In India, the agricultural sector uses more than 80 per cent of the country’s water resources, with well and tube well techniques being the most common methods of irrigation, drawing extensively from groundwater. This has led to increasing stress on groundwater levels, which are declining rapidly. As per industry experts, the estimated water demand in the irrigation sector increased from around 690 billion cubic metres (bcm) in 2010 to 910 bcm in 2015, and it is expected to further increase to over 1,070 bcm by 2050. The overexploitation of India’s limited water supply is a cause for concern. Therefore, it is crucial to improve water use efficiency in the irrigation sector. There is a growing focus on the use of treated wastewater for non-potable purposes, especially for irrigation. The government is also making efforts to improve water management practices and promote the use of reclaimed water in irrigation.
Current scenario
According to the Central Pollution Control Board (CPCB), urban households in India generated 72,368 million litres per day (mld) of sewage in 2021. However, the treatment capacity is only 44 per cent (31,841 mld), of which around 20,236 mld capacity is utilised and only a small proportion of 1,887 mld is reused. Therefore, there is significant potential for reuse of wastewater. The untreated sewage is released into waterbodies and the environment, leading to contamination and health concerns.
Enhancing irrigation water productivity and using treated wastewater will significantly reduce the pressure on India’s groundwater resources. In view of this, the government is encouraging the use of treated wastewater and treated effluent for irrigation and agricultural activities. One of the components of the recently introduced Arth Ganga initiative under the Namami Gange programme is the monetisation and reuse of treated wastewater for irrigation and industrial purposes. The programme entails various interventions for the reuse of treated wastewater such as the execution of action plans and the signing of MoUs with various ministries, departments and PSUs.
Potential of treated wastewater in irrigation
According to CPCB, sewage generation in India witnessed a compound annual growth rate (CAGR) of 4 per cent from 62,000 mld in 2015-16 to 72,368 mld in 2020-21. Based on the historical CAGR of 4 per cent, sewage generation is expected to reach over 100,000 mld by 2029-30. Meanwhile, treatment capacity increased from 23,277 mld in 2015-16 to 31,841 mld in 2020-21, registering a CAGR of 8 per cent. Going forward, treatment capacity is expected to reach around 64,000 mld by 2029-30. This presents significant opportunities for the reuse of treated wastewater for non-potable purposes in various sectors.
The water demand for irrigation is expected to rise in the future, creating pressure on groundwater levels. Therefore, with the reuse of treated wastewater, the irrigation sector can help reduce the pressure on groundwater levels. According to industry experts, irrigating land using treated wastewater will not only help generate revenue from agricultural produce but also provide additional benefits, such as increase in the economic value of nutrients recovered from wastewater and energy savings from reduced groundwater pumping. According to a study, reusing treated wastewater for irrigation in India could have reduced greenhouse gas emissions by 1.3 million tonnes in 2021. Tapping this potential of treated wastewater can promote circularity in urban wastewater management.
Of the 20,236 mld treated sewage in India, only 1,887 mld is being reused at present. In the best-case scenario, the remaining 18,349 mld can be directly used for irrigation purposes, with the help of the right set of technologies and expertise.
Gaps and challenges
Wastewater reuse for irrigation has several benefits such as reduced pressure on fresh water resources, supply of nutrients for the cultivation of crops and adequate water supply during droughts, etc. However, there are several challenges in using wastewater for irrigation. One of them is the lack of recognition of wastewater use for irrigation purposes. Only a few state policies recognise the need to employ treated wastewater for irrigation. There is a need to prioritise and mandate the use of wastewater. Another challenge is the availability of required treatment technologies for utilising treated wastewater. State irrigation departments and farmers do not have the right set of technologies for efficient utilisation. Other challenges include the lack of standard quality benchmarks, appropriate pricing of treated wastewater, incentives for end users, acceptance of treated wastewater by farmers and citizens, and legal and regulatory frameworks.
The way forward
The successful reuse of treated wastewater has been demonstrated by several countries worldwide. India also needs to establish and regularly update water quality benchmarks for discharge and reuse as well as enforce standards for the reuse of wastewater for non-potable purposes. The government must prioritise evaluating the potential of reusing treated wastewater and recognising it as a resource in terms of water, nutrients and energy for agriculture. This approach will help in effectively managing the water network, reduce pressure on freshwater resources and enhance water security in the future.
There is a need for a paradigm shift in the ideology of citizens. Wastewater must be recognised as an integral part of the water resources system that can serve as an alternative source of water. While some states in India recognise the importance of treated wastewater, there is still a long way to go. One of the major issues that need attention is the social stigma associated with the reuse of treated wastewater. Addressing this requires a concerted effort, which includes creating awareness regarding its potential benefits in reducing the pressure on freshwater resources. Establishing a monitoring mechanism is also essential to ensure the quality of treated wastewater and the quality of agricultural produce harvested from crops irrigated using wastewater. This can be achieved by conducting third-party assessments and testing. Overall, treated wastewater must be perceived as a boon and not a curse.
Naina Gulati
