CN113233727B - Method for enhancing rapid cell lysis of excess sludge by using compound biological enzyme - Google Patents
Method for enhancing rapid cell lysis of excess sludge by using compound biological enzyme Download PDFInfo
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Abstract
The invention discloses a method for enhancing rapid cell lysis of excess sludge by using compound biological enzyme, and relates to the field of excess sludge treatment. The invention aims to solve the technical problems of low anaerobic digestion hydrolysis rate and low efficiency of the existing excess sludge, high energy consumption of the pretreatment method and large medicament input amount. The method comprises the following steps: firstly, filtering and detecting residual sludge; secondly, calculating the adding amount of the hydrolase; thirdly, pretreating the excess sludge; fourthly, adding part of protease; fifthly, adding amylase and cellulase; sixthly, adding lysozyme; seventhly, adding protease again. The method has simple operation, obviously improved hydrolysis effect, no generation of any toxic and harmful substance in the treatment process, and no negative influence on the subsequent anaerobic fermentation biological process. The invention is used for treating excess sludge.
Description
Technical Field
The invention relates to the field of excess sludge treatment.
Background
The sewage treatment capacity of urban sewage treatment plants in China is continuously increased, the total amount of generated residual sludge is continuously increased, the sludge is rich in a large amount of organic matters and rich in carbon source resources, and the recycling and energy utilization of the sludge are urgently realized by adopting a proper treatment mode. The anaerobic treatment is a most widely used method for recycling and stabilizing excess sludge internationally, which not only solves the problem of sludge environmental pollution, but also can recover resources such as methane, organic fertilizer and the like, and promotes the recycling efficiency of the sludge. The hydrolysis process becomes the rate-limiting step of anaerobic fermentation due to the complex components of the excess sludge, difficult degradation and long hydrolysis process. The method can realize the rapid and efficient hydrolysis of the organic particles in the excess sludge, is cheap, economical and highly applicable, and becomes a research hotspot problem in the field of biological treatment and recycling of the sludge at present.
The current main pretreatment methods of the excess sludge comprise physical methods such as high temperature and ultrasonic treatment, chemical methods such as acid-base treatment and advanced oxidation, biological methods such as adding biological enzyme and microbial agent, and microwave-H2O2Combined use, ultrasonic-alkali combined use and the like. The physical method generally achieves the purposes of destroying the EPS structure and the cell integrity by inputting a large amount of energy from the outside and crushing macromolecular organic matters into micromolecular organic matters, and the energy consumption is large. The chemical method generally damages chemical bonds by adding chemical reagents to react with EPS and cells, but influences the normal life activities of microorganisms and influences the operation of the subsequent anaerobic digestion process. The coupling method has better treatment effectBut generally needs additional sludge treatment facilities and equipment, and has higher cost and complex operation. The biological enzyme has the advantages of high-efficiency catalytic activity, thorough hydrolysis specificity, strong environment adaptability and the like, and adopts a complex enzyme lysis hydrolysis method of a hydrolysis process in which multiple enzymes participate together, so that the hydrolysis effects of different enzymes can be exerted, targeted hydrolysis is carried out according to different components in EPS, microbial cell walls can be decomposed, intracellular substances are dissolved out, the content of micromolecular organic matters in supernatant is further increased, and raw materials are provided for the subsequent process of anaerobic fermentation. However, at present, the selection and dosage of enzyme in the enzymatic pretreatment are usually performed according to a given dosage mode, and are not adjusted according to different properties of EPS components, so that when the residual sludge components from different sources have large differences, the addition ratio of the fixed exogenous hydrolase cannot effectively improve the sludge hydrolysis effect, and waste is easily caused.
Disclosure of Invention
The invention provides a method for strengthening rapid lysis of excess sludge by using compound biological enzyme, aiming at solving the technical problems of slow anaerobic digestion hydrolysis rate, low efficiency, high energy consumption of pretreatment method, high medicine consumption and large medicine input amount of the existing excess sludge.
A method for enhancing rapid cell lysis of excess sludge by using compound biological enzyme comprises the following steps:
filtering residual sludge in a secondary sedimentation tank of a sewage plant to remove impurities, and then adjusting the concentration of the residual sludge VSS to be 7-8 g/L; extracting residual sludge EPS, and determining COD value as EPS total amount in mg/L, protein content PN in mg/L, polysaccharide content PS in mg/L and cellulose content C in mg/L;
secondly, determining the adding amount of the hydrolase according to the result measured in the step one:
controlling the total dosage of the hydrolase to be 150-170 mg/gVSS;
determining the adding amount of lysozyme according to the proportion of the total EPS amount in VSS, wherein the unit of EPS/VSS is mgCOD/gVSS; when EPS/VSS is less than 50, the adding amount of lysozyme is 55 percent of the total adding amount of hydrolase; when the EPS/VSS is more than or equal to 50 and less than 100, the adding amount of the lysozyme is 50 percent of the total adding amount of the hydrolase; when the EPS/VSS is more than or equal to 100 and less than 200, the adding amount of the lysozyme is 45 percent of the total adding amount of the hydrolase; when the EPS/VSS is more than or equal to 200, the adding amount of the lysozyme is 40 percent of the total adding amount of the hydrolase;
determining the adding amount ratio of the protease to the polysaccharose according to the content ratio of the protein to the polysaccharide in the EPS, wherein when PN/PS is less than 1, the adding amount ratio of the protease to the polysaccharose is 1: 1; when the ratio of PN/PS is more than or equal to 1 and less than 1.5, the adding amount ratio of the protease to the polysaccharose enzyme is 2: 1; when PN/PS is more than or equal to 1.5 and less than 3, the adding amount ratio of the protease to the polysaccharose enzyme is 3: 1; when PN/PS is more than or equal to 3, the adding amount ratio of the protease to the polysaccharose enzyme is 6: 1;
determining the adding amount ratio of amylase to cellulase according to the content ratio of cellulose to polysaccharide in EPS, wherein when C/PS is less than 0.2, the adding amount ratio of amylase to cellulase is 2: 1; when C/PS is more than or equal to 0.2 and less than 0.5, the adding amount ratio of amylase to cellulase is 1: 1; when the C/PS is more than or equal to 0.5, the adding amount ratio of the amylase to the cellulase is 1: 2;
the hydrolase is lysozyme, protease, amylase and cellulase;
the polysaccharidase is amylase and cellulase;
thirdly, adjusting the pH value of the filtered excess sludge to be 5.5-7, controlling the temperature to be 40-60 ℃, and preserving the temperature for 45-75 min;
fourthly, adding protease into the excess sludge treated in the third step, wherein the adding amount of the protease is 50% of the adding amount calculated in the second step, stirring, and hydrolyzing for 0.5-1.5 h;
fifthly, adding amylase and cellulase into the excess sludge treated in the step four, wherein the adding amount of the amylase and the cellulase is calculated in the step two, stirring, and hydrolyzing for 0.5-1.5 h;
sixthly, adding lysozyme into the excess sludge treated in the step five, wherein the adding amount of the lysozyme is calculated in the step two, stirring and hydrolyzing for 1.5-2.5 h;
seventhly, adding protease into the excess sludge treated in the step six, wherein the adding amount of the protease is 50% of the adding amount calculated in the step two, stirring, and hydrolyzing for 1.5-2.5 h; and (4) finishing.
Extracting residual sludge EPS in the first step by adopting an EDTA method, namely adding a sludge sample into a 2% EDTA solution, performing oscillation extraction at 20 ℃ for 5 hours, centrifuging, and passing the supernatant through a 0.45-micrometer membrane to obtain the EPS; COD is measured as the total EPS amount, and the COD measuring method adopts a rapid digestion method with the unit of mg/L. The microbial flora present in the excess sludge is detected at the phylum level using a high throughput method. And (3) determining the protein content PN, the polysaccharide content PS, the cellulose content C and the cellulose content mg/L in the EPS, wherein the protein content is determined by adopting a Lowry method or a modified Bradford method, the polysaccharide content is determined by adopting a phenol-sulfuric acid method, and the cellulose content is determined by adopting a paradigm washing method. This step detects the basic properties of the excess sludge and the main component composition of EPS.
And step three, providing the most suitable reaction condition for the hydrolase, improving the hydrolysis efficiency and increasing the SCOD content after hydrolysis.
And step four, adding protease to destroy the protein skeleton structure in the EPS, and scattering the EPS structure to prepare for the subsequent hydrolysis of other enzymes.
And step five, adding amylase and cellulase for further destroying cross-linked polysaccharide substances in the EPS, and disassembling the EPS to prepare for the subsequent hydrolysis of other enzymes. Since the protease in step four has already destroyed the EPS backbone, the polysaccharides in EPS are more easily contacted with the hydrolase, thereby better destroying the cross-linked polysaccharides. The protease and polysaccharose enzyme combination (amylase and cellulase) is separately added, so that the influence can be avoided, the activity of the polysaccharose enzyme combination is ensured, polysaccharide substances in EPS can be fully hydrolyzed, and the subsequent lysozyme can reach an action site conveniently.
Step six, lysozyme is added, the action site of the lysozyme is positioned on the bacterial cell wall, the cell wall is hydrolyzed by destroying beta-1, 4 glycosidic bond between N-acetylmuramic acid and N-acetylglucosamine in the cell wall of gram-positive bacteria, microorganisms absorb water under the action of osmotic pressure to swell and break, and intracellular substances are further released into the supernatant. The released intracellular material will provide a portion of the degradable organic material as a substrate for the hydrolysis process; at the same time, intracellular enzyme fluid is released, providing more tools for hydrolysis. The two factors influence together, so that the hydrolysis effect is improved, and more substrates can be provided for subsequent anaerobic fermentation. Compared with other pretreatment methods, after the steps of four and five, the method has the advantages that the EPS structure of the residual sludge is damaged and part of the residual sludge is dissolved into the supernatant, lysozyme can easily pass through the EPS to reach the action site, the hydrolysis efficiency is improved, the cost is reduced, and more substrates and intracellular enzymes can be released into the supernatant for the subsequent steps of anaerobic digestion.
And seventhly, adding the protease again can further hydrolyze protein substances in the EPS and can hydrolyze a large amount of organic matters released from cells, so that the hydrolysis effect is enhanced to the maximum extent, and the SCOD is improved.
In the method, protease, amylase and cellulase are selected based on main components for hydrolyzing main substrate Extracellular Polymeric Substance (EPS), and three hydrolases are utilized to specifically remove main components of protein and polysaccharide substances of EPS. The lysozyme is proved to be the hydrolase with the best hydrolysis strengthening effect through experiments, so the lysozyme is selected as the core hydrolase for strengthening hydrolysis in the method.
The invention selects the combination of amylase, cellulase, protease and lysozyme for adding according to the composition of residual sludge EPS. And determining the total adding amount and the adding amount proportion of the four enzymes according to the basic properties of the residual sludge. A new strategy of complex cell lysis of various hydrolases is provided, the adding sequence, adding time and the like of four enzymes are optimized, and the residual sludge is pretreated under the condition of the optimal environmental factors (pH, temperature, stirring intensity and the like), so that the cell lysis efficiency of the enzymes is improved, the total adding amount of the enzymes is reduced, and the hydrolysis effect is enhanced.
The invention has the beneficial effects that:
according to the invention, according to the composition of extracellular polymers and the hydrolysis effect difference of different biological enzymes, the biological enzymes are reasonably selected and the adding mode is determined, the cell lysis of the biological enzyme method is utilized to promote the rapid hydrolysis of organic particles of excess sludge, insoluble macromolecular organic matters in a sludge solid phase are degraded into soluble micromolecular organic matters through enzyme catalysis, and a large amount of organic substrates are provided for the subsequent anaerobic fermentation subsequent process through the 'dissolution' of the organic matters of the excess sludge. The method does not introduce acid-base agents, does not need energy input except mixing and stirring, does not generate negative influence on subsequent microbial anaerobic fermentation, improves the substrate concentration of the hydrolyzed sludge, and is green, environment-friendly and low in cost.
Compared with other physical, chemical and coupling combined methods, the method has the advantages of low energy consumption, small dosage, no generation of other by-products and environmental friendliness. Compared with other methods for enhancing hydrolysis by enzyme method, the method calculates the enzyme dosage according to the basic properties of the excess sludge, and has wide application range and strong pertinence; the proportion and the adding mode (adding sequence and adding time) of different hydrolytic enzymes are reasonably adjusted, so that the hydrolysis effect can be improved, and the cost can be reduced.
After measurement and calculation, after the excess sludge is treated by the method, the SCOD of the supernatant is over 12000mg/L, is 255% of a blank group, is 154% of medium-temperature pyrohydrolysis treatment (80 ℃, 6h), is 122% of ultrasonic treatment (1.5W/ml, 6h), is 141% of independently added protease with the same amount (160mg/gVSS, the stirring intensity is 200rpm, and the reaction time is 6h), is 151% of independently added alpha-amylase with the same amount (1160mg/gVSS, the stirring intensity is 200rpm, and the reaction time is 6h), is 152% of independently added cellulase with the same amount (160mg/gVSS, the stirring intensity is 200rpm, and the reaction time is 6h), and is 135% of independently added lysozyme (160mg/gVSS, the stirring intensity is 200rpm, and the reaction time is 6 h). The method has simple operation, obviously improved hydrolysis effect, no generation of any toxic and harmful substance in the treatment process, and no negative influence on the subsequent anaerobic fermentation biological process.
The invention is used for treating excess sludge.
Detailed Description
The technical solution of the present invention is not limited to the specific embodiments listed below, and includes any combination of the specific embodiments.
The first embodiment is as follows: the embodiment provides a method for enhancing rapid cell lysis of excess sludge by using composite biological enzyme, which specifically comprises the following steps:
filtering residual sludge in a secondary sedimentation tank of a sewage plant to remove impurities, and adjusting the concentration of the residual sludge VSS to be 7-8 g/L; extracting residual sludge EPS, and determining COD value as EPS total amount in mg/L, protein content PN in mg/L, polysaccharide content PS in mg/L and cellulose content C in mg/L;
secondly, determining the adding amount of the hydrolase according to the result measured in the step one:
controlling the total dosage of the hydrolase to be 150-170 mg/gVSS;
determining the adding amount of lysozyme according to the proportion of the total EPS amount in VSS, wherein the unit of EPS/VSS is mgCOD/gVSS; when EPS/VSS is less than 50, the adding amount of lysozyme is 55 percent of the total adding amount of hydrolase; when the EPS/VSS is more than or equal to 50 and less than 100, the adding amount of the lysozyme is 50 percent of the total adding amount of the hydrolase; when the EPS/VSS is more than or equal to 100 and less than 200, the adding amount of the lysozyme is 45 percent of the total adding amount of the hydrolase; when the EPS/VSS is more than or equal to 200, the adding amount of the lysozyme is 40 percent of the total adding amount of the hydrolase;
determining the adding amount ratio of the protease to the polysaccharose according to the content ratio of the protein to the polysaccharide in the EPS, wherein when PN/PS is less than 1, the adding amount ratio of the protease to the polysaccharose is 1: 1; when the ratio of PN/PS is more than or equal to 1 and less than 1.5, the adding amount ratio of the protease to the polysaccharose enzyme is 2: 1; when PN/PS is more than or equal to 1.5 and less than 3, the adding amount ratio of the protease to the polysaccharose enzyme is 3: 1; when PN/PS is more than or equal to 3, the adding amount ratio of the protease to the polysaccharose enzyme is 6: 1;
determining the adding amount ratio of amylase to cellulase according to the content ratio of cellulose to polysaccharide in EPS, wherein when C/PS is less than 0.2, the adding amount ratio of amylase to cellulase is 2: 1; when C/PS is more than or equal to 0.2 and less than 0.5, the adding amount ratio of amylase to cellulase is 1: 1; when the C/PS is more than or equal to 0.5, the adding amount ratio of the amylase to the cellulase is 1: 2;
the hydrolase is lysozyme, protease, amylase and cellulase;
the polysaccharidase is amylase and cellulase;
thirdly, adjusting the pH value of the filtered excess sludge to be 5.5-7, controlling the temperature to be 40-60 ℃, and preserving the temperature for 45-75 min;
fourthly, adding protease into the excess sludge treated in the third step, wherein the adding amount of the protease is 50% of the adding amount calculated in the second step, stirring, and hydrolyzing for 0.5-1.5 h;
fifthly, adding amylase and cellulase into the excess sludge treated in the step four, wherein the adding amount of the amylase and the cellulase is calculated in the step two, stirring, and hydrolyzing for 0.5-1.5 h;
sixthly, adding lysozyme into the excess sludge treated in the step five, wherein the adding amount of the lysozyme is calculated in the step two, stirring and hydrolyzing for 1.5-2.5 h;
seventhly, adding protease into the excess sludge treated in the step six, wherein the adding amount of the protease is 50% of the adding amount calculated in the step two, stirring, and hydrolyzing for 1.5-2.5 h; and (4) finishing.
The second embodiment is as follows: the first difference between the present embodiment and the specific embodiment is: and step one, filtering by adopting a screen. The rest is the same as the first embodiment.
The third concrete implementation mode: the present embodiment differs from the first or second embodiment in that: the mesh of the screen is larger than 10 meshes. The other is the same as in the first or second embodiment.
The fourth concrete implementation mode: the difference between this embodiment mode and one of the first to third embodiment modes is: and step three, adjusting the pH value to 6.5, controlling the temperature to be 50 ℃, and preserving the temperature for 60 min. The others are the same as in one of the first to third embodiments.
The fifth concrete implementation mode: the difference between this embodiment and one of the first to fourth embodiments is: and step four, controlling the stirring speed to be 150-300 r/min. The other is the same as one of the first to fourth embodiments.
The sixth specific implementation mode: the difference between this embodiment and one of the first to fifth embodiments is: step four, the protease is generated by fermenting bacillus subtilis, and the activity is 50000U/mg. The other is the same as one of the first to fifth embodiments.
The seventh embodiment: the difference between this embodiment and one of the first to sixth embodiments is: and step four, controlling the pH value of hydrolysis to be 5.5-6.5. The other is the same as one of the first to sixth embodiments.
The specific implementation mode is eight: the present embodiment differs from one of the first to seventh embodiments in that: and fifthly, the amylase is generated by fermenting the bacillus subtilis, the amylase activity is 3700U/g, the cellulase is obtained by inoculating spore liquid to cellulose and then fermenting, and the cellulase activity is 50U/mg. The other is the same as one of the first to seventh embodiments.
The specific implementation method nine: the present embodiment differs from the first to eighth embodiments in that: and fifthly, controlling the pH value of hydrolysis to be 6.0-6.5. The rest is the same as the first to eighth embodiments.
The detailed implementation mode is ten: the present embodiment differs from one of the first to ninth embodiments in that: sixthly, the lysozyme is extracted and purified from egg white, and the activity is 20000U/mg. The other is the same as one of the first to ninth embodiments.
The following examples were used to demonstrate the beneficial effects of the present invention:
the first embodiment is as follows:
the excess sludge adopted by the embodiment is the excess sludge of a secondary sedimentation tank of a common municipal sewage treatment plant;
a method for enhancing rapid cell lysis of excess sludge by using compound biological enzyme comprises the following steps:
filtering residual sludge in a secondary sedimentation tank of a sewage plant to remove impurities, wherein the aperture of a screen is 0.71mm, and then adjusting the VSS concentration of the residual sludge to 7.2 +/-0.5 g/L; extracting residual sludge EPS, and determining COD value as EPS total amount, protein content PN, polysaccharide content PS and cellulose content C;
the EPS is measured to be 489.6 mg/L; PN is 201.6 mg/L; PS is 115.2 mg/L; c is 32.4 mg/L;
secondly, determining the adding amount of the hydrolase according to the result measured in the step one:
controlling the total dosage of the hydrolase to be 160 mg/gVSS;
determining the adding amount of lysozyme according to the proportion of the total EPS amount in VSS, wherein the unit of EPS/VSS is mgCOD/gVSS; when EPS/VSS is less than 50, the adding amount of lysozyme is 55 percent of the total adding amount of hydrolase; when the EPS/VSS is more than or equal to 50 and less than 100, the adding amount of the lysozyme is 50 percent of the total adding amount of the hydrolase; when the EPS/VSS is more than or equal to 100 and less than 200, the adding amount of the lysozyme is 45 percent of the total adding amount of the hydrolase; when the EPS/VSS is more than or equal to 200, the adding amount of the lysozyme is 40 percent of the total adding amount of the hydrolase;
the ratio of the total EPS amount in VSS is calculated to be 68mgCOD/gVSS, namely the adding amount of lysozyme is 50 percent of the total adding amount of hydrolase;
determining the adding amount ratio of the protease to the polysaccharose according to the content ratio of the protein to the polysaccharide in the EPS, wherein when PN/PS is less than 1, the adding amount ratio of the protease to the polysaccharose is 1: 1; when the ratio of PN/PS is more than or equal to 1 and less than 1.5, the adding amount ratio of the protease to the polysaccharose enzyme is 2: 1; when PN/PS is more than or equal to 1.5 and less than 3, the adding amount ratio of the protease to the polysaccharose enzyme is 3: 1; when PN/PS is more than or equal to 3, the adding amount ratio of the protease to the polysaccharose enzyme is 6: 1;
the calculated PN/PS is 1.75, namely the dosage ratio of the protease to the polysaccharose enzyme is 3: 1;
determining the adding amount ratio of amylase to cellulase according to the content ratio of cellulose to polysaccharide in EPS, wherein when C/PS is less than 0.2, the adding amount ratio of amylase to cellulase is 2: 1; when C/PS is more than or equal to 0.2 and less than 0.5, the adding amount ratio of amylase to cellulase is 1: 1; when the C/PS is more than or equal to 0.5, the adding amount ratio of the amylase to the cellulase is 1: 2;
C/PS is calculated to be 0.28, namely the adding amount ratio of amylase to cellulase is 1: 1;
the hydrolase is lysozyme, protease, amylase and cellulase;
the polysaccharidase is amylase and cellulase;
through calculation: the total dosage of the hydrolytic enzyme is 160mg/gVSS, the dosage of the lysozyme is 80mg/gVSS, the dosage of the protease is 60mg/gVSS, the dosage of the amylase is 10mg/gVSS, and the dosage of the cellulase is 10 mg/gVSS;
thirdly, adjusting the pH value of the filtered excess sludge to 6.5, controlling the temperature to be 50 ℃, and preserving the temperature for 60 min;
fourthly, adding protease into the excess sludge treated in the third step, wherein the adding amount of the protease is 30mg/gVSS, and stirring and hydrolyzing for 1h at the stirring speed of 200 r/min;
fifthly, adding amylase and cellulase into the excess sludge treated in the step four, adjusting the pH value of the excess sludge to 6.5 before adding, calculating the adding amount of the amylase and the cellulase in the step two, and stirring and hydrolyzing for 1h at the stirring speed of 200 r/min; the amylase is alpha-amylase;
sixth, lysozyme is added into the excess sludge treated in the fifth step, the pH value of the excess sludge is adjusted to 6.5 before the lysozyme is added, the adding amount of the lysozyme is calculated in the second step, and the stirring speed is controlled to be 200r/min, and stirring and hydrolysis are carried out for 2 hours;
seventhly, adding protease into the excess sludge treated in the step six, adjusting the pH value of the excess sludge to 6.5 before adding, wherein the adding amount of the protease is 30mg/gVSS, and stirring and hydrolyzing for 2 hours at the stirring speed of 200 r/min; and (4) finishing.
The protease used in this example was produced by fermentation of Bacillus subtilis with an activity of 50000U/mg and an optimum pH of 6.0-7.0; the alpha-amylase is generated by fermenting bacillus subtilis, the activity is 3700U/g, and the optimal pH value is 6.0-7.0; the cellulase is obtained by inoculating cellulose substances (such as straw powder, waste paper pulp, wheat straw, corn stalk powder, bran, etc.) into spore liquid and fermenting, and has activity of 50U/mg and optimum pH of 4.5-6.5; the lysozyme activity is 20000U/mg.
Comparative experiment:
blank control, medium-temperature thermal hydrolysis treatment, ultrasonic treatment, independent protease feeding, independent alpha-amylase feeding, independent cellulase feeding and independent lysozyme feeding are respectively adopted as comparison experiments.
Blank control, not carrying out any treatment on the excess sludge;
medium-temperature thermal hydrolysis treatment: the reaction temperature is 50 ℃, and the reaction time is 6 hours;
ultrasonic treatment: the acoustic density is: 1500W/L, the reaction time is 6 h;
adding protease independently: the dosage is 160mg/gVSS, the stirring intensity is 200rpm, and the reaction time is 6 h;
the alpha-amylase is independently added: the dosage is 160mg/gVSS, the stirring intensity is 200rpm, and the reaction time is 6 h;
and (3) independently adding cellulase: the dosage is 160mg/gVSS, the stirring intensity is 200rpm, and the reaction time is 6 h;
separately adding lysozyme: the dosage is 160mg/gVSS, the stirring intensity is 200rpm, and the reaction time is 6 h.
The treatment effects of the examples and comparative experiments are shown in table 1:
TABLE 1 comparison of the results of this example with comparative test methods
| Excess sludge treatment method | COD concentration (mg/L) of the supernatant after treatment |
| Blank control | 5043 |
| Optimal scheme of the method | 12871 |
| Medium temperature pyrohydrolysis | 8328 |
| Ultrasonic treatment | 10549 |
| Separate addition of protease | 9154 |
| Separate addition of alpha-amylase | 8536 |
| Single addition of cellulase | 8448 |
| Separately adding lysozyme | 9561 |
As can be seen from the table, the reaction was carried out in this example, the SCOD of the supernatant was 12000mg/L or more, and the result was 255% of the blank group, 154% of the medium-temperature pyrohydrolysis treatment (80 ℃, 6h), 122% of the ultrasonic treatment (1.5W/ml, 6h), 141% of the protease (160mg/gVSS, agitation intensity of 200rpm, reaction time of 6h) added in an amount equal to that of the ultrasonic treatment, 151% of the alpha-amylase (1160mg/gVSS, agitation intensity of 200rpm, reaction time of 6h) added in an amount equal to that of the ultrasonic treatment, 152% of the cellulase (160mg/gVSS, agitation intensity of 200rpm, reaction time of 6h) added in an amount equal to that of the cellulase (160mg/gVSS, agitation intensity of 200rpm, reaction time of 6h) added in an amount equal to that of the lysozyme (160mg/gVSS, agitation intensity of 200rpm, reaction time of 6h) added in an amount equal to that of the ultrasonic treatment. The hydrolysis effect of the method is obviously improved.
Table 2 comparison of different enzyme adding modes (lysozyme adding amount is the best mode under the conditions of the examples)
Note: in the adding mode (time), P0, A0, C0 and L0 respectively represent protease, amylase, cellulase and lysozyme; the different enzymes are connected by a "+" (such as P0+ A0+ C0+ L0) to indicate that several enzymes are added simultaneously; (1h) waiting for the time of hydrolysis after addition of the enzyme; 1/2P0 indicates that the protease is added in an amount of 1/2 calculated as the total amount; "," separate "indicates the order of addition of the hydrolytic enzymes.
TABLE 3 comparison of the treatment effect of different lysozyme dosages in the examples (other enzyme dosages are the best way under the conditions of the examples)
| The lysozyme is added in four enzymesRatio of total input amount | SCOD(mg/L) |
| 55％ | 11069 |
| 50％ | 12871 |
| 45％ | 10127 |
| 40％ | 9795 |
Claims (10)
1. A method for strengthening rapid cell lysis of excess sludge by using compound biological enzyme is characterized by comprising the following steps:
filtering residual sludge in a secondary sedimentation tank of a sewage plant to remove impurities, and adjusting the concentration of the residual sludge VSS to be 7-8 g/L; extracting residual sludge EPS, and determining COD value as EPS total amount in mg/L, protein content PN in mg/L, polysaccharide content PS in mg/L and cellulose content C in mg/L;
secondly, determining the adding amount of the hydrolase according to the result measured in the step one:
controlling the total dosage of the hydrolase to be 150-170 mg/gVSS;
determining the adding amount of lysozyme according to the proportion of the total EPS amount in VSS, wherein the unit of EPS/VSS is mgCOD/gVSS; when EPS/VSS is less than 50, the adding amount of lysozyme is 55 percent of the total adding amount of hydrolase; when the EPS/VSS is more than or equal to 50 and less than 100, the adding amount of the lysozyme is 50 percent of the total adding amount of the hydrolase; when the EPS/VSS is more than or equal to 100 and less than 200, the adding amount of the lysozyme is 45 percent of the total adding amount of the hydrolase; when the EPS/VSS is more than or equal to 200, the adding amount of the lysozyme is 40 percent of the total adding amount of the hydrolase;
determining the adding amount ratio of the protease to the polysaccharose according to the content ratio of the protein to the polysaccharide in the EPS, wherein when PN/PS is less than 1, the adding amount ratio of the protease to the polysaccharose is 1: 1; when the ratio of PN/PS is more than or equal to 1 and less than 1.5, the adding amount ratio of the protease to the polysaccharose enzyme is 2: 1; when PN/PS is more than or equal to 1.5 and less than 3, the adding amount ratio of the protease to the polysaccharose enzyme is 3: 1; when PN/PS is more than or equal to 3, the adding amount ratio of the protease to the polysaccharose enzyme is 6: 1;
determining the adding amount ratio of amylase to cellulase according to the content ratio of cellulose to polysaccharide in EPS, wherein when C/PS is less than 0.2, the adding amount ratio of amylase to cellulase is 2: 1; when C/PS is more than or equal to 0.2 and less than 0.5, the adding amount ratio of amylase to cellulase is 1: 1; when the C/PS is more than or equal to 0.5, the adding amount ratio of the amylase to the cellulase is 1: 2;
the hydrolase is lysozyme, protease, amylase and cellulase;
the polysaccharidase is amylase and cellulase;
thirdly, adjusting the pH value of the filtered excess sludge to be 5.5-7, controlling the temperature to be 40-60 ℃, and preserving the temperature for 45-75 min;
fourthly, adding protease into the excess sludge treated in the third step, wherein the adding amount of the protease is 50% of the adding amount calculated in the second step, stirring, and hydrolyzing for 0.5-1.5 h;
fifthly, adding amylase and cellulase into the excess sludge treated in the step four, wherein the adding amount of the amylase and the cellulase is calculated in the step two, stirring, and hydrolyzing for 0.5-1.5 h;
sixthly, adding lysozyme into the excess sludge treated in the step five, wherein the adding amount of the lysozyme is calculated in the step two, stirring and hydrolyzing for 1.5-2.5 h;
seventhly, adding protease into the excess sludge treated in the step six, wherein the adding amount of the protease is 50% of the adding amount calculated in the step two, stirring, and hydrolyzing for 1.5-2.5 h; and (4) finishing.
2. The method for enhancing the rapid lysis of the excess sludge by using the compound biological enzyme as claimed in claim 1, wherein the first step is a filtration step using a screen.
3. The method for enhancing the rapid lysis of the excess sludge by using the compound biological enzyme as claimed in claim 2, wherein the mesh opening of the screen is larger than 10 meshes.
4. The method of claim 1, wherein the pH value of step three is adjusted to 6.5, the temperature is controlled to 50 ℃, and the temperature is maintained for 60 min.
5. The method for enhancing the rapid lysis of the excess sludge by the compound biological enzyme according to claim 1, wherein the stirring speed in the fourth step is controlled to be 150 to 300 r/min.
6. The method of claim 1, wherein said protease of step four is produced by fermentation of Bacillus subtilis and has an activity of 50000U/mg.
7. The method for enhancing the rapid lysis of the excess sludge by the compound biological enzyme according to claim 1, wherein the pH value of hydrolysis is controlled to be 5.5-6.5 in the fourth step.
8. The method of claim 1, wherein said amylase produced in step five is produced by fermentation of Bacillus subtilis, and has an amylase activity of 3700U/g, and said cellulase is obtained by fermentation after inoculation of spore liquid with cellulose, and has a cellulase activity of 50U/mg.
9. The method for enhancing the rapid lysis of the excess sludge by the compound biological enzyme according to claim 1, wherein the pH value of hydrolysis in step five is controlled to be 6.0-6.5.
10. The method for enhancing the rapid lysis of the excess sludge by using the compound biological enzyme according to claim 1, wherein the lysozyme is extracted and purified from egg white in step six, and the activity is 20000U/mg.
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