Challenges in Treating High COD Wastewater
The challenges in treating high COD (Chemical Oxygen Demand) wastewater mainly lie in the following aspects:
1. Efficient Degradation of Organic Matter
High Organic Concentration: High COD wastewater contains extremely high concentrations of organic matter, with COD levels potentially reaching tens of thousands or even hundreds of thousands of milligrams per liter. These organic substances are diverse and complex in structure, making them difficult to fully degrade.
Degradation Difficulty: Some organic substances are particularly difficult to degrade, such as certain organic dyes, pesticides, and pharmaceutical intermediates. These substances are hard for microorganisms to effectively break down during biological treatment, requiring more advanced treatment technologies.
2. Treatment Costs and Efficiency
High Treatment Costs: To effectively treat high COD wastewater, multiple treatment technologies may need to be used in combination, such as physical treatment, chemical treatment, and biological treatment. The equipment investment and operation/maintenance costs for these technologies are generally high.
Low Treatment Efficiency: Due to the complexity of the organic substances in high COD wastewater, there may be mutual interference during the treatment process, leading to reduced overall treatment efficiency. Additionally, by-products such as sludge generated during the treatment process also require further treatment, increasing both the difficulty and cost of the process.
3. Post-Treatment Water Reuse
High Reuse Standards: To achieve water resource recycling, the treated water needs to meet certain reuse standards. However, even after treatment, high COD wastewater may still fail to meet the required standards for some high-level reuse applications.
Complex Reuse Technologies: Achieving water reuse from high COD wastewater may require advanced water treatment technologies, such as advanced treatment and membrane separation technologies. These technologies are both complex and costly.
4. Secondary Pollution during the Treatment Process
Sludge Treatment Issues: During biological treatment, large amounts of sludge are generated. These sludges contain significant amounts of organic matter, heavy metals, and other harmful substances. If not treated properly, they can cause secondary pollution to the environment.
Chemical Reagent Use: In chemical treatment processes, large quantities of chemical reagents are required. These reagents may generate toxic and harmful by-products, such as chlorinated hydrocarbons, which pose potential threats to the environment and human health.
5. Water Quality Instability
Complex Composition: High COD wastewater has a complex composition, with significant variations in pH, salinity, and heavy metal content. This makes the treatment process difficult to control, increasing the treatment challenges.
High Variability: The quality and volume of wastewater often fluctuate with changes in production conditions, requiring the treatment system to have strong adaptability and stability.
