What are the common sewage treatment processes in small towns?

Treatment process: domestic sewage inflow-grid-grit chamber-primary sedimentation tank-aeration tank-secondary sedimentation tank-(disinfection)-effluent.

The process is stable and mature, but the volume load of organic matter treatment is low and the cost is high: the cost of sewage treatment 1 m3 1200- 1500 yuan; High operation and maintenance cost: the operation cost of treating 1 m3 sewage is generally 0.6-0.8 yuan. Moreover, municipal sewage needs to be collected and transported to the sewage treatment plant through the pipe network, and the sewage treatment plant also has a certain impact on the surrounding living environment. Sludge discharged in the treatment process needs to be dehydrated before it can be disposed of.

Anaerobic treatment process of municipal sewage

The process flow is as follows: domestic sewage inflow-grid-grit chamber-upflow anaerobic reactor (UASB)- oxidation pond-effluent.

The treatment process requires less mechanical equipment, and the operation and management are simple. Therefore, compared with the traditional activated sludge process, this process can reduce the project investment and operating costs by about 38%. Excess sludge is discharged into the subsequent oxidation pond for stable treatment without sludge treatment device. The disadvantage is that the post-treatment oxidation pond occupies a large area.

Hydrolysis-aerobic biological treatment process

Process flow: raw sewage-grid+grit chamber-hydrolysis tank-aeration tank-secondary sedimentation tank-effluent, hydrolysis tank-sludge tank-sludge dewatering treatment.

The process controls the anaerobic reaction in the hydrolysis acidification stage, shortens the sewage retention time and subsequent aeration time, and reduces the investment in engineering construction. According to the sewage treatment plant with the scale of 654.38+ 10,000 tons/year, 654.38+0 cubic meters of sewage treatment project is invested in 800 yuan, and the operating cost is about 0.3 yuan. The disadvantage is that sludge needs special treatment.

sequencing batch reactor activated sludge process

The working principle of this process is to alternately realize the functions of aeration, microbial degradation and secondary precipitation in a pool to treat sewage. Sludge needs further treatment.

Advantages include: simple process, no need to build a secondary sedimentation tank, no need for sludge reflux, etc. , save investment; The treatment efficiency is high, and nitrogen and phosphorus can be removed. According to the existing project budget estimate, the investment per ton of water project is 800- 1000 yuan, and the cost per ton of water treatment is 0.2-0.3 yuan.

Oxidation ditch treatment process

Oxidation ditch is a deformation process of activated sludge treatment process. Generally, there is no primary sedimentation tank, and extended aeration is adopted. Complete aeration, biodegradation of organic matter, denitrification, secondary precipitation, etc. In the closed annular groove structure.

The advantages of this process are: strong aeration controllability, small floor space, and about 20% savings in construction investment and operation cost compared with the traditional activated sludge process. High treatment efficiency, stable operation and good denitrification effect, especially suitable for small and medium-sized sewage treatment plants.

Biofilm process

Biofilm method is to make sewage flow evenly to the biofilm on the surface of filter material, biological turntable or filler through water distributor. Biofilm has a large surface area and contains a large number of microorganisms, which can adsorb organic matter in oxidized sewage. While decomposing the organic matter, the microorganisms on the membrane multiply and grow rapidly, and the aged biofilm falls off the surface and is discharged with the water flow, thus purifying the sewage. Biofilm method includes biological aerated filter, biological turntable and contact oxidation.

Because the biofilm process has higher load and higher oxygen supply efficiency than the activated sludge process, the engineering cost and operating cost per ton of water treatment are about 20% lower than that of the activated sludge process. Using biofilm process to treat sewage also has the advantages of small floor space, high effluent quality, strong impact load resistance and little influence of odor and noise on the surrounding environment.

Adsorption biodegradation

AB (adsorption biodegradation) process is the abbreviation of adsorption-biodegradation process. Typical AB process flow: sewage-grid-grit chamber -A-level aeration tank-intermediate sedimentation tank (sludge returns to A-level aeration tank) -B-level aeration tank-secondary sedimentation tank (sludge returns to B-level aeration tank)-effluent. Class A (high load) and Class B (low load) are strictly separated and run in series, which can be regarded as an improved two-stage biological treatment technology.

The capital investment of AB method is equivalent to that of traditional activated sludge method, but the operating cost is about 20% lower. AB process can effectively remove nitrogen and phosphorus by using deformed AB process, but its operation and management are complicated. Moreover, AB method is not suitable for the treatment of urban sewage with a high proportion of industrial wastewater.