Managing Effluents: Wastewater recycling and reuse practices

Wastewater recycling and reuse practices

In light of the depleting water reserves, it is imperative to manage water resources efficiently. To this end, the concept of recycling and reuse of wastewater has started gaining traction. The key players in the sector are inves­ting extensively in technologies that enable the utilisation of wastewater, and promote the reuse and recycling of water. As per recent estimates, approximately 80,000 million litres per day (mld) of wastewater is generated in urban India. Of this, only 30,000 mld is treated, leaving a gap of about 50,000 mld. Overall, there are 25 operational plants for recycling and re­use of waste in the country. The cumulative capacity of these plants stands at 6,368.8 mld. State-wise, Maharashtra acco­un­ts for the lion’s share in the operational recycle and reuse capacity (43 per cent). It is distantly followed by Delhi and Uttar Pradesh at 20 per cent and 12 per cent respectively.

Indian Infrastructure takes a look at some of the key recycle and reuse initiatives undertaken to treat wastewater….

Zero liquid discharge (ZLD) is a water treatment process that includes ultrafiltration, re­ver­­se osmosis, crystallisation and fractional electrodeionisation. Following the process, the treated wastewater becomes suitable for recycling. As a growing number of industrial users are facing increasing water crises, a number of businesses are moving towards recycling and reuse of wastewater produced during their ma­nufacturing process through the installation of captive ZLD plants. The trend is also reflected in the rising order books of ZLD solution suppliers that are aiming to expand their foothold in the rapidly developing Indian market. The utilisation of the ZLD technique is gaining prominence in a number of industries, most notably textiles. States such as Tamil Nadu, Rajasthan and Gujarat are seeing a lot of development in this regard. NTPC Limited is in the process of implementing the ZLD process at all its stations. So far, ZLD has been implemented at 10 stations. NTPC reported a 1.3 per cent reduction in specific water consumption during 2018-19. Power Grid Corporation of India Limi­ted has taken various initiatives for improving water use efficiency and achieving ZLD across its locations. Further, Torrent Power Limited has implemented ZLD at its DGEN and SUGEN plants since April 2016 and August 2017, respectively, to facilitate the reuse and recycling of water.

Rainwater harvesting (RWH) facilitates the storage of run-off water during monsoon, which can be utilised for operational purposes by th­er­mal power plants. Hence, most power plants are building RWH facilities at their locations to ensure the storage of water. RWH also helps in reducing the burden on local water systems and providing a stable water supply. A large number of industries such as ITC Limited have successfully created a total RWH potential over and above their net water consumption. As of March 31, 2020, ITC Limited’s integrated watershed development projects have created a total RWH potential of close to 39 million kl, over three times the net water consumed by ITC during 2019-20. NTPC Limited has also implemented RWH systems at all their locations, in accordance with the Water Policy and Rain Water Harvesting Policy. In 2019-20, Indian Oil Corporation Limited recycled 41.35 billion litres of wastewater to reduce its freshwater requirement. Recycled wastewater acco­un­ted for 30 per cent of the company’s total operational wa­ter consumption. Similarly, the percentage of water recycled, reused and recirculated by Hin­dus­tan Petroleum Corpora­tion Limited during 2019-20 amounted to about 60.2 per cent. JSW Energy Limited has constructed two check dams at its Ratnagiri plant which facilitate storage of run-off water during every monsoon season. Jindal Steel and Power Limited has implemented RWH structures in and around the manufacturing sites for groundwater recharge. Further, it uses surplus rainwater collected in open pits to supplement its water requirement during operations of the plant.

Cycles of concentration are the number of times a tower recycles water before it needs to be dumped; it is also known as blowdown. It measures the degree to which the solid contaminants in the makeup water are concentrated in the recirculating water of an evaporative system. The higher this ratio, the greater the contaminants in the makeup water get concentrated in the system water. NTPC Limited en­sures circulation of water in a closed loop system due to which only makeup water is requir­ed for ensuring continuous operations.

Initiatives in the municipal segment

Several initiatives have been launched by ur­ban local bodies across the country to ensure the long-term availability of water. The Delhi Jal Board has developed 36 wastewater treatment plants (WWTPs) to treat wastewater for non-potable purposes. These WWTPs currently produce 420 million gallons of treated water each day. Delhi also aspires to reuse 80 per cent of its wastewater by 2027. Along the same lines, the Chennai Metropolitan Water Supply and Sewerage Board supplies 36 mld of treated wastewater to industries, and has built two tertiary treatment plants with a combined capacity of 90 mld. In order to generate up to 1,800 li­tres of tertiary wastewater, the Municipal Cor­poration of Greater Mumbai (MCGM) aims to build WWTPs in Colaba, Worli, Malad, Dharavi, Bandra, Versova, Ghatkopar and Bhandup. The MCGM has decided to make the use of treated wastewater from WWTPs a criterion for granting redevelopment approval in an effort to ensure that residential societies use treated wastewater. The Nagpur Municipal Corporation currently recycles about 90 per cent of its generated wastewater and is in the process of expanding the capacity of its WWTPs to recycle 480 mld of wastewater. Another significant de­velopment is the signing of a tripartite agreement among the Nagpur Municipal Corpora­tion, the Maha­rash­tra State Power Generation Co­mpany and a private operator for the construction of a sewage treatment plant (STP) to supply 150 mld of treated wastewater for po­wer generation.

The Surat Municipal Corporation (SMC) su­pplies 40 mld of tertiary treated water to industrial units in Pandesara. In addition, the provision of treated wastewater from two new units of SMC has also begun. The Bruhat Bengaluru Mahanagara Palike (BBMP) has set up four tertiary treatment plants at Cubbon Park, Lalbagh, Vrushabhavathi Valley and Yelahanka. The recycled water is distributed to various industrial and nearby areas. In order to conserve groundwater, the BBMP has made it ma­n­datory to utilise recycled water at construction sites. Additionally, the civic body has stated that building owners who do not use treated wastewater from STPs will not be granted occupancy certificates. The Karna­taka government aspires to attain a 25 per cent wastewater reuse target by 2025 and a 50 per cent reuse target by 2030.

The way forward

Currently, cities in the country are visibly deficient in the quality of wastewater recycle and reuse services they provide. There exists a ma­ssive backlog in the network as well as treatment across all city classes. Cities with million-plus populations also have backlogs of 40-50 per cent in both network and treatment coverage. However, the wastewater treatment market in India has just begun to unlock its potential. The sector is estimated to have grown at over 10-12 per cent of CAGR during 2016-21. Many aspects are contributing to this growth and hold the potential to set the ground for even higher growth in the years ahead. Flagship government programmes such as the Smart Cities Mission, Atal Mission for Rejuvenation and Ur­ban Trans­formation, Swachh Bharat Mission and Nama­mi Gange as well as promotion of recycling and reuse practices under the National Water Policy, 2012 are expected to provide significant impetus to this sector.