From Saline By-products to Reusable Chemicals

This technology focuses on salt resource recovery within a zero liquid discharge (ZLD) system. Its core role is to provide a practical reuse route for selected sodium-chloride-rich brine or crystallized salt produced by upstream treatment processes.

Feedstock Sources

• Sodium-chloride-rich brine from bipolar membrane or other salt-conversion processes.
• RO/NF concentrate and other high-salinity brine after suitable pretreatment.
• Evaporated crystallized salt produced from the treatment of high-salinity wastewater (hereinafter referred to as “crystallized salt”), provided that sodium chloride is its main recoverable component.

Technical Overview

Process Routes

Feedstock Assessment and Required Pretreatment

Not all high-salinity brine or crystallized salt can be used directly for electrolysis. Key parameters to be assessed include sodium chloride content, hardness, iron, manganese, sulfate, fluoride, heavy metals, organic matter and other substances that may affect electrolysis efficiency, electrode life, product quality or the intended downstream use. Based on the analytical results, clarification, filtration, softening, impurity removal and concentration adjustment may be applied so that the feedstock meets the electrolysis system inlet requirements.

Services Available from SCITEC

• Feedstock analysis, laboratory testing and process-route assessment.
• Brine pretreatment and conditioning, with upstream and downstream interface design.
• On-site sodium hypochlorite generation, storage, dosing and automatic control.
• System integration, commissioning support and operating guidance for each project.

Project Reference

High-Salinity Wastewater Treatment Project at a Coal Industry Base in Shaanxi (0.8% Sodium Hypochlorite Production)

Maximum treatment capacity: 630 m³/h for the high-salinity wastewater train and 420 m³/h for the low-salinity wastewater train.

Objective: Recover saline wastewater produced as a by-product of the bipolar membrane process in the reclaimed-water system by installing an on-site sodium hypochlorite generation system, thereby delivering the dual value of wastewater volume reduction and chemical self-sufficiency.

Solution: The plant generates concentrated brine containing 5–6% sodium chloride at an average rate of 15.5 t/h. A SCITEC 2 × 20 kg/h sodium hypochlorite generation system converts 0.25 t/h of this brine into 0.8% sodium hypochlorite solution for cooling-water disinfection within the plant. The system uses new, advanced equipment configurations, and the project design strictly follows the applicable requirements of the coal chemical industry.

Results: The project established a resource-recovery route for brine produced by reclaimed-water treatment in the coal deep-processing industry. It both reduces the volume of saline wastewater requiring disposal and replaces externally purchased sodium hypochlorite, delivering environmental and economic benefits. The project provides a replicable engineering reference for water recycling and higher-value utilization of saline by-products in the coal chemical sector.

Sodium Hypochlorite Generator Drawings and Process Flow