Wednesday, February 27, 2013

Rainwater harvesting in a Software Firm

A software firm located in the outskirts of Bangalore has been facing perpetual water shortage issues. It depends on external tanker supply and its campus borewells. With a population of 8000, it has  a daily water demand of around 200 KL. Adopting a proactive approach towards securing its water supply, the company management started exploring rainwater harvesting measures and engaged in a discussion with Biome.
With abundant rooftop area (~120000 sq ft), it was only natural to tap this runoff and store it in the sump which has a capacity of 200 KL.
Also, there is sufficient landscaped area and a well designed network of storm water drains. So recharging the ground water table was also considered, rather than letting the storm water drain into the sewage laden Vrishabavathi that cuts across the campus.

View of the campus

It was decided to execute the project in phases and therefore a part of the rooftop was considered for the pilot phase. First rain separators and Rainy FL-500 filters provided the job of physical filtration before sending the water to the sump. The water from the raw water sump passes through a treatment system comprising of a Pressure Sand Filter and a Chlorine doser. With this system, there is a potential to harvest around 973 Kl considering a normal rainfall year.

FL-500 Rainy Filter
Five recharge wells of dimension (4 ft dia and 20 ft deep) were dug at points observed to get maximum storm water runoff. The substrate was pretty rocky beyond 18 feet in the case of a couple of wells. Basic filtration is done with the help of concrete jallis and boulders positioned just before the recharge wells.

Recharge well

Channel for laying pipe to recharge well
The next phase will focus on tapping the remaining roof top area and adding more recharge wells based on the percolation rates observed in the current recharge wells.

Though the management had initial apprehension regarding the impact on aesthetics due to the RWH system, all fears were put to rest after the implementation and they are keen to get going with the next phase design and implementation.
Definitely a model worth emulating by other organizations.