Method for treating high-salt and high-concentration landfill leachate by using microbial agent

Abstract

The invention discloses a method for treating high-salt and high-concentration landfill leachate by using a microbial agent, and the process flow for treating the high-salt and high-concentration landfill leachate comprises pretreatment, MBR (Membrane Bioreactor), UF (Ultra Frequency) and RO (Reverse Osmosis), the microbial agent is a mixed microbial agent which is obtained by mixing rhodococcus corynebacteria with the preservation number of CGMCC (China General Microbiological Culture Collection Center) No.8172 and rhodococcus ruber with the preservation number of CGMCC No.8173 according to the volume ratio of (0.5 to 3): 1. The microbial agent is a mixed microbial agent which is obtained by mixing the rhodococcus corynebacteria with the preservation number of CGMCC No.8172 and the rhodococcus ruber with the preservation number of CGMCC No.8173. When the microbial agent is added into an MBR (Membrane Bioreactor) tank in a landfill leachate treatment process, the removal rate of refractory organic matters and ammonia nitrogen can be increased under the condition that the salinity is 1.0-5% and the CODcr and ammonia nitrogen concentration are relatively high. The treatment efficiency of the high-salt and high-concentration landfill leachate is improved, and the treatment and maintenance cost of the landfill leachate is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of landfill leachate treatment, and in particular relates to a method for treating high-salt and high-concentration landfill leachate by utilizing a microbial agent. Background Art

[0002] With the development of economy and the improvement of living standards, the increase in the amount of garbage has led to an increasing output of landfill leachate. Landfill leachate is a high-concentration organic wastewater with the characteristics of high COD concentration, complex composition, many types of toxic and harmful pollutants, high salinity, and high ammonia nitrogen concentration. As the landfill time increases, the biodegradability decreases, and it is difficult to meet the emission standards using a single treatment method. At present, most of the processes using a combination of physical and chemical + biochemical + membrane deep treatment are used. The commonly used deep treatment technologies are mainly ultrafiltration, nanofiltration, and reverse osmosis membrane treatment technology. However, the membrane treatment equipment has a short service life and high maintenance costs; the high salt content of landfill leachate leads to excessive membrane osmotic pressure and low water production rate. In order to improve the efficiency of membrane treatment and reduce costs, biochemical treatment is often used before membrane treatment. Due to the high salt content, high concentration of organic matter and ammonia nitrogen, high toxicity, and great impact on microorganisms, the use of traditional biochemical treatment is difficult to start, low load, unstable operation, or even non-operation. Therefore, the development of low-cost landfill leachate deep treatment technology and high-efficiency bio-enhanced treatment technology is an important research direction for landfill leachate treatment.

[0003] Microbial agents are widely present in nature and have the characteristics of low cost and no secondary pollution in the degradation of organic pollutants. Since the original solution of landfill leachate contains a variety of salt ions such as chloride ions, sodium ions, sulfate ions, etc., the salt content is usually above 10,000 mg / L, and the conductivity is generally between 10,000 and 45,000 μs / cm. As many as 99 kinds of organic pollutants have been measured, including chlorinated aromatic compounds, non-chlorinated aromatic compounds such as naphthalene and phenanthrene, and substances that are difficult to biodegrade such as aniline compounds and phenolic compounds. The COD concentration of the original solution is as high as 60,000 mg / L or more. Conventional microbial agents are greatly affected by the inhibition and toxicity of high-salt and high-concentration organic wastewater, and the removal performance of high-concentration organic matter and ammonia nitrogen is greatly reduced. The discovery of salt-tolerant microbial flora will improve the effect of bio-enhanced treatment of landfill leachate containing high-salt and high-concentration organic pollutants. Summary of the invention

[0004] In order to solve at least one of the above problems, the present invention provides a method for treating high-salt and high-concentration landfill leachate using a microbial agent. The bio-augmentation treatment of the landfill leachate is performed by using a microbial agent to improve the treatment efficiency of the landfill leachate and reduce the cost of landfill leachate treatment.

[0005] In order to achieve the above object, the present invention adopts the following technical means: The present invention provides a method for treating high-salt and high-concentration landfill leachate by using a microbial agent. The process flow for treating the high-salt and high-concentration landfill leachate is pretreatment+MBR+UF+RO. The microbial agent is added into the MBR reaction tank. The microbial agent is a red coccus (CGMCC No. 8172) preserved in the General Microbiological Center of the Chinese Academy of Sciences, Institute of Microbiology, No. 3, Beichen West Road, Chaoyang District, Beijing, with a preservation date of September 11, 2013. Rhodococcus corynebacterioides ), Rhodococcus erythrocytes with the deposit number of CGMCC No. 8173 ( Rhodococcus ruber ) is mixed according to the volume ratio of (0.5-3):1 to obtain the mixed bacterial agent.

[0006] In some preferred embodiments of the present invention, the microbial agent is Rhodococcus with a preservation number of CGMCC No. 8172 ( Rhodococcus corynebacterioides ), Rhodococcus erythrocytes with the deposit number of CGMCC No. 8173 ( Rhodococcus ruber ) are mixed in a volume ratio of 3:1 to obtain the mixed bacterial agent.

[0007] In some embodiments of the present invention, before the microbial inoculants are mixed, the Rhodococcus and the Red Coccus are cultured separately in an environment containing 1% to 5% salt by mass.

[0008] In some embodiments of the present invention, the first stage of the training culture is: take Rhodococcus and Red Coxsackie respectively and inoculate them in 5% NaCl, CODcr 4000~5000 mg / L high-salt and high-concentration landfill leachate for 4~5 days, then take 10% of the landfill leachate and inoculate it in the same landfill leachate, and repeat the training 3~4 times.

[0009] In some embodiments of the present invention, the second stage of training culture is: taking single bacterial colonies of Rhodococcus and Red Coxsaccharomyces respectively and inoculating them into LB liquid culture medium for culture, the pH of the LB liquid culture medium is 6.5~7.5, the NaCl concentration is 1%~5.0%, the culture temperature is 25~35°C, 120~160rpm, and the shaking culture is 2~4 days.

[0010] In some preferred embodiments of the present invention, the pH of the LB liquid culture medium is 7.0, NaCl is 2.0-2.5%, the culture temperature is 32° C., and the shaking culture is performed at 140 rpm for 3 days.

[0011] In some embodiments of the present invention, the mass fraction of salt in the high-salt landfill leachate is 1-5%.

[0012] In some embodiments of the present invention, the daily dosage of the microbial agent is 1 / 10,000 to 5 / 10,000 by volume. In some preferred embodiments of the present invention, the daily dosage of the microbial agent is 2 / 10,000 by volume.

[0013] In some embodiments of the present invention, the dissolved oxygen in the MBR reaction tank is 2-4 mg / L.

[0014] In some embodiments of the present invention, the hydraulic retention time in the MBR reaction tank is 8 to 12 hours.

[0015] Beneficial effects of the present invention Compared with the prior art, the present invention has the following beneficial effects: (1) The microbial agent provided by the present invention is resistant to salt and organic pollutants; the two strains of microorganisms provided in this application are isolated from oil sludge in oil fields. The oil sludge not only has a high salt content, but also has complex components, including alkanes, cycloalkanes, aromatic hydrocarbons, sulfur compounds, nitrogen compounds, oxygen compounds and other difficult-to-degrade compounds, and is obtained by long-term domestication in such an environment. Among all salt ions, chloride ions are the most toxic to microorganisms. The microbial agent provided by this application can not only tolerate a NaCl concentration of 5%, but also degrade difficult-to-degrade organic matter in high-concentration landfill leachate.

[0016] (2) Improve treatment efficiency. In this treatment process, microbial agents that are salt-tolerant and can degrade organic matter are added to the MBR reaction tank. The outer layer of the MBR membrane is an aerobic reaction that degrades organic matter into small molecules and oxidizes ammonia nitrogen into nitrite nitrogen. The inner layer of the MBR membrane is an anaerobic reaction that uses the small molecular organic matter produced by aerobic degradation as a carbon source and the nitrite produced by nitrification as a nitrogen source. Anaerobic denitrification is performed to convert ammonia nitrogen into nitrogen gas. In the same reactor, carbon removal and denitrification are completed simultaneously, which improves the treatment efficiency compared with conventional microbial agents.

[0017] (3) Reduce treatment costs. The current conventional treatment process for landfill leachate is physicochemical + biochemical + membrane deep treatment. Due to the low efficiency of physicochemical + biochemical treatment, the effluent water quality is relatively poor, and the power consumption and replacement frequency of membrane treatment increase, which leads to increased operation and maintenance costs. In addition, in order to improve the influent water quality of membrane deep treatment and reduce the salt content, the high-concentration organic landfill leachate is diluted in the early stage, thereby increasing the treatment cost. The salt-tolerant microbial agent enhanced treatment process provided by the present invention improves the biochemical treatment efficiency, greatly improves the water quality of the influent water of membrane deep treatment, and increases the service life of the membrane equipment. Reduce maintenance and treatment costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The effluent CODcr changes of landfill leachate before and after adding microbial agents in Example 8 of the present invention are shown; Figure 2 The figure shows the change of NH3-N effluent from landfill leachate before and after adding microbial agent in Example 8 of the present invention. DETAILED DESCRIPTION

[0019] The following examples are used to demonstrate preferred embodiments of the present invention. It will be appreciated by those skilled in the art that the techniques disclosed in the following examples represent techniques discovered by the inventors that can be used to implement the present invention and therefore can be considered as preferred embodiments of the present invention. However, it will be appreciated by those skilled in the art based on this specification that many modifications may be made to the specific embodiments disclosed herein and still achieve the same or similar results without departing from the spirit or scope of the present invention.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs, and the materials cited herein and those cited by them are incorporated by reference. Those skilled in the art will recognize or will learn through routine experimentation that there are many equivalents to the specific embodiments of the invention described herein. Such equivalents are intended to be encompassed by the claims.

[0021] The technical solution of the present application is further described in detail below in conjunction with specific implementation methods.

[0022] Example 1 The leachate used for screening bacterial agents is old leachate from a landfill, with a salt content of 2.2%, CODcr of 2870 mg / L, ammonia nitrogen of 134 mg / L, and a pH of 7.2.

[0023] The screening method of the microbial agent is as follows: 300 ml of landfill leachate is taken and placed in a 500 ml triangular flask, and 6 strains of bacteria that have a degradation effect on difficult-to-degrade organic matter are selected from the strain library of the unit, namely, strain 1: Bacillus subtilis ( Bacillus subtilis ); strain 2: Rhodococcus ( Rhodococcus corynebacterioides ); strain 3: Halomonas ( Halomonas sp ); strain 4: Rhodococcus ( Rhodococcus sp . LV4); strain 5: Rhodococcus erythrocytes ( Rhodococcus ruber ); strain 6: Rhodobacterium sphaeroides ( Rhodobacter sphaeorides ).

[0024] The 6 strains were cultured in LB medium and then washed three times with sterile water. One strain was inoculated into one bottle. The inoculation volume was: OD 600The culture medium was 10 ml of bacterial solution with a concentration of 1.0. The landfill leachate without bacterial solution was used as a control. It was inoculated in 4% NaCl, CODcr 4000-5000 mg / L high-salt and high-concentration landfill leachate and cultivated for 5 days. Then 10% of the landfill leachate was inoculated in the same landfill leachate. After repeating the cultivation for 4 times, the culture was carried out in a shaker at 30°C and 130 rpm. CODcr was sampled and tested every day. The removal rates of the six strains for landfill leachate are shown in Table 1.

[0025] Table 1 Screening results of strains from old landfill leachate

[0026] The above results show that strains 2 and 5 are the best strains for treating old landfill leachate with a salinity of 2.2%, followed by strain 1.

[0027] Among them, strain 1: Bacillus subtilis ( Bacillus subtilis ) was deposited at the General Microbiology Center of China Microbiological Culture Collection Committee, Institute of Microbiology, Chinese Academy of Sciences, No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, on April 20, 2017, with the deposit number CGMCC No. 14052. Strain 2 Rhodococcus ( Rhodococcus corynebacterioides ), strain 5 Rhodococcus erythrocytes ( Rhodococcus ruber ) are deposited in the General Microbiology Center of China Culture Collection Committee of Microorganisms, Institute of Microbiology, Chinese Academy of Sciences, No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, on September 11, 2013. The deposit number of Rhodococcus is CGMCC No. 8172, and the deposit number of Rhodococcus erythrocytes is CGMCC No. 8173.

[0028] Example 2 The leachate used for screening the bacterial agent was fresh leachate from a landfill, with a salt content of 2.2%, CODcr of 3847 mg / L, ammonia nitrogen of 68 mg / L, and a pH of 7.2.

[0029] The screening method of the bacterial agent is the same as that in Example 1. The removal rates of the six strains on fresh landfill leachate are shown in Table 2.

[0030] Table 2 Results of strain screening of fresh landfill leachate

[0031] The above results show that strains 2 and 5 are strains with better effects in treating fresh landfill leachate with a salinity of 2.2%, followed by strain 1. The results are basically consistent with those obtained in Example 1.

[0032] Among them, strain 2 Rhodococcus ( Rhodococcus corynebacterioides ), strain 5 Rhodococcus erythrocytes (Rhodococcus ruber ), both of which are deposited in the General Microbiology Center of China Culture Collection Committee of Microorganisms, Institute of Microbiology, Chinese Academy of Sciences, No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, on September 11, 2013. The deposit number of Rhodococcus is CGMCC No. 8172, and the deposit number of Rhodococcus erythrocytes is CGMCC No. 8173.

[0033] Example 3 The strain 2 obtained by screening was Rhodococcus ( Rhodococcus corynebacterioides ), strain 5 Rhodococcus erythrocytes ( Rhodococcus ruber ) is an exploration of inoculation scheme for landfill leachate treatment bacterial agents.

[0034] The leachate used in this embodiment is old landfill leachate, with a salt content of 2.2%, a CODcr of 2870 mg / L, an ammonia nitrogen of 134 mg / L, and a pH of 7.2.

[0035] The two strains screened were inoculated with single colonies from the plate into LB liquid culture medium. The culture conditions were pH 6.5-7.5, NaCl 5.0%, culture temperature 25-35°C, 120-160 rpm, and shaking culture for 2-4 days.

[0036] The treatment method is as follows: 300 ml of landfill leachate is taken and placed in a 500 ml conical flask, and strains 2 and 5 selected in Examples 1 and 2 are cultured with an inoculum size of OD 600 1.0 bacterial solution was used and 10 ml was inoculated according to the mixing ratio of strain 2: strain 5 of 1:1, 1:2, 1:3, 1:4, and 1:5. The landfill leachate without bacterial solution was used as a control. The culture was carried out in a shaker at 30°C and 130rpm. Samples were taken every day to test CODcr and NH3-N. The results of the mixed bacterial agent treatment of landfill leachate are shown in Table 3.

[0037] Table 3 Treatment results of landfill leachate with mixed bacterial agents in different proportions

[0038] Example 4 The method and landfill leachate used in this embodiment are the same as those in Example 3. 10 ml was inoculated with strain 2: strain 5 in a mixing ratio of 1:1, 2:1, 3:1, 4:1, and 5:1, respectively, and the landfill leachate without bacterial liquid inoculation was used as a control. The results of landfill leachate treatment with mixed bacterial agents are shown in Table 4.

[0039] Table 4 Treatment results of landfill leachate with mixed bacterial agents in different proportions

[0040] Example 5 The method and landfill leachate used in this embodiment are the same as those in Example 3. 10 ml was inoculated according to the mixed ratio of strain 1: strain 2: strain 5 of 1:3:1, and compared with the mixed ratio of strain 2: strain 5 of 3:1. The results of the mixed bacterial agent treating landfill leachate are shown in Table 5.

[0041] Table 5: Treatment results of landfill leachate with mixed bacterial agents

[0042] Example 6 The method and landfill leachate used in this embodiment are the same as those in Example 3. 10 ml was inoculated according to the mixed ratio of strain 1: strain 2: strain 5 of 1:1:2, and compared with the mixed ratio of strain 2: strain 5 of 1:2. The results of the mixed bacterial agent treating landfill leachate are shown in Table 6.

[0043] Table 6: Treatment results of landfill leachate with mixed bacterial agents

[0044] Example 7 The method and landfill leachate used in this embodiment are the same as those in Example 3. 10 ml of the mixture was inoculated with a ratio of 3:1:1 of Rhodococcus: Rhodococcus: activated sludge, and compared with a ratio of 3:1 of strain 2: strain 5. The results of the mixed bacterial agent treatment of landfill leachate are shown in Table 7.

[0045] Table 7: Treatment results of landfill leachate with mixed bacterial agents

[0046] It can be seen from the results of Examples 1 to 7 that the microbial agents were used in different combinations to treat landfill leachate with a salt content of 2.2%. The volume ratio of Rhodococcus to Red Coccus in the microbial agents was (0.5-3):1, and good removal effects were achieved for both CODcr and NH3-N.

[0047] Example 8 A landfill in Zhejiang Province uses pretreatment + MBR + UF + RO process to treat leachate from aged garbage, with a daily processing capacity of 400t / d. The designed influent salinity is ≤2.5%, CODcr ≤1200mg / L, and NH3-N ≤60mg / L. Currently, the effluent CODcr and NH3-N cannot stably meet the pollutant emission limits specified in the Pollution Control Standards for Municipal Waste Landfills (GB 16889-2008).

[0048] After culturing, Rhodococcus corynebacterioides and Rhodococcus ruber were mixed in a volume ratio of 3:1 to obtain a mixed bacterial solution, which was added to the MBR reaction tank at a daily dosage of 1 / 10,000 of the volume ratio. When the effluent stabilized and met the standards in the later stage, the dosage was changed to 1 / 10,000 of the volume ratio every other day, with a dissolved oxygen of 3.0 mg / L and a hydraulic retention time of 6 hours. The treatment effect is shown in Figure 1 and Figure 2 .

[0049] have Figure 1 and Figure 2 It can be seen that before adding the bacterial agent, the effluent CODcr was 121-132 mg / L, which could not stably meet the standard. After adding the bacterial agent for 20 days, the effluent CODcr could stably reach 50 mg / L, and the removal rate increased from 87-89% before adding the bacterial agent to 96%. Before adding the bacterial agent, the effluent NH3-N was 13-18 mg / L, which could not stably meet the standard. After adding the bacterial agent for 21 days, the effluent NH3-N was below 6.3 mg / L, and the removal rate increased from 71-80% before adding the bacterial agent to 91-93%.

[0050] It can be seen that adding the microbial agent in the present application to the MBR pool in the landfill leachate treatment process can improve the removal rate of difficult-to-degrade organic matter and ammonia nitrogen under the conditions of salt content of 2.0% to 5% and high CODcr and ammonia nitrogen concentrations. At the same time, the microbial agent in the present application can tolerate a salinity of up to 5% and is suitable for the treatment of high-salt and high-concentration landfill leachate.

[0051] All documents mentioned in the present invention are cited as references in this application, just as each document is cited as references separately. In addition, it should be understood that after reading the above teachings of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined in the present application.

Claims

1. A method for treating high-salt and high-concentration landfill leachate using a microbial agent, characterized in that: The process flow for treating high-salt and high-concentration landfill leachate is pretreatment + MBR + UF + RO. Microbial agents are added to the MBR reaction tank. The microbial agents are Rhodococcus (CGMCC No. 8172, which was deposited in the General Microbiological Center of China Microbiological Culture Collection Administration Committee on September 11, 2013. Rhodococcus corynebacterioides ), Rhodococcus erythrocytes with the deposit number of CGMCC No. 8173 ( Rhodococcus ruber ) is a mixed bacterial agent obtained by mixing according to the volume ratio of (0.5~3):

1.

2. The method according to claim 1, characterized in that: Before the microbial inoculants are mixed, the Rhodococcus and the Red Coccus are first cultured in an environment with a salt content of 1% to 5%.

3. The method according to claim 2, characterized in that: The first stage of the training culture is: taking Rhodococcus and Rhodococcus erythrocytes respectively and inoculating them in 5% NaCl, CODcr 4000-5000 mg / L high-salt and high-concentration landfill leachate for 4-5 days.

4. The method according to claim 3, characterized in that: After 4-5 days of training, take 10% of the landfill leachate and inoculate it in the same landfill leachate, and repeat the training 3-4 times.

5. The method according to claim 3, characterized in that: The second stage of the training culture is: taking single bacterial colonies of Rhodococcus and Rhodococcus erythrocytes and inoculating them into LB liquid culture medium for culture, the pH of the LB liquid culture medium is 6.5-7.5, the NaCl concentration is 1%-5.0%, the culture temperature is 25-35°C, 120-160rpm, and the shaking culture is carried out for 2-4 days.

6. The method according to claim 1, characterized in that: The mass fraction of salt in the high-salt landfill leachate is 1-5%.

7. The method according to claim 1, characterized in that: The daily dosage of the microbial agent is 1 / 10,000 to 5 / 10,000 by volume.

8. The method according to claim 7, characterized in that: The microbial agent is added daily until the treated effluent reaches the standard stably, and then the microbial agent is added every other day, with the addition amount being 1 / 10,000 to 5 / 10,000 by volume.

9. The method according to claim 1, characterized in that: In the MBR reaction tank, the dissolved oxygen is 2-4 mg / L.

10. The method according to claim 1, characterized in that: In the MBR reaction tank, the hydraulic retention time is 8 to 12 hours.

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