A combined wastewater treatment and rainwater harvesting system

The household of Mahalakshmi Jayaram, an architect, is nearly independent when it comes to water. Wastewater is treated and reused here, and rainwater is directly used and also recharged into the ground. In fact, rainwater meets the household’s needs 10 months in a year.

RWH and greywater treatment systems were integrated back in 2011, during the construction of the house. Mahalakshmi says she had come across these systems in the course of her work. “I grew up in Chennai where water shortage is a major issue. When I moved to Bengaluru after marriage, I realised it was a problem here too.” She says taking these measures gives her a sense of independence, aside from knowing that she has reduced the burden on the system.

Her house in HSR Layout does not use any fresh water for gardening or car wash. Treated greywater is used for the vegetable patch on the terrace and for the plantain trees around the house. It is also used to wash the car and the front yard of the house. The treatment system is a reed bed, which naturally absorbs the pollutants in water.

Mahalakshmi says that her family uses organic hand-made soaps and detergents, so that the treated water would be cleaner and would not smell. She says the only time she had a problem with the system was when the reeds dried up. “But they started growing again, and there have been no issues since.” The only maintenance required is trimming the reeds once in a while.

The household gets BWSSB supply, but uses it only in the water-scarce months of March and April. This is because rainwater falling on one part of the roof is channeled to a 30,000 litre sump. Because of the high capacity of the sump, large amounts of water can be stored for long. The four-member family uses 12,000-13,000 litres of water a month. “After a week of rain, the sump would have enough water to last us a month. When the tank is full, it lasts two months,” Mahalakshmi says.

Rainwater falling on the other part of the terrace is channeled into a recharge well dug next to their borewell, which was used only for construction as it contains high levels of iron and salts.

Greywater treatment system

Contact water@biome-solutions.com
Capacity for treatment 600 litres. Only 300-350 litres is generated and treated now.
  • Pipes to carry greywater from kitchen and wash basins
  • Baffle filter with two chambers – settlement chamber and grease trap
  • Reed bed of dimension 7.01X0.45X1.2 m3. It is a concrete structure filled with jelly, in which reeds grow
  • A settling chamber for treated water <confirm if it’s there>
  • Storage sump of 2.7 m depth and 0.9 m diameter
Description of implementation Greywater from kitchen and wash basins are carried to the reed bed, where it is treated. Treated water is sent to an underground sump for storage; water gets cleaner by sedimentation here. Water is then pumped up to an overhead tank and used for gardening, and for washing the car and front yard of the house.
Cost of implementation Rs 70,000
Time taken Unavailable, since it was built during house construction
Any issues at present None

RWH system

Catchment Area
  • Rooftop area: 2000 square feet or 185.8 square meter.
  • Pipes carrying water from one part of the rooftop to the storage sump, and from the other part to a recharge well
  • First Rain Separator (FRS)
  • No. of filters, filter media
  • A 30,000 litre sump with one half for rainwater and another for BWSSB water; both halves are connected to capture overflow
  • A recharge well of dimension?
Description of the implementation Pipes carry rainwater from one part of the rooftop to two filters, and from there to the sump. Rainwater falling on another part of the rooftop is carried to a recharge well built next to their borewell.
Annual RWH potential About 162 KL (185.8X0.9X0.97)
Issues at present None

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