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Treated Used Water Reuse Plan for Thane City
Saiba Gupta, Ayushi Kashyap, Kartikey Chaturvedi, Kushal Pratap Mall, and Nitin Bassi

Suggested citation: TMC and CEEW. 2025. Treated Used Water Reuse Plan for Thane City. Thane: Thane Municipal Corporation; and New Delhi: Council on Energy, Environment and Water (CEEW).

Overview

The Treated Used Water (TUW) Reuse Plan for Thane City was developed by CEEW in association with the Thane Municipal Corporation (TMC). This first-of-its-kind plan aims to maximise the safe reuse of TUW, enabling a circular economy approach to (domestic) used water management in TMC. It promotes TUW reuse for non-potable purposes and establishes reuse–specific quality standards to ensure its reusability. This can reduce the city’s dependence on freshwater to meet its growing water demand, prevent the misuse of groundwater resources, and improve the quality of local water sources.

The plan sets city-specific targets for 2035 and 2046 to optimise sewage treatment capacity utilisation, upgrade sewage treatment infrastructure with advanced technologies, and maximise the safe reuse of TUW. It estimates the financial requirements and identifies reuse-specific business models to meet these targets. The plan also establishes a zone-wise implementation strategy, mapping treated water reuse zones to ensure efficient allocation and conveyance of TUW to identified users.

Key highlights

  • There is a deficit of 53 million litres per day (MLD) in the actual water supply from public sources for domestic and commercial uses in Thane City.
  • Currently, 73 per cent of the domestic used water generated in TMC is treated, of which only about 5 per cent is reused.
  • By 2046, the plan targets 82 per cent utilisation of installed sewage treatment capacity, enabling the treatment of all used water and ensuring that no untreated used water is discharged into the environment.
  • The eight reuse avenues identified in TMC have the potential to reuse 20 per cent of the total used water generated and 27 per cent of the available TUW in the city as of 2024.
  • Presently, all sewage treatment plants in TMC operate at the secondary level. Hence, the first phase of TUW reuse in TMC should focus on reuse applications that require secondary-level TUW, such as landscaping, wheel washing, and road cleaning. The plan recommends that TUW meet 100 per cent of the water requirement.
  • The plan recommends upgrading existing sewage treatment infrastructure to tertiary levels, enabling the safe reuse of about 70 per cent of the estimated TUW reuse potential for diverse applications such as commercial cooling, industrial processes, public utilities, and construction activities.
  • The cost of upgrading existing sewage treatment plants is 31 per cent less than the cost of setting up a new tertiary treatment plant.
  • TMC can recover the annual cost of tertiary technology upgradation by selling tertiary-level TUW to industrial and commercial users at a 30 per cent lower price than the existing freshwater prices for these sectors.

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"The TMC Reuse Plan offers a strategic framework to enhance used water management and implement TUW reuse projects in Thane City. It sets city-specific targets based on current and future water demand, considering planned development. The plan can serve as a template for other ULBs to develop standardised reuse plans across the state. This is crucial for mainstreaming a circular economy in urban water management."

Executive summary

Water security is crucial for the sustainable growth and resilience of economies. Managing freshwater demand should be India’s foremost priority in achieving water security, considering that 11 out of the 15 major river basins in the country will be water-stressed by 2025 (Bassi, Gupta, and Chaturvedi 2023). The situation is particularly severe in urban areas where scarce freshwater resources are unable to keep up with the growing water demand. Given the quantum of domestic used water generated in Indian cities, once safely treated and reused, it can serve as a highly valuable resource that can reduce the pressure on freshwater resources and improve the quality of rivers and aquifers. However, only 30 per cent of the domestic used water generated by Class I and II cities (population above 50,000) is treated (CPCB 2021). Further, the reuse of treated used water is very low, even in the major urban agglomerations in the country (Bassi, Gupta, and Chaturvedi 2023). Hence, it is essential to empower urban local bodies (ULBs) to formulate and adopt long-term reuse plans with clear targets for used water treatment and reuse – an element currently missing in Indian cities.

Vision of the Reuse Plan

The Treated Used Water (TUW) Reuse Plan for Thane City was developed by CEEW in association with the Thane Municipal Corporation (TMC). This first-of-its-kind plan aims to maximise the safe reuse of TUW, enabling a circular economy approach to used water management in TMC. It promotes TUW reuse for non-potable purposes and establishes reuse – specific quality standards to ensure its reusability. This will reduce the city’s dependence on existing freshwater resources for non-potable purposes, optimise resource efficiency, and improve the water quality of local water sources in Thane City.

The Reuse Plan sets quantifiable targets for 2035 and 2046 for enhancing treatment capacity utilisation, upgrading existing treatment infrastructure – mainly treatment technologies – and maximising the safe reuse of TUW in Thane City. Local authorities must align their efforts and resources towards achieving these time-bound benchmarks.

Approach for developing the TMC Reuse Plan

We studied Thane’s water and used water scenario over the years and devised long-term strategies for efficient used water management to create the TMC Reuse Plan. The plan considers used water as an important asset and an essential component of water resources management. The overall approach adopted to develop the plan is illustrated in Figure ES1. TMC officials were consulted throughout the development process, and over 20 consultations were carried out.

Figure ES1: Nine-step approach for developing the TMC Reuse Plan 

 

Key findings
  • Groundwater levels: The pre-monsoon depth-to-groundwater level in TMC has declined at the rate of 10 cm per year due to increased groundwater extraction, despite increasing rainfall.
  • Water quality: Three out of eight surface water monitoring stations in TMC were classified as polluted during the analysis period (2019–23). Average annual biological oxygen demand and average pre-monsoon seasonal faecal coliform (FC) levels in monitored nullahs (natural drains) were 46.94 mg/l and 3,495 counts/100 ml, respectively, which exceed acceptable standards for surface water, suggesting the discharge of untreated or partially treated sewage into surface water bodies. Additionally, the groundwater quality monitoring station in TMC reported that the groundwater was polluted in both assessment years (2018 and 2022). The annual groundwater quality index decreased from 130.55 in 2018 to 185.15 in 2022, with a higher groundwater quality index indicating lower water quality.
  • Water deficit: The city’s water balance analysis reveals a shortfall of 53 million litres per day (MLD) in the actual water supply for domestic and commercial uses from public sources.
  • Used water treatment and reuse: Currently, 73 per cent of the used water generated in TMC is treated, out of which only about 5 per cent is reused. Strengthening used water management can reduce the city’s dependence on freshwater to meet its growing water demand, prevent the misuse of groundwater resources, and improve the quality of local water sources.
  • TUW reuse potential: We have identified eight reuse avenues in TMC as of 2024 that has potential to reuse 20 per cent of the total used water generated and 27 per cent of the available TUW.
  • Treatment quality requirements: Presently, in TMC, all sewage treatment plants operate at the secondary level. If they can be updated to the tertiary level, the treated water will be able to fulfil over 70 per cent of the identified reuse potential.
  • Financial requirements: The Net Present Value (NPV) of upgrading existing secondary treatment plants with tertiary treatment technology is INR 4.67 crore per MLD and setting up a new tertiary treatment plant is INR 6.37 crore per MLD. Thus, the upgradation cost is 31 per cent less than that of setting up a new tertiary treatment plant. This cost includes both capital and operation and maintenance (O&M) costs, which are annualised over 30 years.
  • TUW tariff: TMC can recover the annual cost of tertiary technology upgradation by selling tertiary-level TUW to industrial and commercial users at a 30 per cent lower price than the existing freshwater prices for these sectors.
Action areas for TMC

The Reuse Plan has identified potential reuse avenues or users of TUW within Thane City, along with corresponding departments within TMC that oversee these areas (Figure ES2). Further details regarding the roles and responsibilities of the relevant departments in TMC are provided in Section 13.1 (Table 22b). The end use will determine the quantity of TUW required and the quality parameters that the TUW will need to meet, further influencing the design of treatment systems and, in particular, the treatment technologies required.

Figure ES2: Identified TUW reuse avenues and stakeholders in TMC 

Based on this, the plan recommends the following areas of action for effective TUW reuse planning and implementation:

  • Zone-wise planning: The plan recommends zone-wise planning for TUW allocation, considering the installed treatment capacity (and actual treatment) of existing and planned treatment infrastructure and the estimated TUW requirements of the identified reuse avenues located within each zone. The allocation criteria will further determine the conveyance mechanism adopted from the point of treatment to the point of reuse. For this purpose, five reuse zones have been defined – corresponding to TMC-defined sewage zones – with the existing treatment infrastructure (point of treatment) and the reuse avenues (point of reuse) mapped spatially (Figure ES3) within each zone.

Figure ES3: Five demarcated sewage zones within TMC for zone-wise reuse planning 

  • Treatment capacity utilisation: The existing used water treatment capacity in TMC needs to be strengthened in terms of the actual utilisation of the installed sewage treatment capacity. This highlights the importance of monitoring the O&M of installed infrastructure. The plan sets targets for actual treatment (as a percentage of projected installed treatment capacity) – 71 per cent by 2035 and 82 per cent by 2046 (Figure ES4). The 2046 actual treatment target accounts for 100 per cent of the projected used water generation. This is essential to ensure that there is no discharge of untreated or partially treated domestic used water into surface water bodies to prevent them from being polluted.
  • Priority for reuse: The first phase of TUW reuse in TMC should focus on the reuse applications that require water that meets the quality standards of the currently available TUW. Hence, reuse applications that require secondary-level TUW will be the first priority users. These include applications such as landscaping, wheel washing, and road cleaning, which have an annual estimated water demand of 7,035 million litres. The plan recommends that 100 per cent of this water requirement be met by TUW.

Figure ES4: By 2046, no discharge of untreated domestic used water is targeted in TMC 

  • Diversity of reuse applications: The existing treatment infrastructure in TMC needs to be upgraded to the tertiary level of treatment to realise the full TUW reuse potential. Also, any additional capacity should incorporate tertiary treatment technologies. This will increase and diversify reuse potential across different avenues – such as in industries, the construction sector, and commercial cooling – and hence build a market for reuse. Once the necessary infrastructure has been upgraded, the potential for TUW reuse will increase from 7,035 million litres per annum to 23,902 million litres per annum, with over 70 per cent of the current estimated reuse potential requiring tertiary-treated TUW.
  • Sustainable financing: The reuse projects need to be financially sustainable, with risk sharing between TMC, end users and private stakeholders. The plan recommends business models that can be adopted by TMC to implement reuse projects – including used water treatment, conveyance, and reuse. The recommended business models include onsite value creation, reuse utility buyback, and investments by end users. Further, the price of the TUW should be set such that the revenues generated help reduce/recover the costs incurred by the TMC and thus contribute towards making reuse projects commercially viable and sustainable. However, the TUW price needs to be lower than that of the freshwater to encourage its reuse.

The TMC Reuse Plan has been developed as a long-term guiding document for sustainable used water management in Thane City. It aligns with national and state guidelines for domestic used water treatment and reuse. The national Atal Mission for Rejuvenation and Urban Transformation 2.0 targets meeting 20 per cent of municipal water demand through TUW by 2025-26. Additionally, Maharashtra’s Treated Water Reuse and Management 2023 (Draft) Policy aims to replace 30 per cent of municipal freshwater use with TUW by 2025. The responsibility of implementing these policies lies with the ULBs, being the primary authorities for managing domestic used water in Indian cities. The TMC Reuse Plan provides a strategic framework and guidance to the ULB to strengthen used water management and implement TUW reuse projects within its jurisdiction. It sets city-specific targets that consider both the current and future water demand, factoring in the city’s planned development. This plan can be used as a template and provide direction to other cities to develop standardised reuse plans across the state. This is a crucial step for mainstreaming a circular economy in urban used water management.

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