A low-energy comprehensive wastewater toxicity reduction method

Abstract

The application discloses a low-energy-consumption comprehensive wastewater toxicity reduction method, which comprises the following steps: (1) selecting a suitable electrode according to the B / C ratio of wastewater; (2) constructing a microbial electrochemical system; (3) enriching and culturing an electroactive biofilm; and (4) driving the microbial electrochemical system to treat industrial wastewater in an intermittent polarization mode. The application realizes the reduction of industrial wastewater toxicity under low energy consumption conditions, has the advantages of low energy consumption, simple operation and the like, and has practical significance for realizing standard and safe discharge of industrial wastewater.

Description

Technical Field

[0001] The present invention relates to the field of wastewater treatment, and in particular to a method for reducing the comprehensive toxicity of wastewater with low energy consumption. Background Art

[0002] At present, industrial parks with relatively concentrated industries collect and treat wastewater in a centralized manner. There are many types of pollutants in the wastewater, including many known and so far unknown toxic organic pollutants. Despite primary and secondary treatment, various refractory organic compounds still exist in the wastewater, mainly (>90%) dissolved organic matter, which will cause serious harm to human health and the ecological environment once they enter the water body. In addition, studies have shown that there is no obvious direct correlation between the reduction of toxicity of organic pollutants in wastewater and the reduction of total organic carbon (TOC), that is, the reduction of TOC cannot represent the elimination of the toxicity of organic pollutants in wastewater. However, traditional wastewater treatment methods for removing organic pollutants only aim to control general pollution parameters such as COD and TOC, which cannot meet the growing safety requirements of aquatic ecosystems. Therefore, effective deep treatment is needed to further purify the wastewater and reduce its toxicity to ensure the safety of wastewater discharge from sewage treatment plants.

[0003] Traditional physical and chemical wastewater treatment technologies (such as ozone oxidation) have been applied to remove refractory pollutants, but they also have some major disadvantages, such as high material cost, high energy consumption and the production of toxic byproducts, which can lead to a decrease in the total organic carbon content of the effluent but an increase in the toxicity of organic matter. In recent years, by combining biodegradation with electrochemical processes in a single device, microbial electrochemical systems have been proven to be a low-energy, sustainable technology suitable for treating a variety of wastewater types. However, the practical application of microbial electrochemical systems in treating industrial wastewater is greatly limited by the slow biodegradation rate of refractory pollutants. Summary of the Invention

[0004] Purpose of the invention: The present invention aims to provide a low-energy method for reducing the comprehensive toxicity of wastewater to improve wastewater treatment efficiency.

[0005] Technical solution: The low-energy wastewater comprehensive toxicity reduction method of the present invention comprises the following steps:

[0006] (1) Select appropriate electrodes according to the wastewater B / C ratio

[0007] When the B / C ratio of industrial wastewater is ≥0.25, graphite rod electrodes are used for treatment; when the B / C ratio of industrial wastewater is 0.1≤B / C<0.25, biochar / molybdenum disulfide (Bio-C / MoS2) modified graphite rod electrodes are used for treatment;

[0008] (2) Construction of microbial electrochemical system

[0009] A single-chamber microbial electrochemical system is constructed by using a graphite rod electrode or a biochar / molybdenum disulfide modified graphite rod electrode as a working electrode;

[0010] (3) Enrichment culture of electroactive biofilm

[0011] A mixed culture solution containing sediment, industrial wastewater, phosphate buffer and carbon source is added to the system, and the enrichment culture of the electroactive biofilm is carried out by chronoamperometry, and the culture solution is replaced regularly until the biofilm matures;

[0012] (4) Intermittent polarization driving system operation

[0013] After the biofilm is hung, only the industrial wastewater to be treated needs to be injected into the system, and an external voltage is applied to the working electrode, and an open circuit and a closed circuit intermittent polarization mode is used to drive the system to operate, so as to realize the toxicity reduction of the industrial wastewater.

[0014] The B / C is 5-day biochemical oxygen demand / chemical oxygen demand, and the method provides a corresponding system construction scheme for the treatment of industrial wastewater with different B / C ratios.

[0015] The biochar / molybdenum disulfide modified graphite rod electrode method is to load biochar / molybdenum disulfide on the surface of a stone mill rod for modification.

[0016] Preferably, in step (1), the preparation method of the biochar / molybdenum disulfide (Bio-C / MoS2) modified graphite rod electrode is to uniformly disperse biochar / molybdenum disulfide in a buffer solution with pH=5.5-6.5, and to modify the graphite rod electrode by cyclic voltammetry.

[0017] Preferably, the concentration of the Bio-C / MoS2 is 0.5-1.0 g / L.

[0018] Preferably, the parameters of the cyclic voltammetry for modifying the graphite rod electrode are that the scanning rate is 50-100 mV / s, the scanning potential range is controlled to be-0.8 V-1.0 V vs. Ag / AgCl reference electrode, and the scanning number is 30-60 times.

[0019] Preferably, the biochar raw material in the biochar / molybdenum disulfide is date pit.

[0020] The preparation method of the Bio-C / MoS2 is as follows: after peeling and slicing, date pits are ground by a grinder, and then calcined in a nitrogen atmosphere to obtain an intermediate product; the intermediate product is added into a KOH solution for reaction, and the powder is calcined at high temperature in a nitrogen atmosphere after filtration; the obtained product is washed to neutral to obtain a porous biochar material; ammonium heptamolybdate, thiourea and the prepared biochar are poured into a date peel extract solution, stirred uniformly, and then poured into a high-pressure reaction kettle for hydrothermal reaction for 12 hours, and then naturally cooled, centrifuged and washed to obtain a Bio-C / MoS2 material.

[0021] Preferably, the buffer solution is a citrate buffer solution, and the concentration is 0.01-0.1 M.

[0022] In step (2), the single-chamber microbial electrochemical system comprises a reactor, a counter electrode, a reference electrode, a working electrode, an electrochemical workstation and wires, and a structural schematic diagram is shown in Figure 1 The counter electrode, the reference electrode and the working electrode are all vertically inserted into the reactor and connected with the electrochemical workstation through corresponding wires.

[0023] In step (3), the culture conditions are as follows: the volume ratio of the mixed culture solution of the sludge, the industrial wastewater and the phosphate buffer solution is 1-2:6-8:1-2, sodium acetate is selected as the carbon source, and the concentration is 0.5-1 g / L; when the output current value of single culture is ≤10 -5 A, the culture solution is replaced, and when the output current reaches the maximum and is stable, it indicates that the biofilm is mature.

[0024] Preferably, the single culture time is 2-4 days, and the total culture time is 25-35 days.

[0025] Preferably, in step (4), the intermittent polarization mode of open circuit and closed circuit is as follows: open circuit for 6-12 hours, and closed circuit for 6-12 hours.

[0026] Preferably, in step (4), the treatment time of the industrial wastewater is 24-48 hours.

[0027] Preferably, in step (4), the external voltage value is 0-0.6 V relative to the Ag / AgCl reference electrode.

[0028] Invention mechanism:

[0029] The role of the biochar / molybdenum disulfide (Bio-C / MoS2) in the technical solution is mainly to store and release electrons. In the technical solution, the operation of the microbial electrochemical system adopts an intermittent polarization mode. During the open circuit period, the electrons generated by the electroactive microorganisms during the oxidation of organic matter can be stored in the Bio-C / MoS2. During the closed circuit period, these electrons are released into the circuit to form a larger output current (density), thereby greatly stimulating the metabolic capacity of the electrode microorganisms. In addition, in combination with the intermittent polarization operation mode, the Bio-C / MoS2 can also induce the expression of more redox electron carriers by the electroactive microorganisms, further enhancing the electron flux in the microbial cells and the extracellular electron transfer rate. This not only improves the electron transfer efficiency between the electroactive microorganisms and the electrode, but also enables the electroactive microorganisms to more effectively utilize pollutants as electron donors, thereby promoting the transformation and degradation of pollutants and achieving the reduction of the toxicity of industrial wastewater.

[0030] Advantages: Compared with the prior art, the present application has the following significant advantages: (1) The present method provides a corresponding feasible treatment scheme for industrial wastewater with different biodegradability B / C ratios; (2) For 0.1≤B / C<0.25, the Bio-C / MoS2 modified graphite rod is used as the working electrode and combined with the intermittent action mechanism to improve the wastewater treatment efficiency, greatly shorten the wastewater treatment time, and further reduce the energy consumption per unit of wastewater treatment. Under low energy consumption conditions, the reduction of the toxicity of refractory industrial wastewater is successfully achieved, which breaks through the problem of the existing high-energy consumption process that only reduces the organic carbon content of the effluent but increases the toxicity of the organic matter. This has practical significance for realizing the standard and safe discharge of industrial wastewater; (3) The biochar in Bio-C / MoS2 uses coconut date pits as raw materials, making its charging and discharging capacity more optimal; (4) The intermittent polarization driving mode not only achieves the effect of utilizing external energy input to enhance pollutant degradation, but also further saves system energy consumption by reducing the power supply time. The present method has low energy consumption requirements, simple treatment process and operation method, and good application prospects, and will also achieve good social and environmental benefits. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a single-chamber microbial electrochemical system structure schematic diagram;

[0032] Figure 2 is a time-current graph of Example 1, Comparative Example 1 and Comparative Example 2;

[0033] Figure 3 is a graph of effluent TOC concentration and removal rate of Example 1, Comparative Example 1 and Comparative Example 2;

[0034] Figure 4 is an effluent toxicity graph of Example 1, Comparative Example 1 and Comparative Example 2;

[0035] Figure 5 Time-current graph for Example 2 and Comparative Example 3;

[0036] Figure 6 Effluent TOC concentration and removal rate graph for Example 2, Comparative Example 3 and Comparative Example 4;

[0037] Figure 7 Effluent toxicity graph for Example 2, Comparative Example 3 and Comparative Example 4. DETAILED DESCRIPTION

[0038] The technical solutions of the present application are further described below in combination with examples.

[0039] Example 1

[0040] The wastewater treated in this example is industrial park wastewater, with an average pH of 7.2, an average COD of 82.67 mg / L, a B / C ratio of 0.38, and an average total organic carbon (TOC) of 24.75 mg / L. The wastewater toxicity was determined using the zebrafish egg method, and the zebrafish deformity rate at 72 hours after fertilization (72hpf) was as high as 80.5%, belonging to high-toxicity wastewater.

[0041] The wastewater was treated using the method of the present application, and the specific implementation steps are as follows:

[0042] (1) Constructing a microbial electrochemical system

[0043] The single-chamber microbial electrochemical system structure diagram is shown in Figure 1 , which includes a reactor 1, a counter electrode 2, a reference electrode 3, a working electrode 4, an electrochemical workstation 5, and a wire.

[0044] The B / C of the industrial wastewater is greater than 0.25, and a single-chamber microbial electrochemical system with a graphite rod as the working electrode is constructed. The system belongs to a three-electrode electrochemical reactor system, the main body of the container is a cylindrical glass container with an effective volume of 120 mL, and the top is a polytetrafluoroethylene cover, which is in a closed state during cultivation and operation. The three-electrode system includes a graphite rod working electrode, a platinum sheet counter electrode, and an Ag / AgCl reference electrode.

[0045] (2) Enrichment culture of electroactive biofilm

[0046] A mixed culture solution of 1:8:1 of bottom mud, industrial wastewater, and phosphate buffer solution was added to the reactor in step (1), and 0.5 g / L of sodium acetate was added as a carbon source, and was connected to the electrochemical workstation. The enrichment culture of electroactive biofilm was carried out by chronocoulometry, and when the current was less than 10 -5 After A, the culture solution was replaced, and after continuous culture for 30 days, the current density was greater than 4.69 A / m 2 , indicating that the biofilm was mature.

[0047] (3) Intermittent polarization driving system operation

[0048] After the biofilm was formed, only the industrial wastewater to be treated was injected into the reactor without adding buffer and carbon source. The electrochemical workstation was used to apply an external voltage of 0.6 V (relative to the Ag / AgCl reference electrode) on the working electrode, and the external voltage was intermittently provided (intermittent polarization mode) by using a manual switch mode (12 h open circuit, 12 h closed circuit) to drive the system operation. After 48 h of operation, samples were collected and filtered through a 0.45 μm filter, and then the COD and TOC values were determined. Subsequently, the water toxicity was determined by zebrafish embryo bioassay.

[0049] Comparative Example 1

[0050] Comparative Example 1 differs from Example 1 in that the system was driven to operate by applying a continuous (not manually disconnected) external voltage (continuous polarization mode) in step (3).

[0051] Comparative Example 2

[0052] Comparative Example 2 differs from Example 1 in that the system was not applied with an external voltage during operation, i.e., open circuit operation, in step (3).

[0053] The time-current diagram of Example 1 and Comparative Example 1 is shown in Figure 2 As can be seen from the diagram, the maximum current value of the intermittent polarization system of Example 1 can reach 0.42 mA, which is 2.8 times that of the continuous polarization control group (0.15 mA) of Comparative Example 1. In addition to the peak current, the constant current during the closed circuit operation under the intermittent polarization mode is also higher than that of the control group. The current in the system is generated by the metabolic activity of the anode microorganisms and is guided out of the electrode by the electrogenic microorganisms. Under the intermittent polarization mode, the microorganisms can accumulate electrons under the open circuit, and a very high instantaneous current is generated during the repolarization (closed circuit again). Therefore, the increase in current value indicates that the intermittent polarization mode promotes the metabolic activity of the electrogenic microorganisms.

[0054] The TOC concentration and removal rate of the effluent of Example 1, Comparative Example 1 and Comparative Example 2 are shown in Figure 3 As can be seen from the diagram, both the intermittent polarization system of Example 1 and the continuous polarization control group of Comparative Example 1 can effectively remove most of the organic pollutants in the industrial wastewater, with TOC removal rates of 82.2% and 81.4%, respectively. In the same time, the TOC removal rate of the open circuit control group of Comparative Example 2 is only 34%. In addition, the COD of the effluent of the intermittent polarization system of Example 1 and the continuous polarization control group of Comparative Example 1 is 15.8 mg / L and 16.7 mg / L, respectively, while that of the open circuit control group of Comparative Example 2 is 54 mg / L. This indicates that the application of an external voltage and the maintenance of electron flow can significantly improve the removal of organic matter in wastewater by the microbial electrochemical system, which is conducive to achieving the discharge of industrial wastewater in compliance with the standards.

[0055] The toxicity of the water discharged from Example 1, Comparative Example 1 and Comparative Example 2 is shown in the figure below: Figure 4 As shown in the figure, the deformity rate of zebra larvae 72hpf exposed to the effluent of the open-circuit control group of Comparative Example 2 was as high as 62.1%, indicating that the effluent still had high biological toxicity; it is worth noting that although the TOC concentration of the effluent of the continuous polarization control group of Comparative Example 1 was also low, its effluent still resulted in a 14.3% deformity rate of zebra larvae, i.e., it still had certain biological toxicity; by contrast, the deformity rate (3.5%) caused by the effluent of the intermittent polarization system of Example 1 was no different from that of the CK group (3.3%), indicating that the present invention can effectively remove the biological toxicity of industrial biochemical tail water and eliminate the negative impact of tail water discharge on aquatic ecosystems, thereby achieving the safe discharge of industrial wastewater. In addition, the intermittent polarization mode only applied external voltage for half of the time, which has obvious energy consumption advantages.

[0056] Example 2

[0057] The wastewater treated in this embodiment is industrial park wastewater, with an average pH of 7.3, an average COD of 85.33 mg / L, a B / C ratio of 0.22, and an average total organic carbon (TOC) of 25.12 mg / L. The toxicity of the wastewater was determined using the zebrafish egg method. The deformity rate of zebrafish larvae 72 hours after fertilization (72 hpf) was as high as 76.4%, which is highly toxic wastewater.

[0058] The wastewater is treated by the method of the present invention, and the specific implementation steps are as follows:

[0059] (1) A microbial electrochemical system with a Bio-C / MoS2 modified graphite rod electrode as the working electrode was constructed based on B / C < 0.25 and B / C ≥ 0.1. The preparation method of the Bio-C / MoS2 modified graphite rod electrode was as follows: the electrochemical reactor was a three-electrode system (volume of about 120 ml) with a diameter of 5 cm and a height of 5 cm, including a graphite rod working electrode, a platinum counter electrode, and an Ag / AgCl reference electrode. Bio-C / MoS2 material and 0.01 M citrate buffer (pH = 6.5) were added to the reactor and stirred rapidly to uniformly distribute Bio-C / MoS2. The concentration was about 0.5 g / L. The graphite rod electrode was modified by cyclic voltammetry using an electrochemical workstation with a scan rate of 100 mV / s, a scanning potential range of -0.8 V to 1.0 V vs Ag / AgCl reference electrode, and 30 scans. Finally, the modified electrode was dried at 25 °C.

[0060] The preparation method of the Bio-C / MoS2 is as follows: after peeling and slicing of the date, date pits are obtained, which are ground by a grinder, and then calcined at 600 DEG C in a nitrogen atmosphere for 5h to obtain an intermediate product; the intermediate product is added into a 3M KOH solution for reaction for 8h, and the powder after filtration is pyrolyzed at 1000 DEG C in a nitrogen atmosphere for 4h, and the obtained product is washed to neutral to obtain a porous biochar material; 0.65g of ammonium heptamolybdate, 0.52g of thiourea and 10g of the prepared biochar are poured into a date peel extract solution, stirred uniformly, and then poured into a high-pressure reaction kettle for hydrothermal reaction at 170 DEG C for 12h, and after natural cooling, centrifugation and washing, the Bio-C / MoS2 material is obtained.

[0061] (2) Enrichment culture of electroactive biofilm

[0062] The mixed culture solution of 1:8:1 of the volume ratio of the bottom mud, industrial wastewater and phosphate buffer solution is added into the reactor in 1), and 1g / L of sodium acetate is added as a carbon source, and is connected to an electrochemical workstation. The enrichment culture of the electroactive biofilm is carried out by chronocoulometry, and when the generated current is less than 10 -5 The culture solution is replaced after A, and after continuous culture for 30 days, the current density is greater than 4.69A / m 2 It is shown that the biofilm is mature.

[0063] (3) Intermittent polarization driving system operation

[0064] After the biofilm is hung, only the industrial wastewater to be treated is injected into the reactor without adding buffer solution and carbon source, and the electrochemical workstation is used to apply an external voltage of 0.6V on the working electrode (relative to the Ag / AgCl reference electrode), and the manual switch mode (12h open circuit, 12h closed circuit) is used to intermittently provide the external voltage (intermittent polarization mode) to drive the system operation. After 24h of operation, the sample is collected, filtered through a 0.45μm filter membrane, and then the COD and TOC values are measured. Subsequently, the toxicity of the effluent is determined by the zebra fish egg method.

[0065] Comparative Example 3

[0066] Comparative Example 3 is different from Example 2 in that the unmodified graphite rod electrode is used as a control group.

[0067] Comparative Example 4

[0068] Comparative Example 4 is different from Example 2 in that the unmodified graphite rod electrode is used as a control group, and the running time in step 3) is extended to 48h.

[0069] The time-current diagram of Example 2 and Comparative Example 3 is as follows: Figure 5As shown in the figure, the maximum current value of the Bio-C / MoS2 modified graphite rod electrode of Example 2 can reach 0.57 mA, which is 1.5 times that of the unmodified electrode control group (0.37 mA). In addition to the peak current, the constant current of the Bio-C / MoS2 modified graphite rod electrode during closed circuit operation is also higher than that of the control group. Microorganisms can accumulate electrons under open circuit in the intermittent polarization mode, so the increase in current value of Example 2 indicates that Bio-C / MoS2 is beneficial to the storage of more electrons by the electrogenic microorganisms under open circuit conditions, i.e., up-regulates the expression of redox proteins related to electron transfer, and further improves the electron transfer rate in the system.

[0070] The effluent TOC concentration and removal rate of Example 2, Comparative Example 3 and Comparative Example 4 are as shown in the following table: Figure 6 As shown in the figure, the Bio-C / MoS2 modified graphite rod electrode of Example 2 can efficiently remove most of the organic pollutants in the refractory industrial wastewater within 24 h, with a TOC removal rate of 80.3%. In the same time, the TOC removal rate of the unmodified electrode control group is only 63.6%. Even if the treatment time is extended to 48 h, the TOC removal rate of the unmodified electrode control group does not exceed 70%. The microbial electrochemical system of Example 2 shows obvious advantages. This shows that compared with the general graphite rod electrode, the Bio-C / MoS2 modified graphite rod electrode can significantly improve the efficiency of removing organic pollutants in refractory industrial wastewater under intermittent polarization conditions.

[0071] The effluent toxicity of Example 2, Comparative Example 3 and Comparative Example 4 is as shown in the following table: Figure 7 As shown in the figure, the effluent of the control group with unmodified graphite rod electrode under the operating conditions of 24 h and 48 h still caused 28.8% and 21.2% of the zebrafish to be deformed, i.e., there was still a certain biological toxicity. In contrast, the deformed rate (6.1%) of the effluent of the Bio-C / MoS2 modified graphite rod electrode system of Example 2 was not significantly different from that of the CK group (5.8%), indicating that the present application can effectively remove the toxicity of the refractory industrial biochemical tail water and eliminate the negative impact of tail water discharge on the aquatic ecosystem, thereby realizing the safe discharge of industrial wastewater.

[0072] Example 3

[0073] The wastewater treated in this example is refinery industrial wastewater, with an average pH of 6.9, an average COD of 102 mg / L, a B / C ratio of 0.18, and an average total organic carbon (TOC) of 31.44 mg / L. The toxicity of the wastewater was determined by zebrafish egg method, and the deformed rate of the larvae 72 hours after fertilization (72hpf) was as high as 96.3%, belonging to high-toxicity wastewater.

[0074] The present example is basically the same as example 2, the only difference is that the preparation parameters of the Bio-C / MoS2 modified graphite rod electrode: in the reactor, Bio-C / MoS2 material and 0.1M citrate buffer (pH=5.5) are added, and Bio-C / MoS2 is uniformly distributed by rapid stirring, the concentration is about 1g / L, the graphite rod electrode is modified by cyclic voltammetry using an electrochemical workstation, the scanning rate is 50mV / s, the scanning potential range is controlled in-0.8V~1.0V vs Ag / AgCl reference electrode, and the scanning number is 60 times. The results are as follows: after the above method is run, the average value of the effluent TOC concentration of the microbial electrochemical system is reduced to 5.32mg / L, the zebrafish larva malformation rate caused by effluent exposure is reduced by 90%, the average malformation rate is only 6.14%, and the toxicity of the refractory petrochemical industrial wastewater is efficiently reduced.

Claims

1. A low energy wastewater integrated toxicity reduction method, characterized in that, The method comprises the following steps: (1) selecting wastewater B / C, wherein B / C is 5-day biochemical oxygen demand / chemical oxygen demand When the industrial wastewater is 0.1≤B / C<0.25, a graphite rod electrode modified by biochar / molybdenum disulfide is used for treatment; (2) constructing a microbial electrochemical system A single-chamber microbial electrochemical system is constructed by using the graphite rod electrode modified by biochar / molybdenum disulfide as a working electrode; (3) enriching and culturing an electroactive biofilm A mixed culture solution containing bottom mud, industrial wastewater, phosphate buffer and a carbon source is added to the system, and a chronoamperometry method is used for enrichment and culture of the electroactive biofilm, and the culture solution is replaced regularly until the biofilm matures; (4) driving the system to run in an intermittent polarization mode After the biofilm is formed, only the industrial wastewater to be treated needs to be injected into the system, and an external voltage is applied to the working electrode, and an open circuit and a closed circuit intermittent polarization mode is used to drive the system to run, so as to realize toxicity reduction of the industrial wastewater; the open circuit and closed circuit intermittent polarization mode is: open circuit for 6-12 hours, and closed circuit for 6-12 hours; The preparation method of the graphite rod electrode modified by biochar / molybdenum disulfide is that the biochar / molybdenum disulfide is uniformly dispersed in a buffer solution with pH=5.5-6.5, and the graphite rod electrode is modified by using a cyclic voltammetry method. The concentration of the biochar / molybdenum disulfide is 0.5-1.0 g / L; the raw material of the biochar in the biochar / molybdenum disulfide is coconut date pit.

2. The low energy wastewater integrated toxicity reduction process of claim 1, wherein, The parameters of the cyclic voltammetry method for modifying the graphite rod electrode are: the scanning rate is 50-100 mV / s, the scanning potential range is controlled to be-0.8 V-1.0 V vs. Ag / AgCl reference electrode, and the scanning number is 30-60 times.

3. The low energy integrated wastewater toxicity reduction process of claim 1, wherein, In step (4), the treatment time of the industrial wastewater is 24-48 hours.

4. The low energy wastewater integrated toxicity reduction process of claim 1, wherein, In step (3), the culture conditions are as follows: the volume ratio of the mixed culture solution of the sludge, the industrial wastewater, and the phosphate buffer is 1-2:6-8:1-2, sodium acetate is selected as the carbon source, and the concentration is 0.5-1 g / L; when the output current value of single culture is less than or equal to 10 -5 After the A stage, the culture solution is replaced, and when the output current reaches the maximum and is stable, it indicates that the biofilm is mature.

5. The low energy integrated wastewater toxicity reduction process of claim 4, wherein, The single culture time is 2-4 days, and the total culture time is 25-35 days.

6. The low energy integrated wastewater toxicity reduction process of claim 1, wherein, In step (4), the external voltage value is 0.6 V vs. Ag / AgCl reference electrode.

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