India is at a high risk of water scarcity and is among the highly water-stressed nations. While it accounts for 18 per cent of the global population, the country has access to only 4 per cent of the global water resources. Groundwater, the major source of irrigation and water supply in urban and rural areas, has been depleted to dangerously low levels in many regions in India. A report by The Energy and Resources Institute highlights the water crisis in the country, with annual per capita water availability expected to fall to 1,400 cubic metres (cum) in 2025 and 1,250 (cum) in 2050. India has the highest rate of groundwater utilisation globally, with this source providing 65 per cent of irrigation needs and 85 per cent of drinking water supply. The report also highlights that 70 per cent of the water is polluted and unfit for direct use.
Water scarcity is defined as the lack of availability of hygienic water of annual per capita quantity less than 1,000 cum. It can be due to the lack of physical sources of water to meet the needs of the area or community, or it can be due to economic reasons of poorly developed infrastructure for extracting, distributing, and managing the available water resources. However, there are no rigid boundaries and often reasons overlap and intermix, resulting in scarcity becoming an outcome of a complex system of interdependent factors.
Tackling water scarcity
Urban areas facing water scarcity can implement several solutions to address the issue. These include desalination of seawater for cities located near seashores, sustainable use of groundwater, reduced reliance on groundwater as a primary source of urban water supply, and an increase in water sourced from surface water bodies. Various programmes are being implemented in rural areas to tackle the water crisis. The World Bank supports some of these programmes, including, controlling and reducing groundwater depletion through the world’s largest community-based groundwater management programme in seven states, launched by the government under the Atal Bhujal Yojana, reducing irrigation by water drawn from tube wells in Punjab under the Paani Bachao, Paisa Kamao scheme, and supplying potable quality water to villages in Uttarakhand.
In terms of technological developments, zero liquid discharge (ZLD) has gained traction. It is a process that aims to eliminate the discharge of liquid waste into the environment. In this process, the wastewater generated from industrial or domestic use is treated in a ZLD plant to separate the liquid part for repurposing in activities such as irrigation. At the same time, the solid waste is recovered for disposal or to extract useful chemicals. Moreover, water recovery in ZLD plants can be achieved through different thermal processes such as multi-effect distillation, multistage flush, mechanical vapour compression, crystallisation of minerals, and recovery of condensate. Alternatively, new electrical technologies such as electrodialysis, forward osmosis and membrane distillation can be used for water recovery processes.
Treatment and reuse of municipal waste
With the imminent water crisis looming over in India, finding alternative water sources beyond natural freshwater sources is important. One such source is recycled or treated wastewater. In India, there is a huge potential for using treated wastewater. According to the Council on Energy, Environment and Water, only 28 per cent of the total urban sewage, that is, 20,236 million litres per day (mld) out of 72,368 mld, is treated, while the rest is disposed of directly into fresh surface water bodies. As of 2021, there were 11,622 million cubic metres (mcm) of treated wastewater available for reuse in India. This amount is projected to increase to 15,288 mcm in 2025 and 35,178 mcm in 2050. The treated wastewater available in 2021 could have been used to irrigate 1.38 milion hectares of land, resulting in crop production of 28 million metric tonnes and revenue of Rs 966 billion.
This scenario highlights the urgent need to develop policies and standards for treating wastewater. In November 2022, the central government issued a policy document, “National Framework on Safe Reuse of Treated Water”, to provide specific guidelines and directives for increasing the safe use of treated urban and rural wastewater for non-potable water needs. The framework provides guidelines for establishing funding mechanisms, coordinating activities among various agencies and stakeholders, as well as for river basin planning with recycled wastewater. The potential areas where reclaimed water can be used are irrigation, municipal non-potable purposes such as landscaping, parks, toilet flushing and firefighting.
There are several relevant policies and legislations introduced by the government for the reuse of treated wastewater. Some of these policies are the National Water Policy (NWP, 2012), the draft revised NWP (2020), the National Urban Sanitation Policy, 2008, the National Environment Policy, 2006, and the National Policy on Faecal Sludge and Septage Management (FSSM, 2017) that stresses the need for FSSM to achieve 100 per cent access to safe sanitary practices.
In 2011, the National Mission for Clean Ganga (NMCG) was established as a society to implement the objectives of the National Ganga River Basin project. The World Bank supports this project and aims to rejuvenate the Ganga through a river basin approach, reduce river pollution caused by direct sewage discharges, and ensure sustainable ecological and environmental balance flows. The Namami Gange programme is a set of actions taken under this mission. These include developing sewage treatment facilities in cities along riverbanks, riverfront development by developing ghats and crematoria, and cleaning river surface of floating solid waste. According to the project dashboard developed by Tata Consulting Engineers Limited, as of August 31, 2023, of the total identified 442 projects, 259 have been completed, 129 are at various stages of development, 42 are at the tendering stage, and 12 projects are yet to be tendered under the programme. Notable achievements include completing 2,666 mld capacity sewage treatment plants (STPs) against the 6,016.3 mld target and completing a sewerage network of 4,448 km against the target of 5,255 km.
Atal Mission for Rejuvenation and Urban Transformation (AMRUT) was launched in 2015 as a national water mission to provide water supply and sanitation facilities. The second edition, launched in 2021, takes this vision further by introducing circularity in water systems by developing a city-level water balance plan. This plan focuses on conserving water sources, recharging and rejuvenating waterbodies, recycling and reusing treated water, and rainwater harvesting. It also aims to improve system efficiency and reduce losses.
Under AMRUT, the identified states and union territories have targeted 5,873 projects, of which 4,676 have been completed, and 1,197 are at various stages of development. These projects have successfully installed 13.4 million water tap connections against the targeted 13.9 million and 10.2 million sewer connections against the target of 14.5 million. The 666 completed stormwater drain projects have successfully eliminated 2,434 waterlogging points, and the remaining projects will relieve waterlogging hazards from 1,307 points.
Water reclaim technologies
The technologies that are best suited for reusing treated wastewater based on the intended end-use such as industrial water end-use are multi-grade filter, dual media filter, ultrafiltration, etc. These technologies treat wastewater to meet the requirements of industrial-grade water. When the treated sewage (STW) has a high total dissolved solids content of over 1,000 parts per million, incorporating a reverse osmosis train into each of these systems is recommended. Secondly, when STW is intended for agricultural irrigation, it is preferable to disinfect the water using ultraviolet (UV) radiation or subject it to ozone treatment for agricultural end-use. Furthermore, when STW is to be directly charged into aquifers, it should be subjected to microfiltration followed by reverse osmosis and UV disinfection for aquifer recharge end-use.
In this regard, individual states can recommend specific technologies relevant to the local settings from the list presented in the Central Public Health and Environmental Engineering Organisation’s manual and compendium by IIT Kanpur. The Swachh Bharat Committee meets periodically to review and approve new technologies concerning sanitation, which the implementing agency may also adopt.
The current review of the critical water availability situation, both nationally and globally, highlights the need to identify alternative sources of usable water. With significant amounts of wastewater being generated, treating this resource and repurposing it in various sectors is a viable solution that is increasingly being accepted as a sustainable model. Technological advancements are taking place to reduce energy consumption and costs, making it possible to achieve complete water circularity. This will help ensure a wholesome life for all living beings.