Electrochemical wastewater treatment equipment, used for treating fine chemical

Product Specification

I. Product Overview

Fine chemical wastewater is one of the most challenging types of industrial wastewater treatment. Fine chemicals encompass numerous sub-sectors, including pharmaceutical intermediates, pesticide intermediates, dyes/pigments, surfactants, fragrances and flavors, electronic chemicals, water treatment agents, adhesives, and coating additives. Its wastewater exhibits distinct industry characteristics: a wide variety of products, complex production processes, and frequent batch changes—leading to diverse wastewater sources, extremely complex compositions, and drastic fluctuations in water quality and quantity; extremely high COD concentrations; the presence of large amounts of recalcitrant aromatic compounds, heterocyclic compounds, halogenated hydrocarbons, nitro compounds, and polymers; strong biotoxicity (many intermediates have significant inhibitory effects on microorganisms); high salt content (Cl⁻, SO₄²⁻, Na⁺, NH₄⁺, etc.); typically extremely low BOD₅/COD ratios (0.02~0.15), resulting in very poor biodegradability; and the frequent presence of organic solvents, catalyst residues, unreacted raw materials, and byproducts.

The challenges and key difficulties of treating wastewater from fine chemical industries are extremely prominent:

Frequent biochemical system failures—Residual pesticides/pharmaceutical intermediates, nitro compounds, and halogenated hydrocarbons in the wastewater are highly toxic to activated sludge. Even after hydrolysis and acidification pretreatment, the biochemical system is frequently impacted, leading to sludge bulking and even death.

Dramatic fluctuations in water quality due to product switching—Fine chemical enterprises often operate intermittently. When switching between different products, the COD of the wastewater can surge dramatically within hours, and the types of toxic substances change simultaneously, which traditional biochemical systems cannot adapt to.

Extremely poor biodegradability—Aromatic rings, heterocyclic rings, and polycyclic aromatic hydrocarbons have stable structures, with a B/C ratio often below 0.10, making them almost unusable by microorganisms.

High salinity further inhibits biochemical processes—When salinity is >3%, the osmotic pressure of conventional activated sludge systems becomes unbalanced, leading to the death of a large number of microorganisms.

This system employs electrochemical oxidation technology and can be flexibly configured in multiple stages of fine chemical wastewater treatment: For pretreatment and detoxification of high-concentration mixed raw water—it directly treats high-COD raw water (without dilution). Through direct anodic oxidation and electrocatalysis, hydroxyl radicals (·OH) and active chlorine, along with other strong oxides, rapidly attack stable structures such as aromatic rings, heterocycles, nitro groups, and halogenated groups, breaking bonds and opening rings within 1-2 hours, significantly reducing biotoxicity. The B/C ratio is increased from 0.02-0.10 to over 0.30, creating safe and biodegradable influent conditions for subsequent biological systems.

For advanced treatment of biological effluent—it deeply removes residual recalcitrant COD and color from biological effluent, stably meeting direct discharge or reuse standards, achieving zero chemicals, zero solid waste, and zero hazardous waste.

For high-salt mother liquor/evaporation pretreatment—it removes COD and color from high-salt wastewater, improves the whiteness and purity of evaporated crystallized salt, significantly reduces the discharge of evaporation mother liquor, and achieves resource recovery of high-salt wastewater.

Addressing high-concentration, intermittent emissions during product switching—this system rapidly responds to sudden changes in water quality, treating high-concentration/high-toxicity wastewater as it is generated, thus preventing disruption to the entire plant's wastewater system.

The entire process consumes only electricity, without adding any chemical agents or generating secondary pollutants such as iron sludge, saturated carbon, or concentrated liquid. It operates at ambient temperature and pressure, with a working voltage of 3-15V DC, making it safe and easy to use. The electrochemical unit can adapt to water quality changes within minutes through current adjustment, providing a key technological solution for addressing the three core challenges of "complex water quality, drastic fluctuations, and high toxicity" in fine chemical wastewater treatment systems.

II. Difficulties in fine chemical wastewater treatment and solutions with this equipment

III. Working Principle

Fine chemical wastewater enters the electrochemical reactor after being screened, settled, or filtered to remove suspended solids. Based on the characteristics of the wastewater and the treatment objectives, efficient purification is achieved through the following oxidation pathways:

(1) Direct electro-oxidation (core pathway of aromatic ring/heterocyclic ring opening and bond breaking)

A large number of recalcitrant aromatic and heterocyclic compounds in fine chemical wastewater are directly oxidized by losing electrons on the anode surface:

Aromatic compounds (benzene series, naphthalene series, biphenyls, etc.): The benzene ring is hydroxylated by active oxygen species on the anode surface, and then oxidized to open the ring, generating small molecule organic acids (maleic acid, oxalic acid, acetic acid, etc.), which greatly improves the bioavailability of microorganisms

Heterocyclic compounds (pyridine, quinoline, thiazole, furan, imidazole, etc.): Heterocyclic rings containing N/S/O are oxidized to open the ring on the anode surface, and N is released in the form of NH₃ or N₂, eliminating the cyclic biological toxicity

Nitro compounds (nitrobenzene, nitrobenzene, etc.): The nitro group is reduced at the cathode or oxidized at the anodic surface, the benzene ring is opened, and the mutagenicity is eliminated

Halogenated compounds (chlorobenzene, brominated compounds, etc.) : Carbon-halogen bonds break on the anode surface, halogens are removed in ionic form, and the biodegradability of organic matter is significantly improved after dehalogenation. Organic matter containing unsaturated bonds (olefins, alkynes, etc.): Unsaturated bonds are oxidized and broken, and converted into acids, alcohols, etc.

(2) Indirect electro-oxidation

Anode electrolysis of water generates hydroxyl radicals (·OH), and at the same time, the chloride ions naturally present in the wastewater (fine chemical wastewater generally contains Cl⁻) are electrolyzed to generate active chlorine (Cl₂, HOCl, OCl⁻):

Hydroxyl radicals perform non-selective oxidative attacks on various organic matter, especially effective for opening aromatic rings and breaking heterocyclic rings.

Active chlorine diffuses into the solution to supplement the oxidation of pollutants that have not directly contacted the anode, and efficiently removes ammonia nitrogen.

Chloride ions are recycled in the reaction and continuously participate in oxidation.

(3) Simultaneous improvement of COD reduction and biodegradability

Synergistic effect of direct oxidation and indirect oxidation: Large molecular recalcitrant organic matter → Ring opening/bond breaking → Small molecule organic acids, alcohols, aldehydes

Some organic matter continues to oxidize → CO₂ + H₂O (COD mineralization)

The treated effluent BOD₅ increases significantly (large molecules are converted into small molecule degradable substances), COD decreases, and the B/C ratio increases from 0.02~0.10 to over 0.30, providing a high-quality degradable carbon source for subsequent biochemical systems.

(4) Deactivation effect of toxic functional groups

One of the core goals of electrochemical oxidation is to precisely attack toxic functional groups to "deactivate" them—the nitro group of nitrobenzene is removed, the C-X bond of halogenated products is broken, and the heterocycle opens to release N. After the toxic groups are destroyed, even if the molecular skeleton is not completely mineralized, its inhibitory effect on microorganisms is basically eliminated, and subsequent biochemical systems can safely and efficiently continue to degrade residual small molecules.

(5) Color elimination

The chromophores are oxidized and broken, and the wastewater changes from dark to colorless or light transparent.

IV. Core Advantages (Targeting Fine Chemical Wastewater)

V. Technical Parameters (Customizable)

VI. Process Location

Option 1: Pretreatment Detoxification

Fine chemical wastewater (raw/mixed water) → Bar screen/equalization tank → Sedimentation/flotation (SS and floating oil removal) → Electrochemical treatment equipment (ring-opening, removal of nitro/halogen/heterocyclic toxicity, B/C ratio enhancement) → Intermediate tank/buffer tank → Biological system (hydrolysis acidification + A/O or A²/O) → Discharge meeting standards

Explanation: The electrochemical detoxification unit is located before the biological system, undertaking the core functions of "toxicity elimination + ring-opening + B/C ratio enhancement." This is the most critical and indispensable process in fine chemical wastewater treatment—if fine chemical wastewater without electrochemical detoxification directly enters the biological system, the system operation risk is extremely high, with frequent poisoning and collapse. After detoxification, the effluent B/C ratio is ≥0.30, the COD removal rate of the biological stage is significantly improved, and the overall system operation is stable and reliable. This configuration is particularly suitable for fine chemical enterprises with complex wastewater compositions and frequent product switching.

Option 2: Advanced Treatment to Meet Standards (For cases where COD in the effluent from biological treatment still fails to meet standards)

Fine Chemical Wastewater → Pretreatment → Biological System → Secondary Sedimentation Tank → Electrochemical Advanced Treatment Unit (Removal of Residual Stubborn COD and Color) → Compliant Discharge/Reuse

Explanation: When the COD and color of the effluent from biological treatment still cannot meet the discharge standards, an electrochemical advanced treatment unit is added after the biological system. This unit deeply removes residual aromatic polymers, humic substances, and other stubborn COD, reducing the COD to the discharge/reuse standard.

Option 3: Pretreatment Detoxification + Advanced Treatment

Fine Chemical Wastewater → Electrochemical Detoxification Unit (Before Biological Treatment) → Biological System → Electrochemical Advanced Treatment Unit (After Biological Treatment) → Compliant Discharge/High-Quality Reuse

Explanation: For newly built fine chemical wastewater treatment plants or projects with extremely strict discharge standards, an electrochemical unit is installed both before and after the biological treatment. The front end ensures the stable and efficient operation of the biological system, while the back end ensures that the effluent consistently meets the most stringent discharge standards. With the two systems working together, the system has the strongest resistance to shocks and the highest certainty in water output.