Oil-containing crack sewage treatment system and method

Abstract

The invention provides an oil-containing crack sewage treatment system and method, and belongs to the technical field of sewage treatment. The treatment system comprises a physical pretreatment unit, a biochemical treatment unit, an effluent monitoring pool and an artificial wetland which are communicated in sequence, the physical pretreatment unit comprises an adjusting tank, a coalescence oil removal separator and a coagulative precipitation tank which are connected in sequence; the biochemical treatment unit comprises an anoxic / aerobic tank, an MBR (Membrane Bioreactor) membrane tank and an activated carbon adsorber which are communicated in sequence. According to the method, a coalescence oil removal efficient pretreatment technology is used for replacing a traditional flocculation air flotation chemical treatment method, so that low medicine consumption, low material consumption, low operation cost and hazardous waste reduction are realized; according to the invention, an innovative treatment process of physical pretreatment, biochemical treatment and artificial wetland coupling is constructed for the first time; the treatment indexes are innovated, and the oil-containing crack sewage treatment depth is improved from the current urban first-grade B standard to the earth surface III-grade standard.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage treatment, and in particular relates to a system and method for treating oil-containing fractured sewage. Background Art

[0002] The underground water-sealed cavern is formed by artificial excavation in underground rocks. Its sealing is achieved by groundwater infiltration into the cavern. The underground cavern must be built below the stable groundwater level to ensure that the groundwater pressure around the cavern is greater than the pressure of the storage medium in the cavern. After the reserve crude oil is injected into the cavern, there will be a certain oil and water pressure difference around the cavern. Therefore, at any same level, the underground hydrostatic pressure is greater than the oil pressure in the cavern. In this way, the oil in the cavern is stored in this closed pressure field. Under the action of water pressure, the fissure water in the rock mass continuously flows into the cavern and gathers at the bottom of the cave to form a water cushion layer. Since oil is lighter than water and oil and water do not mix, the reserve crude oil always floats on the water cushion layer at the bottom of the cavern. The liquid level is monitored by an oil-water interface detector. When it reaches a certain height, the oil-containing fissure water is discharged to the ground facilities by a submersible pump installed in the cavern for sewage treatment and discharged after meeting the standards.

[0003] At present, the treatment of fissure water abroad is to first enter the fissure water regulating tank to homogenize the water volume and water quality, then pre-treat it through the inclined plate and the method of adding medicine and flotation, and then discharge it into the production pool for reuse after biological aeration and filtration. With the deterioration of the environment, the traditional "three highs" fissure water treatment technology of high medicine consumption, high energy consumption and high emission has begun to develop in the direction of green and low consumption.

[0004] The development of domestic water-sealed cavern technology lags behind the international level. Currently, there are only a few national strategic oil depots under construction, such as Huangdao in Shandong, Jinzhou in Liaoning, Huizhou in Guangdong, and Zhanjiang. In addition, there are still weak basic theoretical applications and practical engineering experience, including the treatment technology of cavern fissure water.

[0005] Taking a certain operating cavern fissure water treatment process as an example, the fissure water is first collected in the regulating tank, and then enters the oil separator after homogenization and adjustment, where floating oil, dispersed oil and most emulsified oil are floated and removed. The deoiled fissure water enters the flotation section, where tiny bubbles combined with chemicals adhere to oil droplets and suspended solids, and then enters the biochemical pool to degrade organic pollutants such as COD and ammonia nitrogen. The effluent is discharged into the discharge pool after sedimentation in the sedimentation tank, and finally discharged to the municipal sewage treatment plant. However, there are many problems in the current operating process. The grease separator fails due to the low oil content at the front end; the excessive amount of medicine added in the flotation tank causes the sedimentation tank at the back end to turn green; the biological pool is still in a state of suspension due to the lack of a deep understanding of the water quality components and the lack of a suitable strain; and after multi-stage treatment, the oil content of the effluent has not been significantly reduced, and the decline in other indicators is small, failing to meet the original design of the emission indicators.

[0006] Therefore, it is urgent to develop a new technology for treating oily fissure wastewater to achieve the goal of low carbon and economic and technological level improvement and support national strategic energy reserves. Summary of the invention

[0007] The purpose of the present invention is to solve the problems existing in the above-mentioned prior art, and to provide a system and method for treating oil-containing fissure sewage, which for the first time constructs an innovative treatment process of coupling physical pretreatment + biochemical treatment + artificial wetland, and the effluent meets the surface Class III standard.

[0008] The present invention is achieved through the following technical solutions:

[0009] The first aspect of the present invention provides an oil-containing fissure sewage treatment system, comprising a physical pretreatment unit, a biochemical treatment unit, an effluent monitoring pool and an artificial wetland that are connected in sequence;

[0010] The physical pretreatment unit includes a regulating tank, a coalescence oil removal separator, and a coagulation sedimentation tank connected in sequence;

[0011] The biochemical treatment unit comprises an anoxic / aerobic tank, an MBR membrane tank and an activated carbon adsorber which are connected in sequence.

[0012] A further improvement of the present invention is:

[0013] The coalescence oil removal separator comprises a separator body, the upper part of the side wall of the separator body is provided with a water inlet, the top is provided with an oil phase outlet, the bottom is provided with a water outlet, and the separator body is provided with a distributor and a coalescence filtration module from top to bottom in sequence, and the distributor is connected to the water inlet.

[0014] A further improvement of the present invention is:

[0015] The coalescence filtration module comprises a hydrophilic / hydrophobic particle coalescence module and a hydrophilic / hydrophobic fiber coalescence module arranged in sequence from top to bottom;

[0016] The hydrophilic / hydrophobic particle agglomeration module is formed by stacking hydrophilic / hydrophobic particles in bulk, and each layer of particles is stacked by mixing hydrophilic and oleophobic particles and hydrophobic and oleophilic particles, and the particle size increases gradually from top to bottom;

[0017] The hydrophilic / hydrophobic fiber aggregation module is woven from hydrophilic fibers and hydrophobic fibers in an X-shaped and / or Ω-shaped weaving manner.

[0018] A further improvement of the present invention is:

[0019] The materials of hydrophilic and oleophobic particles include but are not limited to glass, ceramics, and quartz sand inorganic hydrophilic materials; the materials of hydrophobic and oleophilic particles include but are not limited to polytetrafluoroethylene and polypropylene polymer oleophilic materials.

[0020] A further improvement of the present invention is:

[0021] The material of the hydrophilic fiber includes but is not limited to 316, 316L, and titanium wire metal hydrophilic fiber materials; the material of the hydrophobic fiber includes but is not limited to polypropylene and polytetrafluoroethylene polymer oleophilic fiber materials.

[0022] A further improvement of the present invention is:

[0023] The coagulation sedimentation tank includes a coagulation tank and a vertical flow sedimentation tank connected to each other; and / or,

[0024] The coagulation tank is an integrated three-tank coagulation reaction tank; and / or,

[0025] The sludge collecting hopper at the bottom of the vertical flow sedimentation tank is connected to the sludge thickening tank.

[0026] A further improvement of the present invention is:

[0027] The MBR membrane pool includes a water distribution tank and two parallel membrane pools respectively connected to the water distribution tank, wherein the two membrane pools operate independently, and the effluent from the anoxic pool enters the water distribution tank for water distribution and then enters the membrane pool; and / or,

[0028] The bottom of the membrane tank is connected to the sludge thickening tank; and / or,

[0029] The pore size of the hollow fiber membrane assembly in the membrane pool is 0.02-0.05 μm.

[0030] A further improvement of the present invention is:

[0031] The artificial wetland adopts three-level horizontal subsurface flow wetland beds, the upper wetland bed is connected to the lower wetland bed through a water distribution channel, and the water inlet side and the water outlet side of each wetland bed are provided with a partition wall for diversion.

[0032] A further improvement of the present invention is:

[0033] The horizontal subsurface flow wetland bed is provided with a clay layer, an anti-seepage layer, and a bottom drainage layer from bottom to top. The middle filter layer is made of crushed stone with a particle size of The soil filter layer is made of gravel and the particle size is It is paved with sandy soil filler and emergent plants are planted on the top.

[0034] The second aspect of the present invention provides a method for treating oily fissure wastewater, wherein the above-mentioned treatment system is used to treat the oily fissure wastewater, comprising the following steps:

[0035] Physical pretreatment: The oily fractured sewage enters the regulating tank for water quality and quantity adjustment, and then enters the coalescence oil removal separator for coalescence oil removal treatment. After coalescence oil removal treatment, the effluent enters the coagulation sedimentation tank for coagulation treatment. After coagulation treatment, the effluent enters the biochemical treatment unit, and the bottom sludge enters the sludge thickening tank for sludge treatment;

[0036] Biochemical treatment: The sewage after physical pretreatment enters the anoxic / aerobic tank and MBR membrane tank for treatment in turn. The effluent is pumped to the activated carbon adsorber for activated carbon adsorption treatment to further remove organic matter and petroleum pollutants in the sewage. The effluent enters the effluent monitoring tank. After monitoring, the effluent from the effluent monitoring tank meets the effluent index requirements and is discharged into the artificial wetland. If the effluent index requirements are not met, the effluent is pumped back to the regulating tank by the backwash water pump for further treatment.

[0037] Artificial wetland: The sewage in the effluent monitoring pool is tested and meets the effluent standards, then it is treated in three-level horizontal subsurface flow wetland beds before being discharged.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] The present invention replaces the traditional chemical treatment method of flocculation and flotation with a physical high-efficiency pretreatment technology, thereby achieving low drug consumption, material consumption, operating costs, and reduction of hazardous waste;

[0040] The treatment process of the present invention is innovative. It breaks through the traditional three-set treatment mode of oil-containing fractured wastewater and constructs an innovative treatment process of physical pretreatment + biochemical treatment + artificial wetland coupling for the first time.

[0041] The present invention has innovative treatment indicators, which raises the treatment depth of oil-containing fissure sewage from the current urban Class I B standard to the surface Class III standard. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 The present invention provides a flow chart of an oil-containing fissure sewage treatment system;

[0043] Figure 2 It is a schematic diagram of the structure of a coalescing and oil removing separator;

[0044] Figure 3 is a schematic diagram of the structure of the coalescence filtration module;

[0045] In the figure, 1. separator body, 2. water inlet, 3. oil phase outlet, 4. water outlet, 5. distributor, 6. coalescence filtration module, 6-1. hydrophilic / hydrophobic particle coalescence module, 6-2. hydrophilic / hydrophobic fiber coalescence module. DETAILED DESCRIPTION

[0046] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0047] In view of the lack of understanding of the quality of oily fissure wastewater in my country and the immature wastewater treatment technology, a comprehensive investigation and analysis of the quality of oily fissure wastewater was carried out to break the "three highs" restrictions of high chemical consumption, high energy consumption and high emissions in traditional pretreatment technology, and realize low-carbon deep treatment in the pretreatment section. The innovation is concentrated in the following three aspects:

[0048] Innovative treatment concept, using physical high-efficiency pretreatment technology to replace the traditional chemical treatment method of flocculation and flotation, achieving low drug consumption, material consumption, operating costs, and reduction of hazardous waste;

[0049] The treatment process is innovative. For oily fracture wastewater, the traditional three-set treatment mode of oil refinery wastewater is broken through. For the first time, an innovative treatment process combining physical pretreatment + biochemical treatment + artificial wetland is constructed.

[0050] Innovation in treatment indicators will raise the treatment depth of oil-bearing fissure sewage in caverns from the current urban Class I B standard to the surface Class III standard.

[0051] Based on the investigation of the water quality of oil-containing fissure water and the results of laboratory experiments, the present invention proposes a system for treating oil-containing fissure wastewater. The specific embodiments are as follows:

[0052] [Example 1]

[0053] like Figure 1 As shown, the oil-containing fissure sewage treatment system of the present invention includes a physical pretreatment unit, a biochemical treatment unit, an effluent monitoring pool and an artificial wetland which are connected in sequence.

[0054] The present invention adopts coalescence oil removal to remove petroleum pollutants in sewage without adding other agents, thereby achieving low drug consumption, material consumption, reduced operating costs, and reduced hazardous waste; at the same time, a biochemical treatment unit + an activated carbon adsorber are used to remove petroleum pollutants to the maximum extent, and the tail water is then treated through a three-level artificial wetland, thereby ensuring that the effluent meets the surface water Class III index of the "Surface Water Environmental Quality Standard" (GB 3838-2002). After being treated by the treatment system of the present invention, the petroleum in the effluent is ≤0.05 mg / L.

[0055] [Example 2]

[0056] The physical pretreatment unit comprises a regulating tank, a coalescence oil removal separator, and a coagulation sedimentation tank which are connected in sequence. After being treated by the physical pretreatment unit, the sulfide content in the effluent is controlled to be ≤10mg / L, and the petroleum content is controlled to be ≤5mg / L.

[0057] like Figure 2As shown, the coalescence oil removal separator includes a separator body 1, a water inlet 2 is provided on the upper part of the side wall of the separator body 1, an oil phase outlet 3 is provided on the top, and a water outlet 4 is provided on the bottom. A distributor 5 and a coalescence filtration module 6 are provided in the separator body 1 from top to bottom, and the distributor 5 is connected to the water inlet 2.

[0058] like Figure 3 As shown, the coalescence filtration module 6 includes a hydrophilic / hydrophobic particle coalescence module 6-1 and a hydrophilic / hydrophobic fiber coalescence module 6-1 which are arranged in sequence from top to bottom. The hydrophilic / hydrophobic particle coalescence module 6-1 is formed by stacking hydrophilic / hydrophobic particles in bulk, and each layer of particles is formed by a mixture of hydrophilic and oleophobic particles and hydrophobic and oleophilic particles. The particle size increases gradually from top to bottom, and the particle size is 0.1mm-3mm; the material of the hydrophilic and oleophobic particles includes but is not limited to inorganic hydrophilic materials such as glass, ceramics, and quartz sand; the material of the hydrophobic and oleophilic particles includes but is not limited to polymer oleophilic materials such as polytetrafluoroethylene and polypropylene.

[0059] The core of the oil removal technology of hydrophilic / hydrophobic particle agglomeration module 6-1 lies in agglomeration. The principle is that the oily wastewater passes through the hydrophilic and hydrophobic particles and the hydrophilic and hydrophobic particles from top to bottom. The emulsified oil droplets with smaller particle size in the water collide, adhere, aggregate, fuse, grow on the surface of a single hydrophilic and hydrophobic particle and between multiple hydrophilic and hydrophobic particles, and are finally released. Specifically:

[0060] (1) Collision: The collision of dispersed phase oil droplets with lipophilic particles, and the oil droplets rebound after colliding with hydrophilic particles; (2) Adhesion: The oil droplets wet and adhere to the surface of lipophilic particles, and the oil droplets rebound from the hydrophilic particles and adhere to the lipophilic particles; (3) Polymembranes: Multiple oil droplets adhere to the surface of lipophilic particles and gradually merge to form a closed oil film to wrap the particles; (4) Bridge flow: Particles with oil films are connected to form "oil bridges" in the bed. Under the action of large flow forces, oil droplets move from top to bottom along the oil bridges, accompanied by mutual collision, aggregation, fusion, growth, and self-renewal of the oil bridges; (5) Release: At the end of the bed, the grown oil droplets break away from the oil bridges and flow with the water phase in a free state until they are collected. In addition, hydrophilic and lipophobic particles can ensure that the bed is not completely covered by the oil film, improve fluidity, and ensure separation efficiency.

[0061] In addition to the oil removal function, the hydrophilic / hydrophobic particle agglomeration module 6-1 also relies on the adsorption and interception effect of the bed layer to separate viscous suspended matter and solid particle impurities, thereby achieving the purpose of desuspension.

[0062] The hydrophilic / hydrophobic fiber aggregation module 6-2 is woven with hydrophilic fibers and hydrophobic fibers in an X-type and / or Ω-type weaving manner, wherein the materials of the hydrophilic fibers include but are not limited to metal hydrophilic fiber materials such as 316, 316L, and titanium wire, and the materials of the hydrophobic fibers include but are not limited to polymer oleophilic fiber materials such as polypropylene and polytetrafluoroethylene.

[0063] The separation principle of the hydrophilic / hydrophobic fiber coalescence module 6-2 is the rapid coalescence and separation induced by the precursor oil film of finely dispersed oil on the surface of the hydrophilic fiber, and the polar force demulsification of the emulsified oil at the intersection of the hydrophilic / hydrophobic fibers. The basic separation process is: there is a cross-scale precursor oil film in the oil-water-solid three-phase interface area where the hydrophilic fiber contacts the oil droplets, which spreads rapidly under the molecular gravity on the surface of the hydrophilic fiber, bridges with adjacent oil droplets to shorten the coalescence time, and the finely dispersed oil droplets in the water collide and capture on the hydrophilic fiber - rapid coalescence and growth, and as the large oil droplets detach, the fiber surface is renewed, and this cycle is repeated to achieve rapid coalescence and separation of the oil droplets; when the oil-water emulsion droplets flow through the intersection of the hydrophilic / hydrophobic fibers, due to the difference in polar force of the droplets on the hydrophilic and hydrophilic fibers, the oil droplets migrate to the hydrophilic fibers and the water droplets migrate to the hydrophilic fibers, thereby achieving efficient physical demulsification of the emulsion.

[0064] The oily fractured wastewater is separated by a coalescence oil removal separator. No chemical agents need to be added during the oil removal and separation process, and there is no secondary pollution. After treatment by the coalescence oil removal separator, the petroleum content in the effluent is ≤5mg / L, while the existing commonly used flotation oil removal technology has a petroleum content of ≤20mg / L in the effluent.

[0065] [Example 3]

[0066] The coagulation sedimentation tank includes a connected coagulation tank and a vertical flow sedimentation tank.

[0067] The coagulation tank includes a coagulation zone and a flocculation zone, and alkali solution, coagulant, and polymer flocculant PAM are added in sequence, wherein the alkali solution is sodium hydroxide solution and the coagulant is PAC; the pH value in the coagulation tank is controlled at about 8.5, for example, when the pH value is 8-9, the coagulation effect is better.

[0068] Preferably, the coagulation tank is an integrated three-tank coagulation reaction tank.

[0069] In the coagulation reaction tank, the pH value is controlled at about 8.5 under the action of the agitator, and larger flocs are formed under the bridging effect of PAM; then the overflow enters the vertical flow sedimentation tank, and under the action of gravity, the sediment in the sewage settles to the bottom sludge collecting hopper, and the supernatant overflows from the outlet trough to the biochemical treatment unit. The sludge collecting hopper at the bottom of the vertical flow sedimentation tank is connected to the sludge thickening tank, and the sediment in the sludge collecting hopper at the bottom of the sedimentation tank is discharged to the sludge thickening tank by the sludge pump for sludge treatment.

[0070] The coagulation sedimentation tank mainly removes sulfide. After coagulation sedimentation treatment, the sulfide in the effluent is ≤10mg / L.

[0071] [Example 4]

[0072] The biochemical treatment unit includes anoxic / aerobic tanks and MBR membrane tanks which are connected in sequence. A submersible mixer is installed in the anoxic tank for mixing to prevent sludge sedimentation. An aeration fan is installed outside the aerobic tank and an aeration system is set inside.

[0073] The activated sludge method is preferred for the anoxic tank, and the DO of the anoxic environment is controlled to be ≤0.5mg / L, so that the denitrifying bacteria can quickly convert the nitrate nitrogen and nitrite nitrogen returned from the end of the aerobic tank into N2 escape, completing the biological denitrification. The reaction equation is:

[0074] Denitrification reaction: 5C (organic matter) + 4NO3 - +2H2O=2N2↑+5CO2↑+4OH -

[0075] 3C(organic matter)+4NO2 - +2H2O=2N 2 ↑+3CO2↑+4OH -

[0076] The effluent from the anoxic pool flows into the aerobic pool by gravity. The anoxic pool is preferably a contact oxidation pool. The aeration fan provides air to control the dissolved oxygen DO in the anoxic pool to be ≥2.0 mg / L. Aerobic microorganisms decompose organic matter into CO2 and H2O and oxidize ammonia nitrogen into nitrate nitrogen, which is a nitrification reaction. The reaction equation is:

[0077] Decomposition of organic matter: (C5H7O2N)n+5nO2=5nCO2↑+2nH2O+nNH3

[0078] Nitration reaction: NH4 + +1.87O2+1.982HCO3 - =0.982NO3 - +1.044H2O+1.881H2CO3+0.021C5H7O2N

[0079] The contact oxidation tank is evenly distributed with curtain-type fiber fillers (products purchased directly from imported filler suppliers). The wire diameter of the filler is nanometer-level. Due to its special structure, it has a huge specific surface area, which is more than 8 times that of conventional fixed fillers, providing the best growth environment for the attachment of microorganisms, and the types of microorganisms are more abundant. The biofilm on the surface of the filler can form a food chain from bacteria-protozoa-metazoa, and the organic matter is removed more thoroughly, and the sludge production is less than that of the activated sludge treatment system. The biological sludge particles that fall off from the biofilm are larger, have a larger specific gravity, and have good sedimentation properties, and will not cause sludge expansion.

[0080] The MBR membrane pool includes a water distribution trough and two parallel membrane pools respectively connected to the water distribution trough. The two membrane pools can operate independently. The effluent from the anoxic pool enters the water distribution trough for distribution, and then enters the membrane pool for further treatment. Organic pollutants continue to be degraded in the membrane pool, and finally solid-liquid separation is achieved through filtration of membrane components.

[0081] The effluent is drawn out from the inside of the hollow fiber membrane assembly by negative pressure suction. Since the pore size of the hollow fiber membrane is 0.02-0.05μm, it can intercept suspended solids, colloids, petroleum, microorganisms and macromolecular organic pollutants, so that the mud-water mixture can be completely separated. On the one hand, high-quality effluent can be obtained, with SS≤1mg / L, COD≤40mg / L, and petroleum≤0.5mg / L, which reduces the load of the subsequent activated carbon adsorber and reduces the backwashing frequency; on the other hand, it effectively retains the dominant bacteria with a long generation cycle that decomposes difficult-to-degrade pollutants, prevents sludge loss, increases the sludge concentration of the biochemical system, and improves the removal rate.

[0082] The membrane is operated in an intermittent mode, i.e. water production-stop-water production. The membrane filtration water production system consists of membrane components, pipelines and mechanical equipment and can meet the water production flow requirements in any operation mode.

[0083] An aeration pipe is provided at the bottom of the hollow fiber membrane module, and turbulence is generated by the aeration method of air supply by a blower to scrub the outer surface of the hollow fiber membrane and reduce the fouling of the membrane.

[0084] A sludge return pipe is connected between the MBR membrane pool and the anoxic / aerobic pool. The sludge in the membrane pool is returned to the anoxic / aerobic pool to maintain the sludge concentration of the biochemical system while denitrifying the nitrate nitrogen in the return liquid, ultimately achieving the removal of total nitrogen.

[0085] The bottom of the membrane pool is connected to the sludge thickening tank for discharging excess sludge. Since the COD and suspended solids concentrations in the oily fissure sewage are very low, the biochemical treatment unit uses curtain fiber fillers with low sludge production and MBR membrane technology. The sludge yield coefficient is very low. Under normal circumstances, there is no need to continuously discharge excess sludge. Only a small amount of excess sludge needs to be intermittently discharged using a membrane pool sludge pump. The discharge interval needs to be determined based on the operating conditions.

[0086] [Example 6]

[0087] The biochemical treatment unit also includes an activated carbon adsorber connected to the MBR membrane pool. After the oily fractured sewage is treated by the MBR membrane pool, the effluent enters the activated carbon adsorber through a water pump. The activated carbon has a good adsorption and removal capacity and can simultaneously adsorb organic matter and petroleum pollutants in the sewage. After treatment by the activated carbon adsorber, the COD in the effluent is ≤30mg / L, and the petroleum is ≤0.1mg / L.

[0088] Activated carbon adsorption utilizes the characteristics of activated carbon, such as porosity, huge specific surface area, and large adsorption capacity, to make organic matter, petroleum, etc. adhere to the surface of activated carbon and be removed from sewage. Activated carbon adsorption includes three types: physical adsorption, chemical adsorption, and ion exchange. The adsorption process includes: liquid film diffusion, from liquid to the surface of adsorbent; pore diffusion, from the liquid phase in the pores of adsorbent to the center of adsorbent; surface adsorption reaction.

[0089] The effluent from the MBR membrane pool is pumped out by the membrane water production pump, and directly enters the activated carbon adsorber using the pressure of the water production pump, and the effluent flows to the effluent monitoring pool. The activated carbon adsorber is automatically backwashed at the set time, generally once every 2 weeks; it can also be automatically controlled by the differential pressure transmitter. Each backwashing time is about 8-12 minutes. The backwashing water comes from the effluent monitoring pool and is lifted by the backwashing water pump; the backwashing water is discharged into the collection pool of the sewage treatment plant. When the COD or petroleum content of the effluent from the activated carbon adsorber exceeds the standard, part or all of the activated carbon needs to be replaced.

[0090] The effluent monitoring pool is also connected to the regulating pool. After the effluent quality of the effluent monitoring pool is monitored and qualified, it will be discharged into the artificial wetland by gravity. If it is unqualified, it will be lifted by the backwash water pump and returned to the regulating pool.

[0091] [Example 7]

[0092] The artificial wetland adopts three-level horizontal subsurface flow wetland beds. The upper wetland bed is connected to the lower wetland bed through a water distribution channel, and each wetland bed is provided with a partition wall for diversion on the water inlet and outlet sides.

[0093] The horizontal subsurface flow wetland bed is composed of a clay layer (compacted), an anti-seepage layer of C30 concrete bottom plate, and a bottom drainage layer of The middle filter layer is made of crushed stone with a particle size of The soil filter layer is made of gravel and the particle size is It is paved with sandy soil filler, and emergent plants are planted on the top. The first-level horizontal subsurface wetland bed is planted with calamus, and the second-level and third-level horizontal subsurface wetland beds are planted with canna and windmill grass alternately.

[0094] [Example 8]

[0095] The present invention also provides a method for treating oily fissure wastewater, which uses the wastewater treatment system of Examples 1-7 to treat the oily fissure wastewater, and specifically comprises the following steps:

[0096] Physical pretreatment: The oily fractured sewage enters the regulating tank for water quality and quantity adjustment, and then enters the coalescence oil removal separator for coalescence oil removal treatment. After coalescence oil removal treatment, the effluent enters the coagulation sedimentation tank for coagulation treatment. After coagulation treatment, the effluent enters the biochemical treatment unit, and the bottom sludge enters the sludge thickening tank for sludge treatment;

[0097] Biochemical treatment: The sewage after physical pretreatment enters the anoxic / aerobic tank and MBR membrane tank for treatment in turn, where the DO in the anoxic tank is controlled to be ≤0.5mg / L, and the DO in the aerobic tank is controlled to be ≥2.0mg / L; the effluent is pumped to the activated carbon adsorber for activated carbon adsorption treatment to further remove organic matter and petroleum pollutants in the sewage, and the effluent enters the effluent monitoring tank. The effluent from the effluent monitoring tank is discharged into the artificial wetland after monitoring to meet the effluent standards. If it does not meet the effluent standards, it is lifted by the backwash water pump and returned to the regulating tank for further treatment;

[0098] Artificial wetland: The sewage in the effluent monitoring pool is tested and meets the effluent standards, then it is treated in three-level horizontal subsurface flow wetland beds before being discharged.

[0099] The sewage treatment method of the present invention adopts coalescence oil removal to remove petroleum pollutants in sewage without adding other agents, thereby achieving low drug consumption, material consumption, reduced operating costs, and reduced hazardous waste; at the same time, a biochemical treatment unit + an activated carbon adsorber are used to remove petroleum pollutants to the maximum extent, and the tail water is then treated through a three-level artificial wetland, thereby ensuring that the effluent meets the surface water Class III index of the "Surface Water Environmental Quality Standard" (GB 3838-2002). After being treated by the treatment system of the present invention, the petroleum in the effluent is ≤0.05 mg / L.

[0100] The treatment method of the present invention is used to treat oil-bearing fractured water in a certain place. The water quality of the inlet water, the water quality of the outlet water after treatment in each unit and the water quality of the outlet water of the entire system are shown in Table 1.

[0101] Table 1 Water quality of inlet and outlet water in each section

[0102]

[0103] As can be seen from Table 1, after being treated by the coalescence oil removal technology of the present invention, the oil content in the oily fissure sewage is reduced from 30mg / L of the influent water quality to 5mg / L, and no agent needs to be added during the coalescence oil removal process, which realizes low drug consumption, material consumption, operating cost, and hazardous waste reduction; after being treated by the treatment system of the present invention, the petroleum in the effluent of the oily fissure sewage is reduced to 0.05mg / L, with a removal rate of 99.8%, the suspended solids are reduced to 5mg / L, with a removal rate of 90%, CODr is reduced to 20mg / L, with a removal rate of 93.3%, BOD5 is reduced to 4mg / L, with a removal rate of 94.3%, ammonia nitrogen is reduced to 1mg / L, with a removal rate of 90%, total phosphorus is reduced to 0.2mg / L, sulfide is reduced to 0.2mg / L, and the removal rate is 99.75%. It can be seen that its treatment indicators are innovative, and the treatment depth of oily fissure sewage is increased from the current urban Class B standard to the surface Class III standard.

[0104] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0105] In the description of the present invention, unless otherwise specified, the terms "upper", "lower", "left", "right", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limitations on the present invention.

[0106] The above technical solution is only one implementation mode of the present invention. For those skilled in the art, it is easy to make various types of improvements or modifications based on the principles disclosed in the present invention, and it is not limited to the technical solution described in the above specific embodiments of the present invention. Therefore, the above description is only preferred and does not have a restrictive meaning.

Claims

1. A system for treating oily fissure wastewater, characterized in that: It includes a physical pretreatment unit, a biochemical treatment unit, an effluent monitoring pool and an artificial wetland that are connected in sequence; The physical pretreatment unit includes a regulating tank, a coalescence oil removal separator, and a coagulation sedimentation tank connected in sequence; The biochemical treatment unit comprises an anoxic / aerobic tank, an MBR membrane tank and an activated carbon adsorber which are connected in sequence.

2. The oily fissure wastewater treatment system according to claim 1, characterized in that: The coalescence oil removal separator comprises a separator body, the upper part of the side wall of the separator body is provided with a water inlet, the top is provided with an oil phase outlet, the bottom is provided with a water outlet, and the separator body is provided with a distributor and a coalescence filtration module from top to bottom in sequence, and the distributor is connected to the water inlet.

3. The oily fissure wastewater treatment system according to claim 2, characterized in that: The coalescence filtration module comprises a hydrophilic / hydrophobic particle coalescence module and a hydrophilic / hydrophobic fiber coalescence module arranged in sequence from top to bottom; The hydrophilic / hydrophobic particle agglomeration module is formed by stacking hydrophilic / hydrophobic particles in bulk, and each layer of particles is stacked by mixing hydrophilic and oleophobic particles and hydrophobic and oleophilic particles, and the particle size increases gradually from top to bottom; The hydrophilic / hydrophobic fiber aggregation module is woven from hydrophilic fibers and hydrophobic fibers in an X-shaped and / or Ω-shaped weaving manner.

4. The oily fissure wastewater treatment system according to claim 3, characterized in that: The materials of hydrophilic and oleophobic particles include but are not limited to glass, ceramics, and quartz sand inorganic hydrophilic materials; the materials of hydrophobic and oleophilic particles include but are not limited to polytetrafluoroethylene and polypropylene polymer oleophilic materials.

5. The oily fissure wastewater treatment system according to claim 3, characterized in that: The material of the hydrophilic fiber includes but is not limited to 316, 316L, and titanium wire metal hydrophilic fiber materials; the material of the hydrophobic fiber includes but is not limited to polypropylene and polytetrafluoroethylene polymer oleophilic fiber materials.

6. The oily fissure wastewater treatment system according to claim 1, characterized in that: The coagulation sedimentation tank includes a coagulation tank and a vertical flow sedimentation tank connected to each other; and / or, The coagulation tank is an integrated three-tank coagulation reaction tank; and / or, The sludge collecting hopper at the bottom of the vertical flow sedimentation tank is connected to the sludge thickening tank.

7. The oily fissure wastewater treatment system according to claim 1, characterized in that: The MBR membrane pool comprises a water distribution tank and two parallel membrane pools respectively connected to the water distribution tank, wherein the two membrane pools operate independently, and the effluent of the anoxic pool enters the water distribution tank for water distribution and then enters the membrane pool; and / or, The bottom of the membrane tank is connected to the sludge thickening tank; and / or, The pore size of the hollow fiber membrane assembly in the membrane pool is 0.02-0.05 μm.

8. The oily fissure wastewater treatment system according to claim 1, characterized in that: The artificial wetland adopts three-level horizontal subsurface flow wetland beds, the upper wetland bed is connected to the lower wetland bed through a water distribution channel, and the water inlet side and the water outlet side of each wetland bed are provided with a partition wall for diversion.

9. The oily fissure wastewater treatment system according to claim 8, characterized in that: The horizontal subsurface flow wetland bed is provided with a clay layer, an anti-seepage layer, a bottom drainage layer paved with crushed stone with a particle size of φ15mm, an intermediate filter layer paved with gravel with a particle size of φ10-φ12mm, a soil filter layer paved with sand filler with a particle size of φ4-φ8mm, and emergent plants are planted on the top.

10. A method for treating oily fissure wastewater, using the treatment system according to any one of claims 1 to 9 to treat oily fissure wastewater, comprising the following steps: Physical pretreatment: The oily fractured sewage enters the regulating tank for water quality and quantity adjustment, and then enters the coalescence oil removal separator for coalescence oil removal treatment. After coalescence oil removal treatment, the effluent enters the coagulation sedimentation tank for coagulation treatment. After coagulation treatment, the effluent enters the biochemical treatment unit, and the bottom sludge enters the sludge thickening tank for sludge treatment; Biochemical treatment: The sewage after physical pretreatment enters the anoxic / aerobic tank and MBR membrane tank for treatment in turn. The effluent is pumped to the activated carbon adsorber for activated carbon adsorption treatment to further remove organic matter and petroleum pollutants in the sewage. The effluent enters the effluent monitoring tank. After monitoring, the effluent from the effluent monitoring tank meets the effluent index requirements and is discharged into the artificial wetland. If the effluent index requirements are not met, the effluent is pumped back to the regulating tank by the backwash water pump for further treatment. Artificial wetland: The sewage in the effluent monitoring pool is tested and meets the effluent standards, then it is treated in three-level horizontal subsurface flow wetland beds before being discharged.

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