Zero Liquid Discharge: a solution to Zero Discharge of Hazardous Chemicals?

Zero Liquid Discharge: a solution to Zero Discharge of Hazardous Chemicals?

The use of hazardous chemicals in the textile & apparel wet processing has been under the scanner of NGOs, Fashion and Outdoor Brands & Retailers, governments (in some countries) and even consumers who are now getting interested in ‘green’ or ‘organic’ products – though this is largely focused on the food that they buy!

We know that these hazardous chemicals, that are used in a fabric mill or a dyehouse or a garment laundry or a printing unit, do not all remain on the final product – the fabric or garment – but get washed out and drained through the effluent discharged from the production factory into nearby river bodies, municipal sewers or groundwater. It is estimated that the textile industry is the third most water- polluting industry, after paper and leather.

In the past decade, there have been NGO movements across different parts of the world- and especially in the producing countries like China and India – to control these discharges of hazardous chemicals into rivers, lakes and groundwater from textile factories. Governments in China and India are clamping down on polluting factories and implementing stringent laws for wastewater discharge, which includes Zero Liquid Discharge (ZLD). The Greenpeace Detox campaign and other NGO initiatives have resulted in the Zero Discharge of Hazardous Chemicals (ZDHC) Program by Signatory Brands, which is pushing the apparel and footwear supply chain to ensure that hazardous chemicals are not discharged across all pathways, that is, end products, wastewater, sludge and air.

The story of Zero Liquid Discharge (ZLD) in India:

20(27)An interesting development happened in a small place in the South of India called Tirupur in 2010. Known as the ‘Knit City’, due to the plethora of T-Shirt processing and garmenting units located here, Tirupur’s 700–odd dyeing units were ordered to be shut down by the Madras High Court in 2011 on a petition moved by the Farmers Association in the area. The petition claimed that these units were discharging hazardous dyes and chemicals into the Noyyal River and into the surrounding farmlands and this had caused the river water and farmlands to become toxic – resulting in children developing skin problems, livestock dying after drinking water from the Noyyal River and field cultivation getting impossible due to the highly colored groundwater.  The Total Dissolved Solids (TDS) of the effluent being discharged by these units was 4000- 5000 ppm, well above the legal limit of 2100 ppm.

The closure of these 700- odd units severely impacted the USD 1.8 billion industry in this area, and even led to migration of workers and export orders from Tirupur to other cities!

The Tirupur cluster is a startling example of how sustainability gives rise to innovation and long- term environmental protection in practice. The closure of the dyeing units led to the evolution of ‘Zero Liquid Discharge’ or ZLD. Simply put, ZLD means Zero or No discharge of wastewater or any liquid effluent from a factory to the outside surroundings. The ENTIRE wastewater generated due to processes inside a factory has to be treated and RECYCLED back into the factory!

The concept of ZLD has been successfully implemented in Tirupur and subsequently in many parts of India and even at the Common Effluent Treatment Plants (CETPs) set up by the government for industrial clusters.

ZLD has its merits such as:

  • No impact on surrounding soil salinity, groundwater pollution or ecology of river bodies
  • Conservation of water resource through recovery and re-use of treated effluent
  • Recovery and re-use of salt used in the textile dyeing process

But, ZLD also has some de-merits, such as:

  • Use of higher amount of chemicals in wastewater treatment
  • Increase in energy usage
  • Generation of enormous amount of hazardous sludge and other solid waste
  • Impact on cost of processing (implementing ZLD pushes up costs by 25-30%)

In order to achieve Zero Liquid Discharge, we have to recover the water and salt separately from the effluent and reuse it in the dyeing process. This is a very complicated, tedious and expensive process, in terms of investment and running costs. We also need to apply lot of chemistry, engineering & technology know-how. As a simple explanation, the effluent is treated in an Effluent Treatment Plant (ETP) comprising Primary, Secondary and Tertiary Treatment steps. The treated water is recovered from the Reverse Osmosis Plant (RO) process during tertiary treatment phase and Salt is then recovered by using Multiple Effect Evaporation (MEE) with Crystallisation.

There is also a water loss in the treatment process and hence only about 80- 85% of the water can be recovered and re-used back in the process. The cost of this recovered water recycled into the process is always much higher than the cost of input water used from other sources. But if ZLD is viewed from an ecological, social and environmental viewpoint – and not as a Cost Centre – then it merits implementation at all factories with no access to a Common Effluent Treatment Plant.

Looking at the Tirupur ZLD success story- which is the first of its kind in the world- the Indian government has initiated a Draft regulation on 22nd October 2015, which will make ZLD mandatory for textile units having wastewater discharge of more than 25 KLD (Kilolitres per day), including re-use of the treated water back in process. No groundwater extraction will be allowed by industry except for make- up water and drinking purposes.The Bangladesh government has also announced in September 2015 that it is keen to implement Zero Liquid Discharge system in another four years in their country.

ZLD and ZDHC: what is the difference?

The Zero Discharge of Hazardous Chemicals (ZDHC) Initiative should not be confused with the Zero Liquid Discharge (ZLD) concept, although both have the same objective of mitigating the impact of hazardous chemicals used and discharged in textile wet processing facilities.

Limited to discharge of hazardous chemicals in wastewater only Considers  discharge of hazardous chemicals across ALL pathways: end-product, wastewater, sludge and air
Is an ‘end-of pipe’ solution to prevent pollution of the environment The focus is on ‘Input Chemical Management’ (using the MRSL) so that input chemicals are screened for restricted substances
Prohibits discharge  of  wastewater (and thus the hazardous chemicals) to the surroundings/environment by a factory Discharge of wastewater is not prohibited, but the hazardous chemicals in the discharged wastewater should be below the detection limits of testing laboratories
Its scope does not cover elimination of hazardous chemicals in the inventory of a facility, but only preventing release Its scope covers elimination of chemicals which intentionally use the listed Priority Chemical Group substances listed in the ZDHC MRSL
Initiated and monitored by  local Pollution Control Boards/ Governments Initiated and encouraged by global Brands & Retailers across their supply chains
Contributes to conservation of water resources by recycling of treated wastewater Does not include conservation of water resources in its scope
Is limited to Tier 2 suppliers i.e., dyehouses Is applicable to all Tiers of the supply chain


Brands and Retailers have initiated the ZDHC Program to lead the textile and apparel industry towards the goal of zero discharge of hazardous chemicals across all pathways across their entire supply chain by the year 2020.

Although Zero Liquid Discharge or ZLD is an ‘end-of-pipe’ concept to mitigate the impact of wastewater pollution on the environment and human health, it can partially help to meet the objective of ZDHC by ensuring that hazardous chemicals are not discharged through the pathway of wastewater.

ZLD has its trade-offs in terms of increased economic burden (due to high investments in the ETP technology), higher energy requirements and the generation of enormous amount of sludge (which will increase the need for secured landfills, thus putting pressure on land resources). However, ZLD is an innovation that contributes to sustainable use of water resources and prevents soil salinity, groundwater contamination and pollution of river bodies.

With the recent Indian government’s draft circular of October 2015 making ZLD mandatory for textile units discharging wastewater of more than 25 KLD, the concept of ZLD will gain more acceptance, which may lead to improvements in the technology and lower the costs. ZLD, alongwith proper input chemical management systems, could help suppliers to achieve the goal of ZDHC!

(The views and opinions expressed in this article are that of the author alone and do not reflect the position of NimkarTek or any other agency)


About author


NimkarTek Technical Services Pvt Ltd is a consultancy company providing world-class ecological and environmental solutions to the textile and leather supply chain. We provide online training through our E-Learning Platform NOTES. We also help dyehouses or garment washing units to assess and grade the facility for their chemical compliance, chemical storage and waste management systems and implement Chemical Management through our unique online tool CMS-i. We also offer Certified Chemical Management Certificate Course to develop competencies in Chemical Management.

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