Treatment system and method for tail water of shrimp culture in seawater higher-place pond

Abstract

The invention discloses a treatment system and method for tail water of shrimp culture in a seawater higher-place pond, the system comprises a settling pond, an ecological pond and a biochemical pond which are communicated in sequence, and a filter screen is arranged in the settling pond and used for settling particulate matters in the tail water of shrimp culture in the seawater higher-place pond; aquatic plants are planted in the ecological pool and are used for absorbing part of inorganic salts and organic matters in the tail water of the shrimps cultured in the seawater higher-place pool; a filler biological membrane is arranged in the biochemical pool and comprises filler and compound microorganisms attached to the filler; the compound microorganism is prepared from the following microorganism components in percentage by weight: 25%-35% of aeromycete, 25%-35% of proteobacteria, 10%-20% of pseudomonas, 8%-12% of nitrospirillum, 3%-8% of acidobacter, 3%-8% of actinomycete, 3%-5% of bacteroides, 2%-3% of menococcus virens and 1%-2% of thick-wall bacteria. The device has the advantages of small occupied area, efficient tail water treatment, stable operation and the like.

Description

Technical Field

[0001] The invention relates to the field of aquaculture wastewater treatment, and in particular to a system and method for treating shrimp tail water in a high-level seawater pond. Background Art

[0002] Aquaculture is an important pillar of the national economy. Aquatic product production is considered to be the most effective way to produce animal-based food and an important part of the global food supply chain. However, with the intensive development of aquaculture, a large number of pollutants produced during the aquaculture process have increased toxic substances such as ammonia, nitrite, and nitrate in the water, which not only affects the quality of aquatic products, but also damages the surrounding ecological environment with the discharge of aquaculture tail water, threatening the long-term sustainable development of aquaculture.

[0003] At present, the methods for treating aquaculture tailwater can be divided into three categories: physical treatment, chemical treatment and biological treatment. Physical treatment methods mainly include filtration method, foam separation method, etc. Chemical treatment methods mainly include ozone oxidation method, flocculation method, electrochemical method, etc. Biological treatment methods mainly include biofilm method, activated sludge method, etc.

[0004] Biological methods show good application prospects due to their advantages such as high efficiency, economy and greenness. Among them, filler biofilm technology is an emerging technology developed in recent years for aquaculture tailwater treatment, which has the advantages of low cost, flexible operation and high cleaning efficiency. Studies have shown that the nitrogen turnover capacity on the filler biofilm is stronger than that of the surrounding water environment, mainly because the microorganisms on the membrane participate in nitrogen metabolism activities. The microbial method is considered to be an economical and environmentally friendly tailwater nitrogen treatment method, which can significantly reduce the content of ammonia nitrogen, nitrite and nitrate in the water body, and achieve the purpose of in-situ denitrification and restoration of aquaculture tailwater. Denitrification is an important part of the nitrogen cycle. Denitrifying microorganisms use NO 3 - -N is an electron acceptor, which undergoes reduction reaction under anaerobic conditions and eventually generates N 2 , so that the excess nitrogen in the water is discharged into the atmosphere in the form of gas. After denitrification technology treatment, nitrates in aquaculture water can be effectively removed. This technology plays an important role in green aquaculture, system energy saving and loss reduction, and pollution control.

[0005] However, the tailwater from shrimp farming in high-level seawater ponds has a complex composition, rich in important environmental factors such as organic matter, inorganic nitrogen, phosphates, and suspended solids. Therefore, there are currently few reports on biological treatment of tailwater from shrimp farming in high-level seawater ponds, and these reports are limited to the experimental exploration stage. The factors that affect the actual biological treatment of tailwater from shrimp farming in high-level seawater ponds are relatively complex, mainly including biological carriers, selection of denitrifying bacteria, and enrichment and cultivation methods. Currently, there are problems such as poor treatment of marine aquaculture wastewater and unstable operation. Therefore, it is necessary to develop an efficient and stable method for biological treatment of tailwater from shrimp farming in high-level seawater ponds. Summary of the invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a system and method for treating shrimp tail water in a high-level seawater pond with a small footprint, high efficiency and stable operation.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] A system for treating shrimp tail water in a high-level seawater pond comprises: a sedimentation pond, an ecological pond and a biochemical pond connected in sequence.

[0009] The sedimentation tank is provided with a filter screen for settling particles in the shrimp tail water of the high-level seawater pool;

[0010] Aquatic plants are planted in the ecological pond to absorb some inorganic salts and organic matter in the shrimp tail water of the high-level seawater pond;

[0011] A filler biofilm is provided in the biochemical pool, and the filler biofilm includes a filler and composite microorganisms attached to the filler;

[0012] The microbial components in the composite microorganism and their percentage contents are: 25% to 35% of Planctomyces, 25% to 35% of Proteobacteria, 10% to 20% of Pseudomonas, 8% to 12% of Nitrospira, 3% to 8% of Acidobacteria, 3% to 8% of Actinobacteria, 3% to 5% of Bacteroidetes, 2% to 3% of Chloroflexi, and 1% to 2% of Firmicutes.

[0013] Preferably, the filler is one or more of high-density polyethylene, polyester and polyolefin.

[0014] Preferably, the initial loading amount of the composite microorganism is 15% to 25%.

[0015] Preferably, the composite microorganisms on the filler are obtained by the following pretreatment method:

[0016] The tail water from shrimp farming in high-level seawater ponds is passed through sedimentation tanks, ecological ponds and biochemical ponds in sequence, with a pretreatment time of 18 to 22 days.

[0017] Preferably, the total inorganic nitrogen load of the pretreatment sedimentation tank is 120-130 g·(m 3 d) -1 The total inorganic nitrogen load of the ecological pool is 135-145 g·(m 3 d) -1 The total inorganic nitrogen load of the biochemical pool is 200-210 g·(m 3 d) -1 .

[0018] Preferably, the aquatic plant is one or more of Gracilaria, Cattail, Phragmites australis, and Lotus.

[0019] Preferably, the planting density of the aquatic plants is 10 to 50 plants / m 2 .

[0020] Preferably, the sedimentation tank includes a sludge zone at the bottom, and an inflow zone, a sedimentation zone and an outflow zone located above the sludge zone, and the inflow zone, the sedimentation zone and the outflow zone are distributed in sequence; the center position of the sludge zone is recessed downward relative to its end, and the depth of the center position of the sludge zone is 3-5m.

[0021] Preferably, the porosity of the filter screen is 45% to 55%, and the pore size is 2 to 3 mm.

[0022] Preferably, the biochemical pool comprises a plurality of treatment chambers, which are connected end to end in sequence to form a serpentine channel, each treatment chamber is provided with a grid for preventing the filler biofilm from flowing out, and each treatment chamber is provided with a plurality of air pipes for providing air and causing the filler biofilm to churn.

[0023] The present invention also provides a method for treating tail water of shrimp cultured in a high-level seawater pond using the above-mentioned tail water treatment system of shrimp cultured in a high-level seawater pond, comprising the following steps:

[0024] S1: The tail water of shrimp culture in high-level seawater pond is discharged into the sedimentation tank for sedimentation treatment to separate the insoluble particles;

[0025] S2: The tail water after treatment in the sedimentation tank flows into the ecological pond, so that the aquatic plants in the ecological pond can absorb some inorganic salts and organic matter in the tail water;

[0026] S3: The tail water treated by aquatic plants flows into the biochemical pool so that the complex microorganisms attached to the biofilm of the filler can absorb the remaining inorganic salts and organic matter in the tail water.

[0027] Preferably, the treatment method is divided into three stages: early operation, mid-operation and late operation. The early operation period is 14 to 16 days, the mid-operation period is 18 to 22 days, and the late operation period is 8 to 12 days.

[0028] Preferably, the total inorganic nitrogen load of the sedimentation tank in the early stage of operation is 245-250 g·(m 3 d) -1 The total inorganic nitrogen load of the ecological pool is 155-160 g·(m 3 d) -1 The total inorganic nitrogen load of the biochemical pool is 520-540 g·(m 3 d) -1 The inorganic nitrogen load of the sedimentation tank in the middle of the treatment system operation is 270-290 g·(m 3 d) -1 The inorganic nitrogen load of the ecological pond in the mid-term operation is 210-230 g·(m 3 ·d)-1, the inorganic nitrogen load of the biochemical pool in the middle of operation is 670~680g·(m 3 d) -1 The inorganic nitrogen load of the sedimentation tank in the later stage of the treatment system operation is 410-416 g·(m 3 d) -1 In the later period of operation, the inorganic nitrogen load of the ecological pool was 310-315 g·(m 3 d) -1 In the later stage of operation, the inorganic nitrogen load of the biochemical pool is 2700~2800g·(m 3 d) -1 .

[0029] Preferably, the hydraulic retention time HRT of the shrimp tail water in the sedimentation tank, the ecological pond and the biochemical pond is B1 It is 250h / mu-350h / mu.

[0030] Note: HRT B1 It indicates the hydraulic retention time when the daily processing volume is 1 mu. If the daily processing volume is 10 mu, the hydraulic retention time HRT B10 The hydraulic retention time HRT is 25h-35h, and the average daily processing capacity is 100 mu. B100 2.5h-3.5h, and so on.

[0031] Compared with the prior art, the advantages of the present invention are:

[0032] By designing a high-level pond aquaculture tailwater treatment project, building sedimentation ponds, ecological ponds and biochemical ponds, using sedimentation, aquatic plant absorption and microbial absorption methods, and rationally designing pretreatment, pre-operation, mid- and post-treatment processes, the N and P contents in aquaculture tailwater can be effectively reduced, and the comprehensive water quality index WQI can be used to analyze the water quality of the entire tailwater treatment process. The research results show that the cooperation of the sedimentation pond, ecological pond and biochemical pond can effectively reduce the NH 4+ -N, NO 2 - -N, TP, COD, and TSS all have good treatment effects. In the later stage of the tailwater treatment project, NH 4 + -N, NO 2 - -The removal rates of N, TP, COD, and TSS were 89.60%, 96.41%, 84.76%, 21.56%, and 81.77%, respectively. Based on the comprehensive water quality index WQI analysis, compared with the water quality of untreated tail water, the aquaculture tail water effectively reduced the content of N, P, etc. after treatment, and the water quality was good, with a significant improvement. In addition, compared with other tail water treatment projects, especially the "three dams and two pools", the tail water treatment project of the present invention has the advantages of less land occupation and higher pollutant degradation efficiency, especially in terms of TSS treatment effect. The purification effect is obvious, which provides a powerful reference for the effective treatment of aquaculture tail water in high-level pools. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is the overall route map of the marine aquaculture tail water of the embodiment.

[0034] Figure 2 It is the overall design diagram of the tailwater treatment pool of the embodiment.

[0035] Figure 3 A schematic cross-sectional view of a sedimentation tank.

[0036] like Figure 4 This is a cross-sectional schematic diagram of the biochemical pool.

[0037] Figure 5 for Figure 4 A partial enlarged schematic diagram of .

[0038] Figure 6 Distribution map of sampling sites for different treatment pools. 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] The overall route of the tail water of seawater aquaculture in this embodiment is as follows: Figure 1The aquaculture tail water is collected through the sewage collection well and enters the sedimentation tank for sedimentation treatment. After the insoluble particles are sunk and separated by sedimentation, the tail water immediately flows into the ecological pool. The aquatic plants planted in the ecological pool will absorb the inorganic salts and organic matter such as N and P in the tail water. The tail water after preliminary treatment will flow into the biochemical pool. The microorganisms in the biochemical pool will further absorb the inorganic salts and organic matter such as N and P in the tail water to meet the discharge standards. The treated tail water flows from the biochemical pool into the sand filter pool. The sand filter pool contains a large amount of fine sand, which can filter most of the invertebrates such as rotifers and copepod larvae. The tail water after a series of treatments is recycled into the high-level pool or discharged into the ocean.

[0042] The overall design of the tailwater treatment pool in this embodiment is shown in Figure 2 It covers an area of ​​about 6.5 acres and is divided into four pools, namely sedimentation pool (1.50 acres), ecological pool (1.57), biochemical pool (1.08 acres) and sand filtration pool (1.65 acres).

[0043] Sedimentation tank

[0044] There are a lot of insoluble particles such as animal feces, leftover bait, mud and sand in the tailwater of aquaculture. If they are not treated and directly enter the biochemical pool, it is easy to cause the filter material in the biochemical pool to be blocked, which will reduce the biological treatment effect and affect the operation of tailwater treatment. The sedimentation tank mainly uses the difference in density between water and insoluble particles. Under the action of gravity, the insoluble particles sink, thereby achieving the purpose of separation.

[0045] like Figure 3 As shown in the figure, in this design, the sedimentation tank is 50m long and 20m wide, the embankment slopes downward, the center of the tank is the lowest point, and the depth is 4m. A tailwater inflow pipe is set at one end of the sedimentation tank, which is the inflow area. After the tailwater flows into the sedimentation tank through the pipe, it flows horizontally in the sedimentation area. During the flow, the particles gradually settle in the sludge area, and the upper water flows out in the outflow area and enters the next tailwater treatment tank.

[0046] Ecological Pond

[0047] The function of the ecological pond is to utilize the absorption of inorganic salts such as N and P and organic matter in the environment by the growth of aquatic plants, convert inorganic salts such as N and P in the tail water into organic matter and store it in the plant body, thereby reducing the content of inorganic salts such as N and P and organic matter in the tail water.

[0048] In this design, the ecological pond is 55m long, 18.5m wide on the short side and 20.7m wide on the long side. The pond embankment slopes downward in a gradient, with the center of the pond being the lowest point and a depth of 4m. The aquatic plants planted in the ecological pond are Gracilaria.

[0049] Biochemical pool

[0050] The biochemical pool is a treatment pool that uses the biofilm method to treat aquaculture tail water. The biofilm method uses microorganisms to attach to the surface of the filter carrier to form a film, and through contact with the tail water to be treated, the inorganic nutrients and organic matter in the tail water are absorbed by the microorganisms to purify the tail water.

[0051] like Figure 4 and Figure 5 As shown in the figure, the biochemical pool of this design is 45.9m long, 16m wide and 1.15m deep. The biochemical pool has 17 channels in total. Water flows in from the inlet, flows in a serpentine shape in the biochemical pool, and finally flows out from the outlet. There is a grid in each channel, which is used to fix the filter material and prevent it from being dispersed. There are four air pipes in each channel, which are used to provide air and make the filter material tumble, provide a growth environment for microorganisms and increase the contact area between the filter material and the tail water.

[0052] Sand filter

[0053] Sand filter uses sand and gravel to filter the tailwater of aquaculture, so that pollutants and microorganisms in the tailwater are trapped on the sand and gravel. According to Peng Jinhu's research, the effect of fine sand filter on removing organic matter is similar to that of ultrafiltration membrane, and it has the ability to remove ammonia nitrogen and retain invertebrates. The retention and filtration capacity of invertebrates such as rotifers and copepod larvae can reach 99%.

[0054] The sand filter tank in this design is 55m long, 20m wide and 4m deep. Four tailwater recycling pipes are laid at the bottom of the sand filter tank, and the upper layer is covered with fine sand. There are small holes on the tailwater recycling pipes, and the outer layer is covered with sand-proof gauze.

[0055] Average daily discharge of marine aquaculture tail water

[0056] Maoming Sanbaolong Co., Ltd. has more than 260 mu of high-level seawater aquaculture ponds. The discharge volume varies according to the pre-, mid- and late-stage of aquaculture and the water quality. The water is changed twice a day, and each time the water is changed by 0.15m of the water level of the aquaculture pond. The average daily discharge volume V = number of acres treated × 666.67 × 0.15 × 2 (m 3 ), and the calculation results are shown in Table 1 below.

[0057] Table 1 Statistics of daily discharge of aquaculture tail water

[0058] serial number Average daily processing capacity (mu) <![CDATA[Emission amount (m 3 )]]> <![CDATA[V 10 ]]> 10 2000 <![CDATA[V 20 ]]> 20 4000 <![CDATA[V 50 ]]> 50 10000 <![CDATA[V 100 ]]> 100 20000

[0059] Note: V 10 It represents the discharge volume when the daily treatment volume is 10 mu, V 20 It represents the discharge volume when the daily processing volume is 20 mu, V 50 It represents the discharge volume when the daily processing volume is 50 mu, V 100 It indicates the emission volume when the daily processing volume is 100 mu.

[0060] Mariculture tailwater flow

[0061] Marine aquaculture tailwater flow Q = daily average tailwater discharge V / time (m 3 / h), and the calculation results are shown in Table 2 below.

[0062] Table 2 Statistics of aquaculture tailwater flow

[0063]

[0064]

[0065] Note: Q 10 It represents the water flow rate when the daily treatment volume is 10 mu, Q 20 It represents the water flow rate when the daily treatment volume is 20 mu, Q 50 It represents the water flow rate when the daily treatment volume is 50 mu, Q 100 It indicates the water flow rate when the daily average treatment volume is 100 mu.

[0066] Hydraulic retention time of marine aquaculture tailwater treatment

[0067] Hydraulic Retention Time (HRT) refers to the average time that the wastewater to be treated reacts with microorganisms in the reactor. HRT = tank capacity / influent flow rate = V / Q (h).

[0068] Sedimentation tank

[0069] In the marine aquaculture tailwater treatment project, the sedimentation tank is 50m long and 20m wide. The embankment is gradient downward, with the center of the tank as the lowest point, the depth is 4m, and the highest water level is 3.5m. The effective tank capacity V can be calculated. A 2512m 3 :

[0070] Hydraulic retention time HRT A = Sedimentation tank capacity V A / water flow rate Q(h), the calculation results are shown in Table 3 below.

[0071] Table 3 Statistics of hydraulic retention time of sedimentation tank

[0072] serial number Average daily processing capacity (mu) Hydraulic retention time (h) <![CDATA[HRT A10 ]]> 10 30.15 <![CDATA[HRT A20 ]]> 20 15.07 <![CDATA[HRT A50 ]]> 50 6.03 <![CDATA[HRT A100 ]]> 100 3.02

[0073] Note: A stands for sedimentation tank, HRT A10 It indicates the hydraulic retention time of the sedimentation tank when the daily processing volume is 10 mu, HRT A20 It indicates the hydraulic retention time of the sedimentation tank when the daily processing capacity is 20 mu, HRT A50 It indicates the hydraulic retention time of the sedimentation tank when the daily processing volume is 50 mu, HRT A100 It indicates the hydraulic retention time of the sedimentation tank when the average daily processing capacity is 100 mu.

[0074] Ecological Pond

[0075] The ecological pond in the marine aquaculture tailwater treatment project is 55m long, 18.5m wide on the short side and 20.7m wide on the long side. The pond embankment is gradient downward, with the center of the pond as the lowest point, a depth of 4m and a maximum water level of 3.5m. B 2622m 3 :

[0076] Hydraulic retention time HRT B = Ecological pool capacity V B / water flow rate Q(h), the calculation results are shown in Table 4 below.

[0077] Table 4 Statistics of hydraulic retention time of ecological pond

[0078] serial number Average daily processing capacity (mu) Hydraulic retention time (h) <![CDATA[HRT B10 ]]> 10 31.47 <![CDATA[HRT B20 ]]> 20 15.73 <![CDATA[HRT B50 ]]> 50 6.29 <![CDATA[HRT B100 ]]> 100 3.15

[0079] Note: B stands for ecological pool, HRT B10 It represents the hydraulic retention time of the ecological pond when the daily treatment capacity is 10 mu, HRT B20 It represents the hydraulic retention time of the ecological pond when the daily processing capacity is 20 mu, HRT B50 It represents the hydraulic retention time of the ecological pond when the daily processing capacity is 50 mu, HRT B100 It indicates the hydraulic retention time of the ecological pond when the average daily processing capacity is 100 mu.

[0080] Biochemical pool

[0081] The biochemical pool is 45.9m long, 16m wide, 1.15m deep, with a maximum water level of 1m. Its pool capacity is V C 734.4m 3 :

[0082] Hydraulic retention time HRT C = Sedimentation tank capacity V C / water flow rate Q(h), the calculation results are shown in Table 5 below.

[0083] Table 5 Statistics of hydraulic retention time of biochemical pool

[0084] serial number Average daily processing capacity (mu) Hydraulic retention time (h) <![CDATA[HRT C10 ]]> 10 8.81 <![CDATA[HRT C20 ]]> 20 4.41 <![CDATA[HRT C50 ]]> 50 1.76 <![CDATA[HRT C100 ]]> 100 0.88

[0085] Note: C stands for biochemical pool, HRT C10 It indicates the hydraulic retention time of the biochemical pool when the daily processing volume is 10 mu, HRT C20 It means the hydraulic retention time of the biochemical pool when the daily processing volume is 20 mu, HRT C50 It indicates the hydraulic retention time of the biochemical pool when the daily processing capacity is 50 mu, HRT C100 It indicates the hydraulic retention time of the biochemical pool when the average daily processing capacity is 100 mu.

[0086] Biochemical pool organic load (F / M)

[0087] Organic load refers to the amount of organic matter that can be removed by a unit volume of treatment reactor per unit time. The amount of organic matter can be expressed by COD. According to existing measurement data, the average COD value of aquaculture ponds is 6.10 mg·L-1. The organic load is calculated as:

[0088] F / M=COD(g) / (V C d)

[0089] The calculation results of organic load are shown in Table 6 below.

[0090] Table 6 Statistics of organic load in biochemical pool

[0091] serial number Average daily processing capacity (mu) Organic Load <![CDATA[F / M C10 ]]> 10 15.61 <![CDATA[F / M C20 ]]> 20 33.22 <![CDATA[F / M C50 ]]> 50 78.05 <![CDATA[F / M C100 ]]> 100 156.1

[0092] Note: C stands for biochemical pool, F / M C10 Indicates the organic load of the biochemical pool when the daily processing capacity is 10 mu, F / M C20 Indicates the organic load of the biochemical pool when the daily processing capacity is 20 mu, F / M C50 Indicates the organic load of the biochemical pool when the daily processing capacity is 50 mu, F / M C100 It indicates the organic load of the biochemical pond when the daily processing capacity is 100 mu.

[0093] Sampling time phase and point

[0094] The operation of the tailwater treatment project is divided into four periods: the initial stage, the early stage, the middle stage and the late stage. Among them, the initial stage belongs to the pretreatment stage, which lasts for 20 days, and the early stage, the middle stage and the late stage belong to the formal operation stage, which last for 15 days, 20 days and 10 days respectively. The sampling time is determined according to the operation period as September 10, 2021, September 19, 2021, October 1, 2021 and April 23, 2022. This study sampled the sites of each treatment stage in the shrimp tailwater treatment project, including the sewage collection well, the entrance and distal end of the sedimentation tank, the entrance and distal end of the ecological pool, and the 2nd, 4th, 6th, 8th, 10th, 12th, 14th and 16th channels of the biochemical pool. The sample number "CL" represents the different treatment pools from the inlet to the outlet stage. The first digit "1"-"4" after "CL" represents the sampling time of each treatment stage (initial, early, middle and late stage) respectively, and the second digit "1"-"13" after "CL" represents the sampling sites of different treatment pools respectively. The sampling sites of different treatment pools are distributed as follows: Figure 6As shown: 1 represents the water collection well, 2-3 represents the water inlet and outlet of the sedimentation tank, 4-5 represents the water inlet and outlet of the ecological pool, and 6-13 represents the waterways from the water inlet to the water outlet of the biochemical pool. Take CL1-1 as an example, which represents the sampling site of the water collection well in the early stage of the tailwater treatment project, and so on.

[0095] During the pretreatment stage, the composite microorganisms attached to the filler biofilm were sampled and analyzed, and the results were as follows: the microbial components and their percentages in the composite microorganisms were: Planctomyces 25%-35%, Proteobacteria 25%-35%, Pseudomonas 10%-20%, Nitrospira 8%-12%, Acidobacteria 3%-8%, Actinobacteria 3%-8%, Bacteroidetes 3%-5%, Chloroflexi 2%-3%, and Firmicutes 1%-2%.

[0096] Sampling methods and sample handling

[0097] According to the National Marine Monitoring Specifications, water samples are collected at a depth of 1-3 meters at the sampling point, and stored in sampling bags. The collected water samples are stored in a 4°C refrigerator as soon as possible, and all physical and chemical indicators of water quality are measured and recorded within 24-48 hours.

[0098] The environmental parameter determination method is shown in Table 7 below:

[0099] Table 7 Environmental parameters and measurement methods

[0100] Environmental parameters unit Determination method temperature ℃ Instrument on-site measurement pH — Instrument on-site measurement Electrical conductivity (EC) <![CDATA[ms·cm -1 ]]> Instrument on-site measurement Dissolved oxygen (DO) <![CDATA[mg·L -1 ]]> Instrument on-site measurement Nitrite Nitrogen <![CDATA[mg·L -1 ]]> Diazo-azo method Ammonia nitrogen <![CDATA[mg·L -1 ]]> Sodium hypobromite oxidation method Nitrate nitrogen <![CDATA[mg·L -1 ]]> Zinc-cadmium reduction method Suspended Matter <![CDATA[mg·L -1 ]]> Filtration constant weight method Chemical oxygen demand <![CDATA[mg·L -1 ]]> Alkaline potassium permanganate titration Total Phosphorus <![CDATA[mg·L -1 ]]> Ammonium molybdate spectrophotometry Active phosphate <![CDATA[mg·L -1 ]]> Ascorbic acid-reduced phosphomolybdenum blue method

[0101] The reagents required for water quality parameter determination are shown in Table 8 below:

[0102] Table 8 Environmental parameters and test reagents

[0103]

[0104] Comprehensive Water Quality Index Analysis (WQI)

[0105] WQI is a water quality analysis method that objectively evaluates water environment, water quality, water quality data and other parameters. Its advantage is that it can conduct qualitative and quantitative evaluation of water quality, and will not affect the overall water quality evaluation due to deviations in individual parameters. Water quality index parameters, standardized values ​​and relative weights are shown in Table 9 below. The comprehensive water quality index analysis (WQI) formula is as follows:

[0106]

[0107] Where:

[0108] n: number of environmental indicators

[0109] i: the i-th environmental indicator

[0110] Ci: Standardized value of the i-th environmental indicator

[0111] Pi: relative weight of the i-th indicator

[0112] The WQI result ranges from 0 to 100, with the higher the value, the better the water quality. Based on the score, the water quality can be divided into five levels: excellent (91 to 100), good (71 to 90), medium (51 to 70), fair (26 to 50), and poor (0 to 25).

[0113] Table 9 Water quality index parameters, standardized values ​​and relative weights

[0114]

[0115]

[0116] Inorganic nitrogen loading analysis

[0117] The inorganic nitrogen load calculation formula is as follows:

[0118]

[0119] Note: TINL stands for inorganic nitrogen load, in g·(m 3 d) -1 ;TIN 进水 Indicates the influent TIN concentration in mg·L -1 ; Q represents the water inlet flow rate, in m 3 ·d; HRT stands for hydraulic retention time, in d; V stands for volume, in m 3 .

[0120] Analysis of treatment effect in the initial operation of tailwater treatment project

[0121] On-site physical and chemical index results and analysis of tailwater treatment pool

[0122] The results of the on-site physical and chemical index measurements of the first sampling of the tailwater treatment pool are as follows: the salinity changes at various points in the treatment pool are relatively stable, and its fluctuation range is 2.8-3.3%, which is within the normal seawater salinity range; the temperature at various points in the treatment pool fluctuates within the normal range, and its fluctuation range is 32.7-35.0℃, with little difference; the pH of the tailwater at various points in the treatment pool is between 7.4-10.3, and except for CL1-1, the pH of the remaining treatment pools is between 9.6-10.3. According to the secondary marine aquaculture wastewater discharge standard, the pH is between 6.5-9.0, indicating that the tailwater at various points in the treatment pool is alkaline.

[0123] The conductivity of each point in the treatment pool is 39.9-47.7ms·cm -1Among them, CL1-1 is the highest. After being treated in the sedimentation tank, ecological pool and biochemical pool, the tail water shows a downward trend. The conductivity of the tail water is 40.7ms·cm when it is discharged from the biochemical pool. -1 .

[0124] There was no significant difference in dissolved oxygen at each point in the treatment pool. The content was at a low level, with CL1-1 being the lowest at 2.0 mg·L -1 , among which CL1-4 was the highest, at 5.5 mg·L -1 The dissolved oxygen at the end of the biochemical pool discharge is 3.3 mg·L -1 .

[0125] The redox potentials of various points in the treatment pool vary greatly, ranging from -344.0 to 139.6 mv, with CL1-6 being the lowest and CL1-11 being the highest.

[0126] Analysis of nitrogen treatment effect in tailwater treatment pool

[0127] The results of the first sampling of inorganic nitrogen in the tailwater treatment pool are shown in Table 10: NH 4 + -N concentration is 0.01-1.13 mg·L -1 Among them, the NH of the sewage well 4 + -N concentration is 0.89 mg·L -1 , sedimentation tank NH 4 + The average -N concentration was 1.13 mg·L -1 , Ecological Pool NH 4 + The average -N concentration was 0.13 mg·L -1 , Biochemical pool entrance NH 4 + -N concentration is 0.09 mg·L -1 , biochemical pool outlet NH 4 + -N concentration is 0.04 mg·L -1 , NH at each point of tailwater treatment pool 4 + -N concentration changes significantly. After treatment in the sedimentation tank, ecological pool, and biochemical pool, the tail water changes from 0.89 mg·L in the sewage collection well CL1-1 to -1 Reduced to 0.04 mg·L at the outlet of biochemical pool CL1-13 -1 , NH 4 + The -N removal rate was 95.51%.

[0128] Treatment pool points NO 2 --N concentration is 0.03-0.65mg·L -1 Among them, the NO 2 - -N concentration is 0.65 mg·L -1 , sedimentation tank NO 2 - The average -N concentration was 0.29 mg·L -1 , Ecological Pool NO 2 - The average -N concentration was 0.04 mg·L -1 , Biochemical pool entrance NO 2 - -N concentration is 0.35 mg·L -1 , Biochemical pool outlet NO 2 - -N concentration is 0.05 mg·L -1 , everyone click NO 2 - -N concentration changes significantly. After treatment in the sedimentation tank, ecological pool, and biochemical pool, the tail water changes from 0.65 mg·L in the sewage collection well CL1-1 to -1 Reduced to 0.05mg·L at the outlet of biochemical pool CL1-13 -1 ,NO 2 - The -N removal rate was 92.31%.

[0129] Treatment pool points NO 3 - -N concentration is 0.00-1.06 mg·L -1 Among them, CL1-2 is the highest and CL1-10 is the lowest. 3 - -N concentration is 0.52 mg·L -1 , sedimentation tank NO 3 - The average -N concentration was 1.02 mg·L -1 , Ecological Pool NO 3 - The average -N concentration was 0.09 mg·L -1 , Biochemical pool entrance NO 3 - -N concentration is 0.05 mg·L -1 , Biochemical pool outlet NO 3 - -N concentration is 0.01 mg·L -1 , tailwater treatment pool, everyone, NO 3 - -N concentration changes significantly. After treatment in the sedimentation tank, ecological pool, and biochemical pool, the tail water changes from 0.52 mg·L in the sewage collection well CL1-1 to-1 Reduced to 0.01mg·L at the outlet of biochemical pool CL1-13 -1 ,NO 3 - The -N removal rate was 98.08%.

[0130] The TIN concentration at each point in the treatment pool is 0.10-2.07 mg·L -1 Among them, CL1-2 was the highest and CL1-13 was the lowest. The TIN concentration of the sewage collection well was 2.07 mg·L -1 The average TIN concentration in the sedimentation tank was 2.44 mg·L -1 The average TIN concentration in the ecological pool was 0.26 mg·L -1 The TIN concentration at the biochemical pool entrance is 0.48 mg·L -1 , the TIN concentration at the biochemical pool outlet is 0.10 mg·L -1 The TIN concentration of each point in the tailwater treatment pool changes significantly. After being treated in the sedimentation tank, ecological pool, and biochemical pool, the tailwater changes from 2.07 mg·L in the sewage collection well CL1-1 to 2.07 mg·L in the sewage collection well CL1-1. -1 Reduced to 0.10 mg·L at the outlet of biochemical pool CL1-13 -1 , TIN removal rate is 95.17%. According to the first-level marine aquaculture wastewater discharge standard, inorganic nitrogen ≤ 1.00 mg·L -1 , the tail water reaches the first-level discharge standard after being treated in the treatment pool.

[0131] Table 10 Inorganic nitrogen index data of the first sampling of tailwater treatment pool

[0132]

[0133]

[0134] Analysis of phosphorus treatment effect in tailwater treatment pond

[0135] The results of the first sampling of phosphorus in the tailwater treatment pool are as follows: TP concentrations at various points in the treatment pool range from 0.00 to 3.91 mg·L -1 Among them, CL1-1 was the highest and CL1-7 was the lowest. The TP concentration in the sewage collection well was 3.91 mg·L -1 The average TP concentration in the sedimentation tank is 1.40 mg·L -1 The average TP concentration in the ecological pool was 0.27 mg·L -1 The TP concentration at the biochemical pool entrance is 0.06 mg·L -1 , the TP concentration at the biochemical pool outlet is 0.15 mg·L -1 The TP concentration of each point in the tailwater treatment pool changes significantly. After being treated in the sedimentation tank, ecological pool, and biochemical pool, the tailwater changes from 3.91 mg·L in the sewage collection well CL1-1 to 4.37 mg·L in the sewage collection well CL2-1.-1 Reduced to 0.15mg·L at the outlet of biochemical pool CL1-13 -1 ,TP removal efficiency was 96.16%.

[0136] Analysis of COD, turbidity and TSS treatment effects in tailwater treatment pool

[0137] The results of the first sampling of COD, turbidity and TSS in the tailwater treatment pool are as follows: COD concentrations at various points in the treatment pool range from 2.92 to 5.51 mg·L -1 Among them, CL1-1 is the highest and CL1-8 is the lowest. The COD concentration of the sewage collection well is 5.51 mg·L -1 The average COD concentration in the sedimentation tank is 3.78 mg·L -1 The average COD concentration in the ecological pool was 3.47 mg·L -1 The COD concentration at the biochemical pool inlet was 4.91 mg·L -1 The COD concentration at the biochemical pool outlet is 3.91 mg·L -1 There is no significant difference in COD concentration at each point in the treatment pool. According to the first-level marine aquaculture wastewater discharge standard, COD≤10mg·L -1 , the tail water reaches the first-level discharge standard.

[0138] The turbidity at each point in the treatment pool was between 99.28-110.45NTU, with CL1-6 being the highest and CL1-5 being the lowest. The turbidity of the sewage collection well was 110.35NTU, the average turbidity of the sedimentation tank was 102.98NTU, the average turbidity of the ecological pool was 99.73NTU, the turbidity at the inlet of the biochemical pool was 110.45NTU, and the turbidity at the outlet of the biochemical pool was 106.70NTU. The turbidity at each point in the treatment pool did not fluctuate much.

[0139] The TSS concentration at each point in the treatment pool is 2.17-31.00 mg·L -1 Among them, CL1-6 was the highest, CL1-3 and CL1-8 were the lowest, and the TSS concentration in the sewage collection well was 21.00 mg·L -1 The average TSS concentration in the sedimentation tank was 7.08 mg·L -1 The average TSS concentration in the ecological pool was 5.42 mg·L -1 , the TSS concentration at the biochemical pool inlet is 31.00 mg·L -1 The TSS concentration at the outlet of the biochemical pool was 14.92 mg·L -1 The TSS concentration at each point in the treatment pool fluctuates greatly. According to the first-level marine aquaculture wastewater discharge standard, TSS ≤ 40 mg·L -1 , the tail water reaches the first-level discharge standard.

[0140] The first sampling results show that the tailwater from all points in the tailwater treatment pool was alkaline at the beginning of its operation, which did not meet the discharge standard of marine aquaculture wastewater. 3 - -N treatment had the best effect, with a removal rate of 98.08%, and NH 4 + -N was second, with a removal rate of 95.51%, and NO 2 - The removal rate of -N was the lowest, at 92.31%, and the removal rate of total inorganic nitrogen was 95.17%. The total inorganic nitrogen content of the final tail water was 0.10 mg·L -1 <1.00mg·L -1 , reaching the first-level discharge standard for marine aquaculture effluent; in phosphorus pollution, the TP removal rate was 96.16%, and the treatment effect was good; in COD, turbidity, and TSS pollution, COD and turbidity did not change much at each point in the treatment pool, while TSS had large differences at each point in the biochemical pool. The reason may be that some channel vents in the biochemical pool were blocked, resulting in the massive growth of green algae and an increase in the content of suspended matter in the channel. However, in the marine aquaculture effluent discharge standard, COD and TSS both reached the first-level discharge standard.

[0141] Analysis of treatment effect in the early stage of tailwater treatment project operation

[0142] On-site physical and chemical index results and analysis of tailwater treatment pool

[0143] The results of the on-site physical and chemical index measurements of the second sampling of the tailwater treatment pool are as follows: the salinity changes at various points in the treatment pool are relatively stable, and its fluctuation range is 2.8-3.2, which is within the normal seawater salinity range; the temperature at various points in the treatment pool fluctuates within the normal range, and its fluctuation range is 31.3-34.4℃, with little difference; the pH at various points in the treatment pool is between 8.0-8.2, with no large difference. According to the first-level marine aquaculture wastewater discharge standard, the pH is between 7.0-8.5. The tailwater discharged this time meets the first-level discharge standard.

[0144] The conductivity of each point in the treatment pool is 41.7-47.7ms·cm -1 The dissolved oxygen in the treatment pool showed a slight upward trend, with CL2-1 being the highest, CL2-8 and CL2-9 being the lowest, and no significant difference between the treatment pools. The dissolved oxygen in the treatment pools showed a slight upward trend, with CL2-1 being the lowest at 2.6 mg·L -1 , among which CL2-11 had the highest value, which was 6.9 mg·L -1 The final dissolved oxygen in the effluent was 6.3 mg·L -1 The redox potentials of various points in the treatment pool vary greatly, ranging from -225.8 to 144.9 mv, with CL2-2 being the lowest and CL2-12 being the highest.

[0145] Analysis of nitrogen treatment effect in tailwater treatment pool

[0146] The results of the second sampling of inorganic nitrogen in the tailwater treatment pool are shown in Table 11: NH 4 + -N concentration is 0.08-0.82 mg·L -1 Among them, the NH of the sewage well 4 + -N concentration is 0.08 mg·L -1 , sedimentation tank NH 4 + The average -N concentration was 0.22 mg·L -1 , Ecological Pool NH 4 + The average -N concentration was 0.26 mg·L -1 , Biochemical pool entrance NH 4 + -N concentration is 0.27 mg·L -1 , biochemical pool outlet NH 4 + -N concentration is 0.21 mg·L -1 , NH at each point in the tailwater treatment pool 4 + -N concentration difference is not obvious. After the tail water is treated in the sedimentation tank, ecological pool and biochemical pool, NH 4 + -N concentration increased slightly.

[0147] Treatment pool points NO 2 - -N concentration is 0.17-1.35 mg·L -1 Among them, the NO 2 - -N concentration is 1.35 mg·L -1 , sedimentation tank NO 2 - The average -N concentration was 0.24 mg·L -1 , Ecological Pool NO 2 - The average -N concentration was 0.17 mg·L -1 , Biochemical pool entrance NO 2 - -N concentration is 0.67 mg·L -1 , Biochemical pool outlet NO 2 - -N concentration is 0.37 mg·L -1 , tailwater treatment pool, everyone, NO 2 --N concentration changes significantly. After treatment in the sedimentation tank, ecological pool, and biochemical pool, the tail water changes from 1.35 mg·L in the sewage collection well CL2-1 to -1 Reduced to 0.37 mg·L in biochemical pool CL2-13 -1 ,NO 2 - The -N removal rate was 72.59%.

[0148] Treatment pool points NO 3 - -N concentration is 0.00-2.61 mg·L -1 Among them, CL2-1 is the highest and CL2-2 is the lowest. 3 - -N concentration was 2.61 mg·L -1 , sedimentation tank NO 3 - The average -N concentration was 0.30 mg·L -1 , Ecological Pool NO 3 - The average -N concentration was 0.23 mg·L -1 , Biochemical pool entrance NO 3 - -N concentration is 0.38 mg·L -1 , Biochemical pool outlet NO 3 - -N concentration is 1.29 mg·L -1 , tailwater treatment pool, everyone, NO 3 - -N concentration varies greatly. After being treated in the sedimentation tank, ecological pool, and biochemical pool, the tailwater is 2.61 mg·L in the sewage collection well CL2-1. -1 Reduced to 1.29 mg·L in biochemical pool CL2-13 -1 ,NO 3 - The -N removal rate was 50.57%.

[0149] The TIN concentration at each point in the treatment pool is 0.49-4.04 mg·L -1 Among them, CL2-1 is the highest and CL2-2 is the lowest. The TIN concentration of the sewage collection well is 4.04 mg·L-1, and the average TIN concentration of the sedimentation tank is 0.75 mg·L -1 The average TIN concentration in the ecological pool was 0.69 mg·L -1 The TIN concentration at the biochemical pool entrance was 1.32 mg·L -1 The TIN concentration at the biochemical pool outlet was 1.96 mg·L -1The TIN concentrations at various points in the treatment pool vary greatly. After treatment in the sedimentation tank, ecological pool, and biochemical pool, the tailwater is 4.04 mg·L in the sewage collection well CL2-1. -1 Reduced to 1.96 mg·L in biochemical pool CL2-13 -1 , TIN removal rate is 51.49%. According to the secondary marine aquaculture wastewater discharge standard, inorganic nitrogen ≤ 2.00 mg·L -1 , the tail water reaches the secondary discharge standard after being treated at various points in the treatment pool.

[0150] Table 11 Inorganic nitrogen index data of the second sampling of the tailwater treatment pool

[0151]

[0152] Analysis of phosphorus treatment effect in tailwater treatment pond

[0153] The results of the second sampling of phosphorus in the tailwater treatment pool are as follows: TP concentrations at various points in the treatment pool range from 0.20 to 0.72 mg·L -1 The TP concentration in the sewage collection well was 0.72 mg·L -1 The average TP concentration in the sedimentation tank is 0.46 mg·L -1 The average TP concentration in the ecological pool was 0.28 mg·L -1 The TP concentration at the biochemical pool entrance is 0.21 mg·L -1 , the TP concentration at the biochemical pool outlet is 0.30 mg·L -1 The overall TP concentration has a downward trend. After being treated in the sedimentation tank, ecological pool, and biochemical pool, the tail water has changed from 0.72 mg·L in the sewage collection well CL2-1 to -1 Reduced to 0.30 mg·L in biochemical pool CL2-13 -1 ,TP removal efficiency is 58.33%.

[0154] Analysis of COD, turbidity and TSS treatment effects in tailwater treatment pool

[0155] The results of the second sampling of COD, turbidity and TSS in the tailwater treatment pool are as follows: COD concentrations at various points in the treatment pool ranged from 3.57 to 6.02 mg·L -1 Among them, CL2-1 was the highest and CL2-7 was the lowest. The COD concentration of the sewage collection well was 6.02 mg·L -1 The average COD concentration in the sedimentation tank is 5.20 mg·L -1 The average COD concentration in the ecological pool was 4.05 mg·L -1 The COD concentration at the biochemical pool entrance is 4.24 mg·L -1 The COD concentration at the biochemical pool outlet is 5.01 mg·L -1After treatment in sedimentation tanks, ecological pools, and biochemical pools, the COD concentration of the tail water has slightly decreased. According to the first-level marine aquaculture wastewater discharge standard, COD≤10mg·L -1 , the tail water reaches the first-level discharge standard.

[0156] The turbidity at each point in the treatment pool was between 96.25-151.10NTU, with CL2-1 being the highest and CL2-7 being the lowest. The turbidity of the sewage collection well was 151.10NTU, the average turbidity of the sedimentation tank was 119.70NTU, the average turbidity of the ecological pool was 104.80NTU, the turbidity at the inlet of the biochemical pool was 107.65NTU, and the turbidity at the outlet of the biochemical pool was 113.00NTU. After treatment in the sedimentation tank, the turbidity decreased slightly, and there was little difference in turbidity at each point between the ecological pool and the biochemical pool.

[0157] The TSS concentration at each point in the treatment pool is 1.50-31.00 mg·L -1 Among them, CL2-1 was the highest and CL2-7 was the lowest. The TSS concentration in the sewage collection well was 31.00 mg·L -1 The average TSS concentration in the sedimentation tank is 7.50 mg·L -1 The average TSS concentration in the ecological pool was 9.92 mg·L -1 The TSS concentration at the biochemical pool entrance was 14.17 mg·L -1 The TSS concentration at the outlet of the biochemical pool was 17.67 mg·L -1 The TSS concentration at each point in the treatment pool fluctuated greatly. After treatment in the sedimentation tank, the TSS content changed from 31.00 mg·L in CL2-1 to -1 Reduced to 8.50mg·L for CL2-2 -1 According to the first-level marine aquaculture wastewater discharge standard TSS≤40mg·L -1 , the tail water reaches the first-level discharge standard.

[0158] The second sampling results show that the pH of tailwater at each point in the treatment pool has improved compared with the results of the early stage of the tailwater treatment project, reaching the first-level discharge standard for marine aquaculture wastewater. 2 - The removal rate of -N was 72.59%, which was the best in this nitrogen pollution treatment. 3 - The -N removal rate was 50.57%, and the treatment effect was average; the total inorganic nitrogen removal rate was 51.49%, and the total inorganic nitrogen content of the final tail water was 1.96 mg·L -1 <2.00mg·L -1 , reaching the secondary discharge standard of marine aquaculture tail water; although the tail water discharge reaches the secondary discharge standard, the NH 4+ -N, NO 2 - -N, NO 3 - The concentration of -N increased, which may be due to the fact that the tail water in the sand filter was not discharged in time, resulting in the backflow of tail water and the concentration of NH 4 + -N, NO 2 - -N, NO 3 - -N concentration increased; in phosphorus pollution, TP removal rate was 58.33%; in COD, turbidity and TSS pollution, COD concentration decreased slightly, and the turbidity decreased slightly after treatment in the sedimentation tank. The turbidity differences at different points in the ecological pool and the biochemical pool were not large, and TSS had large differences at different points. In the marine aquaculture effluent discharge standards, COD and TSS both reached the first-level discharge standards.

[0159] Analysis of treatment effect of tailwater treatment project in the middle stage of operation

[0160] On-site physical and chemical index results and analysis of tailwater treatment pool

[0161] The results of the on-site physical and chemical index measurements of the third sampling of the tailwater treatment pool are as follows: the salinity changes at various points in the treatment pool are relatively stable, and its fluctuation range is 3.1-3.4, which is within the normal seawater salinity range; the temperature at various points in the treatment pool fluctuates within the normal range, and its fluctuation range is 31.1-33.4℃, with little difference; the pH of the tailwater at various points in the treatment pool is between 7.6-8.1, and there is no large fluctuation in the pH at each point. According to the first-level marine aquaculture wastewater discharge standard, the pH is between 7.0-8.5. The tailwater discharged this time meets the first-level discharge standard.

[0162] The conductivity of each point in the treatment pool is 44.2-48.8ms·cm -1 Among them, CL3-1 was the highest. After being treated in the sedimentation tank, ecological pool and biochemical pool, the tail water conductivity decreased slightly, and the final tail water conductivity was 44.6ms·cm -1 The dissolved oxygen concentrations at various points in the treatment pool were not very different, and all showed low levels, with CL3-3 being the lowest at 0.5 mg·L -1 , among which CL3-8 was the highest, at 5.5 mg·L -1 The final dissolved oxygen in the effluent was 2.6 mg·L -1 The redox potentials of various points in the treatment pool vary greatly, ranging from -239.8 to 141.0 mv, with CL3-2 being the lowest and CL3-13 being the highest.

[0163] Analysis of nitrogen treatment effect in tailwater treatment pool

[0164] The results of the third sampling of inorganic nitrogen in the tailwater treatment pool are shown in Table 12: NH 4 + -N concentration is 0.09-1.14 mg·L -1 Among them, CL3-7 is the highest and CL3-3 is the lowest. 4 + -N concentration is 0.54 mg·L -1 , sedimentation tank NH 4 + The average -N concentration was 0.16 mg·L -1 , Ecological Pool NH 4 + The average -N concentration was 0.31 mg·L -1 , Biochemical pool entrance NH 4 + -N concentration is 0.37 mg·L -1 , biochemical pool outlet NH 4 + -N concentration is 0.25 mg·L -1 After being treated in sedimentation tanks, ecological pools, and biochemical pools, the tail water is reduced from 0.54 mg·L of imported CL3-1 -1 Reduced to 0.25mg·L at the outlet of biochemical pool CL3-13 -1 ,NH 4 + The -N removal rate was 53.70%.

[0165] Treatment pool points NO 2 - -N concentration is 0.05-1.85 mg·L -1 Among them, CL3-2 is the lowest and CL3-1 is the highest. 2 - -N concentration is 1.85 mg·L -1 , sedimentation tank NO 2 - The average -N concentration was 0.06 mg·L -1 , Ecological Pool NO 2 - The average -N concentration was 0.11 mg·L -1 , Biochemical pool entrance NO 2 - -N concentration is 0.46 mg·L -1 , Biochemical pool outlet NO 2 - -N concentration is 0.21 mg·L -1 After being treated in the sedimentation tank, ecological pool and biochemical pool, the tail water is 1.85mg·L from the sewage collection well CL3-1. -1Reduced to 0.21 mg·L in biochemical pool CL3-13 -1 ,NO 2 - The -N removal rate was 88.65%.

[0166] Treatment pool points NO 3 - -N concentration is 0.00-0.58 mg·L -1 Among them, CL3-16 is the highest and CL3-8 is the lowest. 3 - -N concentration is 0.53 mg·L -1 , sedimentation tank NO 3 - The average -N concentration was 0.06 mg·L -1 , Ecological Pool NO 3 - The average -N concentration was 0.07 mg·L -1 , Biochemical pool entrance NO 3 - -N concentration is 0.25 mg·L -1 , Biochemical pool outlet NO 3 - -N concentration is 0.08 mg·L -1 After being treated in the sedimentation tank, ecological pool and biochemical pool, the tail water is 0.58mg·L from the sewage collection well CL3-1. -1 Reduced to 0.08 mg·L in biochemical pool CL2-13 -1 ,NO 3 - The -N removal rate was 86.21%.

[0167] The TIN concentration at each point in the treatment pool is 0.16-2.92 mg·L -1 Among them, CL3-1 was the highest and CL3-3 was the lowest. The TIN concentration of the sewage collection well was 2.92 mg·L -1 The average TIN concentration in the sedimentation tank was 0.29 mg·L -1 The average TIN concentration in the ecological pool was 0.48 mg·L -1 The TIN concentration at the biochemical pool entrance is 1.08 mg·L -1 The TIN concentration at the biochemical pool outlet was 0.54 mg·L -1 After being treated in the sedimentation tank, ecological pool and biochemical pool, the tail water is 2.92 mg·L from the sewage collection well CL3-1. -1 Reduced to 0.54 mg·L in biochemical pool CL3-13 -1 , TIN removal rate is 81.51%. According to the first-level marine aquaculture wastewater discharge standard, inorganic nitrogen ≤ 1.00 mg·L -1, the tail water at the outlet of the biochemical pool can meet the first-level discharge standard.

[0168] Table 12 Inorganic nitrogen index data of the third sampling of the tailwater treatment pool

[0169]

[0170]

[0171] Analysis of phosphorus treatment effect in tailwater treatment pond

[0172] The results of the third sampling of phosphorus in the tailwater treatment pool are as follows: TP concentrations at various points in the treatment pool range from 0.15 to 1.47 mg·L -1 The TP concentration in the sewage collection well was 0.75 mg·L -1 The average TP concentration in the sedimentation tank was 1.29 mg·L -1 The average TP concentration in the ecological pool was 0.56 mg·L -1 The TP concentration at the biochemical pool entrance is 0.59 mg·L -1 , the TP concentration at the biochemical pool outlet is 0.15 mg·L -1 After being treated in the sedimentation tank, ecological pool and biochemical pool, the tail water is 0.75mg·L from the sewage collection well CL3-1. -1 Reduced to 0.15mg·L in biochemical pool CL3-13 -1 ,TP removal rate is 80.00%.

[0173] 4.3.4 Analysis of COD, turbidity and TSS treatment effects in tailwater treatment pool

[0174] The results of the third sampling of COD, turbidity and TSS in the tailwater treatment pool are as follows: COD concentrations at various points in the treatment pool range from 3.83 to 6.37 mg·L -1 The COD concentration in the sewage collection well was 6.21 mg·L -1 The average COD concentration in the sedimentation tank is 6.20 mg·L -1 The average COD concentration in the ecological pool was 4.34 mg·L -1 The COD concentration at the biochemical pool inlet is 4.48 mg·L -1 The COD concentration at the biochemical pool outlet is 4.46 mg·L -1 The COD concentration of the tail water of the treatment pool has decreased slightly. According to the first-level marine aquaculture wastewater discharge standard, COD≤10mg·L -1 , the tail water reaches the first-level discharge standard.

[0175] The turbidity of each point in the treatment pool was between 98.11-153.40NTU, with CL3-3 being the highest and CL3-10 being the lowest. The turbidity of the sewage collection well was 113.40NTU, the average turbidity of the sedimentation tank was 144.60NTU, the average turbidity of the ecological pool was 109.40NTU, the turbidity at the inlet of the biochemical pool was 113.20NTU, and the turbidity at the outlet of the biochemical pool was 100.65NTU. Except for the sedimentation tank, the turbidity of other points in the treatment pool was not much different.

[0176] The TSS concentration at each point in the treatment pool is 1.17-64.50 mg·L -1 Among them, CL3-3 had the highest concentration, while CL3-8 and CL3-11 had the lowest concentration. The TSS concentration in the sewage collection well was 19.75 mg·L -1 The average TSS concentration in the sedimentation tank was 45.33 mg·L -1 The average TSS concentration in the ecological pool was 6.74 mg·L -1 The TSS concentration at the biochemical pool entrance was 5.48 mg·L -1 The TSS concentration at the outlet of the biochemical pool was 6.17 mg·L -1 The TSS concentration at each point in the treatment pool fluctuates greatly, among which the TSS concentration in the sedimentation tank is higher, while the TSS concentration in the ecological pool and biochemical pool remains at a lower level. According to the first-level marine aquaculture wastewater discharge standard, TSS≤40mg·L -1 , the tail water meets the first-level discharge standard.

[0177] The third sampling results show that the pH of tailwater at each point in the treatment pool during the operation of the tailwater treatment project has reached the first-level discharge standard for marine aquaculture wastewater; in nitrogen pollution, NH 4 + -N, NO 2 - -N, NO 3 - The removal rates of -N and TIN after treatment in the sedimentation tank, ecological tank, and biochemical tank were 53.70%, 86.65%, 86.21%, and 81.51%, respectively. The TIN concentration at the outlet of the biochemical tank was 0.54 mg·L -1 , reaching the first-level marine aquaculture wastewater discharge standard; in phosphorus pollution, the removal rate of TP after treatment in the sedimentation tank, ecological tank and biochemical tank was 80.00%; in COD, turbidity and TSS pollution, the COD concentration decreased slightly as a whole. Except for the turbidity of the sedimentation tank, the turbidity of other sites in the treatment tank was not much different. The concentration of TSS was higher in the sedimentation tank, while the TSS concentrations in the ecological tank and biochemical tank remained at a low level. In the marine aquaculture tailwater discharge standard, the final tailwater discharge of COD and TSS both reached the first-level discharge standard.

[0178] Analysis of treatment effect of tailwater treatment project in the later stage of operation

[0179] On-site physical and chemical index results and analysis of tailwater treatment pool

[0180] The results of on-site physical and chemical index measurements of the fourth sampling in the tailwater treatment pool are shown in the table below: the salinity changes at various points in the treatment pool are relatively stable, all at 3.5%; the temperature fluctuation range of various points in the treatment pool is 27.6-31.6℃, with little difference; the pH of the tailwater at various points in the treatment pool is between 7.2-8.0, and there is no large fluctuation in pH at various points. According to the first-level marine aquaculture wastewater discharge standard, the pH is between 7.0-8.5. The pH of the tailwater discharged this time meets the first-level discharge standard.

[0181] The conductivity of each point in the treatment pool is 46.5-47.5ms·cm -1 The conductivity of each point in the tailwater treatment pool did not fluctuate much. The dissolved oxygen concentrations at each point in the treatment pool did not differ much, and the contents were all at a low level, with CL4-2 being the lowest at 1.5 mg·L -1 , among which CL4-1 was the highest, at 5.2 mg·L -1 The final dissolved oxygen in the effluent was 5.2 mg·L -1 The redox potentials of various points in the treatment pool vary greatly, ranging from -301.5 to 165.6 mv, with CL4-2 being the lowest and CL4-8 being the highest.

[0182] Analysis of nitrogen treatment effect in tailwater treatment pool

[0183] The results of the fourth sampling of inorganic nitrogen in the tailwater treatment pool are shown in Table 13: NH 4 + -N concentration is 0.00-1.25mg·L -1 Among them, CL4-1 is the highest, and CL4-7, CL4-8, CL4-10, CL4-11, and CL4-12 are the lowest. 4 + -N concentration is 1.25 mg·L -1 , sedimentation tank NH 4 + The average -N concentration was 1.02 mg·L -1 , Ecological Pool NH 4 + The average -N concentration was 0.30 mg·L -1 , Biochemical pool entrance NH 4 + -N concentration is 0.13 mg·L -1 , biochemical pool outlet NH 4 + -N concentration is 0.13 mg·L -1 After being treated in sedimentation tanks, ecological pools, and biochemical pools, the tail water is reduced from 1.25 mg·L of imported CL4-1-1 Reduced to 0.13 mg·L at the outlet of biochemical pool CL4-13 -1 , NH 4 + The -N removal rate was 89.60%.

[0184] Treatment pool points NO 2 - -N concentration is 0.09-2.51 mg·L -1 Among them, CL4-1 is the highest, CL4-12 and CL4-13 are the lowest. 2 - -N concentration was 2.51 mg·L -1 , sedimentation tank NO 2 - The average -N concentration was 0.57 mg·L -1 , Ecological Pool NO 2 - The average -N concentration was 0.56 mg·L -1 , Biochemical pool entrance NO 2 - -N concentration was 2.21 mg·L -1 , Biochemical pool outlet NO 2 - -N concentration is 0.09 mg·L -1 After being treated in the sedimentation tank, ecological pool and biochemical pool, the tail water is 2.51 mg·L -1 Reduced to 0.09 mg·L in biochemical pool CL4-13 -1 ,NO 2 - The -N removal rate was 96.41%.

[0185] The TIN concentration at each point in the treatment pool is 1.94-23.46 mg·L -1 Among them, CL4-8 was the highest and CL4-3 was the lowest. The TIN concentration of the sewage collection well was 6.76 mg·L -1 The average TIN concentration in the sedimentation tank was 3.09 mg·L -1 The average TIN concentration in the ecological pool was 3.16 mg·L -1 The TIN concentration at the entrance of the biochemical pool was 16.53 mg·L -1 The TIN concentration at the biochemical pool outlet is 15.05 mg·L -1 . Due to NO 3 - The -N concentration increased, resulting in a corresponding increase in the TIN concentration.

[0186] Table 13 Inorganic nitrogen index data of the third sampling of the tailwater treatment pool

[0187]

[0188] Analysis of phosphorus treatment effect in tailwater treatment pond

[0189] The results of the fourth sampling of phosphorus in the tailwater treatment pool are as follows: TP concentrations at various points in the treatment pool range from 0.98 to 8.40 mg·L -1 Among them, CL4-1 was the highest and CL4-2 was the lowest. The TP concentration in the sewage collection well was 8.40 mg·L -1 The average TP concentration in the sedimentation tank was 4.16 mg·L -1 The average TP concentration in the ecological pool was 1.85 mg·L -1 The TP concentration at the biochemical pool entrance is 2.37 mg·L -1 The TP concentration at the biochemical pool outlet is 1.28 mg·L -1 After being treated in the sedimentation tank, ecological pool and biochemical pool, the tail water is 8.40 mg·L from the sewage collection well CL4-1. -1 Reduced to 1.28 mg·L in biochemical pool CL4-13 -1 , the TP removal rate was 84.76%.

[0190] The active phosphate concentration at each site in the treatment pool is 0.14-4.42 mg·L -1 Among them, CL4-1 was the highest and CL4-12 was the lowest. The active phosphate concentration in the sewage collection well was 4.42 mg·L -1 The average active phosphate concentration in the sedimentation tank was 2.72 mg·L -1 The average active phosphate concentration in the ecological pool was 0.58 mg·L -1 The active phosphate concentration at the biochemical pool entrance is 0.77 mg·L -1 The active phosphate concentration at the outlet of the biochemical pool is 0.23 mg·L -1 After being treated in the sedimentation tank, ecological pool and biochemical pool, the tail water is 4.42 mg·L from the sewage collection well CL4-1. -1 Reduced to 0.23 mg·L in biochemical pool CL4-13 -1 ,TP removal rate is 94.80%.

[0191] 4.4.4 Analysis of COD, turbidity and TSS treatment effects in tailwater treatment pool

[0192] The results of the fourth sampling of COD, turbidity and TSS in the tailwater treatment pool are as follows: COD concentrations at various points in the treatment pool range from 4.30 to 6.91 mg·L -1 Among them, CL4-1 was the highest and CL4-8 was the lowest. The COD concentration of the sewage collection well was 6.91 mg·L -1 The average COD concentration in the sedimentation tank is 5.86 mg·L-1 The average COD concentration in the ecological pool was 5.60 mg·L -1 The COD concentration at the biochemical pool inlet was 5.58 mg·L -1 The COD concentration at the biochemical pool outlet was 5.42 mg·L -1 The COD concentration of the tail water of the treatment pool has decreased slightly. According to the first-level marine aquaculture wastewater discharge standard, COD≤10mg·L -1 , the tail water meets the first-level discharge standard.

[0193] The turbidity at each point in the treatment pool was between 99.51 and 342.70 NTU, with CL4-1 being the highest and CL4-9 being the lowest. The turbidity of the sewage collection well was 342.70 NTU, the average turbidity of the sedimentation tank was 196.88 NTU, the average turbidity of the ecological pool was 128.20 NTU, the turbidity at the inlet of the biochemical pool was 127.90 NTU, and the turbidity at the outlet of the biochemical pool was 103.85 NTU. The turbidity dropped significantly after treatment in the sedimentation tank. There was little difference in the turbidity between the ecological pool and the biochemical pool CL4-6, and the turbidity changes of the biochemical pool CL4-7 to CL4-13 were relatively stable.

[0194] The TSS concentration at each point in the treatment pool is 11.00-175.50 mg·L -1 Among them, CL4-1 is the highest and CL4-4 is the lowest. The TSS concentration in the sewage collection well is 175.50 mg·L -1 The average TSS concentration in the sedimentation tank is 42.50 mg·L -1 The average TSS concentration in the ecological pool was 11.13 mg·L -1 The TSS concentration at the biochemical pool entrance is 34.50 mg·L -1 , the TSS concentration at the biochemical pool outlet is 32.00 mg·L -1 The TSS concentration at each point in the treatment pool fluctuated greatly. The TSS concentration in the sedimentation tank was the highest. After treatment in the sedimentation tank, the TSS concentration dropped significantly. After treatment in the sedimentation tank, ecological pool, and biochemical pool, the tail water was reduced from 175.50 mg·L in the sewage collection well CL4-1 to -1 Reduced to 32.00 mg·L in biochemical pool CL4-13 -1 , TSS removal rate is 81.77%. According to the first-level marine aquaculture wastewater discharge standard TSS ≤ 40 mg·L -1 , the tail water meets the first-level discharge standard.

[0195] The fourth sampling results show that the pH of tailwater at each point in the treatment pool after the operation of the tailwater treatment project has reached the first-level discharge standard of marine aquaculture wastewater; in nitrogen pollution, NH 4 + -N and NO 2 --N removal rates were 89.60% and 96.41% after treatment in sedimentation tank, ecological tank and biochemical tank, respectively, and the treatment effect was good; in phosphorus pollution, the removal rates of TP and active phosphate were 84.76% and 94.80% after treatment in sedimentation tank, ecological tank and biochemical tank, respectively; the COD concentration decreased slightly overall; the turbidity of the tail water was high when it entered the water, and the color was dark green. After treatment in the sedimentation tank, the color of the tail water was dark yellow, and the turbidity was greatly reduced. After treatment in the ecological tank and biochemical tank, the color of the tail water tended to be colorless, which was a significant improvement compared to the inlet water; TSS had the highest concentration in the sewage collection tank, followed by the sedimentation tank, and there was no obvious fluctuation in the TSS concentration in the ecological tank and biochemical tank. In the marine aquaculture tail water discharge standard, the final tail water discharge of COD and TSS both met the first-level discharge standard.

[0196] The tailwater treatment project in this study uses the "three-tank collaboration" of sedimentation tank, ecological tank and biochemical tank to treat the tailwater of shrimp farming in high-level ponds. The sedimentation tank in this study is a horizontal sedimentation tank. In the study, the sedimentation tank has a good effect on the initial treatment of tailwater. According to Wang Zhen, the tailwater purification facility adopts the "three dams and two tanks" model, including water dam, sedimentation tank, filtration dam, ecological purification tank and overflow dam, covering a total area of ​​27.6 acres. After the tailwater is treated in the sedimentation tank, the removal rates of TSS, TP and COD are 42.31%, 54.31% and 1.94% respectively. The sedimentation tank in this study occupies an area of ​​1.5 acres. In the later stage of the tailwater treatment project, after treatment in the sedimentation tank, the removal rates of TSS, TP and COD are 82.34%, 60.71% and 16.64% respectively. Compared with the "three dams and two tanks", the sedimentation tank in the tailwater treatment project in this study occupies less space and has a higher treatment effect, especially in terms of TSS treatment effect, the purification effect is obvious.

[0197] The ecological pond in this study used Gracilaria to treat tailwater. Gracilaria can not only be eaten and processed into agar, but also has a significant effect on absorbing pollutants in tailwater. The ecological pond in this study covers an area of ​​about 1.6 acres. In the later stage of the tailwater treatment project, after treatment in the ecological pond, DO increased significantly, with a growth rate of 158.64%, and NH 4 + -N, TP, and active phosphate removal rates were 78.26%, 42.42%, and 77.10%, respectively. According to Xu Cunfa, the ecological purification pond covers an area of ​​about 8 mu, and uses water hyacinth and water hyacinth to treat sewage. After the tail water is treated in the ecological purification pond, the DO concentration has dropped slightly, and NH 4 + -N, TP, and active phosphate removal rates were 15.00%, 76.92%, and 83.33%, respectively. Compared with the ecological purification pond, the scale of the ecological pond in this study is much smaller, but in terms of treatment effect, the improvement of DO is more obvious; 4 +-N, TP, and active phosphate treatment, due to the NH 4 + -N concentration is low, in NH 4 + -N treatment had no significant effect, but had significant effects on TP and active phosphate. The ecological pond in this study was inferior to the ecological purification pond in TP treatment, but had significant effects on NH 4 + -N and active phosphate treatments had good treatment effects.

[0198] The biochemical pool in this study uses the biofilm method, which absorbs and purifies tail water by using the biofilm formed by microorganisms on the filter material. The research shows that biofilm treatment of tail water has a good treatment effect. At present, there are few cases of using the biofilm method to treat tail water in practice, and most of them use laboratory small-scale bioreactor devices to simulate tail water treatment. According to Zhang Xiaoshan's research, the aerated biological pool designed by Zhang Xiaoshan is made of plexiglass and has a volume of only 2L. After 14 days of starting the aerated biological pool, COD and NH 4 + -N removal rates were 90.00% and 60.00% respectively. According to Lou Hongwei’s research, the aerated biological pool designed by Lou Hongwei is also made of plexiglass and has a volume of 2L. 4 + -N treatment has a higher removal effect, with removal rates of about 85.70% and 100% respectively, but the treatment capacity on the opposite side of TP is poor, only 20.00%. In the late operation of the biochemical pool of the tailwater treatment project in this study, when the biochemical pool is influent, NH 4 + -N and COD concentrations are low, and the treatment effect is not obvious. 2 - -N, active phosphate, the removal rates were 95.93% and 70.13% respectively, and the treatment effect was good. The laboratory simulation sewage treatment reactor was operated under set conditions without external interference, with strong controllability, and it was relatively easy to achieve good operating results. However, the biochemical pool of the tailwater treatment project in this study was large in scale and aimed at the treatment of actual shrimp tailwater on site. The influent water quality in the operating conditions was uncontrollable, and the treatment effect also had a certain volatility. Overall, the tailwater treatment project of this study was effective and had room for improvement and improvement.

[0199] The tailwater treatment project was compared as a whole. According to Shen Naifeng, the tailwater purification facility adopts the "three pools and two dams" model, including three pools of sedimentation tank, aeration tank and ecological pool and two filter dams. The facility construction is arranged as sedimentation tank → filter dam → aeration tank → filter dam → ecological pool, with a total area of ​​about 20 acres, mainly treating California bass aquaculture tailwater. After testing, after the tailwater was treated by the purification facility, the TP, TN, TSS and COD removal rates were 56.60%, 39.76%, 15.22% and 2.86% respectively. According to Zhang Qianyun, the tailwater purification facility also adopts the "three pools and two dams" model. The facility construction is arranged as sedimentation tank → filter dam → aeration tank → filter dam → biological purification pool, with a total area of ​​50 acres. After testing, after the tailwater was treated by the purification facility, NH 4 + -N, NO 2 - The removal rates of -N, TN, and TP were 92.86%, 66.67%, 64.42%, and 70.98%, respectively. The total area of ​​the tailwater treatment facility in this study is only about 6.5 mu. In the later stage of the tailwater treatment project, NH 4 + -N, NO 2 - -N, TP, TSS removal rates were 89.60%, 96.41%, 84.76%, 81.77% respectively. In comparison, the tailwater treatment project in this study occupies less land, about 3 / 10 or 1 / 10 of the area of ​​the "three pools and two dams" model, but the comprehensive comparison of tailwater treatment effects shows that the tailwater treatment project designed in this study is better than the tailwater purification model of "three pools and two dams".

[0200] Conclusion and engineering optimization suggestions

[0201] Analysis of the treatment effect of tailwater treatment projects based on environmental parameter concentrations, WQI and inorganic nitrogen load in tailwater

[0202] From the environmental parameter concentrations measured in the initial, early, middle and late stages of the tailwater treatment project, it can be seen that when the influent DO value is low, such as the DO value of the influent in the initial, early and middle stages is 3.2 mg·L -1 When the DO value of the effluent is kept at 5.0 mg·L, the treatment pool has the ability to improve the tail water and has an improvement effect. -1 about.

[0203] In nitrogen treatment, after four stages of operation, the entire tailwater treatment project has a 2 - -N treatment has the best effect, in the later stage of operation, NO 2 - -N removal rate can reach 96.41%. NH 4 +-N treatment effect was second, with a removal rate of 89.60%. It can be seen from the inorganic nitrogen load that in the later stage of the tailwater treatment project, the inorganic nitrogen loads of the sedimentation tank, ecological pool and biochemical pool were all at a high level. The biochemical pool operated under a high inorganic nitrogen load, which exceeded the inorganic nitrogen load tolerance range of the biochemical pool, resulting in a decrease in the treatment effect.

[0204] In terms of phosphorus treatment, the tailwater treatment project in this study also has a good treatment effect on TP. In the later stage of the tailwater treatment project, the TP removal rate reached 84.76%. In the treatment of COD, turbidity and TSS, since the COD values ​​of the influent at each period were not high, the COD removal capacity was not shown; in the treatment of turbidity and TSS, both the sedimentation tank and the ecological pond showed good treatment effects. In the later stage of the tailwater treatment project, the tailwater was dark green, turbid, and had obvious sediments; after treatment in the sedimentation tank, the tailwater was dark yellow, the turbidity was reduced, and the sediments were reduced; after treatment in the ecological pond, the tailwater was transparent, clear, and had no obvious sediments.

[0205] In summary, the tailwater treatment project has a great impact on NO 2 - -N, NH 4 + -N, TP, turbidity and TSS treatment have good treatment effects. Based on the overall treatment effect, the tailwater treatment project in this study can basically meet the requirements of shrimp tailwater treatment. In the early, early, middle and late stages of tailwater treatment operation, the WQI score of the tailwater effluent is maintained between 70 and 80. Although the WQI score of the treated water body in the late stage of operation is slightly lower than that in the early stage of operation, the WQI score of the influent in the late stage is lower. The influent load of the tailwater treatment facility in the late stage of operation is significantly higher than that in the early stage. The load can be reduced by reducing the water flow or increasing the hydraulic retention time to improve the treatment effect. In the face of the problem of high-level pond shrimp tailwater polluting the surrounding water environment, this study constructs a high-level pond shrimp tailwater treatment facility, uses sedimentation tanks, ecological ponds and biochemical ponds to treat tailwater, and then observes the overall operation of the tailwater treatment project through environmental parameter measurement and WQI analysis methods, analyzes the problems encountered in the operation of the tailwater treatment project, and proposes solutions and engineering optimization plans, which provide references for tailwater treatment and have great significance in promoting the development of tailwater treatment technology.

[0206] Suggestions for optimizing the operation of tailwater treatment projects

[0207] (1) The results of the second environmental parameter measurement show that there is a backflow phenomenon in the tail water. The reason is that the tail water is not discharged in time after treatment, and continues to accumulate in the sand filter tank, causing the water level to be too high and the tail water to flow back into the biochemical pool. To solve this problem, the tail water in the sand filter tank must be discharged in time to prevent tail water accumulation.

[0208] (2) According to the on-site conditions, when the embankment is lower than the biochemical pond, after the tailwater accumulates in the sand filter, it will overflow the embankment and flow back into the ecological pond when the water level is too high. To solve the backflow problem, the embankment can be raised to the same level as the biochemical pond to prevent the tailwater from flowing back into the ecological pond over the embankment.

[0209] (3) The fourth environmental parameter measurement results show that there is a lack of denitrification in the biochemical pool, NH 4 + -N and NO 2 - -N is converted to NO through nitrification 3 - -N can no longer be reduced to nitrogen and discharged, resulting in NO 3 - -N concentration increases. Interval ventilation can be used to keep a part of the biochemical pool aerated while the other part is stopped to increase denitrification and solve the problem of NO 3 - -The problem of increased N concentration.

[0210] 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 system for treating tail water from shrimp farming in high-level seawater ponds. It is characterized in that include: Sedimentation tanks, ecological pools and biochemical pools are connected in sequence. The sedimentation tank is provided with a filter screen for settling particles in the shrimp tail water of the high-level seawater pool; Aquatic plants are planted in the ecological pond to absorb some inorganic salts and organic matter in the shrimp tail water of the high-level seawater pond; A filler biofilm is provided in the biochemical pool, and the filler biofilm includes a filler and composite microorganisms attached to the filler; The microbial components in the composite microorganism and their percentage contents are: 25% to 35% of Planctomyces, 25% to 35% of Proteobacteria, 10% to 20% of Pseudomonas, 8% to 12% of Nitrospira, 3% to 8% of Acidobacteria, 3% to 8% of Actinobacteria, 3% to 5% of Bacteroidetes, 2% to 3% of Chloroflexi, and 1% to 2% of Firmicutes.

2. The system for treating tail water of shrimp culture in high-level seawater ponds according to claim 1, It is characterized in that The filler is one or more of high-density polyethylene, polyester and polyolefin.

3. The system for treating tail water of shrimp culture in high-level seawater ponds according to claim 2, It is characterized in that The initial loading amount of the composite microorganism is 15% to 25%.

4. A system for treating shrimp tail water in a high-level seawater pond according to any one of claims 1 to 3, It is characterized in that The composite microorganisms on the filler are obtained by the following pretreatment method: The tail water from shrimp farming in high-level seawater ponds is passed through sedimentation tanks, ecological ponds and biochemical ponds in sequence, with a pretreatment time of 18 to 22 days.

5. The system for treating tail water of shrimp cultured in high-level seawater ponds according to claim 4, It is characterized in that The total inorganic nitrogen load of the pretreatment sedimentation tank is 120-130 g·(m 3 d) -1 The total inorganic nitrogen load of the ecological pool is 135-145 g·(m 3 d) -1 The total inorganic nitrogen load of the biochemical pool is 200-210 g·(m 3 d) -1 .

6. A system for treating shrimp tail water in a high-level seawater pond according to any one of claims 1 to 5, It is characterized in that The aquatic plants are one or more of Gracilaria, Cattail, Reed and Lotus.

7. The system for treating tail water of shrimp cultured in high-level seawater ponds according to claim 6, It is characterized in that The planting density of the aquatic plants is 10 to 50 plants / m 2 .

8. The system for treating tail water of shrimp culture in high-level seawater ponds according to any one of claims 1 to 5, It is characterized in that The sedimentation tank includes a sludge zone at the bottom, and an inflow zone, a sedimentation zone and an outflow zone located above the sludge zone, wherein the inflow zone, the sedimentation zone and the outflow zone are distributed in sequence; the center position of the sludge zone is recessed downward relative to its end, and the depth of the center position of the sludge zone is 3-5m.

9. The system for treating tail water of shrimp culture in high-level seawater ponds according to any one of claims 1 to 5, It is characterized in that The porosity of the filter screen is 45% to 55%, and the pore size is 2 to 3 mm.

10. The system for treating tail water of shrimp culture in high-level seawater ponds according to any one of claims 1 to 5, It is characterized in that The biochemical pool comprises a plurality of treatment chambers which are connected end to end in sequence to form a serpentine channel, each treatment chamber is provided with a grid for preventing the filler biofilm from flowing out, and each treatment chamber is provided with a plurality of air pipes for providing air and causing the filler biofilm to churn.

11. A method for treating tail water from shrimp culture in high-level seawater ponds using the tail water treatment system for shrimp culture in high-level seawater ponds as described in any one of claims 1 to 10, It is characterized in that The following steps are involved: S1: The tail water of shrimp culture in high-level seawater pond is discharged into the sedimentation tank for sedimentation treatment to separate the insoluble particles; S2: The tail water after treatment in the sedimentation tank flows into the ecological pond, so that the aquatic plants in the ecological pond can absorb some inorganic salts and organic matter in the tail water; S3: The tail water treated by aquatic plants flows into the biochemical pool so that the complex microorganisms attached to the biofilm of the filler can absorb the remaining inorganic salts and organic matter in the tail water.

12. The method for treating tail water of shrimp culture in high-level seawater ponds according to claim 11, It is characterized in that The treatment method is divided into three stages: early operation stage, mid-operation stage and late operation stage. The early operation stage lasts for 14 to 16 days, the mid-operation stage lasts for 18 to 22 days and the late operation stage lasts for 8 to 12 days.

13. The method for treating tail water of shrimp cultured in high-level seawater ponds according to claim 12, It is characterized in that The total inorganic nitrogen load of the sedimentation tank in the early stage of operation is 245-250 g·(m 3 d) -1 The total inorganic nitrogen load of the ecological pool is 155-160 g·(m 3 d) -1 The total inorganic nitrogen load of the biochemical pool is 520-540 g·(m 3 d) -1 The inorganic nitrogen load of the sedimentation tank in the middle of the treatment system operation is 270-290 g·(m 3 d) -1 The inorganic nitrogen load of the ecological pond in the mid-term operation is 210-230 g·(m 3 ·d)-1, the inorganic nitrogen load of the biochemical pool in the middle of operation is 670~680g·(m 3 d) -1 The inorganic nitrogen load of the sedimentation tank in the later stage of the treatment system operation is 410-416 g·(m 3 d) -1 In the later period of operation, the inorganic nitrogen load of the ecological pool was 310-315 g·(m 3 d) -1 In the later stage of operation, the inorganic nitrogen load of the biochemical pool is 2700~2800g·(m 3 d) -1 .

14. The method for treating tail water of shrimp cultured in high-level seawater ponds according to claim 11, It is characterized in that The hydraulic retention time HRT of the tail water of shrimp culture in the high-level seawater pond in the sedimentation tank, the ecological pond and the biochemical pond B1 It is 250h / mu-350h / mu.

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