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I had the opportunity to visit industrial and municipal sewage plants, and hence understand the status and trends in sewage water treatment in India, as we had an expert from Australia to whom we were introducing various waste water treatment facilities and companies in Chennai.

Some of the highlights for me were as follows:

1. For a city like Chennai, the total municipal sewage treated is close to 400 million liters per day. Over and above, some amount of water is discharged – untreated – into the lakes and rivers.

2. While the old sewage treatment plants essentially did just the primary (solid removal) and secondary treatment (removal of Total dissolved solids and Total suspended solids), after which the treated water is used in a clarifier before being discharged, the new plants also have the anaerobic digesters that use the sludge from the secondary treatment to produce electricity.

3. The water from the clarifier is apparently being used to water the plants and shrubs in the median at various roads in Chennai. That’s nice, except that the water had to be carried in lorries (I suppose) from the sewage plant to the medians, which means extra amounts of fuel used…

4. A large part of the sludge (that is not treated in digester) is discharged to the landfills. The effluent that exits the digester is used as a fertilizer for the greenery at the sewage plant itself (Yay, yay!)

5. At some of the new plants, the power generated from the digester is capable of supplying 80% of the total power required for the plant operations. That’s cool, but remember that anaerobic digester carries a high capital cost, so there’s no free lunch!