text:
College of Agriculture and Life Sciences
Map of Arizona. Source: Arizona Water Map Poster, 2002, Water Resources Research Center, CALS, University of Arizona. Contact the WRRC to purchase a full size version.
KNOW YOUR WATER A Consumer's Guide to Water Sources, Quality, Regulations and Home Water Treatment Options
J a n i c k F. Artiola, Ph.D., Department of Soil, Water and Environmental Science, University of Arizona. Kathryn L. Farrell-Poe, Ph.D., Department of Agricultural & Biosystems Engineering, University of Arizona. Jacqueline C. Moxley, M.Sc., Water Resources Research Center, University of Arizona.
2004, 2006
College of Agriculture and Life Sciences
We wish to extend our sincere thanks to those who contributed to this booklet. Our reviewers/editors:
Joe Gelt, Water Resources Research Center, University of Arizona Mitch Basefski, Tucson Water Frank Corkhill, Arizona Department of Water Resources Chuck Gerba, Department of Soil, Water and Environmental Science, University of Arizona Sheri Musil, Department of Soil, Water and Environmental Science, University of Arizona Mary Black, Center for Sustainability of Semi-Arid Hydrology and Riparian Areas, University of Arizona
Commentary also provided by:
Sharon Hoelscher Day, Maricopa County Cooperative Extension, University of Arizona Gary Woodard, Center for Sustainability of Semi-Arid Hydrology and Riparian Areas, University of Arizona
Graphic Design Support by:
Robert Casler and Maria-del-Carmen Aranguren of the Educational Communications and Technologies Unit, College of Agriculture and Life Sciences, University of Arizona This publication was made possible through a grant from the University of Arizona, Technology and Research Initiative Fund (TRIF), Water Sustainability Program.
Cover photo: Janick F. Artiola
This booklet is intended for Arizona residents who wish to become familiar with water-related issues in Arizona. Topics include: � � A short review of the history and sources of water in Arizona. An overview of the nature of water, the water cycle, water quality concepts, and a glossary of universal terms, including an overview of common minerals and contaminants found in Arizona water sources. A description of drinking water regulations, including National Primary and Secondary Drinking Water Standards. A detailed discussion of accepted home water treatment technologies and home water treatment selection guidelines, based on water quality and user preferences. Downloadable versions of this booklet can be found on the water sustainability web site www.uawater.arizona.edu/pubs/pubs.html in Adobe Acrobat Reader (PDF) format. A link is also provided to a user-friendly edited version of the Home Water Testing Chapter to help determine appropriate water treatment options for home use.
� �
� 2004, 2006 Arizona Board of Regents
Table of Contents
Introduction...............................................................6 I. History and Sources
History and Sources
1.1 History of Water Use in Arizona ...........................9 1.2 Sources of Water ...............................................15
Properties of Water
2. Properties of Water 2 2.1 Minerals in Water ...............................................23 2.2 Contaminants in Water ......................................27
Water Quality and Regulations
3. Water Quality and Regulations 3 3.1 Major Water Quality Parameters and Secondary Drinking Water Standards ................29 3.2 National Primary Drinking Water Standards .....32 4. Water Treatment
Water Treatment
4.1 4.2 4.3 4.4 4.5 4.6
Home Water Testing .........................................35 Particle and Microfiltration ................................38 Activated Carbon Filter .....................................42 Reverse Osmosis .............................................45 Distillation .........................................................49 Ion exchange - Water Softening .......................52
5. Glossary .............................................................79 6. Appendix
6.1 References .......................................................89 6.2 Website Links ..................................................91 4
Table of Contents
History and Sources
1.3 Domestic Wells ..................................................19 1.4 Bottled Water .....................................................21
Properties of Water Water Quality and Regulations Water Treatment
4.7 Disinfection of Drinking Water ..........................56 4.8 Other Treatments Methods ...............................62 4.9 Scams...............................................................64 4.10 Selecting Water Treatment Devices .................66 4.11 Questions to Ask When Purchasing Water Treatment Equipment .......................................73
Glossary Appendix
6.3 Water Quality Standards Tables .......................95
Our day-to-day existence depends on having access to fresh water. We are accustomed to potable water on demand. However, Arizonans, like other U.S. residents, also use large quantities of fresh water to produce food and goods.
Water Use Facts: Arizonans use about 130 gallons (~500 liters) of potable water per person per day. Each adult drinks about _ gallon (~2 liters) of potable water per day and uses about 1 gallon (~4 liters) for cooking. Thus, most of the water delivered to homes is used for waste disposal (toilets), washing (showers, sinks, and laundry) and irrigation (landscape). In addition, each day in the U.S. about 1,400 gallons (~5300 liters) of fresh water are needed to grow one person's food supply, produce electric power, and support industrial production.
The environment, the water cycle and human activities determine water quality. Modern water treatment and delivery systems allow communities to control the levels of contaminants in water. In Arizona, wells and canals also provide and deliver fresh water to areas naturally water deficient (arid).
Public water systems are highly regulated providers of drinking water. Despite evolving federal water quality standards and public right-to-know laws, sales of bottled water continue to grow. Consumers often cite such issues as health, water quality, and convenience as justifications for using bottled water, even though bottled water is often higher in price than gasoline. Packaged drinking water is perceived to be of higher quality than tap water; however, it may not always be safer than tap water. Today, homeowners have access to a variety of home water treatment systems to help control mineral levels and unwanted contaminants in their tap water. Nearly half of the homes in the U.S. have some type of water treatment device. Mistrust of public water utilities, uncertainty over water quality standards, concerns regarding general health issues and limited understanding about home water treatment systems have all played a role in this increasing demand for home systems. However, choosing a home water system is difficult and complex, and the process is often confounded by incomplete or misleading information about water quality, treatment options, and costs. 6
Private well owners also need to provide safe drinking water for their families and have to make decisions as to how to treat their own water sources in order to meet this need. However, information about their water sources is often limited or difficult to obtain. With all these concerns and choices, consumers should be aware of the water sources in Arizona and be familiar with the quality of their water. Consumers should be aware of what minerals, contaminants, chemicals, organisms, pollutants and pathogens are or may be present in their water sources, and what amounts are or are not acceptable. Consumer decisions on home water treatment options should be based on sound water quality information, accepted drinking water standards, and realistic expectations about the cost and performance of home systems.
We Are Not Alone: Land animals, plants, and other living organisms also need fresh water to thrive. We also know that surface water and groundwater sources are often connected and interdependent. Therefore, groundwater overdraft often diminishes surface water resources with negative impacts to the surrounding environment. Modern wastewater treatment facilities control the amounts of contaminants that we discharge into the environment. But residual pollutants that can adversely affect our environment cannot be completely removed from reclaimed water. Therefore, fresh water cannot be regenerated without huge economic costs. What we do at home, at work and outdoors to support our existence as well as the demands we place on Arizona's limited and diminishing water resources all have a direct influence on our environment. Therefore, we must achieve a sustainable water use that includes the needs of Arizona's unique ecosystem, if we want to preserve it for future generations.
PHOTO: Janick Artiola
Sabino Canyon with flowing water and healthy stand of cottonwood trees, Tucson, AZ.
PHOTO: Janick Artiola
Santa Cruz River with dead cottonwood trees due to excessive groundwater overdraft, Tucson AZ.
1.1 History of Water Use in Arizona
Arizona is an arid state where Water Facts. Tucson averages rainfall is highly variable from about 11 inches of rainfall per year to year and region to region, year, Phoenix 7.5 inches, Yuma ranging from 2 inches per year 3 inches, and Flagstaff 22 inches in the western deserts to about per year. 25 inches per year of rain and snow in the mountainous regions. Precipitation in the region has been measured since 1896. Historic precipitation patterns show a continuum of wet and dry periods over the last century with extended drought in the late 1890's to early 1900's; the late 1940's to the 1950's; and the late 1990's to the present.
History and Sources
Arizona statewide precipitation, 1896-2005, showing extended periods of drought in shaded areas. The horizontal red line shows the state average precipitation of 12.5 inches. Source: CLIMAS (Climate Assessment for the Southwest) University of Arizona.
Early History
The search for an adequate water supply has always been a struggle in the desert southwest. The history of water use in Arizona is best defined as the management of water supplies through both wet and dry periods. There is evidence of human control over water resources that dates back to three thousand years ago. The remains of the world's most extensive gravity-based canal system � constructed by the Hohokam people � can still be seen today along the Gila River, and in the Salt River and Santa Cruz Valleys (see next page). These complex systems provided water for established Hohokam communities and their agricultural production until the Hohokam's mysterious disappearance (around A.D. 1450). 9
History and Sources
A few Indian settlements, dependent on irrigation, continued in Southern Arizona. The Spaniards who arrived in the late 1600s already were familiar with irrigation technology, which they had adopted from the Moorish presence in Spain prior to 1500. Wells were dug, more dams and ditches were constructed, and more land went into agricultural production. At the time, Tucson was the northern edge of the Spanish settlements. Conflict with the Indian population and the Mexican War for Independence slowed down further growth and expansion in the area.
Hohokam canals. Source: Southwest Parks and Monuments Association
Nineteenth and Twentieth Centuries
In 1825, American explorers, trappers and settlers began to come into the territory. Settlers in the Salt River Valley reused the Hohokam canals until major diversion projects began in the early 1900s. A prolonged drought in the late 1800s increased pressure on the U.S. government to develop major water storage projects to provide stable water supplies for economic growth, particularly in agriculture and mining. Major reservoir systems were developed throughout the state on the Salt, Verde, Gila and Agua Fria rivers, in addition to the reservoirs on the Colorado River. By the middle of the twentieth century, almost all natural surface water in Arizona had been developed. 10
History and Sources
Roosevelt Dam, completed in 1911. Source: Central Arizona Project
Further south in the Tucson area, rivers dried up as windmills, steam-powered pumps and deeper wells accelerated groundwater pumping to such an extent that, by the early 1900s, local rivers no longer flowed. Colorado River Compact: During the early 1900s, the seven states of the Colorado Water Facts: The Colorado River Compact water allocations were River Basin negotiated for shares decided at a time of above averof Colorado River water. The age rainfall. Arizona was the last Compact of 1922 divided the state to approve the Compact in Colorado River between the 1944. lower basin states of Arizona, California, and Nevada, and the upper basin states of New Mexico, Wyoming, Colorado and Utah � apportioning 7.5 million acre feet to each basin. Today, in the lower basin, Arizona has rights to 2.8 million acre feet of Colorado River water per year, California is entitled to 4.4 million acre feet per year, and Nevada has an annual allocation of 325,851 acre feet. One acre-foot is the approximate amount used by a family of four in one year. Water demand increased through the 1940s and required stable supplies of water particularly in Tucson which, by now, was entirely dependent on groundwater supplies.
Central Arizona Project (CAP): Construction of the Colorado River Project canal to bring water to southern Arizona started in 1968 and was completed just south of Tucson in 1993. Delivery of Colorado River water was a major initiative to provide water to central Arizona. Originally designated for agriculture, by the time of its completion, the water was needed to augment urban supplies for a growing population more than it was needed for agriculture and industry.
Water Facts: After 22 years of lobbying, the Central Arizona Project (CAP) was approved by the federal government in 1968. It is one of the most significant milestones in Arizona water history.
History and Sources
CAP zig-zag canal. Source CAP
The CAP, estimated to have cost over $4 billion, lifts water 2,900 feet through fourteen pumping plants for delivery up to 334 miles from the Colorado River. Arizona Groundwater Water Facts: In Arizona, the Management Act: Throughout ADWR has established five Acthe last century, groundwater tive Management Areas (AMAs) continued to be withdrawn to manage and balance the availfaster than it was being ability of groundwater resources replenished, which created a until the year 2025. These areas condition called overdraft in the include Phoenix and Tucson growing urban areas. Overdraft (see ADWR website link). causes shortages of supplies, increases costs for drilling wells and pumping water, land subsidence, and reduces water quality. Overdraft also has caused the disappearance of 90% of all riparian habitats in Arizona. In 1980, the Arizona Groundwater Management Act was passed and the Arizona Department of Water Resources (ADWR) was formed. The act and state agency were designed to manage water resources more effectively to ensure supplies for the future. Arizona Environmental Quality Water Facts: The ADEQ proAct: In the 1980s, contamination vides state administration of was found in multiple federal programs and assures groundwater sources. The public state compliance with federal became concerned about possible EPA programs. State programs contamination and its effect on for which federal legislative or quality of life. A number of wells regulatory mandates exist must were shut down in the metromeet minimum EPA standards. Phoenix and Tucson areas. By ADEQ regulates public water systems that have at least 15 1986, the Arizona Department of service connections or serve 25 Environmental Quality (ADEQ) people. was formed under the Arizona Environmental Quality Act to establish a comprehensive groundwater protection program and administer all of Arizona's environmental protection programs.
History and Sources
Safe Drinking Water Act
In 1974, the U.S. Congress passed The Safe Drinking Water Act that sets maximum contaminant level (MCL) standards for drinking water. Amendments to this act have since been passed that have imposed more stringent standards on drinking water quality. An example is the new arsenic rule, which has a significant impact in Arizona as groundwater frequently contains arsenic due to the 13
History and Sources
6 million
5 million
Hoover Dam Glen Canyon Dam
First submersible pump
to Phoenix
CAP water
1st Bureau of Rec. Project
Rooselvelt Dam
4 million
CAP water Copper, silver and gold mining
to Tucson
3 million
Groundwater pumping
Roosevelt Dam
raised 77 feet
Portions of this text have been adapted from Kupel 2003, and from the ADWR and CLIMAS websites (see Section 6.2). Updated 2004
local geologic formations through which the water flows. All water providers have to meet these new standards and the associated cost of the technology needed to reduce the levels of arsenic in their water sources.
First turbine pump
2 million
Arizona statehood
Central Arizona Project
1 million
334,162 499,261
Water Users Assoc. formed
Salt River Valley
Groundwater Management Act
0 1900
1920 1940
2000 2005
Water time line and population growth, 1800-2005. Source: Arizona Water Map Poster, 2002, Water Resources Research Center, CALS, University of Arizona, U.S. Census Bureau.
1.2 Sources of Water
Groundwater is considered a Water Facts: Water covers non-renewable source of fresh about 70% of the world's surwater since pumping exceeds face, and all life forms, including recharge in most aquifers humans, depend on it for their used as sources of fresh water. basic survival. However, about Surface sources of fresh water, 97% of the world's water is in the such as lakes and rivers, are oceans and is considered highconsidered renewable. It is ly saline. Ice located near the generally agreed that the total earth's poles, accounts for about amount of water that circulates 2% of the earth's water. About 0.6% of the world's water is annually from the earth's surface fresh water stored below ground to the atmosphere and back (groundwater), often thousands down to the earth has remained or millions of years ago. The atfairly constant in recent times. mosphere and the soil environTherefore, on average, rivers ment account for about 0.06% of and lakes produce the same the world's water. About 0.01% amount of fresh water now as of the world's water is found in they did 100 years ago. However, lakes, rivers, and streams. the population of the world has increased more than six-fold in the last 100 years, adding demands on fresh water resources.
History and Sources
The Water Cycle
Arizona Water Sources
Much of the growth in arid areas like the southwest United States is sustained by the use of non-renewable groundwater and renewable river-fed reservoirs. Presently, about 41% of Arizona's water needs come from in-state groundwater sources. Arizona also has an under-utilized annual allocation of 2.8 million acres of Colorado River water (see Section 1.1). CAP water accounts for about 15% of the state's water use. In-state surface water sources (Arizona rivers and lakes, excluding the Colorado River) provide about 20% of the state's annual water use and reclaimed water is 3%. Agriculture remains the primary user of water resources in Arizona.
History and Sources
20% 3% 15% 21% 41%
Colorado River CAP In-State Rivers Groundwater
Reclaimed Water
7% 25%
Municipal Industrial Agriculture
Arizona Water Sources and Uses. Source: Arizona Water Map Poster, 2002, Water Resources Research Center, CALS, University of Arizona.
Local Water Sources
Phoenix and its surrounding cities � Chandler, Mesa, Tempe, Glendale, Scottsdale and Peoria � have diverse sources of renewable fresh water. These include several major surface water streams: the Salt, Gila, Verde, and Agua Fria rivers and, more recently, the CAP canal. Dams located on these rivers, which flow from the mountains north and east of Phoenix, form reservoirs that provide a steady supply of renewable water. However, it is unlikely that any of these surface water resources will increase in the near future. Phoenix and its surrounding communities also supplement their water needs by pumping from several large aquifers. But significant portions of the groundwater along the Salt and Gila rivers are high in salinity (> 3000 mg/L Total Dissolved Solids (TDS)). The city of Phoenix, which delivers potable water to 1.3 million persons, reported the use of only 8% groundwater in 2002. Tucson has no surface water (streams) supplies. These sources were quickly depleted during the first part of the twentieth century, mostly by local groundwater pumping. Since then, growth has been sustained by the use of groundwater. It is estimated that about 15% of the water that is pumped out of the local aquifers is replaced annually by natural recharge. Thus, in less than fifty years, groundwater levels have dropped in the Tucson basin (center) by more than 200 feet (~60 meters). No one knows the exact amount of water available in the Tucson basin aquifers. However, we know that once water is removed, most of it is not replenished. Also, water pumping costs and mineral content (TDS) increase with aquifer depth. The recent arrival of CAP water (see Section 1.1) has slowed down the groundwater pumping in the Tucson basin. Although CAP water is a renewable resource of water, its amount is not expected to increase in the near future. Yuma obtains drinking water for its 100,000 residents from the Colorado River. Groundwater, while available, is only used in emergencies. Most of the water drawn from the Colorado River in Yuma is used in agriculture. Flagstaff has diverse but limited sources of water. The primary sources are Lake Mary (located to the southwest) and the inner basin wells and springs (located to the north). However, both sources are fed by snowmelt, which can vary greatly year-to-year. Groundwater is also available but it is deep (1000�2000 feet) and, consequently, expensive to obtain.
History and Sources
Water Reuse
About 40% of water delivered to homes is treated in Water Facts: Reclaimed water wastewater treatment plants is becoming a valuable renewable water resource, accounting and can be used for irrigation for about 3% of total water use in or to recharge aquifers. But, Arizona in 2002. reclaimed water is usually ~1.5 times higher in TDS than the original water source. For example, if the water source has 300 mg/L TDS, the reclaimed water will have about 450 mg/L TDS. Also, wastewater treatments kill or remove most pathogens (see Section 4.7), but do not remove all residual (trace) organic chemicals (see also pollutants). The removal of excess salts and residual organic chemicals would increase the cost of wastewater treatment significantly (see Sections 4.4 and 4.5). Reclaimed water is considered safe for irrigation and recharge. We must continue, though, to monitor its impact in the environment to preserve the quality of natural water resources.
History and Sources
The earth has unlimited amounts of water, but only a very small fraction of the world's water is fresh and renewable. Nonrenewable groundwater resources are being depleted in Arizona and many other parts of the world. Many countries in the world (including the U.S.) are experiencing both internal conflicts and conflicts with neighboring countries brought about by the combined pressures of population growth and limited fresh water resources. In the near future, the wise management and use of local water resources will be critical to growth and to the preservation of our life and the environment.
Portions of this text have been adapted from Leeden et al., 1990; WRRC, 2002; and City of Phoenix Water Services Website, 2003.
Water, water everywhere but only a drop is fresh. (See p.15 Water Facts)
1.3 Domestic Wells
The quality and safety of these Water Facts: There are over drinking water sources are not 93,000 domestic, privately owned tested or regulated by any state or and maintained water wells in federal agency. Therefore, private Arizona that provide groundwater well owners should test their well for drinking, household use, and water quality regularly to ensure irrigation to an estimated 300,000 that it meets safe drinking water Arizonans (5% of the states population). standards. Also, well owners may need to select and maintain reliable home treatment systems (see Section 4.10). If the well is located in a large groundwater source, general well water quality information may be available from neighbors or local water utilities. However, the quality of groundwater is influenced by localized geologic conditions and above-ground, human-related influences such as septic systems. Testing Your Well Water Domestic wells should be tested annually for the presence of coliform bacteria, as an indicator of pathogens. More frequent testing is suggested if visual changes in the water quality are noticed or if unexplained health changes occur. The table below provides a schedule and list of analyses for testing. When water tests positive for pathogens, owners may choose to use shock-chlorination to disinfect the well casing and household plumbing. This may not eliminate the contamination if it is found in the aquifer water itself. In that case, the owner should seek an alternate source of water or install a home water disinfection system (see Section 4.7).
Suggested Water Testing* Schedule
Initial Tests** Hardness, sodium, chloride, fluoride, sulfates, iron, manganese, arsenic, mercury, lead, plus all tests listed below. Annual Tests (at a minimum) Total coliform bacteria, TDS, pH, nitrate. Monthly Visual Inspection Look for and note changes in: Turbidity (cloudiness, particulates) Color, taste, and odor*** Health changes (reoccurring gastrointestinal problems in children and/or guests)****
*See Table 4 (Section 6.3) for a comprehensive list of poor water quality symptoms, tests, and possible causes. **Annual testing may not be needed, as these chemicals usually are naturally occurring and their concentrations do not change over time. ***Consider one or more of the initial tests listed above (see also Section 4.10). ****Annual tests should be performed right away.
History and Sources
History and Sources
When the well produces well water of poor quality, it is important to determine the possible causes or sources of the contamination. Table 4 (Section 6.3) provides a list of water symptoms, recommended tests, and possible causes. If the causes cannot be removed, find an alternate source for home water. Otherwise, carefully consider the installation of a new or modified water treatment system (see Section 4.10) to control color, particulates, TDS, and/or inorganic contaminants such as nitrates and arsenic. Homeowners should not attempt to treat or use as drinking water sources contaminated with industrial chemicals such as solvents, pesticides, and gasoline products at concentrations above National Primary Drinking Water Standards (NPDWS; see Section 6.3). See also Section 4.10 for treatment options. Well owners should visit the following ADWR website for information on well construction standards for Arizona residents. www.water.az.gov/adwr/Content/Publications/files/well_ owners_guide.pdf
PHOTO:James Russell
Old farm house with windmill well.
Portions of this text have been provided by and adapted from the ADWR and USGS websites, and USEPA 1997.
1.4 Bottled Water
There are numerous types and sources of bottled water. ComWater Facts: Annual sales of bottled water in the U.S. now mon bottled waters include exceed 8 billion gallons. mineral water (with more than 250 mg/L TDS), purified water (which has been treated to reduce TDS levels), and sparkling water (which is naturally carbonated), among others. For a more complete list, see the National Sanitation Foundation (NSF) website. Bottled water is regulated as a packaged food product by the Food and Drug Administration (FDA) and state governments. Self-imposed standards on bottled water are also required by members the International Bottled Water Association (IBWA). The U.S. Environmental Protection Agency (USEPA) is not directly involved in the regulation of bottled water. However, if the bottled water suppliers use water from public water systems, these must meet USEPA standards. If private water sources are used, such as springs and wells, bottled water may be filtered, but the levels of minerals and contaminants may vary. Also, water disinfection is usually necessary, and packaging is done according to FDA food guidelines.
History and Sources
Water Quality
Large surveys conducted both Water Facts: Limited regulations in the U.S. and worldwide have and inadequate labeling (see shown that, in general, bottled next page) often make it difficult water is no safer than tap water. to determine the source, exact Concerns about the safety of mineral content, and treatment of bottled water has prompted bottled water. the World Health Organization (WHO) to work on the development of an international code of bottled water quality that would require the disclosure of the source, mineral content, and treatment of all bottled water. One advantage of drinking bottled water is its portability and the fact that, unlike tap water, it requires no residual disinfection during storage or delivery to the consumer (see Section 4.6). Therefore, there is no unpleasant chlorine taste or smell. Bottled water should be consumed quickly, not stored for months, as plastic bottles may degrade over time and contaminate the water with plastic residues.
History and Sources
Bottled water label conforming to USDA requirements and non-U.S. bottled water label (insert).
Portions of this text have been adapted from the NSF, FDA, IBWA, NRDC, and WHO websites (see Section 6.2).
PHOTO: Janick Artiola
2.1 Minerals in Water
Water occurs naturally in three states: liquid, gas (vapor) and solid (ice), and moves between these states. Solid water, particularly the polar ice caps, helps protect the aquatic environment from abrupt changes in temperature. Water vapor is essentially pure water in a gaseous form. Water, in its liquid form, picks up chemicals (both minerals and particulates, some considered contaminants) as a result of seepage into its surrounding soil environment. Returning to its gaseous state as it evaporates, water leaves behind the solid residues it acquired in its liquid state.
How Water and Matter Interact
Figure below shows how Water Facts: Water is often water dissolves common table referred to as the universal solvent salt by separating its sodium because of its dual nature � it can (+) and chloride (-) ions (see both surround and separate other dissolution). Within water's chemical substances inside its liquid state, these ions are kept structure separate by molecules whose task is to balance the positive (+) or the negative (-) properties of each element.
Properties of Water
Representation of water molecules interacting with other chemicals.
Other minerals can dissolve in water in a similar manner but in varying amounts. When liquid water comes into contact with the earth's surface and runs off, it can also carry with it visible solid parts (particulates such as silt, clay, and plant parts) that can remain suspended in water. Gases from the atmosphere and gaseous pollutants can also dissolve and be suspended (as bubbles) in water. For example, carbon dioxide dissolves in water and can lower its pH by forming carbonic acid (see carbonated water, Section 1.4).
Common Minerals Found in Water
Besides table salt, fresh water also contains other common minerals that include gypsum, calcite, and dolomite (the main sources of calcium, magnesium, sulfate) and carbonate ions. These ions, together with potassium and table salt, usually account for about 95% (by weight) of the total dissolved solids (TDS) found in natural water. The amount and proportions of minerals in water affect its taste and can often be used to identify the origin of a water source. The figure on the next page shows the mineral compositions of Tucson groundwater and CAP water. A quick look at the figure shows that CAP water has more dissolved minerals and different proportions of minerals than Tucson groundwater.
Water Facts: minerals composed of sodium and chloride ions have a very high water affinity (solubility) and are quickly washed out of the soil. Thus, most dissolved minerals in seawater are sodium and chloride (table salt). Properties of Water
Trace Elements in Water
Numerous other chemicals found in minerals are also found in water in trace amounts. These include beneficial elements like copper, zinc, and iron (see Section 3.1) and undesirable elements like arsenic, mercury, and radon gas (see Section 3.2). Waters that come into contact with minerals rich in these chemicals may contain elevated and potentially toxic amounts.
Contaminants in Water
Human activities can also contaminate natural waters with excessive levels of minerals or pollutants. These activities include agricultural and industrial release of pollutants; improper disposal of municipal and animal wastes into air, soil, surface, and ground 24
waters; and transportation and recreation on air, land, and water. The types and quantities of contaminants that can be tolerated in public drinking waters are set by the USEPA (see Tables 1 and 2, Section 6.3). These standards are discussed in Section 3.
TDS= 650 mg/l
Properties of Water
TDS= 470 mg/l
TDS= 290 mg/l
MINERAL CONTENT (Cumulative Graph) OF WATER SOURCES
Mineral composition of Tucson groundwater, CAP water, and 50:50 blend.
Total Dissolved Solids (TDS) in Arizona Waters
The mineral compositions of the water sources in Arizona vary depending on their origins. In general, the chemical composition of groundwater sources is more seasonally constant but can vary significantly by location. The quality of surface water sources tends to vary both seasonally and by location. Phoenix and other surrounding cities such as Mesa and Gilbert use multiple surface water sources (including groundwater when necessary) that provide tap water with TDS values that exceed 500 mg/L (on average) and can change more than +250 mg/L through the year. The combined hardness of these water sources is considered hard to very hard (see Table 2, Section 6.3). Tucson groundwater's TDS is, on average, about 290 mg/L, but TDS values can vary by about +100 mg/L depending on the location of various wells in the Tucson basin. CAP water has a higher TDS than Tucson groundwater. Therefore, mineral concentrations in tap water are expected to increase as more CAP water is fed into the 25
system. An estimate of the TDS and mineral composition of a 50:50 blend of Tucson groundwater and CAP water is about 470 mg/L (see figure previous page). The combined hardness of this blend is classified as moderately hard to hard (see Table 2, Section 6.3). Flagstaff, on average, has about 200 mg/L TDS in its diverse (multiple surface and groundwater) sources, although values can change by more than +100 mg/L depending on the source. As in other Arizona cities, the hardness of Flagstaff city water ranges from moderately hard to very hard (see Table 2, Section 6.3). Yuma residents obtain their potable water directly from the Colorado River and it is not desalinized prior to delivery. At that location, the Colorado River has an average TDS of about 800 mg/L that changes about +50 mg/L through the year. This source of water is classified as very hard (see Table 2, Section 6.3).
Properties of Water
2.2 Contaminants in Water
Contaminants are divided into three categories: those of natural origin, those of natural origin but enhanced by human activities and those human-made and introduced into the environment. Common minerals are also the most common contaminants found in waters (see Section 2.1). Water sources also have unwanted but naturally occuring toxic elements like arsenic. When arsenic is found in a drinking water source at concentrations above National Primary Drinking Water Standards (NPDWS), the water is "contaminated" with arsenic (see Section 3.2).
Contamination of Water Sources
Water sources may also become Water Facts: The most common contaminated with high sources of water pollution are concentrations of common rainfall (air pollution), seepage, elements like sodium through run-off from urban and agriculturnatural and human activities. al areas, and discharges of conThis water may not be a threat to taminated water and wastewater the environment, but it is unfit to into the open environment. drink or to use to irrigate crops. In this case, the water is considered contaminated with sodium and other salts, and is called saline. Some saline water sources may be acceptable for livestock or used to irrigate salt-tolerant plants common in Arizona. Human-made contaminants are also commonly referred to as pollutants. These include synthetic organic chemicals such as agricultural pesticides, industrial solvents, fuel additives, plastics and many other chemicals. Unfortunately, many of these chemicals are ubiquitous (present everywhere) in our environment due to their extensive use in modern society (see figure next page). Also, microbial pathogens derived from human and animal waste become pollutants when improperly disposed of and can adversely impact the quality of water resources.
Properties of Water
Setting Limits on Contaminants
Few surface and groundwater sources in the world remain unaffected by contamination. Is all the water in the world "polluted?" The answer is "no" if limits are applied. The NPDWS and the National Secondary Drinking Water Standards (NSDWS) are designed to regulate contaminants in water sources because it is unreasonable to expect to have an unlimited amount of contaminant-free water (see Sections 3.1 and 3.2). Thus, drinking water can contain acceptable (by social consensus) amounts of contaminants. 27
Common Contaminants in Arizona Water Sources
Common water contaminants in water and water sources include TDS (naturally high sodium, chloride, sulfate, and calcium), hardness (natural high calcium) nitrates, total coliform bacteria (animal waste, septic systems, and agriculture), arsenic, radon, lead (naturally occurring), pesticides, gasoline products and solvents (agriculture and leaky tanks). With the exception of TDS, all of these contaminants are regulated in public drinking water supplies by the NPDWS (see Section 3.2).
New Contaminants
Properties of Water
The USEPA is always evaluating so-called emerging contaminants that need to be regulated in our public water systems. These include the perchlorate ion found in rocket fuel and explosives (detected in both the groundwater and surface water of several states, including Colorado River water), new groups of water disinfection byproducts, and new types of endocrine disruptors. Although the USEPA has not yet set or passed any national standards on these newly recognized contaminants, individual states may choose to have additional or stricter drinking water quality guidelines, as is the recent case of perchlorate in the state of California. Emerging water pathogens include a bacterium called Mycobacterium avium.
Sources of water pollution in the environment. Adapted from: Arizona Water Map Poster, 2002, Water Resources Research Center, CALS, University of Arizona.
3.1 Major Water Quality Parameters and National Secondary Drinking Water Standards (NSDWS)
The overall quality of water is Water Facts: National Secondmeasured by several parameters. ary Drinking Water Standards The recommended values of are important to public percepmajor water quality parameters tion that water quality is safe. are given in the USEPA list of They provide guidance to water NSDWS (see Table 1, Section 6.3). utilities on aesthetic (taste and These secondary standards, listed odor), cosmetic (skin and tooth as maximum concentration levels discoloration), and technical (water delivery) effects. (MCLs), are non-enforceable. Thus, public water systems are not required to reduce these chemicals below the EPA-recommended levels. However, water utilities control the levels of these chemicals in the water when needed in order to prevent tap water odor and tasterelated customer complaints. The NSDWS also imply that it is acceptable to have some quantities of contaminants, including minerals in fresh water sources and potable water supplies. Most of the minerals found in fresh water are necessary life-sustaining nutrients and many are found in common vitamin supplements. These include calcium, magnesium, potassium, zinc, copper, iron and others (see Section 2.1). In should be noted, however, that drinking tap water normally does not provide the recommended levels of most of these nutrients. For example, drinking 64 ounces (~2L) of water a day containing 50 mg/L calcium would only provide 1/10th of the adult daily requirement of calcium for adults 19-50 year-old recommended by the National Academy of Sciences.
Water Quality and Regulations
Total Dissolved Solids (TDS)
This measurement combines most dissolved minerals found Water Facts: NSDWS may be in water sources into one value. exceeded in drinking water supAccording to the NSDWS plies. For example, the TDS levdrinking water should not have els in several Arizona cities is more than 500 mg/L of TDS. higher than the recommended 500 mg/L (see Section2.1). Still, potable water that has a higher TDS is not necessarily unhealthy. However, high TDS water may cause deposits and/or staining, and may have a salty taste.
This value measures the active acidity or alkalinity of water. The pH of water is important in controlling pipe corrosion and some taste problems. The recommended pH range is 6.5�8.5.
Water Taste
Note that TDS and pH do not determine the proportions of major minerals found in drinking water sources (see Section 2.1). However, the mineral composition of water may affect its taste. For example, water with a TDS of 500 mg/L composed of table salt would taste slightly salty, have a slippery feel, and be called soft water. Whereas, water with the same TDS value but composed of similar proportions of table salt, gypsum, and calcite would have a more acceptable (less salty) taste and feel less slippery due to its greater water hardness (see Section 2.1). Salty taste can be reduced by limiting the amounts of chloride and sulfate ions in potable water to less than 250 mg/L each.
Water Facts: Both the TDS and the proportions of the major chemical (mineral) constituents determine the taste of water, including its hardness and alkalinity.
Water Quality and Regulations
Organic Matter
Other important water properties, listed as NSDWS, have to be controlled in tap water (these are listed in Table 1, Section 6.3). Water color, odor, and foaming are affected by the presence of natural organic matter substances often found in surface (but less frequently in groundwater) supplies. Most organic matter is routinely removed from water by water utilities with EPA-approved physical and chemical water treatments before home delivery.
Metals and Fluoride
The NSDWS also include recommended levels for aluminum, copper, iron, manganese, fluoride, and zinc. Most of these elements are found in trace quantities (less than 1 mg/L) in fresh waters. However, if not controlled, these elements can impart a metallic taste to water, cause staining, and even be toxic when present in tap water at concentrations above the recommended secondary MCLs (see Table 1, Section 6.3).
Water Quality and Regulations
The Code of Federal Regulations. The EPA NSDWS are published in Title 40 (protection of the Environment), Part 143. The EPA NPDWS (presented in Section 3.2) and their implementation are published in Title 40 (protection of the Environment), Part 141 and Part 142.
3.2 National Primary Drinking Water Standards (NPDWS)
The EPA sets drinking water standards in collaboration with numerous other groups, organizations and persons including scientists, state and local agencies, public water systems and the public. States and Native American Communities facilitate implementation of these standards by means of public water systems. Drinking water standards are always evolving as new scientific information becomes available and new priorities are set about the potential health effects of specific contaminants found in water.
Water Facts: Drinking water regulations and standards are used by public water systems to control the levels of contaminants in potable water delivered to homes.
How Standards are Developed
The USEPA considers many issues and factors to set a standard. These include current scientific data, availability of technologies for the detection and removal of contaminants, the occurrence or extent of contamination of a chemical in the environment, the level of human exposure, potential health effects (risk assessment) and the economic cost of water treatment.
Water Facts: Drinking water quality regulations are becoming more numerous and complex in response to public demands, new testing and treatment technologies, and newly discovered health effects of pollutants. Water Quality and Regulations
Public water systems must comply with NPDWS by providing water that does not exceed the MCL of any listed contaminant to their customers. Also, when water sources are treated by public water utilities, they must use EPA-mandated or EPA-accepted water treatment methods. However, small water systems (of up to 3,300 users) may obtain variances (extra time or exemptions) in order to comply with new standards.
Types of Contaminants
Water Facts: There now are over 90 individual and classes of contaminants regulated in public water supplies by the NPDWS.
Contaminants regulated under the NPDWS include inorganic contaminants (such as arsenic and lead), organic contaminants (such as insecticides, herbicides,
and industrial solvents like tri-chloro ethylene or TCE), water disinfectants (such as chlorine and chloramines), disinfection byproducts (such as chloroform), radiunucleides (such as uranium) and microorganisms (such as Giardia and intestinal viruses). The complete list of these contaminants, including their MCLs, is provided in Table 3, Section 6.3. An up-to-date list of NPDWS can always be found on the EPA website (see Section 6.2).
How NSDWS are Implemented
Water Facts: Recent right-to-
know amendments to the SDWA Water providers must monitor require water providers to dis(test) all of their water sources close the results of their water � both groundwater wells and testing to the public. For examsurface waters (lakes, rivers and ple, Tucson Water has its 2004 canals) � at regular intervals annual water quality report on prescribed by the USEPA and its website. This report provides by state regulatory agencies. a summary list of the regulated This is done at the source, after contaminants detected in Tucson water supplies, as well as conany water treatment, and before centration ranges and MCLs. water is introduced into the delivery system. Additionally, water providers must also check for the possible presence of pathogens (using coliform bacteria tests) and residual disinfection chemicals at points throughout their water distribution system. The mandated number of tests and intervals between tests depend on the water quality parameter, number and types of water sources, size of the distribution system, and number of water users.
Water Quality and Regulations
The Safe Drinking Water Act (SDWA) has enforceable provisions for National Drinking Water Standards (see Section 1.1). States are the primary enforcers of drinking water standards. Usually, water quality standards are enforceable three years after being adopted by the EPA. From that time on, water providers affected by the new standard must test their water at regular intervals, maintain complete records of test results, and be subject to audits by state agencies and the EPA. Providers that do not keep records or that violate drinking water standards are subject to fines of up to $25,000 per day. According to the EPA, violations occur more often in smaller rather than in larger water systems.
Portions of this text have been adapted from USEPA websites EPA1, EPA2, and EPA3 (see Section 6.2).
4.1 Home Water Testing
4.1 Home Water Testing .........................................35 4.2 Particle and Microfiltration ................................38 4.3 Activated Carbon Filter .....................................42 4.4 Reverse Osmosis .............................................45 4.5 Distillation .........................................................49 4.6 Ion exchange - Water Softening .......................52 4.7 Disinfection of Drinking Water ..........................56 4.8 Other Treatments Methods ...............................62 4.9 Scams...............................................................64 4.10 Selecting Water Treatment Devices .................66 4.11 Questions to Ask When Purchasing Water Treatment Equipment .......................................73
Water Treatment
4.1 Home Water Testing
To decide whether a home water treatment device is needed you must first know the quality of your water source and the quality of your tap water. Try to obtain as much water quality information as possible from your local water provider or contact neighbors with wells near your own well.
If Your House is Connected to a Public Water System
If your tap water is colored and/or cloudy, smells, or has an Water Facts: Public water unusual taste, verify that your utilities are required by law to deliver water that meets NPDWS house pipes are not affecting to your house (meter) inlet. your water quality. Note the Public water utilities should also appearance, taste and smell of deliver water with acceptable the water from an outlet located taste and aesthetics. outside the house (as close to the main meter as possible). If the water is similar in quality both outside and inside your house, talk with neighbors, as they may be experiencing similar problems. If this is the case, contact your water provider immediately. Most water quality issues of this nature are temporary and will be resolved by your water provider. If your provider is unable to improve the water quality, you should contact the Arizona Department of Environmental Quality (ADEQ) for further assistance (see Section 6.2). If you still are not satisfied with your water quality, you should request an annual water quality analysis report or obtain it from the appropriate water provider website (again, see links provided in Section 6.2). Verify that your water provider delivers water that meets all EPA standards and guidelines. Using this report, you may choose some water quality parameters that you would like to improve.
Water Treatment
If You Own Your Own Water Source (Well)
First, obtain all available water quality information from the previous owner, neighbors, and local water utilities, then consider further testing (see the Suggested Water Testing table in Section 1.3). If your water source is cloudy, smelly, or has an unacceptable taste, it likely does not conform to NSDWS. Consider testing for all parameters (see Table 1, Section 6.3) and review Water Problems: Symptoms, Tests, and Possible Sources (Table 4, Section 6.3) to determine water problems and possible sources of contamination. Finally, contact the ADEQ for information on possible or known sources of groundwater contamination in your area. 35
Water Testing
Before purchasing or installing a water treatment system, test your water at the tap. Be aware that water testing is not an easy or inexpensive step. Laboratory fees for water quality analysis vary greatly from one parameter to another. In 2004, for example, testing for hardness, TDS, and pH may cost about $50. Testing for lead or nitrate may cost about $25. However, testing for all possible individual pollutants can cost more than $2000 per sample. For a complete list see Section 6.3. If you suspect that your house plumbing may be contaminating your water, test your water at the tap for those contaminants that may be present. Carefully choose the list of contaminants to be tested with the assistance of a qualified water quality expert. See also Table 4, Section 6.3, for a list of water problems and suggested tests, and review the drinking water standards listed in Tables 1-3 of Section 6.3. A good water testing laboratory should provide you with clean containers and clear instructions on how to collect your tap water sample. In order to prevent biased test results, it is essential that you follow the water sample collection, preservation, and shipment instructions carefully. To locate an Arizona state certified laboratory, call the Arizona Department of Health Services (ADHS) Bureau of State Laboratory Services for a list of certified water testing laboratories in Arizona (602-364-0728). Water testing laboratories must comply with state and federal guidelines by using USEPA approved methods of analysis. Guidelines for water testing are regularly published and updated by the EPA and are also listed in the Code of Federal Regulations, Title 40, part 136.
Water Treatment
Laboratory Test Results
Have the tests results explained to you by a qualified analyst or water quality expert. For example, terms such as "BDL" mean that a pollutant could not be detected below a certain value or detection limit. BDL values should be listed in the laboratory report and they should always be lower than the NPDWS and the NSDWS MCLs listed in Tables 3 and 1, Section 6.3. Determine which parameters have values above drinking water standards and which parameter you would like to lower in order to improve water quality. 36
PHOTO: Janick Artiola
Water Treatment
Water testing is serious business: Laboratory analyst at work.
The following sections present details on the applications, principles, and cost of six common methods of home water treatment. They also include a list of common water quality problems, specifically those common in Arizona, discuss water scams and present a list of key questions to ask before investing in a water treatment option. Use this information to make informed decisions about your home water treatment options.
4.2 Particle and Microfiltration
Particle filtration is a process that removes small amounts of suspended particles, ranging in size from sand to clay, from water. It can be used alone or ahead of other water treatment devices. Home filters are not intended to filter large amounts of particles. Instead, sedimentation, or sand filters, are used to filter and remove particles from large volumes of water. Microfiltration may also be used to remove some bacteria and large pathogens, like cysts (Giardia and Chryptosporidium). Note that microfiltration should not be relied on to disinfect water with high concentrations of bacteria and viruses, instead chemical disinfection should be used. Other forms of filtration include ultrafiltration and reverse osmosis (see Sections 4.3 and 4.3). See Filtration Application Guide, next page.
Operation and Construction
Filters (Figure 2) function in two general modes: Surface or screen filters remove the particles at or very near the filter surface. Ceramic filters are porous ceramic cylinders that filter at the surface. They are expensive but long lasting, may be cleaned, and provide precise filtration. Resin-bonded filters look like ceramic filters but are produced by bonding particles with resin rather than heat. Depth filters have a thick filter medium. Particles are retained throughout the thick filter mat and these filters may be used for a wide range of particle sizes. There are several types of depth filters. String-wound filters are easily recognized by the criss-cross pattern of the string (which may be made of cotton or synthetic materials such as polypropylene and nylon). Spun-fiber filters look like a fuzzy fiber tube are usually are constructed from synthetic fibers (such as polypropylene and nylon) or natural fibers (such as cellulose). Pleated-fiber filters are constructed either of individual fibers pressed and bonded together or of a continuous sheet or membrane with very small openings.
Water Treatment
Filter Rating
Particle filters have two types of ratings: Average or nominal particle size implies that a range of particles pass through different sized openings within the filter. Absolute particle size implies that no particle larger than the stated size may pass through the filter.
Cr yptosporidium
Metal Ions
Size range of Water Constituents
Aqueous Salts
Dissolved Organics
Beach Sand
Water Treatment
Par ticle Filtration
Filter Process
Reverse Osmosis
Filtration Guide. Source: modified form Filtration Application Guide, Water Quality Improvement Center.
Filter Selection
Filters are rated by the smallest size particle they will remove, stated in microns. A micron is approximately 0.00004 inches (some common particles sizes are shown in Filter Application Guide, previous page). If no colloidal materials or pathogens are present, the filter with the largest rating size that will work is recommended as it will require less maintenance. If the filter must be very fine, such as for removing pathogens, two filters are often recommended. A depth filter with larger opening might be selected as the first filter and an absolute rated surface filter could be used as the second filter to ensure removal of the organisms.
Water Treatment
Particle filtration process
Filter Cost
Particle filters and microfilters range in price from a few dollars for a small self-contained specialty type to $150 or more for a large ceramic filter system. Replacement cartridges range from a few dollars to $100 or more for ceramic cartridges. Total costs are highly variable depending on requirements and particulate load guidelines that determine the cartridge's service interval. Filter Facts: � Synthetic filters (made out of plastic fibers or resins) are a possible source of chemical contamination in themselves. � Misuse of these devices, including overuse and fast or inadequate flushing, may prevent or reduce filtration of contaminants or may release large amounts of contaminants back into the water (initial flush effect). � Filters should be used regularly. Long idle periods may lead to excessive bacterial growth, early clogging, and the possible release of high concentrations of potentially harmful bacteria when flow is restarted. � Replace filters at manufacturer's prescribed intervals.
Portions of this text are adapted from Powell and Black 1987.
Water Treatment
4.3 Activated Carbon Filter
Activated carbon filtration may be selected to reduce unwanted tastes, odors and organic chemicals (such as disinfection by-products, pesticides and solvents) from drinking water. Activated carbon will also reduce radon gas and residual chlorine. Activated carbon filters will not remove or reduce major inorganic ions (e.g., sodium, calcium, chloride, nitrate and fluoride or metals). However, some carbon filters can reduce lead, copper and mercury. Activated carbon filters will not soften the water or disinfect it. If the water source is cloudy, this type of filter may be used after a particle filter to remove particles that may plug or reduce its efficiency.
Water Facts: An activated carbon filter is used most frequently to reduce the unwanted taste and smell caused by water chlorination.
Principles of Activated Carbon Filtration
Activated carbon filtration makes use of a specially manufactured charcoal material. That substance is composed of porous carbon particles to which most organic contaminants are attracted and held (sorbed) on/in the porous surface. See the figure on the next page (insert). However, organic pollutants have large differences in affinity for activated carbon surfaces. Also, the characteristics of the carbon material (particle and pore size, surface area, surface chemistry, density, and particle hardness), the size of the filter and the flow rate of the water through the filter have a considerable influence on the pollutant removal efficiency of these filters. Usually, smaller carbon particles and slower water flows improve contaminant removal.
Water Treatment
Types of Units
Faucet-attached devices, or point-of-use (POU) devices (see figure next page), may be directly attached to the faucet, or the filter may be placed on the countertop and connected to the faucet with a hose. These units may be equipped with a bypass feature to draw unfiltered water. Units that attach to the faucet are very small in size and offer short contact time, relatively short life, and limited contaminant removal. Despite these limitations, these devices improve water taste and reduce smells when used as directed. Pour-through filters also generally are small and portable. Some work merely with gravity filtration and tend to be slow; others contain a poweroperated pump. These devices also improve water taste and reduce smells when used as directed. Speciality filters are intended to treat water for appliances such as ice makers and water coolers. These also are small units, normally a combination particle and activated carbon filter, installed in the water 42
supply pipe. When service is required, the entire unit is replaced. Line by-pass and stationary filters are very similar. These are usually the largest units and they are connected directly into the house plumbing, requiring the services of a plumber.
Filter Selection
When purchasing an activated carbon filtration device, first consider the quality of the drinking water. An activated carbon unit that will get rid of simple taste and odor problems is quite different from one designed to reduce low or hazardous levels of contaminants below national standards. The best unit for a given situation depends on the amount and type of carbon material contained in the unit, what contaminants it is certified to reduce, initial and replacement cost of filters, frequency of filter change, and operating convenience. Two other important factors to consider are the potential drop in water pressure in the home system after installation of a unit and the daily quantity of treated water supplied by the device.
Activated carbon filter units need to have the carbon changed periodically. For small speciality units, the entire unit is normally replaced. Cartridge filters are the easiest to change. The ease of opening the filter housing and the amount of space required to change the filter should be considered.
The devices commonly available for the home range in price from $30 for POU and pour-through filters to over $800 for point of entry (POE) units (installation not included). Replacement cartridges range in price from $3 to $50 or more. The filter cartridge replacement interval will determine annual maintenance cost.
Water Treatment
Activated carbon filter (point-of-use) and activated carbon material (insert).
PHOTO: Janick Artiola
Carbon Filter Facts: � The carbon cartridge should have rigid sides to maximize contact between the water and the carbon. � Only cold, disinfected water should be used. � A newly installed device should be flushed with water, following the manufacturer's instructions. For pourthrough models, water should flow slowly through the unit to assure adequate contact with the carbon. � Filters should be changed on schedule to avoid contamination breakthrough. � Filter material or cartridge should be replaced if left unused for an extended period of time (two weeks or longer). � Hazardous (above NPDWS) levels of organic chemicals should be treated with properly sized, professionally tested, and properly maintained activated carbon filter devices.
Portions of this text have been adapted from Lemly, Wagenet, and Kneen 1995 and Plowman 1989a.
Water Treatment
4.4 Reverse Osmosis
Reverse osmosis (RO) is becoming a common home Water Facts: RO can treat modtreatment method for erately saline to saline water, recontaminated drinking water. ducing the amounts of common RO, probably best known for minerals, including hardness, by 80�95%. its use in water desalinization projects, can also reduce chemicals associated with unwanted color and taste. It also may reduce pollutants like arsenic, lead and many types of organic chemicals. RO treatment is not effective for the removal of dissolved Water Facts: The removal efgases such as radon, or for some fectiveness (percent of removal) depends on membrane type, pesticides and volatile organic water pressure, and the amount chemicals such as solvents. and properties of each contamiFor example, RO will not nant. effectively remove disinfection by-products like chloroform. Consumers should check with the manufacturer to determine which contaminants are targeted and what percent of the contaminant is removed. RO is recommended for sediment (particle) and pathogens. Pretreatments such as particle filtration (to remove sediments), carbon filtration (to remove volatile organic chemicals), chlorination (to disinfect and prevent microbial growth), pH adjustment or even water softening (to prevent excessive fouling produced by water with excessive hardness) may be necessary for optimum RO functioning.
Water Treatment
Principles of Reverse Osmosis
The simplest home RO system consists of a semi-porous membrane (see figure next page), a storage container for the treated water, and a flow regulator and valve to back-flush the membrane when it becomes clogged (or fouled). Tap water is passed through a membrane that filters out most of the contaminants. Eventually, the pores of the membrane become clogged with minerals and the flow-through of water slows down. To remove these residues, the membrane is back-flushed using tap water, which creates reject water high in salts. This brackish water is automatically discharged into the home drain system. When the membrane flow is restored, tap water can be treated again. The pressure for RO is usually supplied by the line pressure of the water system in the home. RO units installed in private water sources should have sediment and activated carbon pre- or post-filters. 45
Home RO units are often small cylindrical devices approximately 5 inches in diameter and 25 inches long, excluding any pre- or post-filtration devices. It is not practical to treat all water entering a residence with RO since small devices do not produce enough water to meet all household needs. Also, RO water can be very aggressive and should not be circulated through or stored in metal pipes or containers. Often, the unit is placed beneath the kitchen sink to treat water used for cooking and drinking.
Reverse Osmosis Process
untreated water
indicates Ion rejection
R.O. Membrane
indicates Ion gets through ,, = IONS
treated water
Reverse osmosis (RO) process.
Types of Reverse Osmosis Membranes
These membranes are made from organic chemicals like cellulose acetate, cellulose triacetate, aromatic polyamide resins, a mixture of these materials and a variety of other materials. Membrane selection depends primarily on the quality of the water source. Some membranes are intended for use only with chlorinated water, others must have water with no chlorine and still others may be used with either. Note that residual chlorine will quickly damage membranes not rated for chlorinated water. All membranes used in home-size RO units are enclosed in a cartridge and are usually either hollow fiber or spiral-wound. Spiral-wound membranes, more common in home systems, are designed to treat water with high levels of suspended solids. Hollow fiber membranes are easily clogged by hard water, but they require less space and are somewhat easier to maintain than the spiral-wound configuration. 46
Water Treatment
Reverse Osmosis System Selection
Key questions to ask and issues to consider before purchasing an RO system include: How well does the RO unit remove contaminants found in our water supply? Note that removals are given in percent removed of the total present in the source water and that this varies for each contaminant. For example: if tap water has 100 mg/L sodium, a membrane with an 85% reject value should produce water with no more than 15 mg/L of sodium. Again, remember that this removal percentage for sodium may not be the same for other contaminants. How much treated water can be produced per day? Since some RO units operate continuously, an oversized system will result in excessive waste of treated water. How much back-flushing water is needed per gallon of treated water? This often is an overlooked cost that may be difficult to determine in home systems that drain the back-flush water directly into the sewer. Home RO systems may spend as much as 10 gallons of water to back-flush the membrane for every gallon of clean water they produce. In contrast, industrial RO units may need only 3 gallons of back-flush water for every 7 gallons of treated water. For home RO systems, the range of water treatment efficiency may vary from ~10-50%, depending on the TDS and hardness of your water source, membrane type, removal efficiency and system pressure.
Operation and Maintenance
Water Treatment
RO units increase home water use since tap water must be used to regularly flush the membranes. Some devices might require continuous operation to maintain peak membrane performance. This may lead to frequent and excessive losses of treated water. Clogged or torn RO membranes require replacement; however, well-maintained membranes should last two to three years. In addition, an RO system that uses pre-and post-treatment devices has added purchase and maintenance costs. Membrane inspection is not practical, so regular analysis of the treated water � using a TDS meter or more specific and expensive contaminant testing methods � is necessary. Also, some beneficial minerals � such as calcium and magnesium � are reduced significantly in RO water. As drinking water is not the primary source of these nutrients in our diet, this can be of minimal importance. 47
RO devices available for the home range in price from $200�$500, not including installation. Maintenance costs can range from $50�$120 a year.
RO Facts: Since extra tap water is needed to regenerate membranes, large home RO systems may result in significant increases in water use and fees. For example, a 10 gallon-a-day RO system with a 20% efficiency rating will require 1500 gallons of extra water use each month. Additionally, if water softening is needed prior to RO treatment, those costs also should be considered. However, these extra monetary and environmental costs are often overlooked.
Water Treatment
4.5 Distillation
Distillation effectively removes Water Facts: Converting water inorganic contaminants to steam and back to liquid. ef(suspended matter including fectively purifies and sterilizers minerals, metals, and water. It's the oldest and most particulates) from water. Since natural form of water treatment. distilled water has no minerals, some people claim distilled water tastes flat or slightly sweet. Distillation also kills or removes microorganisms, including most pathogens. Distillation can also remove organic contaminants, but its efficiency depends on the chemical characteristics of the contaminant. Volatile organic chemicals (VOCs) like benzene and TCE vaporize along with the water and re-contaminate the distilled water if not removed prior to distillation. Some distillation units may initially purge some steam and volatile chemicals. These units should be properly vented to prevent indoor air contamination. Some home distillation units have activated carbon filters to remove VOCs during distillation.
Principles of Distillation
The principle for operation of a distiller is simple. Water is heated to boiling in an enclosed container. As the water evaporates, inorganic chemicals, large non-volatile organic chemicals, and microorganisms are left behind or killed off in the boiling chamber. The steam then enters condensing coils or a chamber where the steam is cooled by air or water and condenses back to a liquid. The distilled water then goes into a storage container, usually 1.5�3 gallons in capacity. See (figure next page).
Distillation Units
Also called stills, distillation units generally consist of a boiling chamber (where the water enters, is heated, and vaporized), condensing coils or chamber (where the water is cooled and converted back to liquid), and a storage tank for treated water. Distillation units are usually installed as point-of-use (POU) systems that are placed near the kitchen faucet and used to purify water for drinking and cooking only. Home stills can be located on the counter or floor, or attached to the wall, depending on size. Models can be manual, partially automated, or fully automated.
Water Treatment
Cooling or Condensing Chamber
Vent for Volatile Gases
Distilled High Quality Drinking Water
Tap Water Minerals Boiling Chamber Heat Collection Tank
Figure 1. Distillation process
Operation and Maintenance
As with all home water treatment systems, distillation units require some level of regular maintenance to keep the unit operating properly. Contaminants left in the boiling chamber need to be regularly flushed out. Even with regular removal of the brackish (saline) residues, calcium and magnesium scale will quickly collect at the bottom of the boiling chamber. Over time, this scale reduces heat transfer and should regularly be removed either by hand scrubbing or by soaking with acetic acid. Vinegar is a common cleaner used in home distillers.
Water Treatment
Small still units (capacity: 1.5 gallons, 6 liters) cost $250 or more. Large units (capacity: 15 gallons, 57 liters) vary from $450 to $1,450 in purchase price.
Distillation Facts: � Distillation is the most effective, but also the most expensive (energy intensive) form of water purification. � � The power rating of the still and the local electricity rates determine the cost of operating these units. To calculate the cost to produce one gallon of water, multiply the price of a kilowatt hour times the rated kilowatt hour use of your model times the number of hours it takes to produce one gallon of water. For example, if local electricity costs 0.10 cents per kilo watt hour and your unit is rated at 800 watts (or 0.8 kilowatt hour) and it takes 4 hours to produce one gallon of water, your operating cost is 0.32 cents per gallon, excluding purchase and maintenance costs. Distillation efficiency decreases as the TDS of the water increases. Distillers can effectively reduce most or all contaminants, including minerals, metals, organic chemicals, and microorganisms from water. Although minerals that can cause corrosion and scaling are reduced during distillation, distilled (and RO) water is very corrosive and should not be stored or transferred in metal pipes. Distillers vary from small, round units that distill less than one quart of water per hour to rectangular carts that distill about one-half gallon of water per hour.
Water Treatment
� �
Portions of this text have been adapted from Plowman 1989b.
4.6 Ion Exchange - Water Softening
Ion exchange units that replace calcium and magnesium ions from water are known as water softeners. They may also remove varying amounts of other inorganic pollutants such as metals, but they will not remove organic chemicals, pathogens, particles, or radon gas. Water softener units work most efficiently with particulate-free water.
Water Facts: Home water softeners are popular in Arizona because they reduce water hardness associated with calcium and magnesium minerals.
Principles of Ion Exchange to Soften Water
Calcium and magnesium ions are atoms that have a positive electrical charge, as do sodium and potassium ions. Ions of the same charge can be exchanged. In the ion exchange process, a granular substance (usually a resin) that is coated with sodium or potassium ions comes into contact with water containing calcium and magnesium ions. Two positively charged sodium or potassium ions are exchanged (released into the water) for every calcium or magnesium ion that is held by the resin. This "exchange or trade" happens because sodium or potassium are loosely held by the resin. In this way, calcium and magnesium ions responsible for hardness are removed from the water, held by the resin, and replaced by sodium or potassium ions in the water. This process makes water "soft." Eventually, a point is reached when very few sodium or potassium ions remain on the resin, thus no more calcium or magnesium ions can be removed from the incoming water. The resin at this point is said to be "exhausted" or "spent," and must be "recharged" or "regenerated."
Water Treatment
Ion Exchange Unit Components
A water softener can be as simple as a tank to hold the exchange resin, together with appropriate piping for raw (inlet) and treated (outlet) water. Modern water softeners include a separate tank for the brine solutions used to regenerate the resin, additional valves to back-wash the resin, and switches for automatic operation.
Plumbing Requirements
New homes are plumbed to accomodate water softeners. Plumbing old homes for soft water can be very expensive. Not all the water coming into a home needs treatment. If the water is classified as very hard (10.5 or more grains per gallon or 180 or more mg/L of 52
Water Softening Process (ION Exchange)
untreated water
= Calcium or Magnesium Ions
Resin bead
= Sodium or Potassium Ions
treated water
Ion exchange process
Water Treatment
calcium carbonate), a house point of entry (POE) treatment may be needed. Otherwise, only the hot water supply should be treated to reduce formation of calcium deposits (scale) in the water heater and pipes. Personal preference may also influence the decision to treat hot and cold supplies going to the laundry room, showers, and sinks. Toilets and outdoor faucets should not receive softened water. Softened and untreated water may also be "blended" to produce water with a lower hardness and to decrease the amount of water that must be
Unit Selection
The selection of a water softening unit depends on the hardness of the raw water and the amount of water to be softened. There are manual, automatic, semiautomatic, and fully automatic units that differ in the degree of resin regeneration automation. First, the number of fixtures in the home that will require softened water must be determined. Then, all the fixtures flow rates need to be added up. Note that conventional faucets use 3-5 gallons per minute (gpm) and conventional showers use 5-10 gpm. (Newer, watersaving fixtures may use only half these amounts).
Operation and Maintenance
Maintenance of water softeners is largely confined to restocking the salt supply for the brine solution. Semiautomatic models require either a manual start of the regeneration cycle or regular service for a fee. The resin should never wear out but if resins are not regenerated on a regular basis, at the proper intervals, they may become contaminated with slime or impurities and require replacement. Resins can also become clogged with tiny particles of iron if the raw water contains that mineral. Back-washing, that is, reversing the normal flow of water through the treatment unit, may be required to remove the iron. Alternately, special additives may be added to the brine to help minimize this condition.
The initial cost of water softeners depends on the total hardness of the water, the degree of desired automation, the volume of water to be treated, and other design factors. Retail prices range from approximately $300 for a one-tank system capable of removing 12,000 grains before recharging, to more than $1000 for a two-tank system capable of removing 48,000 grains before recharging. Operating costs depend on the frequency of resin regeneration. Only salt made specifically for ion exchange units should be used. This salt costs about $3.50 for a 40-pound bag. Electrical costs should be considered as part of operating expense for ion exchange units. Seek units that are energy efficient as expressed by their Energy Efficiency Rating (EER).
Water Treatment
Water Softener Facts: � An often overlooked environmental cost of water softening systems is that they degrade the quality of reclaimed and gray water by increasing water salinity (TDS). Remember, most of the additional sodium or potassium that is used in water softeners and the brackish water produced during resin regeneration is discharged into the sewage or gray water systems and, eventually, into the environment. House and yard plants should not be irrigated with soft water. This is due to its disproportionate ratio of sodium or potassium to calcium and magnesium ions. In general, water with a high sodium/calcium ratio has an adverse effect on soils, and plants are more stressed because soft water has a higher salinity and may lack calcium and magnesium (necessary plant nutrients). Soft water may not be as healthy to drink as hard water for persons that are on a low sodium diet. The taste of soft water may not be as pleasant as hard water.
� �
Water Treatment
4.7 Disinfection of Drinking Water
Drinking water should be free of pathogens that cause illnesses such as typhoid fever, dysentery, cholera, and gastroenteritis. Whether or not a person contracts these diseases from water depends on the type of pathogen, the number of organisms in the water, the strength of the organism (its virulence), the volume of water ingested, and the susceptibility of the individual. The purification of drinking water that contains pathogens requires a specific treatment called disinfection. Disinfection does not produce sterile water but it does lower the concentrations of pathogens to acceptable levels. Also, disinfected water is quickly contaminated with many types of benign heterotrophic bacteria that are ubiquitous (present everywhere) in the environment. These benign bacteria are regulated and listed in the NPDWS as Heterotrophic Plate Count HPC (see Table 3, Section 6.3).
Disinfection Requirements
Disinfection reduces pathogens in water to levels designated Water Facts: State and federal safe by public health standards. governments require public waThis prevents the transmission ter systems to deliver water to of diseases. Ideally, an effective homes with no harmful levels of disinfection system should kill pathogens. or inactivate (render harmless) all pathogens in the water. It should be automatic, simple to maintain, safe, and inexpensive. Water Facts: Private water The ideal system should treat all sources, including wells, are vulthe water and provide residual nerable to contamination from (long-term) disinfection. septic fields, improper well conChemicals should be safe and struction, and poor quality water easy to store and not make sources. the water unpalatable. Thus, water supply operators must disinfect and, if necessary, filter the water to remove Giardia lamblia, Legionella, coliform bacteria, viruses and turbidity to meet USEPA mandated levels. More than 30 million people in the United States rely on private wells for drinking water, and in Arizona there are over 93,000 wells (see Section 1.3).
Water Treatment
Chlorine Treatment
Chlorine readily reacts with Water Facts: Although several many contaminants found in disinfection methods can control water and, in particular, with pathogens in water, chlorination natural organic matter (NOM), is the most common method of microorganisms, and plant disinfection of public water sysmatter. These include natural tems. (see figure below). Chloorganic chemicals associated rination is very effective against with taste and odor. There many pathogenic bacteria; howare many types of chemical ever, at normal dosage rates, it reactions between chlorine and does not kill all viruses, cysts, or worms. water contaminants that raise the amount of chlorine needed to disinfect water (chlorine demand). Additional chlorine may be added to provide continuous disinfection (residual). An ideal water disinfection system provides residual chlorine at a concentration of 0.3-0.5 mg/L. DPD (diethyl phenylene diamine) is a common water color test used to measure chlorine breakpoint and residual levels. Good test kits must measure free chlorine, not total chlorine, in drinking water.
Water Treatment
Typhoid fever deaths since the beginning of water chlorination in the US. Source: US Centers for Disease Control and Prevention, Summary of Notifiable Diseases, 1997.
Water Chlorination Facts: � Add sufficient chlorine to the water to meet the chlorine demand and provide residual disinfection so that water remains safe during storage and/or delivery. � Disinfection using chlorine chemicals can produce unwanted volatile organic chemicals called disinfection by-products. The formation of these pollutants during chlorine disinfection is tied to the presence of NOM, type of chlorine treatment, and other water quality variables. The levels of disinfection by-products in public water supplies are regulated under the NPDWS (see Table 3, Section 6.3). The contact time necessary to disinfect water varies with chlorine concentration, the type of pathogens present, pH, alkalinity, and temperature of the water. Complete mixing of chlorine solution and water is necessary and a holding tank is often needed to achieve appropriate contact time.
Chlorination Guidelines �
Water Treatment
Maintain a free chlorine residual of 0.3 0.5 mg/L after a 10-minute contact time. Measure the residual frequently. Once the chlorine dosage is increased to meet greater demand, do not decrease it. Locate and eliminate the source of contamination to avoid continuous chlorination. If a water source is available that does not require disinfection, use it. Keep records of pertinent information concerning the chlorination system.
Caution: Do not store chlorine-free water in containers or trapped in water lines for long periods of time as bacteria will grow in it.
Chemicals for Home Chlorination Facts: � Household bleach is a common form of liquid chlorine; available chlorine ranges from 5.25% (domestic laundry bleach) to 18% (commercial laundry bleach). Liquid chlorine solutions are unstable and only maintain their strength for about one week. Protect such solutions from sun, air, and heat. Chlorine powder chemicals must be dissolved in water. These solutions have an available chlorine content of about 4% and require filtration. Chlorine powder forms are stable when stored properly, but are a fire hazard if stored near flammable materials.
Types of Chlorine Used in Disinfection
Public water systems use chlorine in gaseous forms, which are considered too dangerous and expensive for home use. Private systems use liquid chlorine (sodium hypochlorite) or dry forms of chlorine (calcium hypochlorite). To avoid hardness deposits on equipment, manufacturers recommend using soft, distilled, or demineralized water when making up chlorine solutions.
Equipment for Continuous Chlorination
Continuous chlorination of a private water supply can be done by various methods: chlorine pump, suction device, aspirator, solid feed unit, and batch disinfection. The injection device should operate only when water is being pumped, and the water pump should shut off if the chlorinator fails or if the chlorine supply is depleted. Consult with a professional on equipment selection and tank requirements. For example, in a private well system, the minimum-size holding tank is determined by multiplying the capacity of the pump by a factor of 10. Thus, a 5 gallon-per-minute (gpm) pump requires a 50 gallon holding tank. Other methods to control contact time include the use of pressure tanks and coils.
Water Treatment
Ultraviolet Radiation (UV)
This method uses a UV lamp (source) enclosed in a transparent protective hollow sleeve through which water flows. RNA/DNAdamaging UV light is absorbed by bacteria and viruses, making them inactive and unable to reproduce. Class A UV systems are 59
more effective at reducing pathogens than Class B units. Class B UV systems may be used at home to reduce the levels of heterotrophic bacteria present in tap water, although this many not necessarily make tap water safer. However, UV systems may provide an extra level of protection against pathogenic bacteria and protozoa. In summary, home UV Class B treatment systems are well suited to treat clean tap water with only residual levels of bacteria. Industrial grade UV Class A treatment units may also be used to kill or inactivate viruses, yeast, mold spores, and algae. UV systems are simple and relatively maintenance free. However, their efficiency depends on several things: the design and energy of the UV chamber and source, the flow rate of the water, the amounts and types bacteria and other microorganisms present, and the clarity of the water. No chemicals are needed with this method of disinfection. But UV treatment provides no residual disinfection and it is not effective with cloudy or turbid water.
UV Systems Maintenance and Costs
UV lamp must be replaced annually (having a 9 month to 1 year lifetime). The cost is approximately $80. A UV sensor is recommended to determine the UV dose needed to kill bacteria. The cost of a home UV disinfection system starts at around $500.
Other Disinfection Methods
Although chlorination is the method of choice for most municipal and private water treatment systems, alternatives do exist (see box).
Water Treatment
Emergency Disinfection 4
The use of household chemicals (such as bleach or iodine) to disinfect water without the appropriate equipment or technical supervision should only be considered under emergency situations. For a list of these chemicals and their safe use, see the EPA website: www.epa.gov/OGWDW/faq/emerg.html (for other EPA links, see Section 6.2).
Other Disinfection Methods Ozonation � ozone is a more powerful disinfectant than chlorine � � � � its disadvantage is that it cannot be purchased but must be generated on-site the machinery to generate ozone is complicated and difficult to maintain the effects of ozonation chemical by-products are not fully understood like UV radiation, ozone treatment does not provide residual disinfection. two minutes of vigorous boiling ensures biological safety boiling kills all organisms in water (whereas chlorination reduces them to safe levels) boiling is practical only as an emergency measure once boiled, cooled water must be protected from recontamination pasteurization uses heat to disinfect but not boil water flash pasteurization uses high temperature for short time (160� F, 15 seconds) low-temperature pasteurization uses lower temperature for longer time (140� F, 10 minutes)
Water Treatment
Boiling � � � �
Pasteurization � � �
Portions of this text have been adapted from EPA7, and Wagenet and Lemley 1988.
4.8 Other Treatment Methods
Bacteriostatic filters are activated carbon filters that also contain silver particles to help control bacterial growth inside the filter. However, their effectiveness is controversial. Silver may help contain, but not necessarily reduce, bacterial growth in activated carbon filters. The National Sanitation Foundation (NSF) lists and certifies some filter devices (and manufacturers) with "bacteriostatic effects." However, their efficiency at controlling bacteria in tap water is not stated. KDF (redox) filters are a new type of home water filtration device that may work as intended to reduce already low levels of bacteria, chlorine, some metals, and some types of organic pollutants from water. The effectiveness of this type of filter is also controversial. The NSF lists KDF filter media in its website. These filters should not be used for any other reason than to (possibly) improve water aesthetics (control taste, odors, or residual chlorine).
Ion Exchange Applied to the Removal of Other Ions
Organic resins can also be used to remove from water any type of ion besides calcium and magnesium (see Section 4.6). Ion exchange resins are commonly used as POU treatment devices to produce ultra pure (near completely demineralized) water in commercial and industrial laboratories. Usually, a water source with a very low TDS (less than 5 mg/L) is used. This usually requires pretreatment of the water source using a RO system. Typically, a series of mixed bed [anionic (-) and cationic(+)] resins followed by activated carbon filtration (packed in cartridges) are used to "polish" the water to strict purity standards. However this approach is not practical, costeffective, or even necessary for home water treatment.
Water Treatment
Ion Exchange Facts: � Mixed-bed resins are quickly exhausted when tap water is used because ions like sodium, calcium, chloride, and sulfate (among others) quicky overwhelm and saturate the resin sites. Unlike water-softening resins, mixed-bed resins cannot be regenerated at home and must be purchased new when exhausted, or regenerated commercially. The cost of each cartridge starts at over $100 and varies upward depending on size. The efficiency of removal of trace levels of pollutants like cadmium, chromium, lead and many other metal ions varies greatly and depends mostly on the TDS of the water source. The higher the TDS, the lower the efficiency of removal. To maintain strict water quality, commercial laboratories regularly test the purity of their water source with sophisticated instruments.
Water Treatment
Laboratory grade water deionizer system that uses four mixed-bed resins, and activated carbon and particle filters.
PHOTO: Janick Artiola
4.9 Water Scams
Consumers may become victims of several types of water scams related to water testing, water treatment, bottled water, and health issues (quackery). Consumers can decrease their chance of becoming victims by staying well informed. Water Facts: To avoid water scams � � � � � � evaluate any claim carefully (remember, if it seems too good to be true, it probably is). consider only widely accepted and scientifically proven methods of water treatment. avoid pseudo-scientific (unproven) methods. be skeptical of testimonials from "satisfied" customers. avoid impulse buying or pressure buying tactics. report scams to local authorities and to the office of the Arizona State Attorney General.
Water Testing Scams
These can best be avoided by having your water tested by an independent laboratory (Arizona certified) that uses state-of-the-art USEPA-approved methods (for web links, see Section 6.2). Avoid "free" home water tests. Sellers may claim that they are using "EPAregistered" methods to test your water. This only means that they have registered their test with the USEPA; it does not mean that the USEPA has approved their test. It is very easy to make the color of water change with the addition of a drop of some chemical. Color changes do not necessarily mean that your water has a particular pollutant or excessive levels of pollutants.
Water Treatment
Water Treatment Scams
These can be relatively benign, for example, being sold a treatment device you do not need. They also can be "fraudulent" when consumers are sold a device that does not work as claimed. There are several devices that claim to control or eliminate scale formation and/or remove minerals from water. These include magnets (magnetic or electromagnetic), electronic devices, depressurizing devices, catalytic, oscillation, vibration, and light devices (other than 64
ultraviolet; for a discussion of ultraviolet radiation, see Section 4.7). There is no scientific evidence that any of these devices reduce or remove salts, prevent scale formation, or perform any other type of useful home water treatment. Again, consumers may encounter home water treatment systems that claim to be "EPA-registered." As with water testing, this does not mean that their system has been tested, approved, or endorsed for home use by the USEPA. The NSF certifies all water treatment technologies for the reduction of specific contaminants (including those previously discussed in this section), and it maintains a list of manufacturers that have tested and registered their home treatment devices with this organization (see Section 6.2).
Bottled Water Scams
These may be benign in nature, but they also can be costly over time (see discussion in Section 1.4). A notable scam claims that oxygenated or super-oxygenated water will provide all sorts of benefits from adding extra oxygen to your blood, changing the structure of water, "hydrating" you faster to "retarding" aging. Other bottled water scams may claim that "magnetized" or "ionized" water from remote glaciers or springs has numerous healing properties. None of these claims has any scientific evidence (visit the NSF website for descriptions of bottled water).
Portions of this text have been adapted from Hairston et al., 2003.
Water Treatment
Glass of water with a twist of magnetism?
PHOTO: Janick Artiola
4.10 Selecting Water Treatment Devices
Water Facts: When considering home water treatment, inform yourself and consult with water treatment professionals at reputable dealership(s) to determine the best treatment approach for your particular problem(s).
There are several types of water problems than can occur in water supplies. A complete listing of water problems, including, water appearance, water tests and possible sources of contamination can be found in Table 4 of Section 6.3.
There are two primary categories of home water treatment devices: point of entry (POE) and point of use (POU). The effectiveness of these devices will vary depending on the quality of the water source and consumer need. If more than one water quality problem exists, choosing a treatment device can be especially confusing and complicated. Well owners, for example, sometimes can eliminate two problems with one treatment. Occasionally, one treatment can create another problem. For example, it may be impractical to install a distiller to remove lead from your drinking water if your water is corrosive and continues to remove lead from the household piping system. Similarly, a reverse osmosis unit will not work efficiently if the water also contains particulates or if the water is very hard, as these can clog the membrane filter. The following guidelines for water treatment are based on the fact that it is practical and efficient to treat some water quality problems before others. For instance, turbidity, acidity, hardness, and iron have to be controlled before activated carbon filters, reverse osmosis, or distillation units will operate efficiently. See also the table at the end of this section for a summary of water treatment options presented below.
Water Treatment
Treatment Options for Users of Public Water Supplies
Common Arizona Water Quality Issues � Hardness: symptoms include excessive scale deposits and stains in showers, toilet bowls, and faucet ends; early appliance failures; and poor swamp cooler performance. Excessive hard water may be controlled using a water softener. The treatment device can be either POE or POU. Note: New homes are often plumbed to provide soft water to the kitchen and laundry room.
Salinity/high TDS: symptoms include excessive staining in showers and aluminum cookware, and houseplants that are stunted or have burned leaf tips. Excessive salinity in water may be reduced or eliminated by using either a reverse osmosis or a distillation unit. The treatment device should be POU. Note: High salinity is often associated with high alkalinity and hardness. Taste and smell: symptoms include a chlorine-like taste and smell, and earthy or musty smells due to the presence of residual chlorine and disinfection by-products. Odorous chemicals produced by soil bacteria can be controlled with an activated charcoal filter. The treatment device should be POU. Arsenic, nitrate, lead and other inorganic pollutants: the levels of these pollutants may be further reduced using reverse osmosis or distillation systems. Treatment devices should be POU. Volatile organic chemicals, including disinfection byproducts, certain pesticides, and gasoline products: symptoms include a chlorine-like smell and taste. Use an activated carbon filter to reduce these smells. The treatment device should be POU. Note: While the smell of disinfection-related chemicals is common, the presence of other smells in your tap water should be reported immediately to your water provider. Radon gas: this gas is colorless and odorless, and its levels in tap water are regulated and controlled by water providers with aeration. Some activated carbon filters have been found to reduce further radon in tap water. The treatment device should be POU.
Water Treatment
4 Treatment Options for Users of Private Water Supplies
Treatments Listed in Order of Priority � Turbidity: symptoms include cloudiness (a yellow, brownish, or black cast) that clears after standing for 24 hours. Turbidity is due to the presence of sediments (including fine sand, silt, and clay particles) as well as insoluble iron and manganese particles. To treat, use flocculation and sedimentation or particle and micro filtration. Your choice will depend of the volume of water to 67
Water Treatment
Point of Use (POU)
Faucet Mount In-Line Line-Bypass
Water Heater
Laundry Room
Outside Use
Water Meter
Direct Use
Point of Entry (POE)
Hot Water
= Valve = Treated Water
Home Water Treatment Installations
Home water treatment installlation options.
be treated and the amount of materials present. Note: Surface water sources are usually contaminated with cystic pathogens. This makes sedimentation or particle filtration a necessary first step. � Hydrogen sulfide and soluble iron and manganese: symptoms include a rotten egg odor and the evident presence of stain-causing chemicals. Also, after standing for 24 hours, brownish/black sediments are observed at the bottom of a glass. This suggests an acidic, oxygenstarved water source. To remove these chemicals, water must be oxidized using aeration, chlorination, and/or an oxidizing filter, followed by particle sedimentation or filtration. Water sources rich in these chemicals tend have high acidity (low pH) upon treatment. They may also require acidity control (see below). Treatment devices should be POE. Color-high natural organic matter (NOM): symptoms include a transparent yellowish-brown tone that does not clear after standing for 24 hours. Normally associated with surface water sources, it indicates the presence of high levels of dissolved NOM. Small concentrations and water volumes can be controlled with activated carbon filtration. Chlorination may also destroy NOM and should be followed by activated carbon filtration to remove residual disinfection by-products. Flocculation is used by water utilities to removed NOM from water sources. Acidity: symptoms include green stains, pH levels below 6.0, and metallic taste (high copper and zinc content). It may be treated using acid neutralizing filters or by the addition (feeding) of alkaline chemicals such as lime. Treatment devices should be POE. Alkalinity: symptoms include high measured value, high pH (more than 8.4), and high sodium. This may be reduced with the addition of acid chemicals. Reverse osmosis or distillation systems also may be used to reduce or eliminate water alkalinity. If alkalinity is associated with excessive scale formation, the treatment device should be POE. Note: Water softeners will not reduce alkalinity. Corrosion: symptoms include blackened or tarnished metal utensils and pipes due to high chloride and sulfate levels and/or to high water acidity and hydrogen sulfide. This problem must be controlled with POE devices (see above for treatments that lower salinity). 69
Water Treatment
Pathogens: symptoms include mild to severe gastrointestinal problems including diarrhea and vomiting. Once particles have been removed (see turbidity above), chlorination, UV radiation, or ozonation may be used to disinfect your water source. Storage and transfer of water will require residual chlorination not provided with UV radiation or ozonation treatments. Residual chlorination is necessary to store or transfer drinking water in potentially contaminated places like water pipes and large water storage tanks. Chemicals used to disinfect water may be added in excess to maintain residual chlorine levels. Chloramine chemicals may also be added after chlorination is completed in order to maintain acceptable chlorine residual levels. Disinfection should be done with POE devices. Hardness: see above. Salinity: see above. Volatile organic chemicals, including disinfection byproducts, certain pesticides, and gasoline products: see above. Radon gas: see above. Arsenic, nitrate, lead and other inorganic pollutants: see above.
� � �
� �
Water Treatment
Water Problems: Symptoms, Tests, and Possible Sources
(* indicates a common Arizona water quality issue)
Symptom Visual (Water appearance) Cloudiness of water with a yellow, brown or black cast that clears after standing 24 hours Transparent yellow-brown tint to water that doesn't clear after standing 24 hours
Cause *Turbidity
Treatment devices Flocculation and sedimentation or particle and microfiltration (POE)
*High levels of natural organic matter (NOM), usually in surface water Presence of dissolved iron and iron bacteria
Activated carbon filtration or chlorination followed by activated carbon filtration Water utilities use flocculation to remove NOM. Low amounts: reduce with particle filter or during reverse osmosis or distillation treatments (POE or POU) High amounts: remove by potassium permanganate-regenerated oxidizing filter and particle filter (POE) Very high amounts: remove by chlorination followed by particle filter (POE) Consider well and distribution/storage shock chlorination to kill iron bacteria. Particle filter (POE)
Brown-orange stains or reddish slime or tint to water
Brownish color or rusty sediment Visual (Staining and deposits) Blackened or tarnished metal utensils and pipes Blackened or tarnished metal utensils and pipes Stains in showers, toilet bowls, and faucet ends Excessive staining in showers and aluminum cookware Green water stains Soap deposits or excessive scaly deposits in plumbing and appliances Excessive salt deposits
Suspended iron and manganese particles High chloride and sulfate levels High water acidity and high hydrogen sulfide *Hardness *Salinity
Reverse osmosis unit (POE) or distillation unit (POU) Acid-neutralizing filters (calcite or calcite/ magnesium oxide) (POE) or addition of alkaline chemicals such as lime Water softener (POE or POU) Reverse osmosis unit or distillation unit (POU) Acid neutralizing filters (POE) or addition of alkaline chemicals such as lime Water softener or reverse osmosis or distillation (POE or POU) Reverse osmosis or distillation systems (POE) Consider acid neutralization of excessive alkalinity Reverse osmosis unit or distillation unit (POU)
Water Treatment
Acidity *Hardness
Alkalinity (high pH and sodium)
Other visual
Houseplants stunted or with burned leaf tips
Symptom Taste Taste of chlorine, gasoline, or oil
Cause VOCs, including residual chlorine, disinfection byproducts, pesticides, or fuel (gasoline, diesel, oil products) Acidity
Treatment devices Activated charcoal filter or aeration (POE)
Metallic taste
Acid neutralizing filters (POE) or addition of alkaline chemicals such as lime Reverse osmosis or distillation (POU)
Salty or bitter taste
*High total dissolved solids, sodium, sulfates, or nitrates (salinity) *VOCs, including residual chlorine, disinfection byproducts, pesticides, gasoline products Gasoline, diesel, oil products Algae products (geos-min and MIB) Excessive acidity, lack of oxygen in water source, or contamination by hydrogen sulfide gas (occurs naturally in aquifers and sediments) Pathogens
Chlorine-like smell
Activated charcoal filter or aeration (POU)
Gasoline-like smell Earthy, musty, or chemical smell Rotten egg odor
Activated charcoal filter or aeration (POU) Activated charcoal filter (POU)
Oxidation of water during aeration (POE) or chlorination and a particle filter (POE) or oxidizing filter (POE) followed by an activated carbon filter Acidity control may also be needed.
Water Treatment
Gastrointestinal problems such as diarrhea and vomiting
Remove source of contamination. Reduce pathogens through chlorination, UV radiation, or ozonation (POE). Chloramine chemicals may be used after chlorination is completed in order to maintain acceptable chlorine residual levels. Water softener (POE or POU) Use bleed-off mechanism to prevent buildup of salts and minerals (more information on Water Conservation website) Reverse osmosis unit or distillation unit (POU) Acid-neutralizing filters (POE) or addition of alkaline chemicals such as lime
Appliance/ hardware problems
Early applicance failure Poor evaporative cooler performance
*Hardness Build-up of scale on pads (high hardness, high salinity) High chloride levels High water acidity and high hydrogen sulfide
Blackened/tarnished metal utensils and pipes Blackened/tarnished metal utensils and pipes
4.11 Questions to Ask When Purchasing Water Treatment Equipment
In the past, the home water treatment industry focused on improving the aesthetic quality of drinking water. New products for home treatment claim to further reduce or eliminate contaminants in drinking water that may pose a health hazard. Product manufacturers now promise to make your drinking water "safe," "pure," and "contaminant free." Consequently, consumers are left to sift through advertising claims and technical data as they try to select the appropriate treatment method(s) best suited to address their water needs. Water Facts and Reminders: � All water sources contain minerals and some contaminants. If a water source meets the standards set by the USEPA, NPDWS, and NSDWS, it is considered safe to drink. No water treatment device can completely eliminate all minerals and all contaminants from water all of the time. Proven treatments, if properly operated and maintained, can reduce contaminants below NSDWS and/or NPDWS levels. Before buying a home water treatment device, know the quality of your water source and decide a) which contaminants you want reduced, b) to what level, and c) how much treated water you need every day.
Water Treatment
� �
� �
Home water treatment devices can break down and, if misused, can contaminate your drinking water. Home treatment devices require regular use and periodic maintenance. They are not "install and forget" devices.
Before purchasing a home water treatment system, the consumer should ask the following questions (or use them as guidelines). The extent to which a manufacturer or distributor is willing to provide answers can help the consumer make an informed choice.
What exactly does your analysis of the water show? Are health hazards indicated? Which ones? Ask for specifics. Should more testing be done? Many water treatment companies include free in-home testing of the water. Most contaminants cannot be evaluated this way. For example, organic chemicals and trace metals, which have been associated with serious health problems, must be analyzed in a laboratory with sophisticated equipment. You should be wary of home analyses claiming to determine more than basic water quality constituents such as TDS, hardness, pH, iron, and hydrogen sulfide. It is best to rely on water testing done by an independent laboratory. Have the product and the manufacturer been rated by the National Sanitation Foundation (NSF) or other third party organizations? Was the product tested (1) for the specific contaminant (or group) in question, (2) over the advertised life of the treatment device (with more than 1 gallon of water), and (3) under household conditions (including local tap water quality, actual flow rates, and pressures)? What is the performance value (removal efficiency and water purity) of this device? And who guarantees the performance and for how long ? The NSF, whose function is similar to the Underwriter's Laboratory for electrical and electronic products, sets performance standards for water treatment devices. Because companies can make unsubstantiated statements regarding product effectiveness, you must evaluate test results of the device to determine if claims are realistic. Keep in mind that the water treatment system you are evaluating may have components that are NSF approved, but that the entire system may not have been evaluated (for more information about NSF, contact them at 800-NSF-MARK or at www.nsf.org; for other valuable links, see Section 6.2). Does the water quality problem, as determined by a certified laboratory analysis, require whole-house treatment? Or, will a single-tap (POU) device be adequate? 74
Water Treatment
Although less than 1% of tap water is used for drinking and cooking, some contaminants are as hazardous when inhaled or absorbed through the skin as when ingested. Treatment of all the water used in the household may be required. Reverse osmosis and distillation units are connected to a single tap; activated carbon devices can be installed on a single tap or where water enters the house. The device selected depends upon the type and level of the contaminant in question. Remember to use a state certified laboratory for your analysis. Contact the ADHS Bureau of State Laboratory Services at 602-255-3454 for a list of certified laboratories in Arizona (see also Section 6.2). Will the unit produce enough treated water daily to accommodate household usage? If a filter or membrane is involved, how often does it need to be changed, back-flushed, or regenerated? How does one know when to do it? Besides maintaining filters and membranes, are any other types of maintenance needed? How often? Who does it? What does it cost? Be sure that enough treated water will be produced for everyday use. The maximum flow rate should be sufficient for the peak home use rate. All proven home treatment devices such as activated carbon units, reverse osmosis units, and iron filters need routine maintenance. You should be fully informed of all maintenance requirements.
Water Treatment
What is the total purchase price plus the expected maintenance costs (monthly/annual) of the device? Will the company selling the device also install and service it, and will there be a fee for labor? Can you perform maintenance tasks, or must a water treatment professional be involved? Will the unit substantially increase water and/or electrical usage in your home? Watch out for hidden costs such as separate installation fees, monthly maintenance fees, or equipment rental fees. Additionally, the disposal of waste materials (such as reject water, spent cartridges from activated carbon 75
units, and used filters) can add to the cost of water treatment and should be figured into the purchase price. Some devices can be installed by the homeowner. Is there an alarm or indicator light on the device to alert you to a malfunction? Many units have backup systems or shutoff functions to prevent you from consuming untreated water. Will the manufacturer include in the purchase price a retesting of the water after a month or two? Testing the water a month after the device is installed will assure you that the unit is accomplishing the intended treatment. Remember, testing for specific contaminants can be very expensive. What is the expected lifetime of the product? What is the length of the warranty period? What does the warranty cover? The warranty may cover only certain parts of a device, so you should be aware of the warranty conditions.
Water Treatment
Are you sure this is the right water filter for me?
Artist: Judi Ellwanger
Final Remarks These guidelines are directed at individuals who are planning to consult a water treatment industry representative or who are planning to do their own research into water treatment devices. Be aware that treatment can be for aesthetic as well as for health factors. If drinking water poses a health risk, you should also consider the cost of purchasing bottled water as an alternative to treatment. Monetary compensation for treatment of problem water resulting from environmental contamination may be possible. Contact the Arizona Department of Environment Quality (1-800-234-5677) for more information concerning this option.
Water Treatment
Portions of this text have been adapted from Wagenet and Lemley, 1989b.
5. Glossary
Acid neutralizing filters are used to reduce water acidity. They contain some form of crushed calcite or other carbonate-based mineral. Like all filters, they must be replaced periodically. Acidity is the total amount of acid and acid forming substances in water. See also pH. Acre-foot equals 1 acre area filled with 1 foot of water. This volume of water is approximately 325,851 gallons or 1.24 million liters. ADEQ (the Arizona Department of Environmental Quality) administers all of Arizona's EPA programs and regulates public water systems that have at least 15 service connections or serve 25 people. ADWR (the Arizona Department of Water Resources) has established five Active Management Areas (AMAs) to manage and balance the availability of groundwater resources until 2025. Aeration or air stripping is a water treatment process that uses forced air to remove volatile contaminants from water. Aggressive water refers to low (TDS) mineral or mineral-free water. It easily dissolves minerals from pipes including scale deposits and metal pipes. Aggressive water is also corrosive. Only plastic piping and containers are recommended to transport mineral-free water. Alkalinity is the total amount of bicarbonate and carbonate ions present in water, reported in mg/L of calcium carbonate (CaCO3). Water alkalinity helps protect (buffers) against abrupt pH changes, limiting its range to between 7.5 and 8.5. Alkalinity and hardness also control pipe scale formation. There is no drinking water standard for alkalinity. AMAs or Active Management Areas are set by the ADWR to manage and balance groundwater resources in Arizona. Anions are negatively charged ions. Examples: chloride and sulfate. Aquifers are bodies of porous and permeable geologic material that can contain and transfer groundwater. Arid climates (as in Arizona) average less than 12 inches of rainfall per year. The high heat and low humidity of these climates can evaporate more than 100 inches of water per year from exposed containers. 79
B Benzene is a volatile organic chemical used as an industrial solvent and is a major component of gasoline. BDL (below d
Click tabs to swap between content that is broken into logical sections.