Over 80 per cent of water consumed in flats and buildings comes out as wastewater. In un-sewered areas, the conventional practice has been to use a septic tank as the recipient of wastewater flows and the liquid effluents then emerging being led into soak pits or leaching trenches.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/decentralised-wastewater-treatment-making-strides
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/hindu-chennai
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/water-treatment-technology
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/wastewater-recycling