Mangrove forest sediment mediated mariculture tail water treatment method

Abstract

A mangrove forest sediment mediated mariculture tail water treatment method comprises the following steps: pretreating mariculture tail water to remove large-particle impurities in the mariculture tail water; introducing into an SBR (sequencing batch reactor) tank for heterotrophic nitrification treatment; before heterotrophic nitrification treatment, mangrove forest sediments are put into an SBR tank and domesticated to enrich AOB bacteria; then introducing into an up-flow denitrification filter tank for aerobic denitrification treatment, and before aerobic denitrification treatment, putting mangrove forest sediments into the up-flow denitrification filter tank and domesticating to enrich nirS type denitrifying bacteria; and finally, carrying out disinfection treatment to remove pathogens in the mariculture tail water. On the basis of a sequencing batch reactor and an up-flow denitrification filter which take domesticated mangrove forest sediments as activated sludge, a set of mariculture tail water treatment process is constructed, efficient removal of NH4 < + >-N, NO3 <->-N, COD and the like can be realized, and long-time operation can be maintained.

Description

Technical Field

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

[0003] In direct proportion to the booming development of marine aquaculture, there are increasingly prominent environmental problems, one of which is the obvious trend of eutrophication of aquaculture water bodies. Surveys show that inorganic nitrogen and active phosphates in many natural important fishery waters such as oceans and rivers are generally excessive; the widespread use of antibiotics in aquaculture also poses a potential threat to aquatic organisms and humans; in pursuit of excellent water quality, people extract a large amount of fresh water to maintain the water level of ponds, and discharge aquaculture tail water into surrounding waters, resulting in water quality deterioration, destroying sensitive aquatic environments such as wetlands and mangroves, and threatening the health of other aquatic animals. Marine aquaculture tail water refers to water bodies generated by marine aquaculture activities and discharged into the receiving sea area. These water bodies contain a variety of substances, and the main water quality indicators include: pH value, suspended solids (TSP), chemical oxygen demand (COD), active phosphate, inorganic nitrogen (nitrite nitrogen, ammonia nitrogen, nitrate nitrogen), heavy metal elements, etc. Due to the high salinity and poor biodegradability of marine aquaculture tail water, it is difficult to treat, and there is currently a lack of mature marine aquaculture tail water treatment models. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a method for treating seawater aquaculture tail water mediated by mangrove sediments.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A method for treating marine aquaculture tailwater mediated by mangrove sediments comprises the following steps:

[0007] S1: Pre-treat the tail water of marine aquaculture to remove large particles of impurities in the tail water of marine aquaculture;

[0008] S2: introducing the pretreated seawater aquaculture tail water into the SBR tank for heterotrophic nitrification treatment, with an aeration rate of 1.0-1.5 mg / L; before the heterotrophic nitrification treatment, adding mangrove sediments into the SBR tank and acclimating the mangrove sediments to enrich AOB bacteria;

[0009] S3: introducing the marine aquaculture tail water treated with heterotrophic nitrification into an upflow denitrification filter for aerobic denitrification treatment. Before the aerobic denitrification treatment, mangrove sediments are put into the upflow denitrification filter and the mangrove sediments are acclimated to enrich nirS-type denitrifying bacteria;

[0010] S4: The aquaculture tail water treated by aerobic denitrification is disinfected to remove pathogens in the aquaculture tail water.

[0011] Preferably, the process of acclimatization of mangrove sediments in the SBR tank is as follows:

[0012] First, the simulated seawater NH 4 + The mangrove sediments in the SBR tank were acclimated to ammonia nitrogen using the -N concentration method. The initial NH 4 + -N concentration is 15-25 mg / L, to simulate the NH of seawater in the SBR tank 4 + -N concentration is 100-120 mg / L; then the mangrove sediment in the SBR tank is first acclimated to salt tolerance by a method of increasing the salinity of simulated seawater in stages, the initial salinity of the simulated seawater in the SBR tank is 0.8%-1.2%, and the salinity of the simulated seawater in the SBR tank is 3%-3.5%.

[0013] Preferably, the adoption stage increases the simulated seawater NH 4 + The mangrove sediment in the SBR tank was acclimated to ammonia nitrogen by using a -N concentration method, specifically including:

[0014] The simulated seawater with an ammonia nitrogen concentration of 15-25 mg / L was used as the culture medium for the first stage of ammonia nitrogen resistance acclimation. The ammonia nitrogen concentration of the simulated seawater in the subsequent ammonia nitrogen resistance acclimation stages was increased by 8-12 mg / L. The simulated seawater at each stage of ammonia nitrogen resistance acclimation was introduced into the SBR tank in sequence, and the hydraulic retention time was controlled to be 38-48 h. The NH 2+ concentration of the simulated seawater after each stage of ammonia nitrogen resistance acclimation was detected. 4 + -N concentration, to NH 4 + When the -N removal rate is stabilized at 70-80%, the next stage of ammonia nitrogen tolerance acclimation begins; during the ammonia nitrogen tolerance acclimation process, continuous aeration is adopted with an aeration volume of 0.5-1.5 L / min.

[0015] Preferably, the method of increasing the salinity of simulated seawater in stages to perform the first salt tolerance acclimatization on the mangrove sediment in the SBR tank specifically comprises:

[0016] With salinity of 0.8%-1.2%, NH 4 +The simulated seawater with a concentration of 60-90 mg / L of ammonia nitrogen was used as the culture medium for the first stage of the first salt tolerance acclimation. The salinity of the simulated seawater in the subsequent stages of the first salt tolerance acclimation was increased by 0.4%-0.6% successively, and the ammonia nitrogen concentration remained unchanged. The simulated seawater in each stage of the first salt tolerance acclimation was introduced into the SBR tank reaction tank in sequence, and the hydraulic retention time was controlled to be 20-24 hours until the NH 4 + When the -N removal rate is stabilized at more than 80%, the next stage of cultivation begins; during the first salt tolerance acclimatization process, continuous aeration is adopted, the aeration volume is 0.2-0.5L / min, and the stirring intensity is 30-60r / min.

[0017] Preferably, the process of acclimatizing mangrove sediment in the upflow denitrification filter is as follows: first, the simulated seawater NO is increased in stages. 3- -N concentration method was used to acclimate the mangrove sediments in the upflow denitrification filter to nitrate tolerance. 3 - -N concentration is 220-280mg / L; and then the mangrove sediment in the upflow denitrification filter is subjected to a second salt tolerance acclimatization by increasing the salinity of the simulated seawater in stages until the salinity of the simulated seawater in the upflow denitrification filter is 3%-3.5%.

[0018] Preferably, the adoption stage increases the simulated seawater NO 3- The mangrove sediments in the upflow denitrification filter were acclimated to nitrate tolerance by using a -N concentration method, which specifically included:

[0019] with NO 3 - -N concentration of 50-80 mg / L simulated seawater was used as the culture medium for the first stage of nitrate tolerance acclimation. 3 - The concentration of -N was increased by 45-55 mg / L, and the simulated seawater at each stage of nitrate tolerance was introduced into the upflow denitrification filter in sequence, and the hydraulic retention time was controlled at 48-56 h until NO 3- When the -N removal rate is stabilized at more than 80%, the next stage of nitrate tolerance acclimatization begins; the air-drying cultivation method is adopted during the nitrate tolerance acclimatization process.

[0020] Preferably, the method of increasing the salinity of simulated seawater in stages to perform the second salt tolerance acclimatization on the mangrove sediment in the upflow denitrification filter specifically comprises:

[0021] With salinity of 0.8%-1.2%, NO 3 -The simulated seawater with a NO concentration of 220-280 mg / L was used as the culture medium for the first stage of the second salt tolerance acclimation. The salinity of the simulated seawater in the subsequent stages of the second salt tolerance acclimation was increased by 0.4%-0.6%, and NO 3 - -N concentration remained unchanged, the simulated seawater from each stage of the second salt tolerance acclimation was introduced into the upflow denitrification filter in sequence, and the hydraulic retention time was controlled at 12 to 20 hours until NO 3 - When the -N removal rate is stabilized at more than 80%, the next stage of cultivation begins; the second salt tolerance acclimatization process adopts the air-drying cultivation method.

[0022] Preferably, in the SBR tank, the amount of mangrove sediment added is 70%-80% of the volume of the SBR tank; in the upflow denitrification filter, the amount of mangrove sediment added is 70%-80% of the volume of the upflow denitrification filter.

[0023] Preferably, the disinfection treatment specifically includes: introducing the seawater aquaculture tail water treated by the DAT-IAT process into a disinfection tank, turning on the chlorine dioxide generator in the disinfection tank, and the residence time of the seawater aquaculture tail water in the disinfection tank is 5-10 hours.

[0024] Preferably, the pretreatment specifically comprises: subjecting the seawater aquaculture tail water to coarse filtration, homogenization, lifting and fine filtration treatments in sequence.

[0025] Compared with the prior art, the advantages of the present invention are:

[0026] The invention is based on a sequencing batch reactor process (Sequencing Batch Reactor Activated Sludge Process, SBR), designs an acclimation tank reactor using mangrove sediment as activated sludge, and enriches ammonia-oxidizing bacteria (AOB) in mangrove sediment by designing a special acclimation process and optimizing process parameters, so as to treat excess nitrogen in pretreated seawater aquaculture tail water and convert it into nitrate and nitrite; an upflow denitrification filter is used as the main nitrate nitrogen treatment process, mangrove sediment is put into the upflow denitrification filter, and a special gradient acclimation process is performed to enrich nirS type denitrifying bacteria in mangrove sediment, which can efficiently convert environmentally harmful substances in aquaculture tail water, namely nitrate and nitrite, and convert them into harmless nitrogen gas for release, thereby significantly reducing the adverse effects on the surrounding marine ecological environment and protecting the aquatic ecological environment; practice shows that the invention can achieve NH 4 + -N, NO 3 --N, COD, etc., and can maintain long-term operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a process flow chart of the mangrove sediment-mediated marine aquaculture tail water treatment method according to an embodiment of the present invention.

[0028] Figure 2 Figure 2 is the phylogenetic tree of AOB flora based on major OTUs.

[0029] Figure 3 This is the phylogenetic tree of the nirS gene of denitrifying bacteria from the bottom sediment of the domesticated upflow denitrifying filter. DETAILED DESCRIPTION

[0030] 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.

[0031] Embodiment 1:

[0032] The initial simulated seawater composition of this embodiment is shown in Table 1:

[0033] Table 1 Initial simulated seawater ratio

[0034]

[0035] like Figure 1 As shown, this embodiment provides a method for treating seawater aquaculture tailwater mediated by mangrove sediments, comprising the following steps:

[0036] 1) Pre-treat the tail water of marine aquaculture to remove large particles of impurities in the tail water of marine aquaculture.

[0037] In this embodiment, the pretreatment specifically includes: subjecting the seawater aquaculture tail water to coarse filtration, homogenization, lifting and fine filtration treatments in sequence.

[0038] 1.1) Coarse filtration

[0039] A coarse screen is used in the coarse filtration stage. The screen is a pretreatment device that protects the subsequent sewage treatment equipment from clogging. Its main function is to intercept and remove particles and substances in the sewage that may clog the subsequent treatment equipment such as pumps, pipes, valves, etc. and reduce the treatment efficiency. For sewage treatment plants that use treatment processes that have certain requirements on the influent water quality, such as AAO, oxidation ditch, SBR and its improved processes and other traditional secondary treatment processes, the screen system plays an important role and is one of the key steps to ensure the normal operation of the entire sewage treatment system. The classification of screens is mainly based on their filtration accuracy, that is, the size of the gap between the screen bars, and can be divided into three categories: coarse screens, fine screens and fine screens. The equipment selected for this design is coarse screens and fine screens.

[0040] The coarse screen is mainly used to effectively screen out large solid materials in the water, such as tree branches and leaves, plastic products, paper, etc., to ensure the normal operation of the subsequent sewage treatment equipment. The coarse screen needs to be cleaned and maintained to ensure its normal operation and filtering effect. Under normal circumstances, when mechanical slag removal is used, the filtration accuracy is selected to be 16-25mm; and when manual slag removal is used, the filtration accuracy is usually selected to be 25-40mm.

[0041] 1.2) Even water quality

[0042] In order to balance the water quality and quantity, a buffer area, the regulating tank, is set up in the sewage treatment system for pre-treatment, so that the sewage entering the system can be homogenized, thereby improving the impact resistance of the entire system, reducing the design scale and reducing costs. In addition, if other equipment in the process stops discharging sewage, the setting of the regulating tank can continue to provide sewage to ensure the normal operation of the entire system.

[0043] 1.3) Promotion

[0044] Lifting is mainly achieved by lifting pump stations. According to the conventional wastewater treatment process, lifting pump stations are important devices for providing power for wastewater treatment. The main function of the lifting pump is to stably and efficiently lift sewage from low-lying structures to high or distant structures, and at the same time promote the mixing effect of sewage for subsequent treatment and discharge. In the SBR process, since the treatment process has a fixed sequence, the operation of the lifting pump also needs to be coordinated with these stages. The introduction of the PLC automatic control system can ensure that the lifting pump operates at the correct and appropriate time and conditions, so that the process can achieve better results. In this design, the lifting pump station is built together with the regulating tank.

[0045] 1.4) Fine filtration

[0046] Fine filtration is achieved by fine screens. The function of fine screens is to remove smaller floating objects and small suspended particles missed by coarse screens on the basis of filtering large-volume substances by coarse screens, thereby reducing the operating load of subsequent sewage treatment equipment and improving the efficiency of the entire sewage treatment process. Its filtration accuracy is usually 2 to 15 mm. Although fine screens are similar to coarse screens in terms of control methods, fine screens require higher operating accuracy and require staff to make judgments and adjustments based on real-time conditions. Manual slag removal can ensure that the fine screen achieves the best effect when filtering small suspended particles and avoids possible misjudgments of the automatic control system. Therefore, manual operation and control are performed by personnel.

[0047] 2) The pretreated seawater aquaculture tail water is introduced into the SBR tank for heterotrophic nitrification treatment with a hydraulic retention time of 30 h.

[0048] In this embodiment, the acclimation tank device includes an acclimation tank, an aeration mechanism, a stirring mechanism, a temperature detection instrument and a pH detection instrument located in the acclimation tank, and adopts a PLC controller as the core and control unit, connecting monitoring equipment such as the temperature detection instrument, the pH detection instrument and the dissolved oxygen meter, as well as execution equipment such as the aeration mechanism and the stirring mechanism.

[0049] Specifically, this embodiment adopts a continuous aeration culture method, the aeration volume is 1.0-1.5 mg / L, an aeration sand head is used as an aerator, and an aeration pump is connected to a rotor flowmeter to adjust the oxygen supply of the device.

[0050] This embodiment adopts mechanical stirring, and the rotation speed of the mechanical stirrer is 100r / min.

[0051] This embodiment adopts a double-layer structure of a 100W electric heating tube and an acclimation tank, and is equipped with a temperature sensor to keep the temperature inside the tank relatively stable.

[0052] In this embodiment, an alkali solution tank is connected to a constant flow pump and equipped with a pH meter to maintain the relative stability of the pH value of the solution in the tank.

[0053] In this embodiment, a sludge activation tank is connected to the SBR acclimation tank, and part of the sludge in the acclimation tank is recovered by the sludge activation tank, with a return sludge ratio of 20% to 50%, and aeration activation is performed, thereby shortening the sludge acclimation cycle and improving the acclimation and tailwater treatment efficiency.

[0054] In particular, before the heterotrophic nitrification treatment, mangrove sediments were added into the SBR tank and the mangrove sediments were acclimated to enrich the AOB bacteria, wherein the amount of mangrove sediments added was 80% of the volume of the SBR tank.

[0055] In this embodiment, the collection process of mangrove sediments is as follows:

[0056] The mangrove ecological protection area of ​​Yangjiang City, Guangdong Province (21°45'18"-21°46'1"N, 111°44'26"-111°45'3"E) was selected as the study area for sediment sample collection. The sediment samples collected on site were packed in sterilized sealed bags and then placed in a 4°C refrigerator.

[0057] Specifically, the mangrove sediment is put into the SBR acclimation tank, and the process of acclimating the mangrove sediment in the SBR tank is as follows:

[0058] 1. Gradually increase ammonia nitrogen to acclimate AOB bacteria

[0059] (1) Initial stage: This design is based on the SBR process to design an acclimatization tank. The parameters (pH, DO, temperature, etc.) are controlled by a programmable logic controller (PLC). It is divided into five stages: water inlet, aeration, sedimentation, drainage, and standby. Mangrove sediments are loaded into the SBR reactor, and NH 4 + -N concentration of 20mg / L in simulated seawater aquaculture tail water, with a controlled hydraulic retention time of 42h and an initial aeration volume of 0.5mg / L. The NH 4 + -N, NO 2 - -N, COD and pH, when the effluent NH 4 + The -N removal rate is stabilized at around 80%, and the operation time is around 35-35 days, completing the initial stage of acclimatization in the SBR acclimatization tank.

[0060] (2) Ammonia nitrogen load increase stage: The simulated tail water with the same composition and proportion as the initial stage of marine aquaculture tail water is the first stage, and the NH 4 + -N content, simulated seawater aquaculture tail water was introduced into the SBR reactor, the hydraulic retention time was controlled to be 38-48h, the aeration volume was 1.0mg / L, and the NH-N content of the water after each stage was detected. 4 + -N removal rate stabilizes at around 70%-80%, and the next stage of cultivation begins. In the latter stage, NH 4 + The concentration of -N was 8-12 mg / L higher than that of the previous stage; each stage lasted for 7-10 days until the NH 4 + -N and NO 2 - The concentration of -N is 100-120 mg / L, NH 4 + -N and NO 2 - The -N removal rate was stabilized at around 70-80%, completing the domestication process of AOB bacteria in mangrove sediments.

[0061] 2. Gradually increase salinity to acclimate AOB bacteria

[0062] (1) Initial stage of salinity acclimation: salinity of 1%, NH 4 +-N concentration of 60-90 mg / L simulated seawater was introduced into the pool with an initial salinity close to the original salinity of mangrove sediments (about 1%). The SBR pool was started for continuous aeration with an initial aeration volume of 0.3 L / min and a stirring intensity of 50 r / min to ensure that the mangrove sediments were in full contact with the sewage. The changes in the mangrove sediment sludge were observed to ensure that AOB could grow and reproduce normally in a low-salinity environment.

[0063] (2) Gradually increase salinity: After the microorganisms adapt to the low-salinity environment, the salinity of the SBR reactor wastewater is gradually increased. The salinity in the first stage is controlled at 1%, and then the salinity is increased by 0.5% each time. The salinity content of each stage increases successively, and the NH3 content of the water treated in each stage is tested. 4 + -N, NO 2 - -N, COD and pH, each stage lasts for 10 to 15 days. When the data is stable, the next stage of cultivation begins. The hydraulic retention time of each stage is 20 to 24 hours. The degradation efficiency of ammonia nitrogen in mangrove sediments is closely monitored to ensure that AOB in mangrove sediments can adapt to the new salinity level. When the degradation efficiency is stably maintained at more than 80%, the next stage of cultivation begins. If the degradation efficiency of ammonia nitrogen in mangrove sediments decreases, the rate of salinity increase should be appropriately reduced, and more time should be given to AOB in mangrove sediments to adapt to salinity changes.

[0064] (3) Stabilization stage: After the mangrove sediment AOB adapts to the current salinity level, the salinity should be maintained for 10-12 days to consolidate the acclimatization results. During this period, the ammonia nitrogen concentration (60-90 mg / L) in the SBR reaction tank remains stable to stabilize the ammonia nitrogen treatment capacity of the SBR reaction tank.

[0065] Extraction of genomic DNA from sediments in SBR tanks after acclimation

[0066] Follow According to the steps described in Soil Genomic DNA Kit, 0.25 g of sediment after acclimation in the acclimation tank was taken to extract the microbial genomic DNA in the mangrove sediment. The specific steps are as follows:

[0067] (1) Place 0.25 g of sediment sample in a LysisTube, add 550 μL LB35S and 25 μL Proteinase K, and vortex on a vortex oscillator for 15 min.

[0068] (2) Add 200 μL Lysis Enhancer, mix well, heat in a 70°C water bath for 10 min, and centrifuge at 12,000 × g for 2 min.

[0069] (3) Take 500 μL of the supernatant after centrifugation and transfer it to a new 1.5 mL centrifuge tube. Add 200 μL PB35 and incubate on ice for 5 min. Then centrifuge at 12,000 × g for 3 min.

[0070] (4) Aspirate 500 μL of supernatant and transfer to a 1.5 mL centrifuge tube. Add 500 μL BB31 and mix well. Mix well the Magnetic Soil Beads and add 15 μL magnetic beads. Vortex for 5 min and place the centrifuge tube on a magnetic rack until the solution becomes clear.

[0071] (5) Discard the supernatant, add 800 μL of CB31, vortex for 5 min, and place the centrifuge tube on a magnetic rack until the solution becomes clear.

[0072] (6) Discard the supernatant, add 700 μL WB31, vortex for 3 min, and place the centrifuge tube on a magnetic rack until the solution is clear. Repeat this step once.

[0073] (7) While avoiding the magnetic beads, aspirate as much of the supernatant as possible and discard it. Dry it at room temperature for 8 minutes to allow the ethanol in the reagents in the previous step to evaporate completely.

[0074] (8) Add 75 μL of ultrapure water (ddH2O), vortex for 30 seconds, and incubate in a 65°C water bath for 5 minutes. During this period, take out the vortex once every 1.5 minutes for a total of 3 times.

[0075] (9) Place the extract on a magnetic rack and clarify. Divide the supernatant into two centrifuge tubes. Store 40 μL of the extract in a -80°C refrigerator and store the remaining extract in a -20°C refrigerator for the next experiment.

[0076] (10) Take 1 μL of the supernatant frozen at -20°C and measure the concentration and quality of the DNA in the supernatant.

[0077] PCR amplification of functional gene of AOB

[0078] The DNA extracted in 3.2.3 was used as a template and specific primer amoA-2R was used.

[0079] (CCCCTCKGSAAAGCCTTCTTC) and amoA-1F (GGGGTTTCTACTGGTGGT), and the functional gene of AOB was amplified by PCR.

[0080] The PCR amplification system is shown in Table 2:

[0081] Table 2 PCR reaction system

[0082]

[0083] The optimal PCR amplification conditions for AOB in the mangrove sediment sample were explored as follows: 95℃, 3min; 95℃, 5s; 55℃, 30s; 72℃, 1min; run 35 cycles, then extend at 72℃ for 10min, and finally store at 4℃.

[0084] After PCR amplification of the functional gene is completed, the product is mixed with GV dye and subjected to gel electrophoresis. After running the gel for about 30 minutes, the electrophoresis bands are observed, and then the target gene is recovered and purified.

[0085] Recovery, purification and high-throughput sequencing of target genes

[0086] Mix the PCR products of multiple samples, perform gel electrophoresis, and use a THBC-470 blue light gel cutter to carefully cut out the target band without cutting the DNA-free part as much as possible, and then immediately perform gel recovery and purification. The operation steps can be briefly summarized as follows:

[0087] Transfer the cut gel strip into a centrifuge tube - add Buffer MB to the gel block - heat in a 37°C water bath to dissolve the gel block - let stand at room temperature - centrifuge and discard the filtrate - add Buffer WB and centrifuge and discard the filtrate - repeat the previous step once - transpose and centrifuge - transpose and add 50 μL of Eliution Buffer - let stand at room temperature and centrifuge - obtain the eluted DNA.

[0088] Mix the DNA sample with Loading Buffer, then detect the target gene and observe the electrophoresis bands. If the purified product is compliant and clearly separated DNA bands can be seen, it will be sent to Genewise Biotechnology Co., Ltd. for high-throughput sequencing.

[0089] High-throughput sequencing data analysis

[0090] The software Mothurv.1.40.5 was used to process the sequences obtained from the raw data returned by the test, and the cutoff threshold was set to 0.09. Alpha diversity and Beta diversity analysis were performed on the samples. Then the samples were clustered, representative sequences were selected, and a phylogenetic evolutionary tree was constructed. The classic tree diagram was beautified into a circle diagram (CircleTree) on the iTOL website.

[0091] Validation analysis

[0092] Phylogenetic tree and community structure characteristics of AOB

[0093] The phylogenetic tree of AOB flora in mangrove sediments was drawn based on the main OTUs. Figure 2As shown: According to the classification of the phylogenetic tree, all OTUs can be divided into three clusters. Cluster 1 has the highest number of sequences, which is 113,386, accounting for 41.94%. A total of 14 OTUs, including OTU1, OTU4, OTU36, OTU98, OTU29, OTU67, OTU57, OTU5, OTU17, OTU3, OTU26, OTU2, OTU14, and OTU28, belong to cluster 1, which is similar to AOB (MK487377.1) found in salt marsh sediments in the Gulf of Mexico and AOB (EU6 51323.1); cluster2 has 13788 sequences, accounting for 5.10%, OTU24, OTU69, OTU19, OTU13, and OTU16 belong to cluster2, and the species has not been determined yet; cluster3 has the lowest number of sequences, 11497, accounting for 4.25%, OTU8, OTU11, and OTU15 belong to cluster3, which is similar to AOB (MW940588.1) found in Chinese mangrove sediments. In general, most of the OTUs in mangrove sediment AOB are clustered with sequences of uncultured strains in the environment, and are mainly closely related to sequences from the Gulf of Mexico, the estuary of San Francisco Bay, and Chinese mangrove sediments. These clustering data can show that the AOB types in the sampled mangrove sediments are more diverse and rich.

[0094] The analysis finally determined the microbial components and their percentages in the SBR acclimation tank after gradient acclimation: AOB belonged to Nitrosomonas and Nitrosospira: Nitrosomonas-related accounted for 28.7%, and was further divided into three subclades, namely Nitrosomonas oligotropha / ureae, Nitrosomonas europaea and Nitrosomonas-like. Nitrosomonas-like B branch contained most of the sample AOB, accounting for 69.3%, and Nitrosospira accounted for 2.0%.

[0095] In this step, the SBR acclimation tank is the core of the process. Under the intermittent aeration operation mode, the mangrove sediment is put into the acclimation tank which integrates the functions of homogenization and biodegradation, so as to enrich the AOB with denitrification performance, treat the excess nitrogen in the marine aquaculture tail water and convert it into nitrate and nitrite.

[0096] Practice has shown that the SBR process based on mangrove sediment AOB mediation in this step can effectively treat high ammonia nitrogen and high salinity tail water produced by marine aquaculture, etc., and can provide important technical support for the sustainable development of aquaculture.

[0097] 3) The marine aquaculture tail water treated with heterotrophic nitrification is introduced into an upflow denitrification filter tank for aerobic denitrification treatment.

[0098] The denitrification filter is a sewage treatment process that integrates biological denitrification and filtration functions. It is a combination of biofilm treatment technology and physical treatment technology. The water flow direction of the denitrification filter is divided into upward flow and downward flow. The water inlet of the upward denitrification filter is from the bottom of the pool and the water outlet is from the top of the pool. The inlet and outlet directions of the downward denitrification pool are opposite. The upward flow biological filter can adopt a higher filtration rate and occupy a small area. It is more resistant to hydraulic load impact and has a higher filter material filling height.

[0099] The main function of the filter material filled in the biological filter is to act as a biological carrier and intercept and filter suspended solids. The choice of filter material is an important factor affecting the treatment efficiency of the denitrification filter. At present, ceramsite and quartz sand are commonly used as the filling filter materials. From the perspective of denitrification effect, ceramsite has a better denitrification effect than quartz sand. The specific surface area and adsorption performance of ceramsite filter material are stronger than quartz sand, so more biofilm can be attached, and the denitrification effect is better. From the perspective of filtration effect, quartz sand filter material is better than ceramsite. Considering the denitrification efficiency, this design uses ceramsite as the filling filter material for the denitrification filter.

[0100] In particular, before aerobic denitrification treatment, mangrove sediments were added to the upflow denitrification filter and the mangrove sediments were acclimated to enrich nirS-type denitrifying bacteria.

[0101] Specifically, the mangrove sediment is put into the upflow denitrification filter, and the process of acclimatizing the mangrove sediment in the upflow denitrification filter is as follows:

[0102] 1. The denitrification filter uses the method of inoculation and biofilm to domesticate NIRS type denitrifying bacteria to tolerate nitrate. The domestication is divided into two stages:

[0103] (1) The first stage is biological inoculation and initial cultivation. Mangrove soil sediments are added to the denitrification filter. Mangrove soil sediments contain denitrifying bacteria. In order to promote the growth and reproduction of denitrifying bacteria, simulated seawater aquaculture tail water is introduced into the filter, in which NO 3 - -N concentration is 60mg / L, hydraulic retention time is 36-48h, the reactor is kept in low oxygen state, without any agitation, so that denitrifying bacteria proliferate in large quantities. When the denitrifying bacteria proliferate to a certain amount, they are directional domesticated to make them more adaptable to the sewage treatment environment with high salinity and high ammonia nitrogen.

[0104] (2) The second stage is to increase the nitrate treatment load of the denitrification filter. The community structure of NIRS-type denitrifying bacteria is understood through high-throughput sequencing. Then the nutrient addition amount is adjusted, the potassium nitrate concentration is increased in stages, and the concentration of potassium nitrate in the synthetic seawater aquaculture tail water is gradually increased and introduced into the denitrification filter reaction tank. The hydraulic retention time is controlled at 48 to 56 hours, and the NO content of the water after each stage of treatment is detected. 3 - -N, COD and pH, to NO in marine aquaculture tail water 3 + The concentration of -N is 220-280 mg / L, and then the NO in the tail water of marine aquaculture 3 + -N concentration is increased by 50mg / L compared with the previous stage; each stage lasts for 15 to 20 days. According to the adaptation of NIRS-type denitrifying bacteria in mangrove sediments and the nitrate degradation efficiency (maintained at more than 80%), it is ensured that NIRS-type denitrifying bacteria in mangrove sediments can efficiently degrade the gradually increasing nitrate concentration to improve the nitrate nitrogen removal efficiency of the denitrification filter.

[0105] 2. The denitrification filter uses the method of inoculation and biofilm to acclimate NIRS-type denitrifying bacteria to high salinity

[0106] The main purpose of salt acclimation is to improve the adaptability of denitrifying bacteria in high-salt environments and their ability to remove nitrate nitrogen, so as to ensure that the upflow denitrification filter can maintain stable and efficient operation when treating high-salt wastewater.

[0107] (1) The initial salt concentration was 1%, NO 3 - -N concentration of 220-280 mg / L simulated seawater is introduced into the upflow denitrification filter, that is, the filter is operated under the condition of initial salt concentration of 1%. The filter is kept under low oxygen conditions, without ventilation and stirring, and the growth of denitrifying bacteria in the sediment and the nitrate removal effect are observed. If the denitrifying bacteria can adapt and stably remove 90% of the nitrate nitrogen, it will enter the next stage.

[0108] (2) The second stage: gradually increase the salt concentration in the simulated seawater aquaculture tail water by 0.5% each time, NO 3 - -N concentration remains unchanged, observe for 5-10 days, control the hydraulic retention time to 12-20h, ensure that the denitrifying bacteria can adapt to the new salt concentration environment, and detect the NO in the water after each stage of treatment. 3 - -N, COD and pH, to NO 3 -When the -N removal rate stabilizes at more than 80%, start the next stage of cultivation; if the removal effect decreases or the growth of denitrifying bacteria is hindered, appropriately reduce the salt concentration and continue to observe.

[0109] (3) The third stage: When the denitrifying bacteria can adapt to the higher salt concentration of 3-4% and stably remove nitrate nitrogen, the effluent NO is continuously monitored. 3 - -N, COD and pH as well as the growth of denitrifying bacteria. When the denitrifying bacteria can adapt to the final salt concentration and stably remove nitrate nitrogen, the acclimation process can be considered complete. At this point, the upflow denitrification filter can operate stably at a higher salt concentration.

[0110] The phylogenetic tree of nirS gene constructed based on OUT level of 50 core OTUs selected from the bottom sediment of the upflow denitrification filter after the above acclimation treatment is shown in Figure 2. Figure 3 As shown in the figure, the tree structure is subdivided into 10 different clusters based on sequence clustering, among which cluster 1 has the largest number of sequences, 29,303, accounting for 19.88% of the total, while cluster 8 has the least number of sequences, only 3,810, accounting for 2.58%. The remaining clusters cover a range of sequence proportions from 3.49% to 16.78%.

[0111] Cluster 1 brings together OTU1, OTU7, OTU13, OTU16, OTU27, OTU30, OTU39, OTU48, and OTU49, indicating that they are closely related to the nirS-type denitrifying bacterial sequences (HQ882414 and HQ882417.1) from the sediments of the Pearl River Estuary. On the other hand, OTU5 and OTU33 are included in cluster 3, which are similar to the above-mentioned Pearl River Estuary sequences; cluster 2 contains OTU10, OTU33, and OTU40, which have high similarity with the denitrifying bacterial sequences (KU995374.1) found in local coastal wetlands. In addition, cluster 4 brings together OTU2, OTU3, OTU15, and OTU20, which match the known nirS-type denitrifying bacterial sequences (JX002733) in mangrove ecosystems. Cluster 5 includes OTU19 to OTU47, which are highly similar to denitrifying bacterial sequences in different environments, such as potato fields (FJ853966.1), the South China Sea (HQ666561), New England salt marshes (KF896049), and Bahia del Tobar, Mexico (KC614388.1). Cluster 6 includes OTU8, OTU21, OTU29, OTU32, and OTU44, which show a genetic relationship with nirS-type denitrifying bacterial sequences (such as KC2934453, DQ676190, and KX388846.1) in oily salt marsh environments along the Chesapeake Bay and the Gulf of Mexico. The members of cluster 7, OTU6, OTU9, OTU22, OTU41, and OTU46, have high sequence identity with nirS-type strains (e.g., KT444053 and JX941775) in intertidal marshes and Fujian river sediments. In cluster 8, OTU11 and OTU45 are associated with denitrifying bacterial sequences (KX510628) from beach sediments, while cluster 9, including OTU4 and OTU23, is similar to the nirS-type strain sequence (KX389087) from oily salt marshes along the Gulf of Mexico. This reveals the high diversity and widespread distribution of nirS-type denitrifiers in mangrove ecosystems.

[0112] The final microbial components and their percentages in mangrove sediments after acclimation treatment in the upflow denitrification filter were determined as follows: Proteobacteria 85.22%, Chloroflexi 10.22%, Aquatic bacteria 3.45%, and other phyla, including Actinobacteria, Planctomyces, and Bacteroidetes, accounting for 1.11% of the total.

[0113] After the upflow denitrification filter has been acclimated with mangrove sediments, the seawater aquaculture tail water that has been treated with heterotrophic nitrification can be introduced into the upflow denitrification filter pool that has been acclimated with mangrove sediments for aerobic denitrification treatment. The hydraulic retention time of aerobic denitrification treatment is 25-30h, and the aerobic denitrification treatment adopts the aeration culture method.

[0114] 4) Disinfecting the aquaculture tail water after aerobic denitrification treatment to remove pathogens in the aquaculture tail water.

[0115] In this embodiment, the disinfection treatment specifically includes: introducing the seawater aquaculture tail water treated by the SBR acclimation process into the disinfection pool, turning on the chlorine dioxide generator in the disinfection pool, and the seawater aquaculture tail water stays in the disinfection pool for 5-10 hours.

[0116] After years of development, chlorine dioxide disinfection technology has been proven to be a stable and effective treatment method. It is widely used in many fields and is favored for its simple operation and management process. The technology performs well in eliminating bacteria such as Escherichia coli, Salmonella typhi, Mycobacterium tuberculosis, and viruses, including hepatitis A and B viruses. In addition, the economy of chlorine dioxide disinfection is also a major advantage, because it is not only affordable as a disinfectant, but also has low power consumption during operation, thereby reducing the overall operating cost. In terms of equipment, it also has the advantages of simple structure, reliability and durability, low cost, and has achieved comprehensive localization, making maintenance and overhaul more convenient. Finally, the disinfection characteristics of chlorine dioxide also include a special residual chlorine effect, which can ensure that the treated water body still maintains the disinfection effect after discharge, effectively preventing the occurrence of secondary pollution.

[0117] The treatment effect of the marine aquaculture tail water treated by this embodiment is shown in Table 3. It can be seen that the treatment process of this embodiment can achieve NH 4 + -N, NO 3 - -N, COD, etc., and can stably and continuously treat marine aquaculture tail water for about 120-150 days.

[0118] Effect of marine aquaculture tail water treatment

[0119] Tail water index Influent concentration (mg / L) Outlet concentration (mg / L) Removal rate (%) Remark <![CDATA[NH 4 + -N]]> 20.8～32.2 3.5～8.5 73.6～83.2 Good removal effect <![CDATA[NO 2 - -N]]> 9.5～14.5 0.88～1.52 89.5～90.7 Good removal effect <![CDATA[NO 3 - -N]]> 105.5～139.8 10.5～13.8 90.1～95.0 Good removal effect COD 91.2～110.5 12.5～13.9 86.3～87.4 Good removal effect pH 7.7～8.2 7.3～7.8 - Stable water quality

[0120] 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 method for treating seawater aquaculture tailwater mediated by mangrove sediments, characterized in that: The following steps are involved: S1: Pre-treat the tail water of marine aquaculture to remove large particles of impurities in the tail water of marine aquaculture; S2: introducing the pretreated seawater aquaculture tail water into the SBR tank for heterotrophic nitrification treatment, with an aeration rate of 1.0-1.5 mg / L; before the heterotrophic nitrification treatment, adding mangrove sediments into the SBR tank and acclimating the mangrove sediments to enrich AOB bacteria; S3: introducing the marine aquaculture tail water treated with heterotrophic nitrification into an upflow denitrification filter for aerobic denitrification treatment. Before the aerobic denitrification treatment, mangrove sediments are put into the upflow denitrification filter and the mangrove sediments are acclimated to enrich nirS type denitrifying bacteria; S4: The aquaculture tail water treated by aerobic denitrification is disinfected to remove pathogens in the aquaculture tail water.

2. The method for treating seawater aquaculture tailwater mediated by mangrove sediments according to claim 1, characterized in that: The process of mangrove sediment acclimation in the SBR tank is as follows: First, the simulated seawater NH4 + -N concentration method was used to acclimate the mangrove sediments in the SBR tank to ammonia nitrogen tolerance. The initial NH4 + -N concentration is 15-25mg / L, to simulate the NH4 of seawater in the SBR tank + -N concentration is 100-120 mg / L; then the mangrove sediment in the SBR tank is first acclimated to salt tolerance by a method of increasing the salinity of simulated seawater in stages, the initial salinity of the simulated seawater in the SBR tank is 0.8%-1.2%, and the salinity of the simulated seawater in the SBR tank is 3%-3.5%.

3. The method for treating seawater aquaculture tailwater mediated by mangrove sediments according to claim 2, characterized in that: The adoption stage increases the simulated seawater NH4 + The mangrove sediment in the SBR tank was acclimated to ammonia nitrogen by using a -N concentration method, specifically including: The simulated seawater with an ammonia nitrogen concentration of 15-25 mg / L was used as the culture medium for the first stage of ammonia nitrogen resistance acclimation. The ammonia nitrogen concentration of the simulated seawater in the subsequent ammonia nitrogen resistance acclimation stages was increased by 8-12 mg / L. The simulated seawater at each stage of ammonia nitrogen resistance acclimation was introduced into the SBR tank in sequence, and the hydraulic retention time was controlled to be 38-48 h. The NH4 + -N concentration, to NH4 + When the -N removal rate is stabilized at 70-80%, the next stage of ammonia nitrogen tolerance acclimation is started; during the ammonia nitrogen tolerance acclimation process, continuous aeration is adopted with an aeration volume of 0.5-1.5 L / min.

4. The method for treating seawater aquaculture tailwater mediated by mangrove sediments according to claim 2, characterized in that: The method of increasing the salinity of simulated seawater in stages to perform first salt tolerance acclimatization on the mangrove sediment in the SBR tank specifically includes: With salinity of 0.8%-1.2%, NH4 + -N concentration of 60-90 mg / L simulated seawater is used as the culture medium for the first stage of the first salt tolerance acclimation. The salinity of the simulated seawater in the subsequent stages of the first salt tolerance acclimation increases by 0.4%-0.6% successively, and the ammonia nitrogen concentration remains unchanged. The simulated seawater in each stage of the first salt tolerance acclimation is introduced into the SBR tank reaction tank in sequence, and the hydraulic retention time is controlled to be 20-24h, until NH4 + When the -N removal rate is stabilized at more than 80%, the next stage of cultivation begins; during the first salt tolerance acclimatization process, continuous aeration is adopted, the aeration volume is 0.2-0.5L / min, and the stirring intensity is 30-60r / min.

5. The method for treating marine aquaculture tailwater mediated by mangrove sediments according to claim 1, characterized in that: The process of acclimatizing mangrove sediment in the upflow denitrification filter is as follows: first, the simulated seawater NO3 - -N concentration method was used to acclimate the mangrove sediments in the upflow denitrification filter to nitrate tolerance, until the NO3 - -N concentration is 220-280mg / L; and then the mangrove sediment in the upflow denitrification filter is subjected to a second salt tolerance acclimatization by increasing the salinity of the simulated seawater in stages until the salinity of the simulated seawater in the upflow denitrification filter is 3%-3.5%.

6. The method for treating seawater aquaculture tailwater mediated by mangrove sediments according to claim 5, characterized in that: The adoption stage increases the simulated seawater NO3 - The mangrove sediments in the upflow denitrification filter were acclimated to nitrate tolerance by using a -N concentration method, which specifically includes: NO3 - -N concentration of 50-80 mg / L simulated seawater was used as the culture medium for the first stage of nitrate tolerance acclimation, and the NO3 - -N concentration was increased by 45-55 mg / L, and the simulated seawater at each stage of nitrate tolerance was introduced into the upflow denitrification filter in sequence, and the hydraulic retention time was controlled at 48-56 h until NO3 - When the -N removal rate is stabilized at more than 80%, the next stage of nitrate tolerance acclimatization begins; the air-drying cultivation method is adopted during the nitrate tolerance acclimatization process.

7. The method for treating marine aquaculture tailwater mediated by mangrove sediments according to claim 5, characterized in that: The method of increasing the salinity of simulated seawater in stages to perform the second salt tolerance acclimatization on the mangrove sediment in the upflow denitrification filter specifically includes: With salinity of 0.8%-1.2%, NO3 - -N concentration of 220-280 mg / L simulated seawater was used as the culture medium for the first stage of the second salt tolerance acclimation. The salinity of the simulated seawater in the subsequent stages of the second salt tolerance acclimation was increased by 0.4%-0.6%, and NO3 - -N concentration remained unchanged, the simulated seawater from each stage of the second salt tolerance acclimation was introduced into the upflow denitrification filter in sequence, and the hydraulic retention time was controlled at 12 to 20 hours until NO 3- When the -N removal rate is stabilized at more than 80%, the next stage of cultivation begins; the second salt tolerance acclimatization process adopts the air-drying cultivation method.

8. The method for treating marine aquaculture tailwater mediated by mangrove sediments according to any one of claims 1 to 7, characterized in that: In the SBR tank, the amount of mangrove sediment added is 70%-80% of the volume of the SBR tank; in the upflow denitrification filter, the amount of mangrove sediment added is 70%-80% of the volume of the upflow denitrification filter.

9. The method for treating marine aquaculture tailwater mediated by mangrove sediments according to any one of claims 1 to 7, characterized in that: The disinfection treatment specifically includes: introducing the seawater aquaculture tail water treated by the DAT-IAT process into a disinfection pool, turning on the chlorine dioxide generator in the disinfection pool, and the seawater aquaculture tail water stays in the disinfection pool for 5-10 hours.

10. The method for treating marine aquaculture tail water mediated by mangrove sediments according to any one of claims 1 to 7, characterized in that: The pretreatment specifically includes: subjecting the seawater aquaculture tail water to coarse filtration, homogenization, lifting and fine filtration treatments in sequence.

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