Why better sewage management in Chennai will help fight floods

Down To Earth Editor Sunita Narain explains how the city's three rivers and 320 tanks and lakes that worked as flood barriers are used mostly for dumping sewage

By Sunita Narain
Last Updated: Friday 04 December 2015 | 13:09:45 PM

Chennai’s waterways: its shame

This article is an extract from "Excreta Matters", India's first comprehensive survey on the state of its water and its management.

Chennai gets enormous amounts of money to clean its rivers and waterways, which continue to look like this (Photo: R K Srinivasan)

The city, much to its shame, has three dead and defiled rivers – the Cooum, Adyar and Kosathalaiyar, which traverse it to flow into the Bay of Bengal. But this is not all the water wealth of the city. Chennai is crisscrossed with canals and dotted with lakes and other waterbodies. According to the City Development Plan, prepared for the centrally sponsored Jawaharlal Nehru National Urban Renewal Mission (JNNURM), there are as many as 320 tanks and lakes within the city’s boundary.

In addition, its ‘human-made’ canal – the Buckingham (known locally as the B-Canal) – adds to the pollution. The canal, built for saltwater navigation, is over 420 km in length, connecting the Pulicut Lake in Andhra Pradesh to Tamil Nadu. In this journey, it crosses the city of Chennai and links its two natural rivers, previously with its water, and now with its wastewater. In the past, the canal used to be an important channel for transport; now, it is virtually non-navigable because of its silt and organic waste load. All pollution surveys have found that the canal is heavily polluted.

But this is not all. The city also has many other waterways – the Captain Cotton Canal, only 3 km long, draining into the Cooum; the Otteri Nullah, which flows into the B-Canal; and the Mambalam, which joins the Adyar river. The total length of these waterways within the city is over 23 km; in the Chennai Metropolitan Area, they extend over 158 km.

The Cooum almost divides the city into half. The most important waterway of northern Chennai, it journeys for 18 km in the city and another 22 km in the metropolitan area. What is clear, say environmental scientists from the city-based Anna University, is that given the hydraulics of the four waterways of that part of the city, all the pollution generated would theoretically pass into the Cooum. The river is described as a languid stream as it has no flow in most months.

Adyar, the river of south Chennai, flows for 15 km in the city and 9 km in the metropolitan area. It enters Chennai at Nandambakkam and in its journey to the sea, it gets transformed into a wide lagoon – the Adyar estuary, with many islands and large sludge-filled backwaters. The Kosathalaiyar is a river of the Chennai metropolitan area; it does not enter the city.

All these waterbodies are in serious trouble. Explaining the problem of pollution, the City Development Plan says: “The waterways of Chennai (see Map: Waterways in Chennai metropolitan region) are not perennial in nature and receive flood discharge only during the monsoon season; the rest of the year these act as carriers of wastewater from sewage treatment plants and others.” The study on sludge in Chennai, done in the mid- 1990s, also shows most of these waterways were choked with sludge and wastes. In Adyar, for instance, the water width was only 15-200 m in the dry season, while sludge filled up 90-500 m.

Why are water bodies polluted?

The big question is, why do these rivers and canals remain so polluted, when the city has a near-perfect track record in water and sewerage provisioning? Also important to note here is that Chennai has received the single biggest chunk of the money under the National River Conservation Programme – some 11 per cent of the sanctioned costs till 2005 – for cleaning of its rivers. The Adyar and Cooum together were sanctioned 15 per cent of the river cleaning budget of the entire country.

The key issue in Chennai is that the city is planning with the assumption that its near-perfect sewerage coverage, pumping and piping plan will successfully intercept all its wastewater. Therefore, its entire programme for river cleaning is focused on investing in building and augmenting sewage treatment capacity; increasing the length of the underground sewage network; and adding to pumping and piping capacity.

In the late 1990s, the Union ministry of environment and forests sanctioned three major projects to the state under its river cleaning programme, among them the Chennai City River Conservation Project (CCRCP). This integrated project was sanctioned for Rs 1,200 crore, of which the Central government agreed to pay Rs 492 crore as a grant. The state government paid the rest, which amounted to about Rs 700 crore. The objective was to improve city waterways and disposal networks for increasing the capacity of the existing sewer system.

By the end of 2005, MetroWater had executed more than 95 per cent of its components under the project. Under CCRCP, another 80 km of sewerage lines was added at a cost of about Rs 12 crore to achieve 100 per cent coverage of Chennai city. MetroWater also put up five new pumping stations under the project.47

All the money spent has not helped. In 2006, the City Development Plan quoted a state pollution control board report, saying, “all waterbodies in the city are polluted and not suitable for any designated uses; level of contamination is worse in B-Canal, followed by Otteri Nullah and Cooum river”. So what is going wrong in Chennai?

Why is the pollution not under control?

Chennai’s STPs are all situated at the far corners of the city (see Map: The wastewater maze). Wastewater is pumped across the city to these plants located on the outskirts. This would make eminent sense if the treated wastewater was reused in nearby areas, for irrigation or by industries. Instead, the bulk of the treated and clean wastewater is disposed off into rivers and canals, which traverse the entire length of the city (carrying this wastewater) before flowing into the sea. This may still have been sensible if the rivers and waterways did not have any outfalls of sewage and were themselves clean and clear. But they are not.

Despite Chennai’s much vaunted sewage treatment infrastructure, its waterways continue to receive sewage from the colonies and industries along their way. In 2000, some 532 MLD of sewage was generated in the basins of Chennai’s waterbodies (see Table: The state of sewage). Along the length of the B-Canal, which cuts across both the Adyar and Cooum rivers, as much as 158 MLD of sewage was generated. The Tamil Nadu Pollution Control Board (TNPCB) has identified some 116 outfalls into just the Cooum. Altogether, some 423 outfalls have been located in the city (see Table: Wastewater outfalls in Chennai’s waterways). An article in the daily newspaper, The Hindu, says that even though MetroWater officials insist that only treated wastewater flows into the waterways, this does not explain the huge amount of sludge and sewage which is evident in these drains and rivers.

In fact, the newspaper’s correspondent even photographed and reported instances of tankers emptying raw sewage into the Cooum. In this way, the treated effluent is mixed merrily with huge quantities of untreated effluents. And the job of pollution control, thus, becomes endless and pointless.

In fact, strangely enough, the government’s own studies accept that the waterways in Chennai convey treated and untreated sewage and garbage together. These waterways, which are also the city’s flood discharge channels, are encroached and built upon as well, thereby severely reducing their flow. A 1994 sludge disposal consultancy commissioned by the state government had revealed that huge amounts of untreated waste in the rivers had led to sludge formation, clogging the waterways.

These waterways also traverse the growing outer city areas of this metropolis. The Chennai Metropolitan Area (CMA) covers some 1,189 sq km, of which the city limits are a mere 176 sq km. The sewage generated by this gigantic extended area flows into the same waterways, which get heavily polluted before they even enter the city limits!

For instance, the seasonal graph for biochemical oxygen demand (BOD) concentration in the Cooum shows that the river is already polluted when it enters the city. It gets more polluted as it traverses the city, with the big jump coming after the B-Canal mixes its waste with the flow (see Graph: The Cooum’s organic load).

Looking ahead

The city government has set out its vision for the future as far as water and sanitation is concerned. It wants to have 100 per cent piped water supply coverage in the municipal corporation and surrounding areas by 2016. The aim is also to have a per capita water supply of 150 LPCD by increasing the hours of supply to eight a day by 2011, and 16 a day by 2016. By 2021, the city looks forward to having a 24-hour supply.50

It also says that it plans to reduce distribution losses to 20 per cent by 2016 and do a 100 per cent recovery of its costs. However, it is a tall order when compared to its present situation (see Table: Aiming high).

How will Chennai cope with its source constraints? Chennai’s water supply is highly dependent on the returning monsoons. The city remains at the tail end of all sources.

Currently, in the best of situations, with huge investments to bring even seawater to its people, the city manages a supply of barely 90 LPCD. The slightest change in any of its sources can lead to a drop in supply of as little as 35 LPCD.

The city has estimated that by 2016, it will need about 1,800 MLD of water – its current supply is close to 800 MLD. By 2010, while water availability had jumped to 1,200 MLD, demand had also increased (see Table: What Chennai needs).

The options to augment its water sources are limited, says the city government. It wants, therefore, to concentrate on the sea for its future. It is banking on building desalination plants up to a capacity of 700 MLD, for which it is busy securing land and loans.

What will it cost the city to supply more

Chennai MetroWater has had the advantage of being a public utility which has kept a reasonably good control over its finances. But its increasing dependence on more expensive water projects will jeopardise this position. Its cost of water is increasing (see Table: Variable costs) and this should be a source of worry for its planners – particularly as it charges high rates from consumers and still needs huge investments in managing sewage.

Building up local water sources

As said before, Chennai has the country’s most successful rainwater harvesting programme. In 2001, the city introduced municipal by-laws which make rainwater harvesting structures mandatory in all multi-storey buildings. Then, in August 2003, faced with an unprecedented drought, the state government passed an ordinance making rainwater harvesting mandatory for all buildings (existing and new) in the city. It set a deadline of October 31, 2003 for the process to be completed and put its most competent officers in charge of ensuring that this was done (see Box: Catching rain in Chennai).

Catching rain in Chennai
Despite hiccups, rainwater harvesting has borne fruit

In 2001, the Tamil Nadu government had made rainwater harvesting (RWH) mandatory for all new buildings in Chennai. The state was racked by an unprecedented and severe drought in 2002-03, intensifying the groundwater crisis to a such a degree that in August 2003, the state government passed an ordinance making RWH mandatory for all buildings (existing and new) throughout the state. The deadline given for the process to be completed was October 2003 – a mere three months’ time.

A vigorous and intensive publicity drive was launched, both to convince the public that the government was serious about implementing the programme and to provide technical guidance in the design and construction of RWH structures. A phase of intensive activity ensued, and the programme was touted as a success. However, there were a few drawbacks:

  • The time given for implementation was too short.
  • There were far too few professionals with the knowledge and experience needed to design according to widely varying conditions.
  • The supply of trained and skilled labour to implement the works was inadequate; neither was enough good quality material available for implementation.

  • There was hardly any systematic follow-up to check the progress of the works reported to be completed.

In 2004-05, CSE conducted a household survey in Chennai: According to it, about 92 per cent of the surveyed households reported having installed RWH systems; 86 per cent of these had been installed after the promulgation of the ordinance. Only 11 per cent of the sample households got their RWH systems designed with MetroWater’s help, while another 12 per cent hired consultants to do the job. A large majority (66 per cent) sought the help of local plumbers in designing the system, while a little under one-fourth designed their own RWH systems. Non-governmental organisations were involved in less the 1 per cent of the cases.

With respect to design, about 52 per cent of the sample households have designed a proper system for diverting rooftop water to a recharge well or percolation pit, or for storing in sumps. About 10 per cent have reported faulty structures.

Despite the loopholes, rainwater harvesting has had its impacts. According to a 2007 study conducted by the Chennai Metropolitan Water Supply and Sewerage Board (CMWSSB), the groundwater table in the city has gone up by almost 50 per cent from November 2004 to November 2007. The city's average groundwater level, which was 6.18 metre (m) in 2004, has improved to 3.45 m in 2007. Villivakkam, for instance, which recorded a groundwater level of nearly 14 m in 2004, now boasts of a water table level of less than 1 m depth. Similarly, the level in Anna University, Guindy, which was 12 m, has been replenished and stands at 5 m.

The study contends that the quality of water has also improved with a drop in total dissolved solids (TDS). The TDS value of water in Chintadripet has dropped from nearly 5,000 parts per million (ppm) in 2004 to nearly 300 ppm in 2007. According to MetroWater, the salinity of groundwater in coastal areas such as Besant Nagar and MRC Nagar, Santhome has gone down in the last three years.

Barring slum pockets, about 75 per cent of the nearly 4.35 lakh households in the city have now installed RWH structures. In spite of lack of maintenance, MetroWater department officials maintain that existing RWH structures are still helpful in generating a 40 per cent recharge.

The ordinance mandating rainwater harvesting came into effect just as the city was in the grip of its worse ever water crisis. People were receptive to the idea since they understood the value of water. They wanted to save and recharge their home dugwells. The combined result was a successful programme.

A household level sample survey, done in the winter of 2003-04 covering some 1,500 households in the city, established the importance of rainwater harvesting. The vigorous and intensive publicity campaign undertaken by the state administration had worked. People understood the concept of rainwater harvesting and wanted it done in their homes. The problem was that there were too few professionals with knowledge and experience to cope with the scale and speed of the programme. Still, the impact was high.

As much as 92 per cent of the respondents of the survey reported that they had installed rainwater harvesting structures – 80 per cent of these were structures to channelise rooftop water into tanks and recharge structures around dugwells.

The question that arose was how could Chennai now expand such a system to make a difference in the city’s water future. A model, developed by researchers from Stanford University in the US, has looked at this issue. Without even harvesting, at least 9 per cent of rainwater in Chennai makes it to the aquifer. The model estimates that using policy as a driver, rainwater harvesting may be implemented to increase recharge to 27 per cent of the rainfall. The results show that aggressive rainwater harvesting keeps the aquifer recharged, as a result of which lesser numbers of private wells run dry during droughts and the tanker market gets reduced by almost one-third. The study recommends that investments to improve efficiency of water use, combined with aggressive strategies for recharge of groundwater, provide the best options for the future.

But if rainwater harvesting has to be a key option for the city’s water supply, then it must go beyond catching rain from rooftops, and move towards protecting its vast lakes and ponds. Currently, these are under threat from builders and polluters alike. The developers have not even spared the Chembarambakkam Lake, which is key for the city’s water supply. In 2007, the state government announced plans to build an industrial park near this lake. A group coming together as the Association of Chembarambakkam Lake Drinking Water Consumers filed a petition in the Madras High Court. The court ordered stoppage of work. Finally in 2008, the government ordered that the lands around the lake would remain agricultural.

This protection needs to be given to all tanks and waterbodies in and around the city, argues water expert A Vaidyanathan – “The tanks and wetlands in the city play an extremely important role as a source of irrigation and domestic water and recharge structures.” His study notes that the number of tanks is more than 1,500 and their rated storage capacity is around 939 million cubic metre (MCM). But these structures are in a serious state of disrepair. What is needed is to commission a detailed survey of the wetlands using remote sensing, and to use this study to prioritise regeneration and provide legal protection to each water structure.

Desalination: water from the sea

Chennai had some past experience in using seawater for drinking – MetroWater built a battery of reverse osmosis plants in the colonies along the sea – mostly inhabited by fisherfolk. The aim was to provide drinking quality water from a source close to where people live. These plants – three of a capacity of 0.15 MLD and two of 0.1 MLD – are small, built specifically for drinking water of local communities.

With this experience the city had tasted salt. In 2005, the Tamil Nadu government signed an agreement with a private party to build and operate a 100-MLD desalination plant for city water supply. The Minjur plant went operational in 2010. It takes seawater and then puts it through a series of water treatment and reverse osmosis technologies to remove salt.

According to senior municipal officials, the capital cost of this plant was Rs 473 crore. Under the agreement, MetroWater will pay the private company Rs 48.66/kl for the next 25 years. This rate does not include power, which is paid for separately, because of its variable costs. If this is added to the bill, then it would cost MetroWater another Rs 10-12 kl, taking water costs to Rs 59-61 kl for this seawater. But officials say the price is worth it as it gives them a reliable source.

So, the expense is not a deterrent for the city. It is now investing in another 100-MLD plant at Nemmeli, this time owned by the water board itself. The cost of this desalination unit is being supported through the Union government’s JNNURM funds. The cost of the project has been divided – part one comprises construction and operations and maintenance for seven years, awarded at a cost of Rs 1,033.68 crore (roughly half and half). The plant is expected to be ready by December 2011.

But it does not stop here. The city is also making provision for two more plants. Clearly, the planners think that the sea and not the rain is the answer for the future. What this expensive water will do to the city’s water accounts is not yet clear.

Recycling and reuse

The reuse of sewage and wastewater for industrial and even domestic water use is another option worth exploring. Chennai has the distinction of having the country’s first recycling project – the city’s sewage was sold to the Chennai Petroleum Company Limited (CPCL), which in turn used reverse osmosis technology to filter the sewage and turn it into water for its use. This industry found sewage more reliable than water and the costs were low as compared to its use.

The CPCL tertiary treatment plant, with a capacity of 41 MLD ‘reclaims’ sewage of the city. Better still, MetroWater earns Rs 12 crore per annum from the sale of sewage to this industry. This approach to turn waste into wealth needs to be promoted in this city of water stress and scarcity.

Chennai has shown that it can work on improving its water management system. Now it must work to provide new and innovative ideas to provide it water, in the worst of drought, and for all.

Carbon credits for metrowater
Biogas used to generate power and run STPs

Chennai MetroWater is set to receive Rs 4 crore every year from a United Nations body to implement environment-friendly projects. The financial incentive is for developing renewable energy sources that offset the use of fossil fuels, a MetroWater official said. The water agency would be presented ‘carbon credits’ for generating electricity from biogas to operate its sewage treatment plants in the city.

In a project implemented in 2005, MetroWater saves about Rs 4 crore a year by generating sufficient electricity through biogas from sewage sludge in four plants at Koyambedu, Nesapakkam, Kodungaiyur and Perungudi.1 The four STPs generate power using methane content of the biogas.

The project is currently under validation. After validation, it will be registered with the United Nations Framework Convention on Climate Change (UNFCCC), the authorised body for issuing carbon credits.2

This article is an extract from "Excreta Matters", India's first comprehensive survey on the state of its water and its management.

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Related Story:

Why Chennai floods are a man-made disaster

Rain reigns in Chennai

IEP Resources:

State of environment report of Chennai metropolitan area

Contamination of ground water in Tamil Nadu

Environmental degradation of the Coimbatore Wetlands in the Noyyal River Basin

Churning still water: a briefing paper on the state of urban waterbodies, conservation and management in India

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  • Outstanding article. Will Tamil Nadu Government consider this.
    Dr.A.Jagadeesh Nellore(AP)

    Posted by: Anumakonda Jagadeesh | 2 years ago | Reply