I.Product Overview

High-salinity wastewater widely originates from chemical synthesis, pharmaceutical manufacturing, pesticide production, coal chemical industry, printing and dyeing, food processing, landfill leachate, and zero-discharge projects. This type of wastewater not only has high salt content but also often exhibits high COD and color. For this type of wastewater, evaporation crystallization (MVR, multi-effect evaporation, etc.) is currently the most mainstream resource recovery route—recovering condensate through evaporation and industrial salt through crystallization.

However, the evaporation process faces two long-standing key challenges:

key challenge 1: Continuous accumulation of mother liquor. COD and color-producing substances in the wastewater do not volatilize during evaporation and are entirely concentrated in the mother liquor. As the evaporation cycle continues, the COD and color of the mother liquor continuously increase, along with viscosity and boiling point, leading to decreased evaporation efficiency and increased energy consumption. To maintain system operation, a certain amount of high-concentration mother liquor must be periodically discharged as hazardous waste, resulting not only in salt loss but also high transportation and disposal costs.

key challenge 2: Poor quality and low whiteness of the evaporated salt. During the evaporation process, COD and chromogenic substances are partially carried or encapsulated into the crystalline salt, causing the industrial salt to appear yellow, black, or gray, and its purity to decrease, making it difficult to meet industrial salt standards. It can only be disposed of as low-value waste salt in landfills, significantly reducing its resource value.

This system places the electrochemical oxidation equipment before the evaporation system as a pretreatment step. Wastewater is first treated electrochemically—direct anodic oxidation and electrocatalytic generation of strong oxidizing species such as hydroxyl radicals (·OH) oxidize and decompose COD (including recalcitrant organic matter, surfactants, complexing agents, chromogenic groups, etc.) into CO₂ and H₂O; simultaneously, it completely destroys the unsaturated conjugated structure of the chromogenic groups, significantly reducing the color of the wastewater. After electrochemical pretreatment, the high-salt wastewater, with significantly reduced COD and color, enters the evaporation system, achieving the following goals: Significantly reduced production of evaporation mother liquor; Significantly improved whiteness and purity of crystalline salt; Extended evaporation system operating cycle and reduced cleaning frequency; Realized high-value recovery of salt resources rather than disposal as waste salt. The entire process consumes only electricity, introduces no chemical agents, does not increase the salt content in the wastewater (COD is mineralized into CO₂ and released, and non-coloring substances are oxidized into colorless small molecules), and produces no solid waste or concentrated water. It is an ideal "pre-treatment" unit for evaporation systems.

II. Difficulties in chemical treatment of high-salt wastewater and solutions of this equipment

III. Working Principle

After suspended solids are removed by a screen/filter, high-salinity wastewater enters an electrochemical reactor. Under the action of electrodes:

(1) Direct electro-oxidation (COD mineralization and chromophore destruction)

Organic pollutants in the wastewater (solvent residues, surfactants, complexing agents, dyes and intermediates, humic substances, etc.) directly lose electrons and are oxidized on the anode surface:

Chemical chain breakage of macromolecular organic matter → Organic acids/alcohols/aldehydes → Further oxidation to CO₂ and H₂O

Chrophore destruction → Wastewater decolorization

Aromatic ring opening → Elimination of color and COD

Direct oxidation has a mineralization effect on organic pollutants on the electrode surface, with high COD removal efficiency and controllable energy consumption.

(2) Indirect electro-oxidation (broad-spectrum oxidation dominated by ·OH and active chlorine)

The anodic electrolysis of water generates hydroxyl radicals (·OH), which utilize the naturally occurring high concentration of chloride ions (one of the main components of salts) in the wastewater to generate active chlorine (Cl₂, HOCl, OCl⁻):

The hydroxyl radicals indiscriminately oxidize various organic compounds, especially aromatic and heterocyclic recalcitrant COD contributors.

Active chlorine further diffuses into the solution, supplementing the oxidation of organic pollutants that did not directly contact the anode.

Indirect oxidation ensures uniform removal of COD and complete elimination of color in all areas of the reactor.

The synergistic effect of direct and indirect oxidation achieves maximum coverage of different types of organic compounds, ensuring that both COD removal rate and decolorization rate meet the standards.

(1) Key effect: "Reducing the burden" of the evaporation system rather than "transferring" it

The final products of COD oxidation are CO₂ and H₂O—CO₂ escapes into the gas phase in gaseous form, and H₂O evaporates into condensate with the evaporation system. Neither COD nor color remains in the mother liquor or crystallized salt. The small molecules (usually colorless organic acids) resulting from color degradation are carried away by the mother liquor in minimal quantities during evaporation, thus not affecting the whiteness of the salt.

In short: The electrochemical unit ensures that COD and color "leave" the salt system in gaseous and colorless forms before evaporation, leaving a purer, whiter salt and less mother liquor.

IV. Core Advantages (Targeting the Resource Utilization of High-Salinity Wastewater)

V. Technical Parameters (Customizable)

VI. Applicable to specific scenarios of high-salinity wastewater resource utilization

VII. Process Location

Option 1: Pre-treatment before evaporation

High-salinity wastewater → Equalization tank → SS removal (precipitation or filtration) → pH

adjustment → Electrochemical pretreatment equipment (COD and color removal) → Evaporation system (MVR/multi-effect evaporation) → Crystallized salt + condensate (recycled after meeting standards)

Explanation: The electrochemical equipment is placed before the evaporator as a "refining" step. The wastewater, after SS removal, undergoes significant COD and color removal via electrochemical treatment before entering the evaporation system. The evaporation system treats "clean brine," resulting in high evaporation efficiency, low mother liquor, and high-quality salt. This is currently the most valuable incremental process configuration in zero-discharge and high-salinity resource utilization projects.

Option 2: Mother liquor reduction (for existing evaporation systems)

Evaporation system → Evaporation mother liquor (high COD, high color, high viscosity) → Electrochemical treatment equipment (removal of enriched COD and color) → Return to the evaporation system for further evaporation (or partial discharge)

Explanation: For existing evaporation systems, the continuous enrichment of COD and color in the mother liquor is the biggest operational challenge. A small electrochemical treatment unit can be added to the mother liquor circulation pipeline to continuously or intermittently circulate and treat the mother liquor, removing and enriching COD and color online, maintaining the mother liquor in a low COD and low color state for a long time, and significantly reducing the frequency of mother liquor discharge. This method does not change the original main process, requires low investment, and yields quick results.

Option 3: Direct Resource Utilization of Raw Water High-salt organic wastewater → Filtration → Electrochemical treatment equipment (COD removal to ≤200 mg/L, complete decolorization) → Evaporation and crystallization → Refined industrial salt + Reclaimed water