CN115818862A - A cold water mariculture tail water treatment system - Google Patents

Abstract

The invention relates to the technical field of water treatment, in particular to a cold water area mariculture tail water treatment system, which comprises a pretreatment unit, a biochemical treatment unit, a membrane treatment unit, a disinfection treatment unit and a sludge treatment unit which are sequentially connected; the pretreatment unit comprises a coarse grating, a fine grating, a grit chamber and a membrane grating which are connected in sequence; the biochemical treatment unit comprises an anaerobic zone, an anoxic zone, an aerobic zone and a post-anoxic zone which are sequentially connected; the membrane treatment unit is a membrane bioreactor. Compared with the prior art, the cold water area mariculture tail water treatment system provided by the invention adopts a highly enriched enhanced microorganism treatment process with a denitrification function, and ensures that the total nitrogen of effluent is stably below the standard limit on the premise of sufficient front-end nitration reaction and sufficient organic carbon source.

Description

A cold water mariculture tail water treatment system

technical field

The invention relates to the technical field of water treatment, in particular to a tail water treatment system for mariculture in cold water areas.

Background technique

Mariculture tail water treatment technology at home and abroad is in the ascendant. There are many studies with different levels. Up to now, there is no large-scale successful case in China. According to incomplete statistics, the first domestic 2000m3/d mariculture tail water treatment plant built in Hainan has been put into operation recently. And the test run is good.

However, the annual average seawater temperature in Hainan is 23-25°C, and the average seawater temperature in my country's Bohai Rim is 9-11°C. After research and small tests, Hainan's mariculture tail water treatment plan is not suitable for the Bohai Rim Tail water treatment of mariculture in cold water areas.

Mariculture tail water contains relatively high pollution concentrations of various nitrogen, phosphorus, COD, antibiotics and heavy metal substances, which has led to a sharp deterioration of the water quality of the aquaculture water around the farmers, and the excellent aquatic aquaculture environment of sensitive fish has also been artificially destroyed. In the process of removing various pollutants, the removal of total nitrogen is the most difficult.

In view of this, the present invention is proposed.

Contents of the invention

The purpose of the present invention is to provide a tail water treatment system for mariculture in cold water areas, which solves the problem of total nitrogen removal, ensures that the indicators of various pollutants in the effluent are lower than the standard limit, and solves various pollution in the tail water of mariculture in cold water areas The problem of material removal.

To achieve the above object, the present invention provides the following technical solutions:

A tail water treatment system for mariculture in cold water areas, comprising sequentially connecting a pretreatment unit, a biochemical treatment unit, a membrane treatment unit, a disinfection treatment unit and a sludge treatment unit;

The pretreatment unit includes a coarse grid, a fine grid, a grit chamber and a membrane grid connected in sequence;

The biochemical treatment unit includes an anaerobic zone, anoxic zone, aerobic zone, and post-anoxic zone connected in sequence;

The membrane treatment unit is a membrane bioreactor.

Preferably, in the pretreatment unit, the coarse grid is a rotary coarse grid, and the fine grid and the membrane grid are both internal inflow screen type fine grids.

Preferably, in the biochemical treatment unit, a sludge return pipe is provided in the anoxic zone to communicate with the water inlet pipe of the anaerobic zone; a return pipe is provided in the aerobic zone to communicate with the outlet pipe of the anaerobic zone.

Preferably, in the membrane treatment unit, a sludge return pipe is set in the membrane treatment unit to communicate with the outlet pipe of the anoxic zone.

Preferably, in the membrane treatment unit, the membranes in the membrane bioreactor are hollow fiber membranes made of PVDF.

Preferably, in the biochemical treatment unit, a secondary sedimentation tank is connected after the post anoxic zone.

Preferably, chemicals for chemical phosphorus removal need to be put into the grit chamber and the secondary sedimentation tank.

Preferably, the agent for chemical phosphorus removal is basic aluminum chloride PAC.

Preferably, the disinfection treatment unit is an ultraviolet disinfection device.

Preferably, the sludge treatment unit is a screw dehydrator.

Compared with the prior art, the present invention provides a tail water treatment system for mariculture in cold water areas, which adopts a high-enrichment and enhanced microbial treatment process with denitrification function, and under the premise that the front-end nitrification reaction is sufficient and the organic carbon source is sufficient , to ensure that the total nitrogen in the effluent is stable below the standard limit.

In order to make the above-mentioned objects, features and advantages of the present invention more comprehensible, preferred embodiments will be described in detail below together with the accompanying drawings.

Description of drawings

In order to illustrate the technical solutions of the embodiments of the present invention more clearly, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and thus It should be regarded as a limitation on the scope, and those skilled in the art can also obtain other related drawings based on these drawings without creative work.

Fig. 1 is a structural diagram of a tail water treatment system for mariculture in cold water areas provided by an embodiment of the present invention.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. The components of the embodiments of the invention generally described and illustrated in the figures herein may be arranged and designed in a variety of different configurations. Accordingly, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative efforts belong to the protection scope of the present invention.

In this plan, the treated raw water is the mariculture tail water discharged from a marine high-tech industrial demonstration park in the Bohai Bay area.

Specifically, it includes the polluted seawater discharged from the aquatic product factory breeding demonstration area, aquatic product nursery base, outdoor recirculating aquaculture demonstration area, aquatic product processing area, leisure fishery resort area, aquatic product trading area, warehousing and logistics area, etc.

After treatment, the effluent reaches the quasi-IV category (TN≤10) of the "Environmental Quality Standards for Surface Water" (GB3838-2002). The main water quality indicators of its influent and effluent water are shown in Table 1:

Table 1 Influent and effluent water quality index table

serial number index Influent water quality Water quality 1 CODcr(mg/L) ≤350 ≤30 2 5-day biochemical oxygen demand BOD5(mg/L) ≤160 ≤6 3 Suspended solids (SS) (mg/L) ≤120 ≤5 4 Ammonia nitrogen (mg/L) ≤47 ≤1.5 5 TN (mg/L) ≤70 ≤1.5 6 TP (mg/L) ≤5 ≤0.3

As shown in FIG. 1 , an embodiment of the present invention provides a tail water treatment system for mariculture in cold water areas, including a pretreatment unit, a biochemical treatment unit, a membrane treatment unit, a disinfection treatment unit and a sludge treatment unit connected in sequence.

The pretreatment unit includes a coarse grid, a fine grid, a grit chamber and a membrane grid connected in sequence.

In the pretreatment unit, according to the characteristics of raw water quality, it is determined that the main task of the pretreatment unit is to use physical separation methods to remove floating and suspended solids in sewage and improve the biodegradability of sewage. The main facilities and structures include grilles, sand settling pool etc.

The grille is used to remove larger suspended matter, floating matter, fibrous matter and solid particle matter in sewage to ensure the normal operation of subsequent treatment units and water pumps, reduce the processing load of subsequent treatment units, and prevent blockage of sludge discharge pipes. According to the grid gap, it is divided into coarse grid, medium grid and fine grid. Generally, there are two thick and thin grids. The coarse grid removes large-scale floating and suspended solids, and the fine grid is used to further remove smaller Suspended particles, floating matter, and grille intercepted matter are shipped out of the factory.

The membrane grid is used to further remove fine hair and fiber substances in the water, and is the key pretreatment device of the MBR membrane method. There are many types of membrane grilles, which are divided into sieve type and mesh type according to the type of screen mesh, and divided into drum type, stepped type, and internal flow type according to the structural form.

In this scheme, the coarse grid adopts the rotary coarse grid, the fine grid adopts the fine grid of internal flow mesh plate, and the membrane grid adopts the fine grid of internal flow mesh plate.

Since the sewage entering the sewage treatment plant contains a certain amount of inorganic silt, in order to protect the normal and stable operation of the subsequent biological treatment section, ensure and improve the effective utilization of the biological reaction tank, and make the process have greater operational flexibility, etc., It is necessary to set up a grit chamber.

Grit chambers account for a small proportion in the investment and land occupation of sewage treatment plants, but their role cannot be ignored. If the sand removal effect of the grit chamber is not good, if there is no ideal sand removal effect, a large amount of sand particles will enter the subsequent treatment units, which will bring many hidden dangers to the normal operation of the sewage plant: in engineering design, the sand particles with d≥0.2mm are usually used Removal efficiency is used to measure the efficiency of the grit chamber system. The most commonly used types of grit chambers are aerated grit chambers and cyclone grit chambers.

The earliest domestic application is the aeration grit chamber, which is widely used in different types of sewage and sewage treatment plants of different specifications. The main advantages of this type of grit chamber are:

1) The removal rate of fine sand particles is relatively high, and the design can be changed according to the water inlet conditions and water outlet requirements to meet different requirements.

2) Stable operation, strong adaptability to the impact load of flow and sand volume.

3) The separation effect of organic matter is high, and the organic matter carried is less.

4) It has a better effect of removing grease and scum, which is especially effective for systems without separate primary sedimentation tanks.

There are two main disadvantages of this grit chamber:

1) It occupies a large area.

2) The aeration process may increase the dissolved oxygen value of the sewage, and may consume part of the rapidly degraded organic matter in the sewage, which will adversely affect the subsequent work of the anaerobic biological pool. Cyclone grit chamber

For the scheme, an aerated grit chamber is used, because the shape of the pond can ensure a stable sand removal effect, and can give full play to its good sand removal effect and the effect of oil skimming and scum removal, so as to ensure the smoothness of the subsequent process It is beneficial to the operation management of the whole plant and the overall improvement of effluent water quality.

The biochemical treatment unit includes an anaerobic zone, anoxic zone, aerobic zone, and post-anoxic zone connected in sequence;

According to the requirements of influent water quality and effluent water quality, the biochemical treatment unit should adopt biological nitrogen and phosphorus removal treatment process. The biological nitrogen and phosphorus removal process adopts the A/A/O process.

The A/A/O process is the anaerobic-anoxic-aerobic activated sludge process, that is, the phosphorus and nitrogen removal reaction is completed through the alternating environment of anaerobic and aerobic, anoxic and aerobic. In this process, the anaerobic tank is used for biological phosphorus removal, and the anoxic tank is used for biological nitrogen removal. The carbon source in the raw water enters the anaerobic tank first, and the phosphorus-accumulating bacteria preferentially use the easily biodegradable substances in the sewage to become the dominant bacteria. species, creating conditions for phosphorus removal, the sewage then enters the anoxic tank, and the denitrifying bacteria use other possible carbon sources to reduce the nitrate nitrogen that flows back to the anoxic tank into nitrogen gas to achieve the purpose of denitrification.

Its characteristic is that the functions of the three stages of anaerobic, anoxic and aerobic are clear, and the boundaries are clear. According to the water inlet conditions and water outlet requirements, the time-space ratio and operating conditions of the three stages can be artificially created and controlled. As long as the carbon source is sufficient, it can be used according to Need to achieve a relatively high phosphorus and nitrogen removal effect. The post-anoxic zone can further enhance the phosphorus and nitrogen removal effects.

The membrane treatment unit is a membrane bioreactor.

Membrane-Bioreactor (MBR for short) is the product of the organic combination of membrane separation technology and sewage biological treatment technology. It is generally considered to be a sewage treatment technology with stable performance, good effect and great development potential. The feature of this technology is to replace the sludge-water gravity sedimentation separation process in the traditional activated sludge treatment process with the ultra-microfiltration membrane separation process. Due to the membrane separation, it can maintain a high biophase concentration and excellent water effluent effect. It can effectively remove pollutants such as organic matter and ammonia nitrogen in water.

The membrane treatment unit adopts the submerged MBR, which is characterized by immersing the special membrane module in the mixed solution, and discharges the water (through the microporous membrane) out of the biochemical reaction tank under the suction of the water pump or the promotion of the water level difference , Microorganisms, cells and other particles are intercepted in the biochemical reaction pool. The membranes are hollow fiber membranes made of PVDF. Each membrane pool is provided with water inlet, outlet gate and emptying pipe. The effluent of the membrane pool is designed according to the suction flow, and each membrane pool is equipped with a permeate pump. The outlet connecting pipe is connected to the outlet jelly pipe of the membrane pool, and the outlet jelly pipe is connected with the membrane pool pump. The permeable liquid pump of the membrane pool is controlled by frequency conversion.

The MBR process mainly has the following characteristics:

(1) The effluent water quality is good and can efficiently separate solids and liquids. The effluent water quality is good and stable, and the suspended solids and turbidity are close to zero. Compared with the traditional biological treatment process, its biological phase-activated sludge concentration has increased by 2-3 times, so the biochemical efficiency is greatly improved, and the effluent water quality is good, which can ensure that the effluent water quality is better than the first-class A standard.

(2) The floor area is small, about 1/2-1/3 of the area occupied by the traditional process. The concentration of microorganisms in the reactor is high, which can reach more than 10,000 mg/liter, which greatly increases the volume load (up to 2-5KgCOD/m ³ .d), reducing the volume of the biochemical pool. One treatment structure of the membrane bioreactor replaces multiple treatment structures such as primary sedimentation, aeration, secondary sedimentation, coagulation, and filtration in the traditional sewage treatment process, which greatly reduces the occupation of land.

(3) Strong impact resistance and stable operation Due to the high sludge concentration and rich biological phase, and there is no problem of sludge loss, it is not affected by factors such as sludge expansion, so it has strong impact resistance and stable operation. Especially for sewage treatment plants containing more industrial sewage, it has significant advantages.

(4) Rich biological phase: The high-efficiency interception effect of the membrane makes the microorganisms completely trapped in the reactor, which can enrich and reproduce the microorganisms with a long generation cycle and the microorganisms that are not easy to form bacterial micelles, and can be in the entire biological phase. Bioaccumulation and co-metabolism are formed to form a relatively complete microbial chain, which greatly improves the treatment efficiency and system stability, which is relatively rare in traditional biochemical processes.

(4) Rich biological phase: The high-efficiency interception effect of the membrane makes the microorganisms completely trapped in the reactor, which can enrich and reproduce the microorganisms with a long generation cycle and the microorganisms that are not easy to form bacterial micelles, and can be in the entire biological phase. Bioaccumulation and co-metabolism are formed to form a relatively complete microbial chain, which greatly improves the treatment efficiency and system stability, which is relatively rare in traditional biochemical processes. (5) Design, automatic control Due to the modular characteristics of membrane bioreactor technology, it is easy to expand, and it can cope with the increase of water treatment capacity by adding necessary modules. The process equipment is centralized, all of which are controlled by computer automation, and the operation and management are simple.

(5) Design, automatic control Due to the modular characteristics of membrane bioreactor technology, it is easy to expand, and it can cope with the increase of water treatment capacity by adding necessary modules. The process equipment is centralized, all of which are controlled by computer automation, and the operation and management are simple.

(6) The effect of 1+1>2 Due to the use of membrane separation technology for solid-liquid separation, the biological concentration and population number in the bioreactor are greatly increased, the biological activity is improved, and the biodegradation efficiency is greatly improved. Therefore, the membrane bioreactor is not simply a superposition of biological treatment and membrane separation technology, but has the effect of 1+1>2.

Membrane separation system working procedure:

The submerged membrane block is placed in a separate membrane tank. The membrane block is submerged in the mixed liquid, and under the negative pressure generated by the osmosis (water outlet) pump, the water passes through the membrane to complete the filtration process. The membrane tank replaces the function of the separation of suspended solids and liquid in the secondary sedimentation tank and the advanced treatment of filtration.

Aeration plays an important role in the operation of membrane equipment. Large bubble aeration is used at the bottom of the membrane block to generate turbulence to scour the surface of the hollow fibers and cause particles to fall off the surface of the membrane. Another method is to combine air and water at the bottom of the membrane monolith to produce the same effect. Each of these measures reduces the frequency of chemical cleaning of the membrane block.

While the membrane tank is aerated, the membrane tank can be used as the second aerobic tank to completely complete the oxidation of BOD5 and the nitrification of ammonia nitrogen to ensure that the effluent reaches the standard.

The microfiltration membrane is also a barrier for biological flocs, suspended solids, and pathogens. It can obtain clear effluent, the SS concentration is close to zero, and the separation effect does not depend on the sedimentation performance of the sludge.

Each membrane tank has an outlet pump. The effluent is sent to the next treatment process through the effluent pump. Through the operation of the pump, a negative pressure can be generated at the head of the membrane block connection. The treated water flows through the porous fiber microfiltration membrane and enters the suction pump.

The concentrated mixed solution produced by the membrane tank is continuously returned to the previous biological tank through the mixed solution to maintain the sludge concentration in the biochemical tank and reduce the accumulation of biological sludge in the membrane tank.

As a part of the remaining sludge, the mixed liquid is transferred to the sludge thickening and dewatering machine room for dehydration.

After a period of use, due to the clogging of organic and inorganic substances, the permeability of the membrane will decrease, which will lead to an increase in membrane filtration resistance, thereby increasing the transmembrane pressure difference (TMP). The following measures will control membrane fouling, so as to achieve long-term and stable operation of the system:

(1) Positive air sweep

Positive air sweeping means that when the system is filtering, the supporting blower of the system is turned on at the same time, the corresponding control valve is opened, and the blower aerates to sweep the surface of the membrane filament to prevent a large amount of deposition of particulate matter on the membrane surface.

(2) intermittent suction

Intermittent suction means that the osmotic suction pump of the membrane runs continuously for a certain period of time (such as 7 minutes) and stops running for a certain period of time (such as 1 minute). Under the disturbance of the gas-water two-phase turbulent flow, the membrane filaments vibrate with sufficient intensity, which will make a small amount of particles deposited on the surface of the membrane filaments detach from the membrane surface during filtration, and remove the pollutants on the membrane surface.

(3) Maintenance cleaning

Dosing chemical backwashing is usually performed once a week, which is called maintenance cleaning (the frequency of cleaning is also related to the nature of sewage, and may be performed once every 10-30 days). When the system is running, the automatic backwashing process is performed separately for each membrane tank without operator input. The development of high-strength, high-chemical-resistance PVDF membranes has made this frequent maintenance-in-line cleaning possible. The agents used for maintenance cleaning are common acids and sodium hypochlorite, which are prepared into low-concentration solutions before use. The automatic control of PLC makes the cleaning operation extremely simple, and the online maintenance cleaning (Clean-In-Place, CIP) process can be designed as a fully automatic operation without manual intervention. The cleaning time for maintenance cleaning shall not exceed 2 hours each time, and normal production shall not be affected.

(4) Recovery cleaning

Even with these maintenance measures, TMP will slowly reach a peak or cutoff value. Once the cut-off value is reached, each membrane block needs to be removed from the tank and chemically cleaned to remove fouling substances and restore permeability. This procedure, called recovery cleaning, is usually performed every 12 to 24 months, depending on the clog. Once the membrane modules need to be cleaned, the individual membrane modules are removed and soaked in the cleaning tank. According to the type of scale, different chemical solvents can be used for cleaning, sodium hypochlorite is used for organic scale, and weak acid is used for inorganic scale. After soaking for a period of time, after the filtration performance of the membrane is restored, the membrane module is reinstalled back to the production line. Since the removal of a single membrane module has little impact on the operation of the system in the short term, the restoration of chemical cleaning will not affect production.

The main features are:

(1) The effluent water quality of the MBR process is good, and it can efficiently separate solids and liquids. The effluent water quality is good and stable, and the suspended solids and turbidity are close to zero. Compared with the traditional biological treatment process, its biological phase-activated sludge concentration has increased. 2-3 times, so the biochemical efficiency is greatly improved, and the quality of the effluent is good, which can ensure that the quality of the effluent is better than the first-class A standard, and the effluent can be used in a wider range of uses. The process for reclaimed water treatment is also relatively simple. In addition, due to the strong modularity of the membrane separation technology, it is easy to expand, and the expansion is very convenient. It can easily improve the treatment capacity by adding microfiltration membrane treatment units in the biological treatment structure and increasing the sludge concentration.

(2) Generally speaking, in the early stage of the application of MBR technology, traditional MBR technology projects require large investment, large power consumption, and high operating costs. However, with the development of MBR technology and the expansion of engineering applications in recent years, as far as we know, there are new MBR technologies at home and abroad that can make engineering investment and operating costs comparable to traditional processes. Its characteristics are as follows: a. The use of double-layer membrane modules makes the packing density of the membrane modules higher and saves land occupation; b. The use of pulse superimposed membrane purge technology further reduces the energy consumption of membrane purge; c. The multi-phase combination forms such as multi-point water inlet and multi-point reflux make the biochemical treatment more efficient, and the energy consumption is lower than that of traditional MBR operation.

(3) For MBR technology, the membrane used for sewage treatment is mainly a solid-phase asymmetric membrane made of organic polymer materials. The structural type of the membrane used in this project is a hollow fiber membrane. Hollow fiber type: the outer diameter is generally 40-250 μm, and the inner diameter is 25-42 μm. The advantages are: high compressive strength, not easy to deform. The combination of the membrane module and the bioreactor is a separate membrane-bioreactor, that is, the membrane module and the bioreactor are set separately, and the mixed liquid in the bioreactor is pressurized by the circulating pump and then pumped to the filter end of the membrane module. Under the action of pressure, the liquid in the mixed liquid permeates the membrane and becomes system treated water; the solids and macromolecular substances are intercepted by the membrane and flow back to the bioreactor with the concentrated liquid. The separated membrane-bioreactor is characterized by stable and reliable operation, easy membrane cleaning, replacement and addition; and the membrane flux is generally large. However, under general conditions, in order to reduce the deposition of pollutants on the membrane surface and prolong the cleaning cycle of the membrane, it is necessary to use a circulating pump to provide a higher cross-flow velocity on the membrane surface and a large amount of water circulation. In the membrane pool, the components are directly put into the reactor without a pressure vessel to form a submerged membrane-bioreactor. Generally, it is an external pressure membrane module. Its advantages are: high packing density; relatively low cost; long service life; nylon hollow fiber membrane with stable physical and chemical properties and low water permeability can be used; the membrane has good pressure resistance and does not need support materials.

Preferably, in the biochemical treatment unit, a sludge return pipe is provided in the anoxic zone to communicate with the water inlet pipe of the anaerobic zone; a return pipe is provided in the aerobic zone to communicate with the outlet pipe of the anaerobic zone.

In addition, in the embodiment of the present invention, the membrane treatment unit is provided with a sludge return pipe to communicate with the outlet pipe of the anoxic zone. In the biochemical treatment unit, a secondary sedimentation tank is also connected after the post anoxic zone. Chemical dephosphorization agents need to be put into the grit chamber and the secondary sedimentation tank. The agent for chemical phosphorus removal is basic aluminum chloride PAC. The disinfection treatment unit is an ultraviolet disinfection device. The sludge treatment unit is a screw dehydrator.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" etc. The indicated orientation or positional relationship is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship that is usually placed when the product of the invention is used, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying References to devices or elements must have a particular orientation, be constructed, and operate in a particular orientation and therefore should not be construed as limiting the invention. In addition, the terms "first", "second", "third", etc. are only used for distinguishing descriptions, and should not be construed as indicating or implying relative importance.

In addition, the terms "horizontal", "vertical", "overhanging" and the like do not mean that the components are absolutely horizontal or overhanging, but may be slightly inclined. For example, "horizontal" only means that its direction is more horizontal than "vertical", and it does not mean that the structure must be completely horizontal, but can be slightly inclined.

In the description of the present invention, it should also be noted that, unless otherwise clearly specified and limited, the terms "installation", "installation", "connection" and "connection" should be understood in a broad sense, for example, it may be a fixed connection, It can also be 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 intermediary, and it can be the internal communication of two components. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention in specific situations.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention. It should be noted that like numerals and letters denote similar items in the following figures, therefore, once an item is defined in one figure, it does not require further definition and explanation in subsequent figures.

Claims (10)

1. A tail water treatment system for mariculture in cold water areas, characterized in that it comprises sequentially connecting a pretreatment unit, a biochemical treatment unit, a membrane treatment unit, a disinfection treatment unit and a sludge treatment unit; The pretreatment unit includes a coarse grid, a fine grid, a grit chamber and a membrane grid connected in sequence; The biochemical treatment unit includes an anaerobic zone, anoxic zone, aerobic zone, and post-anoxic zone connected in sequence; The membrane treatment unit is a membrane bioreactor. 2. A cold water area mariculture tail water treatment system according to claim 1, characterized in that, in the pretreatment unit, the coarse grid is a rotary coarse grid, and the fine grid and The membrane grids are fine grids of the internal flow screen type. 3. The tail water treatment system of a kind of cold water area mariculture according to claim 2, characterized in that, in the biochemical treatment unit, the anoxic zone is provided with a sludge return pipe connected to the water inlet pipe of the anaerobic zone The aerobic zone is provided with a return pipe to communicate with the outlet pipe of the anaerobic zone. 4. A tail water treatment system for mariculture in cold water areas according to claim 3, characterized in that, in the membrane treatment unit, the membrane treatment unit is provided with a sludge return pipe to communicate with the outlet pipe in the anoxic zone. 5. A tail water treatment system for marine aquaculture in cold water areas according to claim 4, characterized in that, in the membrane treatment unit, the membranes in the membrane bioreactor are hollow fiber membranes made of PVDF. 6 . The tail water treatment system for mariculture in cold water areas according to claim 5 , wherein, in the biochemical treatment unit, a secondary sedimentation tank is connected after the post anoxic zone. 7 . 7 . The tail water treatment system for mariculture in cold water areas according to claim 6 , wherein chemicals for chemical phosphorus removal need to be put into the grit chamber and the secondary sedimentation tank. 8 . 8 . A tail water treatment system for marine aquaculture in cold water areas according to claim 7 , wherein the agent for chemical phosphorus removal is basic aluminum chloride PAC. 9 . The tail water treatment system for mariculture in cold water areas according to claim 8 , wherein the disinfection treatment unit is an ultraviolet disinfection device. 10 . 10 . The tail water treatment system for mariculture in cold water areas according to claim 9 , wherein the sludge treatment unit is a screw stacking dehydrator. 11 .

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