At present, most of the domestic sewage in rural areas is discharged at will, directly into the river, or discharged into the open space, and then infiltrated into the ground. A small part of the septic tank is simply treated and then infiltrated into the ground, seriously polluting the river water, directly threatening the survival of the masses of peasants. Environment and physical health. Therefore, strengthening the treatment of rural domestic sewage plays an important role in improving the rural ecological environment and improving the living standards of farmers. Based on this, this paper briefly introduces the general situation of a rural sewage and the integrated sewage treatment equipment, and discusses the application of the biological contact oxidation process in the rural buried integrated sewage treatment equipment.
I. Overview of a rural sewage
Taking a rural area as an example, the domestic sewage treatment project in the environmental contiguous remediation project is analyzed. The source of sewage is mainly the diet, washing and excretion in the daily life of the peasants, the random discharge of domestic garbage, the discharge of livestock manure from the family, and the rain. Scouring and so on. Combined with the actual data related to the project, two sets of 20 tons/day buried integrated sewage treatment equipment were designed, and the A/O biological contact oxidation process was adopted in the treatment process. The whole process control system was controlled by PLC, which has high automation. The operation and management are simple, and the discharged water after treatment is required to be discharged or reused.
Second, the analysis of integrated sewage treatment equipment
1, the grille. The grille is mainly used to intercept large floating objects in the sewage to ensure the normal operation of the subsequent treatment structures and effectively reduce the processing load, and to provide guarantee for the long-term normal operation of the system. Due to the small amount of daily grid slag intercepted by the grid, it is about 0.012m3/d per day, and the method of manual cleaning is considered from the aspect of economic operation.
2. Adjust the sedimentation tank. Since the water quality and water source are different, the general peak flow is 2-8 times of the average treatment volume. Therefore, in order to make the sewage treatment system run continuously and stably, and at the same time adjust the water volume and homogenize the water quality, a regulating tank is designed. The effective volume of the adjustment tank is generally 6 to 10 times the average treatment volume.
3. The underground domestic sewage is treated by underground integrated sewage treatment equipment. The main treatment method is the relatively mature biochemical treatment technology contact oxidation method, which consists of the following parts:
(1) Class A biochemical pool. The sewage is further mixed, and the elastic filler in the pool is fully utilized as a bacterial carrier, and the anaerobic microorganisms are used to convert the insoluble organic matter in the sewage into a soluble organic matter, and the macromolecular organic matter is hydrolyzed into a small molecular organic substance to facilitate the downstream O-stage biological treatment pool. Further oxidative decomposition, at the same time through the reflux of carbon monoxide nitrogen under the action of nitrifying bacteria, partial nitrification and denitrification can be carried out to remove ammonia nitrogen.
(2) O-class biochemical pool. The pool is the core part of the sewage treatment. It is divided into two sections. In the previous section, under the high organic load, the biochemical degradation and adsorption are carried out by a large number of microbial communities of different species attached to the filler to remove the sewage. The various organic substances make the content of organic matter in the sewage greatly reduced. In the latter stage, under the condition of low organic load, the ammonia nitrogen in the sewage is degraded by the action of nitrifying bacteria under the condition of sufficient oxygen, and the COD value in the sewage is also reduced to a lower level, so that the sewage can be purified. The pool is composed of a pool body, a packing material, a water distribution device and an oxygenation and aeration system. The biofilm method is mainly composed of the activated sludge method. Therefore, the pool maintains a high biomass and achieves the purpose of removing organic pollutants at high speed. The aeration equipment uses a blower and a microporous aerator, and the utilization rate of oxygen is more than 25%, which effectively saves operating costs. The residence time is ≥7 hours, and the gas-water ratio is around 15:1.
(3) Sedimentation tank. After the sewage is treated by the O-class biochemical tank, the water contains a large amount of suspended solids (biofilm shedding). In order to make the effluent SS reach the discharge standard, the sedimentation tank is used for solid-liquid separation. The sedimentation tank is set up with a surface load of 1.0 m3/m2·hr. The sludge in the sedimentation tank is taken to the sludge tank by gas extraction equipment. At the same time, the sludge is partially taken to the A-grade biochemical pool for sludge return according to the actual water quality, and the sludge concentration in the O-class biochemical pool is increased to improve the removal efficiency.
(4) Disinfection tank. A disinfection device and a deflector are provided inside. The effluent from the second settling tank flows into the disinfection tank for disinfection, so that the effluent water quality meets the requirements of sanitary indicators. At the same time, the disinfection tank also acts as a clearing pool. The disinfection tank contact time is 45 minutes. Disinfection is disinfected with chlorine tablets. The dosage is 4-6 mg/L. After the biochemical and precipitated treated water, it is disinfected. (5) Sludge tank. The sedimentation tank sludge and the secondary sedimentation tank sludge are regularly discharged into the sludge tank for sludge concentration and anaerobic digestion, and the sludge supernatant is refluxed and discharged into the anaerobic tank for further treatment, and the excess sludge is periodically sucked and transported. .
Third, the application of biological contact oxidation process in rural buried integrated sewage treatment equipment
1. Analysis of water treatment process.
The sewage water quality of this project is CODCr≤350mg/l, BOD5≤150mg/l, combined with the characteristics of this project, using biofilm treatment process, it is proposed to use A/O biological contact oxidation process as the main biochemical treatment method.
Due to the high content of ammonia nitrogen and organic matter in the sewage, especially organic nitrogen, organic nitrogen will be expressed in the form of ammonia nitrogen when biodegrading organic matter. Ammonia nitrogen is also an important pollution control indicator. Therefore, the treatment of wastewater uses hypoxia and aerobic A/O biological contact oxidation process, that is, biochemical pool needs to be divided into two parts: A-class pool and O-class pool. The domestic sewage enters the regulating tank through the grille, and the purpose of setting the regulating tank is mainly to adjust the water quantity and water quality of the sewage. The sewage in the regulating tank is lifted to the A-class biochemical pool by the sewage lifting pump for biochemical treatment. Therefore, the A-class pool not only has a certain organic matter removal function, but also reduces the organic load of the subsequent O-stage biochemical pool to facilitate nitrification, and relies on high-concentration organic matter in the sewage to complete denitrification and finally eliminate nitrogen eutrophication pollution. . After the biochemical action of the A-class pool, there is still a certain amount of organic matter and high nitrogen ammonia in the sewage. In order to further oxidize and decompose the organic matter, and at the same time the carbonization tends to be complete, the nitrification can proceed smoothly. Level biochemical pool.
The A-stage pool effluent flows into the O-stage pool. The treatment of the O-stage biochemical pool is completed by autotrophic bacteria. They use the inorganic carbon source generated by the decomposition of organic matter or carbon dioxide in the air as a nutrient source to convert the ammonia nitrogen in the sewage into NO2-. N, NO3-N. Part of the O-stage effluent water enters the sedimentation tank for precipitation, and the other part is returned to the A-stage tank for internal circulation to achieve denitrification. Fillers are installed in both the Class A and Class O biochemical cells, and the entire biochemical process relies on a variety of microorganisms attached to the filler. In the A-class pool, the dissolved oxygen is controlled at about 0.5 mg/l; in the O-class biochemical pool, the dissolved oxygen is controlled at 2.0 mg/l or higher, and the gas-water ratio is 12:1; a portion of the O-level biochemical pool is returned to the A-stage pool, and the reflux ratio is It is 100%-200%; a part flows into the sedimentation tank for solid-liquid separation; the effluent after solid-liquid separation in the sedimentation tank enters the disinfection outlet. The sludge settled in the sedimentation tank is lifted by the gas extraction device to the sludge concentration tank; the sludge concentrated in the sludge concentration tank is treated with agricultural fertilizer outside the waste vehicle.
2. Sewage treatment process.
The septic tank sewage intercepts large floating objects through the grille and enters the regulating sedimentation tank to equalize the water quality. The sewage from the upper sediment enters the A-class biochemical pool, and the bottom sludge is discharged into the sludge tank, and the effluent after treatment by the A-grade biochemical pool Enter the O-class biochemical pool for further biochemical treatment. At this time, the effluent contains a large amount of suspended solids. In order to make the effluent SS reach the discharge standard, the latter stage enters the sedimentation tank for solid-liquid separation, and the bottom sludge is discharged into the sludge tank to make sludge. Disposal, depending on the specific conditions, the supernatant can be returned to the A-class biochemical pool to increase the sludge concentration in the O-class biochemical pool. Finally, it flows into the disinfection tank for disinfection and discharges to the standard.
Fourth, the choice of buried integrated sewage equipment: FRP material
The main equipment adopts polymer composite structure, which has the advantages of high compressive strength, acid and alkali corrosion resistance and long service life (reasonable use for more than 50 years).
It has strong adaptability to water quality, good impact load resistance and stable effluent quality.
Flexible voltage selection: single-phase power (220V) / three-phase (380V) can avoid the inconvenience caused by the use of traditional three-phase electricity mode in some sewage projects, simple and easy.
The whole process of the main equipment is integrated in the workshop, which is not affected by the weather, which greatly shortens the on-site civil construction period;
The operation is safe and reliable, the system operation is simple, the management is convenient, and the maintenance is easy.
The equipment is automatically controlled by liquid level to avoid waste of electricity;
Low construction and operating costs and savings in infrastructure investment.
Conclusion
In summary, FRP buried integrated sewage treatment equipment, garden design concept; process route: mature, stable, practical, economic; main core equipment to achieve workshop standardization; operating system: intelligent, automated. It will be widely used in small rural sewage treatment systems.
references:
Jiang Jinfeng et al. Process Analysis of Integrated Treatment Equipment for Rural Domestic Sewage[J].Hubei Agricultural Sciences,2012(12)
Yu Jianpeng et al. Application research of integrated rural domestic sewage treatment technology[J].Environmental Engineering,2013(08)
Mei Liyong et al. Study on Operational Performance of Rural Integrated Wastewater Treatment Equipment[J].Anhui Chemical,2016(12)
Original title: Application of integrated sewage equipment (glass fiber reinforced plastics) in rural sewage
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