anaerobic biological treatment is an anaerobic condition, which forms the nutritional and environmental conditions required by anaerobic microorganisms, and uses these microbes to decompose organic compounds in the wastewater and produce methane and carbon dioxide.
the anaerobic degradation process of polymer organic compounds can be divided into four stages: hydrolysis, fermentation (or acidification), acetic acid production and methanogenesis.
(1) hydrolysis in the hydrolysis stage can be defined as the conversion of complex insoluble polymers into simple soluble monomers or dimers.
(2) fermentation (or acidification) stage fermentation can be defined as the biodegradation process of organic compounds both as electron acceptors and electronic donors, in which dissolved organic compounds are converted to volatile fatty acids as the main end products, so this process is also called acidification.
(3) the production of acetic acid, hydrogen, carbonic acid and new cell substances was further transformed into acetic acid producing acetic acid at the stage of acetic acid production.
(4) during the methane stage, acetic acid, hydrogen, carbonate, formic acid and methanol are converted into methane, carbon dioxide and new cellular materials.
the reaction in acidification pond is a part of anaerobic reaction.
an anaerobic pond is a reaction cell without dissolved oxygen or nitrate. anoxic pool is a reaction pool without dissolved oxygen but with nitrate.
acidification pond hydrolysis, acidification, acetic acid production, limiting methanation, with ph reduction. the process is simple and easy to control. it can remove part of cod. objective to improve the biodegradability.
anaerobic pond - hydrolysis, acidification, acetic acid production and methanation. it is necessary to adjust ph, not easy to operate and control, and remove most cod. the aim is to remove cod.
the anoxic pool has hydrolysis reaction, and its ph value increases in the process of denitrification. in the process of denitrification, denitrification plays an important role in removing nitrate nitrogen, while removing part of bod. there is also a hydrolysis reaction that improves the biodegradability.
there can be no aeration device inside the hydrolysis acidification pool to control the retention time in the stage of hydrolysis and acidification without anaerobic biogas production stage. the removal rate of cod in the first two stages is not very high, because his purpose is to turn large molecules into small molecules, with a general removal rate of about 20%, and a general removal rate of cod at the gas production stage. at about 40%, but this is the production of hydrogen sulfide gas to deodorizing treatment, and to reach the gas stage of the residence time is longer than the previous two stages, that is, the emergence of anaerobic state. the aeration device should be set up in the anoxic pool to control the dissolved oxygen in 0.3-0.8mg/l, to degrade the organic matter in the wastewater by the use of facultative microorganism and biofilm. the aerator in the oxidation tank should be carefully chosen, not only to ensure the oxygen supply, but also to ensure the loss of the biofilm and to be more new. generally, the microporous aerator is not used as the bottom aerator.
aerobic pool is to maintain the dissolved oxygen content in the water around 4mg/l by means of aeration and so on. it is suitable for the growth and reproduction of aerobic microorganisms, so as to deal with the structures of the pollutants in the water.
anaerobic pool is not aeration, the concentration of pollutants is high, because the decomposition and consumption of dissolved oxygen makes water in the water almost no dissolved oxygen, suitable for anaerobic microbial activities to deal with the structure of pollutants in the water;
the anoxic pond is a structure that is suitable for aerobic and facultative microorganisms living under low aeration or without aeration.
different oxygen environments have different microbial communities, microorganisms will change their behavior when the environment changes, so as to achieve the purpose of removing different pollutants.
the function of aerobic tank is to allow aerobic respiration of activated sludge and further decompose organic matter into inorganic matter. remove the function of the contaminant. to run well is to control the oxygen content and other microbial requirements of the best, so that microorganisms have the greatest benefit of aerobic respiration.
anaerobic treatment usually takes a long time to remove organic matter from wastewater by anaerobic bacteria. anaerobic processes can be divided into hydrolysis stage, acidification stage and methanation stage.
the product of hydrolytic acidification is mainly small molecule organic matter, which makes the dissolved organic matter in the wastewater increase significantly, and the microorganism can enter the cell directly only with the small molecules of dissolved organic matter, and the insoluble macromolecule is first to be metabolized in the microorganism through the decomposition of the extracellular enzyme. for example, natural gelation agents (mainly starch) are first converted to polysaccharides and then hydrolyzed into monosaccharides. cellulose is hydrolyzed by cellulase to form two sugar and glucose. hemicellulose was hydrolyzed into xylose and oligosaccharides by xylanase.
the hydrolysis process is slow, and is affected by many factors at the same time, which is the speed limit of anaerobic degradation. at this stage of acidification, the small molecular compounds formed in the first stage are converted into simpler compounds in the cells of fermented bacteria, the acidified bacteria, and secreted to the bacteria in vitro, mainly including volatile organic acids (vfa), lactools, alcohols, and then further converted to acetic acid, hydrogen and carbonic acid. acidification is accomplished by a large number of fermenting bacteria and acetogenic bacteria, most of them are strictly anaerobic bacteria, which can decompose sugar, amino acids and organic acids.
source: arctic water treatment network
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