Chennai water crisis: Way ahead could encompass decentralised sewage treatment, solutions matching pain with gain

This is the final column in a four-part series on the Chennai water crisis. Read more from the series here.


If we could wave a wand that caused the population to shrink, restore our water bodies, change our economic model, and get our voters to vote for water management — the water crisis would vanish.

To wit, Chennai was early in the game in notifying groundwater legislation in 1987, via the Chennai Metropolitan Area Groundwater (Regulation) Act. To judge the toothlessness of the act, consider an extract from the Act:

“No person shall sink a well in the scheduled area unless he has obtained a permit in this behalf from the competent authority.

(2) Any person desiring to sink a well in the scheduled area shall apply to the competent authority for the grant of a permit for this purpose and shall not proceed with any activity connected with such sinking unless a permit has been granted by the competent authority.”

In 2002, the Act went on to say that one needed to get a license for drawing groundwater for non-potable purposes.

If it were not so tragic, the level of transgression is almost funny. The government perhaps realising this, repealed the Act in 2013, with one official being quoted as saying, requiring persons having over one HP pump set to register with the proposed Groundwater Authority, would have led to “public outcry.”

So what can we really do?

 Chennai water crisis: Way ahead could encompass decentralised sewage treatment, solutions matching pain with gain

A man uses a hand-pump to fill up a container with drinking water as others wait in a queue on a street in Chennai. REUTERS

Local effort in rejuvenating water bodies

In casting our eye over ever-faraway sources of supply, we lose sight of what is in our midst: our proximate water bodies — the ones that remain.

My husband grew up near the Chitrakulam tank in Mylapore — a neighbourhood in Chennai. He remembers that in the mid-80s, the groundwater had dried up, and the hand pump in the neighbourhood did not work, leaving the residents at the tender mercies of tanker water. The tanker would arrive at any time, and the residents would have to rush at any hour to collect water for their daily needs. Sometimes the tanker would come only every other day. At that time, the tank was dry and filled with rubbish — so overgrown with weeds that the children could not even play cricket on it. There had been no theppam (tank festival) for many years. Then one local “maama”, as my husband puts it, took the initiative to get the tank cleaned. Others pitched in and soon, the atmosphere improved. The tank filled when the rains came. The local community began to speak of the historic significance of the temple and the temple tank, to cement the respect for the tank. Once the virtuous cycle set in, groundwater levels improved.

(Update: The tank is dry again, underscoring the importance of continuous community engagement.)

At a larger scale, the Chennai Smart City Limited, a special purpose vehicle established to execute smart city projects, is taking up tank rejuvenation on a war footing. Partnering with the Greater Chennai Corporation, civil society, resident association and CSR arms of corporates, they have taken up over 200 water bodies for rejuvenation. Of these, 12 have been completely rejuvenated, helping replenish groundwater levels in the respective localities, while work is in progress in another 73.

Before and After shots of a rejuvenated Omakulam. Image courtesy Chennai Smart City Limited.

Before and After shots of a rejuvenated Omakulam. Image courtesy Chennai Smart City Limited.

I have a little more insight into the restoration of the Sembakkam lake, which is being coordinated by the Nature Conservancy. The importance of getting residents to buy into the effort, and most importantly of clearing the inlet and outlet channels in system tanks cannot be overemphasised. The difficulty of handling encroachment becomes easier if a motivated group adds their might to the task.

Rejuvenating water bodies is great for translating seasonal rainfall into perennial water supply. But we are ignoring a hyperlocal perennial source.

The glory of sewage

Funnily enough, what really excites me, is sewage.

Let me explain.

On the supply side, it’s important to realise that not all water uses need the same quality of water. Flushing and landscaping — together accounting for a third to half our demand — can be served quite easily with recycled sewage water.

One caveat: Please do not spend time and money, fruitlessly pumping sewage to a centralised sewage treatment facility from where the treated water is not of any use to persons who generated it. Rather, the model that cities like Chennai should consider is decentralised sewage treatment. Why?

Think of the trouble of pumping sewage to a centralised location – pipes could be broken; there could be an encroachment en route which ensures your sewage never reaches the treatment station; the centralised pumping station could have a maintenance problem. Then think, what happens to the treated sewage — who does it benefit?

Instead, think of a more local solution. In your apartment, under the car park could run a sewage treatment plant. One start-up does just this — build an underground STP with no operating expenditure. I have seen (and smelled) the treated water. Its quality visually beats my muddy bathing water in Chennai, and has been tested by IIT Madras to ensure it is safe for toilet/landscape use. Think. Your bore has begun to run dry. Tanker water is expensive and uncertain. What if significantly cheaper, readily available, reclaimed water (or ‘new water’, as Singapore calls it) could serve some part of your needs?

Apartments and offices across the country are discovering for them how wonderful a resource their own sewage is. If every bulk user (schools/apartments/hotels/offices) reused their treated sewage, they could cut their water purchases by more than a third. Payback times vary based on current water price paid and recycling technology used — but falls between months to a couple of years.

Almost as important as the treatment technology is the financial envelope surrounding the sewage treatment infrastructure. Apartment complexes may balk at the capital investment, which is why some start-ups are beginning to contemplate a “water-as-a-service” model for these, underwriting the capex, and then charging apartments on a per-litre of treated water, which is far more attractive in cash-flow terms for an apartment committee. We sometimes get caught up in the glory of technology while underemphasising the context of its use. This is the importance of local innovation — understanding the context of the customer — the importance of cash flow and lack of space in framing a solution.

Secondly on the supply side, rainwater harvesting helps. One professor from Velachery says, thanks to a combination of sewage treatment and rainwater harvesting, he has no water problems. But even in a state like Tamil Nadu, a pioneer in rainwater harvesting, many structures exist on paper only. In Madurai, in data from a thousand households, less than half had active rainwater harvesting structures. This data is corroborated in Chennai by studies from the Rain Centre.

Percentage of respondents, for the question — Do you have a functioning rainwater harvesting system? | Sundaram Climate Institute, 2018

Percentage of respondents, for the question — Do you have a functioning rainwater harvesting system? | Sundaram Climate Institute, 2018

While greening our urban spaces allows rainwater to replenish groundwater, in our own dwellings, we can check if the rainwater harvesting structures are working to help replenish our own bores.

Demand management

Now, for demand. As mentioned, for most of us, our understanding of how much water we use is poor. The poor, who wait in line, giving up sleep and leisure to fill pots of water, have a fine understanding of how much water they use and for what. But those of us used to water flowing when we open our taps, are habituated to not care how we use our water. This is now changing. A granular understanding is key in managing demand; my house in Madurai, for instance, has 15 water meters — in a single house. That’s what helps us understand where we can optimise usage, and truly helps in locating and arresting leaks.

Here again, the Chennai Smart City is helping install meters at bulk heads. Raj Cherubal, CEO of this SPV, says, “What you can’t measure, you can’t manage. We need metering of bulk heads, commercial building and water lorries — which are some of the smart city related projects.”

On a smaller scale, another start-up helps bulk users measure and reduce their usage through sensors and analytics. By charging on a per litre basis, the company has aligned its interests with saving water and made the proposition financially palatable for apartments.

A changing scenario

At some level, the current almost-predictable crisis comes about because we think water is plentiful. It is not. Earlier in this series, we asked why Israel behaved differently from India — leaning on management and innovation, while India depended on provision.

For one, in Israel, all water is the property of the government. Israel is a dry land, much of it desert. A company or a person or a farmer does not have the right to the groundwater under his or her land. Which means that for every person, water is a limited resource with a price. This encourages management, which, in turn, begets innovation.

In India, while the government might have acted, each of us assumed the ground below us held enough water for always. We now know that is not true. Perhaps, we too now will begin to manage and innovate.

One way in which the government can help is to frame policy that encourages bulk users to manage their water. Zero discharge is not feasible — even if bulk users treated and reused some part of their sewage, they will need some ‘fresh’ water for drinking and cooking needs (not everyone can go the T-Zed way), and there will be excess treated sewage, over and above, what is reused by the bulk user. One great way to use this treated sewage is to emulate what Bengaluru has done with the Jakkur lake.

This ties in neatly with what is needed: rejuvenate a local tank, get bulk users to treat their sewage, and feed in the treated sewage after tertiary treatment into the local tank. The government will need to facilitate this by helping lay pipelines for the transport of treated sewage to a local tank and by ensuring tertiary treatment at the tank. By keeping it local, we tie in incentives — after all, neighbours will not tolerate insufficiently treated sewage flowing into their tank. And the waters in the tank will help replenish local groundwater levels that will benefit all. This moves responsibility and onus from the government to ourselves; it makes the government’s role facilitative — the key mental shift we may need to make to get ourselves out of the crisis.

The writer is the founder of the Sundaram Climate Institute, cleantech angel investor and author of The Climate Solution — India's Climate Crisis and What We Can Do About It published by Hachette. Follow her work on her website; on Twitter; or write to her at

Updated Date: Jul 09, 2019 09:27:41 IST