Zero Liquid Discharge System – The revolutionary way to treat wastewater

Big industries are often responsible for not just using the precious freshwater for their various processes and leaving less of it for other uses, but also for releasing that contaminated residual wastewater into the environment. Zero Liquid Discharge (ZLD) system is a process where all the liquid waste is removed at the end of an industrial process. The wastewater treated in the zero liquid discharge system can be reused in the industrial processes or for other purposes such as irrigation, cleaning etc. As the name suggests, there is zero discharge of wastewater into the environment. The solid waste left out as a part of the decontamination process can be used for other purposes in other industries or can be easily disposed of.

Why Zero Liquid Discharge system?

• Water is a scarce natural resource, and its huge quantity being used for industrial processes and the residual, harmful wastewater being thrown back into the environment is highly detrimental and needs to be changed.
• The water thus treated can be reused, making it more economical to using freshwater for various industrial processes.
• Industries now have an obligation towards their countries, communities and environment to treat the wastewater generated in their premises for harmful contaminants before they release it into the water bodies.
• Zero Liquid Discharge system can be costly but after doing a cost-benefit analysis, it may prove to be a much economical option than to transport that water to long distances and increase not just costs but also carbon footprint.
• About 95% of wastewater can be saved through ZLD systems and put to reuse
• Only residual is solid waste that can be disposed off

Zero liquid discharge systems can prove to be high on both CAPEX and OPEX owing to the complexities involved in personalizing the system to suit the needs of a particular business. However, all the costs seem justified given the sheer quantity of freshwater saved through this process as well as the opportunity cost of using the recycled water back in the industrial processes.

Zero Liquid Discharge systems can be used for treatment and water recycling of industrial contaminants in the following industries, amongst many others:

• Petroleum and petrochemicals
• Power plants
• Fertilizer
• Mining
• Pulp and paper
• Chemical
• Oil refineries
• Metal
• Heavy goods industries

What’s included in a Zero Liquid Discharge system

What’s needed in a ZLD system depends on every business, the kind of impurities and dissolved substances present in the wastewater.

However, broadly, following can be a part of a Zero Liquid Discharge system:

• Clarifier – Used to filter out metals, silica
• Chemical feed – Used to coagulate or concentrate metals and suspended solids
• Filter – Used to coagulate secondary solid waste
• Ultra-filtration (UF) - Used to remove any leftover suspended solids, as well as corrosion
• Reverse Osmosis (RO) - Used to remove dissolved solids
• Brine concentrator – Used to remove dissolved solids, especially brine with high salt content
• Evaporator – For evaporating excess water
• Crystallizer – To boil off any leftover liquid, with only dry solids left for final disposal

These wastewater treatment stages during ZLD system may vary depending on the application.

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