Wastewater treatment COD issues cannot be resolved solely by physical and chemical methods. Besides, biological treatment is the most effective green technology.

 

Biological treatment principles

 

  Effectively treating industrial wastewater is a pressing concern. COD (Chemical Oxygen Demand) is an indicator used to measure the organic content in wastewater; high COD levels can lead to significant environmental pollution. Thus, utilizing biological treatment methods for COD removal has become a widely used and efficient approach.

 

  Biological treatment involves the use of microbial metabolism to break down and transform organic substances in wastewater. Biological treatment methods include aerobic and anaerobic processes. Aerobic treatment requires the presence of oxygen, breaking down organic matter into CO₂ and H₂O:

 

                       C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O

 

  Anaerobic treatment, on the other hand, operates without oxygen and converts organic matter into methane and CO₂:

 

                      C₆H₁₂O₆ → 3CO₂ + 3CH₄

 

Advantages of Biological Treatment

 

  Biological treatment offers advantages like lower costs, ease of operation, and minimal secondary pollution. Additionally, the generated biomass during biological treatment can be further recycled as fertilizer or fermentation material. For high COD content in wastewater, biological treatment methods effectively reduce COD. Common biological treatment methods include activated sludge, aerated biofilters, and immobilized cell systems.

 

1. Activated Sludge Process

 

  Among these, the activated sludge process is a commonly used method for COD removal. In an activated sludge reactor, microorganisms and wastewater are mixed, with microorganisms utilizing organic substances for growth and decomposition. Under aerobic conditions, microorganisms metabolize organic matter, producing carbon dioxide and water:

 

                           C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O

 

  Enhanced mixing and aeration are necessary in the activated sludge process to increase the contact between microorganisms and wastewater, thus promoting microbial growth and metabolic reactions for improved COD removal efficiency.

 

2. Aerated Biofilter Process

 

  The aerated biofilter process is another common biological treatment method for COD removal. This method involves passing wastewater through a media layer and a microbial growth layer. Air is injected through an aeration device to provide the required oxygen for microorganisms. Microorganisms consume organic matter for growth and metabolism, producing carbon dioxide and water:

 

                           C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O

 

  The media layer provides a large surface area for increased microbial-wastewater contact, boosting COD removal efficiency. Furthermore, the media layer forms a biofilm, promoting stable microbial communities and further enhancing COD removal efficiency.

 

3. Immobilized Cell Systems

 

  Immobilized cell systems fix microorganisms onto carriers like polymers, porous ceramics, or glass. Wastewater passing through the immobilized microbial layer undergoes growth and metabolism, producing carbon dioxide and water:

 

                           C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O

 

  The immobilized microbial layer offers a stable microbial environment, preventing settling and loss of microorganisms as in activated sludge and aerated biofilter processes. Additionally, this method can handle wastewater at lower hydraulic loads, reducing operational and maintenance costs.

 

  In conclusion, biological treatment methods are cost-effective and efficient approaches for COD removal, including activated sludge, aerated biofilters, and immobilized cell systems. These methods can be combined with other physical and chemical treatment methods to enhance COD removal efficiency. Selection of the appropriate biological treatment method should consider wastewater characteristics and treatment requirements, alongside regular maintenance and operation to ensure treatment effectiveness and economic benefits.

 

  It's important to note that biological treatment methods require regular maintenance and operation to ensure proper microbial growth and metabolic reactions. Additionally, when treating high COD-concentration wastewater, by-products such as ammonia and nitrates may be generated and require further treatment.

 

  In summary, biological treatment methods, including activated sludge, aerated biofilters, and immobilized cell systems, offer an economical and effective approach for COD removal. These methods can be combined with other physical and chemical treatment methods to enhance COD removal efficiency. When applying these methods, suitable biological treatment options should be chosen based on wastewater characteristics and treatment requirements, alongside regular maintenance and operation to ensure treatment effectiveness and economic benefits.

 

Actual case study of aerobic microbial bacteria

 

   Next, we will introduce a practical case study of our KB-660W-100 hydrocarbon-degrading bacteria