Karunguzhi in Kanchipuram district in north Tamil Nadu is one of 7,000 small towns in India where houses are not connected to an underground sewage network, and are entirely dependent on what are called ‘on-site sanitation systems’, such as septic tanks and twin pits to collect toilet waste. More than 500 of these non-sewered towns are in Tamil Nadu. Moreover, portions of even large towns and big cities with underground sewerage networks remain off the network, even in affluent parts of cities, such as Chennai’s techie suburbs.
Until a year ago, untreated