High COD levels are commonly found in the wastewater emissions of the chemical industry, including coking wastewater, papermaking wastewater, textile wastewater, dyeing and finishing wastewater, petroleum wastewater, and waste leachate from garbage.
Definition of High COD Wastewater
High COD wastewater, also known as high-concentration organic wastewater, refers to wastewater with a COD concentration exceeding 2000 mg/L, typically from chemical industry effluents. The wastewater discharged during industrial treatment often far exceeds this standard, with some process effluents in certain industries even surpassing 10,000 mg/L.
High COD wastewater treatment methods
High COD wastewater treatment methods are generally divided into three major categories: physical-chemical methods, biological methods, and electrochemical methods. I will exemplify one representative method from each major category here.
1. Adsorption Method - This method employs porous solid materials to adsorb one or more substances from wastewater onto their surfaces, thereby removing them. Common adsorbents used in wastewater treatment include activated carbon, carbon fiber, silica, diatomaceous earth, and resins, all of which can serve as adsorbent materials. This approach is cost-effective and yields good results, effectively reducing COD levels, decolorizing and deodorizing wastewater to make it reusable. However, the adsorbents require regular replacement after a period of use.
2. Biofilm Method - The biofilm method is a process that uses the biofilm formed by microorganisms on the surface of solid media to treat wastewater. During wastewater treatment, organic matter in the wastewater is continuously adsorbed and decomposed by the biofilm within the microbial metabolism, achieving the goal of wastewater purification. This method produces less sludge, avoids sludge expansion, and has good adaptability to fluctuations in water quality and quantity.
3. Electrochemical oxidation method, which is divided into two types: direct electrolysis and indirect electrolysis, primarily aimed at removing refractory organic substances from wastewater. Direct electrolysis involves the anodic oxidation of pollutants in wastewater; indirect contact utilizes intermediate substances with strong oxidizing properties produced by the anode reaction as reactants or catalysts, directly oxidizing organic pollutants in the wastewater to achieve purification.
4. Evaporation Concentration Method – This method, also a popular treatment approach in recent years, involves using the principle of evaporation. After heating the waste liquid, it is sent to an evaporator for concentration. The solid produced from the evaporation crystallization of water and wastewater is then separated and dried for reuse. This method is energy-efficient, adaptable to significant changes in water quality and quantity, requires minimal equipment investment, can save over 50% in floor space, has low operational requirements, and reduces personnel through automated systems. It is considered an excellent treatment method in wastewater systems.
Equipment Manufacturer
Zhongke Guosheng is a team jointly established by Guangzhou Zhongkang Environmental Protection and the Chinese Academy of Sciences, specializing in the treatment of high-concentration and difficult industrial wastewater. It is applied in the treatment of high-concentration wastewater from petrochemicals, food breeding, surface treatment, dyeing and papermaking, garbage leachate, and hazardous waste industry organic solvents. It provides more options for wastewater solutions, significantly reduces costs for owners, and contributes to green environmental protection and energy conservation.
