wastewater treatment methods by physical means
The methods for treating wastewater by physical means are generally divided into the following types:
1. Traditional activated sludge method
2. A/O method
3. A2/O method
4. A/B method
5. SBR method
Conventional activated sludge
The traditional activated sludge treatment method is an ancient industrial wastewater treatment process, and the key components of industrial wastewater treatment are biogas digesters and sedimentation tanks.
During the process of organic matter retention in the aeration tank, the microorganisms in the aeration tank adsorb most of the organic matter in the sewage and are oxidized into inorganic substances in the aeration tank. Then, some of the activated sludge after sedimentation in the sedimentation tank needs to be returned to the aeration tank.
The advantages of this process include high organic matter removal rate, high sludge load, small tank volume, low power consumption, and low operating cost. The disadvantages of this process are: ordinary aeration tanks occupy a large area, have high construction investment, meet the relevant indicators of national standards within a small range, are prone to sludge bulking, and have low phosphorus and nitrogen removal rates.
A/O method
The A/O method is an industrial wastewater treatment process developed on the basis of traditional activated sludge method, where A represents Anoxic and O represents aerobic. The A/O method is a type of anaerobic - aerobic biological industrial wastewater treatment process. This process effectively treats the nitrogen content in wastewater by adding a nitrification denitrification reaction system formed by aerobic and anaerobic tanks, and has a significant denitrification effect. However, the nitrification denitrification reaction system needs to be well controlled, which puts higher management requirements on the process, which has become a major drawback of the process.
A2/O method
A2/O method is also an industrial wastewater treatment process developed on the basis of traditional activated sludge method. A2/O is an anaerobic anaerobic aerobic industrial wastewater treatment process.
The A2O method has excellent phosphorus and nitrogen removal effects and is very suitable for industrial wastewater treatment that requires phosphorus and nitrogen removal. Therefore, in urban industrial wastewater treatment plants with special requirements for phosphorus and nitrogen removal, the A2/O process is generally chosen.
A/B method
The A/B method is the abbreviation of adsorption biodegradation method. This process does not have initial sedimentation, and the aeration tank is divided into two stages of high and low load, with independent sedimentation and sludge reflux systems. The residence time in the high load stage is about 20-40 minutes, mainly through biological flocculation and adsorption, while incomplete oxidation reaction occurs, removing over 50% of BOD. The B section is similar to the conventional activated sludge method and has a lower load. The efficiency of section A in AB method is very high and has strong buffering ability. Section B serves as a water outlet control and has good treatment stability. For the treatment of high concentration industrial wastewater, AB method has good applicability and high energy-saving benefits.
However, the AB method produces a large amount of sludge, and the organic matter content in stage A sludge is extremely high. Therefore, it is necessary to add sludge for subsequent stabilization treatment, which will increase certain investment and costs. In addition, due to the removal of a large amount of BOD in section A, the carbon source is insufficient, making it difficult to meet the requirements of the denitrification process. For situations with low sewage concentration, Section B is also relatively difficult and difficult to leverage.
SBR method
SBR process is the abbreviation of intermittent activated sludge process, which is a sewage biological treatment technology that operates in a certain time sequence in an intermittent manner. It is also an activated sludge industrial sewage treatment technology that operates in an intermittent aeration manner.
The biggest difference between the SBR method and traditional water treatment processes is that it divides the process units in chronological order, replacing spatial segmentation with temporal segmentation. The entire process is intermittent for a single operating unit, but it is continuous after scheduling through multiple unit combinations, achieving a combination of orderly and intermittent operations in operation.
In short
The above biological wastewater treatment methods each have their own strengths and need to be selected based on actual situations. Moreover, biological methods are more susceptible to weather conditions. It is generally recommended to add water treatment agents such as COD degradation agents and ammonia nitrogen removal agents at the back end of the process to ensure that the effluent meets the discharge standards.