60 per cent of grey water can be recycled: Expert

Indukanth Ragade, an expert in grey water recycling, has been helping apartment complexes in the city to recycle and reuse the water from the bathroom and kitchen, through a simple mechanism. “The process needs some soil space, water-loving plants like Cannas or Heliconium and sunlight. It does not need any chemicals, operates on gravity and is practically self-operating. This has been implemented in several apartment complexes and the Chennai Metro Water Supply and Sewage Board (CMWSSB) has analysed the water before and after treatment and found it effective,” said the expert. 

According to Ragade, grey water recycling is the easiest to implement and brings immense values, in terms of reusing water to recharge the groundwater. A rough calculation shows that almost 60% of grey water can be recycled. “For instance, a person uses 600 litres of water per month and 100 grams of soap. This small quantity of soap can be easily removed by installing water loving plants and then diverting water from bathroom and washing machine to the soil bed,” added Ragade. 

Sultan Ahmed Ismail, a soil biologist and grey water recycling expert, said that this mechanism – to begin with – should be made mandatory in large institutions with hostel facilities. “In hostels, the maximum usage is during the morning and evening, when the residents shower or wash clothes. This water has only soap. Every person uses 100 litres of water per day. If you have a hundred students, that is 10,000 litres of water. This could be passed through a simple, decentralised root-zone treatment plant and almost 7,500 to 8,000 litres of water can be recycled daily!” he explained. 

The recycled water can be used for gardening, added Ismail. “The recycled grey water has fertilisers such as nitrates, which are wonderful for gardening. If people are interested, they can treat this recycled water further and then pump it into a separate overhead tank, for flushing units of toilets, as the recycled water doesn’t directly come into human contact,” he said, pointing out that the water can be used to recharge the groundwater table. 

Ismail has helped several institutions install grey water recycling structures – including Chennai Mathematical Institute in 2006 and at Stella Maris College for Women. 

For the households too, grey water can be easily recycled. “In households, 65% of water is from washing machine or bath water. I don’t include kitchen water because in Indian cooking, there’s a lot of frying and that oil can clog up the percolation. The usage pattern is distributed throughout the day – in the morning, it is busier as children will bathe and get ready for college, later in the day, the washing will be done. All that is required is a 6x4 feet space to treat 1,000 litres of water per day. In households, to increase retention, baffles pin can be included in the tank, while will allow the water to flow to the plants (Canna indica and Colocasia),” he added. 

According to Ragade, the government should make greywater recycling mandatory too, along with rainwater harvesting. “The 2003 Rules also mandate that all old and new buildings treat their grey water in the garden and use it for flushing or for augmenting the shallow water table. This has remained a dead law because the authorities have not given the method for such treatment,” he added.