Zero Liquid Discharge System

Zero Liquid Discharge (ZLD) is a water treatment process designed to completely eliminate liquid waste discharge from a system. Here are some key points:

1. Wastewater Recovery: Nearly all of the wastewater is treated and reused.
2. Concentration: Technologies like evaporation and crystallization are used to concentrate the waste.
3. Solid Waste Disposal: The remaining solids are then safely disposed of, often after being converted into dry, manageable forms.

ZLD is essential for saving water, reducing pollution risks and sustainable environmental.

Pharmaceutical industry, Oil and gas refineries, Chemical industry, Metals industry, and Cosmetics industry etc. with heavy pollution loads often required zero liquid discharge (ZLD) to meet the strict environmental regulations.

Usually, zero liquid Discharge consists of the following:

1. Wastewater Treatment: The effluent is first directed to the Effluent Treatment Plant (ETP), where it undergoes treatment to remove contaminants. Sludge is removed and thickened using sludge dewatering machine.
2. Filtration: The treated water is then transferred for further filtration through a 2 or 3-stage Recycle Reverse Osmosis (RO) system. This multi-stage filtration ensures that any remaining impurities are effectively removed.
3. Permeate Reuse: The permeate (clean water) from the RO system is re-used in various processes, contributing to water conservation and sustainability.
4. Concentrate Handling: The concentrate (wastewater with concentrated impurities) from the RO system is sent to either a Multiple Effect Evaporator (MEE) or a Mechanical Vapor Recompression (MVRE) system. These systems further concentrate the waste by evaporating the water, leaving behind concentrated waste.
5. Condensate Usage: The condensate (vaporized and then condensed water) from the MEE or MVR is collected and used as boiler feed water, ensuring efficient resource utilization.
6. Salt Disposal: The residual salts and other solid wastes from the evaporation process are safely disposed of in an environmentally responsible manner.

Various processes used in ZLD Plant:

• Effluent treatment plant (ETP)
• Recycle RO (Reverse Osmosis)
• Multiple effect evaporator (MEE) / Mechanical vapour recompression (MVRE) / Agitated thin film dryer (ATFD)
• Sludge dewatering machine
• Ultra-filtration (UF) (optional)
• Dissolved Air Floatation (DAF) (optional)

click on the each above link to know more about particular processes

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