CN101823072B - Method for strengthening methane oxidation of covering layer of landfill site - Google Patents

Abstract

A method for enhancing methane oxidation of landfill overburden, relating to a method capable of enriching methanophilic microorganisms inside mineralized waste. First, weigh the sugar according to the ratio of adding 0.5-3kg of sugar per ton of mineralized waste, then add 1-3 parts of sugar to 100 parts of water and mix well, make a sugar solution, add it to the mineralized waste, and mix well After 7-10 days of acclimatization, it becomes the cover layer material; finally, after the completion of the domestic waste landfill unit operation, the cover layer material is evenly spread on the surface of the domestic waste according to the conventional covering process with a final cover layer thickness of 40-60cm; It was detected that the methane oxidation efficiency increased to 810g/(m ² ·d). The invention treats waste with waste, has low cost, and is 2 to 3 times higher than the methane oxidation efficiency of common landfill covering materials, realizes the reduction of greenhouse gas emissions in landfills, has obvious social and economic benefits, and can be widely used It is especially suitable for strengthening the methane oxidation covering layer of small and medium-sized domestic waste landfills.

Description

A method of enhancing methane oxidation in landfill overburden

technical field

The invention relates to a method for strengthening the methane oxidation capacity of a landfill cover layer, in particular to a method capable of enriching methanophilic microorganisms inside mineralized garbage, and belongs to the technical fields of environmental pollution prevention and control technology and greenhouse gas emission reduction.

Background technique

Methane in the atmosphere is an important greenhouse gas second only to CO ₂ , and its contribution to the greenhouse effect is as high as 26%. The global annual methane emission reaches 5.35×10 ⁸ t, of which the anthropogenic methane emission is 3.75×10 ⁸ t. The organic waste in domestic waste landfill decomposes under anaerobic conditions, which will produce landfill gas. Research in recent years has concluded that domestic waste landfills have become one of the largest anthropogenic sources of methane in the atmosphere.

Methanotrophs can use methane as a carbon source and energy source, use oxygen as an electron acceptor, and catalyze the four-step reaction of methane monooxygenase, methanol dehydrogenase, formaldehyde dehydrogenase and formate dehydrogenase to landfill domestic waste Methane is converted to carbon dioxide and forms the cytoplasm. Carbon dioxide is a metabolite of bacteria, that is, methane is finally oxidized into carbon dioxide. Previous studies have shown that methane oxidation in the functional overlay can effectively promote the terminal conversion of anthropogenic methane. The number of methane-oxidizing bacteria in the 0-30cm soil layer is the largest and the activity is the strongest, and the methane oxidation rate can reach up to 290g/(m ² ·d). The main factors affecting methane oxidation in the functional overlay are soil structure, nutrient status, humidity, temperature, concentration of methane and oxygen, NH ₄ ⁺ and soil pH. Although research on methane-oxidizing microorganisms in functional overlays and factors affecting methane oxidation has been relatively common, the efficiency of methane oxidation through overlays is not very satisfactory. The biggest problem is that the cell growth rate of methanotrophs is slow, Many bottlenecks, such as low density and catalytic reaction affected by reducing coenzymes, limit the application and development of methanotrophs. Because methanotrophs can only use methane or methyl compounds as carbon sources, it is difficult to isolate them by means of agar plates, which makes it difficult to apply methods of bacterial enrichment and expanded culture in engineering. Therefore, in order to ensure the engineering application of overburden methane oxidation, the oxidation rate of unit overburden must be increased.

Contents of the invention

The purpose of the invention is to disclose a method for improving the methane oxidation efficiency of overburden layer with simple process and low cost, which is suitable for small and medium-sized domestic waste landfills.

In order to achieve the above object, the present invention is subject to "many bacteria can utilize multi-carbon compounds and single-carbon compounds rather than exclusively relying on methane or methanol as carbon source and Inspired by "Energy", more attention was paid to the degradation of multi-carbon compounds by methanotrophs, and it was found that the addition of sugar compounds can enhance the methane oxidation capacity of the overburden, which fundamentally solved the bottleneck that is difficult to improve the methane oxidation capacity of the traditional overlay , to avoid the greenhouse effect caused by the release of methane. Furthermore, in the study of mineralized waste, it was found that adding sugar compounds such as sucrose and glucose as carbon source to mineralized waste, after a period of domestication, the methane oxidation effect of mineralized waste was significantly enhanced.

The definition of mineralized garbage referred to in the present invention is: on a dry basis, when the domestic garbage in the landfill has been biodegraded for 8 years or more, the solid product is reduced to an organic matter content of 9 to 15%, and an ion exchange capacity of 120% ~140mmol/100g, the number of bacteria is 1~9× ¹⁰⁶ /g, the pH value is near neutral 7.5, and the saturated hydraulic permeability coefficient K _S is 1~1.3cm/min, it becomes stable mineralized garbage, and its adsorption specific surface area 5-6m ² /g, total nitrogen 0.5%, total phosphorus and total potassium are about 1%. Mineralized waste has undergone methane domestication under long-term landfill conditions and contains a large number of microorganisms that can both oxidize methane and utilize sugar. Therefore, using mineralized waste as a functional covering material, strengthened by sugar, can effectively promote the methane oxidation efficiency of the covering layer.

The specific process is as follows:

First, measure sugar according to the ratio of 0.5-3kg of sugar per ton of mineralized waste, then add 1-3 parts of sugar to 100 parts of water and stir evenly to form a sugar solution; add the sugar solution to the mineralized waste After 7-10 days of acclimation (resting at room temperature) to become the cover layer material; finally, after the domestic waste landfill unit operation is completed, the cover layer material will be covered according to the conventional covering process with a final cover layer thickness of 40-60cm Evenly spread on the surface of domestic garbage; after testing, the methane oxidation efficiency increased to 810g/(m ² ·d).

The mineralized waste is landfilled for more than 8 years, with a particle size of 0.5-4mm and a moisture content of 20-30%.

The sugar is commercially available sucrose, glucose, mannose, fructose, raffinose, lactose or starch.

The present invention has following advantage:

1. Since the raw material used in the present invention is the domesticated cover layer material after adding sugar solution, it can effectively promote the methane oxidation efficiency of the cover layer. Moreover, the process is simple, and the waste is treated by waste to realize the reduction of greenhouse gas emissions in landfills The method has obvious social and economic benefits.

2. When the present invention is operated according to the conventional covering process with a final covering layer of 40-60 cm, the methane oxidation efficiency can reach 810 g/(m ² ·d), which is 2 to 3 times higher than that of common landfill covering materials. times.

3. The invention has low cost and simple process, and is especially suitable for improving the methane oxidation efficiency of the covering layer in small and medium domestic waste landfills, and can be widely popularized.

Description of drawings

Fig. 1 is a process flow diagram of the present invention

Fig. 2 is the utilization amount of different sugars by mixed bacteria in the mineralized garbage of the present invention

Fig. 3 is the effect of adding different sugars of the present invention on the concentration of mineralized garbage mixed bacteria

Fig. 4 is the curve diagram of the influence of adding sucrose of the present invention on the oxidation of methane from mineralized waste

Fig. 5 is the curve diagram of the influence of adding starch of the present invention on the oxidized methane of mineralized garbage

Fig. 6 is the curve diagram of the influence of adding mannose of the present invention on the oxidation of methane from mineralized garbage

Fig. 7 is the curve diagram of the influence of the addition of lactose of the present invention on the oxidation of methane from mineralized waste

Fig. 8 is the curve diagram of the influence of adding fructose of the present invention on the oxidation of methane from mineralized garbage

Fig. 9 is the curve diagram of the influence of the addition of raffinose of the present invention on the oxidation of methane from mineralized waste

Detailed ways

Example 1

Seven kinds of sugars were selected for carbon source optimization experiments, including sucrose, mannose, lactose, raffinose, starch, fructose and glucose. They were respectively added into water and stirred evenly to form a sugar solution, and the initial concentration of each sugar solution was 30.0 g/L.

Mix 500mL of distilled water with 10g of mineralized garbage to obtain a mixed bacterial solution rich in methane oxidizing microorganisms. The sugar solution was added into the mixed bacterial solution according to 3.0g/L to investigate the consumption after 70h. The consumption of different sugars by the mixed bacterial solution can be determined by the consumption concentration of sugar, and the sugar concentration is detected by the anthrone sulfate method. Centrifuge the mixed bacterial solution containing sugar to obtain a sugar solution without bacteria. Take 2.5mL of the above sugar solution and dilute it with a 50mL volumetric flask. Take 1mL and place it in a 10mL test tube with a stopper and a scale. Add 4mL of anthrone reagent respectively, boil it for 10 minutes, take it out, immediately cool it with tap water, and leave it at room temperature for about 10 minutes to obtain a chromogenic solution of sugar, and measure the absorbance at 635nm. It can be seen from Figure 2 that all 7 kinds of sugar compounds can be utilized by the mixed bacterial solution, and the consumption of raffinose is the fastest, which shows that the raffinose has a better promoting effect on the growth of the mixed bacteria.

The absorbance of the bacteria solution can qualitatively characterize the concentration of the bacteria, and the higher the absorbance, the better the growth of the bacteria. It is detected by a spectrophotometer with a wavelength of 560 nm. Use a 5mL glass syringe to extract about 3mL of the mixed bacterial solution added with sugar solution and add it to the cuvette, using distilled water as a reference. Please see Figure 3. From the absorbance of the bacterial solution, it can be seen that the growth of the bacterial cells is better with raffinose and mannose as carbon sources. While sucrose, starch and glucose were the carbon sources, the growth was normal. The growth of bacteria qualitatively characterizes the growth of methane oxidizing microorganisms, and the ability of methane biooxidation needs to be judged by the actual oxidation rate of methane gas, please refer to Example 2.

Example 2

Six carbohydrate compounds were selected, including sucrose, mannose, lactose, raffinose, starch and fructose. Add them into water respectively and stir to form a sugar solution evenly. The initial concentration of each sugar solution is 1.0g/L. 20-30% stable mineralized waste) in a sealed serum bottle, and methane was flushed into the bottle to simulate the actual situation of a domestic waste landfill. Investigate the oxidation of methane by its mineralized waste. The determination of methane and carbon dioxide produced in the gas phase is performed by gas chromatography: the gas chromatograph is the GC-14B type of SHIMADZU company, the thermal conductivity detector, the stainless steel packed column, the column length is 2m; the carrier is GDX-104, 80-100 mesh; The carrier gas is hydrogen, the flow rate of the carrier gas is 30mL/min, and the bridge current is 120mA; the temperature of the detector, injector and chromatographic column are respectively: 90°C, 40°C, and 40°C; a 1mL gas sampling needle is used for sampling, and the injection volume 0.2mL. The volume fraction of the components was obtained by converting the standard curve, the consumption of methane was used to characterize the ability of the mineralized waste to degrade methane, and the amount of carbon dioxide produced was used to characterize the metabolic characteristics of the bacteria in the mineralized waste.

From Figures 4 to 9, it can be seen that the mineralized waste added with sugar has a strong methane consumption capacity. Among them, when mannose was used as carbon source, the methane degradation ability of mineralized garbage was relatively weak, and the methane content dropped from 30% to about 10% after 30 days of cultivation (Fig. 4). Carbon source during the experiment (Figure 5 and Figure 6).

It can be seen from Figure 7 that after 15 days of cultivation of the mineralized waste with sucrose as the carbon source, the methane decreased significantly, and the complete consumption of methane was realized within 1 week. A similar phenomenon also appeared in starch, and the rapid degradation of methane occurred after 10 days of culture, and the methane was completely consumed within the next 10 days (Figure 8). This shows that the metabolic pathway using sucrose and starch as carbon source is very similar to the metabolic pathway using methane as carbon source, so it can ensure that the bacteria can maintain the activity of biological enzymes related to methane oxidation while utilizing sugar. In addition, mineralized waste with added sugar basically needs 7 to 10 days of domestication (placed at room temperature) to ensure the activity of methane oxidation. Taking the mineralized garbage added with starch as an example, the conversion shows that the methane oxidation rate is 810g/(m ² ·d), which is about 3 times higher than the blank experiment with no sugar solution.

It can be seen from Figure 9 that the mineralized garbage with lactose as the carbon source can degrade methane well, but at the same time, it is found that during the process of methane degradation, carbon dioxide does not increase significantly, which shows that methane is mainly converted into bacteria.

Claims (1)

1. A method for strengthening methane oxidation of landfill overburden, is characterized in that: first, according to the ratio of adding 0.5～3kg sugar in every ton of mineralized waste, measure sugar, described sugar is commercially available mannose, Fructose, sucrose, raffinose, lactose or starch; then, add 1 part of sugar by mass to 100 parts of water by mass, stir evenly, configure it as a sugar solution, add it to mineralized waste, mix well, and then let it stand at room temperature for 7~ After 10 days, it becomes the covering layer material; finally, after the completion of the domestic waste landfill unit operation, the covering layer material is evenly spread on the surface of the domestic waste according to the conventional covering process with a final covering layer thickness of 40-60cm; after testing, when adding When the sugar is starch, the methane oxidation efficiency reaches 810g/(m ² ·d); The mineralized waste is landfilled for more than 8 years, with a particle size of 0.5-4mm and a moisture content of 20-30%.

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