What really happens to this resource after it has been used?
Two answers to this question..
It's either discharged into water bodies as is, or it is first treated and only then either discharged or reused.
The former, although easier and cheaper, poses a great health hazard. Untreated domestic wastewater is a carrier of pathogens. When in contact with humans it can cause severe diarrhoea, dysentry and in the worst cases cholera. Lives are lost daily because of such unsafe practices.
In that light, wastewater treatment is slowly gaining attention. Decentralized solutions as opposed to centralized systems, require less capital investment, land area and are easier to operate and maintain. These factors made it an attractive option for urban communities.
One such decentralized approach to treating wastewater is Soil Biotechnology (SBT). This system, developed by a team of engineers at IIT-Mumbai, promotes a natural filtration mechanism which aims to treat water to a standard where it can be discharged safely.
During my consultancy with Arghyam, I carried out an evaluation of the SBT plant at ACCEPT Society in Bangalore. The article below explains the technology and presents a brief feasibility study of the same.
To view this article (pg 182-186), visit the link above and under the search button specify 182.
http://www.ezinemart.com/eaw/01092013/Home.aspx
Disclaimer: Please excuse the typos and formatting.. back and forth edits do very strange things many a times.