Water treatment system coupled with combination of anoxic biofilter and constructed wetland

Abstract

The invention provides a water treatment system combining a coupled anoxic biological filter and a constructed wetland, which belongs to the technical field of water treatment, and has the technical key points that sewage is collected by a pipe network, flows into a water collecting tank and then enters a regulating / anoxic tank through a lifting pump, a carrier is provided for microorganisms through a solid carbon source in the tank, and slow-release supplement of the carbon source is realized at the same time; then, the sewage is conveyed to a biological filter and a contact oxidation pond through a lifting pump after the denitrification reaction is enhanced to remove total nitrogen, COD and ammonia nitrogen are removed through a carbon oxidation reaction and a nitration reaction, effluent enters an efficient clarification pond, most of total phosphorus and SS are removed through chemical phosphorus removal and a coagulation precipitation method, the effluent overflows into an artificial wetland, and the effluent is subjected to plant-microorganism-filler comprehensive treatment, so that the effluent is subjected to denitrification treatment. And pollutants are deeply purified and discharged after reaching the standard. By adopting the water treatment method provided by the invention, the effluent quality can be improved to the first-grade B emission standard.

Description

Technical Field

[0001] The invention belongs to the technical field of water treatment, and in particular relates to a water treatment system combining an anoxic biological filter and an artificial wetland. Background Art

[0002] The combined biofilter-constructed wetland process for treating rural domestic sewage has the characteristics of stable effect, low investment, simple management and low operating costs. It is widely used in rural domestic sewage treatment practice and is the main process for rural domestic sewage treatment facilities in Shanghai, accounting for 26.6%.

[0003] In the early stage of construction, the process design effluent standard mainly implemented the secondary standard of the "Interim Regulations on Effluent Quality of Rural Domestic Wastewater Treatment Projects in Shanghai" (Shanghai Water Affairs

[2010] No. 323). In 2019, Shanghai issued the "Shanghai Rural Domestic Wastewater Treatment Facility Water Pollutant Emission Standard" (DB31 / T1163-2019), and the water pollutant emission control indicators were adjusted from 4 to 8, and the first-level A or first-level B standards were implemented according to the water environment function area division of the discharge water area. In order to meet the management requirements of the current standards, it is necessary to upgrade the biological filter-constructed wetland combined process treatment facilities with the original secondary design effluent standard.

[0004] like Figure 1 As shown, the original process flow is: domestic sewage is collected through the pipe network 100 and flows into the regulating tank 200 for pretreatment. A screen 201 is installed in the regulating tank 200 to remove granular debris. Then, the sewage enters the biological filter 300 for treatment through a lifting pump. The effluent from the filter enters the intermediate tank 400 for sedimentation. After overflow, the sewage enters the artificial wetland 500 for treatment. Part of the sewage flows back to the regulating tank 200 and is discharged into the river after being treated in the artificial wetland 500.

[0005] The original process for removing pollutants mainly relied on pretreatment in regulating tanks, biofilm treatment in biofilters and ecological treatment in artificial wetlands, and the treatment effect could not meet the current emission standards.

[0006] The main reasons are:

[0007] (1) Poor anoxic environment affects the denitrification effect. The regulating tank of the original process serves as an anoxic tank. Due to the large differences in the amount of rural domestic sewage in different periods of time, the hydraulic retention time of sewage in the regulating tank is unstable. In addition, the dissolved oxygen concentration of the return water is high, and the regulating tank cannot form a strict anoxic environment, which reduces the denitrification effect.

[0008] (2) Structural defects in the biofilter reduce the pollutant treatment efficiency. The original process of the biofilter uses plastic baskets to encapsulate the filler and lay it out in layers. The plastic baskets deform when they are compressed, which can easily cause uneven water flow through the filter layer and insufficient water drop. In the same filter layer, some areas have large water flow, while some areas have no water flow and dry up.

[0009] (3) The phosphorus removal effect is unstable. The phosphorus removal capacity of artificial wetland vegetation is limited and will fluctuate seasonally. The phosphorus removal effect is good in spring and summer when the vegetation is dense, and poor in autumn and winter when the plants wither. Summary of the invention

[0010] The purpose of the present invention is to solve the problems existing in the above-mentioned prior art and to provide a water treatment system which couples anoxic biological filter with artificial wetland.

[0011] The technical solution of this application is as follows:

[0012] A water treatment system that couples anoxic biofilters and artificial wetlands, comprising an inlet pipe network, a water collection tank, a regulating / anoxic tank, a biofilter, a contact oxidation tank, a high-efficiency clarification tank, an artificial wetland, and an outlet pipe network that are sequentially connected according to the direction of water flow;

[0013] The water inlet pipe network is used to collect sewage and transfer the sewage to the water collection tank;

[0014] The water collection tank is used to remove silt and regulate water volume;

[0015] The regulating / anoxic tank is provided with a floating body to suspend a solid carbon source, which provides a carrier for microorganisms and realizes a slow-release supplement of the carbon source; the regulating / anoxic tank is used to denitrify sewage and regulate water volume;

[0016] The biofilter uses a composite filler to be filled in multiple levels, which are, from top to bottom, a biological blanket layer, a porous medium cotton layer, a volcanic rock layer, a ceramsite layer, and a modified biological material layer; the biological blanket layer and the porous medium cotton layer are both used to filter particulate matter in sewage; the volcanic rock layer, the ceramsite layer, and the modified biological material layer are all used to absorb impurities in sewage;

[0017] The high-efficiency clarification tank is provided with a phosphorus removal device and a honeycomb inclined tube, and the high-efficiency clarification tank is used for phosphorus removal and water clarification.

[0018] Furthermore, a coarse and fine grid is provided in the middle of the water collection pool to divide the water collection pool into two parts, left and right.

[0019] The water inlet pipe network is connected to the left part of the water collection tank and a gravity mud-water separation device is provided on the left part of the water collection tank;

[0020] A first lifting pump is arranged at the right part of the water collection tank, and the sewage in the water collection tank is transported to the regulating / anoxic tank through the first lifting pump.

[0021] Furthermore, the regulating / anoxic tank is provided with a second lifting pump; the sewage in the regulating / anoxic tank is transported to the biological filter tank through a fifth pipeline by the second lifting pump.

[0022] Furthermore, the biofilter is provided with a third boost pump; the third boost pump is connected to the reflux system.

[0023] Furthermore, the water treatment system also includes: the reflux system, including: a guide valve, a first pipeline, a second pipeline, a third pipeline, and a fourth pipeline; the first pipeline, the second pipeline, the third pipeline, and the fourth pipeline are all connected to the guide valve; the first pipeline is connected to the regulation / anoxic tank; the second pipeline is connected to the second boost pump, the third pipeline is connected to the third boost pump, and the fourth pipeline is connected to the contact oxidation tank; through the reflux system, the flow rate of the solution coming in from the second boost pump and the third boost pump into the first pipeline or the fourth pipeline can be controlled.

[0024] Furthermore, the water distribution facility of the biofilter is composed of a balancing water tank and a tooth weir water distribution tank, wherein the balancing water tank is newly equipped with automatic backwashing and liquid level control functions to ensure uniform water distribution in the biofilter;

[0025] The balancing water tank can filter impurities with a particle size greater than 3mm in the water inlet of the anoxic pool to avoid clogging of the filter material; at the same time, the balancing water tank can also regulate the liquid level in the balancing water tank to ensure the stability of the water level in the water distribution tank;

[0026] The regulating / anoxic tank normally inflows water, and after being filtered through the front-end filter, the water is discharged to the rear end of the balancing water tank, and flows into the tooth weir water trough through the outlet pipe. To ensure the stability of the water level in the tooth weir water trough, the second lifting pump is controlled by the liquid level sensor and the liquid level control valve in the balancing water tank to always ensure that the water level in the balancing water tank is higher than the outlet pipe. According to the actual operation data, backwashing is performed at regular intervals, and the backwashing valve adopts a PLC or PAC control system. The backwashing clean water comes from the rear-end contact oxidation tank, and the flushing wastewater is discharged into the anoxic tank.

[0027] Furthermore, a micro-nano aeration membrane is provided at the bottom of the contact oxidation pond, and a light suspended filler is provided in the middle.

[0028] Further, the water is treated by the following steps:

[0029] S100, sewage is collected through the water inlet network and flows into the collection tank;

[0030] S200, the water collection pool enters the regulating / anoxic pool through the first lifting pump, and the solid carbon source is suspended by the floating body in the pool, providing a carrier for the microorganisms while realizing the slow release supplement of the carbon source, thereby strengthening the denitrification reaction to remove total nitrogen and then transporting it to the biological filter and contact oxidation pool;

[0031] S300 removes COD and ammonia nitrogen through carbon oxidation reaction and nitrification reaction. The effluent flows into the high-efficiency clarification tank by gravity. After most of the total phosphorus and SS are removed by coagulation and sedimentation, the overflow enters the artificial wetland. After comprehensive treatment by plants, microorganisms and fillers, the pollutants are purified and finally transported to the effluent network.

[0032] Furthermore, a wall is provided in the regulating / anoxic tank, and a row of 10 cm×10 cm square holes are provided on the wall to connect the tank body; the wall is used to divide the functional area of ​​the regulating / anaerobic tank to improve the anaerobic environment; the agitator pump and the suspended solid carbon source are divided into different areas by the partition wall, and the influent of the regulating / anoxic tank contains a certain amount of dissolved oxygen. The stirring effect of the agitator pump can reduce the dissolved oxygen in the water, and the sewage overflows to the solid carbon source side through the square holes on the wall. The anoxic environment of the sewage overflowing to the solid carbon source is more stable, which is conducive to the denitrification reaction;

[0033] Lay a gravel layer on the surface of the conditioning / anoxic tank;

[0034] A variable frequency water pump is installed at the bottom of the regulating / anoxic pool, and high and low water level gauges are installed on the pool body; the variable frequency water pump adjusts the output water volume through the measured signal of the level gauge to achieve water level control of the regulating / anoxic pool, ensuring that the anoxic pool maintains a stable anoxic environment.

[0035] Furthermore, the pollutant concentrations of the inlet and outlet of the regulating / anoxic tank satisfy the following relationship:

[0036] c i =c0·e -0.025t ;

[0037] The pollutant concentrations of the inlet and outlet of the biofilter satisfy the following relationship:

[0038] c i =c0·e -0.03t ;

[0039] Among them, c i is the effluent pollutant concentration, c0 is the influent pollutant concentration, and t is the hydraulic retention time of the pollutant.

[0040] The advantages of the technical solution of the present invention are mainly reflected in:

[0041] First, the treatment process after upgrading and increasing efficiency in this application is optimized and upgraded to the "coupled anoxic biological filter + artificial wetland" combination process based on the original "biological filter + artificial wetland" combination process. It not only continues the characteristics of the original process with simple maintenance and low energy consumption, but also upgrades and strengthens the nitrogen and phosphorus removal capabilities. It is a biological + ecological comprehensive biofilm treatment process.

[0042] (1) Solid carbon source fillers are arranged in the regulating / anoxic tank to provide attachment carriers for facultative anaerobic bacteria and continuously release the carbon source required for denitrification reaction, thereby enhancing the treatment efficiency of low-concentration sewage and efficiently removing total nitrogen in the anoxic tank. A new wall is built in the regulating / anoxic tank. A row of 10cm×10cm square holes is set 20-30cm below the liquid level to connect the tank body; the wall is used to divide the functional area of ​​the regulating / anaerobic tank and improve the anaerobic environment. The stirring pump and the suspended solid carbon source are separated into different areas by a partition wall. The influent of the regulating / anoxic tank contains a certain amount of dissolved oxygen. The stirring action of the stirring pump can reduce the dissolved oxygen in the water. The sewage overflows to the solid carbon source side through the square hole on the wall. The anoxic environment of the sewage overflowing to the solid carbon source is more stable, which is conducive to denitrification reaction. In addition, a gravel layer of appropriate size (such as 5-20mm) is laid on the surface of the regulating / anoxic tank to increase the surface roughness of the tank body, improve the Reynolds number of the water flow, promote turbulence formation, accelerate the exchange of sewage and air, effectively remove dissolved oxygen, and optimize the sewage treatment effect.

[0043] (2) The composite filler of the biological filter is a combination of multi-layer inorganic filler and organic polymer filler. The filler surface has abundant micropores, huge specific surface area, and good hydrophilicity. The modular structural unit is designed based on the characteristics of different groups of microorganisms. The removal rate of COD by heterotrophic bacteria in the biofilm can be stably maintained between 70% and 80%, and the removal rate of ammonia nitrogen by nitrifying bacteria can be stably maintained at more than 85%.

[0044] (3) As a supplement and reinforcement link of the aerobic process section, the contact oxidation tank further consolidates and improves the system's ability to resist shock loads, and at the same time greatly enhances the treatment effect under winter and low temperature conditions.

[0045] (4) The addition of a high-efficiency clarification tank and a phosphorus removal dosing system can achieve high-efficiency phosphorus removal and SS removal capabilities with a small amount of reagent addition.

[0046] (5) Air lift sludge discharge devices are added to the water collection tank, micro-nano aerated biological filter tank, and high-efficiency clarification tank to discharge the sludge-containing sewage into the gravity sludge-water separation device installed in the water collection tank. The sludge can be easily disposed of through daily maintenance, avoiding sludge accumulation and re-release of pollutants in the treatment tank.

[0047] Second, the method of the present application: the sewage is collected through the pipe network and flows into the collection pool, and then enters the regulating / anoxic pool through the lifting pump. The solid carbon source in the pool provides a carrier for the microorganisms while realizing the slow-release supplement of the carbon source, thereby strengthening the denitrification reaction to remove the total nitrogen, and then is transported to the biological filter and the contact oxidation pool by the lifting pump. COD and ammonia nitrogen are removed through carbon oxidation reaction and nitrification reaction. The effluent flows into the high-efficiency clarification pool by gravity. After most of the total phosphorus and SS are removed through coagulation and sedimentation, the overflow enters the artificial wetland, and is deeply treated by the comprehensive treatment of plants, microorganisms and fillers to meet the discharge standards.

[0048] Third, this application proposes the relationship between the pollutant concentrations of the inlet and outlet of the conditioning / anoxic tank and the pollutant concentrations of the inlet and outlet of the biofilter. The following formula is used to reflect the influence of factors such as pollutant concentration and hydraulic retention time on the anoxic biochemical reaction / biofilm reaction process, and further guide the application effect of treatment facilities on sewage treatment.

[0049] Relationship between pollutant concentrations in the inlet and outlet of the regulating / anoxic pool: c i =c0·e -0.025t ;

[0050] Relationship between the inlet and outlet pollutant concentrations of the biofilter: c i =c0·e -0.03t ;

[0051] Among them, c i is the effluent pollutant concentration, c0 is the influent pollutant concentration, and t is the hydraulic retention time of the pollutant. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] The present invention will be further described in detail below in conjunction with the embodiments in the accompanying drawings, but this does not constitute any limitation to the present invention.

[0053] Figure 1 It is a structural diagram of a water treatment system in the prior art.

[0054] Figure 2 It is a structural diagram of the water treatment system of this application.

[0055] Figure 3 It is the removal effect of COD, NH3-N, TN, TP and SS.

[0056] Figure 4 It is the pH result diagram of each treatment structure.

[0057] Figure 5 This is the COD removal effect monitoring result diagram.

[0058] Figure 6 This is the monitoring result diagram of NH3-N removal effect.

[0059] Figure 7 This is the TN removal effect monitoring result diagram.

[0060] Figure 8 This is the TP removal effect monitoring result diagram.

[0061] Fig. 9 This is a graph showing the monitoring results of the suspended solids (ss) removal effect.

[0062] Fig.10 This is a diagram of the structure of the regulation / anoxic pool.

[0063] Fig.11 It is a cross-sectional view of the biofilter.

[0064] Fig.12 This is a top view of the biofilter.

[0065] Fig.13 It is a three-dimensional design schematic diagram of the balancing water tank.

[0066] The following are the descriptions of the reference numerals:

[0067] Existing domestic sewage pipe network 100, existing regulating tank 200, existing grille 201, existing biological filter 300, existing intermediate tank 400, existing artificial wetland 500;

[0068] Water treatment system 2000, water inlet network 2010, water collection tank 2020, regulation / anoxic tank 2030, biological filter 2040, contact oxidation tank 2050, high-efficiency clarification tank 2060, artificial wetland 2070, water outlet network 2080, return system 2090;

[0069] Grille 2023, gravity mud-water separation device 2022, first lift pump 2021;

[0070] A second lifting pump 2031 and a floating body suspending a solid carbon source 2032;

[0071] Ecological blanket layer 2041, porous medium cotton layer 2042, volcanic rock layer 2043, ceramsite layer 2044, modified biological material layer 2045;

[0072] third lift pump 2046;

[0073] Balancing water tank 2141, tooth weir water tank 2142, liquid level sensor 21411, liquid level control valve 21412, front end filter 21413, backwash pipe 2143, backwash pump 2144. DETAILED DESCRIPTION

[0074] The purpose, advantages and features of the present invention will be explained by the non-limiting description of the following preferred embodiments. These embodiments are only typical examples of the application of the technical solution of the present invention, and any technical solution formed by equivalent replacement or equivalent transformation falls within the scope of protection claimed by the present invention.

[0075] Example 1: A rural domestic sewage treatment station upgrading project in a town in Jiading District, Shanghai

[0076] 1. Project Overview

[0077] This project is a rural domestic sewage treatment station upgrading and renovation project in a town in Jiading District, Shanghai. The rural domestic sewage treatment station was built in 2017. The service scope is not a rural tourism area. There are 39 farmers and a permanent population of 380. The sewage collection system pipe network is 3.2 kilometers long. The design scale of the treatment station is 40 tons / day. The designed effluent water quality standard is the second-level standard, which is a fully buried biofilter + artificial wetland process. In 2023, the station will be upgraded and the effluent water quality will be upgraded to the first-level B standard.

[0078] There are many cases of farmers renting out their land in this service area, the floating population fluctuates greatly, the water quality and quantity of rural domestic sewage fluctuate greatly, and there is a certain amount of external water intrusion into the pipeline network.

[0079] 2. Design inlet and outlet water quality

[0080] Table 1 gives the design inlet and outlet water qualities.

[0081] Table 1 Designed inlet and outlet water quality

[0082]

[0083] 3. Ideas for process transformation

[0084] Reconstruct the original facilities and structures, optimize the process into a multi-stage coupled biological module, improve the pre-process, add subsequent processes, enhance the nitrogen removal and phosphorus removal effects of the process, and ensure that the effluent quality is stable and meets the standards.

[0085] 1) In order to solve the problem of poor anoxic environment in pretreatment, the partition wall in the original regulating tank was transformed into a water collection tank and a regulating / anoxic tank. A new grid was installed in the water collection tank to remove large particle pollutants, and a suspended solid carbon source was installed in the regulating / anoxic tank.

[0086] like Fig.10As shown in the figure, a detailed design drawing of the regulating / anoxic tank is given. A new wall is built in the regulating / anoxic tank. A row of 10cm×10cm square holes are set at 20-30cm below the liquid level to connect the tank body; the wall is used to divide the functional area of ​​the regulating / anaerobic tank to improve the anaerobic environment. The mixing pump and the suspended solid carbon source are divided into different areas by the partition wall. The influent of the regulating / anoxic tank contains a certain amount of dissolved oxygen. The stirring action of the mixing pump can reduce the dissolved oxygen in the water. The sewage overflows to the solid carbon source side through the square holes on the wall. The anoxic environment of the sewage overflowing to the solid carbon source is more stable, which is conducive to denitrification. In addition, a gravel layer of appropriate size (such as 5-20mm) is laid on the surface of the regulating / anoxic tank. By increasing the surface roughness of the tank body, the Reynolds number of the water flow is increased, turbulence formation is promoted, the exchange of sewage and air is accelerated, the dissolved oxygen is effectively removed, and the sewage treatment effect is optimized.

[0087] A variable frequency water pump is installed at the bottom of the regulating / anoxic pool, and high and low water level gauges are installed on the pool body. The variable frequency water pump adjusts the output water volume through the measured signal of the level gauge to achieve water level control of the regulating / anoxic pool, ensuring that the anoxic pool maintains a stable anoxic environment.

[0088] formula:

[0089] The degradation of pollutants in sewage in the conditioning / anoxic tank shows a certain relationship with the hydraulic retention time of sewage and the concentration of microorganisms in pollutants, and a pollutant degradation formula is constructed.

[0090] Where: c is the pollutant concentration, t is the hydraulic retention time of the pollutant, c0 is the influent pollutant concentration, c i is the effluent pollutant concentration, is the microbial concentration, and k is the reaction constant.

[0091] Since the reaction constant and the microbial concentration are fixed values, the product of the two is a fixed value μ.

[0092] The degradation formula is

[0093] The actual calculation shows that the hydraulic retention time is 12.86h. The influent COD concentration c0 = 80.4mg / L, c i = 60.6mg / L into the calculation, we get μ = 0.025h -1 , from which we can conclude that c i =c0·e -0.025t .

[0094] 2) In view of the problem of low treatment efficiency of the biofilter, the stacked packing structure of the original process is transformed into a composite multi-level standardized box assembly structure. The packing boxes are stacked on a horizontally slidable stainless steel bracket. Each group has 5 layers with the same layer height. From top to bottom, they are the ecological blanket layer 2041, the porous medium cotton layer 2042, the volcanic rock layer 2043, the ceramsite layer 2044, and the modified biological material layer 2045. After the transformation, the water flow cross-section of the biofilter is smaller, the water flow cross-section is smaller, and the water flow is distributed from top to bottom. It will not cause large overflow of some filter materials due to deformation of the filter basket, and some filter materials will not have overflow problems. The filter components can flow evenly. The biological blanket and porous medium cotton have good water permeability, can filter particulate matter in sewage, and are easy to clean regularly; volcanic rock, ceramsite and modified biological materials all have the characteristics of large porosity and large specific surface area, and good adsorption performance. The microorganisms in the vertical direction of the biofilter show a certain distribution pattern and stratified aggregation phenomenon due to the changes in dissolved oxygen and pollutant concentrations, forming a rich microbial community and enhancing the treatment efficiency. All levels of filler frames are equipped with diversion equipment to avoid the formation of concentrated water points and improve the filter material treatment efficiency.

[0095] 3)Formula:

[0096] The degradation of pollutants in sewage in the biofilter shows a certain relationship with the hydraulic retention time of sewage and the concentration of microorganisms in pollutants, and a pollutant degradation formula is constructed.

[0097] Where: c is the pollutant concentration, t is the hydraulic retention time of the pollutant, c0 is the influent pollutant concentration, c i is the effluent pollutant concentration, is the microbial concentration, and k is the reaction constant.

[0098] Since the reaction constant and the microbial concentration are fixed values, the product of the two is a fixed value μ.

[0099] The degradation formula is

[0100] The actual calculation shows that the hydraulic retention time is 14h. The influent COD concentration c0 = 60.6mg / L, c i = 35.2mg / L into the calculation, we get μ = 0.03h -1 , from which we can conclude that: c i =c0·e -0.03t .

[0101] 3) In order to solve the problem of poor phosphorus removal effect of the process, the partition wall in the original intermediate pool was transformed into a contact oxidation pool and a high-efficiency clarification pool, and an artificial wetland was rebuilt. Nano-aeration membrane equipment was installed at the bottom of the contact oxidation pool, and lightweight suspended fillers were installed in the middle to improve the aerobic treatment effect. A reaction hood was set in the high-efficiency clarification pool, and phosphorus removal agents were dripped into the reaction hood through the dosing system. Honeycomb inclined tubes were installed outside the reaction hood to intercept suspended matter in the water, thereby achieving phosphorus removal and clarification of the water. The channels and pipelines of the artificial wetland were rebuilt, new slow-release phosphorus removal fillers were laid, and plants with developed root systems were replaced to enhance the wetland's ability to adsorb nitrogen and phosphorus elements. 4. Process flow after transformation

[0102] like Figure 2 As shown, a water treatment system 2000 coupled with an anoxic biological filter and an artificial wetland includes, in order of water flow direction: an inlet pipe network 2010, a collection tank 2020, a regulating / anoxic tank 2030, a biological filter 2040, a contact oxidation tank 2050, a high-efficiency clarification tank 2060, an artificial wetland 2070, an outlet pipe network 2080, and a return system 2090.

[0103] The water inlet pipe network 2010 is used to collect sewage and transfer the sewage to the collection tank 2020.

[0104] A coarse and fine grid 2023 is provided in the middle of the water collection tank 2020, dividing the water collection tank 2020 into two parts, the water inlet pipe network 2010 is connected with the left part of the water collection tank 2020, and a gravity mud and water separation device 2022 is provided on the left part of the water collection tank 2020 (the separated sludge is regularly removed by the gravity mud and water separation device 2022 during operation and maintenance, thereby avoiding sludge accumulation and affecting normal functions); a first lifting pump 2021 is provided on the right part of the water collection tank 2020; the sewage in the water collection tank 2020 is transported to the regulating / anoxic tank 2030 by the first lifting pump 2021; the first lifting pump 2021 is used to ensure the low water level operation of the water collection tank and realize the water volume regulation function.

[0105] The regulating / anoxic tank 2030 is provided with a second lifting pump 2031; the sewage of the regulating / anoxic tank 2030 is transported to the biological filter water distribution facility 2040 through the fifth pipeline by the second lifting pump 2031; a floating suspended solid carbon source 2032 ("solid carbon source deep denitrification and water purification technology", solid carbon sources are arranged in the regulating / anoxic tank by floating suspension) is provided in the regulating / anoxic tank 2030, which provides a carrier for microorganisms while realizing slow-release supplement of carbon source, avoiding the problem of excessive or insufficient addition of carbon source.

[0106] At the same time, high and low water level gauges are set in the regulating / anoxic tank 2030 to adjust the output water volume and realize automatic adjustment of the operating liquid level: when it is higher than the high liquid level, it is in the forced discharge mode, with large flow and small reflux ratio; when it is between the high and low liquid levels, it is in the storage mode, with normal flow and moderate reflux ratio; when it is lower than the low liquid level, it is in the circulation mode, with complete reflux. The regulating / anoxic tank is set with a suitable minimum water level to ensure the hydraulic retention time.

[0107] The biofilter 2040 adopts a composite filler multi-level filling to further construct a rich biological community, and arranges the filling levels according to the characteristics of different biological phases to enhance the treatment efficiency. That is, the biofilter 2040 adopts a composite multi-level standardized box assembly structure, and the filler box is stacked on a horizontally slidable stainless steel bracket. Each group has 5 layers with the same layer height, and from top to bottom, they are an ecological blanket layer, a porous medium cotton layer, a volcanic rock layer, a ceramsite layer, and a modified biological material layer. The biological blanket layer and the porous medium cotton layer have good water permeability, can filter particulate matter in sewage, and are convenient for regular cleaning; the volcanic rock layer, the ceramsite layer, and the modified biological material layer all have the characteristics of large porosity and large specific surface area, and have good adsorption performance. The microorganisms in the vertical direction of the biofilter are subject to changes in dissolved oxygen and pollutant concentrations, showing a certain distribution pattern and stratified aggregation phenomenon, forming a rich microbial community and enhancing the treatment efficiency. Each level of the filler frame is provided with a diversion device to avoid the formation of a concentrated water point and improve the filter material treatment efficiency.

[0108] like Fig.12 It can be seen that the water distribution facilities of the biological filter are composed of a balancing water tank 2141 and a tooth weir water distribution trough 2142, wherein the balancing water tank has automatic backwashing and liquid level control functions to ensure uniform water distribution in the biological filter.

[0109] The balancing water tank 2141 has two main functions: (1) filtering impurities with a particle size greater than 3 mm in the water inlet of the anoxic pool to avoid clogging of the filter material; (2) regulating the liquid level in the balancing water tank to ensure the stability of the water level in the water distribution tank.

[0110] Operation principle of the balancing water tank: the regulating / anoxic tank normally takes in water, and the water is discharged to the rear end of the balancing water tank 2141 after being filtered by the front-end filter 21413, and flows into the tooth weir water distribution trough 2142 through the outlet pipe; in order to ensure the stability of the water level in the tooth weir water distribution trough, the regulating / anoxic tank inlet pump (i.e., the second lifting pump 2031) is controlled by the liquid level sensor 21411 and the liquid level control valve 21412 in the balancing water tank to always ensure that the water level in the balancing water tank is higher than the outlet pipe; according to the actual operation data, backwashing is performed at regular intervals, and the backwashing flushing valve adopts a PLC or PAC control system. The backwashing clean water comes from the rear end to contact the regulating / anoxic tank, and the flushing sewage is discharged into the anoxic tank.

[0111] The biofilter 2040 is provided with a third boost pump 2046 ; the third boost pump 2046 is connected to the reflux system 2090 .

[0112] The contact oxidation pond 2050 is used as a supplement and regulation link for the aerobic treatment capacity of the biological filter, and an internal circulation system is set between the two. A micro-nano aeration membrane 2051 is provided at the bottom of the contact oxidation pond, and a light suspended filler 2052 is provided in the middle. Through the bottom micro-aeration method, a higher pollutant removal capacity is achieved with lower energy consumption.

[0113] The high-efficiency clarifier 2060 has good sedimentation performance. The phosphorus removal device 2061 is added to add phosphorus removal agents to remove phosphorus while clarifying the water body, which significantly improves the SS content index of the effluent. The high-efficiency clarifier 2060 is provided with a honeycomb inclined tube 2061, and the honeycomb inclined tube sedimentation is used to achieve rapid sedimentation and separation of suspended matter.

[0114] The bottom of the artificial wetland 2070 is paved with a new type of slow-release phosphorus removal filler, and plants such as evergreen iris, canna, and pennywort are planted. The absorption effect of the plant roots in the artificial wetland and the adsorption effect of the new type of slow-release phosphorus removal filler can both improve the phosphorus removal effect.

[0115] The reflux system 2090 includes: a guide valve, a first pipeline, a second pipeline, a third pipeline, and a fourth pipeline; the first pipeline, the second pipeline, the third pipeline, and the fourth pipeline are all connected to the guide valve; the first pipeline is connected to the regulating / anoxic tank 2030; the second pipeline is connected to the second booster pump 2031, the third pipeline is connected to the third booster pump 2046, and the fourth pipeline is connected to the contact oxidation tank 2050; through the reflux system 2090, the flow can be adjusted back to the regulating / anoxic tank 2030.

[0116] 5. Monitoring results

[0117] After the project was completed, the average effluent concentrations of pH, COD, NH3-N, TN, TP and SS were 7.8, 21, 3.3, 10.70, 0.55 and 7.8 mg / L respectively. The monitoring data showed that the average effluent quality of the modified site was significantly improved compared with that before the modification. The improvement of COD, NH3-N, TN, TP and SS was 64%, 79%, 62%, 74% and 48% respectively. The removal effects of ammonia nitrogen, total nitrogen and total phosphorus were significant, which verified the nitrogen and phosphorus removal effect of the modified process. Figure 3 .

[0118] 6. Operation effect analysis

[0119] In order to analyze the operation effect of each treatment structure, the pH, COD, NH3-N, TN, TP, and SS values ​​of the effluent water quality at six points including the collection tank, regulation / anoxic tank, biological filter / aeration tank, contact oxidation tank, high-efficiency clarification tank, and outlet of the treatment station were tested for 5 consecutive days.

[0120] 6.1 pH value

[0121] The pH values ​​of each treatment structure are as follows: Figure 4 As shown, the pH value is in the range of 7.1 to 7.6, meeting the Class I B discharge standard.

[0122] The pH value increased slightly in the regulating / anoxic pond and artificial wetland. Since the regulating / anoxic pond and artificial wetland are in anoxic environment, denitrifying bacteria undergo denitrification reaction, reducing nitrate nitrogen (such as nitrate and nitrite) to nitrogen gas and producing hydroxide ions (OH - ), resulting in an increase in the pH value of the water.

[0123] The pH value decreased slightly in the biofilter and contact oxidation tank, which may be due to the production of certain acidic substances by microorganisms decomposing organic matter in an aerobic environment. The pH change in the high-efficiency clarifier is estimated to be related to the addition of phosphorus removal agents. The fillers in the artificial wetland are mainly artificial synthetic fillers, which are slightly alkaline, so the pH value of the effluent is stable.

[0124] 6.2COD Removal

[0125] The COD removal effect of each treatment structure is as follows Figure 5 As shown. The COD inlet concentration ranges from 71-89 mg / L (average is about 80.4 mg / L), the effluent COD concentration ranges from 20-26 mg / L (average is 23.6 mg / L), the removal rate is 64.8%-77.0%, average is 70.6%, meeting the Class B discharge standard (≤60 mg / L). The COD inlet concentration is lower than the design value of 300 mg / L because:

[0126] (1) After the farmers' sewage is treated in the septic tank, the concentration of the septic tank overflow sewage is low (less than 100 mg / L);

[0127] (2) The rainwater pipe network in the service area is not well constructed, and there is a problem of mixed connection between rainwater and sewage;

[0128] (3) The groundwater level in Shanghai is relatively high, and there is a problem of groundwater infiltration into the sewage pipe network. The monthly effluent water quality monitoring data for one consecutive year all met the design effluent standards, which fully demonstrated that the modified process has a strong adaptability to low influent COD concentration.

[0129] The COD concentration changes in the three treatment units, namely the collection tank, regulating / anoxic tank and biological filter, are the most significant. After the sewage enters the regulating / anoxic tank, the backflow has a certain dilution effect on the COD. At the same time, the denitrifying bacteria use the nitrate and nitrite in the reflux liquid as electron acceptors and use COD as a carbon source and electron donor to carry out denitrification reaction, thereby achieving the treatment of COD.

[0130] Figure 5 It shows that the average COD removal rate of the biological filter is the largest, reaching 42%, which is mainly based on the good ventilation and water distribution effect between the filter media layers. The biological filter is fully reoxygenated during the uniform water distribution and water drop process, allowing a large number of microorganisms to grow on the surface and inside the filler. At the same time, the filter media intercepts solid suspended particles, proteins, enzymes and other macromolecular organic matter in the sewage, which increases the contact time between microorganisms and organic matter, and improves the utilization rate of organic matter by the biofilm attached to the filler.

[0131] 6.3 Removal of NH3-N

[0132] The removal effect of each treatment structure on NH3-N is as follows Figure 6 As shown. The NH3-N inlet concentration ranges from 16.7 to 21.1 mg / L (average is about 18.8 mg / L), the effluent NH3-N concentration ranges from 1.8 to 3.1 mg / L (average is 2.5 mg / L), the removal rate is 82.8% to 89.7%, with an average of 86.7%, meeting the Class I B discharge standard (≤15 mg / L). In the regulating / anoxic tank, ammonia bacteria ammonify other forms of nitrogen in the water and convert them into ammonia nitrogen, so that the ammonia nitrogen concentration in the regulating / anoxic tank remains at a high concentration, with an average concentration of 16.6 mg / L. Figure 6 As shown in the figure, the treatment structures with higher NH3-N removal rates are the regulating / anoxic tank and the contact oxidation tank. Due to the presence of a complete nitrification-denitrification denitrification microbial system in the middle and lower part of the biofilter, the biofilm structure in the filter is stable, and ammonia nitrogen in the water is removed while effectively degrading organic matter. The average removal rate of ammonia nitrogen in the biofilter is 51.9%. The contact oxidation tank is the treatment unit with the highest ammonia nitrogen removal efficiency, with an average removal rate of 54.9%. The contact oxidation tank increases the dissolved oxygen content in the water through micro-nano aeration and oxygenation. A higher concentration of dissolved oxygen is conducive to the removal of ammonia nitrogen in the water by nitrifying bacteria.

[0133] 6.4TN Removal

[0134] The removal effect of each treatment structure on TN is as follows Figure 7As shown. The TN inlet concentration ranges from 28.9 to 34.5 mg / L (average is about 32.1 mg / L), the effluent TN concentration ranges from 9.6 to 10.9 mg / L (average is 10.35 mg / L), the removal rate is 66.6% to 55.5%, and the average is 68.7%, meeting the Class I B discharge standard (≤25 mg / L). The treatment process mainly relies on denitrification to achieve TN removal. Figure 7 As shown in the figure, the highest TN removal efficiency is in the regulating / anoxic tank, with an average removal rate of 44.5%, followed by the biofilter and artificial wetland, with average removal rates of 24.7% and 19.6%, respectively. The COD / TN ratio in the influent concentration is about 2.5, which belongs to low carbon-nitrogen ratio sewage. The lack of carbon source in the sewage leads to low denitrification efficiency. Setting a solid carbon source in the regulating / anoxic tank not only solves the low carbon problem of sewage and realizes the slow release and supplement of carbon source, but also provides a carrier for microorganisms to form biofilms, improves the utilization efficiency of carbon source, and further strengthens denitrification by denitrification. Based on the concentration gradient of matrix and dissolved oxygen on the biofilm on the surface of the biofilter filler, the dissolved oxygen concentration forms an aerobic, anoxic, and anaerobic microenvironment on the biofilm, providing a place for microbial denitrification and realizing TN removal. Artificial wetlands remove nitrogen through the absorption of nitrogen in sewage by plant roots and denitrification in the anaerobic zone near the filler layer.

[0135] 6.5 Removal of TP

[0136] The removal effect of each treatment structure on TP is as follows Figure 8 As shown. The TP inlet concentration ranges from 1.9 to 2.4 mg / L (average is about 2.2 mg / L), the effluent TP concentration ranges from 0.4 to 0.6 mg / L (average is 0.46 mg / L), the removal rate is 71.4%-81.8%, and the average is 78.9%, meeting the Class I B discharge standard (≤2 mg / L). After the sewage is treated by the conditioning / anoxic tank, biological filter, and contact oxidation tank, the total phosphorus concentration has hardly changed. Due to the lack of alternation between aerobic and anaerobic environments in the biological filter, the activated sludge content is low, and the biological phosphorus removal effect is poor. In the treatment of domestic sewage, other combined processes need to be combined to meet the phosphorus removal needs. Therefore, adding phosphorus removal agents to the high-efficiency clarifier to form insoluble precipitates with phosphates in the sewage can make up for the lack of biological phosphorus removal and achieve stable phosphorus removal. The absorption effect of plant roots in artificial wetlands and the adsorption effect of new slow-release phosphorus removal fillers can both improve the phosphorus removal effect.

[0137] 6.6 Removal of SS

[0138] The SS removal effect of each treatment unit is as follows: Fig. 9As shown. The SS inlet concentration ranges from 45-75 mg / L (average is about 62.4 mg / L), the effluent SS concentration ranges from 5-8 mg / L (average is 7 mg / L), the removal rate is 87.5%-90.0%, and the average is 88.8%, meeting the Class I B emission standard (≤20 mg / L). The efficient removal of SS mainly relies on the filler filtration in the biofilter and the sedimentation in the high-efficiency clarifier. The filler in the biofilter has a large specific surface area and porosity, which can effectively intercept and adsorb suspended particles in sewage; at the same time, the microbial film on the surface of the filler can secrete substances such as mucus to further enhance the adsorption effect. In the high-efficiency clarifier, the rapid sedimentation and separation of suspended matter is achieved through honeycomb inclined tube sedimentation. Fig. 9 As shown in Figure 1, aeration in the contact oxidation pond caused a significant increase in SS concentration. When sewage overflowed from the high-efficiency clarifier to the artificial wetland, the SS concentration in the effluent of the artificial wetland might increase slightly due to the flushing effect of the water flow.

[0139] The above embodiments are preferred implementation modes of the present invention and are only used to facilitate the description of the present invention. They are not intended to limit the present invention in any form. Any person with ordinary knowledge in the relevant technical field, if they do not depart from the scope of the technical features of the present invention, can make equivalent embodiments by partial changes or modifications to the technical contents disclosed in the present invention, and they still fall within the scope of the technical features of the present invention without departing from the technical features of the present invention.

Claims

1. A water treatment system combining anoxic biofilter and artificial wetland, characterized in that: According to the direction of water flow, it includes an inlet pipe network, a water collection tank, a regulating / anoxic tank, a biological filter, a contact oxidation tank, a high-efficiency clarification tank, an artificial wetland, and an outlet pipe network that are connected in sequence; The water inlet pipe network is used to collect sewage and transfer the sewage to the water collection tank; The water collection tank is used to remove silt and regulate water volume; The regulating / anoxic tank is provided with a floating body to suspend a solid carbon source, which provides a carrier for microorganisms and realizes a slow-release supplement of the carbon source; the regulating / anoxic tank is used to denitrify sewage and regulate water volume; The biofilter uses a composite filler to be filled in multiple levels, which are, from top to bottom, a biological blanket layer, a porous medium cotton layer, a volcanic rock layer, a ceramsite layer, and a modified biological material layer; the biological blanket layer and the porous medium cotton layer are both used to filter particulate matter in sewage; the volcanic rock layer, the ceramsite layer, and the modified biological material layer are all used to absorb impurities in sewage; The high-efficiency clarification tank is provided with a phosphorus removal device and a honeycomb inclined tube, and the high-efficiency clarification tank is used for phosphorus removal and water clarification.

2. The water treatment system according to claim 1, characterized in that: A coarse and fine grid is arranged in the middle of the water collection pool to divide the water collection pool into two parts, left and right. The water inlet pipe network is connected to the left part of the water collection tank and a gravity mud-water separation device is provided on the left part of the water collection tank; A first lifting pump is arranged at the right part of the water collection tank, and the sewage in the water collection tank is transported to the regulating / anoxic tank through the first lifting pump.

3. The water treatment system according to claim 1, characterized in that: The regulating / anoxic tank is provided with a second lifting pump; the sewage in the regulating / anoxic tank is transported to the biological filter tank through the fifth pipeline by the second lifting pump.

4. The water treatment system according to claim 3, characterized in that: The biofilter is provided with a third boost pump; the third boost pump is connected to the reflux system.

5. The water treatment system according to claim 4, characterized in that: The water treatment system also includes: the reflux system, including: a guide valve, a first pipeline, a second pipeline, a third pipeline, and a fourth pipeline; the first pipeline, the second pipeline, the third pipeline, and the fourth pipeline are all connected to the guide valve; the first pipeline is connected to the regulation / anoxic tank; the second pipeline is connected to the second boost pump, the third pipeline is connected to the third boost pump, and the fourth pipeline is connected to the contact oxidation tank; through the reflux system, the flow rate of the solution coming in from the second boost pump and the third boost pump into the first pipeline or the fourth pipeline can be controlled.

6. The water treatment system according to claim 4 or 5, characterized in that: The water distribution facility of the biological filter pool is composed of a balancing water tank and a tooth weir water distribution tank, wherein the balancing water tank is newly equipped with automatic backwashing and liquid level control functions to ensure uniform water distribution in the biological filter pool; The balancing water tank can filter impurities with a particle size greater than 3mm in the water inlet of the anoxic pool to avoid clogging of the filter material; at the same time, the balancing water tank can also regulate the liquid level in the balancing water tank to ensure the stability of the water level in the water distribution tank; The regulating / anoxic tank normally inflows water, and after being filtered through the front-end filter, the water is discharged to the rear end of the balancing water tank, and flows into the tooth weir water trough through the outlet pipe. To ensure the stability of the water level in the tooth weir water trough, the second lifting pump is controlled by the liquid level sensor and the liquid level control valve in the balancing water tank to always ensure that the water level in the balancing water tank is higher than the outlet pipe. According to the actual operation data, backwashing is performed at regular intervals, and the backwashing valve adopts a PLC or PAC control system. The backwashing clean water comes from the rear-end contact oxidation tank, and the flushing wastewater is discharged into the anoxic tank.

7. The water treatment system according to claim 4, characterized in that: The contact oxidation pond has a micro-nano aeration membrane at the bottom and a light suspended filler in the middle.

8. The water treatment system according to claim 1, characterized in that: The following steps are used to treat the water: S100, sewage is collected through the water inlet network and flows into the water collection tank; S200, the water collection pool enters the regulating / anoxic pool through the first lifting pump, and the solid carbon source is suspended by the floating body in the pool, providing a carrier for the microorganisms while realizing the slow release supplement of the carbon source, thereby strengthening the denitrification reaction to remove total nitrogen and then transporting it to the biological filter and contact oxidation pool; S300 removes COD and ammonia nitrogen through carbon oxidation reaction and nitrification reaction. The effluent flows into the high-efficiency clarification tank by gravity. After most of the total phosphorus and SS are removed by coagulation and sedimentation, the overflow enters the artificial wetland. After comprehensive treatment by plants, microorganisms and fillers, the pollutants are purified and finally transported to the effluent network.

9. The water treatment system according to claim 1, characterized in that: A wall is provided in the regulating / anoxic tank, and a row of 10cm×10cm square holes are provided on the wall to connect the tank body; the wall is used to divide the functional area of ​​the regulating / anaerobic tank to improve the anaerobic environment; the agitator pump and the suspended solid carbon source are divided into different areas by the partition wall. The influent of the regulating / anoxic tank contains a certain amount of dissolved oxygen, and the stirring effect of the agitator pump can reduce the dissolved oxygen in the water. The sewage overflows to the solid carbon source side through the square holes on the wall. The anoxic environment of the sewage overflowing to the solid carbon source is more stable, which is conducive to the denitrification reaction; Lay a gravel layer on the surface of the conditioning / anoxic tank; A variable frequency water pump is installed at the bottom of the regulating / anoxic pool, and high and low water level gauges are installed on the pool body; the variable frequency water pump adjusts the output water volume through the measured signal of the level gauge to achieve water level control of the regulating / anoxic pool, ensuring that the anoxic pool maintains a stable anoxic environment.

10. The water treatment system according to claim 8, characterized in that: The pollutant concentrations of the inlet and outlet of the regulating / anoxic tank satisfy the following relationship: c i =c0·e -0.025t ; The pollutant concentrations of the inlet and outlet of the biofilter satisfy the following relationship: c i =c0·e -0.03t ; Among them, c i is the effluent pollutant concentration, c0 is the influent pollutant concentration, and t is the hydraulic retention time of the pollutant.

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