Zero Liquid Discharge
Zero Liquid Discharge — No Effluent, Full Compliance, Buyer-Ready
Hydro Engineering Solutions designs and builds Zero Liquid Discharge systems that treat and recycle all process wastewater — so no liquid effluent is discharged to drains or waterways. Increasingly mandatory for Bangladesh's textile suppliers to European and American fashion brands.
Liquid Discharge
Zero — 100% recycled
Water Recovery
95 – 99%+
Key Technologies
MBR · RO · MEE · Crystalliser
Sectors Served
Textile · Denim · Tannery · Chemical
Compliance Met
DoE · ZDHC · EU buyer audits
Residual Output
Dry salt/solid cake only
How It Works
The ZLD treatment train
ZLD achieves total wastewater elimination by cascading biological treatment, membrane separation, and thermal evaporation — recovering water at every stage until only a dry solid residue remains.
Primary & Biological Treatment
Conventional treatment removes gross solids, colour, and organic load (BOD/COD) before the water enters the membrane system. Biological treatment is critical to prevent fouling of downstream RO membranes.
Membrane Bioreactor (MBR)
MBR combines activated sludge treatment with ultrafiltration membranes to produce a consistent, high-clarity permeate — the ideal feed for the RO concentration stage. BOD and TSS are reduced to near-zero.
High-Recovery Reverse Osmosis
Multiple-stage RO concentrates the MBR permeate, recovering 75–85% as clean water for process reuse. The RO concentrate — now a small, high-TDS stream — advances to thermal evaporation.
Multiple Effect Evaporation (MEE)
The RO concentrate is fed to a multi-effect evaporator where steam evaporates water vapour from the saline concentrate. Each effect reuses the vapour from the previous stage, reducing energy consumption.
Crystallisation
The concentrated brine from MEE is fed to an agitated thin-film dryer or forced-circulation crystalliser where the remaining water is evaporated and the dissolved salts crystallise into a dry, manageable solid.
Condensate Recovery & Reuse
Water vapour evaporated in MEE and crystallisation condenses and is recovered as high-purity condensate — returned to the process or used as boiler feed water, closing the water loop completely.
Industries
Who needs ZLD in Bangladesh?
ZLD is increasingly required by EU and North American brands as a condition of their supplier contracts, particularly in sectors where dyeing, printing, and chemical processing generate high-TDS, coloured, or toxic wastewater.
Denim & Indigo Dyeing
Indigo dye and desizing wastewater contains colour, BOD, and TDS that European brands increasingly require to be fully recycled — zero discharge.
Textile Wet Processing
Reactive, disperse, and vat dyeing wastewater from knit and woven fabric processing lines require ZLD for ZDHC MRSL compliance.
Leather & Tannery
High-strength tannery wastewater containing chromium, sulphide, and salt requires ZLD treatment to meet Hazaribagh relocation and export market requirements.
Chemical Manufacturing
Specialty chemical processes generating hazardous, high-TDS, or solvent-containing wastewater where discharge is prohibited by DoE permit conditions.
Power Generation
Cooling tower blowdown and boiler blowdown treatment and recovery at power stations to meet zero liquid discharge conditions imposed by water body proximity.
Pharmaceutical API
API manufacturing solvent and process water recovery to meet WHO-GMP environmental requirements and minimise pharmaceutical contamination of local water bodies.
Technical Specifications
Design parameters
| Parameter | Typical Range |
|---|---|
| Overall Water Recovery | 95 – 99%+ of inlet flow |
| Liquid Discharge | Zero (100% recycled or evaporated) |
| RO Recovery (within ZLD) | 75 – 85% |
| MEE Steam Economy | 3 – 8 kg water evaporated/kg steam |
| Condensate Purity (TDS) | < 50 mg/L (boiler-quality) |
| Solid Residue | Dry salt/cake for disposal or sale |
| Inlet COD (max) | Up to 5,000 mg/L (post-biological) |
| Inlet TDS (max) | Up to 60,000 mg/L (evaporator feed) |
| Energy Consumption | 100 – 300 kWh/m³ (feed-dependent) |
| Evaporator Capacity | 1 – 500 m³/hour (site-specific) |
Why Hydro Engineering Solutions
ZLD designed to satisfy buyer audits — not just DoE
Effluent characterisation before design
ZLD system performance depends entirely on the wastewater chemistry. We characterise your effluent fully — TDS, organic load, colour, scaling indices — before specifying the MBR, RO, and evaporator.
ZDHC & EU buyer documentation
We prepare the technical documentation that EU and US brands require from their suppliers — process flow diagrams, water balance reports, and monitoring data — so your audit response is ready.
Energy optimisation
ZLD is energy-intensive by nature. We design MEE systems with the optimal number of effects for your effluent volume and energy cost — and integrate heat recovery to reduce operating cost.
O&M support after commissioning
ZLD plants require skilled operation. Our annual maintenance contracts include scheduled inspection, membrane replacement, evaporator descaling, and emergency support — keeping your plant compliant year-round.
Get Started
Achieve zero liquid discharge — and keep your buyers
Share your current treatment situation, buyer requirements, and wastewater characteristics. We'll design a ZLD system that satisfies your audit obligations and operates reliably year-round.
- ✓Wastewater characterisation and water balance
- ✓ZLD vs MLD feasibility comparison
- ✓MBR + RO + MEE system design
- ✓ZDHC and buyer audit documentation support
Request a Free Consultation
No obligation. Our engineering team responds within 1 business day.