CN102020404A - Method for improving fermentation capability of slurry dry process - Google Patents

Abstract

The invention relates to a method for improving the performance of sludge dry fermentation, which belongs to the field of solid waste resource utilization, and can solve the problem of difficult transmission and diffusion of reaction intermediate products and energy in the medium due to the high viscosity of the reaction substrate and high TS concentration, and the The sludge contains a large amount of refractory substances, and the cell wall structure of microbial residues restricts further biotransformation, resulting in slow hydrolysis and acidification, and low gas production rate. The steps are: pretreat the dewatered sludge under a microwave with a frequency of 915MHz and a power of 10~60kW for 3~10 minutes; cool the pretreated dewatered sludge to the selected fermentation temperature, After mixing evenly at a ratio of 5:1~3:1, put it in an anaerobic fermentation tank, and let it stand for 3~5 days in an airtight, non-stirring state; turn on the stirring motor, and control the stirring speed at 10~30r/min; continuously feed in and out , so that the residence time of the material in the anaerobic fermentation tank is 40-60 days. The invention can reduce sludge viscosity, increase dry fermentation rate and gas production, and save equipment investment and land occupation compared with wet fermentation.

Description

A method for improving sludge dry fermentation performance

technical field

The invention belongs to the field of solid waste recycling, and in particular relates to a method for improving the performance of sludge dry fermentation.

Background technique

The amount of dewatered sludge produced by urban sewage treatment plants due to the purification of domestic sewage is huge. At present, the annual collection capacity is about 26 million tons. The treatment and disposal of sludge in sewage treatment plants mostly use concentration and dehydration followed by landfill. This method not only occupies limited land resources, but also easily causes secondary pollution. In addition, the resource utilization rate of landfill is low, which does not conform to the principle of sustainable development in my country. In recent years, the global energy structure is undergoing a transition from fossil energy-based to the coexistence of multiple energy sources, and issues such as food security and environmental degradation have become increasingly prominent. Anaerobic fermentation technology is used to recover non-food biomass energy from sludge— — Biogas has gradually gained attention.

According to the solid content (TS) of the material in the reactor, anaerobic fermentation technology can be divided into wet fermentation (TS≤12%) and dry fermentation (TS≥20%). Wet fermentation technology has been applied in municipal sludge (TS is about 2%) digestion biogas production, anaerobic fermentation biogas production of livestock manure and anaerobic biogas production of organic waste, and the technologies in all aspects are relatively mature. Compared with the wet fermentation process, the dry fermentation process has the following advantages: (1) Large load, high volume capacity, and greatly reduced equipment volume; (2) Low or no water demand, saving water resources; (3) The production of biogas slurry is less, the water content of waste residue is low, and the cost of follow-up treatment is low; (4) the operation process is stable, and there are no problems such as scum and sediment in the wet process; (5) less odor emission, etc.

At present, in terms of dry fermentation, European countries have carried out the development of anaerobic fermentation technology and equipment for domestic waste with low moisture content. The research work on dry fermentation technology in our country is less and less systematic. Relevant dry fermentation methods are mainly aimed at agricultural straw (CN101338273, CN101338325) and organic waste (CN101381674A). There are no reports on the method of carrying out dry fermentation with dewatered sludge and the pretreatment method for improving the performance of sludge dry fermentation. .

During the sludge dry fermentation process, due to the high viscosity of the reaction matrix and the high concentration of TS, it is difficult to transfer and diffuse the reaction intermediate products and energy in the medium; in addition, due to the large amount of refractory substances in the sludge and the The microbial residues and cell wall structure limit further biotransformation, resulting in difficult reproduction of hydrolytic acidifying bacteria, insufficient substrate available in the methanogenic stage, and slow gas production rate, which is one of the important difficulties in the sludge dry fermentation process.

Contents of the invention

The purpose of the present invention is to overcome the problems of slow hydrolysis and acidification process, insufficient methanogenic substrate, and slow fermentation process due to the large amount of refractory substances and microbial residues in the material in the dry fermentation process of municipal sludge, and provide an improved Method for sludge dry fermentation performance.

The method that the present invention proposes improves sludge dry fermentation performance, concrete steps are as follows:

(1) Preprocessing

Adjust the moisture content of the dewatered sludge to make it >85%, and pretreat the dewatered sludge under a microwave with a frequency of 915MHz and a power of 10-60kW for 3-10 minutes, so that the moisture content of the dewatered sludge after pretreatment rate>75%;

(2) Fermentation start

Cool the pretreated dewatered sludge to the selected fermentation temperature, mix it evenly with the inoculated sludge, place it in an anaerobic fermentation tank, and let it stand for 3 to 5 days in a closed and non-stirred state; the dehydrated sludge after pretreatment The mass ratio of sludge to inoculated sludge is 5:1~3:1;

(3) Stable operation

After standing still for 3~5 days, turn on the stirring motor, and control its daily start time>8h. When stirring, control the stirring speed to 10~30r/min, so that the sludge fermentation intermediate product is fully mixed; start continuous feeding and discharging, The residence time of the material in the anaerobic fermentation tank is 40-60 days.

In the present invention, in the step (1) and the step (3), the temperature of the material is kept to be a certain temperature value in 35~40°C or 50~55°C, the temperature fluctuation is controlled to be less than or equal to 2°C, and the oxidation-reduction potential is less than or equal to -300mV; the step ( 2) The medium fermentation temperature is one of 35~40°C or 50~55°C, the temperature fluctuation is controlled to be ≤2°C, and the oxidation-reduction potential is ≤-300mV.

In the present invention, the inoculum sludge in step (2) can be dewatered sludge without pretreatment, granular sludge from other anaerobic reactors or biogas residue after anaerobic fermentation in the early stage.

In the present invention, sufficient stirring is required in step (3), and the rotating speed of the stirring rotor is controlled to 10-30r/min.

In the present invention, the feed in step (3) is dewatered sludge pretreated in step (1).

The present invention has the following advantages:

1. After microwave pretreatment, the viscosity of the material can be reduced by 50-70%, which is conducive to the full mass transfer of the dry fermentation process and the thorough mixing of microorganisms, enzymes and substrates;

2. Microwave pretreatment can destroy the cell wall structure of a large number of microbial residues in the sludge, dissolve the intracellular substances, and promote the decomposition of refractory substances in the sludge such as out-of-service polymers, which can improve the anaerobic degradability of the material , accelerate the process of hydrolysis and acidification, provide fermentation substrates for methanogens, and strengthen gas production.

3. Microwave pretreatment has high heating efficiency and low energy consumption. The high-temperature fermentation of pretreated materials can significantly speed up the fermentation process and increase the production rate.

Detailed ways

Below further illustrate the present invention by embodiment. 

Example 1:

Take 20kg of dewatered sludge from sewage plant A, add an appropriate amount of water, and adjust the moisture content to 87%; heat the material in a microwave heater with a frequency of 915MHz and a power of 10kW for 5 minutes, and the moisture content of the material after heating is measured to be 80%; Cool the sludge after microwave pretreatment to 35±1°C, mix it evenly with 6kg of dewatered sludge without pretreatment, put it into an anaerobic fermentation tank, turn on the temperature control device, and control the temperature of the material during the fermentation process to 35±1°C 1°C, start statically for 3 days; turn on the stirring motor at a speed of 15r/min, turn on the stirring motor for 1 hour and stop for 1 hour; start the gas metering and collection device; feed in and out 500g per day, and the feed is dehydrated sludge pretreated by microwave ; Monitor the material pH, gas production and gas production components every 3 days, and the fermentation process can be carried out stably.

Example 2:

Take 20kg of dewatered sludge from sewage plant B, add an appropriate amount of water, and adjust the moisture content to 90%; heat the material in a microwave heater with a frequency of 915MHz and a power of 10kW for 8 minutes, and the moisture content of the material after heating is measured to be 80%; Cool the sludge after microwave pretreatment to 55±1°C, mix it evenly with 7kg of fermented biogas residue in the previous stage, put it into the anaerobic fermentation tank, turn on the temperature control device, control the temperature of the material during the fermentation process to 55±1°C, and statically Start for 2 days; turn on the stirring motor at a speed of 15r/min, turn on the stirring motor for 1 hour, and stop it for 1 hour; start the gas metering and collection device; feed and discharge 900g per day, and the feed is dehydrated sludge pretreated by microwave; monitor every 2 days Material pH, gas production and gas production components, the fermentation process can be carried out stably.

Claims (4)

1. method that improves mud dry method leavening property is characterized in that concrete steps are as follows:

(1) pre-treatment

Regulate the dewatered sludge water ratio, make its water ratio 85%, it is that 915MHz, power are under the microwave of 10-60kW pre-treatment 3-10 minute that dewatered sludge is placed frequency, makes the water ratio through dewatered sludge after the pre-treatment〉75%;

(2) fermentation starting

Pretreated dewatered sludge is cooled to leavening temperature, mixes with seed sludge and be placed in the anaerobic fermentation tank, under airtight, no whipped state, left standstill 3-5 days; The mass ratio 5:1-3:1 of pretreated dewatered sludge and seed sludge;

(3) steady running

Leave standstill startup after 3-5 days, open agitator motor, control its opening time every day 8h, during stirring, the control mixing speed is 10-30r/min, makes sludge fermentation intermediate product thorough mixing; Beginning continuously feeding and discharging, making material residence time in anaerobic fermentation tank is 40-60 days.

2. the method for raising mud dry method leavening property according to claim 1, it is characterized in that the middle maintenance of step (1) and step (3) temperature of charge is a certain temperature value in 35-40 ℃ or 50-55 ℃, ≤ 2 ℃ of controlled temperature fluctuations, redox potential≤-300mV; Leavening temperature is a certain temperature value in 35-40 ℃ or 50-55 ℃ in the step (2) ,≤2 ℃ of controlled temperature fluctuations, and redox potential≤-300mV.

3. the method for raising mud dry method leavening property according to claim 1 is characterized in that seed sludge in the step (2) adopts the granule sludge of unpretreated dewatered sludge, other anaerobic reactors or the natural pond slag behind the early stage anaerobically fermenting.

4. the method for raising mud dry method leavening property according to claim 1 is characterized in that charging is through the pretreated dewatered sludge of step (1) in the step (3).