Introduction
Zero Liquid Discharge (ZLD) means no effluent leaves your factory — all wastewater is recovered as reusable water, and remaining solids are recovered as salt or dry cake. ZLD is fast becoming a requirement for global buyers, LEED and Higg audits, and Bangladesh's tightening environmental norms.
What is a Zero Liquid Discharge plant?
A ZLD plant combines biological treatment, high-recovery reverse osmosis and thermal evaporation/crystallisation (MEE, MVR) to eliminate liquid discharge entirely. Water is recycled back into the process; salts and solids are collected for disposal or resale.
Core technologies in a ZLD train
A typical ZLD system stacks several technologies:
- Biological pre-treatment (MBR or MBBR) to reduce organic load.
- High-recovery RO to concentrate the brine.
- Multi-Effect Evaporator (MEE) for thermal concentration.
- Mechanical Vapour Recompression (MVR) for lower energy cost.
- Agitated Thin Film Dryer (ATFD) or crystalliser for solid recovery.
Why go ZLD
Beyond regulatory compliance, ZLD unlocks green-building certifications, opens the door to premium global buyers and turns wastewater from a rising cost into a recovered asset.