Panchayat head of the Chinna Kalapet fishing hamlet in Puducherry, R. Nagaraj, points to the area where wastewater from the houses in the village used to be let out.

?Water used to stagnate here, leading to the breeding of mosquitoes. Now, this area is clean and the villagers are happy about it,? he says. The change has come about after a team from the Centre for Pollution Control and Environmental Engineering, School of Engineering and Technology, Pondicherry University installed a low-cost and eco-friendly wastewater treatment plant in this village close to the coastline. The plant, based on a technology called ?SHEFROL? (sheet flow root level), has been designed by Professor S.A. Abbasi from Pondicherry University, and is a bio-reactor which uses the water hyacinth (Eichhornia crassipes) to absorb nutrients, pathogens and micro organisms from water. Grey water or domestic sewage from 38 houses is fed into the plant which measures around 9 metres by 2 metres, and has a capacity of 10,000 litres.

The plant consists of sand bags placed in pits and channels, a sedimentation tank and a non-permeable sheet which ensures wastewater does not seep into the ground. Costing only around Rs. 15,000, the university team says that the plant is affordable.

At Chinna Kalapet, the treated water is being used to irrigate a patch of Casuarina saplings. The plant was set up in November 2014 by PhD. student Ashraf Bhat as part of his thesis work with the guidance of Assistant Professor Tasneem Bhat. The SHEFROL technology was first tested within the Pondicherry University in 2006 to treat the wastewater for one building. Subsequently, two more plants were installed in the university, which use duckweed, water hyacinth and salvinia. A patent claim for the SHEFROL technology, backed financially by the Department of Biotechnology, Union Ministry of Science and Technology, was registered in 2011, and published in the Official Journal of The Patent Office, India.

Ms. Tasneem and Assistant Professor S. Gajalakshmi of the university are the co-applicants of the patent. The patent claim remains undisputed, says Mr. Abbasi.

?This plant takes only six hours to treat wastewater. It also rids it of its turbidity and smell. The villagers were convinced about the plant because of its flexibility, and its ability to safely discharge wastewater. The plant can be easily dismantled and set up in a new place,? says Mr. Bhat. Some of the advantages of the plant include its ability to be scaled up or scaled down according to the need. So, it can be customised to be used for one house or a large suburb, say the team members.

The plant is low maintenance one, says Mr. Abbasi. ?The villagers were trained to use the plant in a day. They have been maintaining it since installation. The robustness and ruggedness of the plant is what makes it unique. It can withstand any contingency,? says Mr. Abbasi.

The team has prepared a complete inventory of commonly available plants which are present in different regions, thus emphasising that the SHEFROL technology can be used anywhere. ?The technology makes use of the topography and gravity, thus doing away with the requirement of pumping water,? says Ms. Tasneem.

Though the technology has been patented, the inventors are offering free transfer of technology, like how it has been done in Chinna Kalapet, to communities and in public interest, say the team. ?We want more places to take up this technology. It is inexpensive, efficient, simple, robust and eco-friendly,? concludes Mr. Abbasi.