Wastewater treatment and reuse – preventing pollution and conserving water in the textile industry


Introduction:

The textile industry is one of the major industrial sectors in India, contributing significantly to revenue and employment generation. At the same time, it causes severe environmental impacts by generating highly toxic wastewater during wet processing of fabrics at dye houses. This wastewater usually contains high concentration of dyes, salts, and host of other organic and inorganic compounds. If the wastewater is released untreated in the environment, it contaminates soil and water bodies in the vicinity, causing immense harm to plants, animals and as well as humans. There have been numerous reports in the media highlighting the level of pollution in rivers near textile clusters—in some cases entire stretches of river turn colours such as red or blue, owing to untreated dyes in the water. Numerous health ailments due to consumption of polluted water are reported across India every year.

At the same time, textile is among one of the highest water consuming industries—wet processing operations such as dyeing can consume between 60 to 150 litres of water per kilo of yarn. India faces uneven rainfall distribution every year, leading to floods and droughts simultaneously in different districts. This poses a challenge to the sustainability of water intensive industries such as textiles.

Thus, it is the responsibility of all stakeholders, especially the entrepreneurs/mill owners, to ensure that industries operate responsibly and aim to use water efficiently and prevent pollution by following norms set by the government bodies such the Central/State Pollution Control Board(s).

Industrial wastewater reuse – an effective strategy

Treating and reusing (recycling) of industrial wastewater and using treated municipal water are proven strategies that can help industries conserve water and reduce their pollution footprint too.

Typically, a textile wastewater treatment system comprises of primary, secondary, and tertiary treatment units to remove the pollutants from the wastewater up to the level prescribed by the state/central regulatory bodies. Although, the organic pollutants are effectively removed by the conventional treatment technologies, the inorganic salts remain in the treated wastewater, which require high-end technologies to remove them and make the water fit for reuse in industry.

Zero Liquid Discharge (ZLD) approach offers an effective albeit costly solution.

Necessity and viability of ZLD systems

Zero Liquid Discharge is an engineering approach in which the wastewater undergoes various stages of treatment essentially comprising of primary, secondary, Reverse Osmosis (RO) and thermal evaporation systems, and finally pure water and other useful resources are recovered for reuse, thus resulting in no wastewater discharge from the industry.

Generally, the need and viability of ZLD is decided by some key factors such as (i) Water cost, (ii) Water scarcity (iii) Regulations and iv) Input characteristic of the wastewater.

A ZLD based textile treatment plant can recover about 95-98% of pure water by volume and 80-90% of salts by weight from the wastewater. This makes it a highly desirable technology in the face of resource scarcity. Currently, the main drawback of ZLD systems is their prohibitive costs—a conventional tertiary treatment facility costs about Rs 4 crores per Million Litres per Day (MLD) capacity, whereas a ZLD system can cost nearly Rs 18 Crores/MLD. This huge difference in costs make it exceedingly difficult for small and medium enterprises to invest in this technology.

Entrepreneurs must also remember that ZLD is not a one-size-fit-all solution. The final choice of equipment and process flow determined by several factors such as volume of wastewater, types of salts in it, colours/dyes present, etc.

Government Support and regulations for development of wastewater treatment facilities

The Central Government as well as various state governments have several schemes and incentives that can help the industry adopt water conserving and pollution prevention measures. The Integrated Processing Development Scheme (IPDS) helps Micro Small Medium Enterprises (MSME) textile wet processing units construct common treatment facilities, extending crucial financial help to these units who often lack funds to set up individual treatment facilities.

The government sometimes needs to enact regulations to nudge the industries in the direction of environmental sustainability. Considering the detrimental impacts of textile wastewater to the environment, the Tamil Nadu Pollution Control Board (TNPCB) had mandated textile processing units in Tirupur to adopt Zero Liquid Discharge (ZLD) System based effluent treatment plants to treat and reuse the wastewater in the dyeing process. This regulation was triggered by the deteriorating water situation in Tamil Nadu, which is receiving scanty rainfall since many years.

Some state governments and municipalities have created a system in which municipal sewage water is treated up to industrial grade and supplied to clusters in the vicinity of the municipalities. The city of Surat in Gujarat is one such example.

Water stewardship – a responsibility for all

While the industry and government are the major players in water conservation and preventing pollution at a large scale, all stakeholders need to play their part in the fight against a looming water crisis around the globe. Consumers can exert a lot of influence on decision making in the private sector. If consumers demand sustainable products, i.e., products manufactured with less water, energy, less pollution, etc. and with no social injustice, brands and manufacturers will be forced to adopt good practices in their supply chains.

Water stewardship is a holistic approach that underscores the importance of collaboration among all stakeholders. Water is a critical resource that can’t be managed effectively in isolation by individual stakeholders. The private sector (industry), government bodies, consumers, and even farmers need to come together and better allocate resources and responsibilities among themselves. This approach will ensure that the future generations aren’t deprived of this precious resource

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Disclaimer

Views expressed above are the author’s own.



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