Communitarian Circular Water Management

 India faces the dual problems of inadequate potable water supply and pollution from untreated used water. This is mainly due to the colonial legacy of centralised water management that ignores the economically and ecologically sustainable household and community level circular water management, which is schematically depicted in the accompanying graphic.

The key to circular used water treatment and reuse is the separation of grey water (from kitchens and bathrooms) and black water (from toilets):

· Grey water accounts for nearly 85% of total used water and is easier and cheaper to treat.
· Low-cost methods such as filters filled with 25 mm brick pieces and with canna plant roots can clean grey water to prescribed standards.
· Black water treatment is costly due to the faecal matter in it. When grey and black water are mixed, as in centralized systems, costs rise significantly due to transportation, treatment in Sewage Treatment Plants (STP), sludge management, and infrastructure for reuse of treated water. Sewers need a greater water flow to prevent deposition of the faeces in transit and so it is imperative to mix grey and black water in centralised systems.
A very good example of circular grey water management, in this sordid context of its overall neglect in this country resulting in polluted water bodies, is the newly commissioned grey water treatment and reuse system at the Swami Vivekananda Vidyapeeth campus in Sehore district of Madhya Pradesh (https://lnkd.in/dw6NGFEE) run by the NGO Parivaar shown in the picture below.

This circular grey water treatment and reuse system has the following features:

· Daily inflow of 7,000 litres (with a peak of 5,000 litres in the morning).
· Three treatment chambers with 25mm brick pieces hosting beneficial microorganisms.
· Canna plants in the second chamber absorb nutrients and enhance purification.
· Hydraulic retention time of 3–5 days ensures that for the treated water collecting in the fourth chamber, all the important parameters such as ph, Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Dissolved Oxygen (DO), Total Suspended Solids (TSS), Total Nitrogen (TN), Phosphorus (P) an d Faecal Coliform (FC) are as per the standards prescribed by the Central Pollution Control Board as shown in the  table.

·  Automated disinfection with bleaching powder (5g per kilolitre) before reuse.
·  Treated water reused for toilet flushing and gardening, replacing costly potable water.
The installation cost of this system is only ₹30000 per kilolitre and the operating cost is ₹3 per kilolitre without the need for any electricity. Whereas, centralised used water transportation through sewers and treatment in STPs has a combined installation cost of ₹100000 per kilolitre and a combined operating cost of ₹25 per kilolitre. The cost of reusing the treated water in this localised circular system is low as the point of reuse is near to the treatment plant. Thus, Parivaar has set an example that should be replicated widely.