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Construction : Perspective | August 2015 | Source : Infrastructure Today

Decentralised Wastewater Management Systems

Urban India is bracing for a unique and difficult challenge of shortage of freshwater as well as managing increased wastewater.

Urban India is experiencing an exponential growth. With about 377 million people, which means a third of Indians living in about eight thousand towns and cities, the urban Indian story is of both aspirations and challenges. More and more people are heading towards urban areas, dreaming of amenities and opportunities. Urbanisation has its own challenges because urban India seems grossly underprepared to house this highly ambitious immigration. Around 200 million people may be added to India´s urban landscape in about just the next two decades. And the challenges are not just limited to growth of population, but also the problems associated with that. In this article, we will talk mostly about the wastewater scenario in Indian cities, which is in a disastrous state at the moment. Estimates suggest that the more urban we become, the more water-guzzling our lifestyle. Experience and statistics both suggest that an average urban Indian uses at least three to five times more water than an average rural Indian. What´s more, the wastage of water in urban areas, with about 70 to 80 per cent of water supplied for domestic use, is also alarming.

Estimates of the Central Pollution Control Board put the total wastewater generation from only the Class I and Class II cities and towns at around 35,558 and 2,696 million litres per day (MLD) respectively, while the installed sewage treatment capacities are for 11,553 and 233 MLD only. However, the actual treatment is far too less. It is projected that by the year 2050, about 132 billion litres per day of waste water will be generated from Indian cities that is equivalent to 48.2 BCM. Further, experts also feel that the gap between wastewater generated and treatment capacity created will further widen. It, therefore, means urban India is bracing for a unique and difficult challenge of a shortage of freshwater as well as managing increased wastewater.

Polluted Water Bodies
A major threat of the untreated sewage and wastewater is to rivers and other water bodies. As per Census 2011, India has sewer systems linked to 32.7 per cent of urban households. The rest depend on onsite sanitation systems like septic tanks or public toilets. There is still a major section of the population in urban areas who defecate in the open. This is more in the slums that now comprise almost fifty per cent of the urban areas. Scant facilities of sewage treatment clubbed with unscientific disposal of septage pose a major challenge to the water systems and public health.

In fact, under various river action plans, the country has about 234 Sewage Water Treatment Plants (STPs). In class-I cities, oxidation pond or activated sludge process is the most commonly employed technology, covering 59.5 per cent of total installed capacity. This is followed by Up-flow Anaerobic Sludge Blanket technology, covering 26 per cent of the total installed capacity. Series of Waste Stabilisation Ponds technology is also employed in 28 per cent of the plants, though its combined capacity is only 5.6 per cent. But, the actual treatment has always been a grey area. In a recent event in Delhi, Union Environment Minister Prakash Javedkar said, ¨The actual treatment being done by all these plants would be somewhere between 15 to 17 per cent only. Delhi that boasts of the maximum coverage by sewer network, has only about 33 per cent of its habitations covered. The story is not so encouraging and the very vastness of the centralised treatment plants make them more difficult to cover in Indian cities, which face several physical and financial hurdles.¨

The problem is not domestic sewage alone. Some 12,368 MLD of wastewater is generated by industries. About 60 per cent of it is treated, but the ground reality is different because affluent treatments have so far been a very costly affair and many industries complain about their affordability. Small industries have been linked to Common Effluent Treatment Plants (CETPs) set up in clusters. Such plants adopt methods like dissolved air floatation, dual media filter, activated carbon filter, sand filtration and tank stabilisation, flash mixer, clariflocculator, secondary clarifiers and sludge drying beds, etc, to treat industrial effluents. The primary treatments remove coarse material and settable solids by screening, grit removal and sedimentation. Then the treated water is released into rivers. All these methods, however, have not properly worked, if one believes the river pollution statistics recently disclosed by the CPCB.

The CPCB has just come out with a report of pollution of India´s rivers. It points out the number of polluted rivers in India has doubled in just five years from 121 in 2009 to 275. Polluted stretches have also doubled from 150 to 302 in the same period. The report then reveals that the sewage generated from 650 cities and towns situated along the polluted stretches, has also increased from 38,000 MLD in 2009 to 62,000 MLD today. For instance, in Mahanadi River basin, the wastewater, including sewage load from major cities, has increased by almost 300 per cent in just two decades.

The planning in India is now undergoing a drastic change with the Prime Minister´s launch of three mega flagship schemes aimed at transforming urban India. It includes the scheme to build 100 Smart Cities, AMRUT (replacing JnNURM) in 500 cities, and ´Housing For All´. At least Rs 3 lakh crore is to be invested in these schemes in the coming five years. The JnNURM experience has not been that encouraging. India has spent USD 20 billion in 65 select cities between 2005-14 under the urban renewal mission. Despite that, the pollution of the rivers doubled. Six years after the National Urban Sanitation Policy 2008, only 13 states have initiated the mandatory state sanitation strategies, and only six of them have prepared complete sanitation strategies. Even the urban areas have lagged behind in forming the City Sanitation Plans (CSPs) that would have taken care of the wastewater treatment challenges along with other problems. About 200 CSPs have been prepared. Out of that only five have been finalised as per NSUP framework. All this calls for urgent attention.

Decentralised Wastewater Treatment Systems
Given the constraints involved in centralised systems, it is wiser to popularise and promote the Decentralised Wastewater Treatment Systems (DEWATS) approach. DEWATS has been hailed as a cost-effective and more successful approach that promotes people-centric waste to resource activities. As compared to centralised systems that are high on economic costs and require skilled manpower, decentralised systems can be promoted by involving local people and with low cost. It is important to note the system operates in a natural system, considering local conditions.

There are success stories of DEWATS approach dotting various cities in the country, with participation of several institutions. For instance, Kuchhpura in Agra is known for its location by the side of a large drain that takes wastewater from about five slums to Yamuna. A host of institutionsû starting from local to internationalû established a collaboration to design and construct a DEWATS using organic and natural water treatment processes. The objective was to treat and bring down the Biochemical Oxygen Demand (BOD) levels for reused water and recycling the processed wastewater for irrigation and safe disposal of compliant effluent. The system has developed a community management plan and as reports suggest it has helped the Kachhpura environment to improve drastically. This particular one was designed for treating 50 kL of wastewater.

Now that a lot of push is being seen for urban development, a mission mode is needed to promote decentralised wastewater treatment systems, such as the above, in massive scales. Of course, this alone cannot solve all the wastewater crisis. But this can solve a host of the problems. A lot of investments have to pitch in for promoting such systems. There is a need for strong regulations for industrial and municipal bodies. Technology has also to play a role in ensuring the implementation of regulations towards reducing pollu¡tion of the rivers, water bodies, and environment.

DEWATS Design
It uses a natural-three-step bio-remediation process. The first three chambers, which include the Screen Chamber (1.0 molecular weight (mw) + 1.1 millilitre (ml) + 1 metric ton (mt.) Deep), Pre-process filter Chamber (2.0 mw + 2.5 ml + 2.5 mt Deep), Baffled Septic Tank (2.0 mw + 7.5 ml + 3.0 mt Deep), are used for the sedimentation of the sludge, preparing the wastewater for filtration. The next chamber is Baffled Filter Reactor Chamber (2.0 mw + 22.0 ml + 2.5 mt Deep) that is filled with stone. This chamber accomplishes the filtration of the water. The last chamber is the Root Zone Treatment Chamber (2.0 mw + 22.0 ml + 2. 0 mt Deep), which is planted with Canna- the root of these plants treat the waste water.

This article has been authored by Ranjan K Panda. The author is the climate change researcher. He convenes a national online network ´Combat Climate Change Network, India.´ He can be contacted at ranjanpanda@gmail.com.

 
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