The huge unmet demand for fresh water for potable purposes has made it essential for the industrial sector to adopt water efficient practices. To this end, various players in water-intensive sectors such as power generation, steel, paper and pulp, and textiles have taken numerous initiatives to optimise their practices in such a manner so as to minimise wastage of water. Some of the key water management initiatives being taken by these players include recycling and reuse of treated wastewater, zero liquid discharge (ZLD) practices, desalination and treatment of effluents. In the past few years, these initiatives have come a long way in reducing freshwater consumption by the industrial sector.
Recycle and reuse
Besides the dwindling water reserves, recycling and reuse of treated wastewater by industries has gained significance owing to a number of factors. While the growing paucity of water provides a strong case for recycling and reusing treated wastewater, other factors such as a greater emphasis on reduction in the water footprint and tapping an additional source of revenue are providing impetus to the trend. To meet their increasing water requirements, industries are opening up to the idea of deploying advanced technologies to treat effluents, as well as recycling and reusing them for industrial purposes and green belt development. The treatment of this first-use water makes it suitable for further use, depending on the application. For non-potable uses in particular, in the industrial and commercial segments, this source holds significant potential for easing the pressure on freshwater resources.
Zero liquid discharge
Zero liquid discharge (ZLD), a cutting-edge wastewater treatment process, has been developed to completely eliminate all liquid discharge from a system. The ZLD system aims to reduce the volume of wastewater that requires further treatment, economically process wastewater and produce a clean stream suitable for reuse. It removes dissolved solids (mainly salt) from the wastewater and returns pure water to the process. In India, the Central Pollution Control Board has directed the pulp and paper, distillery, sugar, tannery and textile industries to achieve ZLD standards. Further, as a number of industrial users are facing increasing water shortages, many companies are moving towards recycling and reuse of wastewater produced in their manufacturing process through the installation of captive ZLD plants. This trend has gained prominence in a number of industries, particularly in the textile sector. States such Tamil Nadu, Rajasthan and Gujarat are witnessing significant activity in this regard. Consequently, there has been an increase in the order books of ZLD solution providers that are looking to expand their foothold in the rapidly expanding India market.
Driven by a judiciary ruling, states such as Tamil Nadu have progressed well with regard to the execution of ZLD projects. The Tamil Nadu Pollution Control Board has made ZLD systems mandatory for all highly polluting industries including the textile dyeing and bleaching industries. ZLD systems also ensure recovery of water and salt from the wastewater, thus preventing the pollution of rivers and groundwater. Tiruppur, a textile manufacturing hub in the state, was the first industrial cluster in the country and the first textile cluster in the world to implement ZLD. In Tamil Nadu, 90 per cent of textile dyeing units are located in the Tiruppur, Erode, Karur, Namakkal and Salem districts.
Key drivers
At the current pace of development, industries are bound to face an acute shortage of water for their operations. The need to look for alternatives to fresh water, environmental concerns and economic reasons have driven the growth of recycling and reusing of wastewater for industrial purposes. The government has released a number of notifications and guidelines in the past decade to regulate the utilisation of water by these industries, especially the power sector, which is a major consumer of water. The Ministry of Environment, Forest and Climate Change’s Notification Gazette 2015 has limited water usage to 3 cubic metres per MWh (cum/MWh) including the flue gas desulphurisation requirement for thermal plants installed after 2017 and 3.5 cum/MWh for old power plants. In addition, it has made ZLD mandatory for power plants set up after 2017. Another notable policy change in 2016 has made it mandatory for power plants lying within a 50 km radius of sewage treatment plants (STPs) of urban local bodies to use treated wastewater from STPs.
Use cases
- In a notable development, Tata Steel’s Bara tertiary treatment plant in Jamshedpur was awarded the Industrial Water Project of the Year, 2019 by Global Water Intelligence in April 2019. The plant, with a treatment capacity of 30,000 cum per day, has resulted in a 16 per cent cut in the intake of fresh water from the Subarnarekha river. The ultrafiltration treatment plant is part of the company’s plan to make Jamshedpur the first ZLD city in the country.
- The Nagpur Municipal Corporation, the Maharashtra State Power Generation Company and a private operator have signed a tripartite agreement for the construction of an STP for the supply of 150 million litres per day (mld) of treated wastewater for power generation.
- Further, Power Grid Corporation of India Limited has made a provision of soak pits in substations for the treatment of domestic wastewater, which is used for operational activities within the substation campus.
- The Welspun Group has set up a 30 mld STP at the Anjar factory which recycles sewage wastewater from the neighbouring areas. This has led to zero intake of fresh water for manufacturing processes.
- Steel Authority of India Limited is taking steps to set up treatment and recycling facilities in order to achieve ZLD at its plants. Of the three outfalls at the Bhilai and Bokaro steel plants, it has developed facilities for treatment and recycling of effluents from one outfall at each plant whereas works for the remaining outfalls are in progress.
- As a part of ZLD schemes, NTPC Limited is undertaking the installation of flow meters to monitor the discharge of effluents generated from the effluent treatment plant. It has also installed an ash-water recirculation system and a toe drain recirculation system to optimise water consumption in a closed cycle and achieve ZLD from the ash ponds. Further, it is in the process of installing flow meters in the facilities to monitor the quantity of treated effluents. NTPC is expected to significantly reduced the quantity of effluent discharged.
- Arvind Limited, a major textile sector player, has India’s largest ZLD plant which facilitates recycling of 16 mld of wastewater.
- JSW Steel has taken initiatives to improve the utilisation of water through the installation of a 4 mld ZLD facility at Salem as well as the recovery of quality water through the reverse osmosis technology.
- Orient Paper has become the first Indian integrated pulp and paper manufacturer to achieve ZLD. In 2018-19, it upgraded its effluent treatment plant and installed equalisation tanks with a diffused aeration system to achieve the same.
- Indian Oil Corporation Limited is also working towards making the Mathura refinery the first to use effluent discharge and sewage water for 100 per cent of its industrial uses. The refinery has planned to use 20 mld of treated wastewater from the STP located at the Yamuna riverbank in Mathura that is expected to be commissioned by January 2021.
Outlook
At the current pace of industrial development, water demand by the industrial sector is expected to increase multifold, calling for the need to keep water usage in check. To this end, the government has come up with regulations that enforce the use of treated wastewater by industries. The stringent water usage rules have increased the recycling and reuse of treated wastewater and also contributed to the greater number of effluent treatment plants coming up. Besides, the treated wastewater from STPs is also being supplied to the industrial and commercial sectors. However, there are a number of hindrances that need to be tackled in order to achieve wastewater ZLD standards such as high capital and operational costs. In addition, there is a need to enforce stricter compliance for quality of treated wastewater from the STPs and encourage industries to use it for their operations. As India is in the process of transitioning from a water-stressed country to a water-scarce one, it has become extremely crucial to ensure judicious consumption of water from the available freshwater resources and look at alternatives to its use.