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2.6 Sewage Treatment Plant: Sustainable off-grid sewage treatment in

The Police Housing Corporation (TNPHC) has successfully constructed an off-grid sewage treatment plant (STP) to improve living conditions in the police housing colony in Avadi, a suburb of Chennai. This sewage treatment plant has not only solved the problem of sewage disposal but also provided a pond of treated water for fishing, vegetable cultivation and recharging of groundwater. It treats 12 litres of sewage every day with no negative discharge, produces manure, recharges groundwater, removes the source of foul odour and waterborne diseases, and beautifies the area.

Rationale in heavy stagnation of wastewater around the police quarter area, which became a source of foul odour and waterborne diseases, causing severe inconvenience to The lack of sewage treatment facilities was a major residents. concern for residents of the police quarters in Avadi, a suburb of Chennai under the of Thiruvallur The residents complained to the TNPHC, a state-level district. The police colony, constructed by the Chennai nodal body in charge of all police-related construction Public Works Department (PWD) in 1966, occupies an matters. After studying the area and the problems faced, area of 1,000 acres and houses approximately 12,500 a decision was taken to construct an off-grid STP that residents from 2,000 households. However, as the Avadi would transform waste into useful material. area does not fall under Chennai limits, it was not connected to the underground sewer system and had to dispose of its sewage through septic tanks. Objective The problem with this arrangement was that the percolation of water from the septic tank to the subsoil The STP was constructed with the objective of treating was little, as the soil was largely clayey. This resulted and reusing the sewage water generated in the Avadi police quarters.

Key Stakeholders

The programme is being implemented by the TNPHC with the financial support of the , and the beneficiaries are the residents of Avadi.

Figure 1: Key stakeholders

Residents of Avadi police quarters � Beneficiaries of the initiative

Tamil Nadu Police Housing Corporation � Main implementing agency

Image 1: Land affected by sewage was earlier Government of Tamil Nadu unutilised � Provides administrative approval and financial sanction Source: Housing Corporation

Social Sector Service Delivery: Good Practices Resource Book 2015 53 Avadi Sewage Treatment Plant: Sustainable off-grid sewage treatment in Chennai

Implementation Strategy The STP in Avadi is now almost maintenance-free. The process flow for the system is illustrated in Figure 2. The approach followed for implementation involved focussing on the basics initially, testing the essential viability of the project and then, if successful, scaling it up. Thus, the first goal of the project was to contain Figure 2: Process flow chart for sewage treatment the existing damage and treat the sewage that was RAW SEWAGE being generated. Emphasis was also placed on building a robust system that would be as maintenance-free as possible. Accordingly, the methodology of activated SCREEN CHAMBER sludge control was chosen for deployment due to its simplicity and reliability. The method uses air and a biological floc composed of bacteria and protozoa to treat sewage. A contractor was selected through an open COLLECTION/EQUILISATION tendering process to construct the STP using this method. Unplasticised Polyvinyl Chloride (UPC) material was used FILTRATE in construction, as it does not corrode easily and requires AERATION TANK less maintenance. SLUDGE SLUDGE Phase of the project began in 2003, with the target of DRYING SETTLING TANK RECIRCU- treating 2 lakh litres of water daily and constructing a BEDS LATION pond to store the treated water and use it to recharge the groundwater table. The project was completed PRESSURE FILTER in 2004. Phase II began in 2011 and had the target of treating 10 lakh litres of water daily. An additional STP was constructed for this purpose by 2012. ACTIVATED CARBON FILTER

HYPO After the construction of the treatment plant, its maintenance was handed over to the members of the TREATED SEWAGE police colony. Constables and pump operators were trained for three months by the implementing agency. Source: Tamil Nadu Police Housing Corporation

Image 2: (Clockwise from top left): Collection well; clarifier; settling tank; pressure sand and activated carbon filter; sludge drying bed, and treated water pond with walking track Source: Tamil Nadu Police Housing Corporation

54 Social Sector Service Delivery: Good Practices Resource Book 2015 environment

Resources Utilised products cultivated at the site are used in police canteens and are made available to the colony’s residents at Details about the resources utilised in the construction of subsidised rates. the STP in Avadi are presented in Table 1.

Table 1: Resources used in establishing the STP in Key Challenges Police Colony (Avadi) Residents of the police colony were initially reluctant to Funds (in Rs.) Additional Resources use the treated water. To address this issue, senior police Set-up cost Sand 1,000 cu.m officers were involved in building a consensus leading to acceptance of the initiative. The Additional Director General (Police), Inspector General (Prisons) and a Phase I 30,00,000 Brick jelly 96 cu.m former of Chennai visited the field site, held discussions with the residents of the colony and Phase II 1,00,00,000 Stone jelly 850 cu.m encouraged them to use the treated water. The unutilised Bricks 4,000 bags land around the plant was divided into plots that were to be used for cultivation. Three teams were formed to Running cost Cement 10,000 bags carry out the cultivation, and within six months the land Monthly reaped a harvest of bananas. The culture of cultivation electricity 15,000 Manpower 3,000 caught on, and kitchen gardens irrigated by the pond are bill now a common sight in the colony.

Source: Tamil Nadu Police Housing Corporation Subsequently, the TNPHC introduced fish cultivation in the pond by providing seeds and feed. However, residents showed reluctance in consuming the fish. To Impact deal with this, the previous strategy of involving high- level leadership was successfully used again. In fact, the Treatment of sewage, removal of odour and diseases: Additional Director General (Police) set an example by The immediate outcome of the STP in Avadi has been to consuming some of the fish himself. This encouraged treat 12 lakh litres of sewage every day with no negative many of the residents to follow suit. discharge, produce manure, recharge groundwater, remove the source of foul odour and waterborne diseases, and beautify the area. Replicability and Sustainability Production of economically valuable items: The water produced by the STP is being used for cultivation of The STP in the police quarters in Avadi successfully bananas, coconuts and vegetables; fish like katla, kapis converts waste into useful material. It replenishes the and logu; and beema bamboo, which is used in the environment, produces economically valuable items production of furnace oil, paper, cloth, ornamental items and removes a major source of inconvenience for the and mats. This fast growing, thorn-free plant generates community. The set-up costs for the plant were drawn high levels of oxygen and also acts as a green boundary from the funds earmarked for waste disposal in the wall. The 1,000 beema saplings brought from , housing project. The STP’s maintenance cost is low, Bengaluru, will be ready for harvesting in five years. The and there is no requirement for additional allocations.

Image 3: (Left) Cultivation of bamboo and (far right) bananas Source: Tamil Nadu Police Housing Corporation

Social Sector Service Delivery: Good Practices Resource Book 2015 55 Avadi Sewage Treatment Plant: Sustainable off-grid sewage treatment in Chennai

The fruits of the project are directly available to the construction of 2,673 houses for uniformed service community, which also has a stake in maintaining the personnel under the Own Your House scheme in system. Malakottiyur near Chennai.

The Government of Tamil Nadu recognised the value of the initiative and replicated it in several other locations in Conclusion the state. In 2010-2011, it launched a project in Central Prison. The plant cost Rs 45 lakh and has a treatment capacity of 2 lakh litres. The treated water The construction of the STP in Avadi shows how off-grid is being used to cultivate vegetables. The government or isolated systems for sewage treatment can effectively has decided to scale up and implement the model in manage sewage in a way that converts waste into useful all the prisons of the state. Similar projects have already products and also recharges the environment. Having been implemented in the Tamil Nadu Police Academy already been replicated at several sites in Tamil Nadu, in and in Kumarasampatti quarters in Salem the model offers a proven strategy for responsible and district. There are plans to use the Avadi model in the productive sewage disposal.

Fact Sheet

Theme Environment

Nodal Implementing Agency Tamil Nadu Police Housing Corporation

Geographical Coverage Tamil Nadu Police Housing Colony, Avadi suburb, Chennai, Tamil Nadu State

Target Groups The residents of Avadi Police Housing Colony

Years of Implementation 2003 - 2012

56 Social Sector Service Delivery: Good Practices Resource Book 2015