Composite surfactant for oil sludge treatment and oil sludge treatment method

Abstract

The invention relates to a composite surfactant for oil sludge treatment and an oil sludge treatment method, and belongs to the technical field of solid waste treatment. According to the invention, the mixed sludge mixed with the oily sludge and the Fenton iron sludge can be uniformly treated, so that the sludge treatment effect is greatly improved, and the sludge treatment cost is reduced. The composite surfactant comprises a biological surfactant, a chemical surfactant and an auxiliary agent, the biological surfactant is rhamnolipid and sophorolipid, the chemical surfactant is sodium dodecyl benzene sulfonate, and the auxiliary agent is sodium silicate.

Description

Technical Field

[0001] The present application belongs to the technical field of solid waste treatment, and in particular, relates to a composite surfactant and an oil sludge treatment method. Background Art

[0002] Oily sludge refers to sludge mixed with heavy oils such as crude oil, various refined oils, and residual oil. A large amount of oily sludge is produced during the storage of petrochemical products. This oily sludge contains a large amount of petroleum hydrocarbons, asphaltene and other petroleum substances, as well as a large amount of chemicals, heavy metals and other harmful components, which cause serious harm to the areas around the discharge site and is one of the main pollutants in the petroleum and petrochemical industries. Therefore, the treatment of oily sludge is a very important task.

[0003] In addition, Fenton iron sludge refers to the byproduct generated during the treatment of wastewater using the Fenton process. The Fenton process uses hydrogen peroxide (H 2 O 2 ) and divalent iron (Fe 2+ ) produces highly oxidizing hydroxyl radicals (·OH), thereby oxidizing and degrading organic pollutants in wastewater. However, during the reaction, iron ions will generate a large amount of iron-containing sludge. These precipitates are the so-called Fenton iron sludge, the main component of which is iron hydroxide (Fe(OH) 3 ), iron oxide (Fe 2 O 3 ), iron oxide complexes and free iron ions (Fe 2+ / Fe3 + ). Fenton iron sludge has a large output, is difficult to separate solids and liquids, has a high water content and is difficult to dehydrate. At the same time, harmful substances may remain in the sludge, such as heavy metals and incompletely degraded organic pollutants, which also need to be further stabilized or rendered harmless.

[0004] In the prior art, these two types of sludge are treated separately using independent treatment processes. Specifically, for oily sludge, for example, a cleaning solution containing a surfactant is used to heat wash the oily sludge and then perform solid-liquid separation; for Fenton iron sludge, for example, an anaerobic digestion method is used to feed the Fenton iron sludge and organic matter into a reactor and treat the Fenton iron sludge with microorganisms.

[0005] However, the technology for treating oily sludge and Fenton iron sludge in a unified manner has not yet been developed. Therefore, it is necessary to improve the existing technology.

[0006] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present invention, and therefore it may contain information that does not constitute the prior art known to those skilled in the art. Summary of the invention

[0007] In order to solve one or more of the above problems existing in the prior art, the present invention aims to provide a composite surfactant for oil sludge treatment and an oil sludge treatment method.

[0008] The composite surfactant for oil sludge treatment of the present invention comprises a biological surfactant, a chemical surfactant and an adjuvant, wherein the biological surfactant is rhamnolipid and sophorolipid, the chemical surfactant is sodium dodecylbenzene sulfonate, and the adjuvant is sodium silicate.

[0009] According to an embodiment of the present invention, the mass ratio of the rhamnolipid, the sophorolipid, the sodium silicate, and the sodium dodecylbenzene sulfonate may be 3:3:30:1 to 4:4:40:1.

[0010] According to one embodiment of the present invention, the mass ratio of the biosurfactant to the chemical surfactant may be 6:1, and the mass ratio of the rhamnolipid to the sophorolipid may be 1:1.

[0011] According to an embodiment of the present invention, the mass ratio of the rhamnolipid, the sophorolipid, the sodium silicate, and the sodium dodecylbenzene sulfonate may be 3:3:30:1.

[0012] The present invention also provides an oily sludge treatment method, comprising the following steps: step (i): dissolving the above composite surfactant in water to prepare a cleaning liquid; and step (ii): using the above cleaning liquid to clean mixed sludge under heating conditions, wherein the mixed sludge includes oily sludge and Fenton iron sludge.

[0013] According to an embodiment of the present invention, the mass ratio of the oily sludge to the Fenton iron sludge may be 5:1 to 1:1.

[0014] According to one embodiment of the present invention, in the above step (i), the mass concentration of the above composite surfactant in the above cleaning solution can be 0.4% to 0.8%, and in the above step (ii), the above mixed sludge can be cleaned with the above cleaning solution at a temperature of 40°C to 60°C for 2 to 4 hours, wherein the mass ratio of the above cleaning solution to the above mixed sludge can be 2:1 to 4:1.

[0015] According to one embodiment of the present invention, after the above step (ii), the following step (iii) may also be included: cooling the cleaned mixed sludge to 15°C to 30°C, adding a microbial active composite bacterial agent, and stirring for 2 to 3 hours, wherein the above microbial active composite bacterial agent contains acidophilic ferrothiobacillus and petroleum degrading bacteria.

[0016] According to one embodiment of the present invention, the concentration of the acidithiobacillus ferrooxidans in the microbial active composite bacterial agent may be 6.8×10 8–8.2×10 10 CFU / mL, the above-mentioned petroleum degrading bacteria can be any one of Pseudomonas aeruginosa, Bacillus subtilis, and Nocardia asteroides, or a combination of several of them.

[0017] According to an embodiment of the present invention, the mass ratio of the microbial active composite agent to the mixed sludge may be 1:50 to 1:150.

[0018] Beneficial effects:

[0019] The composite surfactant for oil sludge treatment and the oil sludge treatment method provided by the present invention can uniformly treat mixed sludge containing oily sludge and Fenton iron sludge, greatly improving the sludge treatment effect and reducing the sludge treatment cost. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described in combination with the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. It should be noted that, in the absence of conflict, the embodiments in the present disclosure and the features in the embodiments can be combined, separated, interchanged and / or rearranged with each other. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of this application.

[0021] In addition, the terms used here are for the purpose of describing specific embodiments, and are not intended to be restrictive. As used here, unless the context clearly indicates otherwise, the singular forms "one (kind, person)" and "said (the)" are also intended to include plural forms. In addition, when the terms "comprise" and / or "include" and their variations are used in this specification, it is explained that there are stated features, integral bodies, steps, operations, parts, assemblies and / or their groups, but it is not excluded that there are or add one or more other features, integral bodies, steps, operations, parts, assemblies and / or their groups. It should also be noted that, as used here, the terms "substantially", "approximately" and other similar terms are used as approximate terms and not as degree terms, so that they are used to explain the inherent deviations of the measured values, calculated values ​​and / or the values ​​provided that will be recognized by those of ordinary skill in the art.

[0022] During the research on the treatment of oily sludge and Fenton iron sludge, the inventors found that if the two types of sludge are mixed, treated with the addition of specific surfactants, and further treated with specific microbial active composite bacterial agents, the treatment effect of oily sludge and Fenton iron sludge can be significantly improved, the sludge treatment cost can be reduced, and it has great commercial value.

[0023] The inventor further studied and believed that this was due to the use of specific surfactants and microbial active composite bacterial agents to treat mixed sludge containing oily sludge and Fenton iron mud, which produced a good synergistic treatment effect. Specific surfactants can effectively reduce the oil-water interfacial tension in oily sludge and promote the dispersion and release of oils and fats, while the acidithiobacillus ferrooxidans in the microbial active composite bacterial agent produces sulfuric acid by oxidizing ferrous iron and creates a strong oxidizing environment, producing a "co-metabolism" effect in the process of metabolizing iron mud, further enhancing the dissolution and degradation of oil pollutants in mixed sludge. Using this method not only improves the treatment efficiency of mixed sludge, but also helps to reduce the difficulty of mixed sludge treatment and promote the feasibility of sludge resource utilization. The present invention was completed accordingly. It should be noted that in the present invention, the mixed sludge of oily sludge and Fenton iron mud is also referred to as "oil sludge".

[0024] Specifically, first, the present invention provides a novel composite surfactant for oil sludge treatment that can effectively treat mixed sludge containing oily sludge and Fenton iron sludge. The composite surfactant for oil sludge treatment of the present invention includes a biological surfactant, a chemical surfactant and an adjuvant. Among them, a mixture of rhamnolipid and sophorolipid is selected as a biological surfactant, sodium dodecylbenzene sulfonate (hereinafter also referred to as SDBS) is selected as a chemical surfactant, and sodium silicate is selected as an adjuvant. The composite surfactant prepared in this way can greatly improve the oil removal effect of mixed sludge.

[0025] In addition, in the composite surfactant of the present invention, the mass ratio of rhamnolipid, sophorolipid, sodium silicate and sodium dodecylbenzene sulfonate is preferably 3:3:30:1 to 4:4:40:1. Furthermore, when the mass of rhamnolipid and sophorolipid is equal, the effect of the composite surfactant is better. In addition, the mass ratio of the biological surfactant to the chemical surfactant is preferably 6:1, that is, the mass ratio of the total mass of rhamnolipid and sophorolipid to sodium dodecylbenzene sulfonate is preferably 6:1. Furthermore, the mass ratio of rhamnolipid, sophorolipid, sodium silicate and sodium dodecylbenzene sulfonate is optimally 3:3:30:1. The inventors believe that this is because rhamnolipid, sophorolipid and sodium dodecylbenzene sulfonate affect each other in the solution.

[0026] In addition, the present invention also provides a cleaning liquid, which is prepared by dissolving the composite surfactant in water. Preferably, the mass concentration of the composite surfactant in the cleaning liquid is 0.4% to 0.8%, and more preferably 0.6%. The oil content of the mixed sludge can be greatly reduced by hot washing the mixed sludge with the cleaning liquid.

[0027] In addition, the present invention also provides a method for treating oily sludge. Specifically, the mixed sludge is cleaned with the cleaning liquid of the present invention for 2 to 4 hours under heating conditions (preferably at a temperature of 40°C to 60°C). The mass ratio of the cleaning liquid to the mixed sludge (also referred to as the liquid-to-solid ratio) is preferably 2:1 to 4:1. It is further preferred that the cleaning liquid and the mixed sludge are mixed at a mass ratio of 3:1 at a temperature of 50°C, and the mixed sludge is cleaned with the cleaning liquid for 3 hours.

[0028] In addition, due to the complexity of the components in the mixed sludge, even if the components are the same, the content of each component in different sludges varies greatly. Therefore, the existing surfactants will have a poor treatment effect on certain specific sludges. In this regard, the cleaning liquid prepared by the composite surfactant of the present invention has an excellent effect on the mixed sludge composed of oily sludge and Fenton iron sludge.

[0029] Among them, in the mixed sludge of the present invention, the oily sludge and the Fenton iron sludge are preferably mixed in a mass ratio of 5:1 to 1:1. In addition, the oil content of the oily sludge can be 30% to 70%, and the iron content of the Fenton sludge can be 20% to 30%. The iron content of the mixed sludge obtained in this way can be 4% to 6%, and the oil content can be 24% to 56%.

[0030] In addition, after the mixed sludge is washed with the washing liquid, the washed mixed sludge can be cooled to room temperature (15°C to 30°C), and then the microbial active composite bacterial agent of the present invention is added and stirred for 2 to 3 hours for treatment.

[0031] The microbial active composite bacterial agent contains acidithiobacillus ferrooxidans. The concentration of acidithiobacillus ferrooxidans in the microbial active composite bacterial agent is preferably 6.8×10 8 –8.2×10 10 The OD600 of the microorganisms in the microbial active composite bacterial agent is preferably 0.6 to 1.5.

[0032] The inventors believe that in the microbial active composite agent of the present invention, Acidithiobacillus ferrooxidans, as one of the main functional bacteria, can oxidize ferrous ions (Fe 2+ ), generating trivalent iron ions (Fe 3+ ). Trivalent iron has strong oxidizing properties, which can help degrade organic matter in oily sludge and promote further reaction of iron compounds in Fenton iron mud. In addition, the bacteria can also oxidize sulfides to produce sulfuric acid, further reducing the pH value of sludge and creating a suitable acidic environment.

[0033] This treatment process combining the composite surfactant of the present invention with a mixed bacterial agent of microorganisms such as acidophilic ferrooxidans can efficiently treat mixed sludge of oily sludge and Fenton iron sludge through the dual effects of chemistry and biology, and has significant degradation efficiency and environmental benefits.

[0034] In addition to Acidithiobacillus ferrooxidans, the microbial active composite bacterial agent preferably also contains other microorganisms capable of decomposing oils and fats, such as oil-degrading bacteria. These bacterial communities can accelerate the decomposition of complex organic matter in oil sludge, especially long-chain hydrocarbons, by secreting lipase, hydrocarbon-degrading enzymes, etc., and convert them into small molecules that are more easily biodegradable. The oil-degrading bacteria can be any one or a combination of Pseudomonas aeruginosa, Bacillus subtilis, and Nocardia asteroides. Among them, it is preferred that the microbial active composite bacterial agent contains 6.8×10 8 –8.2×10 10 CFU / mL of Pseudomonas aeruginosa, 6.8×10 8 –8.2×10 10 CFU / mL of Bacillus subtilis and 6.8×10 8 –8.2×10 10 CFU / mL of Nocardia asteroides.

[0035] According to an embodiment of the present invention, the mass ratio of the microbial active composite bacterial agent to the mixed sludge is preferably 1:50 to 1:150.

[0036] The technical solution of the present invention is described in more detail below through embodiments and comparative examples.

[0037] 1. Preparation of Composite Surfactants of Examples 1 to 5 and Surfactants of Comparative Examples 1 to 3

[0038] According to the description in Table 1, the composite surfactants of Examples 1 to 5 and the surfactants of Comparative Examples 1 to 3 were prepared.

[0039] Table 1 Components of Examples 1 to 5 and Comparative Examples 1 to 3

[0040]

[0041] As can be seen from Table 1, the difference between the composite surfactants of Examples 1 to 5 is that the ratios of rhamnolipid, sophorolipid, sodium silicate and SDBS are different; the difference between Comparative Example 1 and Example 1 is that the sophorolipid in Example 1 is replaced by an equal amount of trehalolipid; the difference between Comparative Example 2 and Example 1 is that the sodium silicate in Example 1 is replaced by an equal amount of sodium carbonate; the difference between Comparative Example 3 and Example 1 is that the SDBS in Example 1 is replaced by an equal amount of sodium alkylbenzene sulfate.

[0042] 2. Preparation of the Microbial Active Composite Agent of the Present Invention

[0043] 1. Slant culture:

[0044] Acidithiobacillus ferrooxidans was dipped with an inoculation loop at 25°C to 30°C, and streaked on a 9k solid medium (28°C to 30°C) for 2 to 3 days. Pseudomonas aeruginosa, Bacillus subtilis, and Nocardia asteroides were dipped with an inoculation loop at 25°C to 30°C, and streaked on LB solid medium (35°C to 37°C) for 2 to 3 days, respectively, to obtain four activated strains.

[0045] Among them, 9k solid culture medium is A liquid: add 3.0g ammonium sulfate, 0.1g potassium chloride, 0.01g calcium nitrate, 0.5g magnesium sulfate, 0.5g potassium dihydrogen phosphate to 600mL of distilled water; B liquid: add 44.2g ferrous sulfate to 300mL of distilled water; C liquid: add 20g agar to 100mL of distilled water. Adjust the pH of A liquid to 6.0-6.2, and sterilize it at 121℃ for 20min together with C liquid; adjust the pH of B liquid to 6.0-6.2 and filter it through a 0.22μm filter membrane for sterilization. Mix the cooled A liquid with B liquid and C liquid evenly, and then cool and solidify. LB solid culture medium refers to adding 10g tryptone, 5g yeast extract, 10g sodium chloride, and 15g agar to 1000mL of water, mixing evenly, and sterilizing it at 121℃ for 20min.

[0046] 2. Primary seed cultivation:

[0047] The four activated strains were inoculated into 9k liquid culture medium and LB liquid culture medium at a 1% inoculation rate under sterile conditions. The 9k liquid culture medium was cultured in a shaking incubator at 28°C-30°C and 130-160rpm for 3-5 days, and the LB liquid culture medium was cultured in a shaking incubator at 35°C-37°C and 130-160rpm for 3-5 days to obtain four primary seeds.

[0048] Among them: 9k liquid culture medium is A liquid: add 3.0g ammonium sulfate, 0.1g potassium chloride, 0.01g calcium nitrate, 0.5g magnesium sulfate, 0.5g potassium dihydrogen phosphate to 700mL of distilled water; B liquid: add 44.2g ferrous sulfate to 300mL of distilled water. Adjust the pH of A liquid to 6.0-6.2 and sterilize at 121℃ for 20min; adjust the pH of B liquid to 6.0-6.2 and filter and sterilize with a 0.22μm filter membrane. Mix the cooled A liquid and B liquid evenly. LB liquid culture medium refers to adding 10g tryptone, 5g yeast extract, and 10g sodium chloride to 1000mL of water, mixing evenly and sterilizing at 121℃ for 20min.

[0049] 3. Fermentation culture:

[0050] The four primary seeds are inoculated in 9k liquid culture medium and LB liquid culture medium at an inoculation rate of 0.5-2%, preferably 1.5%, respectively, and cultured in a shaker. The fermentation culture conditions are as follows: the temperature is 28℃-30℃ and 35℃-37℃ respectively; the rotation speed is 130-160rpm, preferably 150rpm; the culture time is 3-5 days, and the active bacterial liquid of the four strains is obtained.

[0051] 4. Synthetic composite bacterial agent:

[0052] The cultured active bacterial liquids are mixed in a mass ratio of 1:1 to obtain the microbial active composite bacterial agent of the present invention.

[0053] The composition of the composite microbial agent finally prepared is:

[0054]

[0055] 3. Prepare mixed sludge samples for treatment

[0056] 1. Collect three batches of oily sludge from a refinery in Shouguang, Shandong Province for use.

[0057] 2. Collect Fenton iron sludge from a sewage treatment plant in Weifang, Shandong for future use.

[0058] 3. The three batches of oily sludge were mixed with the Fenton iron sludge in a mass ratio of 4:1 to obtain mixed sludge (represented by sludge samples A1, A2 and A3 in the following table).

[0059] 4. Take another batch of oily sludge from a refinery in Shouguang, Shandong Province (represented by sludge sample B in the table below, i.e. the oily sludge in sample A1).

[0060] 3. Sludge oil removal rate detection

[0061] The composite surfactants of Examples 1 to 5, the surfactants of Comparative Examples 1 to 3, and the microbial active composite bacterial agent of the present invention were used to treat the sludge samples according to the following steps, and the treatment effect was evaluated by the oil removal rate.

[0062] Step (i): dissolving the composite surfactants of Examples 1 to 5 and the surfactants of Comparative Examples 1 to 3 in water at a concentration of 0.6% by mass to prepare a cleaning solution (i.e., 6 g of the composite surfactant or surfactant is contained in every 1000 g of the solution);

[0063] Step (ii): the cleaning agent and each sludge sample were mixed in a mass ratio of 3:1 and then mixed and stirred in a constant temperature water bath at 50°C for 3 hours;

[0064] Step (iii): After the cleaning agent and sludge sample system is cooled to 20° C., the microbial active composite bacterial agent is added at a mass ratio of 1:100 of the microbial active composite bacterial agent to the mixed sludge, and stirring is continued for 2.5 hours;

[0065] Step (iv): Allow the reaction system to stand until the solid phase in the reaction system is completely precipitated naturally, pour out the supernatant, and place the remaining solid phase in an oven at 65°C to dry to constant weight. Calculate the oil content and oil removal rate of each sludge sample according to the following method, and record the results in Table 2.

[0066] Determination method of oil content and oil removal rate of sludge samples

[0067] The oil content (TEO) in the sludge was determined by Soxhlet extraction, with petroleum ether solvent selected as the extractant. The determination steps are as follows:

[0068] (1) Take a certain amount of sludge sample (m 1 ), after drying to constant weight, wrap it tightly with a quantitative filter paper of mass a and weigh its mass as b. The mass of the sludge sample dried to constant weight is calculated as m 2 (m 2 =ba);

[0069] (2) Place the filter paper package in the siphon of the installed Soxhlet extraction apparatus, open the condensate, add the extractant to the bottom flask, and start heating;

[0070] (3) heating the solvent until it boils, and repeatedly extracting until the solvent in the siphon tube turns colorless and transparent;

[0071] (4) Take out the filter paper package and put it in a 105℃ oven to dry until constant weight. Take out the filter paper package, weigh it and record the mass as c. The mass of the sample after extraction is m. 3 (m 3 =ca);

[0072] (5) The oil content TEO of oily sludge is calculated according to the following formula:

[0073] TEO=(m 2 -m 3 ) / m 1 ×100%

[0074] (6) The oil removal rate C after surfactant treatment is calculated according to the following formula:

[0075] C=[m 4 (1-W)-m 5 ] / (m 4 ×TEO)×100%

[0076] Among them, m 4 is the mass of each untreated sludge sample in the above step (ii); W is the water content of the sludge sample measured in advance; m 5 is the mass of the sludge sample dried to a constant weight after deoiling in the above step (ii); TEO is the oil content of the sludge sample determined in advance.

[0077] Table 2 Treatment results of various sludge samples (oil sludge removal rate %)

[0078]

[0079] From the test results in Table 2, it can be seen that the oil removal effects of Examples 1 to 5 of the present invention are significantly better than those of Comparative Examples 1 to 3, especially for the mixed sludge samples A1, A2, and A3 mixed with oily sludge and Fenton iron mud, the synergistic effect of the cleaning agent made of the composite surfactant of the present invention and the microbial active composite bacterial agent is more obvious. This shows that the composite surfactant of the present invention has obvious specificity and has a particularly excellent oil removal effect for removing oily sludge in a system mixed with Fenton iron mud.

[0080] To be more specific, by comparing Examples 1 to 5, it can be seen that the oil removal rates of Examples 3 to 5 are significantly lower than those of Examples 1 and 2, indicating that the relative content of each component of the composite surfactant has a greater influence on the oil removal effect of the composite surfactant. After repeated tests, in the composite surfactant of the present invention, the mass ratio of rhamnolipid, sophorolipid, sodium silicate, and sodium dodecylbenzene sulfonate is preferably 3:3:30:1 to 4:4:40:1. The best ratio is: the mass ratio of rhamnolipid, sophorolipid, sodium silicate and sodium dodecylbenzene sulfonate is 3:3:30:1.

[0081] In addition, it can be seen from Comparative Examples 1 to 3 that even if different types of surfactants are compounded, the effects are obviously inferior to the composite surfactant of the present invention, especially the degreasing effect on mixed sludge.

[0082] 4. Sludge dewatering performance test

[0083] 1. Take the first batch of oily sludge from a refinery in Shouguang, Shandong Province and mix it with the Fenton iron mud in a mass ratio of 4:1 to obtain mixed sludge (untreated) as C1 for standby use.

[0084] 2. Take the oily sludge from the same batch as in Example 1 above, mix it with the Fenton iron sludge in a mass ratio of 4:1 to obtain a mixed sludge treated in steps (i) to (iii) of Example 1 above, and use it as C2 for standby.

[0085] 3. Take 100 mL of C1 and C2 respectively, weigh them and pour them into a funnel lined with filter paper, and filter them by gravity for 1 minute; then filter them step by step through a vacuum filter, and the sludge gradually forms a filter cake on the filter paper, and a pressure difference is formed on both sides of the filter cake, and the water in the sludge is filtered out into the beaker; filter them under the condition of constant vacuum until the mud cake breaks and the filtrate remains basically unchanged. Record the time of filtration, the amount of filtrate at the corresponding time, and the total volume of filtrate, then dry and weigh the filter cake at 105°C, calculate the water content of the sludge and the specific resistance of the sludge and record them in Table 3.

[0086] Table 3 Dewatering performance of sludge samples before and after treatment

[0087] serial number Moisture content Specific resistance C1 50.65％ <![CDATA[8.2×10 11 m / g]]> C2 32.14％ <![CDATA[12.0×10 9 m / g]]>

[0088] It can be seen that after the combined treatment of the composite surfactant and the microbial active composite bacterial agent of the present invention, the specific resistance of the mixed sludge is greatly reduced and the dehydration performance is enhanced. It can be seen that the use of the present invention greatly improves the dehydration performance of the mixed sludge formed by mixing oily sludge and Fenton sludge, which is convenient for the subsequent disposal and resource utilization of the mixed sludge.

[0089] 5. Process conditions for using composite surfactants

[0090] In order to determine the best de-oiling effect, the inventors further investigated the effects of cleaning agent concentration, liquid-to-solid ratio, cleaning temperature and cleaning time, and the liquid-to-solid ratio of the microbial active composite bacterial agent on the elution effect. Through orthogonal experiments, it was finally determined that the mass concentration of the composite surfactant in the cleaning solution is preferably 0.4% to 0.8%, the cleaning temperature is preferably 40°C to 60°C, and the cleaning time is preferably 2 to 4 hours. Among them, the mass ratio of the cleaning solution to the mixed sludge (liquid-to-solid ratio) is 2:1 to 4:1, and the mass ratio of the microbial active composite bacterial agent to the mixed sludge (liquid-to-solid ratio) is 1:50 to 1:150; the microbial active composite bacterial agent contains 6.8×10 8 –8.2×10 10 CFU / mL of Acidithiobacillus ferrooxidans, 6.8×10 8 –8.2×1010 CFU / mL of Pseudomonas aeruginosa, 6.8×10 8 –8.2×10 10 CFU / mL of Bacillus subtilis and 6.8×10 8 –8.2×10 10 CFU / mL of Nocardia asteroides. Furthermore, the optimal process conditions are: the mass concentration of the composite surfactant in the cleaning solution is 0.6%, the cleaning temperature is 50°C, the cleaning time is 3 hours, wherein the mass ratio of the cleaning solution to the oily sludge (liquid-solid ratio) is 3:1, and the mass ratio of the microbial active composite bacterial agent to the mixed sludge (liquid-solid ratio) is 1:100.

[0091] The specific implementation methods described above further illustrate the purpose, technical solutions and beneficial effects of the present application in detail. It should be understood that the above description is only the specific implementation method of the present application and is not intended to limit the scope of protection of the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A composite surfactant for sludge treatment, characterized in that: The composite surfactant comprises a biological surfactant, a chemical surfactant and an adjuvant, wherein the biological surfactant is rhamnolipid and sophorolipid, the chemical surfactant is sodium dodecylbenzene sulfonate, and the adjuvant is sodium silicate.

2. The composite surfactant for sludge treatment according to claim 1, characterized in that: The mass ratio of the rhamnolipid, the sophorolipid, the sodium silicate and the sodium dodecylbenzenesulfonate is 3:3:30:1 to 4:4:40:

1.

3. The composite surfactant for oil sludge treatment according to claim 2, characterized in that: The mass ratio of the biological surfactant to the chemical surfactant is 6:1, and the mass ratio of the rhamnolipid to the sophorolipid is 1:

1.

4. The composite surfactant for sludge treatment according to claim 3, characterized in that: The mass ratio of the rhamnolipid, the sophorolipid, the sodium silicate and the sodium dodecylbenzene sulfonate is 3:3:30:

1.

5. A method for treating oil sludge, characterized in that: The oil sludge treatment method comprises the following steps: Step (i): dissolving the composite surfactant according to any one of claims 1 to 4 in water to prepare a cleaning solution; and Step (ii): washing the mixed sludge with the washing liquid under heating conditions, wherein the mixed sludge comprises oily sludge and Fenton iron sludge.

6. The oil sludge treatment method according to claim 5, characterized in that: The mass ratio of the oily sludge to the Fenton iron sludge is 5:1 to 1:

1.

7. The oil sludge treatment method according to claim 5 or 6, characterized in that: In the step (i), the mass concentration of the composite surfactant in the cleaning solution is 0.4% to 0.8%, In the step (ii), the sludge is washed with the washing liquid at a temperature of 40° C. to 60° C. for 2 to 4 hours, wherein the mass ratio of the washing liquid to the mixed sludge is 2:1 to 4:

1.

8. The oil sludge treatment method according to claim 7, characterized in that: After step (ii), the method further comprises: Step (iii): cooling the washed mixed sludge to 15° C. to 30° C., adding a microbial active composite bacterial agent, and stirring for 2 to 3 hours, wherein the microbial active composite bacterial agent contains acidithiobacillus ferrooxidans and petroleum degrading bacteria.

9. The oil sludge treatment method according to claim 8, characterized in that: The concentration of the acidithiobacillus ferrooxidans in the microbial active composite bacterial agent is 6.8×10 8 –8.2×10 10 CFU / mL, the petroleum degrading bacteria is any one or a combination of Pseudomonas aeruginosa, Bacillus subtilis, and Nocardia asteroides.

10. The oil sludge treatment method according to claim 9, characterized in that: The mass ratio of the microbial active composite bacterial agent to the mixed sludge is 1:50 to 1:150.

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