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Zero Liquid Discharge (ZLD)

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Zero Liquid Discharge (ZLD):

Introduction:
Zero-liquid discharge is a water treatment process in which all wastewater is purified and recycled; therefore, leaving zero discharge at the end of the treatment cycle. Zero liquid discharge is an advanced wastewater treatment method that includes ultrafiltration, reverse osmosis, evaporation/crystallization, and fractional electro-deionization.

Treatment Process

A well-designed Zero Liquid Discharge System (ZLD System) is used to minimize the volume of liquid waste that requires treatment, while also producing a clean stream suitable for use elsewhere in the plant processes.

A common ZLD approach is to concentrate the wastewater through well designed multiple membrane systems and then dispose of it as a liquid brine or further crystallize the brine to a solid. A typical evaporator (MEE) uses tube-style heat exchangers. The evaporated water is recovered and recycled while the brine is concentrated to a higher solids concentration. Concentrated brine treatment is done in a crystallizing system, such as Agitated Thin Film Dryer (ATFD) or a spray dryer. Crystallized solids in most of the cases is categorised as hazardous waste and disposed off periodically. We offer our clients Zero Liquid Discharge Systems designed on advanced user friendly technologies.

zero-liquid-discharge
ZLD System benefits:
  • Elimination of pollution discharge concerns
  • Elimination of regulatory disposal norms
  • Almost 98% good water recovery
  • Self-sustainable water usage industry
  • Meets social responsibility
  • Reduction of dependence on water supply source agency
Process Overview of Zero Liquid Discharge System:

ZLD Pretreatment Stage: ZLD Pretreatment Stage is one of the most important treatment stage. We offer reliable ZLD pretreatment system includes Electro Chemical Treatment, Lime Soda Ash Softening, Advanced Biological treatment like MBR (Membrane Bio Reactor).

ZLD recycle water stage: Multistage RO Membrane System is commonly used in ZLD recycle system for recovering low TDS (less saline) water from high TDS (high saline) water. However, RO Membrane System is prone to frequent fouling and requires highly stringent feed water conditioning.
We also offer advanced treatment technology EDR (Electro Dialysis Reversal) in place of Multistage RO and consistently can achieve 90% or more water recovery, EDR ensures high water recovery & lesser waste water generation. The EDR capex paybacks is achieved at times in less than 02 years.

ZLD Evaporation Stage: Final concentrated reject water generated from Multistage RO or EDR is evaporated by suitable thermal or non-thermal treatment process. Most common evaporator used is MEE (Multi-effect Evaporator) followed by Salt Crystalliser, Agitated Thin Film Dryer (ATFD) or Pusher Centrifuge System.
For lower operating expenses, MVR technology (Mechanical Vapor Recompression) is most suitably used. MVR technology adoption is ideal for cases with higher waste water volumes to be handled through ZLD process.
For intensive solar radiation available locations MD (Membrane Distillation) evaporation technology can be offered with minimal running cost.

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