CN107216004B - Domestic sewage treatment system and method - Google Patents

Abstract

The invention discloses a domestic sewage treatment system, comprising an anaerobic regulation tank, an anoxic reaction tank, a biological filter tower unit, and a subsurface constructed wetland; The oxygen reaction pools are connected by an artesian channel, the anoxic reaction pool is equipped with a lift pump, the biological filter tower unit is located above the anaerobic adjustment tank and the anoxic reaction pool, and is equipped with a high water level tank. The water collecting pipe and the water outlet of the perforated water collecting pipe are connected with the subsurface artificial wetland, and the biological filter material is arranged in the biological filter tower unit and the subsurface artificial wetland. Further, a sewage treatment method based on the system is also disclosed. The system and method have the advantages of small footprint, small one-time investment, low operating cost, strong shock load resistance, high water treatment efficiency, stable effluent quality, and good landscape effect.

Description

Domestic sewage treatment system and method

technical field

The invention belongs to the technical field of sewage treatment, and in particular relates to a domestic sewage treatment system and method.

Background technique

my country is a country with a large population and a large agricultural sector, and most of the population of our country is distributed in rural areas. In recent years, with the rapid economic development of various townships and the improvement of people's living standards, domestic water consumption has gradually increased, and the resulting domestic sewage discharge has continued to increase, making surface water bodies unable to bear excessive load, and environmental safety hazards and problems. increasingly serious. Excessive domestic sewage discharge exceeds the self-purification capacity of the water body, causing water pollution, which not only affects the quality of life of residents, but also affects the health of residents.

In 2009, the Ministry of Housing and Urban-Rural Development pointed out in the report "Village and Town Planning and Construction in the Era of Ecological Civilization" that according to the statistics of the Ministry of Housing and Urban-Rural Development, the sewage treatment rate at the township government's residence was only 1.7% at the end of 2006. It can be inferred that the treatment rate of domestic sewage in rural areas is lower, and rural sewage is basically discharged into rivers and lakes on the spot. Since sewage contains a large amount of organic matter, nitrogen and phosphorus elements, the environmental capacity and ecological carrying capacity of rivers and lakes are overwhelmed. Ecosystems have been severely damaged, and water pollution has become more and more serious, resulting in large-scale cyanobacteria and algal blooms, resulting in deterioration of water quality, seriously affecting the ecological environment in rural areas, and posing a hazard to people's quality of life and health.

In addition, the characteristics of rural sewage quality: rural domestic sewage mainly comes from two sources, including: 1) water for kitchen utensils and cooking, showering, washing water and toilet flushing water, mainly containing organic matter, nitrogen and phosphorus, as well as bacteria, viruses, parasites, etc. Generally, it does not contain toxic substances; 2) The manure and wastewater produced by the farming of rural residents and livestock and poultry mainly contain nitrogen, phosphorus, BOD, COD, suspended solids and other pollutants. The water quality of these sewage has the characteristics of good biochemical properties. Characteristics of rural sewage discharge: Most rural areas do not have special sewage and wastewater pipeline network collection and treatment facilities, and rural domestic sewage is generally discharged to roads, rivers, and pits near residential sites along the terrain. The main features are: 1) Small flow, The coefficient of variation is large; 2) The rural residents are scattered and have a regular life, resulting in larger sewage discharge in the morning and evening than in the daytime, and less discharge at night; 3) There is a peak period in the morning, afternoon and evening, and the appearance of the peak period is related to the season, local rural living habits and other factors.

Based on this, the treatment process studied is mainly aimed at the pollution factors of domestic sewage, and removes suspended solids, organic matter, nitrogen, phosphorus and other indicators in the water.

SUMMARY OF THE INVENTION

The purpose of the present invention is to study a domestic sewage treatment system and method, which can integrate sewage collection, filtration, biochemical and ecological purification treatment processes, and treat dispersed sewage to remove suspended solids, organic matter, nitrogen, phosphorus and other pollution. Factors, and the quality of the effluent after treatment reaches the Class A standard of "Pollutant Discharge Standards for Urban Sewage Treatment Plants" (GB18918-2002). The specific technical solutions are as follows:

A domestic sewage treatment system, comprising an anaerobic adjustment tank 1, an anoxic reaction tank 2, a biological filter tower unit 3, and a subsurface constructed wetland 4; The tank 1 and the anoxic reaction tank 2 are connected by an artesian channel. A lift pump 6 is arranged in the anoxic reaction tank 2. The biological filter tower unit 3 is located above the anaerobic adjustment tank 1 and the anoxic reaction tank 2. The water level tank 7, the water inlet of the high water level tank 7 is connected with the lift pump 6 through the water delivery pipeline 19, the water outlet of the high water level tank 7 is connected with the top of the biological filter tower unit 3, and the bottom of the biological filter tower unit 3 is arranged with perforated collectors. The water pipe 8 and the water outlet of the perforated water collecting pipe 8 are connected to the subsurface constructed wetland 4 , and the biological filter tower unit 3 and the subsurface constructed wetland 4 are both provided with biological filter materials.

Further, the biological filter material in the biological filter tower unit 3 and/or the subsurface constructed wetland 4 can also be covered with a vegetation layer, so that the system can comprehensively use physical, chemical and biological actions under the combined action of plants and soil microorganisms. deal with.

Further, the biological filter tower unit 3 includes a multi-stage biological filter tank 20, and the diameter of the biological filter tank 20 increases step by step from top to bottom. And fall into the filter tank at all levels. In this way, the whole process of self-flow biochemical filtration can be realized, which can effectively screen and absorb suspended solids in sewage and contact oxidation. While removing organic matter, nitrifying bacteria aerobic nitrification converts Kjeldahl nitrogen in future water into nitrate nitrogen and nitrite nitrogen.

Further, a water collector 13 is arranged at the bottom of the biological filters 20 at all levels, and a ring of water outlet troughs 14 is provided outside. The top enters the next stage biofilter 20 in the form of a drop.

Further, the biological filters 20 at all levels have a cylindrical structure, the water collectors 13 arranged at the bottom of the biological filters 20 at all levels are circular, and the water outlet grooves 14 arranged outside are annular.

Further, the high water level tank 7 is arranged at the center of the biological filter tower unit 3 and runs through the biological filter tower unit 3 longitudinally, and its water outlet end is located at the top of the biological filter tower unit 3 .

Further, the water outlet end of the high water level tank 7 is connected with a trumpet-shaped weir 10 with an upward opening.

Further, the high water level tank 7 has a cylindrical structure, and the cross-section of the trumpet-shaped weir 10 at the water outlet end is circular to realize a circumferentially uniform distribution of water, so as to ensure uniform distribution of the inlet water of the biological filter tower unit 3 .

Further, the anaerobic conditioning tank 1 and the anoxic reaction tank 2 are arranged together in a water tank and are divided into two mutually independent tank bodies by means of a partition.

Further, the volume of the anaerobic conditioning tank 1 is 1.5-2.5 times the volume of the anoxic reaction tank 2 .

Further, the anaerobic regulation tank 1 and the anoxic reaction tank 2 are arranged together in a water tank, and the biological filter tower unit 3 is fixed directly above the water tank and forms an integrated structure with the water tank.

Further, the water outlet end of the perforated water collecting pipe 8 is arranged with a first water outlet branch pipe 11 connected to the anaerobic conditioning tank 1 and/or anoxic reaction tank 2 and a second water outlet branch pipe 15 connected to the subsurface constructed wetland 4 . The first water outlet branch pipe 11 realizes the backflow of part of the effluent, and the backflow ratio can be controlled between 50-200%, thereby further improving the efficiency of denitrification and denitrification of the system.

Further, the second water outlet branch pipe 15 is provided with a second water quantity control valve 16 for controlling the water inflow from the biological filter tower unit 3 to the subsurface constructed wetland 4 .

Further, the first water outlet branch pipe 11 is arranged with a first water quantity control valve 12, which is used to control the water inflow from the biological filter tower unit 3 back to the anaerobic adjustment tank 1 and/or the anoxic reaction tank 2.

Further, an outlet channel 17 is provided at the end of the subsurface constructed wetland 4 , and the outlet channel 17 is equipped with a water outlet control valve 18 .

Further, a bactericide injection interface is arranged at the outlet channel 17 of the subsurface constructed wetland 4 , which can be used to inject the bactericide into the outlet channel 17 .

Further, the lift pump 6 is powered by a solar cell assembly.

The present invention also discloses a domestic sewage treatment method, which adopts any one of the domestic sewage treatment systems with the above characteristics for sewage treatment. It flows into the anoxic reaction tank 2 through the self-flow channel, and the water treated in the anoxic reaction tank 2 is pumped into the high water level tank 7 through the lift pump 6. Up-down flow path biological filter tower unit 3; the water treated by the biological filter tower unit 3 is discharged through the perforated water collection pipe 8, thereby completing the sewage treatment process.

The basic treatment process of the system and method is: waste water collection - anaerobic digestion and regulation - anoxic - lift pump - high level water tank - biological filter - effluent (partial return to anoxic tank and/or anaerobic tank) - subsurface wetland -emission. It can be seen that the system and method can complete all the functions of organic matter removal, nitrogen and phosphorus removal, high-efficiency filtration, and ecological water purification from sewage only by consuming one time to increase energy consumption. , The characteristics of high dispersion type and large water quality fluctuation.

The domestic sewage treatment system and method disclosed in the present invention have the following beneficial effects:

(1) Combining two processes of biochemistry and ecology, the biochemical system includes anaerobic tank, anoxic tank and drop-type biological filter tower, and the ecological system includes subsurface constructed wetland. The multi-stage biological filter can not only effectively screen and absorb suspended solids in sewage, but also remove organic substances through biological contact oxidation. The reflux of the effluent from the filter tower can further improve the denitrification and phosphorus removal efficiency of the system. Subsurface constructed wetlands can further remove pollutants such as suspended solids, organic matter, nitrogen, and phosphorus through ecological self-purification. The whole system has the advantages of strong shock load resistance, high water treatment efficiency, and stable effluent quality. It is especially suitable for the treatment of rural scattered domestic sewage with small water volume, wide dispersion and large water quality fluctuation.

(2) The water quality of the effluent treated by the system and method can meet the requirements of Class A of the National Pollutant Discharge Standard for Urban Sewage Treatment Plants (GB18918-2002), while the effluent quality of this type of treatment device in the prior art can only be Meet level B requirements.

(3) There is only one electrical equipment for the sewage lifting pump in the whole equipment composition of the system, and the rest of the sewage can flow through gravity. Among them, the lifting pump can be powered by mains power, its installed capacity is 0.1kw, and the total water treatment cost per ton is 0.2kwh/ ^m3 water, and the solar cell module power supply device can also be used to supply power to the lifting pump, so as to achieve "zero energy" It has the advantages of energy saving, environmental protection and low operating cost.

(4) The design of the drop-type biological filter can increase the dissolved oxygen content in the filter without the need for aeration device, and save the energy consumption required for aeration.

(5) The system can arrange the anaerobic tank and the anoxic tank in a water tank, and the water tank and the biological filter tower unit are connected up and down to form an integrated treatment device, so that the overall structure is compact and the floor area is small; the integrated treatment device It can also be combined with artificial wetlands, the structure design is reasonable, and it has the advantages of high functional integration, low one-time investment cost and good landscape effect.

Description of drawings

Fig. 1 is the structural schematic diagram of the domestic sewage treatment system in the embodiment

Figure 2 is a schematic cross-sectional view of the water tank in the embodiment

Fig. 3 is the cross-sectional schematic diagram of the drop-type biological filter tower in the embodiment

Figure 4 shows the mechanism of biological denitrification

Figure 5 shows the mechanism of biological phosphorus removal

Note in the drawings: anaerobic adjustment tank 1, anoxic reaction tank 2, biological filter tower unit 3, submerged constructed wetland 4, water inlet pipeline 5, lift pump 6, high water level tank 7, perforated water collection pipe 8, water delivery control valve 9. Circular weir mouth 10, water outlet branch pipe 11, water volume control valve 12, circular water collector 13, annular water outlet groove 14, water outlet branch pipe 15, water volume control valve 16, water outlet channel 17, equipped with water outlet control valve 18, water pipeline 19. Biological filter 20.

Detailed ways

The embodiment discloses a domestic sewage treatment system (referred to as the system) for rural decentralized domestic sewage treatment. The system intends to use the method of increasing energy consumption once and self-flowing throughout the whole process to collect and process the domestic sewage that is discharged disorderly, so as to realize The environmental goal of pollution control, and realize the miniaturization, equipment, unmanned, low-cost operation of the treatment device, and can take into account the beautifying effect of the appearance.

The system is further described below in conjunction with the accompanying drawings and specific embodiments:

Referring to Figures 1, 2 and 3, the system includes an integrated device for domestic sewage treatment (referred to as an integrated device) and a subsurface constructed wetland 4. The integrated device for domestic sewage treatment mainly includes an anaerobic conditioning tank 1, an anoxic reaction Pool 2 and Biofilter Unit 3.

The anaerobic regulation tank 1 and the anoxic reaction tank 2 are arranged together in a buried carbon steel cylindrical water tank, and the biological filter tower unit 3 is fixed directly above the cylindrical water tank to form an integrated vertical tower-like structure. The cylindrical water tank has two compartments, namely anaerobic regulation pool 1 and anoxic reaction pool 2, and the anaerobic regulation pool 1 and anoxic reaction pool 2 are connected by an artesian channel. As shown in Figures 2(a) and (b), the anaerobic conditioning tank 1 and the anoxic reaction tank 2 can be divided into two concentric sectors or circular cylinders by means of partitions. The self-flow channel can be designed as a structure such as a communicating pipe or a weir. In the specific design, the volume of the anaerobic adjustment tank 1 can be 1.5-2.5 times the volume of the anoxic reaction tank 2, and the actual size can be adjusted according to the processing capacity. A water inlet pipe 5 is arranged at the water inlet end of the anaerobic conditioning tank 1 . A lift pump 6 is arranged at the center of the bottom of the anoxic reaction tank 2 .

The biological filter tower unit 3 is composed of a multi-stage circular biological filter tank 20. The diameter of the biological filter tank increases step by step from top to bottom. It enters the filter tanks at all levels in a top-down manner. A circular water collector 13 is arranged at the bottom of the biological filters at all levels, and an annular water outlet 14 is arranged on the outside. Refer to the two cross-sectional views shown in Figure 3 (a) and (b). The filter 13 enters the water outlet tank 14, and then enters the next-stage biological filter tank 20 in the form of falling from the top of the water outlet tank 14.

The central position of the biological filter tower unit 3 is arranged with a cylindrical high water level tank 7. The high water level tank 7 runs through the biological filter tower unit 3 longitudinally. The top of the biological filter tower unit 3 serves as the water inlet of the biological filter tower unit 3 . The water delivery pipeline 19 is provided with a water delivery control valve 9 for controlling the amount of water pumped into the high-level water tank 7 . The longitudinally penetrating structure of the high water level tank 5 can be used for the support and fixation of the biological filters 20 at all levels in the multi-stage biological filter unit 7 on the one hand, and is also conducive to stabilizing the influent water pumped from the lift pump 6 on the other hand. . The water outlet end of the high water level tank 7 is connected with a trumpet-shaped weir with an upward opening and a circular cross-section, and the uniform distribution of water in the biological filter tower unit 3 is ensured by the uniform distribution of water around the circumference.

The bottom of the biological filter tower unit 3 is arranged with a perforated water collection pipe 8, and the water outlet end of the perforated water collection pipe 8 is divided into two water outlet branch pipes. 15 is connected to the subsurface artificial wetland 4. And a water volume control valve 12 is provided on the water branch pipe 11, which is used to control the water inflow from the biological filter tower unit 3 back to the anaerobic adjustment tank 1 and/or the anoxic reaction tank 2; the water outlet branch pipe 15 is provided with a water volume control valve. 16. It is used to control the water inflow from the biological filter tower unit 3 to the underflow constructed wetland 4.

An outlet channel 17 is provided at the end of the subsurface constructed wetland 4, and the outlet channel 17 is equipped with a water outlet control valve 18 to control the water level in the wetland. A bactericide injection interface is arranged at the outlet channel 17 of the subsurface constructed wetland 4 for adding the bactericide to the outlet channel 17 for backup.

Biological filter material is arranged in both the biological filter tower unit 3 and the subsurface constructed wetland 4 and covered with a vegetation layer. In this way, the system can comprehensively use physical, chemical and biological actions to treat sewage under the combined action of plants and soil microorganisms.

Based on this system, the waste water enters the anaerobic regulation tank 1 through the water inlet pipe 5, and flows into the anoxic reaction tank 2 by itself; in this process, the anaerobic regulation tank 1 is adjusted to play the role of regulation and anaerobic biochemistry to stabilize the water quality. , through the anoxic reaction tank 2 to play an anoxic biochemical role, mix the aerobic backflow water, and achieve the purpose of denitrification and denitrification.

The treated effluent from the anoxic reaction tank 2 is pumped into the high-level water tank 7 through the lift pump 6 , and after a steady flow in the high-level water tank 7 , flows into the biological filter tower unit 3 through the weir mouth 10 . The drop-type biological filter tower 3 receives the self-flowing water from the weir mouth 10, and in the biological filter tower unit 3, it enters the biological filter tanks of all levels from top to bottom through the action of gravity, so as to realize the whole-process self-flow filtration. Biological filter materials of a certain height are installed inside the biological filters 20 of all levels. The biological filter materials have a relatively high surface area as the carrier of microorganisms, and also have a high porosity to ensure the uniform flow of wastewater. The biological filter 20 Natural oxygen enrichment through hydraulic distribution to meet the requirements of dissolved oxygen in the aerobic filter; aerobic biochemical action on incoming water and its filtering and interception function to remove suspended solids, biochemical degradation of organic matter, and aerobic nitrification at the same time, Remove ammonia nitrogen pollutants in incoming water.

The effluent water of the biological filter tower unit 3 is discharged through the perforated water collection pipe 8, and part of the discharged water enters the subsequent subsurface constructed wetland 4 through the water outlet branch pipe 15, and the other part enters the anaerobic tank and/or anoxic tank through the water outlet branch pipe 11.

The subsurface constructed wetland 4 receives part of the effluent of the biological filter tower unit 3, and under the combined action of plants and soil microorganisms, comprehensive physical, chemical and biological actions are used to treat the sewage. Physical effects include precipitation and filtration and adsorption of pollutants by plant roots. Chemical action mainly refers to various chemical reaction processes in the constructed wetland system due to the diversity of plants, microorganisms, fillers and enzymes. Biological effects are mainly microbial metabolism, bacterial nitrification and denitrification, and plant metabolism and absorption to remove pollutants. Further, the bactericide can be added to the outlet channel 17 of the subsurface constructed wetland as required to meet the requirements of the fecal Escherichia coli index. The effluent of the submerged wetland is controlled by the water outlet control valve 18 to control the water level and the degree of treatment, and reserve a bactericide interface. If sterilization is required, add bactericide to the outlet channel through the bactericide interface.

Further, the domestic sewage treatment system can also be operated unattended and fully automatic. There is only one electrical equipment among all the equipments of the system, namely the sewage lifting pump 6 . The power supply of the lift pump 6 may adopt the mains power supply mode or the solar panel power supply mode. If the mains power supply is used, the installed capacity is 0.1kw, and the total water treatment cost per ton is 0.2kwh/ ^m3 water; if the solar panel power supply device is used to supply power to the lifting pump, “zero energy consumption” can also be achieved. Purpose.

It should be noted that, in the specific embodiment of this patent, the domestic sewage treatment system, the domestic sewage treatment system and the system, the anaerobic conditioning tank and the anaerobic tank, the anoxic reaction tank and the anoxic tank, the subsurface constructed wetland and the constructed wetland Etc. with similar expressions all express the same meaning.

Of course, in addition to the integrated structure shown in the embodiment, other structural designs can also be made according to requirements. For example, the anaerobic adjustment tank 1 and the anoxic reaction tank 2 are not designed in one box, even if they are designed in one box. It is not necessarily located directly below the biological filter tower unit 3 and forms an integrated structure; for example, the cross-section of the box body, the high water level tank 7, and the biological filter tank 20 is not limited to a circle, and can be designed into other shapes such as a rectangle.

It can be seen from the above examples that the system is mainly composed of two organic parts. The first part uses an A/A/O process with denitrification function (anaerobic anoxic and aerobic process), and the second part uses artificial subsurface wetlands. The anaerobic-anoxic-aerobic-underflow wetland on the fluid state meets the requirements of removing organic matter, N, and P. Among them, the aerobic process of the A/A/O section uses a low-load biological filter, which can also achieve the purpose of being unpowered and unattended, and through the design of the appearance of the equipment, taking into account the beauty of the equipment and the coordination with the environment; Artificial subsurface wetlands can form a good landscape effect through the selection of plants.

Sewage collection, anaerobic digestion, and anoxic biochemistry can share a buried carbon steel water tank. The inside of the tank is divided into two parts: anaerobic digestion adjustment tank and anoxic tank according to process requirements. Dispersed collection and regulation of sewage and anaerobic digestion can share a pool compartment, which not only plays the role of regulating the water collection volume and homogeneous regulation of the pool, but also uses its anaerobic conditions for biochemical digestion to improve biochemical properties and reduce the content of organic matter in the influent; The effluent flows into the anoxic tank body, and is mixed with the nitrification liquid returned from the effluent of the subsequent aerobic biochemical filtration process, and anoxic denitrification occurs, which removes nitrate nitrogen in the sewage and supplements the alkalinity required for the subsequent aerobic biochemical filtration. The effluent from the anoxic tank is pumped into the high-level water tank for water distribution through the lift pump, and flows into the biological filter tower unit from the water distribution area. The suspended solids in the wastewater are effectively screened and adsorbed, and contact oxidation occurs. While removing organic matter, nitrifying bacteria aerobic nitrification converts Kjeldahl nitrogen into nitrate nitrogen and nitrite nitrogen in the future. Part of the effluent from the biological filter tower unit is returned to the anoxic tank, and part of it enters the subsurface wetland. Suspended solids, nitrogen and phosphorus are further removed through the action of undercurrent, that is, the interception between plant roots and soil.

It can be seen that the system integrates anaerobic, anoxic, aerobic biological filtration, and subsurface wetlands, and realizes the effective removal of organic matter, N, P and suspended solids through the metabolism of microorganisms of different species; By consuming a single increase in energy consumption, all the functions of removal of organic matter, nitrogen and phosphorus removal, and high-efficiency filtration are completed.

The system and its corresponding method include multiple treatment processes such as anaerobic, anoxic, aerobic and subsurface wetlands, involving biological nitrogen removal mechanism, biological phosphorus removal mechanism and subsurface wetland mechanism. The details are as follows:

Biological denitrification mechanism: Referring to Figure 4, biological denitrification is accomplished by organic nitrogen ammonification, nitrification, denitrification and assimilation of microorganisms.

Ammonation refers to the process by which ammonia is released when amino acids and other nitrogen-containing organics are biodegraded. Nitrifying bacteria can convert ammonia nitrogen to nitrate only when organic nitrogen is converted to ammonia and released into the medium. Nitrification is accomplished by autotrophic aerobic microorganisms. Ammonia nitrogen is first converted into nitrite under the action of nitrous bacteria, and then nitrite is further converted into nitrate under the action of nitrifying bacteria. The reaction is represented by the following formula, and a large amount of oxygen is required in the process.

Denitrification is accomplished by heterotrophic facultative microorganisms and can be represented by the following formula:

In the absence of molecular oxygen, denitrifying bacteria use nitrate nitrogen as electron acceptor, and organic matter as carbon source and electron donor, through the assimilation (anabolism) and dissimilation (catabolism) of denitrifying bacteria.

和

被还原为氨用以新细胞的合成，氮成为细胞质的成分。异化作用是

和

被还原为N₂或N₂O、NO等气态物，主要为N₂，异化作用去除的氮约占去除总量的70％～75％。assimilation is

and

It is reduced to ammonia for the synthesis of new cells, and nitrogen becomes a constituent of the cytoplasm. Alienation is

and

It is reduced to N ₂ or N ₂ O, NO and other gaseous substances, mainly N ₂ , and the nitrogen removed by dissimilation accounts for about 70% to 75% of the total removal.

In this system, the above biological denitrification process is mainly realized through the anoxic-aerobic biological filter section.

Biological phosphorus removal mechanism: Referring to Figure 5, biological phosphorus removal is a complex process carried out by the growth of phosphorus accumulating organisms (PAOs). PAOs have the unique ability to deplete intracellular polyphosphate storage carbon sources under anaerobic conditions and deplete carbon sources to store phosphate under aerobic/anoxic conditions.

Comeau and Wentzel et al. respectively proposed a model to explain the function of PAOs, called the Comeau-Wentzel model. After the wastewater is fermented in the sewer, most of the organic matter exists in the form of acetic acid and short-chain fatty acids (SCFA). When the wastewater enters the anaerobic zone of the bioreactor, the facultative heterotrophic microorganisms ferment to produce additional fatty acids. . PAOs break down intracellular stored polyphosphate to provide the energy required for ATP synthesis and store acetic acid as PHB. The hydrolysis of polyphosphate to form ATP increases the intracellular concentration of inorganic phosphate (P _i ) _, which is released into the bulk solution along with cations.

When the wastewater enters the aerobic zone, the dissolved organic matter in the wastewater decreases, but the PAOs contain a large amount of PHB storage. Inorganic phosphates are abundant in wastewater, while PAOs are low in polyphosphates. In order to grow, PAOs use the stored PHB as carbon source and energy source for aerobic metabolism, absorbing all the phosphate released in the anaerobic zone and the initial phosphate contained in the wastewater. PAOs remove phosphorus from wastewater by alternating cycles of anaerobic and aerobic environments. Most phosphorus removal systems use an aerobic zone to generate polyphosphoric acid storage, and some PAOs use nitrate and nitrite as electron acceptors under anoxic conditions to form denitrification phosphorus removal systems.

In this system, the above biological phosphorus removal process is mainly realized through the anaerobic-aerobic biological filter section.

Underflow wetland mechanism: Underflow constructed wetlands (also known as constructed wetland ecosystems) are constructed by placing sewage on swamps where the soil is often saturated with water and where water-resistant plants such as reeds and cattails grow, and the sewage flows in a certain direction. , A land treatment process in which sewage is purified under the combined action of water-resistant plants and soil. The mechanism of constructed wetlands for sewage treatment is very complex. It is generally believed that constructed wetlands combine physical, chemical and biological effects on sewage treatment. Physical effects include precipitation and filtration and adsorption of pollutants by plant roots. Chemical action mainly refers to various chemical reaction processes in the constructed wetland system due to the diversity of plants, microorganisms, fillers and enzymes. Biological effects are mainly microbial metabolism, bacterial nitrification and denitrification, and plant metabolism and absorption to remove pollutants.

The constructed wetland ecosystem has a good effect on sewage treatment, and the quality of the effluent is stable. It can not only remove organic matter, but also remove phosphorus, nitrogen and heavy metals. At the same time, it has the characteristics of convenient operation and management, and low investment and operating costs. It has been reported that the two-stage series constructed wetland system is used to denitrify and dephosphorize the rural domestic sewage in the Taihu Lake area. 90% and 83% to 94%.

From the above, it can be seen that the present invention is integrated on the basis of the existing independent treatment device, combined with the subsurface constructed wetland, and achieves the purpose of biological nitrogen and phosphorus removal through a biological environment with anaerobic-anoxic-aerobic alternation. It is supplemented by subsurface wetlands to strengthen the treatment of organic matter, nitrogen, phosphorus and suspended solids in the wastewater to ensure that the effluent quality meets the standard.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (6)

1. A domestic sewage treatment system is characterized by comprising an anaerobic adjusting tank (1), an anoxic reaction tank (2), a biological filter tower unit (3) and an undercurrent artificial wetland (4), wherein a water inlet pipeline (5) is arranged at the water inlet end of the anaerobic adjusting tank (1), the anaerobic adjusting tank (1) is connected with the anoxic reaction tank (2) through a self-flowing channel, a lift pump (6) is arranged in the anoxic reaction tank (2), the biological filter tower unit (3) is positioned above the anaerobic adjusting tank (1) and the anoxic reaction tank (2) and is provided with a high water level tank (7), the water inlet of the high water level tank (7) is connected with the lift pump (6) through a water pipeline (19), the water outlet is connected with the top of the biological filter tower unit (3), a perforated water collecting pipe (8) is arranged at the bottom of the biological filter tower unit (3), the water outlet of the perforated water collecting pipe (8) is connected with the subsurface flow constructed wetland (4), and biological filter materials are arranged in the biological filter tower unit (3) and the subsurface flow constructed wetland (4) and are covered with a vegetable layer;

the biological filter tower unit (3) comprises a plurality of stages of biological filters (20), the diameters of the biological filters (20) are increased step by step from top to bottom, and the inlet water from the high water level tank (7) falls into each stage of filter tower from the top of the biological filter tower unit (3) through gravity;

the high water level tank (7) is arranged at the central position of the biological filter tower unit (3) and longitudinally penetrates through the biological filter tower unit (3), and the water outlet end of the high water level tank is positioned at the top of the biological filter tower unit (3); the water outlet end of the high water level tank (7) is connected with a horn weir crest (10) with an upward opening, so that water is uniformly distributed on the circumference;

the anaerobic adjusting tank (1) and the anoxic reaction tank (2) are arranged in a buried water tank together, and the biological filter tower unit (3) is fixed right above the water tank and forms an integrated structure with the water tank.

2. The domestic sewage treatment system according to claim 1, wherein a water collector (13) is arranged at the bottom of each stage of the biological filter (20), a ring of water outlet grooves (14) are arranged outside, and sewage in each stage of the biological filter (20) enters the water outlet grooves (14) through the water collector (13) and then enters the next stage of the biological filter (20) from the top of the water outlet grooves (14) in a falling manner.

3. The domestic sewage treatment system according to claim 1, wherein the outlet end of said perforated header pipe (8) is provided with a first outlet branch pipe (11) connected to the anaerobic conditioning tank (1) and/or the anoxic reaction tank (2), and a second outlet branch pipe (15) connected to the subsurface flow constructed wetland (4).

4. The domestic sewage treatment system according to claim 3, wherein said second outlet branch pipe (15) is provided with a second water amount control valve (16), and said first outlet branch pipe (11) is provided with a first water amount control valve (12).

5. The domestic sewage treatment system according to claim 1, wherein an outlet channel (17) is arranged at the end of the subsurface flow constructed wetland (4), and an outlet control valve (18) is arranged at the outlet channel (17).

6. A domestic sewage treatment method, characterized in that the domestic sewage treatment system according to any one of claims 1 to 5 is adopted for sewage treatment, sewage enters an anaerobic adjusting tank (1) through a water inlet pipeline (5), water treated by the anaerobic adjusting tank (1) automatically flows into an anoxic reaction tank (2) through a self-flow channel, water treated by the anoxic reaction tank (2) is pumped into a high water level tank (7) through a lift pump (6), and water after being stabilized by the high water level tank (7) falls from the top of a biological filtration tower unit (3) and flows through the biological filtration tower unit (3) from top to bottom; the water treated by the biological filter tower unit (3) is discharged through the perforated water collecting pipe (8), thereby completing the sewage treatment process.

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