CN111689666A

CN111689666A - Method for improving methane production by anaerobic fermentation of excess sludge

Info

Publication number: CN111689666A
Application number: CN202010566117.1A
Authority: CN
Inventors: 高俊玲; 李文涛; 杨子新; 魏文霞; 王辰风; 孙庆; 高云鹏
Original assignee: Shaanxi University of Science and Technology
Current assignee: Shaanxi University of Science and Technology
Priority date: 2020-06-19
Filing date: 2020-06-19
Publication date: 2020-09-22

Abstract

The invention discloses a method for improving the methane production of excess sludge through anaerobic fermentation, and belongs to the technical field of methane production of excess sludge through anaerobic fermentation. The preparation method comprises the following steps of mixing the residual sludge and the inoculated sludge in a ratio of 3: 1, adding iron mud into the mixed sludge according to the proportion that 1g of iron mud is added into every 100ml of residual sludge, filling nitrogen for 10min before fermentation, removing oxygen, then adjusting the temperature to enable the whole reaction device to react at 35 ℃, adding a stirring instrument into the reaction device to accelerate the methane production process, and stirring once every 10 min. Compared with the method for producing methane by using excess sludge alone, the method for producing methane by using iron mud to strengthen excess sludge adopted by the preparation method improves the gas production by 87.9%, and compared with the method for producing methane by adding rust, the method improves the gas production by about 24.1%.

Description

Method for improving methane production by anaerobic fermentation of excess sludge

Technical Field

The invention relates to the technical field of excess sludge anaerobic fermentation methane production, in particular to a method for improving the methane production of excess sludge anaerobic fermentation.

Background

The excess sludge is the waste generated in the sewage treatment process of the sewage treatment plant by the biochemical method, the yield of the excess sludge is about 0.3-0.5% of the sewage yield, the water pollution condition is increasingly serious along with the increase of the population number and the rapid development of economy in China, and the continuous increase of sewage plants becomes a necessary measure. The amount of excess sludge produced and the cost of disposal are also increasing. The sludge yield of sewage plants in China is large, but most of the sewage plants are not effectively stabilized. The secondary pollution problem is an obvious result of rapid increase of sludge yield, and in addition, the sludge treatment cost accounts for more than 30% of the operation cost of the sewage plant due to the sludge treatment cost problem, and the sludge treatment problem becomes a great burden for the normal operation of the sewage plant. Therefore, how to reasonably treat the sludge and realize the 'three-transformation' (harmlessness, reduction and recycling) of the sludge becomes an important environmental problem at present. The existing excess sludge disposal methods mainly comprise sanitary landfill, incineration, aerobic composting, anaerobic digestion and the like. And research aiming at anaerobic digestion of excess sludge has become the focus and focus of the current research.

Anaerobic digestion of sludge refers to the conversion of biodegradable organic matters in sludge into CH under the action of anaerobic microorganisms₄、CO₂And the biochemical process of stabilizing substances can effectively realize the stabilization, resource utilization and energy regeneration of the municipal sludge. The anaerobic digestion technology has the advantages of low energy consumption and convenient operation and management, can recover clean energy such as methane and the like, and is widely applied to the field of treatment and disposal of solid wastes such as agricultural solid wastes, kitchen wastes, municipal sludge and the like, but methanogens have strict requirements on anaerobic environment, are narrow in the range of the most suitable pH value, are sensitive to toxic and harmful substances, have the problems of long treatment period, low gas production rate and the like in the practical application process, and limit the development of the anaerobic digestion technology.

The Fenton process is an advanced treatment technology widely applied at present, and has incomparable chemical oxidation method when treating organic wastewater difficult to degradeThe method has been successfully applied to the treatment of various industrial wastewater so far. The Fenton process combines the characteristics of oxidation-coagulation and utilizes H₂O₂The strong oxidizing property of hydroxyl free radicals generated under the catalytic action of ferrous iron oxidizes and removes various complex pollutants which are difficult to be biochemically degraded in the wastewater. Fe (OH) generated by Fenton process reaction₃The colloid particles which are destabilized in water and suspended matters are carried to be transferred into chemical sludge together, namely Fenton iron mud. The Fenton iron mud is solid waste, and if the Fenton iron mud cannot be properly treated, the Fenton iron mud can destroy the soil structure, pollute water resources, occupy a large amount of land, and threaten human health by pathogens. Therefore, how to reasonably dispose the Fenton iron mud is a hot spot of current research.

At present, the method for producing methane by enhancing the anaerobic fermentation of excess sludge by utilizing Fenton iron mud has no research, and the hot spot for researching the method for producing methane by enhancing the anaerobic fermentation of sludge is mainly concentrated on adding iron substances, but the adding cost is higher, and the method has certain limitation in the aspect of practical application.

Disclosure of Invention

The invention aims to solve the problems that the traditional excess sludge anaerobic fermentation methane production technology has less gas production rate and can not meet the existing production requirements. Therefore, the method for improving the methane production of the excess sludge through anaerobic fermentation is provided, and Fe (OH) in the Fenton iron mud is utilized₃Fe generated in the process of reacting with excess sludge³⁺And the methane yield of the fermentation of the excess sludge is enhanced, so that the effect of treating waste by waste is achieved.

The invention provides a method for improving the methane production of excess sludge through anaerobic fermentation, which comprises the steps of mixing the excess sludge and inoculated sludge to obtain mixed sludge, adding iron mud into the mixed sludge according to the proportion that 1g of iron mud is added into each 100ml of excess sludge, and then performing anaerobic fermentation.

Preferably, the volume ratio of the residual sludge to the inoculated sludge is 3: mixing at a ratio of 1.

Preferably, nitrogen is filled before anaerobic fermentation, oxygen in the reaction device is removed, then the temperature is adjusted, and the fermentation temperature is controlled at 32-35 ℃.

Preferably, the anaerobic fermentation container is internally provided withIs provided with a stirring device, and the rotating speed of the stirring device is 90 r.min^-1The frequency is 1 day and 4 times, each time stirring for 1.5 h.

Compared with the prior art, the invention has the following beneficial effects: the iron mud adopted by the invention is also a solid waste generated by Fenton reaction, and cannot be properly treated at present, so that the Fenton iron mud and the excess sludge are utilized for co-fermentation, the methane yield generated by fermentation of the excess sludge can be accelerated, and the iron mud and the excess sludge can be treated together, thereby achieving the effect of treating waste by waste.

Compared with the method for producing methane by using excess sludge alone, the method for producing methane by using iron mud to strengthen excess sludge adopted by the invention has the advantages that the gas production is improved by 87.9%, compared with the method for adding rust, the gas production is improved by 24.1%, and the method meets the three-conversion standard required by the state at present.

Drawings

FIG. 1 shows the effect of iron sludge in different amounts on the amount of methane produced.

FIG. 2 is a comparison of the effect of iron mud and rust on the amount of methane produced.

Detailed Description

Detailed description of the preferred embodimentsthe following detailed description of the present invention will be made with reference to the accompanying drawings 1-2, although it should be understood that the scope of the present invention is not limited to the specific embodiments. All other examples, which can be obtained by a person skilled in the art without inventive step based on the examples of the present invention, are within the scope of the present invention, and the test methods without specifying the specific conditions in the following examples are generally performed according to the conventional conditions or according to the conditions suggested by the respective manufacturers.

Example 1

A method for improving the methane production of excess sludge through anaerobic fermentation is to mix the excess sludge and inoculated sludge in a ratio of 3: 1, adding iron mud into the mixed sludge according to the proportion of adding 1g of iron mud into every 100ml of residual sludge, filling nitrogen for 10min before fermentation, removing oxygen in a reaction device, adjusting the temperature to ensure that the whole reaction device reacts at about 35 ℃, adding a stirring instrument into the reaction device to accelerate the methane production process, wherein the rotating speed is 90 r.min^-1The frequency is 1 day and 4 times, each time of stirring is 1.5 hours, and the whole methane production process lasts about two months until the gas production is finished.

Example 2

And adding part of iron mud into the sludge by taking the residual sludge as a treatment object, and checking the daily gas production condition of the sludge. The residual sludge comes from a certain sewage treatment plant of the west ampere, the inoculated sludge comes from a certain brewery of the west ampere, and the Fenton iron sludge comes from a certain paper mill of the Wugong industry.

And (3) analyzing the components of the residual sludge and the Fenton iron mud:

(1) component analysis of excess sludge:

selecting a certain sludge sample, centrifuging for 10min at 5000r/min, filtering by a 0.45-micron filter membrane, and performing related physicochemical index determination, wherein the indexes mainly comprise pH, TS, VS, SCOD, TCOD, polysaccharide and the like, and the basic content of the residual sludge is described by the index determination, so that the method provides help for the subsequent methanogenesis research.

Table 1 shows the basic components of excess sludge

(2) And (3) analyzing the components of the iron mud:

determining the content of organic substances by using a visible light colorimetric method, determining the proportion of elements in the organic substances by using XRD (X-ray diffraction), and determining the proportion of iron elements in the Fenton sludge by using ICP (inductively coupled plasma emission spectroscopy) for measuring the content of inorganic elements in the Fenton sludge; and the iron content in the Fenton sludge is further determined by using an atomic absorption spectrometer, and the iron consumption in the methane production process is specifically analyzed after the iron content in the iron sludge is determined.

Table 2 shows the basic components of Fenton iron mud

And (3) analyzing the methanogenesis condition:

taking 300mL of residual sludge to be treated, inoculating 100mL of sludge, adding the sludge into 5 reaction fermentation tanks respectively according to a proportion, adding 0g (blank), 1g, 2g, 3g, 4g and 5g of iron mud which are marked as R0, R1, R2, R3, R4 and R5 into 6 fermentation tanks respectively, filling nitrogen into the 6 fermentation tanks for 10min respectively, discharging air, placing the fermentation tanks into a constant-temperature water bath kettle at 35 ℃, arranging a stirrer in the fermentation tanks, and setting the rotating speed to be 90 r.min^-1The frequency is 1 day and 4 times, each time stirring is 1.5 hours, the upper part of the fermentation tank is provided with an air outlet, and the condition of methane production in the fermentation tank is analyzed.

In addition, a set of contrast experiments of iron mud and iron rust are also carried out, 300mL of excess sludge is taken, 100mL of inoculated sludge is added into 6 reaction fermentation tanks in proportion, 1g of iron mud, 2g of iron mud, 3g of iron mud and 1g of iron rust, 2g of iron rust and 3g of iron rust are respectively added into 6 fermentation tanks, nitrogen is respectively filled into the 6 fermentation tanks for 10min, air is discharged, the fermentation tanks are placed in a 35 ℃ constant-temperature water bath kettle, a stirrer is arranged in the fermentation tanks, and the rotating speed is 90 r.min^-1The frequency is 1 day and 4 times, each time stirring is 1.5 hours, the upper part of the fermentation tank is provided with an air outlet, and the condition of methane production in the fermentation tank is analyzed.

After the iron mud is compared with the iron rust, the iron mud in the total gas production amount corresponding to the addition amount of 1g, 2g and 3g is improved by 22.9 percent, 24.1 percent and 23.0 percent compared with the iron rust after the same amount of the iron mud and the iron rust are added.

As is clear from the above results, the Fenton iron mud of the present invention contains Fe (OH) as a main component₃And organic matters, and the rust is a simple chemical component and is different from the components.

The Fenton iron mud used in the invention is dangerous solid waste, only can be subjected to harmless treatment, and the rust has utilization value in other aspects, so that the invention realizes resource utilization of the dangerous solid waste.

Compared with the single production of methane by the excess sludge, the Fenton iron mud used in the invention enhances the methane production by the excess sludge by 87.9%, and compared with rust, the Fenton iron mud enhances the methane production by the excess sludge by 23%, the rust is only a simple chemical component, and the iron mud contains organic matters such as humic acid, so that the hydrolysis and ionization effects in the methane production process can be enhanced, and the methane production rate is increased.

When the claims of the present invention refer to numerical ranges, it should be understood that two endpoints of each numerical range and any value between the two endpoints can be selected, and since the steps and methods adopted are the same as those of the embodiment, the present invention describes a preferred embodiment and effects thereof in order to prevent redundancy. Additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims

1. A method for improving the methane production of excess sludge through anaerobic fermentation is characterized in that the excess sludge and inoculated sludge are mixed to obtain mixed sludge, iron sludge is added into the mixed sludge according to the proportion that 1g of the iron sludge is added into each 100ml of the excess sludge, and then anaerobic fermentation is carried out.

2. The method for enhancing the production of methane by anaerobic fermentation of excess sludge according to claim 1, wherein the excess sludge is mixed with the inoculated sludge in a volume ratio of 3: 1, were mixed.

3. The method for improving the methane production of the excess sludge through the anaerobic fermentation according to claim 1, wherein nitrogen is filled in before the anaerobic fermentation, oxygen in a reaction device is discharged, and then the temperature is adjusted, wherein the fermentation temperature is controlled to be 32-35 ℃.

4. The method for improving the methane production through the anaerobic fermentation of the excess sludge according to claim 1, wherein a stirring device is further arranged in the anaerobic fermentation container, and the rotating speed of the stirring device is 90 r-min^-1The frequency is 1 day and 4 times, each time stirring for 1.5 h.