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Potential of natural technologies for decentralised wastewater management in India 1
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M. Starkl *, P. Amerasinghe , L. Essl , M. Jampani , D. Kumar and S. R. Asolekar
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1 Centre for Environmental Management and Decision Support, Vienna, Austria 2 International Water Management Institute, Regional office, Hyderabad, Andhra Pradesh, India 3 Centre for Environmental Science & Engineering, Indian Institute of Technology Bombay, Mumbai, India
Abstract
High population growth, increasing urbanization and rapid economic development are exerting pressure on the already scarce water resources in India. Untreated wastewater from human settlements reaching natural waterways is very common contributing to environmental pollution, which directly affects the availability of fresh water for human consumption. Therefore, treatment and reuse of wastewater can play an important role in addressing some of the urban water challenges in India. Conventional treatment plants have many challenges, therefore, natural treatment systems are viewed as a cost-effective alternative, which are more suitable in the Indian context. For example, they are not reliant on electricity, easier to maintain, can be part of small decentralised systems and work well in tropical climates. This study presents a rapid sustainability assessment and a review of the potential of natural treatment systems in India. The preliminary results show that the natural treatment systems have a high potential for wastewater treatment. However, there are still gaps in knowledge related to aspects that hinder the sustainable functioning of these treatment systems. Keywords
Duckweed ponds, constructed wetlands, rapid sustainability assessment, waste stabilization ponds, natural treatment ponds
Introduction The high population growth and rapid economic development are exerting pressure on the already scarce water resources in India. Untreated wastewater from human settlements causes high levels of environmental pollution, and contaminates the Indian rivers which provide water to many centralised water supply systems. Natural treatment systems (NTS) are based on natural processes that use attenuation and buffering capacity of natural soil-aquifer and plant-root systems, and the process of contaminant removal is not aided by the input of significant amounts of energy and/or chemicals (Sharma and Amy 2010). NTSs can be classified as soil-based and aquatic treatment systems. Examples for soil-based systems are, subsurface flow constructed wetlands (SFCW), soil aquifer treatment (SAT) systems or planted filters (PF). Aquatic systems are duckweed (DWP) or waste stabilization ponds (WSP). They can be used as secondary or tertiary treatment systems and in combination with conventional and other NTSs (hybrids) or solely based on the influent water quality and intended reuse of the treated water. It has been reported that a combination of different treatment technologies allows for improved water quality of the effluent (Alvarez et al., 2008, Mbuligwe, 2004, Kaseva, 2004). Another classification distinguishes between [I] intrinsic and [II] engineered systems (Chaturvedi and Asolekar, 2009). The intrinsic natural systems are typically the so-called natural water-ways and aquatic systems which can be further subdivided into two divisions, namely: self-supporting and stressed systems. A self-supporting system typically allows degradation of pollution without altering its own mechanisms and processes; for example, 1
rivers and lakes polishing traces of biodegradable organic matter or treated sewage with the help of plants and microorganisms present in the system. It must be noted that the natural systems also concurrently process other biodegradable loads of pollution reaching the system via other natural biogeochemical routes, including the routine humification of natural organic matter. The stressed natural systems, however, are usually characterized by the inability to cope with and degrade rather large amounts of contaminants reaching the system (for example, rivers and lakes receiving large loads of sewage and wastewaters from urban or peri-urban communities). Natural wetlands a type of NTS, and may serve as buffer for storm water runoff. They may also act as a biofilter as well as trap sediment and remove pollutants including heavy metals from the contaminated surface runoff. Wetlands are considered delicate eco-systems because normally they are habitats for native and migratory wildlife. A literature review carried out across India revealed the presence of natural wastewater treatment systems (NWTS), in the form of WSPs, SFCWs, SATs and PFs.Their evaluation reports comprised primarily of technical details and lacked any descriptions of non-technical aspects that could affect the performance of the systems. In an attempt to bridge this knowledge gap, the present study assessed the influence of non-technical aspects (economic, social, institutional and health) in four selected case studies (Agra, Mathura I and II, and Hyderabad).
Experiences in India It is well known that the engineered natural wastewater treatment systems including river banks, wet-zones and their modified versions such as constructed wetlands, waste stabilization ponds, sewage fed aquaculture ponds, duckweed ponds or algal bacterial systems are known to render quite effective environmental services by treating biodegradable carbonaceous matter and by separating suspended loads of particulates. However, it should be noted that, among these wastewater treatment systems not all are particularly effective in removing nitrogen and phosphorus. In spite of their limitations, Natural Treatment Systems (NTSs) have attracted attention of environmental engineers and scientists by the virtue their abilities of treating wastewater at phenomenally low operation and maintenance (O&M) costs (Arceivala and Asolekar, 2006). They have been favourably looked upon in the third world countries, especially because of their low power requirement. In the light of shortage of water in several parts of India; communities are searching for the alternatives that are less power intensive and less expensive to provide some kind of primary and secondary treatment. The NTSs typically fill the gap in the sense that they need relatively low O&M costs and far low power to run them when compared with conventional primary, secondary treatment alternatives - especially such as activated sludge process, trickling filter or extended aeration system. Experiences of application of a variety of natural treatment systems in India have been highlighted by Arceivala and Asolekar (2006), Chaturvedi and Asolekar (2009) and Starkl et al. (2010). Soil aquifer treatment systems and constructed/Natural wetlands have particularly demonstrated more applicability in the context of developing economies such as India. The constructed wetlands can be effectively combined with advanced tertiary treatment alternatives and the resulting high quality treated effluent can be gainfully recycled into production and sanitation applications. The constructed wetlands are most prone to engineering adaptation and modular application. Table 1 gives an overview of the case studies that were already reported in literature.
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Table 1 Review on natural treatment systems in India.
Wastewater treatment technology Waste stabilization ponds Constructed wetlands
Hyacinth and duckweed ponds Algal and fish ponds Soil aquifer treatment Planted filters Wastewater irrigation
References CPCB (2005), Punjab State Council for Science & Technology; Arceivala and Asolekar (2006), Chaturvedi and Asolekar (2009) Juwarkar et al. (1995), Arceivala and Asolekar (2006), Chaturvedi and Asolekar (2009), Fardin et al. (2010), Oekotec, Punjab State Council for Science & Technology Punjab State Council for Science & Technology, SANDEC (1999); Arceivala and Asolekar (2006), Chaturvedi and Asolekar (2009) Arceivala and Asolekar (2006), Chaturvedi and Asolekar (2009) Nema et al. (2001) Wafler et al. (2006), The Hindu (16th September 2011) Arceivala and Asolekar (2006)
WSPs were the most popular treatment technology covering over 72% of the treatment capacity in Class II towns with 100,000 inhabitants (CPCB, 2005). However, only a few performance evaluation reports were available for assessment. On a more positive note, the technical evaluation showed that WSPs are capable of reaching the Indian discharge standards, but algae growth and power cuts (affecting aeration) appeared to impact the performance, in some instances. The location of constructed wetlands and duckweed ponds (Punjab) is documented; however, the evidence for systematic monitoring of performance over time was sparse. Several reports confirm that the technical performance of these systems is good, but institutional governance issues that dealt with operation and maintenance were key for sustainability (CPCB, 2005) Soil aquifer treatment (SAT) technology has only been piloted around 10 years ago, and the performance evaluation results showed the SAT systems were more efficient and economical than conventional wastewater treatment systems that used the up-flow anaerobic sludge blanket (UASB) system, activated sludge process or trickling filters. Planted filters are another type of NWTS, that is becoming popular. They consist of a soil bed, with canna (Canna indica) plants, and used primarily for greywater treatment in residential complexes or institutional buildings. The treated greywater can then be reused for flushing and gardening purposes. No performance evaluation results are available. It was evident from the survey that technical performance evaluation took priority over assessment of social, institutional and health aspects, indicating a gap in knowledge on how the latter would impact the overall performance.
Knowledge gaps As discussed earlier, a few of the case studies described a holistic view on sustainability of the NTSs, and discussed the importance of incorporating other possible issues that could impact performance. These were social, health, institutional and economic issues that could influence the performance cycle. It was clear that many NTS reviews did not consider these issues. Therefore, here we attempted to elaborate some of the important issues that will impact the long-time sustainability of natural treatment systems; 1. Health and environmental aspects of reuse of treated wastewater: Waste Stabilization Ponds (WSPs) and constructed wetlands (CWs) have to be tested on their ability to 3
remove coliforms from the influent wastewater. NTSs are able to remove coliform bacteria up to 2 to 3 log orders. The performance of WSP may vary seasonally as well as owing to overloading and siltation and therefore the effluent may contain a high concentration of coliform bacteria. Since the Central Pollution Control Board (2008) has published recommendations for coliform concentrations for a a variety of reuse purposes, there is increasing emphasis on this aspect in the recent past. The evaluation also suggests that there may be imminent risk to the children who play on the lawns where treated sewage might have been sprinkled for irrigation (Starkl et al., 2010). For all other systems, too, there is no or little information available about the health risks associated with the reuse of treated sewage. 2. Institutional aspects: Evaluation reports dealing with institutional arrangements were not found during this survey. In the case of the WSPs, when compliance was poor, it was said to be due to weak operation and maintenance (O&M) of the plant. However, no systematic studies have been carried out to confirm these observations/perceptions. Institutional aspects, in particular the organization of operation and maintenance as well as monitoring and control are crucial for the successful functioning of any treatment system and these aspects should be documented for performance evaluation of the NWTS that are operating in India. 3. Economic aspects: documentation of cost-benefit analysis and cost recovery processes for NTSs was also poor, despite the importance of these aspects for long term sustainability. 4. Social aspects: the acceptance of the use of treated wastewater from natural treatment systems has not been assessed in a systematic way so far. Other aspects, such as user participation and user acceptance are other crucial issues to ensure long term sustainability of NWTS. Overall, the current literature survey, yielded limited information.
Case studies In order to further examine the non-technical aspects, case studies were identified based on the following criteria: • Suitability to study the identified knowledge gaps (social, health, institutions, economics and governance) • Preference of wastewater treatment technologies that aim at reuse of water • Implementation under “real-life conditions”: the case studies shall not be located on a university campus or be pilot plants as institutional and social aspects are hardly challenged • The system has to be operational for at least one year in order to evaluate its performance under real-life conditions, • Accessibility: The systems shall be located in an area that is not too difficult to access This paper describes four case studies (Table 2). Additional case studies, in particular for other types of NWTS, will be added at a later stage. Table 2: Selected case studies
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Location Mathura
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Mathura
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Agra
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Hyderabad
Technology Waste Stabilization Pond I Waste Stabilization Pond II Decentralised Wastewater Treatment (DEWAT) system Polishing pond (posttreatment)
Capacity 13,59 million litres per day (MLD) 14,5 MLD
State/Location Uttar Pradesh /50 km North-West of Agra
50000 litres per day
Uttar Pradesh/200 km south of Delhi
30 MLD (currently only 15 MLD used)
Andhra Pradesh/15 km from the city of Hyderabad
Methodology A rapid assessment methodology that was validated during previous studies in South Africa and India was used to collect the data (Starkl et al., 2010a, Starkl et al., 2012). It is a qualitative methodology based on expert visits and initial interviews with targeted stakeholders and users. The assessment aims at getting a quick qualitative and quantitative picture of the overall performance of the investigated system, and does not require a statistically representative user survey. The method employs the technique of conducting indepth interviews with a small number of users to collect the information required, which enables the collection of details of the systems that might not be available in literature. It uses a standardised questionnaire that includes the following topics: general information, financial details, downstream use of treated wastewater, health and environmental risks, institutional and operational aspects, social aspects, problems and reasons for success, opinion of users on treated wastewater. The questionnaire first explored if the intended benefits of the technologies have been fulfilled, which is the improvement of the provision of, and access to, safe water. Other additional benefits expected are economic benefits from fish cultivation, reuse of water in agriculture or the improvement of environmental conditions. Then it attempted to examine if there were risks involved in not achieving the intended benefits, for the present and the future. Based on this assessment a case was classified as successful and unsuccessful. Following the qualitative risk assessment, underlying causes were analyzed to understand the reasons behind good or marginal performance systems. We envisage the collection of a variety of technical and non-technical issues linked to this assessment which included, technical, governance, operations, maintenance, design, organisational issues that may lead to not achieving the intended benefits. Most importantly we hope that social and health issues may be uncovered, which may not be part of the current reporting agenda for the system.
Results and discussion Case study 1: Waste stabilization pond – Mathura I
This waste stabilisation pond is in the city of Mathura, located close to the railway lines and a low-income community, which existed before the establishment of the sewage treatment plant. Domestic wastewater (13.59 MLD) from the city of Mathura is conveyed to this treatment plant, but the community living close to it is not connected to the sewer network. It The waste stabilisation pond in Mathura was constructed and commissioned by the National River Conservation Directorate (NRCD) operated and maintained by Mathura Jal Board (Water Board).. The intended benefit of the treatment plant is the treatment of wastewater. Fig. 1 shows a schematic flow chart of the NWTS. The plant is run in two alternate cycles using the double set of ponds. However, at present only one set of chambers is functioning and the other is being dried out for repairs. 5
. Sewage
Screen chamber
Anaerobic pond
Facultative pond I
Facultative pond II
Maturation pond
Anaerobic pond
Facultative pond I
Facultative pond II
Maturation pond
Grit chamber
Effluent discharged to stream
Figure 1: Schematic flow chart of waste stabilization pond Mathura I
Economic aspects: The operation and maintenance of the WSP has been outsourced at a cost of 4 lakh/year. The two operators received a salary of 32,000 Indian Rupees (INR)/year each. Currently, there is no revenue from selling any by-products. The treated water is discharged to the nearby stream and sludge is stacked around the premises of the treatment plant. The facultative anaerobic ponds (FAP) and the two maturation ponds (MP) have been successfully used for rearing fish. It provided a good protein source for communities who engaged in the practice. However, since last year, fish rearing has been abandoned, after a community member fell sick eating the fish from the ponds. Institutional aspects: The main institutions involved are the Mathura Jal Board, the Central Pollution Control Board (CPCB) and a private company that is contracted for one year by the the Mathura Jal Board. The CPCB is conducting monitoring of the quality of the effluent and the monitoring wells. The actual operation and maintenance is handled by the private company, with the support of two operators. One technical supervisor, a junior engineer of the Mathura Jal Board is responsible for attending to the technical problems. He infact supervises all wastewater treatment plants in Mathura.The treatment performance is monitored every month by the Mathura Jal Board and the CPCB, but the information on the performance is not available in the public. The WSP operators have been selected from the local community. The operators were responsible for cleaning the rack and guiding the plant, and did not receive a specific training, The salary was reported as 32,000 INR/year and free housing was provided by the company close to the plant. The site visit showed that the institutional arrangements worked well as technical problems such as infiltrating wastewater were being tackled immediately. Health and environmental risks: Water is not reused, therefore, no apparent health risks have been reported so far. However, when the cement lining in one of the ponds disintegrated, the partially treated wastewater seeped into the ground water contaminating the water in one of the bore wells close to ponds. People consuming the water fell sick, and the pond set that was faulty was emptied for repairs. Social aspects: Five persons (four people from the local community and one operator) were interviewed. They have reported about the problems with the contaminated groundwater and the contaminated fish (see above). The only current benefit for the community is that two local people are employed as operators. When WSP became a source of contamination of ground water, there was resistance against the WSPs, as the system was not even serving their community by collecting the sewage. In summary, overall, this case study did not fulfill the intended benefits, and caused problems to the community living close to it, despite the fact that quick action was taken when the problems arose.
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Case study 2: Waste stabilization pond – Mathura II
This WSP was built ~10 years ago in Mathura by the local water board. It has a capacity of 14.5 MLD and treats domestic wastewater. The structure is the same as for Mathura I, but the intended benefit is not only treatment according to norms, but reuse of treated wastewater in agriculture. Anaerobic pond Sewage
Screen chamber
Facultative pond I
Facultative pond II
Maturation pond Effluent used in agriculture
Grit chamber Anaerobic pond
Facultative pond I
Facultative pond II
Maturation pond
Figure 2: Schematic flow chart of waste stabilization pond Mathura I
Although the system was running normally, its external environment was not maintained well. Plastic wastes were floating in the anaerobic pond and the surrounding of the pretreatment unit was dirty. The treated water was being reused in agriculture and farmers prefered this water over groundwater, due to the presence of nutrients. Economic aspects The municipality pays 7 lakh INR/year to the private company for operation and maintenance. The land next to the WSP is leased to local farmers who can also use the treated water. The treated wastewater was reused in agriculture by the nearby farmers. In two groups of interviews and one individual interview, the perception of the farmers was captured (see social aspects). The results show that the annual benefit of using wastewater is 8500 INR per year (see Table 1). Institutional aspects The operation of the treatment plant is outsourced to a private company with a contract duration of one year. Three persons are employed: two as non-technical operators and one technical operator. The salary of the operators was reported as 32,000 INR/year. The institutional arrangements are the same as in Mathura I. Health and environmental risks The reuse of treated wastewater in agriculture involves a risk for farmers and consumers, if contaminant removal is not tested. The main agricultural crops irrigated are eggplants, cucumber, pumpkin and cereals. The farmers are aware of the treatment process (anaerobic digestion) of the WSP and understand that this water is not fit for domestic use. The use of treated wastewater for the vegetables such as cucumbers that are eaten raw, can pose a risk to consumers. An Italian study (Cirelli et al., 2010) investigated the quality of tomatoes and eggplants irrigated with treated wastewater from a conventional treatment plant which received additional tertiary treatment in a constructed wetland. The results showed that the microbiological quality of the products was at levels acceptable for human consumption. Even though the treatment system is more advanced than in the Indian case, microbial contamination was observed in products that came directly into contact with the irrigated soil. Social aspects Three groups of farmers (groups 1: seven male farmers, group 2: family of six persons, mainly women, group 3: three farmers, who used groundwater and wastewater for irrigation) were interviewed about their opinion on the quality of the water they are using for irrigation. The farmers reported that the price of leasing the plots included the use of wastewater and was varied according to soil fertility and cost between 16.000-48.000 INR/year per acre. The treated wastewater was used year round. In total 100 acres are planted with the water of this wastewater treatment plant and they would like to use more water, but the distribution pipes are a limiting factor. 7
If they had the choice between groundwater and treated wastewater for irrigation they would choose the treated wastewater. The groundwater quality was good, but the groundwater has two disadvantages: it is expensive and it contains no nutrients. Chemical fertilizer was not used because the nutrients in the wastewater were adequate to have three crop cycles per year. Before they used the wastewater they applied chemical fertiliser with the groundwater irrigation. The annual economic benefit for farmers were 8500 INR per year as given in Table 1. Table 1: Economic benefits of wastewater use in agriculture, Mathura I WSP
Costs 1 bag of urea (50 kg) 1 bag of diammonium phosphate DAP (50 kg) Irrigation with groundwater, 1 cycle
INR 500 1200 600-800/per acre (average 700)
Annual financial input Fertilizer (2 bags ures, 1 bag DAP) Groundwater, 9 cycles Total
2200 6300 8500
Case study 3: Decentralised wastewater treatment (DEWATS) in Agra
The purpose of the treatment plant in Agra was to demonstrate the feasibility of a DEWATS system for the treatment of domestic wastewater in the peri-urban areas of Kuchhpura, Agra. The system consisted of a pre-treatment unit, a baffled septic tank, a baffled filter reactor and planted reed beds. Sewage
Screen chamber
Filter chamber
Baffled septic tank
Baffled filter reactor
Reed bed
Effluent to drain
Figure 3: Schematic flow chart of decentralised wastewater treatment system
The case study appears to be a successful case. The feasibility study demonstrated that a bigger treatment plant can be built with the experience of the pilot. Plans for a bigger system has already started. Apart from the treatment of domestic wastewater, another intended benefit was to improve the quality of the environment of the poor families in Kuchhpura. Economic aspects The investment costs were 10-11 lakh INR. An interesting aspect is the cost recovery: The operation and maintenance costs are recovered with the revenues from the “Mughal Heritage Trail”, which was initiated by the same NGO that implemented the WWTP (see institutional aspects). The revenues from the trail are sufficient to pay the salary of five guides on the trail and two operators in the treatment plant (see Table 2). Table 2: Costs for operation and maintenance of DEWATS, Agra Number of visitors per year Revenues per visitor (INR) Annual revenues from Mughal Heritage Trail 700IR/person * 450 visitors per year (INR/year)
450 700
Costs per operator/tour guide: 12 x 3500 INR/year 5 guides (INR/year) 2 operators (INR/year Total (INR)
42.000 210.000 84.000 294.000
315.000
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Health and environmental risks There are no health risks reported with this system as treated water is not reused. The environmental situation has improved a lot with the construction of this scheme (NIUA 2011). Before the system was implemented this was an open wastewater drainage and people had difficulties in crossing it. The cleaning of the grit chamber which is located under the pavement can be a risk as the systems are difficult to access. Institutional aspects The treatment system was designed and constructed on the Kachhpura drain by the Centre for Urban and Regional Excellence (CURE) in partnership with the Agra Nagar Nigam (ANN), USAID FIRE (D), Cities Alliance and financial assistance from Water Trust, United Kingdom and London Metropolitanm University. Two operators from the community are operating the treatment plant. They were trained and in case of problems, the implementing NGO (CURE) can be contacted. The main task is cleaning of the rack, all other task e.g. cleaning of filter material, removing of solids from grit chamber are done when necessary. The operators receive a salary of 3500 INR /month each. Every three months, the effluent quality is monitored by the local NGO. The institutional arrangement works well as in case of problems the local NGO provides support to the operators. In March 2012 the system was blocked and the operators had to remove the filter material, wash it manually and put it back to the system. Social aspects Community participation was an integral part of implementation and the community is also involved in the operation of the treatment plants (NIUA 2011). The pretreatment unit is covered by the pavement and can be used as gathering place or as playground for children. Case study 4: Upflow anaerobic sludge blanket (UASB) with polishing pond in Hyderabad
In this case study, the natural treatment system is a component of conventional treatment system. It serves as a post-treatment unit to improve the quality of the effluent, before it is discharged. The assessment was made for the whole treatment plant as it is not possible to evaluate the functioning of the pond without considering the entire treatment plant. The wastewater treatment plant was constructed in 2009 at Nallacheravu in Hyderabad. Its design capacity is for treatment of 30 MLD. Currently it receives around 15 MLD and should receive the full volume, once the network coverage is completed. After passing the pretreatment unit consisting of screens and grit chambers, wastewater enters four upflow anaerobic sludge blankets (UASB) reactors, then an aerated pond and finally a polishing pond. The effluent is chlorinated.
Sewage
Screen chamber
Grit chamber
UASB I & II UASB III & IV
Aerated pond
Polishing pond
Disinfection unit
Effluent to stream
Figure 4: Schematic flow chart of UASB treatment system
The intended benefit is treatment of wastewater according to the Indian norms for stream disposal. An additional benefit is the improvement of the environmental conditions in the sourrounding area. The system is working well and fulfills its intended benefit.There are no problems with the load and there is still capacity to connect more people. Clogging is happening from time to time, because of rough debris, especially plastics. Since the law against use of plastics 9
(APPCB, 1998) was implemented the less low density plastics reach the STP. In terms of risks, the power cuts and rapid turn over of technical staff can have an impact. Health and environmental risks Within the operating system, health risks have not been reported so far, and the treated water from the system is discharged to a storm water stream nearby. The water in the stream which is polluted gets diluted beyond the point of discharge, and the water is being used for many purposes, including agriculture, which is mostly in the peri-urban regions close to the city. Prior to the installation of the Nallacharuvu STP at Uppal, a nearby lake (Nallacheruvu) used to receive untreated overflow of sewage water. After the installation/upgrading of four new STPs, this lake has not been used for discharges, and has been part of a lake restoration programme. The environment around the lake has improved, with many water hyacinth plants and less odour. A potential threat is the use of the bypass to release the untreated wastewater during power cuts. This will contribute to an increase in the pollution loads in the adjacent waterways. Institutional aspects A private company is contracted for operation and maintenance. At present, 19 people of the company and 2 (one full time, one part time) from the municipality are working in the treatment plant. Total man-power is not sufficient to cover all the activities, especially, for sludge drying, which requires emptying and drying under natural conditions. The private company is contracted for three years, the contract is now expiring and a new contract is tendered. Attempts will be made to retain current operators as they are already well trained and know how to operate the treatmen plant. The operators are trained at the ITI (industrial training institute) after their secondary education (10th grade). The standards (and even more parameters) are checked daily for inlet, UASB effluent, facultative lagoon effluent and final outlet effluent for pH, temperature, BOD, COD, TSS, Fecal coliforms (FC) in a laboratory within the treatment plant. Also the volume entering the treatment plant is monitored. The institutional arrangements are well coordinated at this plant and the discharge standards meet the criteria set by the CPCB (Table 3). The performance was tested in an external lab as the internal sampling results were not provided by the operating company. Table 3: Performance of treatment plant (May 2011, one time testing, external lab)
pH DO mg/l Nitrate mg/l Phosphate mg/l Sulphates mg/l Total dissolved solids mg/l COD mg/l BOD for 5 days at 20o C mg/l
Water before treatment 7.40 0.56 56.5 38.1 212 853 246 147
quality Water quality after post treatment 7.82 1.01 6.0 13.1 98 797 37 22
Economic aspects The cost for installation of the STP system was15 crores (100 lakhs) and an annual operation and maintenance costs of 6,75 lakh/year incur, of which 2,25 lakhs are personnel and 10
maintenance costs, and 4,5 lakhs are for electricity. The costs for post-treatment activities are not known; the amount of chlorine used is at 2 mg/l. The costs are covered by the Hyderabad Municipal Water Supply and Sewerage Board (HMWSSB). A fee is levied for sewage treatment which amounts to 30% of the water bill (at present it is a flat rate of INR 212/HH/month). While there are opportunities for revenue generation from by-products (sludge, treated water, biogas), no gainful economic benefits are reported. The reasons for these are, the amount of wastewater received at present is not sufficient for economical production of biogas; further, the generator that has been installed is a duel fuel generator, which costs more to operate than the energy that can be harnessed from the plant. At present, there is no market for sludge. The downstream farmers feel that the water carries adequate nutrients, and therefore additional supplements are not required (according to the staff at STP). The sludge is dried in the premises, and used for gardening within the site. Social aspects The effluent is not used for irrigation. One farmer cultivating downstream of the STP vegetables (e.g. spinach, amaranth, tomatoes) was satisfied with the quality of water she received even though the quality of the water is worse than the quality of effluent. The farmers were tenant farmers that paid INR 1200/0.5 acre for leasing the land, which included the water supply as well.
Discussion and conclusion This study showed that there is a wide variety of natural wastewater treatment systems present in India, functioning at different performance levels. However, not all the systems had adequate information in the public domain, and therefore, site visits had to be made, to collect the relevant information. Real-time challenges and research needs were highlighted by the key informants such as the managers, operators and communities that were living close to the NTSs. It was clear that municipalities were outsourcing the operation and management of the systems while keeping the role of overall management under their jurisdiction. This method appeared to offer a better service to the public than before, and had the opportunity to revise the O&M system, every 1-3 years, through a tender process. The design capacities and level of sophistication of the systems varied, and appeared to be based on the catchment area and need, as well as the newer technologies that are available for pre-wastewater treatment. The current assessment brought out the following results: Institutional and organisational issues are considered to be of high importance, similar to studies reported from constructed wetlands in Mexico (Starkl et al., 2010b) and Thailand (Brix, 2010). That it should be considered during the planning phase, for effective management has been clearly demonstrated. Except in the Agra and Mathura case II, economic benefits from by-products of treatment was not visible and or difficult to assess during the site visits. Multiple benefits of by-products of natural treatment plants, has been demonstrated elsewhere, especially for floriculture and irrigation (Belmont et al.2004). In India, where wastewater was used for fish farming and agriculture, they recognized the economic value (savings on groundwater pumping and chemical fertilizer). However, potential risks for the consumers of vegetables irrigated with the effluent, need to be further investigated. Following the multi barrier approach of the WHO, it is always advisable to take measures to reduce contamination even at household level, by washing and disinfecting vegetables before consumption.
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In the study on the application of constructed wetlands in Latin America Gauss (2008), it was found that technical assistance is required for community managed systems which was also confirmed in this study. The DEWAT system in Agra worked well due to continous support from a local NGO. The decentralized NTSs can be suitable for countries where cities cannot keep pace with rapid population growth. Such systems require less maintenance and energy input than conventional treatment systems (Nogueira et al. 2007). The important aspect in all of the cases studied was that the system required low or even no energy input; nevertheless as water is usually pumped from pumping stations to the treatment plants, power cuts can affect natural treatment systems, pounded by algal growth. Municipalities should take particular care if the NTSs are close to human habitations and ground water aquifers, to anticipate health related issues, and be ready to address them. For the users, health risk assessments should be mandatory, and for the produce, food safety measures and testing should be part of the agriculture production process. The DEWATS system in Agra shows how operation and maintenance can be financed in an unconventional way in a tourism project in which the whole community is involved. All other systems were financed by the municipality which contracted a private company for operation and maintenance.
Acknowledgements Co-funding of the project leading to these results by the European Commission within the 7th Framework Programme under Grant Number 282911 is kindly acknowledged.
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