CN111518843A - Anaerobic fermentation hydrogen production method and additive using excess sludge as raw material - Google Patents

Abstract

The invention relates to an anaerobic fermentation hydrogen production method and an additive using excess sludge as a raw material. The hydrogen production method is as follows: S1: using excess activated sludge produced by a sewage treatment plant as a raw material, sedimentation, and removing the upper surface of the excess activated sludge clear liquid to obtain anaerobic fermentation raw materials; S2: add anaerobic fermentation raw materials to the fermentation reactor, add ferrate, stir evenly, and maintain the anaerobic environment in the fermentation reactor; S3: control the temperature and continue the fermentation reaction , the hydrogen produced will be output continuously or intermittently. Compared with the prior art, the ferrate added in the present invention can not only destroy the structure of the excess sludge, promote the release of a large amount of biodegradable organic matter in the sludge, but also significantly inhibit and reduce the hydrogen consumption of hydrogen-phagocytic methanogens and the like. The activity and abundance of microorganisms can significantly promote the amount of hydrogen produced by the fermentation of excess sludge; the operation is simple, and it is convenient for long-term operation and management; it can significantly increase the amount of hydrogen produced by the resource of excess sludge.

Description

A kind of anaerobic fermentation hydrogen production method and additive using surplus sludge as raw material

technical field

The invention relates to the technical field of environmental protection and sludge treatment and resource utilization, in particular to a method for producing hydrogen by anaerobic fermentation using excess sludge as a raw material and an additive.

Background technique

The activated sludge process has been widely used in urban sewage treatment. Although this process can effectively treat sewage, it also produces a large amount of process by-products, namely surplus activated sludge. It is estimated that in 2020, the output of excess sludge in my country is expected to reach 60 million metric tons (with a moisture content of 80%). Excess sludge concentrates a lot of toxic and harmful substances, such as pathogens, heavy metals, persistent organic pollutants, etc. If not treated effectively, the pollutants contained will pose a huge threat to human health and the ecological environment. At present, sludge treatment and disposal costs are high, accounting for 60% of the total operating cost of sewage treatment plants, which poses a huge challenge to the long-term operation of sewage treatment plants. Meanwhile, excess sludge is rich in organic matter, such as proteins, polysaccharides, lipids, and polyhydroxyalkanoates, which usually account for 50-70% of sludge cells. With the increasing global demand for resources year by year, the whole society's understanding of sludge has also changed from "pollutant" to "resource bank".

At present, due to the massive emission of greenhouse gases, the problem of global warming is becoming more and more serious, so the development and utilization of clean energy has received extensive attention. Anaerobic sludge fermentation is a common method for sludge resource utilization at present, which can realize sludge reduction and resource recovery (such as volatile fatty acids and hydrogen). Hydrogen is a non-polluting, renewable and ideal fuel with high calorific value, which has received increasing attention worldwide. Using excess sludge to produce hydrogen by anaerobic fermentation not only realizes the effective treatment of sludge, but also generates valuable clean energy, which has important environmental significance. However, in the prior art, the amount and rate of hydrogen produced by anaerobic fermentation of sludge are relatively low, and it is difficult to achieve large-scale application.

CN109593791A discloses a method for utilizing low temperature thermal pretreatment combined with free ammonia treatment to improve the hydrogen production of excess sludge in anaerobic fermentation. treatment; step 2, performing FA treatment on the thermally pretreated sludge; and step 3, using the sludge as a substrate and inoculated sludge to carry out anaerobic fermentation to produce hydrogen. The technical scheme adopts the method of low temperature thermal pretreatment combined with free ammonia treatment to promote hydrogen production, which is equivalent to adding a low temperature pretreatment process, which makes the overall process flow complicated and the energy consumption increases.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a kind of anaerobic fermentation hydrogen production method and additives using excess sludge as raw material in order to overcome the defects of the above-mentioned prior art, which not only realizes the reduction of sludge, but also effectively reduces environmental pollution. , and the hydrogen produced is a clean, sustainable energy with high calorific value, which can effectively alleviate the situation of energy shortage and global warming, in line with the concept of sustainable development.

The object of the present invention can be realized through the following technical solutions:

The anaerobic fermentation hydrogen production method using excess sludge as raw material in the present invention is characterized in that, comprising the following steps:

S1: take the surplus activated sludge produced by the sewage treatment plant as the raw material, settle, remove the supernatant of the surplus activated sludge, and obtain the anaerobic fermentation raw material;

S2: add the anaerobic fermentation raw material to the fermentation reactor, add ferrate, stir evenly, and keep the fermentation reactor in an anaerobic environment;

S3: Control the temperature, continuously carry out the fermentation reaction, and output the generated hydrogen continuously or intermittently.

Further, in step S1, the settlement is natural settlement.

Further, in step S1, the ambient temperature during the settling process is 3-5°C, and the settling time is 24-48h.

Further, in step S2, the dosage of ferrate is 0.03-0.15g/g TSS. The dosage within this range can achieve a better effect of promoting hydrogen production. If it is too high, it will gradually inhibit the activity of various active bacteria. If it is too small, its promoting effect will not be obvious.

Further, in step S2, the dosage of ferrate is 0.06-0.09 g/g TSS.

Further, in step S2, the anaerobic environment of the fermentation reactor is maintained in the form of introducing nitrogen gas.

Further, in step S2, the ferrate includes potassium ferrate and sodium ferrate.

Further, the stirring speed during the reaction is 120-180 rpm/min. The stirring speed above 120 can achieve repeated stirring and dispersing effect, and when it exceeds 180 rpm/min, the effect of promoting hydrogen production will decrease because of affecting the hydrogen production process of active bacteria.

Further, in step S3, the fermentation reaction temperature is 18-42°C, and under this condition, the activity of the hydrogen-producing microorganisms is strong; in order to obtain the maximum hydrogen production, the fermentation reaction time is 3-10 d.

Further, in step S3, the fermentation reaction temperature is 25-37°C.

In the present invention, an additive for promoting hydrogen production by anaerobic fermentation of excess sludge in a sewage treatment plant comprises one or both of potassium ferrate and sodium ferrate.

In the process of sludge anaerobic fermentation, under the combined action of microorganisms, the anaerobic degradation process of organic matter can be divided into six stages: dissolution stage, hydrolysis stage, acidification stage, acetation stage, homoacetogenic stage and methanation stage . The organic matter in the sludge is composed of extracellular polymers and intracellular organic matter. Before they can be used for fermentative hydrogen production, they need to be converted from solid phase to liquid phase through a sludge dissolution stage. However, the rate of sludge dissolution is usually at a low level due to the protective effects of cell walls/membranes and extracellular polymers, and the dissolution phase is considered to be the rate-limiting step for hydrogen production by anaerobic fermentation. In this technical solution, the target product hydrogen is an intermediate product of the sludge anaerobic fermentation process. It is produced in the acidification and acetation stages, and then will be destroyed by hydrogen-consuming microorganisms such as hydrogenophilic methanogens in the homoacetogenic stage and the methanation stage. consume. Therefore, to promote the dissolution of the sludge and provide more biodegradable substrates for the hydrogen-producing microorganisms, the ferrate used in the present invention promotes the activity and abundance of the hydrogen-producing microorganisms and reduces the activity and abundance of the hydrogen-consuming microorganisms. The key to hydrogen production by oxygen fermentation.

In this technical solution, the ferrate used is a green and environmentally friendly strong oxidant, which can destroy the cell structure of the sludge and release a large amount of solid-phase organic matter into the liquid phase, thereby being transformed and utilized by microorganisms.

In addition, ferrate can not only significantly inhibit the activity of hydrogen-consuming microorganisms, but also reduce their abundance, thereby significantly increasing the yield of hydrogen produced by anaerobic fermentation of sludge.

Compared with the prior art, the present invention has the following advantages:

1) The present invention utilizes the by-product-excess sludge produced by the urban sewage treatment plant to produce hydrogen, which not only realizes the reduction of sludge, effectively reduces environmental pollution, but also produces hydrogen that is clean and sustainable. Energy with high calorific value can effectively alleviate the situation of energy shortage and global warming, which is in line with the concept of sustainable development.

2) In the prior art, the amount and rate of hydrogen produced by anaerobic fermentation of sludge are relatively low, and the ferrate used in the present invention can significantly promote the lysis of sludge cells, so that proteins, sugars, etc. in the sludge can be biodegradable. A large amount of degraded organic matter is released, so as to provide more available substrates for hydrogen-producing microorganisms, and improve the rate and output of hydrogen production. The overall process is simple, and only the addition of additives can achieve the promotion effect, which is conducive to the realization of large-scale promotion and production. application.

3) The ferrate used in the present invention can inhibit the activity of hydrogen-consuming microorganisms and can significantly reduce their relative abundance, thereby greatly reducing the consumption of hydrogen and promoting the accumulation of hydrogen.

Description of drawings

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

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

Example 1

(1) In a plexiglass reactor with a working volume of 1 L, the excess sludge produced by the urban sewage treatment plant was placed at 3 °C for natural sedimentation for 24 hours, and the supernatant was drained to obtain the raw material for fermentation (that is, the excess sludge sample). , the same as in the following examples).

(2) Add ferrate of 0.05g/g TSS to the reactor, fill the reactor with nitrogen, continue for 10min to remove oxygen, seal the reactor and put it into a shaker for anaerobic fermentation. Through the combined action of microorganisms and ferrate in the sludge, the organic matter in the sludge is converted into hydrogen. The fermentation temperature of the reactor was controlled to be 25±1°C, the stirring speed of the shaker was 120 rpm/min, the residence time of the sludge in the reactor was 3 d, and the output of hydrogen produced was 4.03 mL/g VSS.

Example 2

(1) In a plexiglass reactor with a working volume of 1L, the excess sludge produced by the urban sewage treatment plant was placed at 5 °C for natural sedimentation for 48 hours, and the supernatant was drained to obtain the raw material for fermentation (that is, the excess sludge sample). , the same as in the following examples).

(2) Add ferrate of 0.07g/g TSS to the reactor, fill the reactor with nitrogen, continue for 10min to remove oxygen, seal the reactor and put it into a shaker for anaerobic fermentation. Through the combined action of microorganisms and ferrate in the sludge, the organic matter in the sludge is converted into hydrogen. The fermentation temperature of the reactor was controlled to be 37±1°C, the stirring speed of the shaking table was 180 rpm/min, the residence time of the sludge in the reactor was 3 d, and the output of hydrogen produced was 5.82 mL/g VSS.

Example 3

(1) In a plexiglass reactor with a working volume of 1 L, the excess sludge produced by the urban sewage treatment plant was placed at 4 °C for natural sedimentation for 24 hours, and the supernatant was drained to obtain the raw material for fermentation (that is, the excess sludge sample). , the same as in the following examples).

(2) Add ferrate of 0.03g/g TSS to the reactor, fill the reactor with nitrogen, continue for 10min to remove oxygen, seal the reactor and put it into a shaker for anaerobic fermentation. Through the combined action of microorganisms and ferrate in the sludge, the organic matter in the sludge is converted into hydrogen. The fermentation temperature of the reactor was controlled to be 30±1°C, the stirring speed of the shaker was 150 rpm/min, the residence time of the sludge in the reactor was 3 d, and the output of hydrogen produced was 2.67 mL/g VSS.

Example 4

(1) In a plexiglass reactor with a working volume of 1 L, the excess sludge produced by the urban sewage treatment plant was placed at 4 °C for natural sedimentation for 24 hours, and the fermented raw materials were obtained after the supernatant was drained.

(2) Add ferrate of 0.03g/g TSS to the reactor, fill the reactor with nitrogen, continue for 10min to remove oxygen, seal the reactor and put it into a shaker for anaerobic fermentation. Through the combined action of microorganisms and ferrate in the sludge, the organic matter in the sludge is converted into hydrogen. The fermentation temperature of the reactor was controlled to be 30±1°C, the stirring speed of the shaker was 150 rpm/min, the residence time of the sludge in the reactor was 10 d, and the output of hydrogen produced was 3.10 mL/g VSS.

Example 5

(1) In a plexiglass reactor with a working volume of 1 L, the excess sludge produced by the urban sewage treatment plant was placed at 4 °C for natural sedimentation for 24 hours, and the fermented raw materials were obtained after the supernatant was drained.

(2) Add ferrate of 0.06g/g TSS to the reactor, fill the reactor with nitrogen, continue for 10min to remove oxygen, seal the reactor and put it into a shaker for anaerobic fermentation. Through the combined action of microorganisms and ferrate in the sludge, the organic matter in the sludge is converted into hydrogen. The fermentation temperature of the reactor was controlled to be 30±1°C, the stirring speed of the shaker was 150 rpm/min, the residence time of the sludge in the reactor was 10 d, and the output of hydrogen produced was 4.90 mL/g VSS.

Example 6

(1) In a plexiglass reactor with a working volume of 1 L, the excess sludge produced by the urban sewage treatment plant was placed at 4 °C for natural sedimentation for 24 hours, and the fermented raw materials were obtained after the supernatant was drained.

(2) Add ferrate of 0.09g/g TSS to the reactor, fill the reactor with nitrogen, continue for 10min to remove oxygen, seal the reactor and put it into a shaker for anaerobic fermentation. Through the combined action of microorganisms and ferrate in the sludge, the organic matter in the sludge is converted into hydrogen. The fermentation temperature of the reactor was controlled to be 30±1°C, the stirring speed of the shaking table was 150 rpm/min, the residence time of the sludge in the reactor was 5 d, and the output of hydrogen produced was 8.30 mL/g VSS.

Comparative Example 1

(1) In a plexiglass reactor with a working volume of 1 L, the excess sludge produced by the urban sewage treatment plant was placed at 4 °C for natural sedimentation for 24 hours, and the fermented raw materials were obtained after the supernatant was drained. No ferrate was added, nitrogen was charged into the reactor for 10 min to remove oxygen, and the reactor was sealed and placed in a shaker for anaerobic fermentation. Through the action of microorganisms contained in the sludge itself, the organic matter in the sludge is converted into hydrogen. The fermentation temperature of the reactor was controlled to be 30±1°C, the stirring speed of the shaker was 150 rpm/min, the residence time of the sludge in the reactor was 10 d, and the output of hydrogen produced was 1.47 mL/g VSS.

The hydrogen production of the implementation case and the comparative example is shown in Table 1:

As can be seen from the table, the hydrogen production of Examples 1 to 4 is significantly higher than that of Comparative Example 1. In particular, the hydrogen production of Example 4 under optimal conditions has the highest improvement compared to that of Comparative Example 1. Significantly.

The foregoing description of the embodiments is provided to facilitate understanding and use of the present invention by those of ordinary skill in the art. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Without departing from the spirit and technical solutions of the present invention, those skilled in the art can make many possible modifications to the technical solutions of the present invention, or modify them into equivalent embodiments with equivalent changes. Therefore, any simple improvements and modifications made without departing from the scope of the present invention should fall within the protection scope of the present invention.

Claims (10)

1. a kind of anaerobic fermentation hydrogen production method with surplus sludge as raw material, is characterized in that, comprises the following steps: S1: take the surplus activated sludge produced by the sewage treatment plant as the raw material, settle, remove the supernatant of the surplus activated sludge, and obtain the anaerobic fermentation raw material; S2: add the anaerobic fermentation raw material to the fermentation reactor, add ferrate, stir evenly, and keep the fermentation reactor in an anaerobic environment; S3: Control the temperature, continuously carry out the fermentation reaction, and output the generated hydrogen continuously or intermittently. 2 . The method for producing hydrogen by anaerobic fermentation using excess sludge as a raw material according to claim 1 , wherein in step S1 , the sedimentation is natural sedimentation. 3 . 3 . The method for producing hydrogen by anaerobic fermentation using excess sludge as a raw material according to claim 1 , wherein in step S1 , the ambient temperature in the sedimentation process is 3 to 5° C., and the sedimentation time is 24 to 24° C. 4 . 48h. 4 . The method for producing hydrogen by anaerobic fermentation using excess sludge as a raw material according to claim 1 , wherein in step S2 , the dosage of ferrate is 0.03-0.15 g/g TSS. 5 . 5 . The method for producing hydrogen by anaerobic fermentation using excess sludge as a raw material according to claim 4 , wherein in step S2 , the dosage of ferrate is 0.06-0.010 g/g TSS. 6 . 6 . The method for producing hydrogen by anaerobic fermentation using excess sludge as a raw material according to claim 1 , wherein in step S2 , the anaerobic environment of the fermentation reactor is maintained by feeding nitrogen gas. 7 . 7 . The method for producing hydrogen by anaerobic fermentation using excess sludge as a raw material according to claim 1 , wherein, in step S2, the ferrate comprises potassium ferrate and sodium ferrate. 8 . 8 . The method for producing hydrogen by anaerobic fermentation using excess sludge as a raw material according to claim 1 , wherein, in step S3 , the fermentation reaction temperature is 18-42° C., and the fermentation reaction time is 3-10 d. 9 . 9 . The method for producing hydrogen by anaerobic fermentation using excess sludge as a raw material according to claim 8 , wherein, in step S3 , the fermentation reaction temperature is 25-37° C. 10 . 10. An additive for promoting hydrogen production by anaerobic fermentation of excess sludge in a sewage treatment plant, characterized in that it comprises one or both of potassium ferrate and sodium ferrate.

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