Achieving water sufficiency through wastewater management

Indian cities are displaying multiple water-related problems. On the one hand, drinking water availability for all people living in a city is inadequate. This is evident as there is a gap in demand and supply of treated fresh water and its low availability particularly in unplanned areas (i.e. unauthorised colonies and slums) of cities. Moreover, due to the non-availability of treated wastewater, the treated fresh water received through municipal pipelines for drinking/potable purposes is utilised by consumers for non-potable purposes, such as gardening, washing vehicles and driveways, flushing toilets, horticulture, construction, and industrial use. Such practices unnecessarily consume the limited treated fresh water available. It also leads to over-extraction of groundwater to meet the needs, which in turn results in declining groundwater levels.

The release of untreated wastewater by various consumers, including residential, institutional, commercial, medical and industrial establishments, has numerous social, economic, and environmental implications.

On the other hand, an insignificant volume of treated fresh water disposed of after consumption is treated again by civic agencies or other entities for reuse. The release of untreated wastewater by various consumers, including residential, institutional, commercial, medical and industrial establishments, has numerous social, economic, and environmental implications. The untreated wastewater contains impurities and pollutants that adversely affect soil quality, vegetation, surface water bodies (i.e. rivers, canals, lakes, ponds), groundwater, as well as the health of people and wildlife. For example, poor people dependent on river water for bathing and washing clothes suffer from numerous water-borne diseases and spend their hard-earned money on healthcare services.

Considering the role of wastewater (or used water) in meeting the water requirements of cities, and the negative effects of untreated wastewater, efforts are underway for its better handling. Domain experts suggest that for reuse, wastewater needs to be treated up to a level that the water is completely free from impurities. Further, it is mentioned that the discharge of inadequately treated wastewater (or non-compliance with standards) is still a common practice that results in the emergence of disease-causing organisms (or pathogens) in wastewater. Presently, many scientific laboratories in India release hazardous and toxic wastewater in nature. Similarly, industries release untreated effluents into water bodies.

This article describes a few city/institution-level wastewater treatment initiatives. It also explores the prospects of wider penetration of wastewater treatment methods and technologies in Indian cities.

Considering the role of wastewater (or used water) in meeting the water requirements of cities, and the negative effects of untreated wastewater, efforts are underway for its better handling.

In the National Capital Territory (NCT) of Delhi, the water agency supplies about 946 million gallons per day (mgd) of water, and the city generates about 792 mgd of sewage (or wastewater). Of the total wastewater generated, about 70 percent (550 mgd) is treated in various sewage treatment plants (STPs). Some wastewater treatment technologies/initiatives introduced are internet of things (IoT)-based technology for chemical enhanced dosing to achieve biological oxygen demand (BOD)/total suspended solids (TSS) below 10 milligrams per litre (mg/l), remote controlled automatic sampling units for composite sampling of sewage at STPs, and laboratory information management system software for generating real-time feedback on process control. Thus, the agency tries to maintain all quality control parameters (including the potential of hydrogen (PH) level, BOD, chemical oxygen demand (COD), TSS, oil and grease levels, ammoniacal nitrogen level, and dissolved phosphate) prescribed by the Delhi Pollution Control Committee (DPCC).

Currently, only about 89 mgd of treated wastewater is supplied for reuse in irrigation, horticulture, construction, and industry. Efforts are also being made to treat higher volumes of wastewater for power stations, groundwater recharge, toilets, and washing of motor vehicles.

The Delhi government is working towards early resolution of problems for deriving greater benefits: the sewage treatment plants (STPs) are not able to generate adequate treated wastewater because of low flow of sewage to STPs, delays in the connection of trunk and peripheral sewer lines with STPs, and incompletion of work related to rehabilitation of silted sewer lines. Further, several unauthorised/regularised colonies and peripheral urban/rural areas of Delhi are still without an underground sewerage system. The wastewater discharged from these habitats stagnates in open drains and nearby low-lying areas for indefinite periods, and the environmental conditions are ideal for mosquito breeding. A similar situation prevails in many small, medium, and large towns in India, including Aligarh, Firozabad, Meerut, and Sardhana. With regard to the quality of treated wastewater, the DPCC notes that many STPs do not meet one or more of the prescribed standards. Thus, there is concern regarding its reuse as well as release in surface water bodies, such as river Yamuna. The release of inadequately treated wastewater also affects the quality of groundwater.

The wastewater discharged from these habitats stagnates in open drains and nearby low-lying areas for indefinite periods, and the environmental conditions are ideal for mosquito breeding.

In some places in India, pilot projects for wastewater treatment are underway:

• At the IIT Bhubaneswar campus, efforts are being made to remove nutrients from wastewater. It is learnt that disposal of nutrient-rich (nitrogen and phosphorus) wastewater poses a threat to aquatic ecosystems.
• In Jaipur, a packaged wastewater treatment plant is installed to treat wastewater contaminated with pathogens.
• The pressure on fresh water in Mumbai is expected to be reduced by providing rotating biological contractor (RBC) and sand filtration technologies that ensure the safe reuse of treated wastewater for irrigation purposes.
• Kharagpur has initiated measures for the biological removal of nutrients from wastewater and pathogens inactivation. The objective is to recover protein-rich biomass as fertiliser and water for reuse.
• Work has begun on the management of sewage sludge (i.e. a residual by-product of wastewater treatment) in Roorkee by using thermal hydrolysis technology; it helps protect the environment from unpleasant odours, and surface and groundwater contamination and prevents the spread of pathogens. At IIT Kharagpur, ultrasonic treatment of sludge is being undertaken to reduce organic matter and pathogen content.
• The IIT Madras campus has installed a bioreactor to reduce residual nitrogen-based nutrients; it allows for increasing usability of treated effluents.
• Under the centrally-sponsored smart cities mission, wastewater-related projects have been implemented in various cities. Some examples are the use of robots to clean drainage holes and septic tanks in Coimbatore, training imparted to an all-women cooperative society in mechanised cleaning of sewers and septic tanks in Patna, the establishment of a self-sustainable sludge treatment plant in Port Blair, and design of a sewer network with the help of GIS-based terrain modelling as well as installation of decentralised STPs in Indore.

A review of ongoing work on wastewater management undertaken in various urban centres of India helps in understanding the significance of good quality wastewater; its availability in larger volumes is necessary for meeting the growing water requirements; the practice contributes to resource conservation and maintenance of good environmental conditions. Globally, many cities are working towards achieving the target of recycling 100 percent of the wastewater as part of their sustainability strategy; some are already treating wastewater to a level that is clean enough to drink.

In urban India, wastewater management is being done up to a certain level, however, more work is required:

• Unless the entire city-level requirements of sewerage planning, sewerage infrastructure (i.e. interconnected sewer network and treatment plants), and administrative efficiency in maintaining sewer systems/open drains are met, the water-related problems will remain.
• Civic agencies responsible for wastewater management do not have sufficient funds, knowledge, and technical expertise to properly discharge their duties. Those in need would benefit from support provided by central/state government, and non-state entities.
• The quality of sewage reaching treatment plants deteriorates further in transit due to citizens dumping various kinds of liquid and solid waste in open drains and cracks in sewer lines. Regular cleaning and maintenance by civic agencies, and awareness generation among citizens will lessen the burden of treatment entities.
• Some educational and research institutions (including the IITs and IIMs) have developed low-cost, environment-friendly, small-scale technologies for wastewater treatment. It will be beneficial for civic agencies to utilise such emerging and readily available technologies.

Rumi Aijaz is a Fellow at the Observer Research Foundation

• Water
• India
• Drinking Water
• environmental impact
• groundwater depletion
• resource conservation
• sewage treatment
• treated water
• untreated wastewater
• water problems

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