Homes and gardens

Lessons in reusing wastewater

In the face of water shortage, falling groundwater table and drought, the city’s infrastructure managers and residents have their task cut out. A look at what IISc. is doing in this regard by S. Vishwanath

Sitting with the Professor in his cabin at one of the most prestigious learning institutions, one appreciated the conversation more than the coffee. He was explaining the process of setting up a used water treatment plant, as sewage treatment plants are called now, on campus. The discussions that had to be held, the convincing that had to be done on the treatment quality and finally the structuring, both technical and financial, so that the plant delivered the quality of treatment desired as well as was run efficiently for its life time.

The institution chose a technology called the Membrane Bio-Reactor, MBR for short, for treating wastewater. Based on the experience gained at running a similar plant at Cubbon Park in the city, this smaller plant designed to treat half-a-million litres per day was set up.

The treated wastewater is now absolutely clean, virtually indistinguishable from clean waters, better in quality in most parameters as compared to borewell waters and is being used unhesitatingly for non-potable purpose such as flushing the toilets and for gardening purpose and even to fill a small lake on campus. The best part of the project is that the system set up pays back for itself in about 4 years, making it economically viable.

Being a premier institution, the students of Civil Engineering have immediate access to the treatment plant and can learn much from it. However, if it were to be opened up to all students of engineering from other institutions, it would have greater impact. If apartment associations and layout resident associations could visit and learn, it would only encourage the spread of treated wastewater being reused. Other institutions with large campus could also benefit from the learnings gained in this small-scale treatment and reuse as demonstrated by the Indian Institute of Science.

Success stories

The city has many success stories as this one. If only they could be collated and shared between those who have the experience and those likely to benefit from it, a sort of virtual and real clearing house of knowledge on solving water and wastewater problems of the city, things would improve tremendously on the resilience and sustainability front.

Wastewater is no longer a resource below the radar. As water shortage kicks in, as groundwater tables fall, as drought has more and more of an impact the city cannot stand in splendid isolation from its rural hinterland. The response of Bengaluru has been interesting to the shortage felt in nearby areas.

Sweepingly large investments are being made, to pick up secondary treated wastewater and fill up tanks in the districts of Kolar, Bengaluru (Rural), Chikkaballapura and even Ramanagara. Over 770 million litres of treated waste-water will eventually be moved out of the city to be used for agriculture purpose and to fill groundwaters in the surrounding dry districts. Investments envisaged are well over Rs. 2000 crore in capital cost alone.

If implemented well, it will have enormous consequence for the city. The city will itself have less wastewater for itself but importantly the farmers will have access to nutrient-rich waters for irrigation.

Investing in science and knowledge to track these projects for health and environmental externalities, apart from the economic one, would be a great learning lesson and water wisdom.

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Printable version | Feb 26, 2020 12:15:55 AM | https://www.thehindu.com/life-and-style/homes-and-gardens/lessons-in-reusing-wastewater/article19427874.ece

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