Staff Reporter

It can be used for gardening, cleaning and toilet flushing

60 per cent of water used per person is grey water Gravel filter through which water passes needs only to be emptied and put back once a year The treated water is neither potable nor can be used for bathing

Chennai: Representatives of various residents welfare associations in the city had a first-hand lesson in grey water recycling at the inauguration of a pilot project by Rotary Club in Asan Memorial School on Sunday.

According to water management experts at the workshop organised by Rotary Club, rainwater harvesting had become a household word but grey water recycling is still viewed as difficult.

Doubts cleared

The pilot plant, used to treat wash water from the school canteen, is open for viewing by persons interested in the subject. Residents had a range of doubts to ask: Is the treated water potable? Should the gravel filter be changed often? What plants can be used in the reed bed? Would not detergents kill the microorganisms in the soil?

Ecology expert Sultan Ismail, who designed the plant, explained that grey water (used water with the exception of toilet water) could be recycled for gardening, cleaning and toilet flushing purposes. However, the treated water was neither potable nor could be used for bathing, Mr. Ismail said.

The gravel filter through which the water passes needs only to be emptied and put back once in a year, Mr. Ismail said. The film that develops on the gravel (blue metal stones or marble could be used) was actually composed of microorganisms that thrive on phosphates in the detergent.

While wash water could be recycled, kitchen water treatment was not recommended in the first phase, Mr. Ismail said. This was because organic wastes could clog the filter bed.

Best plants

Indukanth Ragade, Vice-Chairman of Alacrity Foundation, said 60 per cent of water used per person was grey water. Alacrity had built several apartment complexes that harness the recycled water for gardening.

Mr. Ragade said the best plants to use for the reed bed include Canna (kal vaazhai), Banana and Colocasia (a yam).

The plants keep the soil partially aerobic by pumping atmospheric oxygen to the roots, where some microorganisms live.

Where there was no space for gardens, treated water could be put in a sump for future use.

Power-Point presentations of successful examples of water management were made before the participants.