Case Study | 100 T/D Triple-Effect Evaporative Crystallizer for Sodium Chloride Wastewater — Zero Liquid Discharge & Salt Recovery

Project Overview

Background & Challenge

A chemical manufacturer specializing in raw material processing generates approximately 100 tons of high-salinity wastewater per day. The wastewater contains 8–12% sodium chloride, along with trace organic impurities carried over from the production process.

The client faced three critical challenges:

1. Strict environmental regulations – Direct discharge of saline wastewater was no longer permitted; a zero liquid discharge solution was required.

2. High operating cost risk – Evaporating 100 tons of water daily is energy-intensive; without an efficient multi-effect design, steam consumption would make the project economically unviable.

3. Salt quality requirements – The recovered NaCl needed to meet purity standards for reuse as an industrial raw material, not merely for disposal as solid waste.

Our Solution

After laboratory testing and process simulation, we designed and delivered a complete triple-effect evaporative crystallization system with the following configuration:

• Three-effect falling film evaporator for pre-concentration of the dilute brine, utilizing secondary vapor from each effect as the heating medium for the next, reducing live steam consumption by over 60% compared to single-effect operation.

• Forced circulation crystallizer (FC) as the final effect, producing uniform NaCl crystals and preventing scaling on heat transfer surfaces.

• Mother liquor recycling system ensuring complete crystallization and maximizing salt recovery.

• Centrifuge and dryer package for solid-liquid separation and production of dry, packaged salt.

• Automatic CIP cleaning system and advanced PLC control, enabling continuous, unattended operation with real-time monitoring of concentration, density, and crystallization status.

To address the trace organics in the feed, we incorporated a pretreatment unit with pH adjustment and filtration, protecting the evaporator from foaming and fouling.

Results & Performance

The system has been running continuously and stably since commissioning, achieving all project targets:

✅ Zero liquid discharge achieved – All wastewater is converted into two outputs only: distilled water and dry salt. No liquid effluent leaves the plant.

✅ High-quality distillate – The recovered condensate meets reuse standards and is recycled back into the production process, reducing fresh water consumption by over 90%.

✅ NaCl purity ≥ 99.5% – The recovered salt meets industrial-grade quality standards and is sold as a valuable by-product, creating an additional revenue stream that offsets operating costs.

✅ Energy efficiency – Triple-effect design with thermal vapor compression keeps steam consumption at approximately 0.28–0.30 tons of steam per ton of water evaporated, roughly one-third of a comparable single-effect system.

✅ Stable & automated operation – With PLC control and automatic density-based discharge, the system operates 24/7 with minimal manual intervention and a cleaning cycle of several weeks between washes.

Customer Feedback

“The system has operated stably for over a year, fully meeting our ZLD compliance requirements. The recovered salt quality exceeded our expectations — what was once a wastewater disposal cost is now a sellable product.”

Conclusion

This 100 T/D triple-effect evaporative crystallization project demonstrates that with proper process design, wastewater treatment can be transformed from a cost center into a value-generating process. By combining energy-efficient multi-effect evaporation with crystallization technology, the client achieved full regulatory compliance, significant water savings, and a high-purity NaCl by-product.

Facing similar high-salinity wastewater challenges? Contact our engineering team for a free feasibility analysis and customized ZLD solution.