A composite double carbon source for sulfate-reducing bacteria and a preparation method thereof

Abstract

The application belongs to the technical field of water treatment, and particularly relates to a composite double carbon source for sulfate-reducing bacteria and a preparation method thereof. The application constructs a double carbon source system by using agricultural and forestry waste biochar, reduced iron, fruit peel waste and lactic acid bacteria flora, provides a suitable growth environment and carbon source for sulfate-reducing bacteria, and thus promotes the reduction of sulfate. The application provides the carbon source for an acid mine drainage treatment method, and the carbon source is convenient to obtain, simple to operate, high in treatment capacity and reduction rate, and can be widely applied in actual engineering.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of water treatment, and particularly relates to a composite double carbon source for sulfate-reducing bacteria and a preparation method thereof. BACKGROUND

[0002] The SRB microbial method can remove sulfate in the process of oxidation-reduction reaction, and the produced sulfide can precipitate heavy metals in water bodies and soil, has low cost, no secondary pollution, is safe and stable, and has become a research hotspot in the world and has been widely applied to the research of water body and soil heavy metal remediation technology. However, the growth and oxidation-reduction reaction of SRB are affected by carbon source, pH value, heavy metals and other factors, which seriously affects the actual application effect. In the face of the competition of other anaerobic microorganisms, SRB often cannot obtain sufficient carbon source; H+ and heavy metals in acid mine wastewater have great toxic and inhibitory effects on SRB.

[0003] Patents CN103265142A and CN111362425B both disclose a method of increasing iron-carbon micro-electrolysis reaction to cooperate with sulfate-reducing bacteria to treat acid mine wastewater, but the above patents still have problems of long start-up time and unstable carbon source, which further affect the treatment effect. SUMMARY

[0004] In order to solve the problem that the growth and oxidation-reduction reaction of SRB are affected by carbon source, pH value, heavy metals and other factors, the application provides a composite double carbon source for sulfate-reducing bacteria and a preparation method thereof. The application constructs a double carbon source system by using agricultural and forestry waste biochar, reduced iron, fruit peel waste and lactic acid bacteria flora, and can provide a suitable growth environment and carbon source for sulfate-reducing bacteria, so as to promote the reduction of sulfate. The specific technical scheme is as follows:

[0005] A composite double carbon source for sulfate-reducing bacteria: the composite double carbon source comprises agricultural and forestry waste biochar, reduced iron, fruit peel waste and lactic acid bacteria flora; and is prepared by the following steps:

[0006] (1) The fruit peel waste and the anaerobically cultivated lactic acid bacteria flora are mixed and fermented to produce a mixed fermentation product.

[0007] (2) The agricultural and forestry waste biochar and the reduced iron are added to the mixed fermentation product to obtain a mixed product, which is the composite double carbon source.

[0008] Further, the agroforestry waste biochar is biochar prepared from one or more of corn straw, peanut shell, sugarcane residue and rice straw; the peel waste is one or more of mango peel, banana peel, pear peel, mango peel, apple peel and pineapple peel; the lactic acid bacteria flora is commercially purchased lactic acid bacteria mixed dry powder; and the reduced iron powder is commercially purchased analytical pure iron powder.

[0009] Further, the mixed fermentation conditions in step (1) are as follows: anaerobic conditions, the fermentation temperature is set to 35 degrees, and the pH value is set to 7.0.

[0010] Further, the anaerobic cultivation method of the lactic acid bacteria flora is as follows: the purchased lactic acid bacteria mixed dry powder is added to the MRS culture medium and cultured in an anaerobic, 35 DEG C, 150 r / min constant-temperature shaking incubator, and the constant-temperature shaking culture is repeated for 2-3 times.

[0011] Further, the lactic acid bacteria in the lactic acid bacteria flora are single flora or mixed flora of Lactobacillus, Lactococcus, Pediococcus, Bifidobacterium, Leuconostoc, Streptococcus and Dorea.

[0012] Further, the ratio of the mixed fermentation product to the iron-carbon mixture in step (2) is 8:1, and the ratio of iron to carbon is 4:1; after mixing, the mixture is shaken and then statically placed for 24 hours, and the mixed product after static placement is the composite double carbon source.

[0013] The application also provides application of the composite double carbon source for sulfate-reducing bacteria, i.e., the composite double carbon source is used as a carbon source for treating acid mine wastewater.

[0014] The application has the following beneficial effects:

[0015] The application adopts mixed fermentation of lactic acid bacteria flora and peel waste to produce lactic acid, propionic acid and other different molecules of organic acid, which directly provides a common available carbon source for SRB. The biochar not only provides a long-acting carbon source for SRB, but also the reduced iron can form more iron-carbon microelectrodes in the acid environment (ph 3-5) formed by lactic acid fermentation, the anode releases electrons, the cathode accepts and transfers electrons, and a large number of micro original batteries are formed microscopically. The corrosion process of the zero-valent iron on the surface of the biochar consumes hydrogen ions in the water in the acid and rare earth wastewater, the reduction of hydrogen ions improves the pH of the solution, and the pH in the growth environment of microorganisms is improved, which can create the acid-base conditions required by SRB.

[0016] At the same time, a large amount of active [H] is generated in the microelectrolysis process, which converts the complex organic matter and macromolecular refractory organic acid produced by lactic acid fermentation into small molecular organic acid, and provides more available carbon source for SRB; Fe 0 Electrochemistry / corrosion with oxygen or water to generate Fe 2+and H + is converted into H2, and the generated H2 provides an electron donor for SRB, reducing the concentration of the electron donor required in the sulfate reduction process. The micro-electrolysis process generates Fe 2+ is an activator of the enzyme catalyzing the sulfate reduction reaction, Fe 2+ is an active component of various enzymes in SRB cells, and Fe 2+ can form metal sulfides with soluble sulfides to reduce the inhibition of SRB. By using the micro-electrolysis reaction of iron and carbon, through the synergistic effect of redox reaction, electrochemical enrichment, etc., part of the metal ions can be quickly removed and the pH value of the acid mine wastewater can be increased, effectively solving the problems of low pH and heavy metal inhibition of SRB activity in acid mine wastewater.

[0017] The lactic acid fermentation carbon source is combined with the iron-carbon primary battery, not only forming a double carbon source system, but also adjusting the pH value of the fermentation product through the iron-carbon primary battery, promoting the reproduction of SRB, and further promoting the formation of lactic acid fermentation products into small molecule carbon sources suitable for SRB. The two are mutually synergistic and objectively achieve the effect of 1+1 greater than 2.

[0018] The present application provides a carbon source for acid mine wastewater treatment, which is convenient to obtain, simple to operate, high in treatment capacity and reduction rate, and can be widely applied in practical engineering. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0020] Embodiment 1

[0021] The preparation method of the composite carbon source is as follows:

[0022] (1) The peel waste and the anaerobically cultured lactic acid bacteria flora are mixed and fermented to produce a mixed fermentation product.

[0023] (2) The agricultural and forestry waste biochar and reduced iron are added to the mixed fermentation product to obtain a mixed product.

[0024] Specifically, the purchased lactic acid bacteria mixed powder is added to the MRS culture medium for anaerobic culture, and the constant temperature shaking incubator is used for shaking at 35℃ and 150r / min. The constant temperature shaking culture is carried out for 2-3 days, and the culture is repeated for 2-3 times.

[0025] The broken wall crushed mango peel mixture is added to the lactic acid bacteria mixed culture medium, and the anaerobic fermentation temperature is set to 35 degrees, the ph value is set to 7.0, and the fermentation is 72 hours.

[0026] The mixed fermentation product 1 is added to the straw biochar and reduced iron, and the ratio of the mixed fermentation product to the iron-carbon mixture is 8:1, and the ratio of iron to carbon is 4:1. After mixing, shake evenly and stand for 24 hours.

[0027] The mixed product after standing for 24 hours is used as a carbon source for sulfate-reducing bacteria, and is used in sulfate bacteria-related research to study its effect on removing sulfate radicals.

[0028] In this embodiment, mango peel is used, and the pH of the product at each step is as follows:

[0029] Type of fruit peel Initial pH after anaerobic fermentation pH after 24 h of iron-carbon mixture addition Mango peel 3.09 6.00

[0030] The composition of the water used in the experiment in this embodiment is as follows:

[0031] Table 1 Composition of simulated mine wastewater (pH = 6.5)

[0032] Medicament Mass concentration (g / L) Medicament Mass concentration (g / L) K2HPO4.3H2O 0.5 FeSO4.7H2O 0.5 NH4Cl 1.5 CaCl2·2H2O 0.06 MgSO4.7H2O 1.256 L-cysteine hydrochloride 0.6 Na2SO4 0.5 Pb 2 mg / L

[0033] 300ml of simulated wastewater without sodium lactate (Table 1) was added to each bottle, 40ml of mixed double carbon source was added, the ph value was adjusted to 6.5, 10ml of SRB bacteria liquid was added to each bottle, and nitrogen was filled for 30 seconds. Each treatment has 3 replicates. After preparation, all experimental bottles are placed in a 35-degree constant temperature incubator for incubation. Sampling is taken the next day after the experiment starts, and sampling is taken every 1 day, for a total of 1 week. The change in sulfate content is tested. The sulfate removal rate is 77%, and the sulfate concentration at the end of the experiment is 206mg / L.

[0034] Example 2

[0035] The experimental process and the water used in the experiment are basically the same as in Example 1, except that the pear skin is used instead of the mango peel in Example 1, and the amount of long-acting slow-release carbon source is 30ml.

[0036] Type of fruit peel Initial pH after anaerobic fermentation pH after 24 h of iron-carbon mixture addition Pear peel 2.53 5.71

[0037] The final sulfate removal rate is 50%, and the sulfate concentration at the end of the experiment is 461mg / L.

[0038] The above describes the preferred embodiments of the patent in detail, but the patent is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the spirit of the patent.

Claims

1. A composite dual carbon source for sulfate-reducing bacteria, characterized in that: The composite dual carbon source includes agricultural and forestry waste biochar, reduced iron, fruit peel waste and lactic acid bacteria; it is prepared by the following steps: (1) First, fruit peel waste and anaerobic lactic acid bacteria are mixed and fermented to produce mixed fermentation products; (2) Agricultural and forestry waste biochar and reduced iron are added to the mixed fermentation products to obtain the mixed product, which is the composite dual carbon source.

2. The composite dual carbon source for sulfate-reducing bacteria according to claim 1, characterized in that: The agricultural and forestry waste biochar is prepared from one or more of corn stalks, peanut shells, sugarcane bagasse, and rice straw; the fruit peel waste is one or more of mango peel, banana peel, pear peel, apple peel, and pineapple peel; the lactic acid bacteria are commercially purchased mixed dry powder of lactic acid bacteria; and the reduced iron powder is commercially purchased analytical grade iron powder.

3. The composite dual carbon source for sulfate-reducing bacteria according to claim 1, characterized in that: The mixed fermentation conditions in step (1) are: anaerobic conditions, fermentation temperature set to 35 degrees, and pH value set to 7.

0.

4. The composite dual carbon source for sulfate-reducing bacteria according to claim 2, characterized in that: The anaerobic culture method for lactic acid bacteria is as follows: Add the purchased mixed dry powder of lactic acid bacteria to MRS medium and culture it in an anaerobic, constant temperature shaking incubator at 35℃ and 150r / min for 2-3 days under constant temperature conditions. Repeat the culture 2-3 times.

5. The composite dual carbon source for sulfate-reducing bacteria according to claim 1, characterized in that: The lactic acid bacteria in the lactic acid bacteria flora are single or mixed flora from species and subspecies of Lactobacillus, Lactococcus, Pediococcus, Lactobacillus brevis, Leuconostoc, and Bifidobacterium.

6. The composite dual carbon source for sulfate-reducing bacteria according to claim 1, characterized in that: In step (2), the ratio of the mixed fermentation product to the iron-carbon mixture is 8:1, and the iron-carbon ratio is 4:

1. After mixing, the mixture is shaken and left to stand for 24 hours. The mixed product after standing is the composite dual carbon source.

7. The application of the compound dual carbon source for sulfate-reducing bacteria according to any one of claims 1-6, characterized in that: A composite dual carbon source is used as a carbon source for sulfate-reducing bacteria to treat acidic mine wastewater.