The over-extraction of surface water and groundwater to meet the increasing demand for water has led to their alarming low levels. The conventional methods of water supply are no longer a sustainable solution for municipal as well as industrial use. Thus, the principles of circular economy – recycling and reuse of wastewater – are now being adopted by large industries, water utility boards and urban local bodies.
Adoption in industrial segment
According to the World Bank, the demand for water for industrial use and power generation is increasing at a rate of 42 per cent per annum. The water stress will continue to rise under business-as-usual scenarios. In recent years, organisations from industries such as thermal power, steel, mining, cement, etc., are turning towards the use of recycled water.
The focus now is on zero-liquid discharge (ZLD) for reusing water in their manufacturing processes or in industry premises. ZLD plants are being installed across industries for wastewater treatment through ultrafiltration, reverse osmosis, crystallisation and fractional electro-deionisation methods. Coal-based thermal power plants commissioned after January 1, 2017 are mandated to ensure ZLD. Amongst the pioneering projects that have harnessed this technique is the Sipat super thermal power station of the National Thermal Power Corporation in Chhattisgarh. It is a large-scale, coal-fired power project of 2,980 MW and has adopted ash water recirculation systems, which typically allow recovery of 70 per cent of the ash pond water for reuse. Installation of sewage treatment plants (STPs) and effluent treatment plants (ETPs) at the station has further helped in the process. Similarly, several plants of Adani Power have been able to reduce their water consumption and ensure ZLD through the establishment of ETPs, demineralisation of water and rainwater harvesting. The results have been noteworthy as between 2020 and 2023, the company’s plants at Maithon, Haldia and Jojobera have observed a drop from 2.32 cubic metres (m3) per MW hour (MWh) to 2.27 m3 per MWh; from 3.31 m3 per MWh to 2.82 m3 per MWh; and from 2.72 m3 per MWh to 2.32 m3 per MWh respectively.
Similarly, there are some key examples from the steel industry as well. The Steel Authority of India’s (SAIL) Bhilai Steel Plant’s Universal Rail Mill has implemented ZLD. Recycled wastewater is being used for cleaning the plant’s filters. Similarly, Tata Steel Mining Limited has developed a 108 million litre per day (mld) common effluent treatment plant (CETP) at the Sukinda Chromite Mine. It treats 100 per cent of the generated effluent, which allows 90-95 per cent reclamation of recycled treated water.
With such initiatives picking up pace across industries, it creates the need for a robust operations and maintenance (O&M) contractual framework for long-term viability and quality assurance of these projects. In this regard, SAIL, in 2022, had entered into a contract with Arvind Envisol Limited for ZLD adoption at its Rourkela steel plant; the contract also includes O&M of the system for five years.
Initiatives in municipal segment
The growing demand for water across cities has put high pressure on water utility departments and urban local bodies. They are now making efforts to adopt more sustainable methods for long-term sustenance. A National Framework on Safe Reuse of Treated Water was formulated in November 2022 by the Ministry of Jal Shakti, in association with the European Union, which has set a target of 100 per cent collection of used water and its 100 per cent treatment for all states. Around 50 per cent of the treated used water is to be safely reused by 2025 and 100 per cent by 2030, where STPs are operational and collection and treatment capacity already exists.
The Delhi Jal Board (DJB) is actively focusing on reuse of water. The utility is developing a plant with 2 million gallons per day recycling capacity at its Bawana water treatment plant in Delhi. The Delhi government had approved this project in December 2022 to cater to the future demands for water in the city. Similarly, in Chennai, many projects are coming up to ensure optimum supply of recycled water for drinking through desalination treatment. A 400 mld desalination plant is an upcoming mega project, which aims to bridge the gap in the water requirement of the city. It has been awarded to VA Tech Wabag Limited in April 2023.
The Maharashtra government is also addressing the low quality treated water produced by STPs in the city. It has recently pushed the Aurangabad Municipal Corporation for the preparation of a detailed project report for the reuse of treated water released from STPs at Kanchanwadi (161 mld), Padegaon (10 mld) and JhaltaPhata (35 mld). Aurangabad Smart City Development Corporation Limited is also pushing for the same through the reuse of 90 per cent of the water from STPs. Similarly, the Goa government has also chalked out a plan to reuse treated water from STPs for reducing the burden on existing water sources. The infrastructure and other facilities to carry out this plan are expected to be developed within the next two years. The STP in Vasco is being considered for providing 2 to 3 mld of water to Mormugao Port Authority and Zuari Industrial Estate, besides providing for domestic use.
Pivotal role of technology
With less than 50 per cent of wastewater being treated in India, there is an urgent need to explore new and emerging technologies to ensure water efficiency. Some of these, such as geographic information system (GIS) and supervisory control and data acquisition (SCADA), and internet of things (IoT) are finding growing acceptance among both industrial and municipal segments. These technologies enable efficient monitoring of wastewater treatment plants, thereby ensuring quality output. As a result, direct reuse becomes easier without the need for other intermediary processes.
The Atal Mission for Rejuvenation and Urban Transformation (AMRUT) has also been pushing for widespread adoption of these technologies. GIS-based master plans have been prepared for 152 cities till March 2023 under AMRUT. These have been prepared using geo-referenced base maps and land use maps. The use of SCADA is also prevalent across many STPs. The technology is being adopted in the 564 mld STP in Okhla, Delhi, 30 mld STP in Gajadharpura, Jaipur, and 7 mld STP in DurgamCheruvu, Hyderabad.
IoT is being leveraged for cooling water analysis and an overall reduction in water consumption at Vedanta Aluminium’s power plants in Jharsuguda. These power plants reuse water through a circulating cooling system and a cluster of natural draft cooling towers. Real-time operational data and water quality parameters are possible with their IoT platform. IoT is also being used by the Boson Whitewater Company in Bengaluru, which converts water from STPs into high quality potable water. Their current IoT platform utilises artificial intelligence-based algorithms for detection of various anomalies such as filtration efficiencies, pump failures and variation in the life of filters. With the installed capacity of their system to treat 340 million litres of water per year, these data sets help in managing inventories of the plants better.
Future scope
The equitable supply of water in cities is a challenging task, with depleting and degrading surface water and groundwater sources. The adoption of a circular economy model that pushes the reuse of high quality treated water is inevitable. Programmes such as the National Mission for Clean Ganga are aimed at monetising this valuable asset with reclamation and selling of treated water to industries. It has identified 11 locations with a power plant near a river that can be sold treated water, instead of consuming untreated water directly from rivers. One such plant is an oil refinery in Mathura, wherein 20 mld of the treated sewage water will be provided as a part of an agreement. Similarly, the government’s Water Vision 2047 is also expected to be a major contributor to efficient recycling and reuse of wastewater.
The potential of accelerating reuse of wastewater is high through the implementation of decentralised wastewater treatment systems. To this end, DJB plans to increase its sewage treatment capacity to 903 million gallons per day by June 2023, with the construction of 48 new STPs and decentralised STPs in outer Delhi, among other initiatives. A modular STP decentralised treatment project is also under tendering with an estimated cost of Rs 4 billion under the NamamiGange Programme. There is also a promising avenue opening towards decentralised domestic wastewater management through a recent partnership with Japan. As a part of this, the use of Johkasou technology will allow the efficient reuse of treated wastewater.
