Wastewater Management in Urban India

By: R M Bhardwaj
The growing urban population and the developmental activities in rural India, both exert pressure on water supply and sewage systems. The existing infrastructure is incapable of meeting the ever-increasing demands for domestic as well as industrial water. The author argues that a judicial use of appropriate technologies is the answer to overcome the problems.
Urbanization

India is faced with two problems – lack of infrastructure and an increasing share of urban population. The urban population in India has grown from 285 million in 2001 to 377 million in 2011 – about 31 per cent – while the number of urban centres has increased from 5161 to 7935 during the same period (Census 2001, 2011). Even though the level of urbanisation is relatively low, in terms of absolute numbers India has the second largest urban population in the world. It is estimated that by 2051, about 60 per cent of the country’s population will live in cities and towns. The growing numbers have thrown up two self-perpetuating concerns: shortage of water and sewage overload.

As of now, public services do not keep pace with the demands – and water supply, sanitation, management of sewage and solid wastes cover only a fraction of total urban population. There are clear inequities and disparities between various segments of population including slum dwellers. Apart from the natural growth, migration of population, mostly from rural areas and small towns to big towns and cities, the cities’ physical boundaries expand to include newer rural areas within their orbit. Many cities have spread beyond municipalities, but the new urban agglomerations remain under rural administrations, which do not have the capacity to handle the problems of water supply and sewage.

WASTEWATER GENERATION AND TREATMENT

As against nearly 45000 million litres per day (MLD) of wastewater generated in the urban centres, the municipal capacity to treat wastewater so far is for about 11553 MLD accounting for merely 26 per cent of wastewater generation in urban centers (Infrastructure Report 2011) (Fig 1). It is estimated that the projected wastewater from urban centres may cross 116000 MLD by 2051 and rural India will also generate not less than 50,000 MLD in view of water supply schemes for community supplies in rural areas (Infrastructure Report 2011) (Fig 2). However, waste water management plans do not address the pace of wastewater generation.

Figure 1: Wastewater Generation and Treatment Capacity in Urban Centres
Figure 1: Wastewater Generation and Treatment Capacity in Urban Centres

According to the Central Pollution Control Board (CPCB), there are 284 sewage treatment plants (STPs) in India of which only 231 are operational. The remaining untreated sewage is the main cause of pollution of rivers and lakes. A large numbers of STPs created under Central funding schemes such as the Ganga Action Plan, the Yamuna Action Plan under the National River Action Plan are not operated in full capacity.

The development processes ushered in rural India are likely to generate huge volume of wastewater requiring appropriate optimal designing of water and wastewater management so that competing pressure on water resources can be eased. This includes strategies with equal weightage to a) augmentation of supplied water and b) development of wastewater treatment facilities, recycling, recovery, recharging and its storages.

Fig 2: Perspective Wastewater Generation from Municipal Sources in Urban Centres
Fig 2: Perspective Wastewater Generation from Municipal Sources in Urban Centres

 

CURRENT PRACTICES OF WASTEWATER REUSE

Not only has the volume of wastewater generated by domestic, industrial and commercial sources increased, the productive use of wastewater has also gone up, as small-scale farmers in urban and peri-urban areas depend on wastewater or wastewater polluted water sources to irrigate high-value edible crops for urban markets. Conventionally, sewage is collected through a vast network of sewerage system and transported to a centralised treatment plant, which is resource intensive. Instead of transporting it long distance for centralised treatment, CPCB is promoting decentralised treatment at local levels using technology based on natural processes. The properly treated sewage water can be used in pisciculture, irrigation, forestry and horticulture. Its conventional treatment generates sludge, which acts not only as manure, but can also be used for energy recovery. Some sewage treatment plants in the country are recovering this energy and utilising it.

New generation of sewage treatment technologies such as membrane bioreactor (MBR) can treat the waste water near to the quality standards of river water. With suitable renovation this treated sewage can also recharge a riverine system to ensure a perennial flow. It is pertinent to mention that the cost for activated sludge process is around Rs 9 to 10 million for 1 MLD sewage while that of MBR it is Rs 13 to 15 million for 1 MLD sewage (Infrastructure Report 2011). If the treated sewage by the MBR technique is linked to industry, the chances of payback are encouraging. In fact this would mean a paradigm shift with respect to sewage management – from sewage treatment to reuse and recycling.

Wastewater irrigation practices can be enhanced with improved policies, institutional dialogues and financial mechanisms – reducing risks in agriculture. Effluent standards combined with incentives can motivate improvements in water management by household and industrial sectors discharging wastewater from point sources. Segregation of chemical pollutants from urban wastewater facilitates treatment and reduces risk. Strengthening institutional capacity and establishing links between water delivery and sanitation sectors through inter-institutional coordination leads to more efficient management of wastewater and risk reduction

ENDNOTE

There is a need to judiciously use and reuse water from all available resources including wastewater. Municipal wastewater collection, treatment and disposal are still not awarded a priority status by the municipalities/state governments as compared to the supply of water. In the absence of sewer lines, untreated wastewater flows into the storm water drains and poses a health hazard to citizens. Despite various governmental schemes, the gap between generation and treatment still remains large.

There are various issues with treatment technology in addition to management aspects. The primary requirement of treatment is adequate supply of electricity which is a deterrent in the present context in almost all the states of the country. The selection of treatment technology in sync with available land in different urban settlement is another issue. The waste stabilisation ponds (oxidation, maturation and duckweed pond) are most appropriate for small towns whereas large urban settlements with land scarcity can opt for mechanical treatment systems, i.e., activated sludge process, trickling filter, upflow anaerobic sludge blanket (UASB) and aerated lagoons produce good results. There are success stories of treatment plants producing reasonably good quality water which is being used in the industrial sector for process as well as cooling purposes thereby reducing demand for fresh water.

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