CN110902948B - Rural distributed domestic sewage treatment process and system for strengthening phosphorus removal and recovery - Google Patents

Rural distributed domestic sewage treatment process and system for strengthening phosphorus removal and recovery Download PDF

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CN110902948B
CN110902948B CN201911198427.6A CN201911198427A CN110902948B CN 110902948 B CN110902948 B CN 110902948B CN 201911198427 A CN201911198427 A CN 201911198427A CN 110902948 B CN110902948 B CN 110902948B
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sewage
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anaerobic
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CN110902948A (en
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程翔
吴洪宇
孙德智
邱斌
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Beijing Forestry University
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    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F9/00—Multistage treatment of water, waste water or sewage
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/001—Processes for the treatment of water whereby the filtration technique is of importance
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/105—Phosphorus compounds
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2301/00—General aspects of water treatment
    • C02F2301/08—Multistage treatments, e.g. repetition of the same process step under different conditions
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2303/00—Specific treatment goals
    • C02F2303/14—Maintenance of water treatment installations
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2303/00—Specific treatment goals
    • C02F2303/16—Regeneration of sorbents, filters
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F3/00—Biological treatment of water, waste water, or sewage
    • C02F3/30—Aerobic and anaerobic processes
    • C02F3/302—Nitrification and denitrification treatment

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  • Hydrology & Water Resources (AREA)
  • Engineering & Computer Science (AREA)
  • Environmental & Geological Engineering (AREA)
  • Water Supply & Treatment (AREA)
  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Biological Treatment Of Waste Water (AREA)
  • Purification Treatments By Anaerobic Or Anaerobic And Aerobic Bacteria Or Animals (AREA)

Abstract

A rural distributed domestic sewage treatment process and a treatment system for strengthening phosphorus removal and recovery comprise the following steps: (1) the domestic sewage is filtered by a grid and then enters a regulating tank; (2) then the sewage enters a reaction tank for treatment, the sewage sequentially passes through an anaerobic zone, an anoxic zone and an aerobic zone, the sewage flows through a fixed bed filler with rich biological films in the reaction tank, and pollutants in the sewage are removed through the adsorption and degradation of microorganisms; ferric iron modified charcoal materials are added into an anaerobic zone, reduced into ferrous iron under the action of microorganisms, and combined with phosphate in sewage to form ferrocyanide crystals so as to remove and recover P in sewage; (3) then the effluent is discharged outside after passing through a sand filter. The sewage treatment process and the sewage treatment system simplify the sewage treatment process, are convenient to operate and manage, and reduce the sewage treatment cost.

Description

Rural distributed domestic sewage treatment process and system for strengthening phosphorus removal and recovery
Technical Field
The invention belongs to the technical field of advanced sewage treatment processes, in particular relates to a system for rural distributed domestic sewage treatment, and relates to phosphorus removal and other pollutants in sewage by using anaerobic and aerobic microorganisms and a chemical crystallization method. The sewage treatment method realizes the standard discharge of sewage in rural areas and simultaneously performs phosphorus resource recovery.
Background
Through the latest population survey in 2019 of the State administration of statistics, 45412 villages and towns are counted in China, 23692.7 village households are counted, and 56401 ten thousands of people in the village permanent population account for 41.42 percent of the total population. By 2016, the treatment rate of the administrative village-level sewage in China is only 20%, domestic sewage is discharged at will, rivers, lakes and underground water in peripheral areas are seriously polluted, the health of farmers is harmed, the environmental sanitation of rural areas is influenced, diseases are easy to occur and spread, the rural water environment problem is concerned by governments and various social circles, and the rural domestic sewage problem needs to be solved urgently.
Villages in rural areas of China have the characteristics of wide distribution, low density and dispersed living, and currently, many technical schemes for rural dispersed domestic sewage treatment are provided domestically, including an artificial wetland + stabilization pond sewage treatment technology, an anaerobic/aerobic sewage treatment technology, an anaerobic digestion technology, an MBR technology and the like, but many schemes have the problems of low treatment efficiency, high technical difficulty, more investment, large occupied area and the like. Therefore, in order to really solve the problem of rural domestic sewage treatment, a sewage treatment process which is simple in operation and maintenance, low in cost, convenient to operate and good in effluent quality needs to be developed.
The rural sewage treatment needs to be simple and easy to maintain, while the traditional enhanced biological phosphorus removal technology needs sludge discharge and sludge backflow, and needs to treat phosphorus-containing sludge, so that the operation is complex and is not suitable for rural sewage treatment. Meanwhile, as the eutrophication of water body increases, the removal of nitrogen, phosphorus and other substances in sewage becomes one of the most important tasks in sewage treatment. Phosphorus is an indispensable nutrient substance for human survival, and phosphorite is a non-metal mineral resource which is difficult to regenerate. Since phosphorus ore is mined and used from land and finally flows into the sea, the phosphorus is mined out after decades according to the storage amount of the phosphorus ore in the world known at present, and therefore, the research and development are accelerated and the strategy for recovering the phosphorus is urgently implemented. In recent decades, attention has been paid to the recovery of phosphorus resources, and among them, phosphate crystallization methods have been widely studied, and the main crystallization products are struvite (MAP) and Hydroxyapatite (HAP). The two phosphate crystals can be used for recycling phosphorus resources in sewage, but the reaction needs to be carried out under an alkaline condition, and cannot be recycled in situ, so that the method has great difficulty, great recycling difficulty and high cost in the actual implementation process, and has great significance for improving the phosphorus resource recycling technology.
Disclosure of Invention
The invention aims to solve the problems of rural domestic sewage dispersion, too complex traditional enhanced biological phosphorus removal technology, high implementation difficulty, incapability of popularization, difficult phosphorus resource recovery and the like, provides a novel rural distributed domestic sewage treatment process and a novel rural distributed domestic sewage treatment system, can overcome the problems of low treatment efficiency, high technical difficulty, high investment, large occupied area and the like, and can realize the recovery of phosphorus resources in sewage and reduce the operation and treatment cost by removing phosphorus by a ferrocyanide crystallization method.
According to the first aspect of the invention, a rural distributed domestic sewage treatment process for enhancing phosphorus removal and recovery is provided, which comprises the following steps:
(1) the domestic sewage is filtered by a grid and then enters a regulating tank, and the hydraulic retention time is 5-6 h.
(2) Then the sewage enters a reaction tank for treatment, the sewage sequentially passes through an anaerobic zone, an anoxic zone and an aerobic zone, the sewage flows through a fixed bed filler with rich biological membranes in the reaction tank and is fully contacted with microorganisms in the biological membranes, and pollutants in the sewage are removed through the adsorption and degradation of the microorganisms; an iron source (a ferric iron modified biochar material) is added into an anaerobic zone, reduced into ferrous iron under the action of microorganisms, and combined with phosphate in sewage to form ferrocyanide crystals so as to realize removal and recovery of P in sewage; effluent of nitrified liquid in the aerobic zone flows back to the front end of the anoxic zone through a reflux pump to carry out denitrification for removing N.
(3) Then the effluent is discharged outside after passing through a sand filter.
In the concrete case, the reaction tank adopts a three-gallery plug flow type, sewage enters from the lower end of a water inlet, and flows through fixed bed fillers from an anaerobic zone to an anoxic zone from bottom to top; after flowing through the anaerobic zone, the wastewater enters the anoxic zone from the upper end and flows through the fixed bed filler from the anoxic zone to the aerobic zone from top to bottom; after flowing through the anoxic zone, the water flows into the aerobic zone from the lower end, and flows through the fixed bed filler from the aerobic zone to the water outlet from bottom to top.
In a specific case, the fixed bed packing is made of plastic and is in the shape of a hexagonal honeycomb vertical pipe, and the horizontal through hole is used for strengthening the sufficient contact between the sewage and the biological membrane attached to the surface of the fixed bed packing.
In the anaerobic zone, ferric modified biochar material is arranged at the lower part in the fixed bed filler, and the adding amount is 50-70% of the volume of the filler.
Under the specific condition, the biochar material is taken out periodically to serve as a soil conditioner, and meanwhile, the biochar material has the effect of a phosphate fertilizer, so that phosphorus resources can be effectively recovered.
Particularly, sewage flows from the grid to the regulating tank, to the reaction tank and then to the sand filtration device, and gravity flow is adopted among all structures, so that the operation cost is reduced.
Preferably, the retention time of the sewage in the anaerobic zone is 2 hours, the retention time of the anoxic zone is 2 hours, and the retention time of the aerobic zone is 8 hours.
According to a second aspect of the invention, a rural distributed domestic sewage treatment system for enhancing phosphorus removal and recovery is provided, which comprises a grid, an adjusting tank, a reaction tank and a sand filter device which are connected in sequence; the reaction tank sequentially comprises a water inlet section, an anaerobic section, an anoxic section, an aerobic section and a water outlet section, wherein fixed bed fillers are arranged in the anaerobic section, the anoxic section and the aerobic section, and are hexagonal honeycomb vertical pipes and are transversely perforated; during operation, in the anaerobic section, a ferric iron modified charcoal material is arranged at the lower part in the fixed bed filler, and the adding amount is 50-70% of the volume of the filler; the bottom of the aerobic section is provided with an aerator, and the tail end of the aerobic section is provided with a reflux water pump for refluxing water to the front end of the anoxic section.
Under the optimal condition, the reaction tank adopts a three-gallery plug flow design, the first gallery, the second gallery and the third gallery are arranged side by side, the anaerobic section and the anoxic section are arranged in the first gallery, the second gallery and the third gallery are respectively a first aerobic section and a second aerobic section, a baffle plate with a bottom communicated is arranged between the water inlet section and the anaerobic section, a baffle plate with a top communicated is arranged between the anaerobic section and the anoxic section, a baffle plate with a bottom communicated is arranged between the anoxic section and the first aerobic section, a baffle plate with a tail end communicated is arranged between the first aerobic section and the second aerobic section, and a baffle plate with a top communicated is arranged between the second aerobic section and the water outlet section. Through the optimized design, the reaction tank has compact structure and small occupied area; and sewage all adopts gravity to flow in each section in whole reaction tank, can realize longer dwell time moreover for sewage fully reacts with the biomembrane on fixed bed filler surface fully.
Furthermore, the length, the width and the depth of the first gallery, the second gallery and the third gallery are the same, the length of the anaerobic section and the length of the anoxic section in the first gallery are the same, so that the retention time ratio of the sewage in the anaerobic section, the anoxic section and the aerobic section is 1:1:4, and experiments prove that the design ensures that the sewage achieves the best comprehensive treatment effect in three areas, namely the anaerobic section, the anoxic section and the aerobic section.
Particularly, the hexagonal honeycomb vertical tube of the fixed bed filler is hollow, the side length of the hexagon is 15-30mm, the wall thickness is 0.45-0.80 mm, the aperture of the transverse perforation is phi 10-18mm, and the hole spacing is 15-25 cm. The design can greatly strengthen the full contact between the sewage and the biological film on the surface of the fixed bed filler, and improve the reaction effect.
Preferably, the middle grating (10-40mm) is selected as the grating, and the regular cleaning is carried out by adopting a manual slag removal mode.
Furthermore, a grid plate is arranged at the water inlet and the water outlet of the reaction tank and used for filtering larger suspended matters and floating objects, and the meshes are smaller than 10 mm.
Furthermore, the filler is a carrier of microorganisms, when sewage passes through the filler, the microorganisms and suspended matters in the sewage are adsorbed on the surface of the filler, a viscous microbial community is formed on the surface of the filler, and the viscous microbial community continuously adheres to and grows on the inner surface and the outer surface of the filler to form a biological film. The biological membrane is fully contacted with pollutants in the water body and decomposes the pollutants, so that the water quality is purified. Biofilms are ecosystems consisting of bacteria, fungi, algae, protozoa and metazoa, as well as solid impurities, etc., in which bacteria dominate. Reducing ferric iron into ferrous iron in an anaerobic section by using iron reducing bacteria; denitrifying bacteria convert nitrate nitrogen into nitrogen gas in the anoxic zone; in the aerobic section, various aerobic bacteria decompose and convert organic matters, and nitrifying bacteria convert ammonia nitrogen into nitrate nitrogen.
The invention has the following beneficial effects:
1. the anaerobic/anoxic/aerobic reaction tank adopts the fixed bed filler, sewage flows through the microorganisms attached to the filler, pollutants are adsorbed and degraded under the action of the microorganisms, the sewage is purified, sludge treatment and sludge backflow are not required, the sewage treatment process is simplified, the operation and management are convenient, and the sewage treatment cost is reduced.
2. According to the invention, a ferric iron modified biochar material is added into an anaerobic zone of a reaction tank, ferric iron is reduced into ferrous iron under the action of iron reducing bacteria, and is combined with phosphate ions to form a ferrocyanide crystal, and the biochar is taken out periodically to be used as a soil conditioner. The method not only removes P in the sewage, but also can effectively recover phosphorus resources, and has great economic benefit and environmental benefit.
3. The dephosphorization method is carried out under the condition of neutral or nearly neutral pH, is suitable for domestic sewage treatment, does not need to adjust the pH, overcomes the technical defect of the traditional chemical crystallization method carried out under the alkaline condition, saves the chemical agent adding cost and reduces the sewage treatment cost.
4. The invention carries out advanced treatment of sewage through the sand filtration device, further removes pollutants in the sewage and has good effluent quality.
5. The invention has simple process flow, good treatment effect, low cost and small occupied area, is suitable for rural distributed domestic sewage treatment and is beneficial to large-scale popularization.
Drawings
FIG. 1 is a schematic flow diagram of the treatment process of the present invention.
FIG. 2 is a schematic top view of the AAO reaction tank in the main process of the present invention.
FIG. 3 is a schematic expanded sectional view of the AAO reaction tank of the main process of the invention.
FIG. 4 is a schematic view of the fixed bed packing structure of the present invention.
FIG. 5 is a schematic structural view of a sand filtration device according to the present invention.
Wherein the reference symbols in the drawings represent respectively:
1. the device comprises a water inlet section, 2, an anaerobic section, 3, an anoxic section, 4, an aerobic section, 5, a water outlet section, 6, a water inlet, 7, a water outlet, 8, a filler, 9, an iron source, 10, a first partition plate, 11, a second partition plate, 12, a third partition plate, 17, a fourth partition plate, 13, a fifth partition plate, 14, an aerator, 15, a reflux water pump, 16, a reflux pipeline, 20, a first gallery, 30, a second gallery, 40, a third gallery, 21, a sand cylinder, 22, sand, 23, an upper three-way valve, 24, a lower three-way valve, 25, a water inlet pipe, 26, a backwashing pipe, 27, a water outlet pipe, 41, a first aerobic section, 42, a second aerobic section, 90, a hollow vertical pipe, 91 and a cross hole.
Detailed Description
The patent is further described in detail below with reference to examples. The examples are given solely for the purpose of illustration and are not to be construed as limitations on the scope of the invention, as modifications and alterations in detail and form may be made to the present invention without departing from its scope.
First, the present invention is introduced to a rural decentralized domestic sewage treatment system (or treatment facility) for enhancing phosphorus removal and recovery. Referring to fig. 1, the treatment system of the present invention mainly comprises a grating, a conditioning tank, a reaction tank and a sand filtration device which are connected in sequence by pipes. The reaction tank is a main device of the treatment system and is mainly divided into three zones (sections), namely an anaerobic zone (section), an anoxic zone (section) and an aerobic zone (section), and the reaction tank is also commonly called as an AAO reaction tank.
The present invention is designed specifically for the structure and internal filling of the AAO reaction tank, and is described in detail below with reference to FIGS. 2-4.
Referring first to fig. 2, the reaction tank is designed in a three-gallery plug flow manner, the first gallery 20, the second gallery 30 and the third gallery 40 are arranged side by side, the anaerobic section 2 and the anoxic section 3 are arranged in the first gallery 20, the second gallery 30 is a first aerobic section 41, and the third gallery 40 is a second aerobic section 42. Referring to fig. 3, the reaction tank comprises a water inlet section 1, an anaerobic section 2, an anoxic section 3, an aerobic section 4 and a water outlet section 5 in sequence. The water inlet section 1 is provided with a water inlet 6 for receiving sewage adjusted by the adjusting tank. A first clapboard 10 with the bottom capable of being communicated is arranged between the water inlet section 1 and the anaerobic section 2. A second clapboard 11 with the top part capable of being communicated is arranged between the anaerobic section 2 and the anoxic section 3. A third clapboard 12 with the bottom capable of being communicated is arranged between the anoxic section 3 and the first aerobic section 41. A fourth partition 17 with a communicable end is arranged between the first aerobic section 41 and the second aerobic section 42, that is, the end of the first aerobic section 41 is communicated with the initial section of the second aerobic section 42. A fifth clapboard 13 with the top part capable of being communicated is arranged between the second aerobic section 43 and the water outlet section 5. The water outlet section 5 is provided with a water outlet 7, and the water outlet 7 is connected with the sand filter.
In a specific case, the anaerobic section 2, the anoxic section 3 and the aerobic section 4 are all fixedly provided with fillers 8. The filler 8 is a carrier of microorganisms, when sewage passes through the filler 8, the microorganisms and suspended matters in the sewage are adsorbed on the surface of the filler 8, a viscous microbial community is formed on the surface of the filler 8, and the viscous microbial community continuously adheres to and grows on the inner surface and the outer surface of the filler 8 to form a biological film. The biological membrane is fully contacted with pollutants in the water body and decomposes the pollutants, so that the water quality is purified. Biofilms are ecosystems consisting of bacteria, fungi, algae, protozoa and metazoa, as well as solid impurities, etc., in which bacteria dominate.
With particular reference to fig. 4, the invention is further characterized in that: the filler 8 is formed by arranging a plurality of regular hexagonal (or regular hexagonal) hollow vertical pipes 90, the whole body is in a honeycomb shape, and each hollow vertical pipe 90 is transversely perforated; the side length of the hexagon is 15-30mm, the wall thickness is 0.45-0.80 mm, the aperture of the transverse hole 91 is phi 10-18mm, and the hole distance is 15-25 cm. Through the design, the full contact of the sewage and the biological film on the surface of the fixed bed filler is greatly strengthened, and the reaction effect is improved.
Before the sewage treatment system runs, an iron source 9 is arranged at the lower part of the filler 8 in the anaerobic section 2 in advance, the iron source 9 is a ferric iron modified biochar material, and the adding amount is 50-70% of the volume of the filler 8. The biological carbon is used as a carrier of the ferric iron source, and the abundant surface area of the biological carbon is utilized, so that the ferric iron source is uniformly distributed and has high loading capacity; in addition, during sewage treatment, the biochar can further adsorb pollutants in the sewage.
The ferric iron modified biological carbon material has two preparation methods, which are respectively as follows: adding biochar with the particle size of 0.5-1 mm into alkali liquor to form mixed liquor, mixing the mixed liquor with a ferric salt solution, adding water for dilution when red precipitates are generated, stirring the mixed liquor for 2 hours at 65-70 ℃, and then filtering and drying the mixed liquor. The alkali liquor is sodium hydroxide (NaOH) or potassium hydroxide (KOH), and the concentration is 5 mol/L; the ferric salt solution is ferric nitrate (Fe (NO)3)3) Or ferric chloride (FeCl)3) The concentration is 1 mol/L. The ratio of the biochar to the alkali liquor is 1g:30 mL; the volume ratio of the mixed solution to the ferric salt solution is 1: 2.② adding biochar with the particle size of 0.5-1 mm into ferrous sulfate (FeSO)4) Aerating the solution for 1h at normal temperature, and then filtering and drying. In the process, the concentration of dissolved oxygen is 4mg/L, the solid-to-liquid ratio is 1:2, and the concentration of a ferrous sulfate solution is 1 mol/L. Wherein, the prepared iron modified biochar has small particle size, large specific surface area and low cost,secondly, the preparation method is simple, the reaction condition is mild, the required time is short, and the finished product has a good adsorption effect.
Preferably, the middle grating (10-40mm) is selected as the grating, and the regular cleaning is carried out by adopting a manual slag removal mode.
Furthermore, a grid plate is arranged at the water inlet and the water outlet of the AAO reaction tank and used for filtering larger suspended matters and floating objects, and the mesh is smaller than 10 mm.
Specifically, the bottom of the aerobic section 4 is provided with an aerator 14, the aerator 14 adopts blast aeration, preferably a roots blower, the aerator 14 adopts micropore aeration, and the distance between the aerator 14 and the bottom of the tank is about 0.2 m. The tail end of the aerobic section 4 is provided with a return water pump 15 which is connected with the front end of the anoxic section 3 through a return pipeline 16.
Furthermore, the power supply system of the invention preferably adopts solar power supply, and the solar power supply system is respectively connected with the reflux water pump and the aeration equipment. Of course, conventional power supply systems may also be connected where the power supply is convenient and appropriate.
Referring specifically to fig. 5, the sand filtration device of the present invention is preferably a shallow sand filter, which is composed of a standard high-speed sand cylinder unit, wherein sand 22 is filled in a sand cylinder 21, the sand is quartz sand, manganese sand, anthracite, etc., and the grain size of the sand is generally 0.5-1.2 mm. The effluent of the reaction tank is connected with the top end of a sand cylinder 21 through a water inlet pipe 25, and an upper three-way valve 23 is connected between the effluent and the sand cylinder. The lower end of the sand cylinder 21 is connected with a lower three-way valve 24, a backwashing pipe 26 is connected between the water inlet pipe 25 and the lower three-way valve 24, and the other end of the lower three-way valve 24 is connected with a water outlet pipe 27. The sewage passes through the shallow sand filter, so that pollutants in water can be further removed, macromolecular solid particles and colloids in the water are intercepted, and the water is clarified. The shallow sand filter has a filtering mode and a backwashing mode, and backwashing operation can be carried out periodically. The switching between the filtration mode and the backwashing mode of the shallow sand filter can be fully automatically controlled, wherein the upper three-way valve 23 and the lower three-way valve 24 preferably adopt electromagnetic valves, a pressure sensor is arranged in the sand cylinder 21 and connected with the electromagnetic valves, and the internal head loss is increased along with the continuous accumulation of impurities in the sand layer. When the loss of the water inlet pressure head and the water outlet pressure head reaches a set value, the system automatically activates the electromagnetic valve to enable the electromagnetic valve to be switched to a backwashing state, manual operation is not needed, and the device is convenient to install and does not need maintenance.
The following description specifically introduces the use of the treatment system described above for decentralized domestic sewage treatment in rural areas, comprising the following steps:
(1) the domestic sewage is filtered by a grid and then enters a regulating tank, and the hydraulic retention time is 5-6 h.
(2) Then the sewage enters a reaction tank for treatment, the sewage sequentially passes through an anaerobic zone, an anoxic zone and an aerobic zone, effluent of nitrified liquid in the aerobic zone flows back to the front end of the anoxic zone through a reflux pump to carry out denitrification to remove N, and the reflux ratio is 200%.
(3) Then the effluent is discharged outside after passing through a sand filter.
Wherein, the sewage flows through a fixed bed filler with rich biological films in the reaction tank, fully contacts with microorganisms in the biological films, and removes pollutants in the sewage through the adsorption and degradation of the microorganisms; by adding an iron source (a ferric iron modified biochar material) into the anaerobic zone, ferric iron is reduced into ferrous iron by the iron reducing bacteria, and the ferrous iron is combined with phosphate in sewage to form ferrocyanide crystals so as to remove and recover P in the sewage. Denitrifying bacteria convert nitrate nitrogen into nitrogen gas in the anoxic zone; in the aerobic section, various aerobic bacteria decompose and convert organic matters, and nitrifying bacteria convert ammonia nitrogen into nitrate nitrogen.
Under the specific condition, after the system runs for a period of time, the biochar material is taken out to be used as a soil conditioner, and meanwhile, the biochar material has the effect of a phosphate fertilizer and can effectively recover phosphorus resources.
Wherein the filtering flow of the sand filtering device is 30.6m3/h–2500m3H, backwashing time of 2-3min and backwashing water quantity<3m3，
DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION
A small sewage treatment station is built in a village for treating domestic sewage of village residents, the village has 200 villages in total, about 800 people, and the highest daily produced sewage amount is 200m3The average sewage quantity per day and the maximum daily hour is 8.3m3H is used as the reference value. Setting the retention time of the regulating reservoir to be 6h and the capacity of the regulating reservoir to be 50m3. The residence time of the reaction tank is 12h, and the volume is 100m3The depth of the pond is 2m,the pool area is 50 square meters. The reaction tank has three galleries, and the width of each gallery is 1.5m, the total width of the reaction tank is 4.5m, and the total length is 12m (see fig. 2, the width is in the left-right direction, and the length is in the up-down direction). The sewage stays for 2 hours in the anaerobic section, and the flowing length is 6 m; the residence time of the anoxic section is 2h, and the flow length is 6 m; the aerobic section has a retention time of 8 hours and the length of the flow-through is 24 m.
The indexes of the water inlet pollutants are as follows: SS is 150 mg/L; COD is 300 mg/L; BOD5＝160mg/L；NH4 +-N＝35mg/L；TN＝45mg/L；TP＝4mg/L。
After the system operates, the SS of the effluent is stably lower than 20 mg/L; the COD of the effluent is stably lower than 60 mg/L; BOD of the effluent5The stability is lower than 20 mg/L; outlet water NH4 +-N is stable below 8 mg/L; the TN of the effluent is stably lower than 20 mg/L; the effluent TP was stable at less than 1 mg/L.

Claims (8)

1. A rural distributed domestic sewage treatment process for strengthening phosphorus removal and recovery is characterized by comprising the following steps:
(1) the domestic sewage is filtered by a grid and then enters a regulating tank, and the hydraulic retention time is 5-6 h;
(2) then the sewage enters a reaction tank for treatment, the sewage sequentially passes through an anaerobic zone, an anoxic zone and an aerobic zone, the sewage flows through a fixed bed filler with rich biological membranes in the reaction tank and is fully contacted with microorganisms in the biological membranes, and pollutants in the sewage are removed through the adsorption and degradation of the microorganisms; in the anaerobic zone, a ferric iron modified charcoal material is arranged at the lower part in the fixed bed filler, and the adding amount is 50-70% of the volume of the filler; ferric iron modified charcoal materials are added into an anaerobic zone, reduced into ferrous iron under the action of microorganisms, and combined with phosphate in sewage to form ferrocyanide crystals so as to remove and recover P in sewage; effluent of nitrifying liquid in the aerobic zone reflows to the front end of the anoxic zone through a reflux pump to carry out denitrification to remove N;
(3) then the effluent is discharged outside after passing through a sand filtering device;
(4) the biochar material is taken out periodically to serve as a soil conditioner, and meanwhile, the biochar material has the effect of a phosphate fertilizer, so that phosphorus resources can be effectively recycled.
2. The rural distributed domestic sewage treatment process of claim 1, wherein the reaction tank adopts a three-gallery plug flow type, sewage enters from the lower end of the water inlet, and flows through fixed bed packing from the anaerobic zone to the anoxic zone from bottom to top; after flowing through the anaerobic zone, the wastewater enters the anoxic zone from the upper end and flows through the fixed bed filler from the anoxic zone to the aerobic zone from top to bottom; after flowing through the anoxic zone, the water flows into the aerobic zone from the lower end, and flows through the fixed bed filler from the aerobic zone to the water outlet from bottom to top.
3. The rural distributed domestic sewage treatment process of claim 1, wherein the fixed bed packing is made of plastic and is shaped as a hexagonal honeycomb vertical tube, and the fixed bed packing is perforated transversely to strengthen the full contact between the sewage and the biological membrane attached to the surface of the fixed bed packing.
4. The rural distributed domestic sewage treatment process of claim 1, wherein the sewage flows from the grid to the adjusting tank to the reaction tank and then to the sand filtration device, and gravity flow is adopted among all structures.
5. The rural distributed domestic sewage treatment process of claim 1, wherein the residence time of the sewage in the anaerobic zone is 2 hours, the residence time in the anoxic zone is 2 hours, and the residence time in the aerobic zone is 8 hours.
6. A rural distributed domestic sewage treatment system for strengthening phosphorus removal and recovery is characterized by comprising a grid, an adjusting tank, a reaction tank and a sand filter device which are sequentially connected; the reaction tank sequentially comprises a water inlet section, an anaerobic section, an anoxic section, an aerobic section and a water outlet section, wherein fixed bed fillers are arranged in the anaerobic section, the anoxic section and the aerobic section, and are hexagonal honeycomb vertical pipes and are transversely perforated; during operation, in the anaerobic section, a ferric iron modified charcoal material is arranged at the lower part in the fixed bed filler, and the adding amount is 50-70% of the volume of the filler; the bottom of the aerobic section is provided with an aerator, and the tail end of the aerobic section is provided with a reflux water pump for refluxing water to the front end of the anoxic section.
7. The rural distributed domestic sewage treatment system of claim 6, wherein the reaction tank is designed in a three-gallery plug flow manner, the anaerobic section and the anoxic section are arranged in the first gallery, the second and third galleries are respectively a first aerobic section and a second aerobic section, a bottom-communicable partition is arranged between the water inlet section and the anaerobic section, a top-communicable partition is arranged between the anaerobic section and the anoxic section, a bottom-communicable partition is arranged between the anoxic section and the first aerobic section, a tail-end-communicable partition is arranged between the first aerobic section and the second aerobic section, and a top-communicable partition is arranged between the second aerobic section and the water outlet section.
8. The rural distributed domestic sewage treatment system of claim 6, wherein the hexagonal honeycomb vertical tube of the fixed bed packing is hollow, the side length of the hexagon is 15-30mm, the wall thickness is 0.45-0.80 mm, the aperture of the transverse perforation is phi 10-18mm, and the hole spacing is 15-25 cm.
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CN109626771A (en) * 2018-12-13 2019-04-16 广东省生态环境技术研究所 A method of promote anaerobically digested sludge heavy metal stable
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CN112221466B (en) * 2020-09-30 2021-08-10 中国地质大学（北京） Phosphate-iron oxide modified biochar composite material, and preparation method and application thereof
CN114477663B (en) * 2022-03-30 2022-07-08 北京林业大学 System and method for preparing large-size hematite based on kitchen waste hydrothermal carbonization liquid
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