Electrochemical wastewater treatment equipment, used for petrochemical

Product Specification

I. Product Overview

Petrochemical wastewater mainly originates from two major sectors: petroleum refining (oil refining) and petrochemicals (ethylene, aromatics, synthetic resins, synthetic fibers, synthetic rubber, etc.). It is a typical type of industrial wastewater characterized by large volume, complex composition, and high treatment difficulty. Its water quality characteristics include: a wide variety of wastewater types (including process wastewater, oily wastewater, sulfur-containing wastewater, alkaline wastewater, circulating water discharge, and domestic sewage), high COD concentration, large amounts of petroleum/hydrocarbon organic matter, toxic substances such as phenols, sulfides, ammonia nitrogen, and cyanides, and recalcitrant organic matter (polycyclic aromatic hydrocarbons, heterocyclic compounds, polymer monomers, etc.), generally low biodegradability (B/C ratio 0.15~0.30), and significant fluctuations in water quality and quantity due to variations in crude oil type and processing methods.

Traditional petrochemical wastewater treatment processes typically follow a route of "oil separation → flotation → biological treatment → advanced treatment." However, in practice, this approach has long faced the following challenges: 1. Oily substances interfere with the biological treatment system—even after oil separation and flotation, residual emulsified oil and dissolved oils remain, leading to decreased activated sludge activity and deteriorated settling performance over time. 2. Recalcitrant organic matter is difficult to remove biologically—polycyclic aromatic hydrocarbons, heterocyclic compounds, and polymer monomers are highly resistant to microorganisms, limiting the removal rate of these CODs in the biological treatment stage. 3. The biological treatment system is inhibited by both sulfides and ammonia nitrogen—sulfides and free ammonia inhibit both nitrifying and heterotrophic bacteria, resulting in low efficiency of the biological treatment system. 4. Biological efficiency decreases with increasing wastewater salinity—while petrochemical wastewater is not as extreme as fine chemical wastewater, some wastewater still contains significant amounts of salt. The removal rate can reach 2%~5%, inhibiting conventional biochemical processes. Low temperatures in winter reduce biochemical nitrification efficiency, leading to lower ammonia nitrogen removal rates and a high risk of ammonia nitrogen exceeding standards in effluent. Increased demand for wastewater reuse—circulating water discharge and some compliant effluent need to be reused, but existing processes cannot guarantee the long-term stability of reused water quality. This system employs electrochemical oxidation technology, which can be flexibly integrated into multiple stages of the petrochemical wastewater treatment process:

For combined wastewater after oil-water separation and flotation—directly treats wastewater containing residual oil, phenols, sulfides, and recalcitrant organic matter, oxidizing and decomposing toxic substances within 1~2 hours, removing emulsified and soluble oils, and degrading polycyclic aromatic hydrocarbons through ring-opening. The B/C ratio is increased from 0.15~0.20 to over 0.30, creating safe and biodegradable influent conditions for subsequent biochemical systems.

For advanced treatment of biochemical effluent—deeply removes residual COD (recalcitrant polymers, polycyclic aromatic hydrocarbon ring-opening products, etc.), ammonia nitrogen, and color from the biochemical effluent, stably meeting reuse standards.

For oily emulsified wastewater, this system efficiently demulsifies and oxidizes to remove oil and COD, solving the problem of poor treatment efficacy of conventional air flotation + biological treatment for emulsified oil.

For circulating water discharge and reuse systems, this system removes COD, ammonia nitrogen, and microorganisms before reusing the water in the circulating cooling water system, achieving cascade utilization and resource recovery of water.

The entire process consumes only electricity, without adding any chemical agents (demulsifiers, flocculants, oxidants), and does not produce secondary pollutants such as chemical sludge, iron sludge, or adsorbed saturated carbon. The electrodes are designed to resist oil contamination, adapting to the complex operating conditions of oily wastewater. It operates at normal temperature and pressure (0~40℃), unaffected by seasonal and temperature changes.

II.Difficulties in petrochemical wastewater treatment and solutions of this equipment

III. Working Principle

After pretreatment such as oil separation and flotation to remove floating oil and most suspended solids, petrochemical wastewater enters the electrochemical reactor, where the following purification reactions occur under the action of electrodes:

(1) Direct electro-oxidation

Characteristic pollutants in petrochemical wastewater are directly oxidized on the anode surface:

Petroleum/hydrocarbon organics (alkanes, cycloalkanes, aromatics, etc.): Long carbon chains and cycloalkanes are gradually oxidized and broken on the anode surface, transforming into small molecule organic acids and alcohols, and finally mineralized into CO₂ and H₂O

Polycyclic aromatics (naphthalene, anthracene, phenanthrene, pyrene, etc.): Aromatic ring systems are gradually oxidized and opened on the anode surface, and polycyclic structures are opened into monocyclic or small molecule organics, eliminating biotoxicity

Phenolics (phenol, cresol, xylenol, etc.): Benzene rings are gradually oxidized and opened on the anode surface, and polycyclic structures are opened into monocyclic or small molecule organics, eliminating biotoxicity

Phenolics (phenol, cresol, xylenol, etc.): Benzene rings are opened and opened on the anode surface, transforming polycyclic structures into monocyclic or small molecule organics. After hydroxylation, the anode surface is further oxidized and ring-opened, transforming into small molecule organic acids. Heterocyclic compounds (containing N/S/O heterocycles): Heterocycles are oxidized and ring-opened on the anode surface, significantly reducing biotoxicity. Sulfides (S²⁻): Directly oxidized to sulfate ions (S²⁻→SO₄²⁻) at the anode, eliminating toxic inhibition on microorganisms.

(2) Indirect electro-oxidation: Electrolysis of water at the anode generates hydroxyl radicals (·OH), while utilizing naturally occurring chloride ions in the wastewater (petrochemical wastewater contains Cl⁻) to generate active chlorine (Cl₂, HOCl, OCl⁻), supplementing the oxidation of pollutants that cannot directly contact the anode, especially showing significant oxidation efficiency for soluble oils and recalcitrant organic matter.

(3) Demulsification and removal of emulsified oil: Emulsified oil droplets in oily wastewater carry a negative charge on their surface, forming a stable emulsion state, which is difficult to completely remove using conventional air flotation. In the electrochemical reactor: The microbubbles and electric field generated by anodic oxidation cause changes in the surface potential of the emulsified oil droplets, the double layer is compressed, the oil droplets in the unstable emulsion state aggregate and float, the dissolved oil organic matter is oxidized and mineralized, and the oil content in the effluent can be reduced to below 1~3 mg/L.

(4) Simultaneous oxidation of ammonia nitrogen and sulfides Active chlorine oxidizes ammonia nitrogen to nitrogen gas (2NH₃+3HOCl→N₂+3Cl⁻+3H₂O), and the ammonia nitrogen removal rate can reach 80%~95%. Sulfides are directly oxidized to sulfate at the anode, completely eliminating their toxicity.

(5) COD reduction and biodegradability improvement The synergistic effect of direct oxidation and indirect oxidation causes the ring-opening and bond-breaking of large molecular recalcitrant organic matter into small molecular degradable substances, and the B/C ratio increases from 0.15~0.20 to above 0.30; some organic matter is completely mineralized, which directly reduces COD and creates good influent conditions for the subsequent biochemical system.

IV. Core Advantages (Targeting Petrochemical Wastewater)

V. Technical Parameters (Customizable)

VI. Process Location

Option 1: Pre-treatment and Detoxification Before Biochemical Processing

Petrochemical Wastewater (after oil separation and flotation) → Electrochemical Pretreatment Equipment (removal of residual oil, oxidation of sulfides, ring-opening polycyclic aromatic hydrocarbons, and improvement of B/C ratio) → Intermediate Tank/Equalization Tank → Biochemical System → Secondary Sedimentation Tank → Discharge meeting standards

Explanation: The electrochemical pretreatment unit is located after oil separation and flotation and before the biochemical system, undertaking the comprehensive functions of "oil removal + desulfurization + detoxification + ring-opening + B/C improvement". This is a key guarantee for the pre-biochemical treatment of petrochemical wastewater—effectively removing residual emulsified oil and soluble oil after oil separation and flotation, oxidizing sulfides that significantly inhibit biochemical processes, degrading polycyclic aromatic hydrocarbons through ring-opening, greatly improving biodegradability, and ensuring the long-term stable and efficient operation of the subsequent biochemical system.

Option 2: Advanced Treatment of Biological Effluent

Petrochemical Wastewater → Pretreatment → Biological System → Secondary Sedimentation Tank → Electrochemical Advanced Treatment Unit (Removal of Residual COD and Ammonia Nitrogen) → Discharge to Standard/Reuse into Circulating Water System

Note: For enterprises with existing biological systems but whose effluent COD and ammonia nitrogen levels cannot meet current discharge standards, an electrochemical advanced treatment unit can be added after the biological system. No modifications to the existing biological system are required; COD and ammonia nitrogen levels will be reduced to meet direct discharge standards or reuse requirements.

Option 3: Special Treatment for Oily Emulsified Wastewater

Oily Emulsified Wastewater → Equalization Tank → Electrochemical Demulsification and Oil Removal Equipment → Effluent

Option 4: Pretreatment of High-Salinity/Alkaline Sludge Wastewater

High-Salinity Wastewater/Alkaline Sludge Wastewater → Electrochemical High-Concentration Treatment Unit → Effluent into Integrated Wastewater System/Evaporation System

Note: Alkaline sludge wastewater and electro-desalination wastewater have high salt content, high COD, and high toxicity; direct discharge into the integrated system will cause a shock. Electrochemical treatment units can be dedicated to treat this type of wastewater in batches, significantly reducing COD and toxicity before smoothly integrating it into the entire plant system, avoiding the high costs of off-site disposal, and the economic benefits remain significant.