A new water reuse project in the Indian city of Chennai, to supply the automotive sector with water derived from municipal sewage, highlights the contribution reuse can make to supporting industrial water security. Dr Josef Lahnsteiner tells The Source about this latest project and wider progress with industrial water reuse around the country.
Industry needs water – a lot of it, and generally in a steady supply. But this need exists alongside other demands on precious resources.
“Whenever there is a shortage of potable supply, the municipalities cut the industrial supply first,” notes Dr Josef Lahnsteiner, R&D director of water technology company VA Tech Wabag. Responding to such concerns, it has built a number of industrial water reuse plants across India.
Rajiv Mittal, the company’s managing director and group CEO, adds: “Water is too precious to be used just once. As water managers, it is our responsibility to provide safe, clean water at an affordable price.”
Lahnsteiner has presented conference papers on the reuse projects, including one delivered at last year’s IWA World Water Congress & Exhibition in Tokyo. The most recent project to be covered is one being completed in the water-stressed city of Chennai. The scheme will process treated municipal sewage and supply it for reuse in the automotive sector.
“The major driver for industrial water recycling in India and other parts of the world is water stress,” Lahnsteiner adds.
Industrial water reuse offers a double benefit. “If industries recycle and reuse, they increase the industrial water supply security, of course. They also increase the overall water supply security, because there is more fresh water for [other uses such as] agriculture and also for potable supply,” says Lahnsteiner.
The main applications for industrial water reuse are cooling and boiler make-up water. This means there are important water quality targets to factor in, such as a need for high levels of silica removal in boiler make-up water applications, to avoid scaling.
Industry can reuse water that is recycled within an industrial facility or reclaimed from the effluent of another facility. The constant flow from municipal sewage plants presents an appealing option as another source for reuse, and this potential was exploited in an earlier reuse scheme in Chennai.
The city is the capital of the southern state of Tamil Nadu. It is home to eight million people, with the population of the wider metropolitan area totalling around 10 million. Annual rainfall is 1200-1300mm, mainly falling in the monsoon months.
According to Lahnsteiner, the total capacity of the city’s four water treatment plants is around 1,280,000m3/day. This has to be supplemented by two seawater reverse osmosis plants, each providing 100,000m3/day. City water utility Chennai Metropolitan Water Supply and Sewerage Board (CMWSSB) also operates nine sewage treatment plants across the city, with a total capacity of 822,000m3/day.
The potential to use this municipal effluent as a source for industrial water reuse projects was noted in a scheme linked to CMWSSB’s largest sewage plant, the 270,000m3/day Kodungaiyur plant. This is located close to the Manali industrial area, in the north of Chennai. The utility supplies the area with around 36,000m3/day of secondary treated effluent at a cost of €0.15/m3. Of this, 11,500m3/day is supplied to Madras Fertilizer and 1500m3/day to Manali Petro Chemicals. The remaining 23,000m3/day is supplied to Chennai Petroleum Corporation, which includes processing in an 11,400m3/day water reclamation plant supplied by Wabag and commissioned in 2007.
Regional resource limitations
Such thirst for reuse on the part of industry is being seen elsewhere in the country. The importance of the process is highlighted by the Dahej refinery and petrochemical complex of Reliance Industries, in the coastal Dahej special economic zone in Gujarat State, in the north-west of the country.
Drought is a threat in the area because annual rainfall is less than 500mm, with 80% of this falling in the monsoon months of July to September. According to Lahnsteiner, this prompted the refinery to commission a water reclamation and recycling facility at the end of 2015. This produces 43,200m3/day of reclaimed water, in terms of reverse osmosis (RO) permeate, making it the largest industrial water reclamation and recycling facility in India. This uses an advanced multiple barrier treatment system, comprising anaerobic treatment (upflow anaerobic sludge blanket technology), membrane bioreactors, and reverse osmosis as core technologies. The brine from the reverse osmosis stage is discharged to sea, with a chemical oxygen demand (COD) limit of 150mg/l. Capacity is planned to be expanded to 57,600m3/day.
Even with this extra resource, the refinery had to be shut down for several days because of severe water shortage in May 2016. Low flow in the Narmada River meant the refinery’s intake was brackish at high tide, and so unsuitable for water production. In response, Reliance had to bring in RO permeate from its Jamnagar refinery and petrochemical complex, as well as initiating a 50,000m3/day brackish water reverse osmosis plant. Meanwhile, Gujarat State recently adopted the latest version of its water reuse guidelines to further promote reuse.
Zero liquid discharge requirements
Industrial water reuse can also be driven by the need to limit the impact of industrial activity in an area. As an example, Lahnsteiner highlights the Panipat refinery and petrochemical complex of the Indian Oil Corporation in Haryana State. This was opened in 1998 and built in a rural area to support government aims of diversifying economic activity, and to support industrial goals of supplying petrol and petrochemical products to northern India. Capacity was doubled in 2006, with further enlargement and capabilities added in 2009 and 2010.
Located around 100km north-west of Delhi, this agricultural area is close to the Yamuna Canal. Its supply is mainly used for potable water production and agricultural irrigation, so it cannot receive effluent. As a result, the refinery has to comply with a zero liquid discharge requirement.
For Lahnsteiner, the Panipat refinery project highlights the three aspects of sustainability: development has to be economically sustainable, socially sustainable – shown by the number of jobs created – and environmentally sustainable. Hence the need for zero liquid discharge in a location where there is no body of water into which effluent could be directed.
A dedicated, main water reclamation plant was added with the 2006 expansion, and a further reclamation plant for the new process (a naptha cracker) was added in 2010. The main reclamation plant receives blended refinery and petrochemical used water flow, with water quality parameters such as: temperature 15-35°C, 150mg/l COD, 1786mg/l total dissolved solids (TDS), and 98mg/l silica. The treated water – 15,000m3/day of ion exchange polished RO permeate – has less than 0.1mg/l TDS and is mainly recycled as boiler make-up in the refinery power plant. The operating expenditure of this plant has been calculated as less than €0.40/m3.
The RO brine is used for refinery coke quenching. Other potential uses include blending for use in fire-fighting water, but the ultimate requirement is to achieve zero liquid discharge. Lahnsteiner explains that this is likely to require implementation of technologies offering evaporation and crystallisation. It was with this in mind, for example, that testing of vacuum membrane distillation was initiated in March 2016.
Chennai’s latest steps
The latest project in Chennai adds another variant to the range of reuse solutions that have been deployed. It is based around CMWSSB’s Koyambedu sewage treatment plant. Here, the utility is constructing a 45,000m3/day tertiary treatment plant to further treat the secondary effluent using technologies such as ultrafiltration and reverse osmosis.
The project includes a 72km transmission pipeline, which will transfer the treated water for use by industries to the south-west of the city, in Irungattukottai, Sriperumbudur and Oragadam, particularly for use in the automotive sector.
The new water reclamation plant is being built in Chennai through a contract with a consortium of VA Tech Wabag, as lead, and IDE Technologies. Award of the €80m contract was announced in March 2016 and commissioning is due this April. Under the contract, the consortium will operate the plant for 15 years. An engineering, procurement and construction contract accounts for around €53m of the project total, with the O&M activity representing around €27m.
The water reclamation plant includes the use of chlorine dioxide, direct membrane filtration, ultrafiltration, reverse osmosis, and ozone disinfection. The key parameter is for an inlet total dissolved solids of up to 1500mg/l, and with the treated water being up to 70mg/l total dissolved solids. Lahnsteiner adds that one of his presented papers concluded that ‘it can be stated that the reuse of secondary effluent represents a drought-proof water supply at relatively low cost’.
The situation in Chennai illustrates the potential for industrial reuse to support water security. Use of secondary effluent in Chennai for industrial reuse was 36,000m3/day in 2016, rising to 81,000m3/day today to include the new Chennai project. This represents approximately 10% of the total quantity of sewage generated. While this is significantly higher than urban reuse, there is substantial scope for further expansion in what is a major water-stressed urban region.
An incentive to invest
Lahnsteiner adds that, in some instances, there can be an overriding need to implement industrial water reuse. This was the case for the Panipat refinery project in Haryana State, where there are restrictions on discharge.
But this is not always the case, and Lahnsteiner has a message for industry. “Normally, the payback times in industry are very short – 3-5 years. If industry accepted longer payback periods, they would promote much more water reuse and recycling, and subsequently social and environmental sustainability.”
He notes also that the economic cost associated with having to shut down an installation because of lack of water is generally not factored into feasibility studies. “If you imagine the shutdown of a refinery, it is extremely expensive,” Lahnsteiner says. “In the future, higher security should be considered, then more reuse and recycling projects [become] feasible.”
CEO Rajiv Mittal concludes by pointing to the sustainability driver coming from the municipal side: “Sewage is a resource with economic value, not a liability. The focus has to be on resource recovery models, which contribute to the environment by reusing treated water, producing green power/bio-compressed natural gas (CNG) from biogas, and using composted sludge as manure.”
Article prepared by Keith Hayward based on background documents and comments from Dr Lahnsteiner
Gujarat’s goal of full reuse by 2030
The State of Gujarat’s Policy for Reuse of Treated Waste Water (May 2018) aims for full reuse of treated wastewater by 2030.
It highlights that, of the state’s 185 rivers, only eight are perennial and around 69% of surface water resources lie within one-quarter of Gujarat’s territory, in the centre and south of the state. A number of water programmes have been initiated, but these rely to a large extent on inter-basin transfers. ‘Developing a locally available alternative source of water or reuse of treated waste water will help to decrease dependency on inter-basin transfer of water, and improve overall water use efficiency,’ the policy document notes.
It also sets out the following vision: ‘…maximising the collection and treatment of sewage generated, and reusing the treated waste water on a sustainable basis, thereby reducing dependency on fresh-water resources; and to promote treated waste water as an economic resource.’
The key objectives are:
- To reach a minimum 80% coverage and collection of sewage in all municipal towns
- To reach a level of 100% treatment of collected sewage as per the prescribed standards
- To reuse at least 25% of fresh-water consumption from treated waste water (TWW) within the time limit set under policy by every municipal body
- To reuse 70% of TWW by 2025
- To reuse 100% of TWW by 2030.
The policy document also includes the following mandate: ‘TWW shall be used on the principle of substitution of fresh water with it… While making use of TWW, necessary care will be taken that treated waste water is not mixed with or used with potable water.’
At the launch of the policy in May last year, The Times of India reported that Gujarat chief minister Vijay Rupani said the state government planned to create a water grid for reuse of the treated wastewater from urban areas. The plan is for half of the reclaimed water to be reused in industry. It also reported that the government is intending to create up to 10 desalination plants along the state’s 1600km coastline.