Method for simultaneously removing heavy metals and pollutants in aquaculture wastewater by driving granulation of bacteria-algae granular sludge with copper stress

Abstract

The application discloses a method for simultaneously removing heavy metals and pollutants in aquaculture wastewater by driving granulation of bacteria-algae granular sludge with copper stress. The specific method is as follows: a sequencing batch reactor is used to culture and domesticate bacteria-algae granular sludge; under the condition of simulated sunlight and low aeration intensity, high-concentration heavy metals Cu in tail water of aquaculture are efficiently removed, and the average removal rate is more than 75%; meanwhile, organic matters and nutrients in the wastewater are effectively removed, and the granulation of the bacteria-algae granular sludge is promoted. The application first uses the bacteria-algae granular sludge to treat low-carbon aquaculture wastewater containing copper, the reactor performance is stable during the operation stage, the pollutant removal capacity is not obviously affected, and under the exposure of Cu, the granulation process is accelerated, and the sludge settling performance is far superior to that of a control group. The application is a method for efficiently removing heavy metals and pollutants in aquaculture wastewater, and has a good application prospect.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, specifically relating to a method for simultaneously removing heavy metals and pollutants from aquaculture wastewater by using copper stress-driven granulation of bacterial and algal sludge. Background Technology

[0002] With the rapid development of aquaculture, the resulting pollution problems have attracted increasing attention. In recent years, China has become the world's largest aquaculture nation, accounting for two-thirds of global production, with annual wastewater discharge exceeding 300 million tons. Furthermore, over 80% of my country's aquaculture is conducted in ponds, and the excessive use of feed and medicines during the process leads to the discharge of large amounts of nutrients, heavy metals, and other pollutants into water bodies. This intensive development model causes significant pollution to aquaculture water bodies. If this wastewater is discharged directly without treatment, it will cause eutrophication and excessive heavy metal concentrations in surrounding water bodies.

[0003] In recent years, there have been numerous reports on heavy metals in the environment, with various heavy metals detected in surface water, groundwater, and wastewater treatment plants. Heavy metals in aquaculture wastewater mainly originate from vitamins in feed, pipe corrosion, and algaecides and antibacterial agents, including iron (Fe), zinc (Zn), copper (Cu), cobalt (Co), manganese (Mn), nickel (Ni), and selenium (Se), with zinc (Zn) and copper (Cu) accounting for over 80%. Numerous studies have shown that heavy metals tend to accumulate in sediments in water bodies, but when released into the water, they accumulate through the food chain, posing potential hazards to humans and ecosystems. Therefore, it is essential to utilize appropriate treatment processes to reduce the heavy metal content in aquaculture wastewater.

[0004] Currently, the main treatment process for freshwater aquaculture wastewater employs microbial methods, which are more environmentally friendly and cost-effective compared to other methods. These include the "three ponds and two dams" treatment model, constructed wetland models, and pond-based enclosed culture models. The "three ponds and two dams" model is predominantly used in many areas, but it suffers from unsatisfactory nitrogen and phosphorus removal, requires a large land area, is significantly affected by seasonal changes, and is also ineffective in removing heavy metals. Therefore, there is a growing demand for more efficient and cost-effective methods for treating aquaculture wastewater.

[0005] In recent years, algal-bacterial aerobic granular sludge (ABGS) has attracted widespread attention due to its more compact microbial structure, excellent settling performance, ability to simultaneously achieve nitrification and denitrification, and strong resistance to shock loads from high concentrations of organic matter. Therefore, it is considered a strong candidate to replace traditional activated sludge. ABGS generates oxygen by absorbing organic matter from the water and carbon dioxide released by bacteria, thereby reducing aeration intensity, increasing nitrogen and phosphorus removal efficiency, and reducing aeration volume and wastewater treatment plant operating costs. Furthermore, the complex biological structure and diverse synergistic mechanisms of ABGS demonstrate promising application prospects in the removal of heavy metal pollutants. Current research has found that ABGS can effectively remove pollutants from 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.). However, the COD content in the simulated wastewater is much higher than that in actual wastewater, and the pollutants in the water are relatively simple, with no heavy metals present, thus having limited reference value for practical applications. Therefore, our research on the performance of ABGS in treating Cu-containing low-nutrient aquaculture wastewater remains blank. This application uses pollutant and heavy metal Cu concentrations that are closer to those in real wastewater and conducts research using actual wastewater, achieving stable morphology of the bacterial and algal granular sludge and maintaining high pollutant removal efficiency. Summary of the Invention

[0006] This invention provides a method for simultaneously removing heavy metals and pollutants from aquaculture wastewater by using copper stress-driven granular sludge production of bacteria and algae. The invention constructs a granular sludge system of bacteria and algae and discovers that when faced with low concentrations of copper, surface filamentous algae are inhibited, the granular sludge morphology stabilizes, and settling performance is improved, allowing granulation to proceed to the next stage. Simultaneously, under Cu stress, a large number of denitrifying bacteria and bacteria related to organic matter removal are enriched, enhancing the removal of organic matter and total nitrogen from low C / N ratio, low-nutrient aquaculture wastewater. During the operation of the SBR photoreactor, when subjected to low nutrient and heavy metal inhibition, the constructed granular sludge system of bacteria and algae exhibits stronger resistance and degradation efficiency.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A method for simultaneously removing heavy metals and pollutants from aquaculture wastewater by granulating bacterial and algal sludge under copper stress includes the following steps:

[0009] (1) Reactor startup:

[0010] ① Cultivation of bacterial and algal granular sludge: Activated sludge from the aerobic tank of the sewage treatment plant is inoculated into the reactor for aerobic cultivation. Simulated domestic sewage and trace element dilution are added through the inlet pipe. To meet the growth requirements of algae, LED lamps are installed on the outside of the reactor, and the reactor is operated in a simulated sunlight environment. The light-dark ratio of the system parameter is controlled at 12h:12h. Aeration is carried out through the aeration disc at the bottom of the reactor, and the aeration flow rate is adjusted. The reactor is operated in this manner until the algae and bacteria intertwine and combine to form bacterial and algal granular sludge with a regular elliptical shape.

[0011] ② Start the first stage: Take a portion of the bacterial and algal 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. The time is about 15 days to allow the bacterial and algal granular sludge to adapt to the new reactor environment. The influent and effluent indicators are tested every day until the COD and TN removal rates reach stability.

[0012] ③ Acclimation of granular sludge: When the COD conversion rate is above 90% and the average TN conversion rate reaches 65%, artificially synthesized aquaculture wastewater is introduced into the reactor. Simultaneously, heavy metals are added to the artificially synthesized wastewater, and the process conditions are adjusted to enter the second stage of startup. The second stage mainly involves the acclimation of heavy metal-containing aquaculture wastewater to granular sludge, lasting 1-2 months. The acclimation stage begins when influent containing nitrogen, carbon, NaHCO3, KH2PO4, and heavy metal Cu enters the reactor. During 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, to achieve microbial acclimation and complete the reactor startup. To ensure minimal changes in influent quality, the influent is changed daily.

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

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

[0015] Further, the process operation conditions for the bacterial and algal granular sludge cultivation stage in step (1) are as follows: the reactor operates in a 6-hour cycle, and 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%, aerobic aeration is performed for 4 hours, and anaerobic settling is performed for 2 hours. 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℃ (preferably 25-30℃), the influent pH is 7.5-8.0, and the light-dark time is 11.5-12.5h:11.5-12.5h (preferably 12h:12h).

[0016] Furthermore, the domestic wastewater in the bacterial and algal granular sludge cultivation stage of step (1) contains nitrogen source, carbon source, NaHCO3 and phosphorus source. The nitrogen source is provided by NH4Cl, the carbon source is provided by NaAc, NaHCO3 is the phosphorus source, and KH2PO4 is used to buffer the pH of the reactor. The nitrogen source concentration in the simulated domestic wastewater in step (1) is 30 mg / L, the carbon source concentration is 300 mg / L-COD, the inorganic phosphorus concentration is 5 mg / L, and the NaHCO3 concentration is 250 mg / L. The pH of the artificially synthesized 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 operating cycle is 6h, the influent and effluent are controlled by peristaltic pump at the end of each cycle, the influent flow rate is 1.2L, the volume exchange rate is 50%, 4h of aerobic aeration, 2h of anaerobic settling, the aeration intensity is 0.4cm / s, the reaction temperature is 20~35℃, the influent pH is 7.5-8.0, and the light-dark time is 12h:12h.

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

[0019] Further, the artificially synthesized aquaculture wastewater in steps (1), (2), and (3) contains a nitrogen source, a carbon source, magnesium chloride, NaHCO3, and KH2PO4. The nitrogen source is provided by NH4Cl and NaNO3, the carbon source is provided by NaAc, NaHCO3 is the phosphorus source, and KH2PO4 is used to buffer the pH of the reactor. The nitrogen source in the artificially synthesized aquaculture tailwater in step (1) is ammonia nitrogen and nitrate nitrogen, with concentrations of 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. The pH of the artificially synthesized wastewater is preferably 7.5–8.0.

[0020] Furthermore, the trace element diluent 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 composition and content of the stock solution are as follows: 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 composition and content 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 an inlet and outlet water system, a reaction zone, and a bottom-inlet water system with air introduced through a bottom aeration disc. It comprises an inlet tank, an outlet tank, an inlet pump, an outlet pump, an air pump, an inlet pipe, an outlet pipe, an aeration pipe, an inlet valve, an outlet valve, and the reactor body. LED lights are installed on the outside of the reactor body.

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

[0024] Further, in the reaction system described in step (1), the concentration of bacterial and algal granular sludge is 4.25 g / L, and the MLVSS / MLSS of the bacterial and algal 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 pollutant in the wastewater to be treated in step (3) is 0.5 mg / L.

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

[0027] The principle of this invention: The basic principle of the bacterial-algae symbiotic system for wastewater treatment is as follows: Organic pollutants in wastewater are oxidized and decomposed by aerobic bacteria, producing ammonium salts, phosphates, and CO2; while algae utilize ammonium salts, phosphates, and CO2 as nutrients, and sunlight as energy, performing photosynthesis through chlorophyll to synthesize their own cellular material and release oxygen for the bacteria to continue oxidizing organic matter. Simultaneously, the bacterial-algae granular sludge has a complex multi-layered structure, consisting of anaerobic, anoxic, and aerobic layers, with the surface covered by algae. This multi-layered structure plays a positive role in the adsorption of heavy metals. The bacterial-algae granular sludge adsorbs heavy metals within the granules through electrostatic attraction. Within the granules, most heavy metals are converted into more stable components through ion exchange and chemical precipitation, while a small portion is absorbed and utilized by cells or complexed with organic matter into a more stable form, thereby achieving effective removal of heavy metals. During this process, a large number of algae in the granular sludge are inhibited or poisoned, but the settling performance of ABGS is improved, which promotes the acceleration of the granulation process and greatly increases the enrichment of some denitrifying bacteria, making up for the lack of decontamination capacity of algae, thereby maintaining the stable operation of the ABGS system 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] This invention employs a bacterial-algae granular sludge method, which can efficiently treat Cu-containing aquaculture wastewater under low aeration and low light conditions, solving the problem of high energy consumption in biological treatment methods. Furthermore, it achieves rapid granulation in aquaculture wastewater with a low C / N ratio, improving sludge settling performance and resulting in more stable morphology. The bacterial-algae granular sludge achieves highly efficient Cu removal through bio-adsorption, ion exchange, chemical precipitation, and biotransformation. For 0.5 mg / L Cu, the removal rate reaches over 80% within a hydraulic retention time of 6 hours, meeting heavy metal emission limits. Under Cu and low C / N ratio environmental stress, it still maintains a 90% COD removal rate, a 100% ammonia nitrogen removal rate, and a TN removal rate of over 75%. It also achieves a preliminary denitrification effect by enriching over 40% of some denitrifying bacteria. This method shows promising prospects for the removal of heavy metals from aquaculture wastewater. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the SBR reactor used in the embodiments of the present invention.

[0031] Figure 2 The image shows the effect of bacterial and algal granular sludge on the removal of Cu from synthetic aquaculture wastewater.

[0032] Figure 3 The diagram shows the effect of bacterial and algal granular sludge on the removal of Cu from actual aquaculture wastewater.

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

[0034] Figure 5 The graph shows the TN removal effect of Cu-containing and Cu-free aquatic wastewater from bacterial and algal granular sludge.

[0035] Figure 6 The graph shows the changes in SVI5 in Cu-containing and Cu-free aquatic wastewater from granular bacterial and algal sludge.

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

[0037] Figure 8 This is a schematic diagram of live and dead bacteria in granular sludge containing Cu and without Cu (R-Control on the left, R-Cu on the right). Detailed Implementation

[0038] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the implementation of the present invention is 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 granular sludge from bacteria and algae: Activated sludge from the aerobic tank of the Guangzhou Datansha Wastewater Treatment Plant was inoculated into a sequencing batch reactor (SBR) for aerobic cultivation. Simulated domestic wastewater was added through the inlet pipe, containing a nitrogen source, carbon source, magnesium chloride, NaHCO3, KH2PO4, and trace elements. The simulated domestic wastewater contained a nitrogen source concentration of 30 mg / L, a carbon source concentration of 300 mg / L-COD, an inorganic phosphorus concentration of 5 mg / L, and a NaHCO3 concentration of 250 mg / L. The operating conditions for this stage are as follows: the hydraulic retention time of the reactor is 6 hours; at the end of each cycle, the influent and effluent are controlled by a peristaltic pump; the influent flow rate is 1.2L; the volume exchange rate is 50%; 4 hours of aerobic aeration followed by 2 hours of anaerobic settling; the aeration intensity is 0.8-1.2 cm / s; the reaction temperature is 20-35℃; the influent pH is 7.5-8.0; the light intensity is 6000 lux; and the light-dark cycle is 12 hours:12 hours. This process continues until algae and bacteria intertwine and combine to form granular sludge with a regular elliptical shape.

[0042] The first stage of startup involves partially culturing the cultured algae and bacteria granular sludge in an SBR reactor. The influent remains simulated domestic sewage. No Cu is added during this first stage, which lasts approximately 15 days, allowing the sludge to adapt to the new reactor environment. Influent and effluent parameters are monitored daily until COD and TN removal rates stabilize. The operating conditions for this stage are as follows: reactor hydraulic retention time is 6 hours; at the end of each cycle, influent and effluent are controlled via a peristaltic pump; influent flow rate is 1.2 L; volume exchange rate is 50%; 4 hours of aerobic aeration followed by 2 hours of anaerobic settling; aeration intensity is 0.4 cm / s; reaction temperature is 20–35℃; influent pH is 7.5–8.0; light intensity is 3000 lux; and light-dark cycle is 12 hours:12 hours.

[0043] Acclimation of granular sludge: Initial granular sludge was added to the sequencing batch reactor (SBR) to achieve a sludge concentration of 4.25 g / L, and the pH of the reaction system was adjusted to 7.5-8.0. To meet the growth requirements of microorganisms, a trace element dilution was added to the influent. 1.2 L of synthetic aquaculture wastewater was then pumped into the reactor through the influent pipe using a peristaltic pump for sludge acclimation. Simultaneously, Cu was added to help the microorganisms adapt to a low-nutrient, low-carbon-nitrogen ratio environment and enhance their activity. This process took 1-2 months. The synthetic wastewater contains nitrogen, carbon, KH₂PO₄, and NaHCO₃. The nitrogen source is provided by NaNO₃ and NH₄Cl, with initial concentrations of nitrate nitrogen and ammonia nitrogen of 25 and 8 mg / L, respectively. The carbon source is provided by NaAC, with a COD concentration of approximately 150 mg / L. KH₂PO₄ serves as the phosphorus source, and NaHCO₃ acts 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. To ensure minimal changes in the influent quality, the influent is changed daily. The operating conditions for this stage are as follows: the hydraulic retention time of the reactor is 6 hours; at the end of each cycle, the influent and effluent are controlled by a peristaltic pump; the influent flow rate is 1.2 L; the volume exchange rate is 50%; 4 hours of aerobic aeration followed by 2 hours of anaerobic settling; the aeration intensity is 0.4 cm / s; the reaction temperature is 20–35 °C; the influent pH is 7.5–8.0; the light intensity is 3000 lux; the light-dark cycle is 12 h:12 h; and the mass concentration ratio of COD to nitrogen in the influent is 5.

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

[0045] After the reactor is started up, a trace element dilution solution is introduced. To meet the needs of microbial growth, the trace element dilution solution is added to the influent. 1.2L of synthetic aquaculture wastewater is then introduced into the reactor via a peristaltic pump through the influent pipe. Simultaneously, heavy metal pollutants are added to the influent to maintain a concentration of 0.5mg / L. The COD to nitrogen mass concentration ratio in the influent is maintained at 5, removing nitrogen sources, carbon sources, and heavy metal pollutants. When the COD conversion rate reaches 90%, the TN conversion rate exceeds 75%, and the average Cu removal rate reaches 80%, the enhanced process for removing heavy metal pollutants using bacterial and algal granular sludge is completed, thus establishing a stable process environment for heavy metal removal from water based on bacterial and algal granular sludge. To ensure minimal changes in influent water quality, the influent is changed daily. The operating conditions for this step are as follows: the hydraulic retention time of the reactor is 6 hours; at the end of each cycle, the influent and effluent are controlled by a peristaltic pump; the influent flow rate is 1.2L; the volume exchange rate is 50%; 4 hours of aerobic aeration followed by 2 hours of anaerobic settling; the aeration intensity is 0.4 cm / s; the reaction temperature is 20–35℃; the influent pH is 7.5–8.0; and the light-dark cycle is 12 hours:12 hours.

[0046] The photo-sequential batch reactor described in this 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 influent is prepared artificially and changed daily to ensure that the water quality does not change significantly. It is then transported to the reactor by a peristaltic pump to react with the bacterial and algae granular sludge. The effluent flows out from the effluent pipe.

[0047] Example 2: The effect of the bacterial-algae granular sludge reactor on the removal of Cu from actual aquaculture wastewater and the effect of Cu stress promoting granulation.

[0048] The stable process system for removing heavy metal pollutants from aquaculture wastewater based on bacterial and algal granular sludge in Example 1 was operated in stages from establishment to stability for 150 days. In the first stage (0-15d), the Cu concentration in the influent was 0 mg / L, and the influent was artificially synthesized domestic sewage. In the second stage (16-100d), the Cu concentration in the influent increased to 0.5 mg / L, and the influent was artificial aquaculture wastewater. In the third stage (101-150d), the Cu concentration in the influent remained at 0.5 mg / L, while the influent became actual aquaculture wastewater with a COD concentration of 80-150 mg / L, a TN concentration of 12-30 mg / L, and a TP concentration below 1 mg / L. Other conditions remained unchanged. During system operation, the process operating conditions were as follows: reactor hydraulic retention time was 6h, influent and effluent were controlled by peristaltic pumps at the end of each cycle, influent flow rate was 1.2L, volume exchange rate was 50%, aerobic aeration was 4h, anaerobic settling was 2h, aeration intensity was 0.4cm / s, reaction temperature was 20-35℃, influent pH was 7.5-8.0, and light-dark cycle was 12h:12h.

[0049] Within one hydraulic residence time, 10 mL of the influent was taken from the influent tank at the beginning of the reaction and 10 mL was taken from the effluent at the end. These samples were filtered through a 0.22 μm PTFE filter into 10 mL sample tubes, stored at 4°C, and the Cu content was analyzed using a UV spectrophotometer on the same day. 2+ Changes in content.

[0050] Figure 2 and Figure 3 These are Cu from artificially synthesized aquaculture wastewater and actual aquaculture wastewater, respectively. 2+ The figure shows the removal effect of granular sludge in the photoreactor. As can be seen from the figure, the granular sludge still has a good removal effect on Cu under real environment, with an average removal rate of over 75%.

[0051] Figure 4 and Figure 5These are graphs showing the removal effects of granular sludge on COD and TN in aquaculture wastewater containing and without Cu (R-Cu represents copper-containing aquaculture wastewater, and R-Control represents Cu-free aquaculture wastewater). Figure 4 and 5 As shown, Cu exposure has almost no effect on the sludge removal capacity of the granular sludge, indicating its strong resistance to toxicity and adaptability. In the simulated wastewater, the total nitrogen (TN) removal rate of the granular sludge gradually increased from 55.77% to approximately 78% and remained stable, representing a growth rate of 23%.

[0052] also, Figure 6 The graph shows the changes in the settling performance of the two groups of bacterial and algal granular sludge. Figure 7 Microscopic and SEM images of the particle morphology of Cu-containing and Cu-free granular sludge in aquatic wastewater are shown. It can be clearly observed that the settling performance of the granular sludge gradually improves under Cu stress, while the Cu-free group exhibits slight sludge bulking during reactor operation, with SVI5 even being twice that of R-Cu. Figure 7 It was observed that there were significant differences between the two groups of particles. The surface of the R-Control particles was covered with a large amount of green filamentous algae, and scanning electron microscopy showed that its surface was rough with numerous spherical protrusions. In contrast, the surface of the R-Cu particles was smoother and denser, and under scanning electron microscopy, it appeared more compact, with no algae coverage. This result indicates that Cu exposure has a significant inhibitory effect on the surface algae growth of bacterial and algal granular sludge, thereby inhibiting sludge bulking and improving settling performance. Figure 8 The table shows the ratio of live to dead bacteria in the algae-bacterial granular sludge. Green represents live bacteria, and red represents dead bacteria. It can be seen that under Cu stress, although the proportion of live bacteria in the algae-bacterial granular sludge is slightly lower than in R-Control, it still maintains a relatively high ratio of live to dead bacteria, indicating its strong tolerance to Cu toxicity. This may be the intrinsic reason why the R-Cu group maintains stable system operation and granular stability. Table 1 further analyzes the reaction mechanism of microorganisms under Cu toxicity through enzyme activity comparison. The higher ROS and lower SOD activities in R-Cu indicate that it is under oxidative stress, while the higher LDH and lower ATP content also indicate that its cellular metabolic function is somewhat impaired. However, combined with the stability of pollutant removal efficiency and settling performance of the algae-bacterial granular sludge mentioned earlier, it can be analyzed that some Cu-intolerant microorganisms in R-Cu die less, including surface filamentous microorganisms that affect granular stability and settling performance. This explains the intrinsic mechanism of further granulation of granular sludge under Cu stress. In summary, the bacterial and algae granular sludge system has the ability to treat Cu-containing low-carbon aquaculture wastewater with long-term stable operation and resistance to metal toxicity and sludge bulking.

[0053] Table 1 shows the changes in microbial enzyme activity in Cu-containing and Cu-free granular sludge.

[0054]

[0055] Example 3

[0056] The main structures of the photocatalytic batch reactors for granular sludge in Examples 1 and 2 are as follows: Figure 1 As shown, the reactor includes an LED light 1, a water inlet tank 2, a reactor body 3, an air pump 4, a water outlet tank 5, a water outlet pipe 6, a water inlet pipe 7, and an air pipe 8. The reactor body 3 has a water outlet and a water inlet, which are connected to the water outlet tank 5 and the water inlet tank 2 respectively through the water outlet pipe 6 and the water inlet pipe 7. The air pump 4 aerates the inside of the reactor body 3 through the air pipe 8. The water inlet pump is located 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 located on the water outlet pipe 6. Both the water inlet pump and the water outlet pump are peristaltic pumps. The LED light 1 is installed on the outside of the reactor body 3.

[0057] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for simultaneously removing heavy metals and pollutants from aquaculture wastewater by granulating bacterial and algal sludge using copper stress-driven processes, characterized in that... The specific steps are as follows: (1) Cultivation of bacterial and algal granular sludge: The activated sludge is inoculated into the SBR reactor for aerobic cultivation, using simulated domestic sewage and trace element dilution solution for cultivation, and running until bacterial and algal granular sludge with a regular elliptical shape is formed; the reactor is equipped with LED lamp tubes on the outside and operates in a simulated sunlight environment; aeration is carried out through the aeration disc at the bottom of the reactor. (2) Acclimation of bacterial and algal granular sludge: Take out part of the bacterial and algal granular sludge obtained in step (1) and place it in the SBR reactor. Start the first stage without adding Cu(II), and the influent is still the simulated domestic sewage. Reduce the light intensity and aeration intensity to allow the bacterial and algal granular sludge to adapt to the new reactor environment. The operation time is 10-15 days. In the second stage, replace the influent with artificial aquaculture wastewater and add 0.4-0.6 mg / L Cu(II). The reactor is run 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 settling property of the granular sludge is improved, the mud-water separation effect is enhanced, thereby improving the reactor treatment efficiency and further reducing the output of residual sludge. (3) The wastewater to be treated is introduced into a stable wastewater treatment system as influent to remove carbon, nitrogen and heavy metal pollutants from the wastewater to be treated, and to achieve efficient removal of Cu. The wastewater to be treated is Cu-containing aquaculture wastewater. In step (1), the light source intensity is 5800~6100 lux; in step (2), the light source intensity is 2800~3000 lux.

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: the light-dark ratio is controlled at 11.5~12.5 h:11.5~12.5 h; the temperature is controlled at 25-30℃, the dissolved oxygen range is controlled at 2-8 mg / L, the pH is maintained at 7.5-8.5, and the hydraulic retention time is 6 h as one cycle; aeration is carried out through the aeration disc at the bottom of the reactor; the aeration intensity in step (1) is 0.8-1.0 cm / s; and the aeration intensity in step (2) is 0.3-0.4 cm / s.

3. The method according to claim 1, characterized in that, In step (1), the activated sludge taken is flocculent activated sludge from the aerobic tank of the 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, and NaHCO3; the nitrogen source is NH4Cl; the carbon source is NaAc; the phosphorus source is KH2PO4; NaHCO3 is used to buffer the pH of the reactor; 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 in the artificially synthesized aquaculture wastewater in step (2) is ammonia nitrogen and nitrate nitrogen, with concentrations of 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. 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.

6. The method according to claim 1, characterized in that, The trace element diluent was prepared by adding 1 ml of trace element stock solution to 1 L of tap water. The stock solution contained ZnSO4 2.0~2.2 g / L, CaCl2 7.0~7.3 g / L, MnCl2·4H2O 2.0~3.0 g / L, and (NH4)6Mo7O 24 ·4H2O 0.4~0.6 g / L, CoCl2·6H2O 0.4~0.6 g / L, FeSO4·7H2O 4~6 g / L, MgCl29~11 g / L.

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

1.

8. The method according to claim 1, characterized in that, The SVI5 of the acclimated bacterial and algal granular sludge in the reaction system in step (2) is 34.11-41.28 ml / g.

9. The method according to any one of claims 1-8, characterized in that, Using the above method to treat aquaculture wastewater containing Cu, the average COD removal rate reached 85%, the TN removal rate was over 75%, the average Cu removal rate was 80%, the settling performance gradually improved, and no sludge bulking occurred.

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