Friday, August 4, 2017

Anupama/Ramesh Grey Water Treatment System Case Study


On 20 July 2017, we visited the site of a grey water treatment (GWT) system in a layout off Sarjapur Road in Bangalore. The family of four consumes approximately 18 KL of water per month. The water is provided by a combination of the layout sump, stored rainwater, and grey water.  The family saves about 600 litres of water each day by treating and reusing grey water for gardening.

GWT System Details
The GWT system was designed and installed in 2015 and currently treats about 600 litres of grey water per day - even less on days when the washing machine isn’t used. At the time of installation in 2015, the system cost approximately Rs 1.4 lakhs, including the civil work.

Before setting up the GWT, they would buy about 3 tankers of water every month (6 KL at Rs 600 x 3 = 18 KL for Rs 1800 per month). Now they pay Rs 8000 per quarter for layout piped water (approx. Rs 2666/month).


The water that gets treated comes from multiple sources. The GWT system currently treats water from the washing machine and one bathroom. It previously treated the kitchen utility as well, but it was disconnected due to backflowing (the dishwasher is also not connected). The family uses Surf Excel and Rustic Art detergents, Strategi for dishwashing, organic body soaps and shampoos which are easier on the GWT system.

The system consists of the following components:
Component
Dimensions
Notes
Baffle Tank
5’ x 2.5’ x 4.5’ with 3 baffles
Not cleaned so far, though Rajiv had put a small bag of activated charcoal into it because of slight odour
Reed Bed
4’ x 8’ x 3.5’
Full of bulrushes and canna
·       Biome helped source reeds from Rainbow Drive (another community that has a plant based water treatment system)
Polishing Pond
Approx. 3’ dia. x 8’ depth
Round, with a metal mesh cover

The treated water was tested and gave the following results:
     TDS: 1310 ppm
     pH: 8.2
     H2S: black in less than 48 hours, indicating presence of coliform bacteria





IMG_20170723_152654341_HDR[6587] - Anupama.jpg

There is a concern of leakage from the well because the water level in the polishing pond falls significantly as compared to before.

Water Source Overview
The family of four uses about 18 KL of water per month, or about 150 L/person/day. The sources of water are summarized in the table below.
Source of Water
Layout Sump
·       Piped to the house and stored in a 6 KL sump.
·       Used for all domestic purposes and some for gardening, especially in the dry season.
·       Billed every quarter; Rs 8000/- last month.
Rainwater
·       Rain from rooftop is harvested and stored in another 6 KL sump, which is mixed with layout water.
·       Sump overflows in heavy rain and runoff goes into recharge wells on the road.
o   There are plans to build a bigger one.
·       System was refurbished in 2015.
Grey Water
·       Treated in a planted gravel bed and polishing pond.
·       Used only for gardening.
·       System was installed in 2015.








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