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Step by step, drop by drop

P Anima | Updated on February 01, 2019 Published on February 01, 2019

Flower bed: The sewage treatment plant (STP) at Bawana is a raised and extended pebbled garden, flanked by knee-length green grills   -  KAMAL NARANG

Delhi plans to rejuvenate its defunct waterbodies with treated waste water

The waterbody is a shrivelling, muddy patch. A couple of desolate cranes search for prey. Boys cycle around it, men huddle together a few feet away under the shade of a tree. Two months ago, it was rippling with water. Around Chhath Puja in November, when women, mostly from Bihar, pray to the sun standing in ankle-deep water, tankers queued up at the vast waterbody in Bawana in North-West Delhi. Gallons of water from a dozen tanks were emptied into the pond so that devotees could pray.

What is left now is a large wet patch.

The waterbody was meant to be an oasis in a dry, dusty and industrial part of town, with a pond, a neat bank and green open space. But however dire it looks, it may stick to the script after all. The Bawana waterbody is set to be revived. It is among 259 lakes and ponds the Delhi government hopes to breathe life into as part of a project aimed at lifting the Capital’s sagging groundwater levels. Groundwater — the basic resource for the sustenance of cities and villages — has been skirting critical levels in Delhi for years.

Dry run: The waterbody at Bawana which is set to be revived with the treated water from the nearby STP   -  KAMAL NARANG

 

The new lifeline to the Bawana waterbody is less than a mile away, next to the region’s garbage dump — the Bawana landfill. Under the project, the waterbody will be filled with treated water from Ghoga drain, which brings in sewage from the neighbouring villages. In 2017, the Delhi government built a small sewage treatment plant (STP) — which experts call a constructed wetland — and it is effectively cleaning the black and polluted water from the drain.

“The pollutant component in the Ghoga drain is extremely high,” says Delhi Jal Board consultant Ankit Srivastava. “While the biochemical oxygen demand (BOD) levels in a normal drain are around 220 mg/l, here it is 332 mg/l, indicating industrial waste. After the treatment, the BOD levels in the outlet water is 31 mg/l,” adds Srivastava. A low BOD indicates good quality water, and anything above 100 mg/l is considered highly polluted.

Pipes will now be laid to take the treated water to the Bawana waterbody. A budget of ₹1 crore has been approved for the project, which will be carried out by the Department of Irrigation and Flood Control (I&FC). Under Delhi’s massive rejuvenation project, sources of treated water will be linked to local waterbodies. But, significantly, it will lead to the prevalence of small, local and cost-effective STPs such as the one in Bawana.

Clean act:Water from Ghogha drain is treated at Bawana STP   -  KAMAL NARANG

 

The Bawana STP is a pleasant surprise. There is nothing to indicate that you are standing on a sewage treatment plant, for there are no intimidating compound walls or officials guarding the gates. There is no heavy odour in the air either. A government employee is the only staffer at the site, which appears like a raised and extended pebbled garden, flanked by knee-length green grills.

But hectic activity is underway beneath the seemingly calm, concrete surface, as gravity brings the drain water into the first tank, where the solid waste settles, before it passes through multiple partitions and zig-zag paths, each weeding out pollutants along the way. The pebbled garden with cyperus and canna, its roots floating in the water below, becomes another layer of cleaners.

“The roots provide oxygenation and also weed out pollutants that are not taken out in normal STPs,” says Srivastava.

As water flows below 2-3 metre of gravel and pebbles, it keeps the odour in check. The STP, with capacity to treat 1 million litres per day (mld) of waste water, was set up at a cost of ₹1.38 crore. “Its capital cost is ₹1.17 per kilo litre, while that of a regular STP will be around ₹5-7. That makes it one of the cheapest STPs,” he points out.

Clean act Ghoga drain water after treatment   -  KAMAL NARANG

 

Round-the-clock power supply, essential to regular STPs, is not mandatory here. “What we have is a simple and scientific model executed in-house by a superintendent engineer,” notes Srivastava.

Experts say that such small, community-level STPs which allow sewage to be treated locally and can be used to revive local waterbodies are the way of the future. They are an integral part of a model Delhi has adopted to rejuvenate dry waterbodies and recharge groundwater.

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Environmentalists as well as regulatory bodies have been flagging the Capital’s water situation for decades. The Central Ground Water Board (CGWB) data shows parts of South Delhi as the worst-affected, where over-exploitation has plunged groundwater levels to beyond 40m. In a report to the Supreme Court (SC) last year, the CGWB said almost of Delhi, except for small, stray pockets, belongs to critical and semi-critical zones. Only 11 per cent of the Capital, it pointed out, had groundwater in the 0-5 m level. A NITI Aayog report last year warned that Delhi would be left with zero groundwater by 2020 if stringent interventions were not taken.

“Ideal groundwater level varies,” says CR Babu, Professor Emeritus at the Centre for Environmental Management of Degraded Ecosystems, Delhi University. “But it would range from 60 to 90 feet (18 to 27m), where the aquifers are located,” he adds. The Capital’s groundwater levels are so dire that it has exhausted three levels of it. “We have finished subsoil aquifer, unconfined aquifer and now we are going to deep aquifer. That is serious,” says Babu. He warns that water depletion from the deep aquifers will lead to massive subsidence — caving in of land.

Both the National Green Tribunal (NGT) and the SC had intervened in recent years and urged Delhi to take measures before the city dried out. In a July 2018 order, the NGT banned the extraction of groundwater by industries and commercial organisations. The SC had pulled up all stakeholders, including the Centre, the state and civic bodies, for their complacency in tackling the issue.

Subsequently, the Delhi government presented before the SC last November its action plan to revive over 200 waterbodies in the Capital.

Two governmental departments — the DJB and the I&FC — are helming the project with the aid of consultants that include Indian Institute of Technology Delhi, National Environmental Engineering Research Institute (NEERI) and WAPCOS. “The DJB will be taking care of 159 waterbodies and I&FC, 100,” says Srivastava.

Apart from reviving waterbodies, the project seeks to establish five new lakes — in Timarpur, Nilothi, Rohini, Dwarka and Najafgarh. While the DJB’s 159 waterbodies will be revived with a budget of over ₹380 crore, the lakes have a separate budget that ranges from ₹15 crore to over ₹100 crore, depending on the project size.

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Babu points out that the Capital once had over 1,000 waterbodies, of which a large chunk had been lost to urbanisation. Status, Revival and Greening of Waterbodies in Delhi, a report by the state’s Environment Department, says the Capital had 1,011 waterbodies, of which 40 could not be traced and only 600-odd can be revived.

Before and after: The Rajokri waterbody — a discharge area of 5-6 drains — was cleaned, enlivened and beautified as part of the pilot project   -  SPECIAL ARRANGEMENT

 

That new life can be breathed into lakes became apparent when Babu, with a team of scientists at the Neela Hauz Biodiversity Park, recently restored the dead Neela Hauz lake, which once supplied drinking water to South Delhi. The lake was desilted and the debris used for embanking and landscaping. Sewage emptying into the lake was treated by making it pass through a constructed wetland — two open oxidation ponds, three physical treatment plants and furrows and ridges.

“There is absolutely no doubt that waterbodies help recharge groundwater and improve local water conditions. But most of these are completely silted, so they have to be de-silted first,” says Babu.

He points out that sewage draining into waterbodies — which chokes the aquatic ecosystem and is a serious health hazard — needs to be treated. But it does not require gigantic STPs. “The constructed wetland system can considerably improve the quality of water that enters a waterbody,” he says. In the absence of continuous water supply, the waterbodies dry up, hence a steady supply of treated sewage into them is a practical solution, he notes.

Babu, however, rings a note of caution. While he welcomes the project to revive 259 waterbodies, he wants a sustainable management system to be put in place to take care of the functioning. “It is important to ensure that the project doesn’t lose its sustainability when the government withdraws from it. Unless a sustainable management system is put in place, waterbodies will go back to being dead.” He moots the idea of a wetland committee or commission to address the problem directly.

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In December last year, the Rajokri waterbody — cleaned, enlivened and beautified — was unveiled. A pilot to the revival project, it gave a glimpse of how a polluted waterbody — a discharge area of 5-6 drains — could be cleaned. Now, a decentralised STP ensures that clean water enters the pond, rejuvenates it and recharges groundwater.

“The community around it requested a Chhath ghat, so that has been developed,” says Yusuf Arsiwala, consultant, DJB, who takes care of landscaping the projects. Regular parks often do not have local STPs or rainwater harvesting systems. But each of the revived waterbodies — such as the Rajokri one — and the landscape around it will be self-sustaining, points out Arsiwala. “The purpose is to recharge groundwater as much as possible. Once that happens, water from the body can irrigate the landscape,” he adds.

At Rajokri, a natural landscape of indigenous plants marks the surroundings. “Here the wetland merges with the natural landscape. There are no signs telling you that this is an STP to which you do not have access. The plant species used for landscaping are indigenous and low-maintenance,” he adds. While such cost-effective and small STPs are found in a few campuses, as a policy, Arsiwala says, it has not been taken up by many state governments.

The rejuvenated bodies eventually have to become community spaces, he adds, and that is the key to making the project effective and sustainable.

Before and after: A revived waterbody has a Chhath ghat, which was made on the request from the residents   -  SPECIAL ARRANGEMENT

 

“Take, for instance, the Chhath ghat at Rajokri. When the community starts using it, they take ownership of it; they keep it clean and free of anti-social elements. Communities need to engage with the waterbody. The government has taken the first step,” he says.

While the projects are in the design and tendering stage, provisions require each contractor to operate and maintain the site for five years. Arsiwala says once the maintenance is transferred back to the landowning body, it needs to keep the community engaged with the site and ensure that it follows the regulations. Of the two NGT monitoring committees in place, one is mandated to monitor groundwater change.

At NEERI, one of the consulting firms for the project, Tuhin Banerji and his team, are negotiating deadlines and designs. “We have taken up designing work for both the DJB and I&FC,” says Banerji, a scientist. NEERI will prepare the design, make the estimates and ready the tender documents for 97 waterbodies under the DJB and 29 under the I&FC. “We will also be handling work on the five proposed lakes,” he adds.

At Timarpur, the project involves converting a defunct oxidation pond into a lake. “Six million gallons of water will be treated and put into the lake every day. We’ve done studies to understand the rate of percolation and are expecting high efficiency of water recharge,” says Banerji.

As a team handling multiple waterbodies, Banerji says the requirements are different for each of them. If a constructed wetland works at one, it may not in a densely populated area chock-a-block with buildings. “We might have to use floating rafters that will treat the water on the lake itself. In the case of industrial effluents, we might have to use a different treating system,” he adds.

Banerji has visited all the sites NEERI will handle, and picks the Aya Nagar project in South Delhi as the most challenging. “There are four sites and local people want to use the treated water before it gets to the waterbody,” he says. DJB water supply is scanty in the region and residents have laid their eyes on the waterbodies project. “If they take the water home, the treatment quality has to be very high, with less than 3 mg/l in BOD levels. It is not a difficult task technically, but treatment costs will go up. We have a budget to stick to,” says Banerji.

Hiccups and challenges aside, Banerji insists, the holistic model of small and multiple STPs to revive local waterbodies is the way ahead.

“It is the future. In fact, it is the only way forward. We cannot be spending so much money to treat sewage and put it back into the naala,” he says.

There is hope in the air, and perhaps clean water under the ground. At the Bawana STP, a worker lifts a concrete cover from the first tank to reveal murky black water. At the other end of the STP, where the treated water gurgles out, water is transparent and clean.

P Anima

Published on February 01, 2019
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