A SBR treatment method for marine aquaculture tail water

Abstract

The invention discloses a SBR treatment method for seawater aquaculture tail water, comprising the following steps: loading activated sludge into an SBR reactor; introducing simulated seawater aquaculture tail water into the reactor, anaerobic treatment for 5-7h, aeration treatment for 1-2h, precipitation, exporting the treated tail water, repeating the above anaerobic-aerobic process for many times, until the reactor runs for 70-80 days; introducing simulated seawater aquaculture tail water into the reactor, anaerobic precipitation treatment for 7-8h, exporting the treated tail water, repeating the above complete anaerobic process for many times, until the reactor runs for 120-125 days; introducing seawater aquaculture tail water into the reactor, anaerobic precipitation treatment for 7-8h, exporting the treated tail water, repeating the above anaerobic process for many times, until the treatment of seawater aquaculture tail water is completed. The method has a short acclimation phase cycle, a short hydraulic retention time in the treatment phase, and can stably degrade the seawater aquaculture tail water of pollutants in the aquaculture tail water.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment, and in particular to a SBR treatment method for seawater aquaculture tail water. Background Art

[0002] Shrimp farming in high-level seawater ponds is a form of high-density stocking. With the rapid development of the shrimp farming industry in high-level seawater ponds, some problems have also arisen in the breeding process, including excessive accumulation of dissolved organic matter, deterioration of water quality, acidification of water bodies, and increased ammonia nitrogen content. The flow exchange capacity of the environment of the high-level seawater pond itself is relatively weak. Specifically, in the shrimp farming process, due to the lack of reasonable and scientific use of various inputs (such as feed, drugs), the excessive amount of artificially added bait is not completely digested and absorbed by the cultured organisms, the excrement precipitation of the growth and metabolism of the cultured organisms, the accumulation of remains after the death of aquatic organisms, and the residues of chemical drugs, water pollutants continue to accumulate. After these substances are decomposed by microorganisms in the breeding environment, the content of pollutants such as organic matter, nitrite nitrogen, ammonia nitrogen, nitrate nitrogen, and active phosphate in the water environment is too high, exceeding the environmental capacity and the ability of the environment to self-purify, causing the water bodies in various coastal areas to be polluted. Therefore, solving the problem of seawater aquaculture tailwater treatment is the key to the sustainable development of the seawater aquaculture industry.

[0003] Activated sludge is formed by flocculation of microorganisms and substances in the water. Activated sludge has the ability to grow. After a period of domestication, it can degrade pollutants in aquaculture tail water, thereby achieving the purpose of removing pollutants. This technology has a good removal effect on elements such as phosphorus and nitrogen, and is a commonly used technology for sewage treatment.

[0004] As early as the beginning of the 20th century, the activated sludge process used the sequencing batch reactor (SBR, also known as intermittent activated sludge), but the SBR process requires precise automation technology control. Since the automation technology was not mature at that time, the SBR process failed to develop well. The operation of the SBR process can be divided into five stages, including water inlet, reaction, precipitation, water outlet and idle. The operation time of each stage needs to be automatically controlled. With the development and maturity of automation technology, the technology of automatically controlling the operation cycle time of the SBR reactor has been continuously improved. The research on using SBR reactors to treat marine aquaculture tail water has been paid attention to by countries around the world, and the SBR process has been well developed. In recent years, the SBR process has been applied to the treatment of pollutants such as nitrite nitrogen, ammonia nitrogen, nitrate nitrogen and COD in marine aquaculture tail water, and its removal rate has exceeded 90%. The entire process of the SBR process for treating marine aquaculture tail water is to react and precipitate in an SBR reactor, which has more advantages than the traditional plug-flow activated sludge treatment of tail water, as follows:

[0005] (1) The SBR process has a simple operation flow and flexible operation methods. The SBR process can perform different treatment operations on different tail waters. It only needs to formulate the operation mode and sequence and set the timing control for each operation step to treat different tail waters and make the treated tail water meet the discharge standards;

[0006] (2) The SBR reactor has the characteristics of a completely mixed reactor, which avoids the problem of water inflow interference during the operation of the traditional plug flow reactor, makes up for the shortcomings of weak reaction driving force and water back mixing in the traditional reactor, and has a relatively ideal precipitation effect;

[0007] (3) The SBR process can switch between aerobic and anoxic environments at any time, which can effectively solve the problem of activated sludge expansion caused by fungal growth and improve the impact load resistance of activated sludge;

[0008] (4) The SBR reactor has low manufacturing and operating costs. The SBR process is carried out in the same reactor, saving the cost of manufacturing equipment in separate processes for the traditional activated sludge method. The SBR reactor can be automatically controlled and occupies a small area, saving manpower and land resources.

[0009] However, SBR treatment of marine aquaculture tail water also has some disadvantages:

[0010] (1) The technology of SBR for treating marine aquaculture tailwater is not mature enough. During the operation of SBR reactor, it is difficult to acclimate sludge, improve sludge salinity tolerance and nitrogen load;

[0011] (2) During the operation of the bioreactor, the degradation effect of activated sludge on pollutants is unstable. Summary of the invention

[0012] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide an SBR treatment method for seawater aquaculture tail water, which has a short acclimatization period, a short hydraulic retention time in the treatment period, and can stably degrade pollutants in the aquaculture tail water.

[0013] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0014] A SBR treatment method for marine aquaculture tail water comprises the following steps:

[0015] S1. Acclimation stage:

[0016] S1.1, loading activated sludge into the SBR reactor;

[0017] S1.2, Aerobic-Anaerobic Alternation Stage:

[0018] S1.2.1. The simulated seawater aquaculture tail water is introduced into the SBR reactor. After anaerobic treatment for 5-7 hours, aeration treatment for 1-2 hours, and sedimentation for 8-12 minutes, the treated simulated seawater aquaculture tail water is led out of the SBR reactor.

[0019] S1.2.2, repeat step S1.2.1 multiple times until the SBR reactor runs for 70-80 days;

[0020] S1.3, Completely anaerobic stage:

[0021] S1.3.1. Introduce the simulated seawater aquaculture tail water into the SBR reactor and treat it with anaerobic sedimentation for 7-8 hours. Then, export the treated simulated seawater aquaculture tail water out of the SBR reactor.

[0022] S1.3.2, repeat step S1.3.1 multiple times until the SBR reactor runs for 120-125 days;

[0023] S2, processing stage:

[0024] S2.1. The tail water of aquaculture is introduced into the SBR reactor for anaerobic sedimentation treatment for 7-8 hours, and the treated tail water of aquaculture is led out of the SBR reactor.

[0025] S2.2, repeat step S2.1 multiple times until the treatment of the marine aquaculture tail water is completed.

[0026] In the above-mentioned SBR treatment method for marine aquaculture tail water, preferably, in the activated sludge, the microbial components and their percentages are: 25% to 30% of Planctomyces, 12% to 20% of Firmicutes, 10% to 15% of Proteobacteria, 7% to 8% of Acidobacteria, 5% to 10% of Bacteroidetes, 1.2% to 2.2% of Chlorobacteria, and 1.5% to 2.0% of Armored Fungi.

[0027] In the above-mentioned SBR treatment method for seawater aquaculture tail water, preferably, the components of the simulated seawater aquaculture tail water are: glucose 125-130 mg / L, NH4Cl 15.0-15.5 mg / L, KH2PO4 4.5-5.5 mg / L, NaNO2 2-3 mg / L, KNO3 12-18 mg / L, and sea crystal 4500-5500 mg / L.

[0028] In the above-mentioned SBR treatment method for seawater aquaculture tail water, preferably, the seawater aquaculture tail water is seawater high-level shrimp farming wastewater.

[0029] In the above-mentioned SBR treatment method for seawater aquaculture tail water, preferably, the rate at which the simulated seawater aquaculture tail water and the seawater aquaculture tail water are introduced into the SBR reactor is 0.15-0.25L / min, and the rate at which the simulated seawater aquaculture tail water and the seawater aquaculture tail water are exported from the SBR reactor is 0.15-0.25L / min.

[0030] Compared with the prior art, the advantages of the present invention are:

[0031] The present invention uses a sequencing batch reactor (SBR) to study and utilize aerobic-anaerobic alternation combined with complete anaerobic acclimation treatment technology. The research results show that after the acclimation treatment, the SBR bioreactor has a maximum removal rate of nitrite nitrogen, nitrate nitrogen, chemical oxygen demand, and total phosphorus in seawater high-level shrimp farming wastewater of more than 94%, and a maximum removal rate of ammonia nitrogen of 78%. Compared with other types of bioreactors for treating aquaculture tail water, the bioreactor SBR process has a short acclimation phase cycle and a short hydraulic retention time in the treatment phase, and can stably and quickly degrade pollutants in aquaculture tail water, and has strong high efficiency and feasibility in the treatment of seawater aquaculture tail water. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of the structure of the SBR reactor in this embodiment.

[0033] Figure 2 This is a curve chart showing the changes in nitrite nitrogen in the inlet and outlet water of the bioreactor.

[0034] Figure 3 This is a curve chart showing the changes in nitrate nitrogen in the inlet and outlet water of the bioreactor.

[0035] Figure 4 This is a curve chart showing the changes in ammonia nitrogen in the inlet and outlet water of the bioreactor.

[0036] Figure 5 This is the COD change curve of the bioreactor inlet and outlet water.

[0037] Figure 6 This is a curve chart showing the changes in total phosphorus in the inlet and outlet water of the bioreactor.

[0038] Figure 7 This is a graph showing the changing pattern of the effluent pH of the bioreactor. DETAILED DESCRIPTION

[0039] The present invention is further described below in conjunction with specific preferred embodiments, but the protection scope of the present invention is not limited thereby.

[0040] Embodiment 1:

[0041] This embodiment provides a SBR treatment method for marine aquaculture tail water, comprising the following steps:

[0042] S1. Acclimation stage:

[0043] S1.1, loading activated sludge into the SBR reactor;

[0044] S1.2, Aerobic-Anaerobic Alternation Stage:

[0045] S1.2.1. The simulated seawater aquaculture tail water is introduced into the SBR reactor at a rate of 0.15-0.25L / min. After anaerobic treatment for 5-7h, aeration treatment for 1-2h, and sedimentation for 8-12min, the treated simulated seawater aquaculture tail water is discharged from the SBR reactor at a rate of 0.15-0.25L / min.

[0046] S1.2.2, repeat step S1.2.1 multiple times until the SBR reactor runs for 70-80 days;

[0047] S1.3, Completely anaerobic stage:

[0048] S1.3.1. Introduce the simulated seawater aquaculture tail water into the SBR reactor at a rate of 0.15-0.25 L / min, and treat it by anaerobic sedimentation for 7-8 hours. Then, export the treated simulated seawater aquaculture tail water from the SBR reactor at a rate of 0.15-0.25 L / min.

[0049] S1.3.2, repeat step S1.3.1 multiple times until the SBR reactor runs for 120-125 days;

[0050] S2, processing stage:

[0051] S2.1, introduce the tail water of shrimp farming at high altitude in seawater into the SBR reactor at a rate of 0.15-0.25L / min, treat it with anaerobic sedimentation for 7-8h, and then export the treated tail water of shrimp farming at high altitude in seawater out of the SBR reactor at a rate of 0.15-0.25L / min,

[0052] S2.2, repeat step S2.1 multiple times until the treatment of the marine aquaculture tail water is completed.

[0053] In this embodiment, the inoculated sludge was taken from the seawater high-level shrimp pond of Maoming Sanbaolong Co., Ltd., and its microbial components and their percentages were: 25% to 30% of Planctomyces, 12% to 20% of Firmicutes, 10% to 15% of Proteobacteria, 7% to 8% of Acidobacteria, 5% to 10% of Bacteroidetes, 1.2% to 2.2% of Chlorobacteria, and 1.5% to 2.0% of Armored Fungi.

[0054] The composition of simulated seawater aquaculture tail water is: glucose 125-130 mg / L, NH4Cl 15.0-15.5 mg / L, KH2PO4 4.5-5.5 mg / L, NaNO2 2-3 mg / L, KNO3 12-18 mg / L, sea crystal 4500-5500 mg / L.

[0055] The invention process of the present invention is specifically described below:

[0056] 1. Experimental Design and Materials and Methods

[0057] 1 Design and operation of SBR reactor

[0058] 1.1 Design of SBR reactor

[0059] SBR reactor Figure 1 As shown, the reactor is configured as a circular column with an openable cover on the top and a reinforcement plate at the bottom to make the reactor more stable. The reactor H = 650 mm, r 内径 =120mm, wall thickness =5mm, the total effective volume of the reactor is 7L, two sampling ports, one water inlet and one water outlet are designed respectively, tail water is introduced into the lower part of the reactor by a peristaltic pump, the water outlet is at the upper part of the reactor, an oxygen pump and a stirrer are installed inside the reactor, the reactor has the ability to provide an aerobic environment when it is running, the running time of the oxygen pump and the stirrer is controlled by a relay, so that the reactor can run automatically.

[0060] 1.2 SBR reactor operating conditions setting

[0061] The reactor designed in this experiment can switch between aerobic and anoxic environments at any time. Domesticating activated sludge in an aerobic-anaerobic environment can effectively solve the problem of activated sludge swelling caused by fungal growth. Activated sludge has a stronger ability to withstand shock loads, and domesticating activated sludge in a completely anaerobic environment can save energy. In order to compare the effects of reactors in treating aquaculture tail water under an aerobic-anaerobic alternating environment and a completely anaerobic environment, the function of the reactor to switch between aerobic and anoxic environments is utilized. Activated sludge is domesticated in an aerobic-anaerobic alternating environment, so that the domesticated sludge can stably degrade pollutants in aquaculture tail water, and the activated sludge is re-domesticated in an anaerobic environment. When the domesticated sludge can stably treat various pollution indicators of aquaculture tail water, the effects of treating ammonia nitrogen, nitrite nitrogen, nitrate nitrogen, total phosphorus and chemical oxygen demand in aquaculture tail water under the two environments are compared.

[0062] The reactor was fed with simulated seawater aquaculture tail water with a salinity of 10 g / L, and the salinity of the simulated seawater aquaculture tail water increased stage by stage according to the sludge acclimation. The experimental operation cycle was 8 hours, with an inlet of 0.2 L / min and an outlet of 0.2 L / min. The operation changes of each operation stage of the SBR reactor were controlled by a time relay. Water samples were taken every other day to measure ammonia nitrogen, nitrite nitrogen, nitrate nitrogen, total phosphorus, chemical oxygen demand and pH in the water samples. The specific operating conditions are shown in Table 1. The aerobic-anaerobic alternation period was 1d to 75d of the reactor operation, and the complete anaerobic stage was 76d to 123d of the reactor operation.

[0063] Table 1 Reactor cycle operation parameters

[0064]

[0065] 2 Experimental inoculation of sludge and simulated seawater aquaculture tail water

[0066] The inoculum sludge was taken from the high-level shrimp pond of Maoming Sanbaolong Co., Ltd. The simulated seawater aquaculture tail water was added to the running SBR reactor as needed. Sea crystal was used to adjust the salinity of the simulated seawater aquaculture tail water in each stage. The main components of the simulated seawater aquaculture tail water are shown in Table 2.

[0067] Table 2 Composition and function of simulated marine aquaculture tail water

[0068]

[0069] 3. Determination and methods of experimental indicators

[0070] This study measured various indicators based on the national standard "Marine Survey Specification Part 4: Seawater Chemical Element Survey" (GB / T12763.4-2007) and "Chemical Oxygen Demand-Alkaline Potassium Permanganate Method" (GB 17378.4.32-2007). The specific measurement indicators are shown in Table 3, the reagent preparation is shown in Table 4, and the reagent and instrument material information is shown in Tables 5 and 6.

[0071] Table 3 Experimental determination indicators and methods

[0072] index Determination method pH pH Meter Nitrite Nitrogen Diazo-azo method Nitrate nitrogen Zinc-cadmium reduction method Total Phosphorus Potassium persulfate oxidation method Ammonia nitrogen Sodium hypobromite oxidation method Chemical oxygen demand Alkaline potassium permanganate method

[0073] Table 4 Reagent preparation

[0074]

[0075]

[0076] Table 5 Reagent information

[0077]

[0078]

[0079] Table 6 Instrument material information

[0080] Instrument Name Manufacturer Laboratory grade ultrapure water machine Nanjing E-Puda Technology Development Co., Ltd. ELISA reader BIO-RADimark Microplate Reader 2μL~20μL pipette Eppendorf 20μL~200μL pipette Eppendorf 100μL~1000μL pipette Eppendorf 1μL~200μL Pipette Tips TS 1μL~1000μL Pipette Tips RonMark Digestion Instrument Lianhua Technology Co., Ltd. UV spectrophotometer Puxi General Instrument Co., Ltd. Peristaltic Pump Driver Baoding Lange Constant Flow Pump Co., Ltd. Constant speed electric stirrer Shibo Instruments

[0081] 3.1 Determination of nitrite nitrogen

[0082] The specific steps for drawing the standard working curve of nitrite nitrogen are as follows:

[0083] (1) Add NO2 to six parallel 2 mL disposable plastic centrifuge tubes with round bottom screw caps. - -N standard working solution 0.00, 0.04, 0.08, 0.16, 0.24, 0.32mL, transferred into ultrapure water to dilute to a volume of 1mL;

[0084] (2) Add 20 μL of 10 g / L 4-aminobenzenesulfonamide solution, shake well, and react for 5 min;

[0085] (3) Pipette in 20 μL of 1 g / L N-(1-naphthyl)-ethylenediamine dihydrochloride solution, shake well, and react for 15 min;

[0086] (4) Use a 1 mL pipette to transfer 0.3 mL of the sample solution to a standard flat-bottom 96-well ELISA plate, place the plate in an ELISA reader, measure the absorbance (Ab) of each sample solution at a wavelength of 543 nm, and record the absorbance of the sample solution;

[0087] (5) Using the absorbance of the six test samples as the ordinate, plot NO2 - -N standard working solution concentration as the horizontal axis, draw the standard working curve, and find its regression equation.

[0088] NO2 in aquaculture tail water samples - -N determination process: transfer 1mL of water sample into a 2mL disposable plastic centrifuge tube, transfer 20μL of 10g / L 4-aminobenzenesulfonamide solution, shake well, react for 5min, then transfer 20μL of 1.0g / L N-(1-naphthyl)-ethylenediamine dihydrochloride solution, shake well, react for 15min, use a 1mL pipette to transfer 0.3mL of the sample solution into a standard flat-bottom 96-well ELISA plate, place it in an ELISA instrument and measure the absorbance (Ab) of each sample solution at a wavelength of 543nm, record the absorbance of the sample solution, substitute it into the regression equation of the standard working curve, and calculate the NO2 - -N concentration.

[0089] 3.2 Determination of nitrate nitrogen

[0090] The specific steps for drawing the standard working curve of nitrate nitrogen are as follows:

[0091] (1) Add NO3 to six parallel 2 mL disposable plastic centrifuge tubes with round bottom screw caps. - -N standard working solution 0.00, 0.02, 0.04, 0.08, 0.12, 0.16mL, transferred into artificial seawater with a salinity of 7.5psu to dilute to a volume of 1mL;

[0092] (2) 1.5cm 2 Add the clean zinc rolls to the centrifuge tube, then transfer 20 μL of 20 g / L cadmium chloride solution, cover the centrifuge tube with the screw cap and quickly place it on the oscillator for 10 minutes. After the shaking is completed, quickly remove the zinc rolls;

[0093] (3) Add 20 μL of 10 g / L 4-aminobenzenesulfonamide solution, shake well, and react for 5 min;

[0094] (4) Pipette in 20 μL of 1 g / L N-(1-naphthyl)-ethylenediamine dihydrochloride solution, shake well, and react for 15 min;

[0095] (5) Use a 1 mL pipette to transfer 0.3 mL of the sample solution to a standard flat-bottom 96-well ELISA plate, place the plate in an ELISA reader, measure the absorbance (Ab) of each sample solution at a wavelength of 543 nm, and record the absorbance of the sample solution;

[0096] (6) Using the absorbance of the six test samples as the ordinate, plot NO3 - -N standard working solution concentration as the horizontal axis, draw the standard working curve, and find its regression equation.

[0097] NO3 in aquaculture tail water samples - -N determination process: transfer 1 mL of water sample into a 2 mL disposable plastic centrifuge tube and place 1.5 cm 2 Add the clean zinc roll to the centrifuge tube, add 20μL of 20g / L cadmium chloride solution, cover the centrifuge tube with the screw cap and quickly place it on the oscillator for 10 minutes. After the shaking is completed, quickly remove the zinc roll, add 20μL of 10g / L 4-aminobenzenesulfonamide solution, shake well, react for 5 minutes, add 20μL of 1g / L N-(1-naphthyl)-ethylenediamine dihydrochloride solution, shake well, react for 15 minutes, use a 1mL pipette to transfer 0.3mL of the sample solution into the standard flat-bottom 96-well ELISA plate, put it into the ELISA instrument, and measure the absorbance (Ab) of each sample solution at a wavelength of 543nm. Record the absorbance of the sample solution and substitute it into the regression equation of the standard working curve to calculate the NO3 - -N concentration.

[0098] 3.3 Determination method of ammonia nitrogen

[0099] The specific steps for drawing the standard working curve of ammonia nitrogen are as follows:

[0100] (1) Add NH4 to six parallel 2 mL disposable plastic centrifuge tubes with round bottom screw caps. + -N standard working fluid

[0101] 0.00, 0.02, 0.04, 0.08, 0.12, 0.16 mL, transfer into ultrapure water and dilute to a volume of 1 mL;

[0102] (2) Add 100 μL of sodium hypobromite oxidant, shake well, and react for 30 min;

[0103] (3) Add 20 μL of 2 g / L 4-aminobenzenesulfonamide solution, shake well, and react for 5 min;

[0104] (4) Pipette in 20 μL of 1 g / L N-(1-naphthyl)-ethylenediamine dihydrochloride solution, mix well, and react for 15 min;

[0105] (5) Use a 1 mL pipette to transfer 0.3 mL of the sample solution to a standard flat-bottom 96-well ELISA plate, place the plate in an ELISA reader, measure the absorbance (Ab) of each sample solution at a wavelength of 543 nm, and record the absorbance of the sample solution;

[0106] (6) Using the absorbance of the six test samples as the ordinate, + -N standard working solution concentration as the horizontal axis, draw the standard working curve, and find its regression equation.

[0107] NH4 + -N determination process: transfer 1mL of water sample into a 2mL disposable plastic centrifuge tube, transfer 100μL of sodium hypobromite oxidant, shake well, react for 30min, transfer 20μL of 2g / L 4-aminobenzenesulfonamide solution, shake well, react for 5min, transfer 20μL of 1g / L N-(1-naphthyl)-ethylenediamine dihydrochloride solution, mix well, react for 15min, use a 1mL pipette to transfer 0.3mL of the sample solution into a standard flat-bottom 96-well ELISA plate, place it in an ELISA instrument, and measure the absorbance (Ab) of each sample solution at a wavelength of 543nm. Record the absorbance of the sample solution, substitute it into the regression equation of the standard working curve, and calculate the NH4 + -N concentration.

[0108] 3.4 Determination of total phosphorus

[0109] The specific steps for drawing the standard working curve of total phosphorus are as follows:

[0110] (1) Add PO4 to six parallel 18 mL round-bottom screw-cap glass digestion tubes. 3- -P standard working fluid

[0111] 0.00, 0.30, 0.60, 1.20, 2.40, 3.00 mL, transfer into ultrapure water and dilute to a volume of 10 mL;

[0112] (2) Transfer 1 mL of potassium persulfate solution, shake well, tighten the screw cap, wipe the bottom of the digestion tube until it is clean and free of water, and place it in a Lotus digestion instrument at a temperature of 120°C for 30 min. After digestion, cool the temperature to room temperature;

[0113] (3) Pipette in 200 μL of 54 g / L ascorbic acid solution, tighten the cap, and shake well;

[0114] (4) Add 800 μL of sulfuric acid-molybdic acid-potassium antimony tartrate mixed solution (mixing ratio 5:2:1) and 200 μL of 54 g / L ascorbic acid solution, shake well, and react for 10 min;

[0115] (5) The reaction-completed sample is transferred into a cuvette, the cuvette is placed in a UV spectrophotometer, and the absorbance (Ab) of each sample solution to be tested is measured at a wavelength of 882 nm, and the absorbance of the sample solution to be tested is recorded;

[0116] (6) Using the absorbance of the six test samples as the ordinate, plot PO4 3- -P standard working solution concentration as the horizontal axis, draw the standard working curve, and find its regression equation.

[0117] PO4 of aquaculture tail water samples 3- -P determination process: transfer 10mL of water sample into a 18mL round-bottom screw-capped glass digestion tube, transfer 1mL of potassium persulfate solution, shake well, tighten the screw cap, and wipe the bottom of the digestion tube until it is clean and free of water, and place it in a lotus digestion instrument at a temperature of 120℃ for digestion for 30min. After digestion, lower the temperature to room temperature, transfer 200μL of 54g / L ascorbic acid solution, tighten the screw cap, shake well, transfer 800μL of sulfuric acid-molybdic acid-potassium antimony tartaric acid mixed solution (mixing ratio 5:2:1) and 200μL of 54g / L ascorbic acid solution, mix well, react for 10min, transfer the sample after the reaction into a cuvette, place the cuvette in a UV spectrophotometer, measure the absorbance (Ab) of each sample solution at a wavelength of 882nm, record the absorbance of the sample solution to be tested, substitute it into the regression equation of the standard working curve, and calculate the PO4 of the water sample. 3- -The concentration of P.

[0118] 3.5 Determination of Chemical Oxygen Demand (COD)

[0119] The specific steps for standardizing sodium thiosulfate standard solution are as follows:

[0120] (1) In two parallel iodine volumetric flasks, add 10 mL of 0.01 mol / L potassium iodate standard working solution along the bottle wall, and use a wash bottle to spray a small amount of pure water onto the bottle wall;

[0121] (2) Add 0.5 g of potassium iodide, add 1 mL of 0.45 g / mL sulfuric acid solution along the bottle wall, mix well, cover the bottle cap, add a small amount of water to seal the bottle mouth, and react for 2 min;

[0122] (3) Gently unscrew the cap and add 50 mL of pure water along the bottle wall. While shaking continuously, titrate the solution with sodium thiosulfate solution until it turns light yellow.

[0123] (4) Add 1 mL of 5 g / L starch solution and titrate with sodium thiosulfate solution while shaking continuously until the blue color of the solution disappears. Record the amount of sodium thiosulfate solution used.

[0124] The determination process of COD of aquaculture tail water samples: transfer 100mL of water sample into a conical flask, add 1mL of 250g / L sodium hydroxide solution, mix well, then add 10mL of 0.01mol / L potassium permanganate solution, mix well, heat to boiling, boil accurately for 10min, put it into a water tank and quickly cool it to room temperature, add 5mL of sulfuric acid solution, add 0.5g of potassium iodide, mix well, and conduct a dark reaction for 5min. Under continuous shaking, titrate the solution with a calibrated sodium thiosulfate solution until it turns light yellow, add 1mL of 5g / L starch solution, and titrate with sodium thiosulfate solution under continuous shaking until the blue color of the solution just disappears, and record the amount of sodium thiosulfate solution used. Repeat the above experiment with ultrapure water instead of the water sample to obtain a blank control.

[0125] 4 Data analysis

[0126] 4.1 Calculation of nitrite nitrogen concentration

[0127] The calculation method of nitrite nitrogen concentration is as follows:

[0128] Nitrite nitrogen concentration = [(A1-A2)-a] ÷ b

[0129] Where:

[0130] A1—Determine the average absorbance of water samples

[0131] A2—Determination of ultrapure water absorbance

[0132] a—Slope intercept of standard curve

[0133] b—Slope of the standard curve

[0134] 4.2 Calculation of nitrate nitrogen concentration

[0135] The nitrate nitrogen concentration is calculated as follows:

[0136] Nitrate nitrogen concentration = [(A1-A2-A)-a] ÷ b

[0137] Where:

[0138] A1—Determine the average absorbance of water samples

[0139] A2—Determination of ultrapure water absorbance

[0140] A—Determination of the average absorbance of nitrite nitrogen

[0141] a—Slope intercept of standard curve

[0142] b—Slope of the standard curve

[0143] 4.3 Calculation of ammonia nitrogen concentration

[0144] The calculation method of ammonia nitrogen concentration is as follows:

[0145] Ammonia nitrogen concentration = [(A1-A2-0.85×A)-a]÷b

[0146] Where:

[0147] A1—Determine the average absorbance of water samples

[0148] A2—Determination of ultrapure water absorbance

[0149] A—Determination of the average absorbance of nitrite nitrogen

[0150] a—Slope intercept of standard curve

[0151] b—Slope of the standard curve

[0152] 4.4 Calculation of total phosphorus concentration

[0153] The total phosphorus concentration is calculated as follows:

[0154] Total phosphorus concentration = [(A1-A2)-a] ÷ b

[0155] Where:

[0156] A1—Average absorbance of water sample

[0157] A2—Determination of ultrapure water absorbance

[0158] a—Slope intercept of standard curve

[0159] b—Slope of the standard curve

[0160] 4.5 Calculation of Chemical Oxygen Demand Concentration

[0161] The calculation method of chemical oxygen demand is as follows:

[0162] Chemical oxygen demand = [c 硫代硫酸钠浓度 (V1-V2)×8×1000]÷V

[0163] Where:

[0164] c—titrated sodium thiosulfate concentration

[0165] V—Measure the volume of water sample

[0166] V1—The amount of sodium thiosulfate used to titrate ultrapure water

[0167] V2—The amount of sodium thiosulfate used to titrate the water sample

[0168] 4.6 Calculation of removal rate of environmental indicators

[0169] Analyze the changes in nitrite nitrogen, nitrate nitrogen, ammonia nitrogen, total phosphorus, and chemical oxygen demand, and calculate the removal rates of nitrite nitrogen, nitrate nitrogen, ammonia nitrogen, total phosphorus, and chemical oxygen demand. The calculation methods for the removal rates of each indicator are as follows:

[0170] Removal rate = [(c1-c2) / c1] × 100%

[0171] Where:

[0172] c1—influent pollutant concentration

[0173] c1—Effluent pollutant concentration

[0174] 2. Results and Analysis

[0175] 1. Changes of nitrite nitrogen in reactor inlet and outlet water under aerobic-anaerobic alternating and complete anaerobic conditions

[0176] The changes of nitrite nitrogen in the inlet and outlet water of the bioreactor under aerobic-anaerobic alternation and complete anaerobic conditions are as follows Figure 2As shown: the nitrite nitrogen content of the influent in this experiment was about 0.717 mg / L. The nitrite nitrogen removal rate increased from 16% to 75% during the initial 1d to 7d after the reactor was started. The analysis showed that before the activated sludge inoculated in the reactor was acclimated, denitrifying bacteria were cultivated in a completely anaerobic environment, which was conducive to denitrification and could quickly remove nitrite nitrogen in a short period of time. Therefore, the nitrite nitrogen removal rate gradually increased. During the 8d to 61d of operation of the reactor, the nitrite nitrogen removal rate showed a negative growth trend, and the removal rate changed greatly, and the effect of degrading nitrite nitrogen was not achieved. The analysis showed that under the conditions of aerobic-anaerobic alternation, the anaerobic reaction time of the activated sludge was insufficient, which was not conducive to the denitrification. As the aerobic reaction proceeds, the activity of aerobic bacteria in the sludge is increased, the growth of denitrifying bacteria in the sludge is inhibited, and even a large number of denitrifying bacteria are killed, resulting in the inability to remove nitrite nitrogen, and even the increase in the content of nitrite nitrogen, which cannot remove nitrite nitrogen; from 62d to 75d of operation of the reactor, the change in nitrite nitrogen removal rate is relatively stable. During this stage, the average removal rate of nitrite nitrogen is about 53%, the lowest removal rate is 0%, and the highest removal rate is 85%. Analysis shows that denitrifying bacteria have adapted to the aerobic-anaerobic alternating environment, and therefore can achieve the effect of stably degrading nitrite nitrogen, indicating that the method of using a bioreactor to treat nitrite nitrogen in shrimp tail water under aerobic-anaerobic alternating conditions is feasible.

[0177] From 76d to 109d of operation of the reactor, under completely anaerobic conditions, the change of nitrite nitrogen removal rate was relatively stable, with an average removal rate of about 65% and a maximum removal rate of 90%. However, the removal rates were -19% and -22% at 81d and 109d, respectively. Analysis showed that during the water sampling process, sludge flowed out along with the water samples, resulting in an increase in nitrite nitrogen content and a negative removal rate. From 110d to 123d of operation of the reactor, the nitrite nitrogen removal rate gradually increased, with an average removal rate of about 77%, a minimum removal rate of 30%, and a maximum removal rate of 94%. Analysis showed that denitrifying bacteria adapted to the environment, the number of bacteria increased, and a better removal effect on nitrite nitrogen was achieved. This shows that the method of using a bioreactor to treat nitrite nitrogen in shrimp tail water under completely anaerobic conditions is also feasible. Compared with aerobic-anaerobic alternating conditions, it is more efficient to use a bioreactor to treat nitrite nitrogen in shrimp tail water under completely anaerobic conditions.

[0178] 2 Changes of nitrate nitrogen in reactor inlet and outlet water under aerobic-anaerobic alternating and complete anaerobic conditions

[0179] The changes of nitrate nitrogen in the inlet and outlet water of the bioreactor under aerobic-anaerobic alternation and complete anaerobic conditions are as follows Figure 3As shown: the nitrate nitrogen content of the influent in this experiment was about 2.077 mg / L. During the initial 1d to 7d of the reactor startup, the nitrate nitrogen removal rate varied greatly, with the lowest removal rate reaching 52% and the highest reaching 100%. It was analyzed that before the activated sludge inoculated in the reactor was domesticated, denitrifying bacteria were cultivated in a completely anaerobic environment, which was conducive to denitrification and could accelerate the removal of nitrate nitrogen in a short period of time; during the 8d to 17d of the reactor operation, the nitrate nitrogen removal rate varied steadily, with the removal rate reaching 100%; during the 18d to 35d of the reactor operation, the nitrate nitrogen removal rate varied greatly, with the lowest removal rate reaching -26% and the highest reaching 100%. It was analyzed that during the water intake process, the activated sludge outflow, resulting in large changes in the nitrate nitrogen removal rate; from 36d to 55d of reactor operation, the change in nitrate nitrogen removal rate was stable, and the removal rate reached 100%; from 56d to 75d of reactor operation, the change in nitrate nitrogen removal rate was large, and the average nitrate nitrogen removal rate was about 84%, the lowest removal rate was 60%, and the highest could reach 100%. Analysis shows that in the aerobic stage, the activated sludge accumulated in the water intake after stirring, and the activated sludge flowed out as the water sampling was carried out, causing changes in the nitrate nitrogen content; in the entire aerobic-anaerobic alternating stage, the reactor had a more obvious effect on nitrate nitrogen removal, indicating that the method of using a bioreactor to treat nitrate nitrogen in shrimp tail water under aerobic-anaerobic alternating conditions is feasible.

[0180] From 76d to 95d of operation of the reactor, under completely anaerobic conditions, the nitrate nitrogen removal rate changed greatly, with an average nitrate nitrogen removal rate of about 67%, a minimum removal rate of 3%, and a maximum of 100%. Analysis shows that the denitrifying bacteria failed to adapt to the sudden change in acclimation conditions, and the number of denitrifying bacteria changed, resulting in the inability to stably and effectively remove nitrate nitrogen; from 96d to 107d of operation of the reactor, the nitrate nitrogen removal rate gradually decreased, with the lowest removal rate reaching -45%. Analysis shows that the denitrifying bacteria failed to adapt to the environment, and the original denitrifying bacteria began to die, resulting in denitrification. The nitrite nitrogen was weakened, and part of the nitrite nitrogen was converted into nitrate nitrogen, making the nitrate nitrogen content higher than the nitrate nitrogen content in the influent, and the removal rate was negative; from 108d to 123d of the reactor operation, the nitrate nitrogen removal rate gradually increased and then stabilized, the average nitrate nitrogen removal rate was about 90%, the lowest removal rate was 29%, and the highest was 100%. The analysis showed that the denitrifying bacteria began to adapt to the domestication environment, the number of denitrifying bacteria gradually increased, the denitrification effect was enhanced, and the nitrate nitrogen removal rate increased, indicating that the method of treating nitrate nitrogen in shrimp tail water with bioreactors under completely anaerobic conditions is also feasible. Compared with aerobic-anaerobic alternating conditions, bioreactors under completely anaerobic conditions are more efficient in treating nitrate nitrogen in shrimp tail water.

[0181] 3. Changes of ammonia nitrogen in the reactor inlet and outlet water under aerobic-anaerobic alternating and complete anaerobic conditions

[0182] The changes of ammonia nitrogen in the inlet and outlet water of the bioreactor under aerobic-anaerobic alternation and complete anaerobic conditions are as follows Figure 4 As shown in the figure: the ammonia nitrogen content of the influent in this experiment was about 35.33 mg / L. During the initial 1d to 19d of the reactor startup, the ammonia nitrogen removal rate changed steadily and reached 100%. The analysis showed that in the aerobic-anaerobic alternating environment, anaerobic bacteria failed to adapt to the environment, while ammonia oxidizing bacteria adapted to the environment faster and could effectively remove ammonia nitrogen. During the 20d to 41d of the reactor operation, the ammonia nitrogen removal first decreased and then increased, and the average ammonia nitrogen removal rate was about 59%. The lowest removal rate was 37% and the highest was 85%. The analysis showed that the anaerobic bacteria at this stage adapted to the aerobic-anaerobic alternating environment, and the growth of ammonia oxidizing bacteria was inhibited, making it impossible to efficiently remove ammonia nitrogen. During the 42d to 75d of the reactor operation, the ammonia nitrogen removal rate changed greatly, and the ammonia nitrogen removal rate increased. The average nitrogen removal rate is about -11%, the lowest removal rate is -140%, and the highest can reach 68%. Analysis shows that the increase in the number of anaerobic bacteria and the absorption of more nutrients make it impossible for ammonia oxidizing bacteria to obtain sufficient nutrients during the growth process, and even lead to the death of aerobic bacteria. At the same time, some microorganisms in the activated sludge cannot adapt to the aerobic-anaerobic alternating environment and gradually die. The heterotrophic bacteria in the activated sludge decompose the dead microorganisms and the nitrogen-containing organic matter in the activated sludge itself, which increases the ammonia nitrogen content, resulting in an increase in the ammonia nitrogen content instead of a decrease. Therefore, the ammonia nitrogen removal rate will be negative, which shows that the method of treating ammonia nitrogen in shrimp tail water by bioreactors under aerobic-anaerobic alternating conditions still needs to adjust the ratio of aerobic-anaerobic time.

[0183] From 76th to 97th day of the reactor operation, under completely anaerobic conditions, the ammonia nitrogen removal rate changed greatly and showed a negative growth.

[0184] The average removal rate of ammonia nitrogen is about -91%, and the lowest removal rate is -225%. The analysis shows that most of the nitrogen-containing aerobic microorganisms in this stage continue to die due to environmental changes. The heterotrophic bacteria in the activated sludge decompose the dead microorganisms, making the ammonia nitrogen content in the effluent higher than the ammonia nitrogen content in the influent, so the ammonia nitrogen removal rate shows a negative growth trend; from 98d to 123d of the reactor operation, the ammonia nitrogen removal rate shows an upward trend, the average removal rate of ammonia nitrogen is about 29%, the lowest removal rate is -13%, and the highest can reach 78%. The analysis shows that the number of nitrogen-containing aerobic microorganisms is almost gone, and the anaerobic ammonia-oxidizing bacteria also begin to adapt to the environment, the number begins to increase, and can remove ammonia nitrogen more effectively, so the ammonia nitrogen removal rate begins to rise, indicating that the method of using bioreactors to treat ammonia nitrogen in shrimp tail water under completely anaerobic conditions is feasible. Compared with completely anaerobic conditions, bioreactors under completely anaerobic conditions have better effects on treating ammonia nitrogen in shrimp tail water.

[0185] 4 Changes of COD in reactor inlet and outlet water under aerobic-anaerobic alternating and complete anaerobic conditions

[0186] The changes in COD of the bioreactor inlet and outlet water under aerobic-anaerobic alternation and complete anaerobic conditions are as follows Figure 5 As shown: The COD content of the influent in this experiment was about 7.579 mg / L. During the initial 1d to 9d of the reactor startup, the COD removal rate changed relatively steadily, with an average COD removal rate of about 24%, a minimum removal rate of 22%, and a maximum removal rate of 26%. Analysis shows that the aerobic time is shorter than the anaerobic time, the growth rate of aerobic microorganisms is slow, and the speed of processing organic matter is slow. Therefore, the COD removal rate is low. During the 10d to 41d of the reactor operation, the COD removal rate changed greatly during this stage, first decreasing and then increasing. The removal rate was as low as 15% and as high as 100%. Analysis shows that the growth rate of aerobic microorganisms that can degrade COD changes continuously during the adaptation stage, and the growth rate accelerates after adapting to the environment. The amount of COD increased, and the number of aerobic microorganisms that can degrade COD was sufficient to completely treat the organic matter in the reactor inlet water. Therefore, the speed of removing organic matter accelerated, and finally the organic matter was completely removed; the COD removal rate varied greatly from 42d to 75d of the reactor operation, and the average COD removal rate was about 32%, with the lowest removal rate reaching 12% and the highest reaching 59%. Compared with the previous stage, the COD removal rate decreased. Analysis shows that the anaerobic time is longer than the aerobic time, and the anaerobic bacteria adapt to the environment, increase in number, and absorb more nutrients, so that the aerobic microorganisms that can degrade COD cannot get sufficient nutrients to supply their own growth, resulting in a decrease in the number of aerobic microorganisms that can degrade COD, which leads to a weakened organic matter removal effect and a decrease in COD removal rate. In the entire aerobic-anaerobic alternation stage, the reactor has a more obvious COD removal effect, indicating that the method of using a bioreactor to treat COD in shrimp tail water under aerobic-anaerobic alternation conditions is feasible.

[0187] From 76d to 101d of the operation of the reactor, under completely anaerobic conditions, the COD removal rate changed greatly, with the lowest removal rate reaching 13% and the highest reaching 43%. The average COD removal rate was about 31%. Analysis shows that the anaerobic bacteria that can degrade COD have not yet fully adapted to the environment, so the effect of degrading COD is general; from 102d to 123d of the operation of the reactor, the COD removal rate increased, with the lowest removal rate reaching 37% and the highest reaching 98%. The average COD removal rate was about 64%. Analysis shows that the anaerobic bacteria that can degrade COD have adapted to the environment, the number has increased, and they can degrade COD better, indicating that the method of using bioreactors to treat COD in shrimp tail water under completely anaerobic conditions is also feasible. Compared with aerobic-anaerobic alternating conditions, bioreactors are more efficient in treating COD in shrimp tail water under completely anaerobic conditions.

[0188] 5. Changes of total phosphorus in the reactor inlet and outlet water under aerobic-anaerobic alternating and complete anaerobic conditions

[0189] The changes in total phosphorus in the bioreactor inlet and outlet water under aerobic-anaerobic alternation and complete anaerobic conditions are as follows Figure 6 As shown: the total phosphorus content of the influent in this experiment was about 6.84 mg / L. During the initial 1d to 13d after the reactor was started, the total phosphorus removal rate increased from a negative value to 29%. The analysis showed that the activated sludge inoculated in the reactor was obtained from a high-level shrimp pond. The shrimp in the shrimp pond were decomposed after death, and the activated sludge itself contained phosphorus, so the reactor effluent contained a large amount of phosphorus, resulting in a negative total phosphorus removal rate at the beginning. The activated sludge was taken out in an anaerobic environment before being domesticated. Therefore, denitrifying bacteria and polyphosphate bacteria were cultivated, which was conducive to the rapid removal of phosphorus in a short time and the total phosphorus removal rate increased. During the 14d to 45d of operation of the reactor, the total phosphorus removal rate changed relatively stably, with an average total phosphorus removal rate of about 9%, a minimum total phosphorus removal rate of -10%, and a maximum removal rate of 39%. The analysis showed that the insufficient anaerobic reaction time was not conducive to the growth of denitrifying bacteria and polyphosphate bacteria. At the same time, the sludge flowed out during the water sampling process. , resulting in a higher phosphorus content in the effluent than in the inlet. At the same time, with the progress of aerobic reaction, the activity of aerobic bacteria in the sludge is increased, which inhibits the growth of denitrifying bacteria and polyphosphate bacteria in the sludge, and phosphorus is difficult to be removed in large quantities. Therefore, the removal rate of total phosphorus is general; from 46d to 69d of operation of the reactor, the total phosphorus removal rate changed greatly. In this stage, the average removal rate of total phosphorus was about 16%, the lowest total phosphorus removal rate was -21%, and the highest removal rate was 48%. Analysis shows that during the process of water sampling in this stage, sludge flowed out, and the sludge itself contained phosphorus, resulting in a higher phosphorus content in the effluent than in the inlet. However, as the denitrifying bacteria and polyphosphate bacteria in the sludge adapted to the environment, the total phosphorus removal rate increased; from 70d to 75d of operation of the reactor, the removal rates were all negative, with the lowest removal rate being -111%. Analysis shows that during the process of water sampling in this stage, more sludge flowed out, resulting in a higher phosphorus content in the effluent than in the inlet. In general, phosphorus removal is also effective under aerobic-anaerobic alternating conditions, indicating that the method of using a bioreactor to treat total phosphorus in shrimp tail water under aerobic-anaerobic alternating conditions is feasible.

[0190] From 76d to 96d of operation of the reactor, under completely anaerobic conditions, the total phosphorus removal rate changed greatly and showed a downward trend. The average removal rate of total phosphorus was about 46%, with the lowest removal rate reaching 10% and the highest reaching 96%. The analysis shows that under completely anaerobic conditions, some anaerobic bacteria quickly adapt to the environment, increase in number, and absorb more nutrients. Denitrifying bacteria and polyphosphate bacteria fail to compete with other anaerobic bacteria and cannot obtain sufficient nutrients for their own growth, resulting in a decrease in the number of denitrifying bacteria and polyphosphate bacteria, thereby weakening the removal effect of total phosphorus. From 97d to 123d of operation of the reactor, the average removal rate of total phosphorus was about 64%, with the lowest removal rate reaching 13% and the highest reaching 90%. The analysis shows that denitrifying bacteria and polyphosphate bacteria gradually adapt to the competitive environment, can grow and reproduce normally, and can effectively remove total phosphorus. Therefore, the average removal rate of total phosphorus has increased, indicating that the method of using bioreactors to treat total phosphorus in shrimp tail water under completely anaerobic conditions is also feasible. Compared with aerobic-anaerobic alternating conditions, bioreactors are more efficient in treating total phosphorus in shrimp tail water under completely anaerobic conditions.

[0191] 6 Changes in pH of reactor effluent under aerobic-anaerobic alternation and complete anaerobic conditions

[0192] The pH variation of the effluent from the bioreactor under aerobic-anaerobic alternation and complete anaerobic conditions is as follows Figure 7 As shown in the figure: from 1d to 11d at the beginning of the reactor, the pH changes greatly, the pH decreases first and then increases, and the pH is in the weak alkaline range. It is analyzed that before the activated sludge inoculated in the reactor is domesticated, denitrifying bacteria are cultivated, and denitrification is carried out in a completely anaerobic environment, which increases the pH of the activated sludge itself. Therefore, after the operation of the reactor, the pH of the first effluent is higher; from 12d to 59d of the operation of the reactor, the pH changes greatly in this stage, and the pH has been decreasing, but it is still weakly alkaline. It is analyzed that in the aerobic-anaerobic alternating environment, aerobic microorganisms begin to adapt to the environment, and the growth rate keeps changing. After adapting to the environment, the growth rate accelerates and the number increases, which is not conducive to the denitrification. Therefore, the pH has been decreasing; from 59d to 75d of the operation of the reactor, the pH begins to rise and the alkalinity increases. It is analyzed that the anaerobic time is longer than the aerobic time, and the anaerobic bacteria adapt to the environment and the number increases, which is conducive to the denitrification. In the entire aerobic-anaerobic alternating stage, the pH fluctuates in the weak alkaline range.

[0193] From 76d to 95d of operation of the reactor, under completely anaerobic conditions, the pH changed greatly. The stage with the largest change was from 87d to 89d of operation of the reactor, when the pH dropped rapidly. Analysis showed that the sudden drop in temperature caused the denitrifying bacteria to die quickly and the rate of denitrification slowed down. With the continuous operation of the reactor, the microorganisms gradually adapted to the lower temperature environment, the denitrification gradually recovered, and the pH began to rise. From 96d to 123d of operation of the reactor, the pH did not change much and remained in the weak alkaline range. Analysis showed that at this stage, the acclimation stage had been completed and the pH was almost stable. During the entire completely anaerobic stage, the pH changes were the same as those in the aerobic-anaerobic alternation stage, and did not drop to acidity.

[0194] Discussion

[0195] Aerobic-anaerobic treatment can effectively solve the problem of activated sludge expansion caused by bacterial growth in bioreactors. Anaerobic treatment is conducive to denitrification and can more thoroughly remove nitrite nitrogen, nitrate nitrogen, ammonia nitrogen and total phosphorus. The anaerobic time set for the operation of the general reactor is longer than the aerobic time. Wang Zhe and others have found through experimental research that when the aerobic-anaerobic cycle is 10h, the effect of treating aquaculture tail water pollutants under different aerobic-anoxic time ratios is also different. By adjusting the aerobic-anaerobic time ratio, they can treat the removal rates of nitrite nitrogen, nitrate nitrogen, ammonia nitrogen and COD in aquaculture tail water to 91.8%, 30.65%, 94.45% and 97.92% respectively. In contrast, this study treated aquaculture tail water by operating the SBR bioreactor under the condition of an aerobic-anaerobic time ratio of 1.5h:6h. Although the removal effect of nitrite nitrogen in the aquaculture tail water was slightly smaller, the aerobic-anaerobic cycle was short, and the removal rates of nitrate nitrogen, ammonia nitrogen and COD could reach 98% to 100%, indicating that the overall operation effect of SBR was more efficient.

[0196] Complete anaerobic treatment is conducive to denitrification, and appropriate hydraulic retention time is the key to completely remove marine aquaculture tailwater. In this study, the SBR bioreactor can achieve a 94% nitrite nitrogen removal rate for aquaculture tailwater under completely anaerobic conditions with a hydraulic retention of 8 hours. The hydraulic retention time is short, and the removal effect of nitrite nitrogen in aquaculture tailwater is better. Jiang Yuli et al. conducted experimental research and found that the aerobic denitrification reactor can achieve a nitrate nitrogen removal rate of more than 90% for aquaculture tailwater under the condition of 9 hours of hydraulic retention. The nitrate nitrogen removal rate in this study can reach 100%. The hydraulic retention time in this study is shorter, and the removal effect of nitrate nitrogen in aquaculture tailwater is better. In this study, the removal rate of ammonia nitrogen by SBR in the anaerobic stage reached 78%, and the hydraulic retention time was short. Proper extension of the hydraulic retention time may improve the treatment effect of ammonia nitrogen. Lin Bing et al. conducted experimental research and found that under completely anaerobic conditions with a hydraulic retention time of more than 10 hours, the COD removal rate of the anoxic-dynamic membrane reactor to treat aquaculture tailwater reached 87%. In this study, the COD removal rate of SBR in the anaerobic stage can reach 98%, which can be more efficient in removing COD from aquaculture tailwater under conditions of shorter hydraulic retention time. Ma Hang et al. conducted experimental research and found that under aerobic conditions with a hydraulic retention time of 24 hours, the total phosphorus removal rate of the microalgae membrane reactor in aquaculture tailwater reached 77.9%. In comparison, in this study, the total phosphorus removal rate reached 96% under conditions of shorter hydraulic retention time. Therefore, the removal effect of total phosphorus in aquaculture tailwater in the anaerobic stage of SBR is more significant.

[0197] In summary, the SBR reactor in this study treated nitrate nitrogen, ammonia nitrogen, and COD better under aerobic-anaerobic alternating conditions than the above-mentioned studies; and the SBR reactor in this study treated nitrite nitrogen, nitrate nitrogen, COD, and total phosphorus better under completely anaerobic conditions than the above-mentioned studies. Therefore, compared with the current aquaculture tailwater treatment process, the SBR bioreactor in this study has certain advantages in treating marine aquaculture tailwater using aerobic-anaerobic alternation combined with completely anaerobic process.

[0198] IV. Conclusion and Outlook

[0199] This study uses SBR bioreactors to treat excess pollutants in aquaculture tailwater by combining aerobic-anaerobic alternation with complete anaerobic process. The maximum removal rate of nitrite nitrogen in this process is 94%; the maximum removal rate of nitrate nitrogen can reach 100%; the maximum removal rate of ammonia nitrogen can reach 100%; the maximum removal rate of COD can reach 100%; the maximum removal rate of total phosphorus can reach 96%. Compared with other bioreactors for treating aquaculture tailwater: In this study, SBR has a good effect on the degradation of nitrate nitrogen, ammonia nitrogen, and chemical oxygen demand in aquaculture tailwater during the aerobic-anaerobic alternation stage, and shortens the cycle of aerobic-anaerobic alternation; the complete anaerobic stage with 8h hydraulic retention has obvious degradation effects on nitrite nitrogen, nitrate nitrogen, ammonia nitrogen, chemical oxygen demand, and total phosphorus, and the hydraulic retention time is shorter, which can achieve stable and efficient degradation of pollutants in aquaculture tailwater.

[0200] The SBR designed by this research uses aerobic-anaerobic alternation combined with complete anaerobic process to treat aquaculture tail water, which is highly efficient and feasible. It can provide a theoretical reference for the efficient treatment of marine aquaculture tail water, and provide ideas for solving the problem of marine aquaculture tail water pollution. It is beneficial to reduce the degree of environmental pollution in coastal areas and is of great significance to environmental protection and ecological balance.

[0201] The above is only a preferred embodiment of the present application and does not constitute any form of limitation to the present application. Although the present application is disclosed as a preferred embodiment as above, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A SBR treatment method for marine aquaculture tail water, characterized in that: The following steps are involved: S1. Acclimation stage: S1.1, loading activated sludge into the SBR reactor; S1.2, Aerobic-Anaerobic Alternation Stage: S1.2.

1. The simulated seawater aquaculture tail water is introduced into the SBR reactor. After anaerobic treatment for 5-7 hours, aeration treatment for 1-2 hours, and sedimentation for 8-12 minutes, the treated simulated seawater aquaculture tail water is led out of the SBR reactor. S1.2.2, repeat step S1.2.1 several times until the SBR reactor runs for 70-80 days; S1.3, Completely anaerobic stage: S1.3.

1. Introduce the simulated seawater aquaculture tail water into the SBR reactor and treat it with anaerobic sedimentation for 7-8 hours. Then, export the treated simulated seawater aquaculture tail water out of the SBR reactor. S1.3.2, repeat step S1.3.1 multiple times until the SBR reactor runs for 120-125 days; S2, processing stage: S2.

1. The tail water of aquaculture is introduced into the SBR reactor for anaerobic sedimentation treatment for 7-8 hours, and the treated tail water of aquaculture is led out of the SBR reactor. S2.2, repeat step S2.1 multiple times until the treatment of marine aquaculture tail water is completed.

2. The SBR treatment method for seawater aquaculture tail water according to claim 1, characterized in that: The activated sludge contains microbial components and their percentages as follows: 25% to 30% of Planctomyces, 12% to 20% of Firmicutes, 10% to 15% of Proteobacteria, 7% to 8% of Acidobacteria, 5% to 10% of Bacteroidetes, 1.2% to 2.2% of Chlorobacteria, and 1.5% to 2.0% of Armored Fungi.

3. The SBR treatment method for seawater aquaculture tail water according to claim 1, characterized in that: The components of the simulated seawater aquaculture tail water are: glucose 125-130 mg / L, NH4Cl 15.0-15.5 mg / L, KH2PO4 4.5-5.5 mg / L, NaNO2 2-3 mg / L, KNO3 12-18 mg / L, and sea crystal 4500-5500 mg / L.

4. The SBR treatment method for seawater aquaculture tail water according to claim 1, characterized in that: The seawater aquaculture tail water is wastewater from shrimp farming at high altitude in seawater.

5. The SBR treatment method for seawater aquaculture tail water according to claim 1, characterized in that: The rate at which the simulated seawater aquaculture tail water and the seawater aquaculture tail water are introduced into the SBR reactor is 0.15-0.25 L / min, and the rate at which the simulated seawater aquaculture tail water and the seawater aquaculture tail water are exported from the SBR reactor is 0.15-0.25 L / min.

6. The SBR treatment method for seawater aquaculture tail water according to claim 1, characterized in that: The SBR reactor includes a reactor body, an oxygen pump and an agitator arranged in the reactor body, a first time relay arranged outside the reactor body and electrically connected to the oxygen pump, and a second time relay arranged outside the reactor body and electrically connected to the agitator; a water inlet, a water outlet and a sampling port are arranged on the side wall of the reactor body, and valves are arranged on the water inlet, the water outlet and the sampling port.

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