Key Challenges in the Treatment of High-COD Wastewater

The challenges of treating high-COD (Chemical Oxygen Demand) wastewater are mainly reflected 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 reaching tens of thousands or even hundreds of thousands of mg/L. These organics are diverse in type and complex in structure, making complete degradation difficult.

Poor Biodegradability:

Some organic compounds are refractory, such as certain dyes, pesticides, and pharmaceutical intermediates. These substances are difficult for microorganisms to degrade effectively during biological treatment, requiring advanced or intensified treatment technologies.

2. Treatment Cost and Efficiency

High Treatment Cost:

Effective treatment of high-COD wastewater often requires the combined use of multiple processes, including physical, chemical, and biological treatments. This results in high capital investment as well as increased operation and maintenance costs.

Low Treatment Efficiency:

The complex composition of organic matter may cause mutual interference during treatment, reducing overall efficiency. In addition, by-products such as excess sludge require further treatment, increasing both technical complexity and cost.

3. Reuse of Treated Water

Strict Reuse Standards:

To enable water reuse, treated effluent must meet stringent quality standards. However, even after treatment, high-COD wastewater may still fail to meet high-grade reuse requirements. 

Complex Reuse Technologies:

Achieving water reuse often requires advanced treatment technologies, such as tertiary treatment or membrane separation, which involve high complexity and cost.

4. Secondary Pollution During Treatment

Sludge Management Issues:

Biological treatment generates large amounts of sludge containing organic matter and heavy metals. Improper handling may lead to secondary environmental pollution. 

Use of Chemical Reagents:

Chemical treatment requires substantial amounts of reagents, which may produce toxic by-products (e.g., chlorinated hydrocarbons), posing potential risks to the environment and human health. 

5. Unstable Wastewater Quality

Complex and Variable Composition:

High-COD wastewater varies widely in pH, salinity, and heavy metal content, making process control more difficult. 

Strong Fluctuations:

Wastewater quality and flow rate often fluctuate with production conditions, requiring treatment systems with strong adaptability and operational stability.