Reusing wastewater – treatment systemsNovember 25, 2010
This waste could be a resource
A look at some emerging technologies for wastewater treatment by S. Vishwanath
Try them out: (Top) Soil biotechnology system in Mumbai; (below) let waste-water have its uses
Managing waste-water as a resource has become the new paradigm, what with water resources being seriously competed for and the general difficulty of accessing water. Added to this scarcity value of water are the tougher laws on the environment and for pollution control.
Some of the interesting new technologies include DEWATS or decentralised wastewater treatment systems and SBT or Soil Bio-technology.
The DEWATS system looks at treating wastewater from a small 1000 litres to 1000 cubic metres per day. This system can handle wastewater from homes, apartments, institutions and even small and medium industries.
It is a four-step process which involves sedimentation, up-flow anaerobic digestion, aerobic treatment in horizontal planted gravel filters and, finally, aerobic treatment in a polishing pond.
The website says that more than 350 DEWATS systems have been implemented all across South Asia. The one at the Arvind Eye Hospital in Pondicherry has been an outstanding model.
The SBT treatment or the Soil Bio-Technology system has been developed by Professor Shankar from IIT-Mumbai. The system also uses what is called a combination of organic and inorganic matter in a soil layer with bacteria and earthworms as a mode of treatment.
A three million litres per day treatment plant is running in Mumbai for some time and the results have been extremely positive. In Bangalore, two experimental plants of smaller scale have been running and have shown excellent preliminary results.
Both DEWATS and SBT use nature as their source of treatment. Bacteria and soil-based creatures do their job sometimes in an anaerobic condition as with part of the DEWATS and sometimes in aerobic conditions as in SBT.
Both require low energy, if at all, and there are no moving parts, thus reducing maintenance issues and cost. Both can be integrated into landscapes and the treated wastewater used for productive irrigation applications as well as for non-potable uses such as toilet flushing.
The systems help in ensuring ‘zero discharge’ for the building where they are used.
More information on DEWATS is available on the website http://cddindia.org/ which is the Centre for Dewats Dissemination Society in India.
It organises regular training programmes too.
Information on for SBT from Prof H.S.Shankar should be available on the e-mail firstname.lastname@example.org.
China has seen a boom in wastewater treatment systems over the last five years. Similarly India too will see a boom in the business. Solutions for wastewater treatment will necessarily have to adapt to Indian conditions and work on reducing maintenance cost and manpower requirement.
The nutrients recovered from the waste-water treatment need to be used productively for soil enhancement rather than to pollute water bodies.
One of the biggest threats to the environment resulting in contamination of both surface water and ground water has been domestic sewage. Treating this will protect the environment and fresh water supplies, thus enhancing sustainable water availability. This is the path to water wisdom.