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Quality Assessment of Surface Water for Domestic and Agricultural Purposes Using Hydro-chemical and Microbial Studies in Kilifi County, North Coast Region of Kenya

1 Department of Biochemistry, School of Biomedical Sciences, Jomo Kenyatta University of Agriculture and Technology, Nairobi, Kenya. 2 Department of Pure and Applied Sciences, School of Applied and Health Sciences, Technical University of Mombasa, Mombasa, Kenya. Department of Medical Biochemistry, Medical School, Mount Kenya University, Thika, Kenya. 4 Department of Medical Microbiology, Medical School, Mount Kenya University, Thika, Kenya. Department of Environmental Sciences, School of Pure and Applied Sciences, Pwani University, Kilifi, Kenya.

, CO 3 2-, HCO 3 -and NH 4 + were determined using Ion Exchange Chromatography. Cations; Na  3 -, CO 3 2-, HCO 3 -, NH 4 + , K + , Ca 2+ , Mg 2+ , Cd 2+ , Cr 3+ , Al 3+ and Ag + were below WHO limits. The study concludes that water sources in Kilifi County are unsuitable for domestic and agricultural uses. It's recommended that a continuous water quality monitoring program be put in place and development of effective management practices for utilization of the surface water resources be instituted.

INTRODUCTION
One of the major environmental concerns throughout the Coastal regions of the world is salinity [1][2][3][4]. The economic viability brought about by growth and development of countries depends on Agricultural production system [5]. However, this depends on the quality of natural resources used for Agricultural productivity [6]. Salinized water resources constrain Agricultural and economic development by creating a hostile environment for normal crop production in Coastal belts of many countries [3][4][5]. The organic matter of Coastal soils is very low and highly salinized [3][4][5] resulting into deficiencies of Nitrogen (N), Sodium (Na) and Potassium (K) and a wide spread of micronutrients such as Copper (Cu), Zinc (Zn) among others [5]. This has negatively affected the economy of many countries in the Coastal regions of the world [3][4][5] due to reduction in Agricultural productivity. Furthermore, reduction in fresh water flow from the upstream tidal flow and ground water discharge exacerbate the problem [2,4]. Although salinity challenges have been identified and management strategies put in place [7,8], they still affect plant health and productivity [9][10][11][12][13][14][15] and human health [16][17][18][19].
The Coastal belt of Kenya consists of 6 Counties; among them is Kilifi County [20].  [20]. The population was projected to rise to 1,841,958 (47.8% males and 52.2% females) by the year 2025 at a mean intercensual annual growth rate of 3.05% [20]. The males represent 48.4% while the females represent 51.5% of the total population indicating a male: female ratio of 1:1.065 with the County's dependency ratio standing at 101.45% [20]. Kilifi County has a versatile child rich population, where 0-14 year olds constitute 47% of the total population. In Kilifi County, 16% of the population have no formal education, 23% have primary education and 39% have secondary level of education or above and are salaried employees [20]. The population of Kilifi County represents Kenya's fastest growing demographic population and thus requires corresponding food security and economic stability to be addressed.
Agriculture is one of the most important economic activities that support livelihoods of many communities within Kilifi County. However, the County experiences erratic rainfall patterns just like other Counties within the Coast region [4]. Consequently, the County depends on rain fed Agriculture practices, which give rise to insufficient Agricultural produce to sustain the ever growing population of the County. This pose a constant threat to food security in the County. The problem is further complicated by high microbial load and salinity levels of the water available [4,21], that hinders Agricultural advancement within the County. In a bid to bridge food security issues, several nongovernmental organizations (NGOs), including Japan International Corporation Agency (JICA), World Vision, DANIDA, United Nation's (UN) World Food Program (WFP) and Plan International partnered with the County Government of Kilifi to boost Agricultural activities. Some of the projects include Mudachi Irrigation Scheme (MIS) in Ganze sub-county establish by JICA, Galana Irrigation Scheme (GIS) in Malindi and Magarini sub-county by the central Government and Water Pan Project established by World vision in collaboration with WFP in Kaloleni sub-county, which aims at providing quality water for both domestic and Agricultural use.
Although the establishment of MIS and GIS were intended to improve the economy of the north Coast of Kenya [22], the success of these projects is tied to the availability and quality of the water [6,[23][24][25][26]. The MIS pays greater attention to production of horticultural crop leaving the burden of livestock production entirely to the farmers. River Nzovuni, the only source of water for MIS, also utilized for domestic purpose presents salinity and mineralization challenges necessitating scientific research and worthwhile interventions [22]. The crops grown in MIS have shown wilting suggesting the use of poor quality water [27], thus resulting in low productivity. The upstream of River Nzovuni including the source is fresh. The salinity level however, increases as the river flows through the Coastal lowlands and drains into the Indian Ocean via the Kilifi creek. Other rivers such as River Kombeni, River Mbogolo, River Rare, River Mukulu, River Galana (Sabaki) among others are suspected to follow the same trend just like River Nzovuni. The ocean water intrusion during high tides, dissolving bedrocks and industrial waste deposition are suspected cause for the salinity of the rivers and any other surface water source [3,4]. The quality of water for both domestic and Agricultural use has been evaluated in several studies in several countries including Kenya [4,[28][29][30][31][32][33][34][35][36][37][38][39][40][41][42]. However, none was conducted in Kilifi County. Therefore, the quality of surface water within the county for its suitability for both domestic and Agricultural use need to be evaluated for the improvement of Agricultural productivity.

Description of Study Area and Sampling
The study was carried out in Kilifi County situated in the northern part of the Coast province of Kenya ( Fig. 1 [20]. Water samples were collected from twenty-five (25) different sampling sites located in different administrative locations within Kilifi County (Table 1).

Collection of Water Samples
Water samples were collected randomly with different sites in Kilifi County for analysis of salinity indicators in 2018. Three collected water samples were mixed together for making a sample for each location. Samples were collected in 100 mL polyethylene plastic bottles. Each bottle was cleaned thoroughly by rinsing with diluted HCl followed by washing with distilled water. The water samples were filtered with Whatman 42 to remove suspended solids. Prepared sample solutions were sealed immediately to minimize exposure to air, and collected samples were transported within 48 hrs in a cooler box to the Environmental Science Laboratory of Jomo Kenyatta University of Agriculture and Technology (JKUAT) and and Directorate of Research Grants and Endowments Laboratories Mount Kenya University (MKU). The samples were refrigerated at 4°C prior to analysis.

Analysis of Physico-chemical Properties of the Water Samples
The pH, electrical conductivity (EC), Salinity, Temperature, and Total Dissolved Solids (TDS) were determined in situ using a portable multiparameter meter, Temp/pH/TDS/EC meter (Model MI 1399) as described by Jackson [43] ) were determined using Ion Exchange Chromatography (IEC) (Model: Dionex ICS-1600) as described by APHA 4110 method [44]. The samples and standard solutions were digested for 30 minutes on a hot plate in fume hood after which they were filtered and transferred to 100-mL volumetric flask. Prior to the analysis of Potassium, Sodium, Magnesium and Calcium in the water sample, 5 mL of 71% HNO 3 was used to digest 100 mL of the samples for 30 min on hot plate in a fume hood. Sodium (Na

Bacteriological
Analysis of the Collected Water Samples

Isolation and enumeration
Ten (10) mL of the water samples were diluted with 90 mL sterile peptone water and thoroughly mixed. About 0.1 mL aliquot of each of the diluted samples were inoculated onto presterilized Nutrient agar (NA) and solidified plate count agar (PCA) as basal medium. Presumptive isolation of coliform bacteria was made on MacConkey broth. Multiple tubes containing 1 mL, 0.1 mL and 0.01 mL samples were inoculated onto test tubes each containing 10 mL of single-strength MacConkey broth incubation at 37°C for 48 hours and the tubes with acid and gas were considered positive for coliforms. Fecal and total coliform counts were performed using the standard membrane filtration technique as described by APHA [44]. The distribution of positive tubes was used to determine the Most Probable Number (MPN) of total coliform count following standard probability table as described by APHA [44]. Further, the presence of Escherichia coli was confirmed by streaking loopful of broth culture onto Eosine Methylene Blue (EMB) agar and evaluating for the formation of metallic sheen color as described by APHA [44].

Detection of salmonella
Pre-enrichment was performed by aseptically inoculating 1 mL of each sample into 10 mL of lactose broth (LB) and incubated at 37°C for 24 hours. Thereafter, 1 mL culture was transferred into 10 mL of Rappaport-Vassiliadis broth (selenite cystine broth) as secondary enrichment broth and incubated at 42°C for 48

Data Analysis
The data were analyzed using SPSS statistical software (version 20). Results of physicochemical analysis and mean microbial counts of the investigated water samples were compared with the set standards [18] and interpreted as acceptable or unacceptable.

Hydro-chemical Properties of Water
The hydro-chemical properties of water samples collected from the twenty-five (25) sampling points within Kilifi County are given in Table 2.
The pH values of the collected samples ranged from 6.890.06 (RNUS) and 9.650.30 (RNDS) with an average value of 7.420.52. The sample RNDS recorded pH value above the World Health Organization (WHO) recommendation for both drinking and irrigation water (6.5 -8.5). The temperature readings of the collected water samples ranged from 23. ), salinity and turbidity, the results from the study were above these set limits.     Table 4. The concentration of Fin sample collected ranged between 0.420.04 mgL -1 (MWT) to 3.910.08 mgL -1 (CD). On average the Flevels in the water sources from Kilifi County was 2.900.24 mgL

Microbial Load of Water Sources
The mean microbial counts for E. coli, total coliforms, S. aureus, S. typhi and Shigella in the water sources in Kilifi County are shown in Table  5. The positive samples after 24 hrs incubation in different medium are presented in Fig. 3.
Generally, the water sources from Kilifi County had high microbial load as depicted by the values, MPN, faecal coliforms and total coliforms. The MPN of water samples from Kilifi County ranged between 00.0±0.00 CFU 100 mL -1 (MWT) and 44351.00±890.00 CFU 100 mL

DISCUSSION
Agricultural production in arid and semi-arid areas is entirely dependent on irrigation. Therefore, irrigation water should have little or no dissolved salts, which would harm the plant and/or alter soil properties, reducing the amount of agricultural produce. Such quality water is often not available in arid and semi-arid forcing farmers to go for saline water for irrigating their plants. Different cations and anions are inconsistent in saline water. The degree of salinity effects on crops, livestock and aquatic life may not be the same [47]. Water of such substandard quality usually lacks some aspects of plant nutrient requirements. The plants grown using saline water are not optimally productive and the soil requires intensive treatment to recover its usefulness. The pH values of the water samples analyzed are within the permissible levels of pH from FAO, which range from 6.50 to 8.40 [18]. The high pH levels can be attributed to high calcium concentration (4.000.16 mgL -1 ) obtained from the study. Drinking water should have a temperature which is equal to or less than 15°C. Temperature above 15°C enhances the growth of nuisance organisms leading to increase in problems related to odor, taste, color and corrosion. In livestock production, cattle prefer drinking water at temperatures between 4.4 o C and 18.3°C. Temperature more than 27°C decrease water and feed intake rates affecting animal productivity [48].
The EC depends on concentration, mobility, valence, type of ions present and temperature [42,49]. As a parameter used to assess water purity, it indicates the amount of total dissolved ions [46]. The average value EC of water sources from Kilifi County (3.440.75 dScm -1 ) were above the WHO guidelines value (3. , Na + , Mg 2+ and Ca 2+ among other dissolved ions. The levels of dissolved ions in the surface water sources from Kilifi County were significantly high (Table 3 and Table 4) which may have resulted from runoffs from agricultural farms. Safe drinking water sources had EC values of less than 3.00 dScm -1 . High EC values of between 1.00 dScm -1 and 2.9 dScm -1 in drinking water may cause mild diarrhea, whereas above 3.00 dScm -1 , domestic animals may detest water drinking, considered a precursor for acute diarrhea [18]. Excessive concentrations of boron, Cl -, HCO 3 -, Na + among other ions have been implicated in specific ion toxicity [50,51]. Similarly, cations, anions and EC in Kilifi County water sources were recorded at an extremely toxic levels. For instance, the water EC in this study was found to be 3.440.75 dScm -1 , while recommended values are 0.75 -4 dScm -1 and 3.00 dScm -1 for domestic and agricultural use respectively [18].
Studies conducted elsewhere have suggested an increase in salinity across Coastal belts at a rate of 39% by 2050 [2]. The intensity and spread of salinity across the Coastal belts are due to changes of sea level rise, temperature, acidic rainfall, altered riverine flow and sea water intrusion [2][3][4][5]. Extreme levels of soil and water salinity trends across Coastal belts in many countries of the world negatively affect crops, fish, and livestock production [5,47]. Coastal Agriculture provides livelihood support for its community with several groups of people often suffering a shortage of freshwater in different areas of these Coastal belts [52,53]. Many regions in the world along the Coastal belt use saline water for food crop cultivation, fodder crop production, drinking, and bathing [1,3,4]. This increased usages of saline water have contributed to enormous negative effects on Agricultural production systems and products as well as human health [19,54,55]. This lack of quality drinking water can result into overconsumption of saline water leading to malnutrition, under nutrition, water and food borne diseases and even starvation among Coastal people [5,19,[56][57][58]. Crops, livestock and fish production have been negatively affected due to the high salt in the Coastal belt [59][60][61]. The TDS is the sum of all components dissolved in water including K + , Na is recommended for human use [18]. High TDS in water may impair physiological processes leading to gastrointestinal irritation in individuals with kidney problems [62]. Further, high TDS renders the water unfit for industrial use due to scales formation, accelerated corrosion and precipitate foaming in boilers besides interfering with the taste and color of final industrial products [63].
The toxicity of various metals is also a point of concern. In this study, the average concentration of Na + was 8751.80214.04 mgL -1 which is approximately 44 times above the permissible limit of 200 mgL -1 [18]. The high Na + levels may result from sewage discharge, domestic effluents, leachates of Na + containing rocks and recharge water from underground systems which are rich in brine [42]. With absence of desalination plants to extract the brine in the water, these regions experiences low Agricultural productivity. Moreover, fractures within water sources such as rivers may lead to mineralized regimes producing mineral veins and saline intrusion which in turn result in the elevation major ions [42]. Kilifi County being adjacent to the Indian Ocean suffers from the effect of seawater intrusion [3,4] contributing further to the concentration of major ions in water sources. High levels of Na + in drinking water has been associated with hypertension in pregnant women [64] and children [65], fluid loss (dehydration), hypernatraemia and neurological damage [65,66]. There is no recommended limit of K + in water. However, increased exposure may lead to significant health effects in individuals with kidney disease, heart disease, coronary artery disease, hypertension, diabetes, adrenal insufficiency, aging and specific medications [67,68].
Presence of heavy metals such as Cd 2+  in water sources indicate pollution and make the water harmful if they are in excessive concentrations [35]. They poison aquatic ecosystems destroying life while poisoning the water resources besides being a threat to crop production [11,33]. Accumulation of metals in the plants and soil occur due to continued use of metal loaded water for agricultural purposes [68]. Bioaccumulation or biomagnification of these metals via plants lead to their entry into human bodies as they consume these plants produce posing risks to human health [15,16,18] . Some water sources were within the limit while others had Cu 2+ concentrations higher than the permissible levels. The average levels of Cr 3+ and Cd 2+ in the water sources were found to 0.350.01 mgL -1 and 0.070.01 mgL -1 respectively and such high levels are toxic for continued irrigation use.
On average, the F in the study was found to be 2.900.24 mgL -1 . These values were considerably above the recommended guideline for drinking water set at 1.5 mgL -1 [18]. High F in drinking water may lead to dental and skeletal fluorosis [69] as evident in Nakuru County around Salgaa and Molo in Kenya [42]. Skeletal fluorosis may be manifested upon drinking water containing 3 to 6 mgL -1 of F - [69,70]. Although moderately high values of Fwere obtained in this study, signs of dental and skeletal fluorosis are not common in Kilifi County. This may be attributed by the fact that many parts of Kilifi County have a good and well maintained piped (tap) water system provided by Malindi Water and Sewerage Company (MAWASCO) and Kilifi Mariakani Water and Sewerage Company (KIMAWASCO).
The study established that the average value of SO 4 2was 300.6442.47 mgL -1 which is below the permissible limits of 400 mgL  which was above permissible limit of 0.5 mgL -1 [18,72]. This may be attributed to use of fertilizers and weathering of rocks (gypsum) [42]. Although PO 4 3is not very mobile in soils and only moderately soluble, transportation through surface runoff and soil erosion significantly increase its solubility in surface waters [73]. Further, PO 4 3is not harmful to humans but has a significant impact on natural ecosystems as a result of eutrophication. It damages the health of water sources due to massive growth of algae (algal bloom) clouding water and reduce sunlight available to other plants [73] The death of algae as a result of consumption in the water by algae biodegradable bacteria deprive aquatic systems of oxygen leading to suffocation of aquatic life [63]. limits for safe drinking water (18,48]. The sources of nitrates include animal and human waste, industrial effluent, use of chemicals, fertilizers and silage through drainage systems [69]. High NO 3 levels above 40 mgL -1 in water has been associated with "blue baby syndrome" or "methemoglobinemia" in children as experienced in some of the Coastal regions of the world such as the Gaza Strip of Palestine [65,70]. The average value of Cl -(1756.68900.60 mgL -1 ) in the collected water samples was significantly high above the permissible limit of 250 mgL -1 and thus pose health risk to consumers. In the present study on the bacteriological analysis of the water samples, it was observed that 24 out of 25 samples (96%) did not reach the standard of 0.0000 MPN 100 mL -1 recommended WHO guidelines for drinking water. The transformation of nutrient broth from clear to cloudy is a clear indication of microbes in the water. From the observed levels of microbiological organisms, it can be safely concluded that the microbiological quality of the water sources in Kilifi County present a challenge to the utilization of the various water sources both for domestic (drinking) and agricultural (irrigation) purposes. Microbial hazards in irrigation water have been on the rise owing to contamination of surface water. Increased levels of microbial load have been directly linked to the increase in food-borne diseases in the developing world [19]. Horticultural production is perhaps the most relevant since the produce is consumed raw. Farmers are required to use microbe-free water for irrigation. This will allow the production of potentially germ-free food [27]. Microbes such as E. coli and Salmonella draw particular concerns for their effects on human enteric health [19]. Farmers are required to assess the water before using it on farm. Risk assessment enables these farmers to predetermine the potential risk of illness posed by the water in question prior to using it. The production of Leafy and low growing crops, for instance, vegetables calls for the use of highly sterile water to avoid spreading contamination to the population and other parts of the farm. The drinking of such water also poses a health risk to the consumers including poor enteric health, diarrhea and stomach upsets [74].

CONCLUSION
This Coastal area in Kenya constitutes 20% of the country of which about 53% is affected by different degrees of water salinity [4]. In fact, declining land, fish, and livestock productivity with a shift toward negative nutrient balance is among the main concerns for food security problems in the country. High pH values as demonstrated in this study indicates alkalinity of Kilifi County water sources possibly due to fertilizers application in nearby farms around the sampling area in addition to other anthropogenic sources. The temperature, TDS, EC, F-, Br -, PO  2 -and NO 3 were below the WHO permissible limits. Further, the microbial load of the water source in Kilifi County was above the required limit of < 2 CFU 100 mL -1 . Most of the water sources from Kilifi County are highly saline containing significant levels of copper, calcium, zinc, cadmium, and chromium. The copper, zinc, and cadmium pose potential risks following longterm irrigation within the county's farmlands. The reduced crop yields in the scheme can be attributed to the quality of the water and poor Agricultural practices such as the use of gross Agricultural chemicals and fertilizers. In turn, this may lead to soil infertility and possible desertification. The high values of these parameters makes the Kilifi County water sources unsuitable for irrigation as well as domestic use. Further, these high concentrations may serve as precursors for water and food borne diseases among other diseases including fluorosis and hypertension. The significant high Samonella, Shigella, and E. coli of < 2 CFU 100 mL -1 exposes the local population around these farms to a risk of enteric infections. Due to weak policy implementation on monitoring of agricultural and domestic water quality, the salinity problem in the county continues to impact negatively on food quality and food security.

RECOMMENDATIONS
For domestic and agricultural irrigation purposes, farmers in Kilifi County may be advised to continuously monitor the sampled water sources due to high salinity. Desalination of the water may not be an option since the process is capital intensive. Rather, they ought to find alternatives for metal based fertilizers and herbicides on their farms in order to lower salinity levels in the water. Industries and homes in the vicinity of the sampled water sources should design befitting waste disposal schemes. Better disposal of wastes would save the farmers and the locals from the salinity hazards in their face. The government may consider harvesting the water from the sampled water source and putt up water treatment plant (s) to supplement the already existing Baricho water treatment plant that is being used by MAWASCO and KIMAWASCO since some parts of the Kilifi County are not supplied with the piped (tap) water system. Treating the water before use would go a long way in saving farmers from microbial hazards. Maintaining proper hygiene alongside the use of latrines is also crucial in reducing the microbial load of the water sources. It is significantly important to explore the possibilities for increasing agricultural production for the growing population in Kilifi County. Thus, combating this land salinization problem is a vital issue for food security in the country through adoption of longterm land management strategies. Further studies should be conducted especially in the piped (tap) water system to establish its suitability for domestic purposes.

ACKNOWLEDGMENTS
The authors would like to acknowledge the Environmental Science Laboratory at Jomo Kenyatta University of Agricultural and Technology (JKUAT) and Directorate of Research Grants and Endowments Laboratories Mount Kenya University (MKU) where the samples were analyzed. The authors are also thankful to the community in Kilifi County for their support during sample collection. Finally, they are especially thankful to the National Research Fund (NRF-2018), Kenya, for their valuable funding.

DISCLAIMER
The products used for this research are commonly and predominantly use products in our area of research and country. There is absolutely no conflict of interest between the authors and producers of the products because we do not intend to use these products as an avenue for any litigation but for the advancement of knowledge. Also, the research was not funded by the producing company rather it was funded by personal efforts of the authors.