Method for synchronously removing heavy metals and pollutants in aquaculture wastewater by utilizing copper stress to drive granulation of bacteria-algae granular sludge

Abstract

The invention discloses a method for synchronously removing heavy metals and pollutants in aquaculture wastewater by utilizing copper stress to drive granulation of bacteria-algae granular sludge. The method specifically comprises the following steps: culturing and domesticating bacteria-algae granular sludge by adopting a sequencing batch reactor, and efficiently removing the high-concentration heavy metal Cu in the aquaculture tail water through long-term operation of the reactor under the illumination condition of simulated sunlight and low aeration intensity, and the average removal rate reaches 75% or above; meanwhile, organic matters and nutrient substances in the wastewater are effectively removed, and granulation of the bacteria-algae granular sludge is promoted. According to the method, the bacteria-algae granular sludge is used for treating the copper-containing low-carbon aquaculture wastewater for the first time, in the operation stage, the reactor performance is stable, the dirt removal capacity is not obviously influenced, under the exposure of Cu, the granulation process is accelerated, the sludge settling performance is far superior to that of a control group, and the method is a method for effectively removing heavy metal and pollutants in the aquaculture wastewater and has good application prospects. Good application prospects are realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of water treatment, and in particular relates to a method for synchronously removing heavy metals and pollutants in aquaculture wastewater by utilizing copper stress to drive bacteria and algae granular sludge granulation. Background Art

[0002] With the increasing development of aquaculture, the pollution problems it brings are also receiving more and more attention. In recent years, China has become the world's largest aquaculture country, with a total aquaculture output accounting for 2 / 3 of the world's output and an annual discharge of more than 300 million tons of tail water. Moreover, more than 80% of my country's aquaculture industry adopts pond farming, and excessive use of feed and drugs in the breeding process leads to a large amount of nutrients, heavy metals, drugs and other pollutants discharged into the water body. This intensive development model brings huge pollution to aquaculture water bodies. If this tail water is discharged directly without treatment, it will cause eutrophication of the surrounding water bodies and excessive concentration of heavy metals.

[0003] In recent years, there have been many reports on heavy metals in the environment. Various heavy metals have been detected in surface water, groundwater and sewage treatment plants. Heavy metals in aquaculture tailwater mainly come from vitamins in feed, pipeline corrosion and algaecide and antibacterial agents, such as iron (Fe), zinc (Zn), copper (Cu), cobalt (Co), manganese (Mn), nickel (Ni) and selenium (Se), of which zinc (Zn) and copper (Cu) account for more than 80%. A large number of studies have shown that heavy metals are easily accumulated in sediments in water bodies, but if released into water, they will accumulate along the food chain, which is potentially harmful to humans and the ecosystem. Therefore, it is necessary to use appropriate treatment processes to reduce the heavy metal content in aquaculture tailwater.

[0004] At present, the treatment process of freshwater aquaculture wastewater mainly adopts microbial method, which is more environmentally friendly and low-cost compared with other methods. These include the "three ponds and two dams" treatment mode, artificial wetland mode and pond internal enclosure mode, and many places mainly adopt the "three ponds and two dams" treatment mode, but this mode has problems such as unsatisfactory nitrogen and phosphorus removal effect, large land occupation, and greater seasonal influence, and it is difficult to effectively remove heavy metals. Therefore, more efficient and cost-effective methods for treating aquaculture wastewater are now sought.

[0005] In recent years, algal-bacterial aerobic granular sludge (ABGS) has attracted widespread attention due to its advantages such as more compact microbial structure, excellent sedimentation performance, ability to simultaneously achieve nitrification and denitrification processes, and strong resistance to high-concentration organic matter. Therefore, it is regarded as a strong candidate to replace traditional activated sludge. ABGS produces oxygen through the absorption of organic matter in water by microalgae and carbon dioxide released by bacteria, thereby reducing aeration intensity, improving the removal efficiency of nitrogen and phosphorus, and reducing aeration volume and operating costs of sewage treatment plants. In addition, the complex biological structure and multiple synergistic mechanisms of ABGS make it show good application prospects in the removal of heavy metal pollutants. At present, studies have found that ABGS can effectively remove pollutants in aquaculture wastewater (Ji, B.; Fan, S.; Liu, Y., A continuous-flow non-aerated microalgal-bacterial granular sludge process for aquaculture wastewater treatment under natural day-night conditions. Bioresour. Technol. 2022, 350, 126914.), but the COD content in its simulated wastewater is much higher than that in the actual wastewater, and the pollutants in the water are relatively single, without heavy metals, and have little reference value for practical applications. Therefore, our performance in the treatment of Cu-containing low-nutrient aquaculture wastewater by ABGS is still blank. This application adopts concentrations of pollutants and heavy metal Cu that are closer to real wastewater, and studies are carried out through actual wastewater to achieve the stability of the bacterial and algal granular sludge morphology and maintain high pollutant removal efficiency. Summary of the invention

[0006] The present invention provides a method for synchronously removing heavy metals and pollutants from aquaculture wastewater by driving the granulation of bacteria and algae granular sludge under copper stress. The present invention constructs a bacteria and algae granular sludge system, and finds that when the bacteria and algae granular sludge faces low concentrations of copper, the surface filamentous algae are inhibited, the granular sludge morphology is stable, the sedimentation performance is improved, and the granulation enters the next stage. At the same time, under the stress of Cu, a large number of denitrifying bacteria and bacterial communities related to the removal of organic matter are enriched, and the removal of organic matter and total nitrogen in low carbon-nitrogen ratio and low nutrient aquaculture wastewater is enhanced. When the SBR photoreactor is in operation and is inhibited by low nutrition and heavy metals, the constructed bacteria and algae granular sludge system has stronger resistance and degradation efficiency.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] The method for simultaneously removing heavy metals and pollutants from aquaculture wastewater by using copper stress to drive bacterial and algal granular sludge granulation comprises the following steps:

[0009] (1) Start-up of the reactor:

[0010] ① Cultivation of bacteria-algae granular sludge: The activated sludge from the aerobic tank of the sewage treatment plant is inoculated into the reactor for aerobic cultivation, and simulated domestic sewage and trace element dilution solution are added through the water inlet pipe; to meet the needs of algae growth, LED lamps are installed on the outside of the reactor and operate in an environment of simulated daylight, and the light-dark ratio of the system parameters is controlled to be 12h:12h; aeration is carried out through the aeration plate at the bottom of the reactor, and the aeration flow rate is adjusted; this operation is carried out until the algae and bacteria are entangled and combined to form bacteria-algae granular sludge with a regular elliptical shape.

[0011] ② Start the first stage: take out part of the bacteria and algae granular sludge obtained in ① and put it into the SBR reactor for cultivation. The influent is still simulated domestic sewage (with the same composition as the simulated domestic sewage in step 1). No Cu is added in the first stage, which lasts for about 15 days to allow the bacteria and algae granular sludge to adapt to the new reactor environment. The inlet and outlet water indicators are tested every day until the COD and TN removal rates are stable.

[0012] ③ Domestication of bacteria and algae granular sludge: When the COD conversion rate is above 90% and the average TN conversion rate reaches 65%, the artificial aquaculture tail water is introduced into the reactor, and heavy metals are added to the artificial synthetic waste water, and the process conditions are adjusted to enter the second stage of startup; the second stage mainly carries out the domestication stage of aquaculture tail water containing heavy metals by using bacteria and algae granular sludge to treat the aquaculture tail water, which lasts for 1 to 2 months; among them, the influent containing nitrogen source, carbon source, NaHCO3, KH2PO4 and heavy metal Cu enters the reactor and begins the domestication stage of bacteria and algae granular sludge. In this stage, the concentration of heavy metal Cu in the influent is 0.5 mg / L, and the mass concentration ratio of COD to nitrogen in the influent is 5, so as to achieve the purpose of microbial domestication, thereby completing the startup of the reactor; in order to ensure that the influent water quality does not change too much, the influent is replaced every day.

[0013] (2) After the reactor was started up, the average COD removal rate reached 85%, the TN removal rate was over 75%, the Cu removal rate was 80%, and the SVI5 was 34.11-41.28 ml / g. The bacteria-algae granular sludge system reached a stable operating state, thus establishing a stable process environment for removing heavy metals from aquaculture effluents based on bacteria-algae granular sludge.

[0014] (3) The wastewater to be treated is introduced as influent into a wastewater treatment system in stable operation to remove carbon, nitrogen and heavy metal pollutants in the wastewater to be treated.

[0015] Furthermore, the process operating conditions of the bacteria and algae granular sludge cultivation stage in step (1) are as follows: the reactor is operated in a cycle of 6 hours, and the inlet and outlet water are controlled by a peristaltic pump at the end of each cycle, the water inlet volume is 1.2L, the volume exchange rate is 50%, 4 hours of aerobic aeration, 2 hours of anaerobic standing, the aeration intensity is controlled at 0.8-1.0cm / s, the dissolved oxygen range is controlled at 2-8mg / L, the reaction temperature is 20-35°C, preferably 25-30°C, the inlet pH is 7.5-8.0, and the light and dark time is 11.5-12.5h:11.5-12.5h, preferably 12h:12h.

[0016] Furthermore, the domestic sewage in the bacterial and algal granular sludge cultivation stage in step (1) contains a nitrogen source, a carbon source, NaHCO3 and a phosphorus source, the nitrogen source is provided by NH4Cl, the carbon source is provided by NaAc, NaHCO3 is a phosphorus source, and KH2PO4 is used to buffer the reactor pH; the nitrogen source concentration in the simulated domestic sewage in step (1) is 30 mg / L, the carbon source concentration is 300 mg / L-COD, the inorganic phosphorus concentration is 5 mg / L; the NaHCO3 concentration is 250 mg / L; the pH of the artificial synthetic wastewater is preferably 7.5-8.0.

[0017] Furthermore, the process operating conditions for starting the first stage and starting the second stage in step (1) are as follows: the reactor operation cycle is 6 hours, the inlet and outlet water are controlled by a peristaltic pump at the end of each cycle, the water inlet volume is 1.2L, the volume exchange rate is 50%, 4 hours of aerobic aeration, 2 hours of anaerobic standing, the aeration intensity is 0.4cm / s, the reaction temperature is 20-35°C, the inlet pH is 7.5-8.0, and the light-dark time is 12h:12h.

[0018] Furthermore, the process operating conditions of steps (2) and (3) are as follows: the reactor operation cycle is 6 hours, the inlet and outlet water are controlled by a peristaltic pump at the end of each cycle, the inlet volume is 1.2 L, the volume exchange rate is 50%, 4 hours of aerobic aeration, 2 hours of anaerobic standing, the aeration intensity is 0.4 cm / s, the reaction temperature is 20-35°C, the inlet pH is 7.5-8.0, the light-dark time is 12h:12h, and the mass concentration ratio of COD to nitrogen in the inlet water is 5.

[0019] Furthermore, the artificially synthesized aquaculture wastewater in steps (1), (2) and (3) contains a nitrogen source, a carbon source, magnesium chloride, NaHCO3 and KH2PO4, wherein the nitrogen source is provided by NH4Cl and NaNO3, the carbon source is provided by NaAc, NaHCO3 is a phosphorus source, and KH2PO4 is used to buffer the pH of the reactor; the nitrogen sources in the artificially synthesized aquaculture tail water in step (1) are ammonia nitrogen and nitrate nitrogen, and their concentrations are 7.5-8.5 mg / L and 24.5-25.5 mg / L, preferably 8 mg / L and 25 mg / L, respectively; the initial concentration of the carbon source is 140-160 mg / L-COD, preferably 150 mg / L-COD; the initial concentration of inorganic phosphorus is 1.5-2.5 mg / L, preferably 2 mg / L; the concentration of NaHCO3 is 240-260 mg / L, preferably 250 mg / L; and the pH of the artificially synthesized wastewater is preferably 7.5-8.0.

[0020] Furthermore, the trace element dilution solution in steps (1), (2) and (3) is prepared by adding 1 mL of trace element stock solution to 1 L of tap water.

[0021] Furthermore, the stock solution composition and its content are ZnSO4 2.0-2.2 g / L, CaCl2 7.0-7.3 g / L, MnCl2·4H2O 2.0-3.0 g / L, (NH4)6Mo7O 24 ·4H2O 0.4~0.6g / L, CoCl2·6H2O 0.4~0.6g / L, FeSO4·7H2O 4~6g / L, MgCl2 9~11g / L. Preferably, the components and contents of the trace element stock solution are ZnSO4 2.2g / L, CaCl2 7.3g / L, MnCl2·4H2O 2.5g / L, (NH4)6Mo7O 24 ·4H2O 0.5g / L, CoCl2·6H2O 0.5g / L, FeSO4·7H2O 5g / L, MgCl2 10g / L.

[0022] Furthermore, the reactor described in step (1) is a sequencing batch reactor (SBR). It is made of plexiglass and consists of a water inlet and outlet system and a reaction zone. Water enters the bottom and air is introduced into the bottom aeration plate. It consists of a water inlet bucket, a water outlet bucket, a water inlet pump, a water outlet pump, an air pump, a water inlet pipe, a water outlet pipe, an aeration pipe, a water inlet valve, a water outlet valve and a reactor body. An LED lamp is installed on the outside of the reactor body.

[0023] Furthermore, the effective reaction volume of the reactor described in step (1) is 2.4-2.5 L, preferably 2.4 L, and the height-to-diameter ratio is 8.0-8.5:1; the artificial synthetic wastewater influent is preferably 1.2 L, the volume exchange rate is 50%, the influent enters through the bottom of the reactor at a certain flow rate through a peristaltic pump, and the effluent is discharged through an outlet pipe through a peristaltic pump.

[0024] Furthermore, the concentration of the bacteria-algae granular sludge in the reaction system of step (1) is 4.25 g / L, and the MLVSS / MLSS of the bacteria-algae granular sludge is 0.75; the pH of the reaction system is adjusted by sodium bicarbonate to 7.5-8.0.

[0025] Furthermore, the concentration of heavy metal Cu pollutants in the wastewater to be treated in step (3) is 0.5 mg / L.

[0026] Furthermore, the intensity of the light source is 5800 to 6100 lux; the intensity of the light source is 2800 to 3000 lux.

[0027] Principle of the present invention: The basic principle of the bacteria-algae symbiotic system for treating sewage is that organic pollutants in sewage are oxidized and decomposed by aerobic bacteria to produce ammonium salts, phosphates and CO2, etc.; while algae use ammonium salts, phosphates and CO2 as nutrients, sunlight as energy, photosynthesis through chlorophyll, synthesize algae's own cell substances, and release oxygen for bacteria to continue to oxidize organic matter. At the same time, the bacteria-algae granular sludge has a complex multi-layer structure, which is divided into anaerobic, anoxic and aerobic layers, and the surface is covered by algae. This multi-layer structure has a positive effect on the adsorption of heavy metals. The bacteria-algae granular sludge adsorbs heavy metals in the particles through electrostatic action. Most of the heavy metals in the particles are converted into more stable components through ion exchange and chemical precipitation, and a small part is absorbed and utilized by cells or complexed with organic matter to form a more stable form, thereby achieving effective removal of heavy metals. During this process, a large number of algae in the bacterial-algal granular sludge were inhibited or poisoned, but the sedimentation performance of ABGS was improved, which promoted the acceleration of the granulation process and greatly increased the enrichment of some denitrifying bacteria, making up for the lack of algae's pollution removal ability, thereby maintaining the stability of the ABGS system operation and achieving efficient removal of Cu-containing aquaculture wastewater.

[0028] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0029] The present invention adopts a bacterial algae granular sludge method, which can efficiently treat Cu-containing aquaculture wastewater under low aeration and low light conditions, solves the problem of high energy consumption of biological treatment methods, and realizes rapid granulation in aquaculture wastewater with a low carbon-nitrogen ratio, improves sludge sedimentation performance, and has a relatively stable morphology. The bacterial algae granular sludge realizes efficient removal of Cu through methods such as biological adsorption, ion exchange, chemical precipitation and biological transformation. For 0.5 mg / L Cu, the removal rate is more than 80% within a hydraulic retention time of 6 hours, reaching the heavy metal emission limit. Under the environmental stress of Cu and low carbon ratio, it can still maintain a COD removal rate of 90%, ammonia nitrogen removal rate of 100% and a TN removal rate of more than 75%. The enrichment ratio of some denitrifying bacteria reaches more than 40%, achieving a preliminary denitrification effect. It is a technical method for removing heavy metals in aquaculture tail water with good promotion and application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the structure of the SBR reactor used in the embodiment of the present invention.

[0031] Figure 2 This is a diagram showing the removal effect of Cu in artificial aquaculture wastewater by bacterial and algal granular sludge.

[0032] Figure 3 This is a diagram showing the removal effect of bacterial and algal granular sludge on Cu in actual aquaculture wastewater.

[0033] Figure 4 This is a diagram showing the COD removal effect of bacterial and algal granular sludge in Cu-containing and Cu-free aquatic wastewater.

[0034] Figure 5 This is a diagram showing the removal effect of TN in Cu-containing and Cu-free aquatic wastewater by bacterial and algal granular sludge.

[0035] Figure 6 This is a graph showing the changes in SVI5 in aquatic wastewater containing Cu and without Cu in bacterial and algal granular sludge.

[0036] Figure 7 Microscope and scanning electron microscope images of the particle morphology of the bacterial-algal granular sludge containing Cu and Cu-free aquatic wastewater (a and b are microscope images of R-Control and R-Cu, respectively; b and d are scanning electron microscope images of R-Control and R-Cu, respectively).

[0037] Figure 8 Schematic diagram of dead and live bacteria in bacterial-algal granular sludge with Cu and without Cu (R-Control on the left and R-Cu on the right). DETAILED DESCRIPTION

[0038] The present invention is further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0039] Example 1: Establishment of a stable process environment for treating aquaculture wastewater based on bacterial and algal granular sludge

[0040] (1) Start the reactor:

[0041] Cultivation of bacteria and algae granular sludge: The activated sludge from the aerobic pool of Guangzhou Datansha Sewage Treatment Plant was inoculated into a sequencing batch reactor for aerobic cultivation, and a dilution solution containing nitrogen source, carbon source, magnesium chloride, NaHCO3, KH2PO4 and trace elements was added through the water inlet pipe to simulate domestic sewage. The nitrogen source concentration in the simulated domestic sewage was 30mg / L, the carbon source concentration was 300mg / L-COD, the inorganic phosphorus concentration was 5mg / L, and the NaHCO3 concentration was 250mg / L. The process operating conditions in this stage are as follows: the hydraulic retention time of the reactor is 6 hours, the inlet and outlet water are controlled by a peristaltic pump at the end of each cycle, the inlet volume is 1.2L, the volume exchange rate is 50%, 4 hours of aerobic aeration, 2 hours of anaerobic standing, the aeration intensity is 0.8-1.2cm / s, the reaction temperature is 20-35℃, the inlet pH is 7.5-8.0, the light intensity is 6000lux, and the light-dark time is 12h:12h. It is operated in this way until the algae and bacteria are entangled and combined to form a regular elliptical bacterial-algae granular sludge.

[0042] Start the first stage: take out part of the cultured algae granular sludge and place it in the SBR reactor for cultivation. The influent is still simulated domestic sewage. No Cu is added in the first stage. The time is about 15 days, so that the algae granular sludge can adapt to the new reactor environment. The influent and effluent indicators are tested every day until the COD and TN removal rates are stable. The process operating conditions of this stage are: the hydraulic retention time of the reactor is 6h, the influent and effluent are controlled by a peristaltic pump at the end of each cycle, the influent volume is 1.2L, the volume exchange rate is 50%, 4h aerobic aeration, 2h anaerobic standing, aeration intensity of 0.4cm / s, reaction temperature of 20-35℃, influent pH of 7.5-8.0, light intensity of 3000lux, and light-dark time of 12h:12h.

[0043] Domestication of bacteria-algae granular sludge: Add part of the initial bacteria-algae granular sludge to the sequencing batch reactor to make the sludge concentration in the reactor 4.25g / L, and adjust the pH of the reaction system to 7.5-8.0. In order to meet the needs of microbial growth, trace element dilution solution is added to the inlet water, and 1.2L of artificial synthetic aquaculture wastewater is introduced into the reactor through the inlet pipe by a peristaltic pump for sludge domestication. At the same time, Cu is added to domesticate the microorganisms to adapt to the low-nutrient, low-carbon-nitrogen ratio environment and improve their microbial activity. The time is 1 to 2 months. The synthetic wastewater contains nitrogen source, carbon source, KH2PO4, and NaHCO3; the nitrogen source is provided by NaNO3 and NH4Cl, and the initial concentrations of nitrate nitrogen and ammonia nitrogen in the synthetic aquaculture wastewater are 25 and 8 mg / L respectively; the carbon source is provided by NaAC, and the COD concentration is about 150 mg / L; the KH2PO4 is a phosphorus source, and NaHCO3 is used as a pH buffer. The concentrations of inorganic phosphorus and NaHCO3 in the influent are 2 mg / L and 250 mg / L respectively, and the concentration of Cu is 0.5 mg / L. In order to ensure that the influent water quality does not change too much, the influent water is replaced every day. The process operating conditions of this stage are as follows: the hydraulic retention time of the reactor is 6h, the inlet and outlet water are controlled by a peristaltic pump at the end of each cycle, the inlet volume is 1.2L, the volume exchange rate is 50%, 4h aerobic aeration, 2h anaerobic standing, aeration intensity is 0.4cm / s, reaction temperature is 20-35℃, inlet pH is 7.5-8.0, light intensity is 3000lux, light-dark time is 12h:12h, and the mass concentration ratio of COD and nitrogen in the inlet water is 5.

[0044] (2) Establishment of stable operation of wastewater treatment system:

[0045] After the reactor is started, trace element dilution is introduced. To meet the needs of microbial growth, trace element dilution is added to the influent. 1.2L of artificial synthetic aquaculture wastewater is introduced into the reactor through the inlet pipe by a peristaltic pump. At the same time, heavy metal pollutants are added to the influent to make the concentration of heavy metal pollutants in the influent 0.5mg / L. The mass concentration ratio of COD and nitrogen in the influent is maintained at 5, and the nitrogen source, carbon source and heavy metal pollutants in the influent are removed; when the COD conversion rate is 90%, the TN conversion rate is above 75%, and the average removal rate of Cu is 80%, the enhanced process of removing heavy metal pollutants with algae granular sludge is completed, and then a stable process environment for removing heavy metals in water based on algae granular sludge is established. In order to ensure that the influent water quality does not change too much, the influent is replaced every day. The process operating conditions of this step are: the hydraulic retention time of the reactor is 6 hours, the inlet and outlet water are controlled by a peristaltic pump at the end of each cycle, the water inlet volume is 1.2L, the volume exchange rate is 50%, 4 hours of aerobic aeration, 2 hours of anaerobic standing, the aeration intensity is 0.4cm / s, the reaction temperature is 20-35°C, the inlet pH is 7.5-8.0, and the light-dark time is 12h:12h.

[0046] The photosequential batch reactor described in the embodiment is the most important processing unit in this process. The reactor body is made of plexiglass, with an inner diameter of 70 mm, a total height of 700 mm, and a total effective volume of 2.4 L. The inlet water is prepared by artificial simulation and replaced every day to ensure that the water quality does not change too much. It is transported to the reactor by a peristaltic pump to contact and react with the bacterial and algal granular sludge, and the effluent flows out from the outlet pipe.

[0047] Example 2: Effect of removing Cu from actual aquaculture wastewater by bacterial-algal granular sludge reactor and effect of Cu stress on promoting granulation

[0048] The stable process system for removing heavy metal pollutants from aquaculture wastewater based on bacteria and algae granular sludge in Example 1 was operated in stages for 150 days from establishment to stabilization. Among them, in the first stage (0-15d), the concentration of Cu in the influent is 0 mg / L, and the influent is artificial synthetic domestic sewage; in the second stage (16-100d), the concentration of Cu in the influent is increased to 0.5 mg / L, and the influent is artificial aquaculture wastewater; in the third stage (101-150d), the concentration of Cu in the influent is maintained at 0.5 mg / L, and the influent becomes actual aquaculture wastewater with a COD concentration of 80-150 mg / L, a TN concentration of 12-30 mg / L, and a TP concentration of less than 1 mg / L; other conditions remain unchanged. During the operation of the system, the process operating conditions are: the hydraulic retention time of the reactor is 6h, the inlet and outlet water are controlled by a peristaltic pump at the end of each cycle, the inlet volume is 1.2L, the volume exchange rate is 50%, 4h aerobic aeration, 2h anaerobic standing, aeration intensity is 0.4cm / s, reaction temperature is 20-35℃, inlet pH is 7.5-8.0, and the light and dark time is 12h:12h.

[0049] In the above reaction system, 10 mL of water was taken from the water bucket at the beginning of water inflow and 10 mL of water was taken from the water bucket at the end of water inflow. The water was filtered into a 10 mL sample tube using a 0.22 μm PTFE filter and stored in a 4 °C refrigerator. The Cu was detected and analyzed by UV spectrophotometer on the same day. 2+ Changes in content.

[0050] Figure 2 and Figure 3 The Cu of synthetic aquaculture wastewater and actual aquaculture wastewater are 2+ The removal effect diagram of bacteria-algae granular sludge in the bacteria-algae granular sludge photoreactor. As can be seen from the figure, the bacteria-algae granular sludge still has a good removal effect on Cu in the real environment, and the average removal rate reaches more than 75%.

[0051] Figure 4 and Figure 5These are the COD and TN removal effects of bacterial and algal granular sludge on aquaculture wastewater containing Cu and without Cu (R-Cu is aquaculture wastewater containing copper, and R-Control is aquaculture wastewater without Cu). Figure 4 and 5 As shown, exposure to Cu has almost no effect on the pollution removal ability of bacterial algae granular sludge, indicating that it has strong anti-toxicity and adaptability. In the simulated wastewater, the TN removal rate of bacterial algae granular sludge gradually increased from 55.77% to about 78% and remained stable, with a growth rate of 23%.

[0052] also, Figure 6 The graphs showing the changes in the settling performance of the two groups of bacterial and algal granular sludge are shown in Figure 2. Figure 7 Microscope and SEM morphology of algae granular sludge in aquatic wastewater containing Cu and without Cu. It can be clearly observed that the sedimentation performance of algae granular sludge gradually improved under the stress of Cu, while the group without Cu showed a slight sludge swelling phenomenon during the operation of the reactor, and SVI5 was even twice that of R-Cu. Figure 7 It can be found that there are obvious differences between the two groups of particles. The surface of R-Control particles is covered with a large number of green filamentous algae. Scanning electron microscopy shows that its surface is rough with a large number of spherical protrusions. In contrast, the surface of R-Cu particles is smoother and denser, and under the scanning electron microscope, it is more compact and has no algae coverage. This result shows that Cu exposure has a significant inhibitory effect on the growth of algae on the surface of bacterial and algal granular sludge, thereby inhibiting the sludge expansion phenomenon and improving the sedimentation performance. Figure 8 The ratio of live and dead bacteria in algae granular sludge is shown. The green part is live bacteria and the red part is dead bacteria. It can be seen that under the stress of Cu, although the ratio of live bacteria in algae granular sludge is slightly lower than that in R-Control, it still maintains this higher ratio of live and dead bacteria, indicating that it has a strong tolerance to Cu toxicity, which may also be the internal reason for the R-Cu group to maintain stable operation of the system and particle stability. Table 1 further analyzes the reaction mechanism of microorganisms under Cu poisoning through enzyme activity comparison. It is found that the higher ROS and lower SOD activity in R-Cu indicate that it is in a state of oxidative stress, and the higher LDH and lower ATP content also indicate that its cell metabolic function is damaged to a certain extent. However, combined with the stability of pollutant removal efficiency and sedimentation performance of algae granular sludge in the previous article, it can be analyzed that some microorganisms in R-Cu that are not resistant to Cu poisoning have reduced death, including surface filamentous microorganisms that affect particle stability and sedimentation performance, which explains the internal mechanism of further granulation of granular sludge under Cu stress. In summary, the use of bacteria-algae granular sludge system to treat Cu-containing low-carbon aquaculture wastewater has the ability to operate stably for a long time and resist metal poisoning and sludge swelling.

[0053] Table 1 shows the changes in microbial enzyme activity in bacterial-algal granular sludge containing Cu and without Cu

[0054]

[0055] Example 3

[0056] The main structures of the bacterial algae granular sludge photo-sequencing batch reactor in Example 1 and Example 2 are as follows: Figure 1 As shown, it includes an LED lamp 1, a water inlet bucket 2, a reactor body 3, an air pump 4, a water outlet bucket 5, a water outlet pipe 6, a water inlet pipe 7 and an air pipe 8; the reactor body 3 is provided with a water outlet and a water inlet, which are respectively connected to the water outlet bucket 5 and the water inlet bucket 2 through the water outlet pipe 6 and the water inlet pipe 7; the air pump 4 aerates the interior of the reactor body 3 through the air pipe 8; the water inlet pump is arranged on the water inlet pipe 7; the reactor body 3 and the water outlet pump are connected through the water outlet pipe 6, and the water outlet pump is arranged on the water outlet pipe 6; the water inlet pump and the water outlet pump are both peristaltic pumps; the outside of the reactor body 3 is provided with an LED lamp 1.

[0057] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for synchronously removing heavy metals and pollutants from aquaculture wastewater by using copper stress to drive bacterial and algal granular sludge granulation, characterized in that: The specific steps are: (1) Cultivation of bacteria-algae granular sludge: The activated sludge is inoculated into the SBR reactor for aerobic cultivation, and the culture is carried out using simulated domestic sewage and trace element dilution liquid, and the process is operated until bacteria-algae granular sludge with a regular elliptical shape is formed; the reactor is equipped with an LED lamp outside and operated in an environment simulating sunlight; aeration is performed through an aeration plate at the bottom of the reactor; (2) Acclimation of bacteria-algae granular sludge: Part of the bacteria-algae granular sludge obtained by culture in step (1) is taken out and placed in an SBR reactor. In the first stage, no Cu(II) is added, and the influent is still the simulated domestic sewage. The light intensity and aeration intensity are reduced to allow the bacteria-algae granular sludge to adapt to the new reactor environment. The operation time is 10-15 days. In the second stage, the influent is replaced with artificial synthetic aquaculture wastewater, and 0.4-0.6 mg / LCu(II) is added. The reactor is operated for 1-2 months to enable it to effectively adapt to the low carbon-nitrogen ratio environment under low light and aeration. At the same time, under the exposure of Cu(II), the growth of filamentous algae on the surface of the granular sludge is inhibited, the sedimentation of the granular sludge is improved, and the mud-water separation effect is enhanced, thereby improving the reactor treatment efficiency and further reducing the output of excess sludge.

2. The method according to claim 1, characterized in that: The process operating conditions of the SBR reactor in steps (1) and (2) are as follows: controlling the light-dark ratio to 11.5-12.5h:11.5-12.5h; controlling the temperature to 25-30°C, controlling the dissolved oxygen range to 2-8mg / L, maintaining the pH at 7.5-8.5, and the hydraulic retention time to be 6h as one cycle; aeration is performed through an aeration plate at the bottom of the reactor; wherein the aeration intensity in step (1) is 0.8-1.0cm / s; and the aeration intensity in step (2) is 0.3-0.4cm / s.

3. The method according to claim 1, characterized in that: In step (1), the activated sludge obtained is flocculent activated sludge in an aerobic tank of a sewage treatment plant.

4. The method according to claim 1, characterized in that: In step (1), the simulated domestic sewage contains a nitrogen source, a carbon source, NaHCO3 and 7.5-8.5; the nitrogen source is NH4Cl; the carbon source is NaAc; the phosphorus source is KH2PO4; NaHCO3 is used to buffer the reactor pH; the nitrogen source concentration in the simulated domestic sewage in step (1) is 30 mg / L, the carbon source concentration is 300 mg / L-COD, the phosphorus source concentration is 5 mg / L; and the NaHCO3 concentration is 250 mg / L.

5. The method according to claim 1, characterized in that: In step (2), the artificially synthesized aquaculture wastewater contains a nitrogen source, a carbon source, NaHCO3 and a phosphorus source; the nitrogen source is composed of NH4Cl and NaNO3; the carbon source is NaAc, and the phosphorus source is KH2PO4; NaHCO3 is used to buffer the pH of the reactor; the nitrogen sources in the artificially synthesized aquaculture tail water in step (2) are ammonia nitrogen and nitrate nitrogen, and their concentrations are 7.5-8.5 mg / L and 24.5-25.5 mg / L respectively, the initial concentration of the carbon source is 140-160 mg / L-COD, the initial concentration of inorganic phosphorus is 1.5-2.5 mg / L, and the concentration of NaHCO3 is 240-260 mg / L.

6. The method according to claim 1, characterized in that: The trace element diluent is prepared by adding 1 ml of trace element reserve solution to 1 L of tap water. The reserve solution composition and content are ZnSO4 2.0-2.2 g / L, CaCl2 7.0-7.3 g / L, MnCl2·4H2O 2.0-3.0 g / L, (NH4)6Mo7O 24 ·4H2O 0.4~0.6g / L, CoCl2·6H2O 0.4~0.6g / L, FeSO4·7H2O 4~6g / L, MgCl2 9~11g / L.

7. The method according to claim 1, characterized in that The main body of the SBR reactor is made of organic glass, has an effective volume of 2.4 to 2.5 L, and a height-to-diameter ratio of 8.0 to 8.5:

1.

8. The method according to claim 1, characterized in that In step (1), the light source intensity is 5800 to 6100 lux; in step (2), the light source intensity is 2800 to 3000 lux.

9. The method according to claim 1, characterized in that: In step (2), the SVI5 of the acclimated bacteria and algae granular sludge in the reaction system is 34.11-41.28 ml / g, and that of the control group is 54.05-79.12 ml / g.

10. The method according to any one of claims 1 to 9, characterized in that: The above method was used to treat aquaculture wastewater containing Cu. The average COD removal rate reached 85%, the TN removal rate was more than 75%, the average Cu removal rate was 80%, the sedimentation performance was gradually improved, and no sludge bulking occurred.

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