BENGALURU: Researche rs from the Indian Institute of Science (IISc) have demonstrated that a decentralised grey water treatment system can be installed and easily operated in a rural Indian setting, and help reuse waste water. In an attempt to provide a feasible water treatment option to prevent groundwater contamination in rural areas of developing countries, they installed a decentralised greywater treatment system at Berambadi Primary School in Chamarajnagar district a year ago.
The process saved up to 1,80,000 litres of water annually, which was stored in an overhead tank for non-potable uses in the school. The system comprises slow sand biofilters, anaerobic sludge bioreactors, aerators and ozonation system. In collaboration with researchers from the UK, the IISc team studied the system’s performance over 12 months.
Their findings were published in the Journal of Water Process Engineering. Greywater is any water from households or offices that has not come into contact with faecal matter. Kitchen sink water is passed through a grease trap to strip off the top layer of oil and grease, while water from wash basins is strained for large food particles.
All the water then goes through three anaerobic sand biofilters - tanks filled with locally available coarse gravel, medium gravel and sand where bacterial biofilms (communities of bacteria that grow on moist surfaces) help in the breakdown of nutrients to reduce nutrient levels in the water, P S Ganesh Subramanian, former project assistant at CST and the lead author of the paper said in a release.
After this, the greywater flows through an anaerobic sludge bioreactor, and then a stratified biofiltration chamber. Finally, the filtered water from wash basins and kitchen sinks enters an aeration tank, followed by an ozonation tank where it is disinfected with ozone.
Ozone is generated using a cold plasma ozonator designed to disinfect waste water. “Ozonation removes odours and colours from water, and eliminates free chlorine (FC), thereby disinfecting the water while leaving no harmful byproducts,” he said. The team has already been approached by other schools to replicate the method.