METHOD OF REDUCING AND CONTROLLING HAZARDOUS SUBSTANCE IN PROCESS OF HIGH-VALUE BIOLOGICAL CONVERSION OF URBAN ORGANIC WASTE

Abstract

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. The method includes: 1) 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. In the present invention, sludge microbes are acclimatized and then added to high-value chemicals such as acetic acid, propanoic acid and lactic acid prepared in biological conversion of the urban organic waste and then added with bacteria. Thus, by controlling pH value, microbe addition amount and nitrate concentration, the unfavorable effect of the antibiotics and heavy metal ions.

Claims

1. A method of reducing and controlling a hazardous substance in a process of high-value biological conversion of an urban organic waste, comprising 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.

2. The method of claim 1, wherein in step 1), a dry weight ratio of the sludge to the first urban organic waste is 1:(7-11); and/or, the acclimation condition is that a pH value is 4-11, and a temperature is 5° C.-80° C.; and/or, the acid is acetic acid, propanoic acid or lactic acid; and/or, a content of a solid in the mixture formed by mixing is 2000 mg/L-10000 mg/L; and/or, a concentration of the acid in the mixture formed by mixing is 50 mg/L-3000 mg/L.

3. The method of claim 1, wherein in step 2), a dry weight ratio of the acclimatized sludge to the second urban organic waste is (0.5-30):100; and/or, the mixture formed by mixing further comprises water, and a concentration of a solid in the mixture is 5000 mg/L-70000 mg/L.

4. The method of claim 1, wherein in steps 2) and 3), a time of the anaerobic culture is 0.5 d-6 d with a pH value of 4-11 and a temperature of 5° C.-80° C.

5. The method of claim 1, wherein the nitrate is sodium nitrate or potassium nitrate; the bacteria comprise denitrifying bacteria and exoelectrogenic bacteria.

6. The method of claim 5, wherein the denitrifying bacteria comprise Pseudomonas and Paracoccus denitrificans, and the exoelectrogenic bacteria comprise Shewanella and Geobacter.

7. The method of claim 5, wherein an addition amount of the nitrate does not exceed 50 mg/L.

8. The method of claim 5, wherein 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.

9. The method of claim 1, wherein the sludge is a residual sludge of a wastewater treatment plant; and the urban organic waste comprises restaurant garbage and kitchen garbage.

10. The method of claim 1, wherein the organic acid comprises acetic acid, propanoic acid or lactic acid; the hazardous substance comprises heavy metal and antibiotic; the antibiotic comprises tetracycline and sulfanilamide; and the heavy metal ion comprises chromium and arsenic.

Description

BRIEF DESCRIPTIONS OF THE DRAWINGS

[0049] 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

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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

[0060] 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:

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

TABLE-US-00001 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

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

TABLE-US-00002 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

[0072] 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:

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

TABLE-US-00003 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

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.