Sewage treatment information?

Introduction of domestic sewage treatment I. Overview

Domestic sewage treatment process is now quite mature, the core technology for the activated sludge method and biofilm method, the activated sludge method (or biofilm method) of the improvement and development of the formation of a variety of different domestic wastewater treatment process, the traditional activated sludge treatment process in small and medium-sized domestic wastewater treatment has been less used. According to the amount of sewage, water quality and effluent requirements and local conditions, the selection of a reasonable sewage treatment process, the normal operation of sewage treatment, treatment costs have a decisive role.

This article is a brief introduction to the main domestic sewage treatment process commonly used.

Two, small and medium-sized domestic sewage treatment process

Typical domestic sewage treatment process is complete as follows: sewage - pre-treatment - biochemical method - secondary sedimentation tank -

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------ sludge treatment system -

Disinfection -

Outlet - Effluent

Pre-treatment, also known as pre-treatment techniques, are commonly used, such as grids or grids, regulating tanks, sand sedimentation tanks, primary sedimentation tanks and so on.

Because the core of domestic wastewater treatment is the biochemical part, so we say that wastewater treatment process is specifically referred to this part, such as contact oxidation, SBR method, A/O method, etc.. Biochemical method (including anaerobic and aerobic) treatment of domestic sewage at present is the most economical, the most applicable sewage treatment process, according to the amount of domestic sewage, water quality and site conditions and choose a different sewage treatment process has a decisive impact on the investment and operating costs. The following is a brief introduction to the current common domestic sewage treatment process.

1, no energy consumption buried small domestic sewage device

that is, the improved septic tank, the process is as follows:

Sewage - anaerobic hydrolysis tank - anaerobic filtration tank - anaerobic ditch - effluent

Water - anaerobic hydrolysis tank - anaerobic filtration tank - Oxidation ditch - water

Anaerobic hydrolysis tank that is the national standard septic tank, anaerobic filtration tank that is an anaerobic contact oxidation tank, built-in filler, oxidation ditch that is the use of drainage ditches and forced ventilation, the process of oxygen in the air dissolved in sewage for the natural process. This sewage treatment process is suitable for single residential building of domestic sewage treatment, and can be used in combination with the national standard septic tank, its biggest advantage is that the operating costs are zero. The effluent water quality can reach the national "comprehensive sewage discharge standards" in the secondary standards.

The process is suitable for sewage volume less than 20m3/d sewage treatment works, can be used in more affluent rural areas.

2, A/O method

that is, anaerobic - aerobic sewage treatment process, the process is as follows:

Sewage - pre-treatment - anaerobic hydrolysis pool --Contact oxidation tank --Sedimentation tank

|_______ sludge return___|

--Filtration tank -- Effluent A: The anaerobic hydrolysis tank adopts the form of upflow anaerobic sludge bed reactor, and the design hydraulic retention time is 2~4 hours.

The lower part of the anaerobic pool is the sludge bed area, the thickness of the sludge bed is usually controlled between 1~1.2M, the water inlet system can be used in the pulse inlet water resistance water distribution system, the bottom of the cloth ditch is set up to retain the sludge does not deposit the bottom of the sludge in a suspended state.

The average concentration of sludge bed is 30~35g/l, then the sludge load is 0.35~0.30kgCODcr/kg(ss).d.

B: Biological contact oxidation process is between the activated sludge method and the biofilm method of a sewage treatment process. The tank is equipped with filler, part of the microorganisms in the form of biofilm fixed on the surface of the filler, part of the flocculent suspended growth in the water, so it has both the activated sludge method and the characteristics of the biofilter. The aeration system can be used as blast or jet aeration and oxygenation system (investment and operation cost must be considered when designing). In order to cultivate different dominant strains of microorganisms, it is effective to divide the contact oxidation tank into two compartments. The effective hydraulic retention time of the first compartment is 2.5 hours, and the organic load is 1.15kgBOD5/m3.d. The effective hydraulic retention time of the second compartment is 1.5 hours, and the organic load is 0.768kgBOD5/m3.d.

The main features of the A/O method are as follows: strong adaptive capacity; shock load resistance; high volumetric loading; absence of sludge expansion; and very low sludge discharge; It has better nitrogen removal effect.

A2/O and A3/O wastewater treatment processes derived from the A/O method are similar in principle.

3, SBR method

that is, intermittent activated sludge method, because it has a series of characteristics better than the ordinary activated sludge method, has been commonly used in sewage treatment works.SBR method of aeration pool both precipitation, anaerobic, aerobic also in the same pool. Its operation consists of five processes: inflow, reaction, sedimentation, discharge and standby. By adjusting the time of each process, the effect of phosphorus and nitrogen removal can be achieved.

Pre-treatment - SBR reactor - Filtration - Effluent

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Sludge disposal

Design points: Theoretically the volume load of SBR reactor has a more in the range of 0.1~1.3 kgBOD5/m3.d, but for safety, generally take a low value, such as 0.1 kgBOD5/m3.d about. The highest water level and the lowest water level, the highest water level that is the water level at the reaction, the lowest water level is the water level at the end of the discharge process, the lowest water level must ensure that in the drainage at this level, the sedimentation sludge is not lost with the supernatant.

The main features of the SBR process are: better effluent water quality; occupies less land; does not produce sludge expansion; phosphorus removal and denitrogenation effect is good.

4, oxidation ditch

Oxidation ditch is a kind of activated sludge method of deformation, its tank is long and narrow, so it is called oxidation ditch. Oxidation ditch has a variety of construction type, typical: A: Carrose type; B: O'Barr type; C: alternate working oxidation ditch; D: aeration - sedimentation integrated oxidation ditch

Oxidation ditch technology has been widely used in large and medium-sized urban wastewater treatment plants, the scale from several hundred cubic meters per day to several tens of thousands of cubic meters, the process is becoming more and more sophisticated, and the construction type is more and more. Its main features are: inlet and outlet devices. Its main features are: simple inlet and outlet devices; the flow of sewage can be regarded as completely mixed, due to the long and narrow pool, and similar to the push-flow type; low BOD load, good quality of treated water; low sludge yield, less sludge discharge; long sludge age, with the function of nitrogen removal.

Design points: suspended solids concentration of 5000mg/l; average retention time of biosolids, removal of BOD5, take 5-8 days, when the nitrification reaction is required to take 10-30 days; hydraulic retention time of 20, 24, 36, 48h, according to the requirements of the treated water quality; BOD-SS loading (Ns) of 0.03~0.07kgBOD/(kgMLSS.d); BOD volumetric loading (Nv) is 0.1~0.2 kgBOD/(m3.d); sludge reflux ratio is 50~150%; the flow rate of the mixed liquid in the ditch is 0.4~0.5m/s; the flow rate at the bottom of the ditch is 0.3 m/s.

Three, the development of domestic wastewater treatment processes

With the continuous improvement of people's living standards, the development of domestic wastewater treatment processes is becoming increasingly important. p> With the continuous improvement of people's living standards, people's quality requirements for the living environment also continue to improve. Forced by the pressure of the environment, have proposed the construction of domestic sewage treatment plant, in the efforts of environmental workers, the new sewage treatment process continues to emerge. Such as: the SBR and oxidation ditch advantages of the combination of reciprocating activated sludge method; CASS sewage treatment process; HCR high-efficiency biological water treatment technology; membrane biological method and so on. The emergence of new sewage treatment processes, around a small footprint, low operating costs, low total investment, automation and other factors, around the actual situation and the choice of sewage treatment process suitable for the region.