CS242979B1 - A method of stimulating biogas production in anaerobic methane sludge fermentation - Google Patents

Abstract

A mechanically or physically treated biomass suspension is added as a stimulating agent to the material intended for fermentation or directly to the anaerobic reactor in an amount of 0.1 to 10%, based on the organic dry matter of the processed material. Biomass taken from the reactor in which the actual process takes place or from another well-methanizing reactor is used to prepare the stimulating agent. The stimulating agent is prepared by mechanical disruption of biomass cells or by one to five repeated freezing and thawing of the biomass suspension at a temperature of -1 to 40 °C, preferably -8 °C, or by heating the biomass suspension for 5 to 60 minutes at a temperature of 80 to 100 °C, or by disruption of the cells of biomass microorganisms by ultrasound. The invention can be applied to all processes of anaerobic stabilization of organic substances, such as anaerobic stabilization of sewage sludge or other organic sludge and anaerobic wastewater treatment.

Description

The invention relates to increasing and accelerating biogas production during anaerobic methane fermentation of sludge, wastewater and other organic materials, for example during anaerobic stabilization of livestock excrement and during anaerobic wastewater treatment.

Anaerobic decomposition - methane fermentation of organic matter is a process in which a mixed culture of microorganisms gradually decomposes biodegradable organic matter under anaerobic conditions. The final products of decomposition are methane, carbon dioxide, sulfate, nitrogen, hydrogen, the resulting biomass and stabilized organic matter.

Anaerobic decomposition includes several sets of processes that differ from each other in their initial and final decomposition products. The hydrolysis of high-molecular substances, the decomposition of hydrolysis products into organic acids, alcohols, amino acids, carbon dioxide and hydrogen, the decomposition of more complex products of the intermediate process into substrates suitable for methanogenic bacteria and the formation of methane and carbon dioxide take place sequentially.

The most important factors that influence the course of anaerobic decomposition of organic matter include the composition of the substrate (the specific production and composition of biogas also depends on it), the presence of nutrients, pH, buffering capacity and temperature.

For anaerobic digestion to proceed well, the presence of a number of inorganic nutrients is important. The presence of a number of growth factors and vitamins is also important, some of which microorganisms can synthesize, others must be supplied.

The above problem is solved by a method of stimulating biogas production during anaerobic methane fermentation of sludge, wastewater and other organic materials according to the invention. Its essence lies in the fact that a mechanically or physically modified biomass suspension is added as a stimulating agent to the material intended for fermentation or directly to the anaerobic reactor in an amount of 0.1 to 10%, preferably 5%, based on the organic dry matter of the processed material.

According to a preferred embodiment, biomass taken from the reactor in which the actual process takes place or from another well-methanizing reactor in which the actual process takes place or from another well-methanizing reactor is used to prepare the stimulating agent.

It is possible to prepare the stimulating agent by mechanical disruption of the biomass cells or by repeated freezing and thawing of the biomass suspension one to five times at a temperature of -1 to -40°C, preferably -8°C.

It is further preferred to prepare the stimulating agent by heating the biomass suspension for 5 to 60 minutes at a temperature of 80 to 100° C. Finally, it is also possible to prepare the stimulating agent by disrupting the cells of the biomass microorganisms by ultrasound.

The basic advantage of the method according to the invention lies in the increase in biogas production by 10 to 60% compared to the existing method of anaerobic methane fermentation of organic substances, however, the methane content in the biogas is the same or higher than in the process without stimulation.

Simultaneously with the increase in biogas production, the rate of anaerobic decomposition increases. In anaerobic sludge stabilization by the method according to the invention, in addition to the increase in the amount and rate of biogas production, the amount of the obtained product - stabilized sludge - decreases due to deeper decomposition. The obtained stabilized sludge exhibits good drainage properties.

The stimulating effect of the process according to the invention lies in the fact that the cellular content released from the cells of anaerobic microorganisms by their disruption contains a number of growth factors, vitamins and inorganic substances having a stimulating effect on all types of microorganisms participating in the anaerobic stabilization process.

Another advantage of the process according to the invention is that a portion of the excess biomass (sludge) removed from the reactor is used to prepare the cell extract. This reduces the amount of sludge after anaerobic stabilization and makes its further processing cheaper.

Stimulation according to the method does not increase the specific biogas production, which is also not theoretically possible, but it increases the overall depth of decomposition of organic matter and sludge and thus the overall biogas production.

The method according to the invention is further described in more detail with reference to several exemplary embodiments.

Example 1.

Three reactors with a usable volume of 12 l /A, B, C/ were operated under identical conditions with the same amount and type of substrate and inoculum. The substrate was raw sludge from a municipal wastewater treatment plant and the inoculum was well-stabilized sludge from the anaerobic reactor of the treatment plant.

Both sludges /substrate and inoculum/ were homogenized and sieved through a 9 mm mesh sieve before the experiment. Reactor A served as a reference. A stimulating agent prepared by three times freezing and thawing anaerobic biomass was added to reactor B.

A stimulating agent prepared by freezing three times and then heating for 30 minutes at 100 °C was added to reactor C. The experiments were performed once at a temperature

35 °C, constant i silence. Time attempt it's 10 days. Initial and final parameters attempts are listed in the following table A B C amount added substrate /organic dry matter/ g 32.0 32.0 32.0 amount of inoculum /organic dry matter/ g 123.0 123.0 123.0 stimulant /organic dry matter/ g 0 1.3 1.3

concentration of organic dry matter in the reactor

beginning of the experiment /g 1 */ 12.9 13.0 13.0 /mixture volume 12 1/ end of experiment /g 1 / 12 , 16 11.97 11.72 /mixture volume 11.4 T/ removed organic dry matter /g/ 16.1 19.5 22.3 specific biogas production /1 g ^-1 / 0.685 0.720 0.705 total biogas production /1/ 11.03 14.04 15.72 increased biogas production /%/ 24.2 42.5 methane content in biogas /%/ 6 7.0 66.5 67.3

i r i k i a d 2

Semi-continuous experiments on anaerobic stabilization of raw sewage sludge were carried out in two anaerobic reactors with a volume of 12 l. Both reactors were operated under the same conditions; a stimulating agent prepared by heating anaerobic biomass at 100 °C for 30 minutes, taken from the reactor itself as excess sludge, was added to reactor no. 1 together with raw sludge. The second reactor served as a reference.

The reactors were filled with 0.8 kg ^m3 of organic dry matter. A stimulating agent was added to reactor 1 in an amount of 3% relative to the substrate. In a steady state.

with a residence time of 12 days, reactor no. 1 produced 5.4 1 d ^-1 and reactor no. 2 - the reference

4.2 1 d ^-1 of biogas, i.e. the stimulated reactor produced 22% more biogas under the same technological conditions, while the methane content was around 65% in both cases.

Example 3

Experiments to stimulate biogas production were carried out in laboratory models with a volume of 12 l. Raw sludge from the Prague WWTP was used as a substrate and anaerobically stabilized sludge from the anaerobic reactor of the treatment plant was used as an inoculum.

Three reactors were operated under identical conditions. Reactor No. 1 as reference.

A stimulating agent prepared by mechanical disruption of cells was added to reactor No. 2. Disruption was performed on a laboratory homogenizer using glass beads with a diameter of 0.25 mm and mixing for 10 minutes. This treatment increased the COD in the solution by approximately 50%.

A stimulant prepared by ultrasonic disruption was added to reactor No. 3. This treatment increased the COD of the liquid phase by 120%. In both cases, anaerobically stabilized sludge, the same as that used as the inoculum, was used to prepare the stimulant. The stimulant addition in both cases was 5% based on organic dry matter.

The initial and final parameters of the experiments are listed in the table below:

reactor

1 2 3 amount of added substrate /organic dry matter/ /g/ 41.5 41.5 41.5 amount of inoculum /organic dry matter/ /g/ 134.0 134.0 134.0 stimulant /organic dry matter/ /g/ 0 2.0 2.0 concentration of organic solids in the reactor start of the experiment g 1 ¹ 14.6 14.8 14.8 end of attempt gl ^-1 12.95 13.0 12.45 total biogas production /1/ 13.46 15.33 19.2 increase biogas production /*/ - 13.9 42.6

The invention can be applied to all processes of anaerobic stabilization of organic substances, such as anaerobic stabilization of sewage sludge or other organic sludge, anaerobic wastewater treatment, wherever the goal of the process is maximum energy yield, that is, maximum biogas production.

Claims (6)

SUBJECT OF THE INVENTION A method for stimulating biogas production in anaerobic methane fermentation of sludge, effluents and other organic materials, characterized in that a mechanically or physically modified biontase suspension in an amount of 0.1% is added to the material to be fermented or directly to the anaerobic reactor. up to 10%, preferably 5%, based on the organic dry matter of the material to be treated. 2. A process according to claim 1, wherein the stimulating agent is biomass taken from the process reactor or from another methanizing reactor. 3. The method according to claim 1, wherein the biomass is treated by mechanical disruption of the cells. 4. Process according to claims 1 and 2, characterized in that the biomass suspension is treated by repeated freezing and thawing at 1 to 5 times at a temperature of -1 to -40 ° C, preferably -8 ° C. 5. The method of claims 1 and 2, wherein the biomass suspension is treated by heating for 5 to 60 minutes at 80 to 100 ° C. 6. A method according to claim 1, wherein the biomass is treated by ultrasonically destroying the microorganism cells.