Industrial wastewater COD is difficult to treat?

 

The basic principles and methods of aerobic biological treatment help you understand.

 

  With the rapid development of industry, the types of wastewater are becoming more complex. Water pollution is also becoming more serious, not only affecting the environment but also gradually threatening human health and well-being.

 

  Among the current discharge standards for industrial wastewater, COD (Chemical Oxygen Demand) is often the most challenging and difficult to treat.

 

  COD is typically used as an indicator of the organic content in water. The higher the concentration of COD, the more severe the contamination of organic substances in the water.

 

  Generally, the biological treatment of COD in industrial wastewater can be carried out in two ways: aerobic, which utilizes microorganisms in the presence of oxygen, and anaerobic, which involves microbial growth in the absence of oxygen.

 

  The following outlines the basic principles and methods of using aerobic microorganisms to treat COD in industrial wastewater:

 

  Aerobic biological treatment relies on aerobic microorganisms. During the treatment process, soluble organic substances in industrial wastewater are absorbed by bacteria through their cell walls. Solid and colloidal organic materials first adhere to the outside of bacterial cells and are then broken down into soluble substances by extracellular enzymes secreted by bacteria before entering the cell.

 

  Bacteria, through their life activities such as oxidation, reduction, synthesis, and other processes, convert a portion of the organic matter in industrial wastewater into inorganic substances, while another portion of organic matter is synthesized into microbial cell substances. It can be seen that aerobic biological treatment is particularly suitable for treating dissolved and colloidal organic matter because this part of the organic matter cannot be directly removed by sedimentation methods. Instead, using biological methods, a portion of it is converted into inorganic substances, and another portion is transformed into microbial cell substances, thus separating them from the sewage.

 

In general, there are two main types of biological treatment methods for industrial wastewater COD: activated sludge method and biofilm method

 

The first type is the activated sludge method:

 

SBR stands for Sequential Batch Reactor, which is a type of activated sludge wastewater treatment technology operated using intermittent aeration. The SBR pool integrates equalization, sedimentation, biological degradation, and secondary sedimentation functions into a single system with no sludge reflux. It is suitable for wastewater systems with intermittent discharge and large flow rate variations.

 

A/O: The A/O (Anaerobic/Oxic) biological denitrification process is a wastewater treatment system composed of two parts: anaerobic and oxic reactions. Wastewater enters the anaerobic tank and undergoes sequential stages of anaerobic denitrification, oxic organic matter removal, and nitrification. The key feature of the process is pre-denitrification, where part of the water exits to the denitrification tank after nitrification to provide nitrate.

 

A/A/O or A2/O: The A/A/O (Anaerobic/Anoxic/Oxic) process, also known as the A-A-O process, essentially refers to the Anaerobic-Anoxic-Oxic method, which is a biological denitrification and phosphorus removal process.

 

The second type, biofilm methods: including biofilters, biological rotating disks, and biological contact oxidation tanks:

 

Biofilter: A biofilter is an artificial biological treatment technology developed based on the principle of self-purification of soil and the practice of sewage irrigation. It has evolved from primitive intermittent sand filters and contact filters. It consists of gravel or plastic products as fillers for biological treatment. Wastewater comes into contact with microbial films growing on the surface of the fillers, allowing for purification of the wastewater.

 

Rotating Biological Contactor (RBC): A rotating biological contactor consists of a tank and partially submerged rotating discs in wastewater. Microbial films growing on the surface of the discs repeatedly come into contact with wastewater in the tank and oxygen in the air, allowing for the purification of wastewater.

 

Biofilm Reactor: A biofilm reactor is a type of industrial wastewater treatment derived from the biofilm process. It involves filling the reactor with a certain amount of packing material. Microbial films attached to the packing material and supplied with sufficient oxygen undergo biological oxidation, breaking down organic matter in the wastewater to achieve purification goals.