Patent Publication Number: US-2022234932-A1

Title: Method of reducing and controlling hazardous substance in process of high-value biological conversion of urban organic waste

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from, Chinese patent application number 2021100869888, filed Jan. 22, 2021, the content of which is incorporated herein in the entirety by reference. 
     TECHNICAL FIELD 
     The present invention relates to the field of urban organic waste treatments, and in particular to a method of reducing and controlling a hazardous substance in a process of high-value biological conversion of an urban organic waste. 
     BACKGROUND 
     With rapid development or Chinese urbanization, the amount of the urban organic waste generated (including restaurant garbage and kitchen garbage and the like) is sharply increasing. Urban organic waste contains a large amount of carbohydrates, protein substances and the like, and are directly discharged into the environment without treatment, leading to severe environmental pollution and waste of organic resources. One method to improve a utilization value of the organic waste is to convert the organic waste into energy source substances such as methane and hydrogen by a biological method. In contrast with the conventional method of converting the urban organic waste into methane and hydrogen, a biological method is employed to convert the urban organic waste into liquid chemicals such as acetic acid, propanoic acid and lactic acid in an open system. This method has the advantages of simple operation, easy transportation and storage of products and low requirements for surrounding safety levels. Therefore, in recent years, it has become a topic of increased interest at home and abroad. 
     Detection frequency of antibiotics and heavy metal ions in urban organic waste is also increasing. In addition to causing chemical environmental pollution, antibiotics may also induce microbes in the environment to mutate and produce resistance genes and may harm human health when spread. The discharge of excess heavy metal ions into environments will not only pose severe harm to systems including bodies of water, aquatic plants, and aquatic animals, but may also affect human health through the food chain, bringing about diseases such as gout-like syndromes, arthralgia and kidney injury. Furthermore, in a system of high-value biological conversion of urban organic waste, the presence of excess antibiotics and heavy metal ions may also produce noticeable inhibition effects on the activity of microbes. Therefore, research and development of a method of reducing and eliminating an unfavorable effect of antibiotics and heavy metal on a high-value biological conversion of urban organic waste may be significant for improving the effect of high-value biological conversion of urban organic waste and reducing the unfavorable effect of antibiotics and heavy metal in the organic waste residues on the environment. 
     At present, antibiotics are mainly treated by methods such as the artificial wetland method, soil infiltration method, ultrasonic degradation method and low-temperature plasma method. The heavy metal ions are mainly removed by methods such as the chemical precipitation method, oxidation reduction treatment, solvent extraction separation, adsorption method, membrane separation method and ion exchange method. If a new method of reducing and eliminating an unfavorable effect of antibiotics and heavy metal on high-value biological conversion of urban organic waste can be developed based on consideration of an inhibition effect of the antibiotics and heavy metal ions on the high-value biological conversion of urban organic waste, there may be improvement in high-value utilization levels of urban organic waste and product quality and reduction in secondary pollution to the environment resulting from release of hazardous substances in solid or liquid residues. 
     SUMMARY 
     In order to solve the above defects of the prior art, the present invention provides a method of reducing and controlling a hazardous substance in a process of high-value biological conversion of an urban organic waste so as to solve the difficulties in the prior art. 
     In order to achieve the above object and other relevant objects, the present invention is achieved in the following technical solution. 
     One of the objects of the present invention is to provide a method of reducing and controlling a hazardous substance in a process of high-value biological conversion of an urban organic waste. The method includes the following steps: 
     1) acclimation stage: mixing a sludge, a first urban organic waste and an organic acid with water for acclimation to obtain an acclimatized sludge; 
     2) stage 1 of biological conversion: mixing the acclimatized sludge with a second urban organic waste to perform anaerobic culture; 
     3) stage 2 of biological conversion: adding nitrate and bacteria to continue anaerobic culture so as to obtain an organic acid; 
     Preferably, the sludge is a residual sludge of a wastewater treatment plant, a pH of the sludge is 6.0-7.0, a suspended solid concentration is 900 mg/L-10400 mg/L, and a molar ratio of carbon to nitrogen is 5.0-7.5; the main properties of the first urban organic waste and the second urban organic waste are as follows: a pH is 5.0-6.5, a suspended solid concentration is 8000 mg/L-81600 mg/L, and a molar ratio of carbon to nitrogen is 18-27. In the present invention, suspended solid is measured with reference to stipulations of Monitoring Analysis method of Water and Wastewater (fourth version) (China Environmental Science Press House, December 2002). 
     Preferably, in step 1), a dry weight ratio of the sludge to the first urban organic waste is 1:(7-11). 
     More preferably, the dry weight ratio of the sludge to the first urban organic waste is 1:(8-10). 
     Preferably, in step 1), the acclimation condition is that a pH value is 4-11 and an acclimation temperature is 5° C.-80° C. 
     Preferably, in step 1), the acid is acetic acid, propanoic acid or lactic acid. 
     Preferably, in step 1), a content of a solid in the mixture formed by mixing is 2000 mg/L-10000 mg/L. In the present invention, the content of the solid is measured with reference to stipulations of Monitoring Analysis method of Water and Wastewater (fourth version) (China Environmental Science Press House, December 2002). 
     Preferably, in step 1), a concentration of an acid in the mixture formed by mixing is 50 mg/L-3000 mg/L. 
     More preferably, when the acid is acetic acid, an acclimation condition is that: a pH value is 8-10, and a temperature is 24° C.-26° C.; a concentration of acetic acid is 2000˜2200 mg/L. 
     Further preferably, when the acid is acetic acid, the acclimation condition is that: the pH value is 9, and the temperature is 25° C.; the concentration of acetic acid is 2100 mg/L. 
     More preferably, when the acid is propanoic acid, an acclimation condition is that: a pH value is 8-10, and a temperature is 24° C.˜26° C.; a concentration of propanoic acid is 1100-1300 mg/L. 
     Further preferably, when the acid is propanoic acid, the acclimation condition is that the pH value is 8 and the temperature is 25° C.; the concentration of propanoic acid is 1200 mg/L. 
     More preferably, when the acid is lactic acid, an acclimation condition is that a pH value is 5.5-7.5, and a temperature is 24° C.-26° C.; a concentration of lactic acid is 500-700 mg/L. 
     More preferably, when the acid is lactic acid, the acclimation condition is that the pH value is 6.5, and the temperature is 25° C.; the concentration of lactic acid is 600 mg/L. 
     Preferably, in step 2), a dry weight ratio of the acclimatized sludge to the second urban organic waste is (0.5-30):100. 
     More preferably, the dry weight ratio of the acclimatized sludge to the second urban organic waste is (6-10):100. 
     Preferably, in step 2), the mixture formed by mixing further includes water, and a concentration of a solid in the mixture is 5000 mg/L-70000 mg/L. 
     More preferably, the concentration of the solid in the mixture is 5500 mg/L-30000 mg/L. 
     Preferably, in step 2), a condition of the anaerobic culture is that: a pH value is 4-11, a time is 0.5 d-6 d, and a temperature is 5° C.-80° C. 
     More preferably, when the acid is acetic acid, the condition of the anaerobic culture is that the pH value is 8-10, the time is 5 d-6 d, and the temperature is 24° C.-26° C. 
     More preferably, when the acid is acetic acid, the condition of the anaerobic culture is that the pH value is 9, the time is 6 d, and the temperature is 25° C. 
     More preferably, when the acid is propanoic acid, the condition of the anaerobic culture is that the pH value is 7-9, the time is 4 d-6 d, and the temperature is 24° C.-26° C. 
     Further preferably, when the acid is acetic acid, the condition of the anaerobic culture is that the pH value is 8, the time is 5 d, and the temperature is 25° C. 
     More preferably, when the acid is lactic acid, the condition of the anaerobic culture is that the pH value is 5.5-7.5, the time is 3 d-5 d, and the temperature is 24° C.-26° C. 
     Further preferably, when the acid is acetic acid, the condition of the anaerobic culture is that the pH value is 6.5, the time is 4 d, and the temperature is 25° C. 
     Preferably, in step 3), a condition of continuing the anaerobic culture is that a pH value is 4-11, a time is 0.5 d-6 d, and a temperature is 5° C.-80° C. 
     Preferably, the nitrate is sodium nitrate or potassium nitrate. 
     More preferably, an addition amount of the nitrate does not exceed 50 mg/L. 
     Further preferably, with a volume of the mixture formed by mixing in step 2) as a reference, the concentration of the nitrate is 20 mg/L-24 mg/L. 
     Preferably, the bacteria include denitrifying bacteria and exoelectrogenic bacteria. 
     More preferably, the denitrifying bacteria include  Pseudomonas  and  Paracoccus denitrificans,  and the exoelectrogenic bacteria include  Shewanella  and  Geobacter.    
     More preferably, a dry weight ratio of the denitrifying bacteria to the second urban organic waste is (0.001-20):100, and a dry weight ratio of the exoelectrogenic bacteria to the second urban organic waste is (0.001-20):100. 
     Further preferably, the dry weight ratio of the denitrifying bacteria to the second urban organic waste is (0.2-0.6):100, and the dry weight ratio of the exoelectrogenic bacteria to the second urban organic waste is (0.5-1.5):100. 
     Preferably, the organic acid includes acetic acid, propanoic acid or lactic acid; the hazardous substance includes heavy metal and antibiotic; the antibiotic includes tetracycline and sulfadiazine; and the heavy metal includes chromium and arsenic. 
     In the present invention, in a biological conversion process of an urban organic waste, microbes are introduced to eliminate hazardous substances such as antibiotics and heavy metals through degradation or oxidation reduction mechanism of microbes. With antibiotics as an electron donor and heavy metal ions as an electron acceptor, under the action of the microbes such as  Pseudomonas  and  Paracoccus denitrificans,  the antibiotic is degraded and completely mineralized while the heavy metal ions are reduced and detoxified. Since the exoelectrogenic bacteria have the capability to promote electron transfer or transport, the efficiency of the antibiotic degradation and heavy metal ion reduction will be significantly improved by adding the exoelectrogenic bacteria during an antibiotic degradation and heavy metal ion reduction process. Furthermore, metabolic products of acidogenic bacteria (for example, lactic acid) may be used as a carbon source required for growth and metabolism of the exoelectrogenic bacteria. As a result, the use of the present invention greatly promotes the elimination efficiency of the hazardous substances and increases a product yield of the organic acid for high-value anaerobic biological conversion of the urban organic waste. 
     Compared with prior art, the present invention has the following beneficial effects. 
     (1) In the present invention, the unfavorable effect of antibiotics and heavy metal ions in a process of biological conversion of the urban organic waste into an organic acid, for example, a high-value chemical, such as acetic acid, propanoic acid and lactic acid, is biologically reduced and the yield of the organic acid is increased by three folds. 
     (2) In the present invention, without using chemical agents, a residue amount of antibiotics and heavy metal ions after biological conversion of the urban organic waste is reduced, thereby improving the yield of products such as high quality organic acid, and significantly reducing secondary pollution to the environment resulting from the residues of the treatment of the urban organic waste. 
    
    
     
       BRIEF DESCRIPTIONS OF THE DRAWINGS 
         FIG. 1  is a flowchart illustrating a method of reducing and controlling a hazardous substance in a process of high-value biological conversion of an urban organic waste. 
     
    
    
     DETAILED DESCRIPTIONS OF EMBODIMENTS 
     The present invention will be further described below in combination with specific embodiments and those skilled in the art may know about other advantages and efficacies of the present invention easily from the contents disclosed in the specification. 
     Before the specific embodiments of the present invention are further described, it should be understood that the scope of protection of the present invention is not limited to the following specific embodiments. It should be further understood that the terms used in the embodiments are used for describing a particular solution rather than limiting the present invention. Those test methods without specific conditions specified in the following embodiments are generally carried out under normal conditions or under conditions recommended by each manufacturer. 
     When a value range is given in an embodiment, it should be understood that unless otherwise stated in the present invention, two endpoints of each value range and any value between the two endpoints may be selected. Unless otherwise defined, all technical or scientific terms used in the present invention has the same meaning as generally understood by those skilled in the art. In addition to the specific methods, devices and materials used in the embodiments, those skilled in the art may also use any method, device and material in the prior art which are similar or equivalent to the method, device and material mentioned in the embodiments of the present invention based on the knowledge of the prior art and the recordings of the present invention, so as to implement the present invention. 
       FIG. 1  shows a method of reducing and controlling a hazardous substance in a process of biological conversion of an urban organic waste. The method specifically includes the following steps. 
     1) Acclimation stage: a sludge, a first urban organic waste and an acid are mixed with water for acclimation to obtain an acclimatized sludge; specifically, a dry weight ratio of the sludge to the first urban organic waste is 1:(7-11), the acid is acetic acid, propanoic acid or lactic acid, a concentration of a solid in the mixture is 2000 mg/L-10000 mg/L, a concentration of the acid in the mixture is 50 mg/L-3000 mg/L, and the acclimation condition is that a pH value is 4-11 and a temperature is 5° C.-80° C. 
     2) Stage 1 of biological conversion: the acclimatized sludge is mixed with a second urban organic waste to perform anaerobic culture; specifically, a dry weight ratio of the acclimatized sludge to the second urban organic waste is (0.5-30):100, the mixture further includes water, a concentration of a solid in the mixture is 5000 mg/L-70000 mg/L, and a condition of the anaerobic culture is that a pH value is 4-11, a time is 0.5 d-6 d, and a temperature is 5° C.-80° C. 
     3) Stage 2 of biological conversion: nitrate and bacteria are added to continue anaerobic culture so as to obtain an organic acid; specifically, the nitrate is sodium nitrate or potassium nitrate; the bacteria include denitrifying bacteria and exoelectrogenic bacteria, and a condition of continuing anaerobic culture is that a pH value is 4-11, a time is 0.5 d-6 d, and a temperature is 5° C.-80° C. 
     As a preferred embodiment of the embodiments of the present invention, the denitrifying bacteria include  Pseudomonas  and  Paracoccus denitrificans,  and the exoelectrogenic bacteria include  Shewanella  and  Geobacter.    
     As a preferred embodiment of the embodiments of the present invention, a dry weight ratio of the denitrifying bacteria to the second urban organic waste is (0.001-20):100, and a dry weight ratio of the exoelectrogenic bacteria to the second urban organic waste is (0.001-20):100. 
     In the embodiments of the present invention, biological conversion is performed with the optimal dry weight ratio of the sludge to the first urban organic waste being 1:9. 
     Embodiment 1 
     The method of reducing and controlling a hazardous substance in a process of high-value biological conversion of an urban organic waste in the embodiment includes the following steps: 
     1) Acclimation stage: a residual sludge of a wastewater treatment plant, the first urban organic waste, acetic acid and water were placed in a biological acclimation reactor and mixed uniformly, where a dry weight ratio of the sludge to the first urban organic waste was 1:9, a concentration of a solid in the mixture was 10000 mg/L, a concentration of acetic acid in the mixture was 3000 mg/L; a pH value in the acclimation reactor was maintained as 11 and a temperature was maintained as 80° C., and a concentration of acetic acid in the acclimation reactor was measured each day; when the concentration of acetic acid in the reactor no longer increased noticeably over time, the above operations were performed again; through acclimation of 51 d, an acclimatized sludge (VS-A) was obtained. 
     2) Stage 1 of biological conversion: the second urban organic waste and the acclimatized sludge (VS-A) were added to a biological conversion reactor and mixed uniformly, where a dry weight ratio of VS-A to the second urban organic waste was 30:100; water was added until the concentration of a solid in the biological conversion reactor was 70000 mg/L; sulfadiazine, tetracycline, potassium dichromate and sodium arsenate were added to the biological conversion reactor in the amount of 10 mg/L respectively, and then stirred under an anaerobic condition for 6 days with the pH value controlled to 11 and a culture temperature to 80° C. 
     3) Stage 2 of biological conversion: potassium nitrate was added to a product of the biological conversion to 50 mg/L, where a dry weight ratio of  Pseudomonas  to the second urban organic waste was 0.001:100, and a dry weight ratio of  Shewanella  to the second urban organic waste was 0.001:100; the above mixture was stirred for 6 days and then solid-liquid separation was performed and then the concentrations of lactic acid, tetracycline, sulfadiazine, chromium ions and arsenic ions in the liquid phase were analyzed, and the concentrations of tetracycline, sulfadiazine, chromium ions and arsenic ions in the solid phase were analyzed. 
     As a result, the concentration of acetic acid in the liquid phase was 3241 mg/L, and the removal rates of total sulfadiazine, tetracycline, hexavalent chromium and pentavalent arsenic in the liquid and solid phases were 39%, 36%, 41% and 41%, respectively. 
     Embodiment 2, embodiment 3, embodiment 4 and control embodiment 1 are identical to the embodiment 1 except for specific parameters listed in table below. The specific parameters and detection results are shown in table below. 
     
       
         
           
               
               
               
               
               
               
               
             
               
                   
               
               
                   
                   
                   
                   
                   
                   
                 Control 
               
               
                   
                   
                 Embodiment 
                 Embodiment 
                 Embodiment 
                 Embodiment 
                 embodiment 
               
               
                 Stage 
                 Index 
                 1 
                 2 
                 3 
                 4 
                 1 
               
               
                   
               
             
            
               
                 Acclimation 
                 dry weight 
                 1:9 
                 1:9 
                 1:9 
                 1:9 
                 1:9 
               
               
                 stage 
                 ratio of the 
               
               
                   
                 sludge to the 
               
               
                   
                 first urban 
               
               
                   
                 organic waste 
               
               
                   
                 concentration 
                 3000 
                 3000 
                 2100 
                 2100 
                 50 
               
               
                   
                 of acetic acid 
               
               
                   
                 in the mixture/ 
               
               
                   
                 mg/L 
               
               
                   
                 concentration 
                 10000 
                 10000 
                 8000 
                 8000 
                 2000 
               
               
                   
                 of solid in the 
               
               
                   
                 mixture/mg/L 
               
               
                   
                 acclimation pH 
                 11 
                 11 
                 9 
                 9 
                 4 
               
               
                   
                 acclimation 
                 80 
                 80 
                 25 
                 25 
                 5 
               
               
                   
                 temperature/° C. 
               
               
                   
                 acclimation 
                 51 
                 51 
                 46 
                 46 
                 60 
               
               
                   
                 time/d 
               
               
                 Stage 1 of 
                 dry weight 
                  30:100 
                  30:100 
                  8:100 
                  8:100 
                  0.5:100 
               
               
                 biological 
                 ratio of the 
               
               
                 conversion 
                 acclimatized 
               
               
                   
                 sludge to the 
               
               
                   
                 second urban 
               
               
                   
                 organic waste 
               
               
                   
                 solid 
                 70000 
                 70000 
                 30000 
                 30000 
                 5000 
               
               
                   
                 concentration 
               
               
                   
                 (mg/L) 
               
               
                   
                 culture pH 
                 11 
                 11 
                 9 
                 9 
                 4 
               
               
                   
                 culture 
                 80 
                 80 
                 25 
                 25 
                 5 
               
               
                   
                 temperature/° C. 
               
               
                   
                 culture time/d 
                 6 
                 6 
                 1 
                 3 
                 1 
               
               
                 Stage 2 of 
                 nitrate and 
                 potassium 
                 potassium 
                 sodium 
                 sodium 
                 — 
               
               
                 biological 
                 concentration/ 
                 nitrate 
                 nitrate 
                 nitrate 
                 nitrate 
               
               
                 conversion 
                 mg/L 
                 50 
                 50 
                 22 
                 22 
               
               
                   
                 dry weight 
                   Pseudomonas / 
                   Pseudomonas / 
                 
                   paracoccus 
                 
                 
                   paracoccus 
                 
               
               
                   
                 ratio of the 
                 0.001:100 
                 20:100 
                   denitrificans / 
                   denitrificans / 
               
               
                   
                 bacteria to the 
                   
                   
                 0.4:100 
                 0.4:100 
               
               
                   
                 second urban 
                   Shewanella / 
                 
                   Geobacter 
                 
                   Geobacter / 
                   Shewanella / 
               
               
                   
                 organic waste 
                 0.001:100 
                 20:100 
                 1:100 
                 1:100 
               
               
                   
                 continued 
                 6 
                 6 
                 1 
                 3 
               
               
                   
                 conversion 
               
               
                   
                 time/d 
               
               
                 Product 
                 acetic acid/ 
                 3241 
                 2138 
                 3038 
                 4967 
                 1096 
               
               
                   
                 mg/L 
               
               
                   
                 sulfadiazine 
                 39 
                 43 
                 61 
                 83 
                 12 
               
               
                   
                 removal rate/% 
               
               
                   
                 tetracycline 
                 36 
                 42 
                 63 
                 81 
                 10 
               
               
                   
                 removal rate/% 
               
               
                   
                 Chromium 
                 41 
                 50 
                 68 
                 89 
                 22 
               
               
                   
                 removal rate/% 
               
               
                   
                 arsenic 
                 41 
                 47 
                 61 
                 88 
                 19 
               
               
                   
                 removal rate/% 
               
               
                   
               
            
           
         
       
     
     Embodiment 5 
     The method of reducing and controlling a hazardous substance in a process of high-value biological conversion of an urban organic waste in the embodiment includes the following steps. 
     1) Acclimation stage: a residual sludge of a wastewater treatment plant, the first urban organic waste, propanoic acid and water were placed in a biological acclimation reactor and mixed uniformly, where a dry weight ratio of the sludge to the first urban organic waste was 1:9, a concentration of a solid in the mixture was 10000 mg/L, a concentration of propanoic acid in the mixture was 3000 mg/L; a pH value in the acclimation reactor was maintained as 11 and a temperature was maintained as 80° C., and a concentration of propanoic acid in the acclimation reactor was measured each day; when the concentration of propanoic acid in the reactor no longer increased noticeably over time, the above operations were performed again; through acclimation of 49 d, an acclimatized sludge (VS-P) was obtained. 
     2) Stage 1 of biological conversion: the second urban organic waste and the acclimatized sludge (VS-P) were added to a biological conversion reactor and mixed uniformly, where a dry weight ratio of VS-P to the second urban organic waste was 30:100; water was added until the concentration of a solid in the biological conversion reactor was 70000 mg/L; sulfadiazine, tetracycline, potassium dichromate and sodium arsenate were added to the biological conversion reactor in the amount of 10 mg/L respectively, and then stirred under an anaerobic condition for 6 days with the pH value controlled to 11 and a culture temperature to 80° C. 
     3) Stage 2 of biological conversion: potassium nitrate was added to a product of the biological conversion to 50 mg/L, and  Pseudomonas  and  Shewanella  were then added, where a dry weight ratio of  Pseudomonas  to the second urban organic waste was 0.001:100, and a dry weight ratio of  Shewanella  to the second urban organic waste was 0.001:100; the above mixture was stirred for 6 days and then solid-liquid separation was performed and then the concentrations of lactic acid, tetracycline, sulfadiazine, chromium ions and arsenic ions in the liquid phase were analyzed, and the concentrations of tetracycline, sulfadiazine, chromium ions and arsenic ions in the solid phase were analyzed. 
     As a result, the concentration of propanoic acid in the liquid phase was 1394mg/L, and the removal rates of total sulfadiazine, tetracycline, hexavalent chromium and pentavalent arsenic in the liquid and solid phases were 31%, 33%, 44% and 45% respectively. 
     Embodiment 6, embodiment 7, embodiment 8 and control embodiment 2 are identical to the embodiment 5 except for specific parameters listed in table below. The specific parameters and detection results are shown in table below. 
     
       
         
           
               
               
               
               
               
               
               
             
               
                   
               
               
                   
                   
                   
                   
                   
                   
                 Control 
               
               
                   
                   
                 Embodiment 
                 Embodiment 
                 Embodiment 
                 Embodiment 
                 embodiment 
               
               
                 Stage 
                 Index 
                 5 
                 6 
                 7 
                 8 
                 2 
               
               
                   
               
             
            
               
                 Acclimation 
                 dry weight 
                 1:9 
                 1:9 
                 1:9 
                 1:9 
                 1:9 
               
               
                 stage 
                 ratio of the 
               
               
                   
                 sludge to the 
               
               
                   
                 first urban 
               
               
                   
                 organic waste 
               
               
                   
                 concentration 
                 3000 
                 3000 
                 1200 
                 1200 
                 50 
               
               
                   
                 of acetic acid 
               
               
                   
                 in the mixture/ 
               
               
                   
                 mg/L 
               
               
                   
                 concentration 
                 10000 
                 10000 
                 8000 
                 8000 
                 2000 
               
               
                   
                 of solid in the 
               
               
                   
                 mixture/ 
               
               
                   
                 mg/L 
               
               
                   
                 acclimation pH 
                 11 
                 11 
                 8 
                 8 
                 4 
               
               
                   
                 acclimation 
                 80 
                 80 
                 25 
                 25 
                 5 
               
               
                   
                 temperature/° C. 
               
               
                   
                 acclimation 
                 49 
                 56 
                 44 
                 42 
                 58 
               
               
                   
                 time/d 
               
               
                 Stage 1 of 
                 dry weight 
                  30:100 
                  30:100 
                  8:100 
                  8:100 
                  0.5:100 
               
               
                 biological 
                 ratio of the 
               
               
                 conversion 
                 acclimatized 
               
               
                   
                 sludge to the 
               
               
                   
                 second urban 
               
               
                   
                 organic waste 
               
               
                   
                 solid 
                 70000 
                 70000 
                 30000 
                 30000 
                 5000 
               
               
                   
                 concentration/ 
               
               
                   
                 mg/L 
               
               
                   
                 culture pH 
                 11 
                 11 
                 8 
                 9 
                 4 
               
               
                   
                 culture 
                 80 
                 80 
                 25 
                 25 
                 5 
               
               
                   
                 temperature/° C. 
               
               
                   
                 culture time/d 
                 6 
                 6 
                 1 
                 2.5 
                 1 
               
               
                 Stage 2 of 
                 nitrate and 
                 potassium 
                 potassium 
                 sodium 
                 sodium 
                 — 
               
               
                 biological 
                 concentration/ 
                 nitrate 
                 nitrate 
                 nitrate 
                 nitrate 
               
               
                 conversion 
                 mg/L 
                 50 
                 50 
                 22 
                 22 
               
               
                   
                 dry weight 
                   Pseudomonas / 
                   Pseudomonas / 
                 
                   paracoccus 
                 
                 
                   paracoccus 
                 
               
               
                   
                 ratio of the 
                 0.001:100 
                 20:100 
                   denitrificans / 
                   denitrificans / 
               
               
                   
                 bacteria to the 
                   
                   
                 0.4:100 
                 0.4:100 
               
               
                   
                 second urban 
                   Shewanella / 
                   Geobacter / 
                   Geobacter / 
                   Shewanella / 
               
               
                   
                 organic waste 
                 0.001:100 
                 20:100 
                 1:100 
                 1:100 
               
               
                   
                 continued 
                 6 
                 6 
                 1 
                 2.5 
               
               
                   
                 conversion 
               
               
                   
                 time/d 
               
               
                 Product 
                 propanoic 
                 1394 
                 906 
                 2367 
                 3385 
                 604 
               
               
                   
                 acid/mg/L 
               
               
                   
                 sulfadiazine 
                 31 
                 28 
                 68 
                 86 
                 12 
               
               
                   
                 removal rate/% 
               
               
                   
                 tetracycline 
                 33 
                 24 
                 65 
                 83 
                 13 
               
               
                   
                 removal rate/% 
               
               
                   
                 chromium 
                 44 
                 40 
                 71 
                 90 
                 21 
               
               
                   
                 removal rate/% 
               
               
                   
                 arsenic 
                 45 
                 43 
                 73 
                 93 
                 22 
               
               
                   
                 removal rate/% 
               
               
                   
               
            
           
         
       
     
     Embodiment 9 
     The method of reducing and controlling a hazardous substance in a process of high-value biological conversion of an urban organic waste in the embodiment includes the following steps: 
     1) Acclimation stage: a residual sludge of a wastewater treatment plant, the first urban organic waste, lactic acid and water were placed in a biological acclimation reactor and mixed uniformly, where a dry weight ratio of the sludge to the first urban organic waste was 1:9, a concentration of a solid in the mixture was 10000 mg/L, a concentration of lactic acid in the mixture was 3000 mg/L; a pH value in the acclimation reactor was maintained as 11 and a temperature was maintained as 80° C., and a concentration of lactic acid in the acclimation reactor was measured each day; when the concentration of lactic acid in the reactor no longer increased noticeably over time, the above operations were performed again; through acclimation of 46 d, an acclimatized sludge (VS-L) was obtained. 
     2) Stage 1 of biological conversion: the second urban organic waste and the acclimatized sludge (VS-L) were added to a biological conversion reactor and mixed uniformly, where a dry weight ratio of VS-L to the second urban organic waste was 30:100; water was added until the concentration of a solid in the biological conversion reactor was 70000 mg/L; sulfadiazine, tetracycline, potassium dichromate and sodium arsenate were added to the biological conversion reactor in the amount of 10 mg/L respectively, and then stirred under an anaerobic condition for 6 days with the pH value controlled to 11 and a culture temperature to 80° C. 
     3) Stage 2 of biological conversion: potassium nitrate was added to a product of the biological conversion to 50 mg/L, and  Pseudomonas  and  Shewanella  were then added, where a dry weight ratio of  Pseudomonas  to the second urban organic waste was 0.001:100, and a dry weight ratio of  Shewanella  to the second urban organic waste was 0.001:100; the above mixture was stirred for 6 days and then solid-liquid separation was performed and then the concentrations of lactic acid, tetracycline, sulfadiazine, chromium ions and arsenic ions in the liquid phase were analyzed, and the concentrations of tetracycline, sulfadiazine, chromium ions and arsenic ions in the solid phase were analyzed. 
     As a result, the concentration of lactic acid in the liquid phase was 1071 mg/L, and the removal rates of total sulfadiazine, tetracycline, hexavalent chromium and pentavalent arsenic in the liquid and solid phases were 43%, 36%, 48% and 50% respectively. 
     Embodiment 10, embodiment 11, embodiment 12, and control embodiment 3 are identical to the embodiment 9 except for specific parameters listed in table below. The specific parameters and detection results are shown in table below. 
     
       
         
           
               
               
               
               
               
               
               
             
               
                   
               
               
                   
                   
                   
                   
                   
                   
                 Control 
               
               
                   
                   
                 Embodiment 
                 Embodiment 
                 Embodiment 
                 Embodiment 
                 embodiment 
               
               
                 Stage 
                 Index 
                 9 
                 10 
                 11 
                 12 
                 3 
               
               
                   
               
             
            
               
                 Acclimation 
                 dry weight 
                 1:9 
                 1:9 
                 1:9 
                 1:9 
                 1:9 
               
               
                 stage 
                 ratio of the 
               
               
                   
                 sludge to the 
               
               
                   
                 first urban 
               
               
                   
                 organic waste 
               
               
                   
                 concentration 
                 3000 
                 3000 
                 600 
                 600 
                 50 
               
               
                   
                 of acetic acid 
               
               
                   
                 in the mixture/ 
               
               
                   
                 mg/L 
               
               
                   
                 concentration 
                 10000 
                 10000 
                 8000 
                 8000 
                 2000 
               
               
                   
                 of solid in the 
               
               
                   
                 mixture/mg/L 
               
               
                   
                 Acclimation pH 
                 11 
                 11 
                 6.5 
                 8 
                 4 
               
               
                   
                 acclimation 
                 80 
                 80 
                 25 
                 25 
                 5 
               
               
                   
                 temperature/° C. 
               
               
                   
                 acclimation 
                 46 
                 43 
                 38 
                 35 
                 42 
               
               
                   
                 time/d 
               
               
                 Stage 1 of 
                 dry weight 
                  30:100 
                  30:100 
                  8:100 
                  8:100 
                  0.5:100 
               
               
                 biological 
                 ratio of the 
               
               
                 conversion 
                 acclimatized 
               
               
                   
                 sludge to the 
               
               
                   
                 second urban 
               
               
                   
                 organic waste 
               
               
                   
                 solid 
                 70000 
                 70000 
                 30000 
                 30000 
                 5000 
               
               
                   
                 concentration/ 
               
               
                   
                 mg/L 
               
               
                   
                 culture pH 
                 11 
                 11 
                 6.5 
                 6.5 
                 4 
               
               
                   
                 culture 
                 80 
                 80 
                 25 
                 25 
                 5 
               
               
                   
                 temperature/° C. 
               
               
                   
                 culture time/d 
                 6 
                 6 
                 1 
                 2 
                 1 
               
               
                 Stage 2 of 
                 nitrate and 
                 potassium 
                 potassium 
                 sodium 
                 sodium 
                 — 
               
               
                 biological 
                 concentration/ 
                 nitrate 
                 nitrate 
                 nitrate 
                 nitrate 
               
               
                 conversion 
                 mg/L 
                 50 
                 50 
                 22 
                 22 
               
               
                   
                 dry weight 
                   Pseudomonas / 
                   Pseudomonas / 
                 
                   paracoccus 
                 
                 
                   paracoccus 
                 
               
               
                   
                 ratio of the 
                 0.001:100 
                 20:100 
                   denitrificans / 
                   denitrificans / 
               
               
                   
                 bacteria to the 
                   
                   
                 0.4:100 
                 0.4:100 
               
               
                   
                 second urban 
                   Shewanella / 
                   Geobacter / 
                   Geobacter / 
                   Shewanella / 
               
               
                   
                 organic waste 
                 0.001:100 
                 20:100 
                 1:100 
                 1:100 
               
               
                   
                 continued 
                 6 
                 6 
                 1 
                 2 
               
               
                   
                 conversion 
               
               
                   
                 time/d 
               
               
                 Product 
                 propanoic 
                 1071 
                 936 
                 1482 
                 2407 
                 548 
               
               
                   
                 acid/mg/L 
               
               
                   
                 sulfadiazine 
                 43 
                 41 
                 73 
                 90 
                 22 
               
               
                   
                 removal rate/% 
               
               
                   
                 tetracycline 
                 36 
                 35 
                 74 
                 86 
                 18 
               
               
                   
                 removal rate/% 
               
               
                   
                 chromium 
                 48 
                 45 
                 78 
                 92 
                 28 
               
               
                   
                 removal rate/% 
               
               
                   
                 arsenic 
                 50 
                 41 
                 80 
                 89 
                 34 
               
               
                   
                 removal rate/% 
               
               
                   
               
            
           
         
       
     
     Embodiment 13 
     The method of reducing and controlling a hazardous substance in a process of high-value biological conversion of an urban organic waste in the embodiment includes the following steps. 
     1) Acclimation stage: a residual sludge of a wastewater treatment plant, the first urban organic waste, lactic acid and water were placed in a biological acclimation reactor and mixed uniformly, where a dry weight ratio of the sludge to the first urban organic waste was 1:7, a concentration of a solid in the mixture was 10000 mg/L, a concentration of lactic acid in the mixture was 3000 mg/L; a pH value in the acclimation reactor was maintained as 11 and a temperature was maintained as 80° C., and a concentration of lactic acid in the acclimation reactor was measured each day; when the concentration of lactic acid in the reactor no longer increased noticeably over time, the above operations were performed again; through acclimation of 46 d, an acclimatized sludge (VS-L) was obtained. 
     2) Stage 1 of biological conversion: the second urban organic waste and the acclimatized sludge (VS-L) were added to a biological conversion reactor and mixed uniformly, where a dry weight ratio of VS-L to the second urban organic waste was 30:100; water was added until the concentration of a solid in the biological conversion reactor was 70000 mg/L; sulfadiazine, tetracycline, potassium dichromate and sodium arsenate were added to the biological conversion reactor in the amount of 10 mg/L respectively, and then stirred under an anaerobic condition for 6 days with the pH value controlled to 11 and a culture temperature to 80° C. 
     3) Stage 2 of biological conversion: potassium nitrate was added to a product of the biological conversion to 50 mg/L, and  Pseudomonas  and  Shewanella  were then added, where a dry weight ratio of  Pseudomonas  to the second urban organic waste was 0.001:100, and a dry weight ratio of  Shewanella  to the second urban organic waste was 0.001:100; the above mixture was stirred for 6 days and then solid-liquid separation was performed and then the concentrations of lactic acid, tetracycline, sulfadiazine, chromium ions and arsenic ions in the liquid phase were analyzed, and the concentrations of tetracycline, sulfadiazine, chromium ions and arsenic ions in the solid phase were analyzed. 
     As a result, the concentration of lactic acid in the liquid phase was 948 mg/L, and the removal rates of total sulfadiazine, tetracycline, hexavalent chromium and pentavalent arsenic in the liquid and solid phases were 36%, 30%, 37% and 41% respectively. 
     Embodiment 14 
     The method of reducing and controlling a hazardous substance in a process of high-value biological conversion of an urban organic waste in the embodiment includes the following steps. 
     1) Acclimation stage: a residual sludge of a wastewater treatment plant, the first urban organic waste, lactic acid and water were placed in a biological acclimation reactor and mixed uniformly, where a dry weight ratio of the sludge to the first urban organic waste was 1:11, a concentration of a solid in the mixture was 10000 mg/L, a concentration of lactic acid in the mixture was 3000 mg/L; a pH value in the acclimation reactor was maintained as 11 and a temperature was maintained as 80° C., and a concentration of lactic acid in the acclimation reactor was measured each day; when the concentration of lactic acid in the reactor no longer increased noticeably over time, the above operations were performed again; through acclimation of 46d, an acclimatized sludge (VS-L) was obtained. 
     2) Stage 1 of biological conversion: the second urban organic waste and the acclimatized sludge (VS-L) were added to a biological conversion reactor and mixed uniformly, where a dry weight ratio of VS-L to the second urban organic waste was 30:100; water was added until the concentration of a solid in the biological conversion reactor was 70000 mg/L; sulfadiazine, tetracycline, potassium dichromate and sodium arsenate were added to the biological conversion reactor in the amount of 10 mg/L respectively, and then stirred under an anaerobic condition for 6 days with the pH value controlled to 11 and a culture temperature to 80° C. 
     3) Stage 2 of biological conversion: potassium nitrate was added to a product of the biological conversion to 50 mg/L, and  Pseudomonas  and  Shewanella  were then added, where a dry weight ratio of  Pseudomonas  to the second urban organic waste was 0.001:100, and a dry weight ratio of  Shewanella  to the second urban organic waste was 0.001:100; the above mixture was stirred for 6 days and then solid-liquid separation was performed and then the concentrations of lactic acid, tetracycline, sulfadiazine, chromium ions and arsenic ions in the liquid phase were analyzed, and the concentrations of tetracycline, sulfadiazine, chromium ions and arsenic ions in the solid phase were analyzed. 
     As a result, the concentration of lactic acid in the liquid phase was 981 mg/L, and the removal rates of total sulfadiazine, tetracycline, hexavalent chromium and pentavalent arsenic in the liquid and solid phases were 40%, 32%, 43% and 46% respectively. 
     The above embodiments are merely intended to illustrate the principle and efficacies of the present invention rather than limit the present invention. Any modification or change may be made to the above embodiments by those skilled in the art without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by persons of ordinary skill in the prior art without departing from the spirit and technical idea of the present invention shall all be covered by the claims of the present invention.