India has been witnessing a growing focus on advanced wastewater treatment techniques and initiatives in the municipal and industrial segments. The government has been encouraging collaborations with diverse stakeholders to devise strategies and technologies for effective wastewater treatment. To promote such initiatives, the first centre of excellence (CoE) for water reuse called the National Mission for Clean Ganga (NMCG)-The Energy and Resource Institute (TERI) Centre of Excellence has been established by the Department of Water Resources, River Development and Ganga Rejuvenation, the Ministry of Jal Shakti and the NMCG. The primary focus areas of the CoE include research and innovation, capacity building and the development of technologies. Moreover, the CoE has representation from relevant stakeholders such as urban local bodies, water boards, industrial associations, civil society organisations and knowledge partners. It has undertaken various interventions to solve persistent issues in wastewater treatment. Some of these are focused on enhancing wastewater treatment systems through new technologies and improving their carbon footprint. These include the accounting of greenhouse gas (GHG) emissions and research studies addressing river pollution. Additionally, technologies such as the TERI advanced oxidation technology (TADOX) and zero liquid discharge (ZLD) have been implemented for effective wastewater treatment across various cities in India.
Efficient wastewater treatment through TADOX
Industrial wastewater treatment for industries such as textiles involves energy-intensive treatment processes. In addition, there is a heavy dependence on costly chemical treatments that lead to the generation of toxic sludge. According to studies, a textile common effluent treatment plant (CETP) generates around 42.6 kg per cubic metre of sludge. To tackle this issue, TERI has developed an innovative wastewater technique called TADOX through funding support from the Department of Science and Technology of the Water Technology Initiative. This technology involves the mixing of certain semiconducting nanomaterials, such as titanium dioxide, in the wastewater stream. After this, the stream is passed through a photocatalytic reactor, which is a closed assembly with ultraviolet (UV) light radiation sources. In the presence of UV light, these semiconducting nanomaterials generate hydroxyl radicals which have a high oxidation potential, aiding the mineralisation of pollutants like dyes. Following this, the nanomaterial is segregated in a recovery unit and recirculated in a textile CETP. TADOX technology has reduced the overall treatment time from 36-48 hours to a maximum of 12-18 hours. This technology has been implemented as a pilot in the Rooma industrial area of the Kanpur textile CETP and was funded by the NMCG.
In Kanpur, TADOX technology achieved a chemical oxygen demand of less than 50 milligrams per litre and a biological oxygen demand of less than 10 milligrams per litre. In addition, the frequency of colour achieved was less than 10 Hertz. It also facilitated water reuse of around 90 per cent. In terms of cost, around 50 per cent of the capital expenditure and 40 per cent of the operational expenditure was reduced. In addition to this, GHG emissions were reduced by up to 32 per cent. The process also reduced the use of chemicals by around 75 per cent, and the sludge was reduced significantly from 42.6 kg per cubic metre to 0.5 kg per cubic metre. As per these results, the load on the biological and the subsequent tertiary treatments is expected to be drastically reduced through the use of TADOX technology. This is likely to make the entire wastewater treatment process energy- and cost-efficient. Moreover, to understand the applicability and feasibility of the technology, the CoE has undertaken more than 35 case studies integrating the use of TADOX and examined its results. The results have highlighted that for the case of a textile CETP, the pre-biological treatment stage can be integrated with TADOX. Meanwhile, for cases like tanneries, TADOX can be incorporated into the post-biological treatment process to attain better results.
GHG emissions accounting
There has been a significant shift towards sustainable technologies and quantification of GHG emissions in the wastewater sector. Wastewater treatment plants and facilities adopt processes such as aerobic microbial degradation, which releases GHGs like carbon dioxide, methane and nitrous oxide. This makes treatment plants a significant source of GHG emissions. In order to make the treatment process more sustainable and systematically reduce these emissions, GHG accounting is of paramount importance. To this end, several research bodies and companies such as the CoE and TETRA Technologies have collaboratively undertaken a research study on GHG emissions (specifically methane) produced from domestic wastewater treatment in India. It aims to examine the disparities in GHG accounting data and their implications, along with recommendations for potential solutions and strategies. GHG emissions accounting will assist in the development of initiatives to minimise them and make the wastewater treatment process sustainable.
ZLD and abatement of river pollution
The CoE has undertaken several research studies and reports on the integration of ZLD plants with CETPs. It has recently completed a comprehensive assessment of an 18 million litre per day ZLD plant at Balotra in Rajasthan. ZLD has been recommended as a sustainable solution to issues such as groundwater contamination caused by the discharge of leachate into the environment. Recently, the CoE submitted a report to the Municipal Corporation of Gurugram and the Haryana State Pollution Control Board on adequate and sustainable treatment of the Bandhwari landfill leachate using ZLD. Further, ZLD is an efficient system for minimising the discharge of sewage into rivers, which is expected to help curb pollution. In line with this, the CoE has undertaken a study on the frothing of the Yamuna river in Delhi caused by sewage discharge. It is working closely on research-based policy interventions aimed at pollution abatement and the rejuvenation of the Yamuna river.
Other emerging wastewater treatment systems
Specific small-scale technologies are being adopted for wastewater treatment at different treatment stages. For instance, the Bangalore Water Supply and Sewerage Board (BWSSB) has undertaken a significant project in collaboration with the CoE. It has utilised moderate-temperature mesophilic-based treatments and higher-than-normal-temperature-based thermophilic treatments for improving sludge treatment. A study was undertaken by the CoE, which involved a comprehensive assessment of all the existing 36 sewage treatment plants managed by BWSSB. It examined the efficacy of the water and sewage treatment facilities and recommended technology-based solutions, a road map and a financial model to accomplish them. The use of these technologies has helped BWSSB improve their revenue generation through the use of treated wastewater. Further, these initiatives are expected to help BWSSB maintain optimal production and optimise the utilisation of of bio-solids and biogases.
Future potential
With the rising focus on making the wastewater treatment process sustainable and cost-efficient, technology interventions such as TADOX and ZLD are poised to transform the wastewater segment and make it more resilient in the coming years. TADOX technology can also be applied widely in areas such as ZLD, water reuse, decentralised wastewater treatment and lake rejuvenation. In the municipal wastewater sector, direct TADOX treatment can be achieved without stream segregation or biological treatments. Moreover, non-technological interventions such as GHG emissions accounting and collaborations with research institutions are expected to introduce efficient solutions to tackle the issues faced in the water treatment and reuse space. Going forward, these solutions can help better harness the potential of the water sector.
Based on a presentation and remarks by Dr Nupur Bahadur, Associate Director, NMCG-TERI Centre of Excellence, at a recent India Infrastructure conference
