Working with Wastewater

Water treatment technologies deployed in India

Water is essential for daily sustenance and healthy living. With plummeting groundwater levels, contamination of water sources and increasing consumption, challenges in the water sector have increased manyfold. One of the biggest challenges is ensu­ring the availability of safe, sustainable and affordable water. In a scenario where fresh wa­ter supplies are not adequate to meet the growing demand, technology plays a vital role in managing and using the limited available water in a cost-effective and critical manner.

Water contamination is an outcome of both human activities and natural processes. Water is treated depending on its purpose – municipal, industrial or agricultural. The technology us­ed depends on the current water quality, the future standards required, and the economics of the treatment method.

A look at some of the technologies deployed for wastewater treatment in India…

The membrane bioreactor (MBR) wastewater treatment process is widely used in both industrial- and municipal-level wastewater treatment. It blends a membrane procedure such as ultrafiltration or microfiltration with an organic/biological wastewater treatment meth­od – the activated sludge process. The Cubbon Park wastewater treat­ment plant in Bengaluru is India’s first municipal wastewater treatment plant that dep­loys MBR technology. The pro­cess uses ultrafiltration membranes with pores that are 0.035 microns in size, capable of re­mo­ving bacteria and virus. It is an ideal example of recycle and reuse. The plant contributes to the maintenance of greenery at Cubbon Park and Vidhan Soudha, and provides water for construction purposes and sewer line maintenance. Many other projects, such as the brackish water reverse osmosis (RO) plants providing drinking water in villages of Andhra Pradesh and Gujarat, the Reliance refinery at Jamnagar, and the desalination plant at Trombay, are using membrane-based technology for wastewater treatment.

Companies have also adopted the recycling and reuse of wastewater through the installation of captive zero liquid discharge (ZLD) plan­ts. ZLD is a water treatment process that invol­ves ultrafiltration, RO, crystallisation and fractional electrode ionisation of wastewater. After the process, the entire volume of treated waste­water is fit for reuse. The deployment of ZLD systems is gaining traction in a number of industries, particularly textiles. Tiruppur, a textile manufacturing hub in Tamil Nadu, was the first industrial cluster to implement ZLD in the country, and the first textile cluster in the world to do so. Grasim Industries has installed a ZLD plant with a capacity of 2,700 kilolitres per day. Trident maintains a ZLD facility for towel processing, saving 6 million litres per day (mld) of fresh-water. NTPC Limited is in the process of implementing ZLD at all its power stations. It has been implemented at 10 stations so far. Meanwhile, Steel Authority of India Limited is taking steps to set up treatment and recycling facilities in order to implement 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 while works at the remaining outfalls is in progress.

In an attempt to augment water supply to the southern parts of Chennai, the Chennai Me­t­ropolitan Water Supply and Sewerage Board (CMWSSB) had set up a desalination plant of 100 mld capacity. The plant is following the seawater RO process, which is different from conventional surface water treatment plants. It starts with the inflow of seawater through gravity flow in a 1 km pipeline embedded at the sea floor at a depth of 10 metres. The inlet water from the sea is pretreated with a state-of-the-art pretreatment technology La­mella Clarifier, which not only efficiently re­mo­ves a high number of suspended solids from the incoming water, but also reduces the footprint of the entire facility. Another similar project being executed by CMWSSB is the Perur seawater desalination plant, which also uses the RO treatment process. In 2019, the state government granted administrative sanction to establish the plant for Rs 60.78 billion.

Conclusion

With the rapid rise in urbanisation, it is imperative to keep water usage in check and adopt techniques for wastewater treatment and re­use. The government has come up with regulations to enforce the use of treated wastewater by industries. Going forward, there is a need to ensure stricter compliance with quality standards by wastewater treatment plants, and encourage industries to use wastewater for their operations. India is constantly developing ways to address the growing water crisis. It is thus essential to ensure the judicious consumption of water from the available freshwater resources and promote the reuse and recycling of wastewater.