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Technological solution to toxic industrial wastewater finding its way to food chain

By Proshakha Maitra*, Megha Gupta*, Dr Mansee Bal Bhargava** 

The rapid growth rates of population, urbanization and industrialization in India has put the country in a critical state with respect to environmental degradation. The essay focuses on water pollution which is among the most acute environmental threats among others. About 50,000 million liters of wastewater is generated in India every year from various industrial and domestic activities (Chakraborty & Mukhopadhaya, 2012). This wastewater often flows into the nearby waterbodies mostly untreated and thus raising the pollution levels of the waterbodies beyond a tolerable limit. Despite spending huge amount of money on the various schemes to treat waste water, water pollution remains the biggest challenge of the water crises.
India has close to 90% of businesses represented by the micro, small & medium enterprises (MSME) sectors. While the guidelines are laid out in detail for the installation of Effluent Treatment Plant (ETP) or transfer of effluent to the Common Effluent Treatment Plants (CETPs), the reality is that 72% of the industrial wastewater remains untreated and is disposed of in rivers/lakes/groundwater affecting its natural quality as well as its natural regenerating capacity. This could either be due to the high cost of installation/operation of the ETPs or non-functional ETPs or insufficient capacity of the CETPs or weak implementation of the regulations. In many situations, the toxic synthetic chemicals discharged from the industries are impossible to break down by natural processes. The toxic chemical through the water have found their way to the food chain causing severe health impacts to humans and other beings.

Session on industrial water pollution and treatment

A prior discussion at Wednesdays for Water on the municipal wastewater treatment deliberated on the pressing need to switch to ‘Decentralized Waste Water Management’ where Nature based Solution (NbS) as a green and sustainable option for wastewater treatment was discussed at length. This discussion is taken further with a session organized on ‘Industrial Water Pollution and Treatment’. The session invited Dr Nupur Bahadur and Vaibhav Shrivastava as the speakers. Nupur is a Senior Fellow & Head of NMCG-TERI Centre of Excellence on Water Reuse (NTCoE) and Area Convenor of TADOX® Technology Centre for Water Reuse in Water Resources Division of TERI. She is also the Vice-Chairman, International Water Association (IWA)-India and Adjunct Faculty at the Department of Regional Water studies at TERI School of Advanced Studies. Vaibhav is a Water Auditor at the CIIs Water Institute. He has been involved in designing decentralized wastewater treatment systems in India and abroad. The session discussant is Balpreet Kaur, who was then pursuing M. Tech in Water Resource Engineering and Management at the TERI School of Advanced Studies. The session is moderated by Dr Fawzia Tarannum. The video of the session is available here.

Industrial wastewater treatment and tadox technology

The water scarcity in the country demands large-scale reuse of water for which efficient wastewater treatment is crucial. Industrial wastewater is among the major chunks of polluted water that requires treatment before being discharged into the waterbodies (streams/rivers/lakes/groundwater) or for its reuse in the ancillary processes. The present and conventional methods to treat industrial wastewater have been challenging in every aspect. There have been several shortcomings in the treatment process leading to improper treatment, leaving the treated water still polluted and unfit for reuse.
All effluents are often treated using similar protocols and the use of large amounts of chemicals leads to heavy quantity of sludge. There is a heavy reliance of biological treatments without realizing the varied nature of streams from acidic to basic and the different nature of effluents. Industrial wastewater is treated in several steps from the primary to the tertiary. Broadly, the water initially is passed through sand and iron filters. The polluted water, being full of heavy contaminants often chokes the membranes and hamper the process. The water then is further treated with Reverse Osmosis (RO) and Multi Effect Evaporator Drying (MEE). This also generates a lot of reject water.
The Government of India mandates all the industries to treat their wastewater to a level where it can be further reused in the process. To achieve this compliance, industries are liable to achieve Zero Liquid Discharge (ZLD) which has high operational expenditure and is also highly resource and energy intensive. The process of use of MEE requires huge amount of steam which is obtained from the burning of coal. Thus, this tertiary treatment is often challenging for the industries to achieve and the entire process is highly unsustainable in India.
To address these challenges in industrial wastewater treatment, the TERI Advanced Oxidation Technology, shortly known as tadox technology, has designed a system to enhance water reuse through ZLD towards making the entire treatment process more sustainable and cost effective. The tadox is equipped to treat water with high color, Chemical Oxygen Demand (COD), Total Organic Carbon (TOC) and high levels of pathogens and micropollutants. It uses technical interventions at the secondary stage of wastewater treatment to provide tadox treated water to reduce the load on the tertiary treatment.
The tdox technology addresses multiple challenges in the process of industrial wastewater treatment by substantially bringing down the color, COD, and toxicity levels. It also has added advantages of reducing the sludge generation in treatment processes and enhances the shock load bearing capacity of the systems. As the water becomes clearer post tadox treatment, there is lesser chances of the membranes being choked or fouled. It makes the achievement of ZLD cost effective while reducing the use of excessive energy and resources in the process. Thus, it is intended to make the entire process of tertiary treatment more affordable, sustainable, and compliant.

Technological Interventions

Any process which generates hydroxyl radical (OH-) is categorized under Advanced Oxidation Processes (AOPs). Depending on the source of generation of these radicals, AOPs are further classified into, chemical, photochemical, sonochemical, electrochemical, and others. Presently, chemical AOPs are there in the market. tadox focusses on the use of photochemical AOPs, particularly photocatalysts. The integration of photocatalysis in wastewater treatment is applied for the first time in India through tadox.
The tadox technology involves the use of nano materials which are UV activated (or self-activated on exposure to UV light) and generate hydroxyl radical in the presence of air and water. After primary treatment the effluent is passed through secondary treatment where it is mixed with the nano materials. It is then treated in a photocatalytic reactor having UV radiation sources. After this treatment, the nano particles are separated to enable them to be used for many cycles. This process substantially reduces the use of chemicals in wastewater treatment and considerably reduces the generation of sludge in the process. The photocatalysis also leads to the inactivation of bacteria and thus the water does not require any further disinfections. It has a unique property of breaking down the chemical bonds and macromolecules (pollutants) are broken down into smaller molecules and finally into constituent minerals. Due to this the color becomes transparent and the COD levels are lowered.

Application of TADOX technology

Based on several case studies in the past few years, it is observed that tadox can be implemented at the pre-biological, post-biological, polishing or no-biological stage of wastewater treatment. It has been highly successful in treating wastewater from chemical industries with high phenol content in the pre-biological stage of treatment. Due to high halyacidic nature of wastewater, most of the times, the biological systems are unable to take such effluents. However, tadox treatment had enabled such effluents to go into the biological systems, as it reduces the COD by 90% and improves the BOD:COD ratio (which is an indicator of biodegradability) by almost five times.
The tadox has successfully treated water from pharmaceutical industries, slaughter houses, tanneries, oil and gas industries and more. It is also observed that tadox treatment is even applicable for Municipal Sewage Discharge. It can be used either to treat the water at inlet or further treat the wastewater using conventional treatment methods. If the water is treated at the inlet using tadox, it can save huge amounts of energy and time besides the purified water can be provided to the industries for reuse.
The tadox technological interventions is recognized and awarded by several government institutions and departments including its selection in the Namami Gange initiative for the treatment of various wastewater streams. It has so far developed 35+ case studies and has established a 10 KLD water treatment plant at the TERI Gurgaon Campus.

Wastewater Mapping and Accounting

The process of wastewater treatment has suffered considerably due to a casual approach towards it with lack of commitment towards environment and lack of appreciation of the enormous benefits of its recycle and reuse. In addition, the funding constrains and lack of necessary knowledge and skills, bring challenge to proper operations and maintenance in the present approach that leads to the end of the water cycle. With the current trends of water usage, water has already become and increasingly scarce resource. People have become more and more dependent on groundwater and there is an immediate need for source diversification. In such a situation, the treated water from the Effluent Treatment Plants (ETP) or Sewage Treatment Plant (STP) becomes a crucial secondary source. Wastewater treatment should therefore be given utmost importance and be performed in a scientific and sustainable manner.
Wastewater mapping and accounting are important to improve the capacity and outcome of the treatment plants by identifying and quantifying what needs to go into the system. In most cases it is observed that the industries add the entire amount of wastewater generated into the effluent treatment plants without any idea of segregation. Streams of water which might be treated locally remain unidentified and are allowed to flow into the drainage channel. Water mapping are required to identify different wastewater streams that are generated through various units of operations and processes. It can help to quantify how much water is needed to be treated after segregation is performed. After identifying and quantifying how much water should go into the plant, it is also necessary to monitor the actual flow that is coming to the streams so that the streams can be optimized locally. Wastewater mapping, thus, involves segregating water before its treatment to help reduce the actual volumetric load to the ETPs for their better functioning and outcome.
The quantity of the produce and the quantity of the treated wastewater can also be determined numerically through wastewater accounting which helps to calculate how much water is being sent to the treatment plant or how much need to be sent after delocalizing. This helps to account/figure the actual quantity of the produce besides realize the efficiency of the wastewater treatment plant.
Wastewater mapping and accounting involves a decentralized treatment of water where a segregation of the wastewater streams is performed. In this process, the reject of one operation could be used as a feed to another operation. Treatment processes usually involve a set of filters, followed by softeners, RO, and EDI units. The EDI can get its feed from the RO and in this manner the reject can be recycled and used. Low TDS rejects from EDI and RO can also be used as feed to cooling tower. This type of treatment also uses technological interventions such as the Scale Ban Technology where the solid waste is precipitated out and the water is reused into the system.
The entire process of wastewater mapping and accounting helps to reduce the volumetric and salt load added to the ETP by segregating out water and sending only the actual quantity of effluent that needs to be treated. It further lowers the demand for freshwater by substituting freshwater with reject generated in the treatment process for the cooling towers. Therefore, simply putting a treatment plant and treating everything is neither a solution nor is a sustainable manner of treating wastewater. The root cause of wastewater must be identified to arrive at what needs to be done to treat it in order to optimize the process of wastewater treatment.

Discussion

A typical problematic scenario of industries in the country is that most of them run the ETPs only when there is an inspection. The main reason behind this is high operational costs of treatment which discourages the industries to use treatment machines regularly. This is an area of probable intervention where most cost saving technologies should come up so that the operational expenditures are reduced and wastewater treatment takes place regularly and effectively, benefitting both the environment and the society.
Another typical concern from the industries is the over extraction of groundwater, excess water used in the production process, and deep discharge of wastewater without proper treatment. Though the occurrence of such scenarios and practices have started to decline with introduction of guidelines and strict actions by the government for the industries. For example, it is mandatory for any industry extracting more than 100 cubic meters of water per day to go for accounting and auditing process. The data needs to go to a particular server and the government is putting up more stringent rules to monitor them. For example, Industries have also adapted several technologies and alternatives to save water in the production process. Water saving methods such as heap filter to cleaning, side stream filter cleaning, pressure guns and water saving guns are put to practice by many industries. Industries requiring large amounts of water for production are encouraged to judiciously use water as that will generate lesser wastewater and thus reduce loads on the effluent treatment plants. For example, the industries are now closely monitored and heavily penalized by the government for deep aquifer discharge of untreated waste water which was chronic phenomena in the past.
The tadox technology is designed to reduce the conventional stages of filtration like chemical treatment, chlorination, sand filtration etc. thus becoming more cost effective for implementation. Its upscaling for consideration of environmental safety protocols and associated risks will be crucial in the days to come. For example, the tadox has taken a simple scientific principle of photocatalysis where the properties of nano materials are harnessed but how it is being used is important. The photocatalysis unit uses nano materials which are further recovered in the process. There are risks (impact on the environment) if these nano materials bypass the recovery. From treatment to separation of particles, tadox has taken into consideration such risks with thorough research on material size, monitoring, etc. The consequences of accumulation nano materials on both terrestrial and aquatic life after its full-scale implementation after 40-50 years is well researched. It is still important to use every system with utmost responsibility. For example, although uv activated nano materials are effective in treating wastewater, their introduction into a polluted river will not help cleaning even in the exposure to uv rays from the sun. Thus, the use of nano materials must go through a proper channel and engineering starting from the mixing of nano materials to giving radiation and passing through reactor with proper Hydraulic Retention Time (HRT).
An important aspect of tadox technology that can take it far in upscaling is its plant operations that can be managed with basic knowledge of the operations backed by technical team to monitor the technical process.
The treatment and reuse of wastewater is plausible when a clear understanding of the origin of wastewater is there. For example, the wastewater from a packaging unit will differ from a pharma manufacturing unit. Since, there is a consumption point, treatment point, utility and then there's a wastewater treatment. It’s important to identify them, take out a stream and mix them to figure out the quality aspect of it and get the QA & QC (quality assurance & quality control) verified. This is crucial since if the entire production of reused water is not correctly/methodically done, the wastewater may be of bad quality and thus discarded.
The session provided insights on decoding the mysteries of functioning of the sewage and effluent treatment plants with new technology and implementation for decentralised wastewater management. It is important that such information and knowledge of treatments must be made more accessible and affordable for all industries to adopt and adapt to it. For example, to upscale the tadox technology requires dealing with the companies who manufacture/maintain/operate STPs/ETPs/CTPs because they are at the Technology Readiness Level 7 that are ready for commercialization and approaching companies for taking it as a licensee and thus become the implementing partners.
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Wednesdays.for.Water is an initiative of the WforW Foundation, a think tank, built as a citizen collective. The idea of Wednesdays.for.Water is to connect the water worries and wisdom with the water warriors through dialogues/discussions/debates. The objective is to get in conversations with policy makers, practitioners, researchers, academicians, activists, artists, besides the youth towards water conservation and management. The other team members of the WforW are, Garbhit Naik, Monica Tewari, Harshita Sehgal, Monami Bhattacharya, Anubhuti Shekhar (ED(R)C-Ahmd), Dr Fawzia Tarannum (Climate Reality India), Prof. Bibhu P Nayak (TISS-Hyd), Ganesh Shankar and Vasantha Subbiah (FluxGen-Blr), Dr Vandana Tripathi (KJS-IoM), and counting. The Wednesdays.for.Water is reachable at wednesdays.for.water@gmail.com and WforW Foundation is reachable at hellowforw@gmail.com and hello@wforw.in. The WforW Foundation social media are reachable at Instagram, Facebook, Twitter, LinkedIn.
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*Independent Scholars and Fellow at ED(R)C Ahmedabad and WforW Foundation.
**Entrepreneur, researcher, educator, speaker, mentor. Environmental Design Consultants Ahmedabad and WforW Foundation (www.mansee.in and www.wforw.in)

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