Recycling grey water with the roots of plants like Canna can give you a perennial source of water. Hema Vijay tells you how

In Gandhi Nagar at Adyar, an eight-flat apartment complex revels in the luxury of a perennial ground water source, enabled by a simple plumbing arrangement and a few Canna Lily plants. Here, a PVC pipeline takes grey water (bath water, wash basin water and washing machine run-off water) from the apartment to a narrow Canna plant bed.

As grey water trickles down, it gets purified by the action of the Canna roots and the natural microbes present in the soil, and the treated water enters the ground water table. “This system is absolutely safe and easy. Our bore well has never gone dry, and we have never needed to buy water”, says V.S. Sukumar, who built and lives in this apartment block.

Since grey water accounts for 50-60 per cent of a household’s average daily water consumption of around 920 litres, this apartment recharges its ground water with roughly 4,000 litres of water every day.

Elsewhere in the city, former DGP V. Vaikunth and President of Home Exnora S. Indrakumar too recycle grey water in their homes. Dr. Indukanth S. Ragade, grey water recycling (GWR) expert and author of Self-reliance in Water – A Practical Manual for Town and City Dwellers has installed GWR systems in a few apartments.

At a time when our parched city is looking everywhere for water, these isolated efforts hold out a crucial roadmap.

Make it mandatory?

Countries like Japan and Israel have successfully addressed water shortages by recycling used water. In the US, states like Arizona and New Mexico promote GWR with tax credits. Should GWR be made mandatory in Tamil Nadu? “The law which made rainwater harvesting mandatory in October 2002 also says that grey water has to be recovered in situ and used for flushing of toilets. ( Known as the TN Municipalities Building Rules Act (1972), it was amended to include RWH and grey water reuse,” says Dr. Sekhar Raghavan, founder, Rain Centre.

In practice, we have unfortunately ignored GWR.

Purification process

“Plants like Canna indica (Kalvazhai), hedychium (sugandhi) and heliconium supply oxygen to the soil in the root zones. Using this oxygen, soil bacteria break down organic compounds in grey water and render the water clean,” says Ragade. Grey water consists of very small quantities of exhausted and unexhausted soaps and detergents, and small quantities of organic salts like washing soda. “Bacteria consume the organic components like Linear Alkyl Benzene Sulphonate (LABS). Detergents also contain inorganic compounds called STPP (Sodium Tri Poly Phosphate). This acts as a nutrient for the plants and is consumed under aerobic conditions,” says Raghavan. Adds Ragade, “The treated water may be used to recharge groundwater, or collected in dug wells/sumps and used for flushing toilets; it is safe for these uses.” The treated grey water has been tested by the Chennai water and sewerage board (CMWSSB) and found satisfactory.

However, kitchen waste water does not quite work. It contains suspended organic matter that could lead to foul smells; it requires much larger soil spaces (6-8 sq. ft per person). Bath and wash water are safer for recycling.

While organic alternatives are available and preferable, mild cleaning chemicals can still be handled by the natural cleansing action of soil and plant roots. However, do avoid powerful synthetic chemicals and detergents that promise swift action.

Meanwhile, a few recycling residents have been inspired to go totally organic. “I use soap nut powder with ash and a little baking soda, which keeps my vessels spotless; vinegar for cleaning ceramic ware; activated effective microorganisms (AEM) as a toilet cleaning agent; soap nut powder as washing powder, and lemon grass oil for floor cleaning,” says Kavitha Ramakrishnan.