text:
Journal of Chemistry
Volume 2016, Article ID 3796352, 12 pages
Greenhouse Gases Emissions from Wastewater Treatment Plants: Minimization, Treatment, and Prevention
1Facultad de Ingeniería y Ciencias, Universidad Adolfo Ibáñez, Avenida Padre Hurtado 750, 2520000 Viña del Mar, Chile
2Department of Chemical Engineering, School of Engineering, University of Santiago de Compostela, Rua Lope Gómez de Marzoa s/n, 15782 Santiago de Compostela, Spain
3Department of Environment, Faculty of Engineering, University of Playa Ancha, Avenida Leopoldo Carvallo 270, 2340000 Valparaíso, Chile
4School of Biochemical Engineering, Pontifical Catholic University of Valparaíso, Avenida Brasil 2085, 2340000 Valparaíso, Chile
Received 28 December 2015; Revised 29 March 2016; Accepted 5 April 2016
Academic Editor: Claudio Di Iaconi
Copyright © 2016 J. L. Campos et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
The operation of wastewater treatment plants results in direct emissions, from the biological processes, of greenhouse gases (GHG) such as carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), as well as indirect emissions resulting from energy generation. In this study, three possible ways to reduce these emissions are discussed and analyzed: minimization through the change of operational conditions, treatment of the gaseous streams, and prevention by applying new configurations and processes to remove both organic matter and pollutants. In current WWTPs, to modify the operational conditions of existing units reveals itself as possibly the most economical way to decrease N2O and CO2 emissions without deterioration of effluent quality. Nowadays the treatment of the gaseous streams containing the GHG seems to be a not suitable option due to the high capital costs of systems involved to capture and clean them. The change of WWTP configuration by using microalgae or partial nitritation-Anammox processes to remove ammonia from wastewater, instead of conventional nitrification-denitrification processes, can significantly reduce the GHG emissions and the energy consumed. However, the area required in the case of microalgae systems and the current lack of information about stability of partial nitritation-Anammox processes operating in the main stream of the WWTP are factors to be considered.
1. Introduction
In the past years most efforts to improve wastewater treatment plants (WWTPs) performance have been focused on obtaining a good effluent quality [1–5]. However nowadays, new challenges are under consideration, oriented to ensure the sustainability of WWTPs in terms of their economic feasibility and environmental impact. Energy consumption and greenhouse gases (GHG) emissions are among the aspects that have become key-factors concerning the overall performance of the WWTPs [6, 7]. Recent studies have identified the WWTPs as potential sources of anthropogenic GHG emissions, contributing to climate change and air pollution [8–10]. WWTPs produce carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) during the biological wastewater treatment processes and CO2 is also emitted during the production of the energy required for the plant operation. The CO2 released due to the energy demand can be directly reduced by enhancing the energy efficiency of the WWTPs. In this way both the reduction of environmental impacts and the decrease of treatment costs by enhancing the energy savings can be accomplished simultaneously.
With regard to each GHG source the N2O emitted is generated by nitrification and denitrification processes used to remove nitrogenous compounds from wastewater. Its production occurs mainly in the activated sludge units (90%) while the remaining 10% comes from the grit and sludge storage tanks [11]. N2O gas is an intermediate of biological processes such as heterotrophic denitrification and nitrification (Figure 1). It is formed during denitrification operated at low pH values and toxic compounds or low dissolved oxygen (DO) concentrations are present in the media [12–14]. Nitrifying bacteria are able to produce N2O under aerobic or anoxic [15] conditions. In anoxic conditions, both ammonia- and nitrite-oxidizing bacteria are able to produce it, while only ammonia-oxidizing bacteria do it in aerobic conditions. In the latter case, the production is stimulated by the presence of low DO concentrations and presence of nitrite () or organic matter in the liquid media [12, 13]. Nitrous oxide can be produced also from chemical reactions taking place in the presence of hydroxylamine and nitrite [16].
In practice nitrous oxide is emitted in the WWTP predominantly in the aerobic tank [17]. However, the contribution of the anoxic and aerobic reactors to this production remains still unclear since it can be produced in the anoxic stage and be subsequently stripped to the gas phase in the aerated compartment [18]. Ammonia-oxidizing bacteria have been identified as the main N2O producers while heterotrophic denitrifying bacteria contribution is only relevant when nitrite and/or oxygen are present in the anoxic stage [19]. According to Tallec et al. [20], under common operational conditions, the N2O production occurs mainly via denitrification by nitrifying bacteria. However hydroxylamine oxidation pathway can be the main process responsible for the production of N2O emissions at high ammonia () and low nitrite concentrations, when a high metabolic activity of ammonia-oxidizing bacteria is present (at 2 to 3 mg O2/L) [19].
With regard to CH4 emissions, Daelman et al. [21] found out that about 1% of the incoming chemical oxygen demand (COD) to the WWTPs was emitted as methane. This amount exceeds the amount of carbon dioxide emission that was avoided by utilizing the produced biogas in anaerobic digestion. The main sources of methane detected by these authors were related to the sludge line units where anaerobic digestion is carried out: the primary sludge thickener, the centrifuge, the exhaust gas of the cogeneration plant, the buffer tank for the digested sludge, and the storage tank for the dewatered sludge. These units contribute to around 72% of methane emissions of the WWTPs while the remaining emissions come from the biological reactors and can be mainly attributed to the CH4 dissolved in the wastewater which is not totally removed by the biological system. Research works of Yver Kwok et al. [22] and Oshita et al. [23] also showed that most of the methane emissions from WWTPs are closely related to processes involved in the sludge line.
With respect to CO2 its production is attributed to two main factors: biological treatment process and electricity consumption. In the main stream of the WWTP the organic carbon of wastewater is either incorporated into biomass or oxidized to CO2. In the sludge line, it is converted mainly to CO2 and CH4 during anaerobic digestion and, finally, methane is oxidized to CO2 during biogas combustion.
In recent literature the emissions of GHG from the conventional configurations of WWTPs were determined but the analysis of the possible alternatives to minimize these emissions is generally not done [24–28]. On the other hand, most of the papers studying the application of new processes to remove pollutants from wastewaters are mainly focused on the energy savings [29–32] and only few of them also give an environmental evaluation [33–36]. Therefore, the main objective of this work is to provide an overview of all possible ways to reduce GHG emissions from WWTPs. For that, two possible scenarios are discussed and analyzed: to maintain the present scheme of operation of the WWTP and to modify the operational conditions (minimization) or to implement capture and treatment units for the gaseous streams (treatment) and to change the scheme of operation and to implement new processes which produce lower GHG emissions than the existing ones (prevention).
2. Minimization of GHG Emissions
Perhaps, the most efficient way, in terms of costs, to reduce GHG emissions is to modify the operational conditions of WWTPs units but this is not always possible due to the operational limitations of the installed units. In the following sections, some recommendations about the possible actions to put in practice to operate WWPTs in order to reduce GHG emissions are provided.
2.1. N2O Production
Data obtained from the operation of full-scale WWTPs show a wide range of values for the fraction of nitrogen that is emitted as N2O (0–14.6% of the nitrogen load) [12]. Such large variation can be related to the different operational conditions imposed in the studied WWTPs. Having this in mind decreasing the amounts of N2O emitted from activated sludge processes presents a great potential for improvement, by avoiding those operational conditions identified as responsible for its production. Some identified conditions are (i) low dissolved oxygen concentration in the nitrification and the presence of oxygen in denitrification stages, (ii) high nitrite concentrations in both nitrification and denitrification stages, (iii) low COD/N ratio in the denitrification stage, (iv) sudden shifts of pH and dissolved oxygen and ammonia and nitrite concentrations, and (v) transient anoxic and aerobic conditions [12, 13].
Therefore, to minimize N2O emissions, biological wastewater treatment plants should be operated at high solid retention times (SRT) to maintain low ammonia and nitrite concentrations in the media. Furthermore large bioreactor volumes are recommended to dispose of systems able to buffer loadings and reduce the risk of transient oxygen depletion. N2O emissions can be also reduced if nitrous oxide stripping by aeration is limited since microorganisms would have more time to consume it [37].
2.2. CH4 Production
CH4 emissions can be minimized if thickening sludge tanks and sludge disposal tanks are covered to avoid gas leakages and their emissions are captured by hoods which could be burnt with excess biogas in a torch [21]. Besides the methane produced in the plant itself, methane also enters the plant from outside via the influent since it contains CH4 that has been formed in the sewer. The methane load was estimated as 1% of the influent COD load and is mainly oxidized in the activated sludge tanks (80%), which could be exploited as a means to further decrease methane emissions from wastewater treatment [21].
2.3. CO2 Production
Organic matter oxidation in the biological reactors and combustion of CH4 are responsible for the direct CO2 emissions while indirect emissions are attributed to the energy consumption of the WWTP [26]. The SRT applied to the biological reactor is a key operational factor that affects these emissions. The operation of the activated sludge system at high values of SRT promotes endogenous respiration of biomass which increases the amount of COD oxidized to CO2 and decreases the overall sludge production. This decrease of sludge production implies a decrease of the methane production and, therefore, a decrease of the CO2 emissions associated with its combustion [38]. Both tendencies counteract each other and the addition value of both quantities remains almost constant. Furthermore, the decrease of the SRT also involves an increase of the energy efficiency of the WWTP and, therefore, a decrease of indirect CO2 emissions. Therefore, CO2 emissions should be minimized by applying the shortest SRT value as possible without negatively affecting the effluent quality.
The effect of SRT on the overall CO2 emissions of a conventional WWTP can be quantified by performing mass and energy balances according to the methodology described by Campos et al. [39] and using the parameters given in Table 1. The SRT values tested ranged from 10 to 30 d in order to guarantee a stable nitrification. Results showed that an increase of the SRT from 10 to 30 days supposed an increase of 7.6% of the CO2 emissions (Figure 2).
3. Treatment
A second possible option to reduce GHG emissions from WWTPs is to capture and treat them. An important number of technologies are available to destroy or capture N2O, CH4, and CO2 from industrial gaseous streams but there is still a need for the development of efficient low-cost abatement technologies to treat gaseous streams from WWTPs. On the other hand, the capital costs required to cover the different tanks and capture GHG emissions are relatively high [47].
3.1. N2O Removal
Traditional technologies, such as selective catalytic reduction and selective noncatalytic reduction, are currently used to control NOx emissions from power plants [48–50]. However, both processes require operating at high temperatures or using catalysts, which revert to high installation and maintenance costs. These total costs become prohibitive in large-scale facilities treating air flows containing low-to-moderate concentrations of NOx [51]. Recently, many different bioprocesses, using nitrifying and denitrifying bacteria or microalgae, have been developed to control NOx gas emissions. Technologies based on the denitrification process have been successfully used to remove N2O with efficiencies of 75–99% [51–53]. However, the low aqueous solubility of this greenhouse gas limits the mass transfer rate from the air flow to the liquid phase and, therefore, high hydraulic retention times (HRT) are required to achieve high N2O removal efficiencies. These long applied HRT result in large bioscrubber (or biofilter) volumes, with the subsequent increase in capital costs [53]. Another alternative is to collect the outlet gaseous stream from the top of the nitrifying unit, containing N2O, and use it as oxidizer to burn the methane produced in the anaerobic sludge digester [54].
3.2. CH4 Removal
Biological technologies to remove CH4 from waste gaseous emissions, based on biofilter systems, have been studied since the early 1990s although they are not yet consolidated at industrial scale [55, 56]. Several biological processes are capable of oxidizing methane into CO2 (1 mol to 1 mol) which allow reducing the total GHG emissions in terms of CO2 equivalents since the warming factor of CO2 is lower than that of methane. In aerobic conditions CH4 is oxidized by methanotrophic bacteria in the presence of oxygen. Another option relies on the application of anaerobic conditions and exploitation of the activity of bacteria and archaea to oxidize CH4 using sulfate, nitrite, nitrate, Mn+4, or Fe+3 as electron acceptors [57]:As in the case of the N2O gas, the low solubility of CH4 implies the necessity to operate the biofilters at high residence time values (2–30 minutes) [58]. For these reasons, nowadays, the interest has moved to remove the CH4 directly from the liquid phase, before it is stripped to the atmosphere. To accomplish this removal the anaerobic methane oxidation is coupled to a denitrification process ((2)-(3)) which uses the methane as electron donor. In this case methane and both nitrite and nitrate are removed from wastewater [59]. Furthermore not only is the GHG removed but also the electron donor requirements for the denitrification processes diminish, reducing the costs of potential addition of external carbon source.
After the biological processes the methane remaining in the exhausted gaseous stream can be submitted to a postcombustion process [60].
3.3. CO2 Removal
For the CO2 gas removal extensive research has been carried out on the study of its capture by chemical or physical sorption and membrane separation processes from power cycles and industrial processes [61, 62]. However, the application of these technologies is generally associated with high capital and operating costs and the generation of waste streams. For these reasons, nowadays the cultivation of microalgae is being considered as an attractive alternative for CO2 gas sequestration. In WWTPs microalgae can be used for precombustion CO2 capture, as an economic way for biogas purification [63], or for postcombustion CO2 capture in order to maximize the microalgae production for their use as biofertilizer [64] or as substrate to increase biogas production [65].
4. Prevention
Most of the efforts to improve WWTPs performance are being focused on economic aspects related to energy consumption reduction, minimization of sludge production, and maximization of the amount and quality of biogas generated. To face these topics is important not only in terms of operational costs but also in terms of environmental impacts since it allows reducing direct and indirect GHG emissions [9, 66, 67].
Nowadays, only around 35–45% of the energy contained in the raw wastewater, as organic compounds, is converted into CH4 during anaerobic digestion of primary and secondary sludge. The remaining part is wasted under aerobic conditions due to the use of conventional nitrification and denitrification processes to remove nitrogen and organic matter simultaneously [68]. An alternative is to apply autotrophic processes to remove nitrogen, such as those based on the combination of the partial nitrification plus Anammox processes or the use of microalgae and even the application of biochemical processes. In this way both organic matter and nitrogen compounds can be removed in separated processes as the former is not required for denitrification but directed to the anaerobic digestion for biogas production. Thus oxygen requirements are minimized while methane production is maximized [69–71].
4.1. Application of Partial Nitritation and Anammox Processes to Remove Ammonia
In principle according to the metabolism of Anammox bacteria these are not directly involved in the production of N2O [72] and, therefore, the application of the Anammox process in the WWTPs instead of the conventional nitrification-denitrification processes is expected to reduce N2O emissions. However, in practice during the operation of full-scale Anammox reactors treating the reject water from sludge anaerobic digesters N2O emissions have been detected and accounted for up to 0.6% of the converted nitrogen [46]. This value is much higher than the percentages previously measured in lab-scale Anammox enriched reactors fed with synthetic media of 0.03–0.1% [73, 74]. For this reason the results at full scale can be attributed to the presence of nitrifying bacteria, entering the Anammox reactor in the stream coming from the previous partial nitrification unit [74].
Furthermore Kampschreur et al. [46] measured also N2O emissions in a partial nitritation full-scale reactor, attributed to denitrification carried out by ammonia-oxidizing bacteria, which corresponded to the 1.7% of the inlet nitrogen load [18]. From the previous results, obtained from full-scale systems, about 2.3% of the nitrogen load can be converted to N2O in nitritation-Anammox systems. In these conditions a two-stage partial nitritation-Anammox process appears as a nonsuitable alternative to reduce N2O emissions in WWTPs [66, 67].
Emitted percentages can be reduced down to 0.8–1.2% if a one-reactor nitritation-Anammox system is used [43, 75–77]. At full scale this configuration is the most applied one for the treatment of reject water from the sludge line [78]. For this reason, all the latest studies of the application at the main stream of the Anammox based processes have been carried out in single-stage systems. However, this kind of systems must be operated at low dissolved oxygen concentrations to maintain the balance between ammonia oxidation and Anammox rates and, therefore, the achieved nitrogen removal rates are relatively low [68]. However to operate at low dissolved oxygen levels promotes the development of nitrite-oxidizing bacteria and favours the oxidation of ammonia to nitrate instead of its desired conversion to N2 [78]. Due to this difficulty in avoiding the activity of the nitrite-oxidizing bacteria a change of concept has occurred and most of the research in course to implement the Anammox process at the main stream is focused on the two-stage reactor configuration. In this way operational strategies to avoid the development of nitrite-oxidizing bacteria, without affecting the Anammox bacteria, can be evaluated [68]. This might imply that the emissions of N2O would hamper the practical application of the partial nitritation-Anammox process, from the energy-saving and cost-effective point of view. Nevertheless, since the total amount of N2O emission from the partial nitrification unit is correlated to the nitrite concentration present, N2O emissions about 0.1% of the inlet nitrogen load are expected considering a nitritation unit operated for the treatment of the main stream (20–25 mg -N/L) [44]. Until now data of N2O emissions from Anammox systems in operation in the main stream conditions are not available in the literature, although if the entrance of nitrifying bacteria inside the Anammox system is minimized the expected emissions would be limited to 0.1% of the inlet nitrogen load and mainly due to the presence of heterotrophic denitrifying bacteria [45, 79]. This means that the partial nitritation-Anammox system treating the main stream would emit in total around 0.2% of the inlet nitrogen load as N2O.
Taking into account the fact that WWTPs with nitrogen removal carried out by nitrification-denitrification processes have a median emission factor of 0.01 kg N2O-N/kg [42], meaning that 0.6% of the inlet nitrogen is converted into N2O, the application of partial nitritation-Anammox processes in both sludge line (20% of the total nitrogen load with a conversion of 0.8% into N2O) and main stream (80% of the total nitrogen load with a conversion of 0.2% into N2O) will signify an important decrease of the N2O emissions.
4.2. CANDO Process
Recently, Scherson et al. [54] introduced a new N removal process called CANDO (Coupled Aerobic-anoxic Nitrous Decomposition Operation) which involves three steps: biological conversion of to ; biological or chemical partial anoxic reduction of to N2O; and () N2O conversion to N2 with energy recovery.
Then from steps () and () ammonia is converted to N2O, which is used in step () as a cooxidant for CH4 combustion or decomposed over a metal oxide catalyst to recover energy. The end product of the reaction is the N2. The innovation consists of utilizing N2O as a renewable energy source and reducing the requirements of organic matter which is consumed during denitrification. Combustion of CH4 with N2O releases roughly 30% more heat than using O2 ((6) and (7)) and mitigates the release of N2O to the atmosphere:Steps () and () of the CANDO process have been already applied at full scale while step () is still under study [54, 71, 80]. In these research works, two ways of producing nitrous oxide from nitrite are proposed: () abiotic reduction by Fe(II) with conversions over 90% and () partial heterotrophic denitrification (62% of converted to N2O).
4.3. Application of Microalgae
One of the main operating costs of conventional activated sludge systems, where nitrogen removal takes place, is associated with the large aeration requirements. Alternative systems like those based on microalgae are being considered as potential substitutes. In these systems nitrogen is removed via assimilation for biomass growth without oxygen consumption (8) [81], decreasing energy requirements. Moreover, a low N2O production is expected (0.005% kg N2O-N/kg ) if microalgae are used to remove nitrogen [82]When microalgae are applied for wastewater treatment cultivation the process is generally carried out in open raceway ponds, since the capital costs of these systems are lower than those of photobioreactors [83]. These microalgae ponds occupy large land areas which limits their use to rural areas. Another disadvantage of the microalgae application relies on the poor settling properties of the microalgae, which implies the use of coagulants and flocculants for separation from the treated wastewater [84]. For this reason, a novel approach consisting in the use of algal-bacterial cocultures has received significant attention in recent years as well. In this way the bacterial population would profit from the O2 produced by algae reducing the aeration requirements of treatment processes and at the same time greenhouse gas emissions are mitigated by the CO2 consumption during algal photosynthesis (Figure 3). According to (8), microalgae produce 17 kg O2/kg . Then, for typical urban wastewater, the amount of oxygen produced by microalgae would be higher than the O2 amount needed to remove organic matter by the activity of the heterotrophic biomass [85]. Therefore, both organic matter and nitrogen could be simultaneously removed in an open raceway pond without oxygen external supply. In addition, challenges associated with the high energy requirements for algal biomass harvesting might be overcome by means of the better settleability properties of the algal-bacterial coculture. Su et al. [86] demonstrated that an algal-bacterial coculture is able not only to achieve high COD and nutrient removal efficiencies but also to settle completely over 20 minutes. They also argued that the shares of algae and sludge inoculated in the pond have an influence on the nutrient removal efficiency and settleability, and they identify the ratio value of 1 : 5 (algae/sludge by weight) as that providing the biomass with the best settleability.
5. Case Studies
In order to quantify the potential reduction of GHG emissions due to the implementation of new processes in WWTPs (prevention strategy), five different configurations were evaluated for comparison purposes.
Case A. A conventional activated sludge system was used as a base case, performing the nitrification-denitrification process to remove both organic matter and nitrogen (Figure 4). The operational conditions of this system were SRT of 15 d, hydraulic retention time (HRT) of 12 h, internal recycle ratio of 3, external recycle ratio of 1, and aerobic volume percentage of 45%. In the primary settler, a particulate COD removal efficiency of 45% was assumed. Primary and secondary sludge are treated in an anaerobic digester (SRT: 30 d) in order to produce biogas, used in a cogeneration unit, and reduce the amount of sludge generated. The following cases take this one as a base case and only the descriptions of modifications applied to this configuration are included.
Case B. The activated sludge system was substituted by an aerobic reactor operated at a SRT of 2 d, to remove organic matter and to maximize the sludge generation, in order to increase methane production, followed by a partial nitritation and an Anammox reactor to remove nitrogen. In this case, the primary settler is intended for removing all the particulate COD to promote the anaerobic route of organic matter. Nitrogen is treated from the return sludge stream by a 1-stage partial nitritation-Anammox reactor.
Case C. A CANDO system comprising a partial nitrification and a partial denitrifying reactor is implemented in the sludge line. In this case, organic matter separated in the primary sludge is increased 20% since the nitrogen load applied to the activated sludge system is decreased in the same percentage. In the sludge line, an acidogenic reactor is used to provide organic matter to the partial denitrifying reactor. Produced N2O is used, instead of O2, to burn methane.
Case D. The activated sludge system was substituted by an aerobic reactor operated at a SRT of 2 d, to remove organic matter, followed by a high rate microalgae pond, operated at a HRT of 6 days, to remove nitrogen.
Case E. A high rate microalgae pond (SRT and HRT of 6 days) where the microalgae remove the nitrogen and provide the oxygen required for the heterotrophic bacteria to oxidize the organic matter was evaluated in substitution of the activated sludge system.
Mass and energy balances were performed by using Excel spreadsheets according to the methodology described in Campos et al. [39]. Finally, the emissions of CO2, CH4, and N2O were estimated considering the results obtained from the mass balances and the parameters given in Tables 1 and 2. From these values the global GHG emissions of each configuration expressed as kg CO2/m3 of wastewater treated were calculated taking into account the greenhouse gas production impact factors of 21 and 310 for CH4 and N2O, respectively.
Results obtained from the calculations indicate that systems using microalgae to remove nitrogen are the most suitable systems to reduce GHG emissions during wastewater treatment (Figure 5). This fact is mainly due to the high amount of CO2 captured by the microalgae together with the contribution of three other factors: () the improvement of the WWTP energy efficiency: in Case D, since the application of microalgae to remove nitrogen does not require the presence of organic matter, most of it can be converted into methane while, in Case E, oxygen generated by microalgae allows an important energy saving in terms of aeration; () the very low emissions of N2O observed in the high rate microalgae ponds; and () the additional biogas production due to the anaerobic digestion of the generated microalgae. When the partial nitritation and Anammox processes are used to remove ammonia, instead of conventional nitrification and denitrification processes, the WWTP energy efficiency is also improved which also causes a decrease of GHG emissions. However this decrease is considerably lower than that obtained by microalgae systems.
The WWTP configuration based on the application of the CANDO process (Case C) has associated GHG emissions higher than those of the conventional system. This can be attributed to the increase of N2O emissions due to the implementation of a partial nitrification reactor in the sludge line and the leakage of nitrous oxide expected in the exhaust gas. On the other hand, in this process organic matter is used to denitrify nitrite into N2O, decreasing methane production, while N2O generated can be used to oxidize only around 8% of methane. Those factors limit the energy efficiency improvement achieved by the application of CANDO process.
Nowadays, there are several technologies already implemented at full scale to perform partial nitrification-Anammox processes in the sludge line [87, 88]. However, in spite of the recent advances, their implementation at the main stream is still a challenge due to the strict control of operational conditions needed to maintain the stability of the partial nitrification process [89]. The use of microalgae systems to remove nitrogen from domestic wastewater is a feasible option when enough land is available since this kind of systems would require about ten times the area necessary for activated sludge systems [90]. The CANDO process can be used to improve energy efficiency of WWTPs but can only be applied to the sludge line. Moreover, the need of the development of a reliable technology for its implementation at full scale and its negative environmental impact make it not as attractive as the partial nitrification-Anammox and microalgae systems.
6. Conclusions
Minimization. N2O and CO2 emissions can be decreased by a good control of the operational conditions of the activated sludge system. CH4 emissions can be minimized if emissions from the different units of the sludge line are captured by hoods and burnt together with the biogas generated in the sludge anaerobic digester. N2O emissions will depend mainly on the operational conditions ( and O2 concentrations) of the reactor systems.
Treatment. Nowadays most of the technologies available to remove GHG are expensive or even not suitable to be applied to gaseous streams of the WWTPs. Biological systems treatment has low operating costs but their capital costs are high due to their size. The correct selection of the process to be installed in the plant will provide the best results as it is the case of the partial nitritation-Anammox process which is feasible in two units applied in the main stream of the plant but not for the treatment of the sludge line.
Prevention. The configuration of the next generation of WWTPs should maximize the anaerobic pathway for organic matter removal and the use of microalgae, if enough area is available, or partial nitritation-Anammox processes to remove ammonia.
Competing Interests
The authors declare that they have no competing interests.
This work was supported by FONDECYT 1150285 (Chile) and Postdoctoral FONDECYT 3140276 (Chile) and by the Spanish Government through FISHPOL (CTQ2014-55021-R) and GRANDSEA (CTM2014-55397-JIN) projects cofunded by FEDER. The authors A. Pedrouso, A. Val del Río, and A. Mosquera-Corral belong to the Galician Competitive Research Group GRC 2013-032, program cofunded by FEDER.
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text:
Breville Sous Chef BFP800CBXL (Cranberry Red) is a great food processor and if you are like me, I am sure you will find it versatile and convenient for all your food processing needs. My wife loves the food processor simply because it is powerful enough to accomplish her food preparation tasks within a short time without need to switch it on and off to allow it time to cool down.
My old food processor was a little bit noisy plus it could not work as fast as I wanted. This was a setback since I would waste a lot of time in food preparation and therefore opted to look for an affordable unit to replace the old one. After researching a number of food processors, Breville BFP800XL Sous Chef food processor stood out as the best. I have decided to share my experience and research findings with you since I believe this is a great food processor for any homeowner.
Variable 24-setting slicing discs
Having used a number of food processors, none of them could give us different sizes of slices for ingredients. This to me was a big disadvantage. I however found a solution in Breville Sous Chef food processor. The processor will definitely make work easier for you especially with its 24 disc settings which allows you to choose the thickness you need for your ingredients. In addition, this food processor also features a, S blade which is able to slice through tough pieces of ingredients with a lot of ease. It is easy to slice foods of all sizes and shapes using this slicer.
Powerful and strong motor
Breville Sous Chef (Cranberry Red) comes with a 1200 watt motor that is powerful enough to slice even the toughest foods in the kitchen. The motor is reliable enough such that the manufacturers have given it a 25 year warranty. This powerful motor works very fast thus ensuring that all the ingredients are perfectly sliced in the desired sizes and shapes.
16-cup capacity work bowl
The food processor has a work bowl with a capacity to hold 16 cups. The bowl comes with a lid which has a safety lock thus enhancing the safety of the processor throughout. If this lid is not securely locked, Breville Sous Chef will not run. It also has a mini processing bowl with a capacity of 2.5 cups thus making it easy for users to perform smaller tasks when necessary. These bowls combine very well with the extra large feed tube to make your work easier. There is no need for you to pre-cut your ingredients into smaller pieces before feeding them into the tube.
Features and specifications
- The Breville BFP800CBXL food processor (Cranberry Red) has 3 blades and 5 multi-function discs out of the box
- Breville Sous Chef food processor features a large and small food pusher which helps push huge and small ingredients through the feed tube. The small pusher also works as a measuring cup for ingredients whenever you need to add some into the bowl. The appliance won't run without the large food pusher or if it is not properly set but will run without the smaller pusher.
- It has an LCD display count-up/down auto timer. The timer helps in setting the time required for food processing.
- The food processor has an extra large feed chute which has a safety system. The feed chute makes it unnecessary to pre-cut large pieces of your ingredients before putting them in the food processor. On the other hand, the safety system prevents motor operation unless the bowl and food pushers are locked correctly in their position.
- Silicone seal to prevent fluid leakage when processing large amounts of liquid-based ingredients.
- Non-skid rubber feet for enhanced stability and safety.
Customer reviews and score rating
Breville Sous Chef is an extremely handy food processor and can knead, chop, dice and slice with precision saving you much time in the process.
By the time I wrote this review, the appliance had 277 reviews which had given the Breville Sous chef food processor a star rating of 4.7 out of the possible 5. Generally, reviews in Amazon are positive but also balanced with a few points of concern raised by some reviewers. One review went like this, "I was misled to thinking that the 'S' blade that came with the unit had two layers." However, the same customer added that, "The 'S' blade is fantastic. I can give a very fine chop in to just about anything in a few pulses." This to me shows that the customer had some expectation but not based on manufacturer's specifications and assurance.
I find it very easy to recommend Breville Sous Chef (Cranberry Red) all factors considered.
Breville bfp800xl sous chef food processor can perfectly handle all types of processing tasks whenever called upon. You should however avoid processing cheese products according to the manufacturer.

subset: commoncrawl


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Special Session: Astronomy Software Publishing: Community Roles and Services
10:00 am – 11:30 am
National Harbor 2
The Astrophysics Source Code Library (ASCL) and Astronomical Data Group at the Flatiron Institute have organized a Special Session at January's AAS meeting. The session, Astronomy Software Publishing: Community Roles and Services, will be moderated by Peter Teuben (University of Maryland).
The importance of software to astronomy research is well-established, and excellent arguments to reveal these computational methods to support the research record have been advanced and much discussed in recent years. But what avenues are open to software authors to publish their codes, and what roles and services exist in the community to support their efforts? This session answers these questions. It builds on previous AAS special sessions and brings together a panel of experts to present various avenues for publishing codes and the pros and cons of these avenues, the roles of authors, data editors, and publication indexers in software publication, the benefits of publication to authors and the discipline, and efforts of related community projects to improve aspects of software publication. After the presentations, the floor will be open for discussion and questions. The presenters and topics covered are:
Matteo Cantiello (Flatiron Institute), The Evolution of Software Publication in Astronomy
Chris Lintott (AAS Journals), Software papers and citation in the AAS Journals
Leslie J. Sage (Nature), Software policies and guidelines at Nature
Ramon Khanna (Springer), SpringerNature data and software policies for astrophysics journals
Arfon M. Smith (STScI/JOSS), Journal of Open Source Software (JOSS): Design and first-year review
Karen Collins (Center for Astrophysics), Lessons Learned through the Development and Publication of AstroImageJ
August Muench (AAS Journals), The roles of the AAS Journals' Data Editors
Alberto Accomazzi (NASA Astrophysics Data System), The role of the ADS in software discovery and citation
Alice Allen (ASCL/UMD), The Astrophysics Source Code Library: Supporting software publication and citation
And you, astro software authors and users, are as always important participants in the discussion. Please come with your questions, observations, and comments; I hope to see you there!


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Sailors and Navy civilians need to take precautionary measures to maintain a heightened cyber security posture. Here are several tips: (1) ensure that all your annual cyber security training is up to date; (2) stop and think before you open emails or click on hyperlinks. Verify the authenticity of the source; (3) log off your workstation at night, reboot on a weekly basis to ensure all security patches can be properly applied; (4) maintain awareness of your command's cyber security policies; and (5) open a dialogue with your Information Systems Security Manager (ISSM) and, when in doubt, ask questions. Sailors and civilians can voluntarily participate in any additional training offered through FedVTE, Navy Knowledge Online (NKO), or the Information Assurance Support Environment (IASE).
For more Navy news, visit the Military.com Navy section.


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Giselle Anguizola
Giselle Anguizola has dedicated her life to jazz era dances for twenty years. She has been an unmissable voice in the swing dance community as performer, instructor, competitor, event organizer, social dancer, judge, DJ, and singer/band leader - - and has recently devoted herself to combining vintage tap/jazz with singing as part of her performance. She's highly influenced by Cab Calloway and loves bringing the music to life. One of the top proponents of syncopated footwork, personal style, improvisation and communication - Giselle will breathe rhythmic life into any dance, class, or stage appearance.
Giselle "G", spends her days working with the New Orleans Swinging Gypsies and continues to spread her love for jazz culture across the globe.
Evita Arce
Known for her magical energy, high-flying aerials and dynamic movement, Evita Arce is a specialist in the Lindy Hop, The Charleston, and other Swing era dances. Evita performed the featured Lindy Hop role with partner, Michael Jagger, in the Broadway show SWING for the 2008 Japan tour, The Sacramento Music Circus, and the Benedum Theater in Pittsburgh. Evita's choreography and partnerwork have earned her 1st and 2nd place in numerous national contests. In October 2007 at the American Lindy Hop Championships she won 1st place in Blues and Cabaret. Evita was recognized for her solo-Charleston dancing with 1st and 2nd place standings. More recently she took 1st place in the Jazz dance competitions, both solo and partner (with partner Nathan Bugh), at ILHC 2012!
Learn more at https://michaelandevita.com/
Julie Brown
Julie's expressive dancing and joyful, playful connection are known throughout the country. With a background in performance and solo dance, she is best known for her solo blues, artistic choreography, and seamlessly integrating following with expression.
As a teacher… Julie presents material with a caring and often light-hearted tone. She carefully crafts her classes and continuously tailors her material to fit the crowd at hand. Julie teaches regularly in her hometown of Boston, and has taught workshops everywhere from California to London.
A hard-working competitor… Julie has also won many national competitions, including Enter the Blues 2013 Choreography Competition and Solo Blues, Mile High Blues 2012 Strictly and Jack & Jill, Enter the Blues 2012 Strictly and Choreography Competition, Emerald City Blues 2011 Strictly and Solo Cuttin, and many, many more.
Nathan Bugh
Nathan Bugh presents a unique, rhythmic style of jazz movement on stage, on screen, and in classrooms worldwide. As a national competitor, Nathan has taken 1st place in Lindy, Slow Dancing, Solo Charleston, Team, Jill&Jack, and Cabaret divisions. He is one of the most eminent solo-jazz contestants in the world, having won both the Ultimate Lindy Hop Showdown (2012) and International Lindy Hop Championships (2014). He is based in New York City, where he performs and teaches regularly, in affiliation with Syncopated City Dance Company, and Gaby Galore.
Learn more at http://www.nathanbugh.com/
Gaby Cook
Gaby is a national-award winning dancer who is praised for her dynamic style and choreographic ingenuity. In her 10 years+ of professional experience, she has appeared on stages around the world, and has garnered various film and television credits. She performs weekly at the famed "Cotton Club" in Harlem with the "Sophisticated Ladies" led by Dormeshia Sumbry Edwards. In addition, she is also lead choreographer for Gatsby Entertainment NYC, an entertainment production house, specializing in Great Gatsby theme.
With a solid foundation of studio dance training, she has developed a unique style in lindy hop. She blends the raw, athletic power of lindy hop, with the grace and refinement of the movie musical-era. She brings great care to lines, shapes and balance in her personal performance, as well as her choreographic work. In New York, she is a cast member in the classroom, she shares her knowledge of the dance with a cheerful disposition, and clear straight-forward instruction. She is passionate about lindy hop traditions and works to share the joy of swing with new audiences.
Mia Halloran (Goldsmith)
Mia Goldsmith, with her incredible string of competition wins and international teaching and performing gigs, excels in dances from the Jazz Age and is known as one of the best Balboa Swing dancers in the world. Based in New Orleans, she is constantly inspired by the live music surrounding her. While she no doubt loves traveling the world, she's most at home in a small neighborhood bar with a packed floor, getting down to that rhythm only New Orleans has to offer.
Her unique approach to teaching is full of energy and creativity, bringing a passionate and motivated air to the classroom. She is known for her highly impressive footwork, elegance, improvisation, and individual approach to the dance. Above all else, she is driven by her desire to create with both partner and band on the social floor.
Hillary-Marie is one of the accomplished tap dance artist and producers in America. Hillary-Marie's dancing has been described as 'like feathers with steel bones' due to her combination of strength and grace. She has also been called 'a brilliant artist'. A native of New Jersey currently based in NYC, Hillary-Marie has been recognized by and featured in Dance Studio Life Magazine, Dance Spirit Magazine and Dance Teacher Magazine. She has performed on The Colbert Report and has appeared at the Smithsonian, Apollo Theater, Jazz at Lincoln Center, Highline Ballroom, The Copacabana, NJ STATE Theater, NJPAC, SOPAC, and Symphony Space among many other prestigious venues along the American east coast.
Learn more at http://www.hillary-marie.com/
Michael Jagger
Michael began dancing in college in Jacksonville, Fl., and once he had a taste of swing and transferred back home to Colorado he began taking Lindy Hop lessons from the performance troupe, The Jumpin' JiveCats, and eventually joined the troupe as teacher and performer. In 2003, Michael serendipitously moved to Los Angeles to join the dance company run by Londoners Ryan Francois and Jenny Thomas, who had relocated to LA for a time. At that time he met his future, and current, partner Evita Arce. Neither could have imagined what adventures were in store for them. Both Michael and Evita moved to New York City in 2005. They currently perform and teach internationally and continue to train with Ryan and Jenny when either jumps across the pond.
Mike Legenthal
Mike's true loves in life are teaching, dancing, following, and music. There's no order, because for her, these things are intrinsically linked. In addition to national events like Lindy Focus and Enter the Blues, Mike has taught at countless regional events in Lindy, Blues, and Balboa, as well as traveling all over the country to teach and perform. She performed in an all-girls Charleston troupe at Camp Jitterbug's Jump Session Show in 2007, and in the all-girl blues troupe, the Hoodoo Ladies, at events from DC to BluesShout in St. Louis. Additionally, she has taught at events ranging from one-month artists residencies to international training camps.
Mike combines an intuitive understanding of connection with an analytical speaking style to give her students technique, but also strives to challenge and inspire her students to push themselves further into the music. She aims to help leaders create artistic compositions that are clearly led; she wants follows to have the ability to be a completely literal follow, and the inspiration and freedom to be an imaginative and dynamic contributor. In the classroom or on the social floor, she seeks a connection that involves active communication from both partners, to make a dance together.
Shesha Marvin
Shesha Marvin is a dance aficionado specializing in Jitterbug dances. He is an active competitor, teacher, and performer, appearing around the world at swing dance events and in Hollywood productions such as Dancing with the Stars, music videos, and TV spots. Additionally, he is the owner of ATOMIC Ballroom in Irvine, CA and organizer of the 24 Hour Cancer Dance-a-thon, Inspiration Weekend, and OC Lindy Exchange.
Dan Legenthal
Dan lives in Boston, MA, working on as many vernacular jazz and blues dances as he can find the time for. His passion extends to both the social floor and competition. Dan can be found teaching at regional events like LaB Love (Philadelphia, USA), and at international events like BluesSHOUT! (USA), Studio Hop Summer Camp (France), and Korea Blues Camp (South Korea).
Before becoming obsessed with jazz and blues, Dan studied Classical Guitar at Carnegie Mellon University's conservatory program. There, he learned how to practice effectively, and was exposed to pedagogy that bridges the gap between making music and moving to it, including Dalcroze Eurhythmics (not to be confused with the totally awesome British new wave group "Eurythmics"). Dan uses those techniques in classroom to create the right balance between thinking and doing, pushing students to understand important underlying principles by developing and testing their own ideas.
Andy Reid
Andy Reid is one of the most well known and influential swing dancers out there. Since he started dancing in the late nineties, Andy has left an indelible mark on the dance scene. Andy's style is a balance of the refined and the eccentric. His proficiency with rhythm and partnering make his dancing rich and inspiring to watch and experience. While Andy specializes in and is passionate about the original styles of Lindy Hop, his dancing is a mix of many influences, is always inventive, and is never encumbered by labels.
Learn more at http://www.andyandnina.com/