Formation Of Biofilm For The Anaerobic Microbe Carrier And Its Effect On Digestion

The improvement of reaction efficiency is the key to methane's production on industrializationscale. However, anaerobic digestion is a complicated biochemical process. Of all the microbesengaging in the reaction, the species and density of methanogen are the most important influencingfactors for the efficiency of anaerobic digestion and methane yield. Thus the optimization of thespecies of methanogen, the density of methanogen in the reactor and the high intensity of microbesin the reactor are key affecting factors. Extra cellular polysaccharides (ECP) secreted by anaerobicmicrobes, especially methanogens, adhere to carriers and form biofilm by the means that highdensity of microbes and high efficiency of biogas production can be achieved.In the research, tow-step fermentation method is simulated according to the industrializationcraft of methane production. The experimental device and carrier frame are independentlydesigned and packaged. Four reactors are individually packed with 10%, 7.5%, 5% and 0%activated carbon fibre as carrier. At the same condition the cattle manure is put in the reactors inbatch mode for the one experiment',while for the other it is semi-continuously put in reactor. Theconclusions of the research are as follows:1,When material being input and output by batch method without mixing, the methane yieldand COD removing rate can be improved by adding acitvated carbon fibre.But it doesn't showthe superiority in increasing volume gas production rate of reactors, when material input andoutput semi-continuous and mixed twice a day, both of the methane yield and COD removeingrate and volume gas production rate of reactors can be improved by adding acitvated carbonfibre.2,The experimental condition is controlled, the methane yield and COD removeing rate is thehighest in the reactor with 7.5% carrier, the reactor with 5% carrier is second. However, theoverloaded carrier in the reactor with 10% carrier causes lower fermentation efficiency than thecontrol group. As for the phenomenon we can see carriers can increase the intensity of microbeand affect volume utilization ratio. It is necessary to define suitable carrier space factor.3,With different carrier filling factors, the volume load will have different influence on the system. The research results indicated that in the reactor with 7.5％carrier filling factor, whenthe amount of material supplied is 3.2L/d,the capacity aerogenesis rate will be the maximum1.15L/L·d and the COD removing rate rises by 47.38％.It shows the good anti-impact loadperformance.4,With the help of scanning electron microscopy (SEM), the carrier in different periods isobserved, biofilm quantity on the surface of carbon fibre increases continually along with thedigestion time.It almost covers the whole carrier. Besides, it has permeated into the carbonfibre.The high quantity and the diversity of microbes can be compared with sludge pellet.Between the carbon fibre and the biofilm many cracks exist,which is favorable to the attachingand fixed planting of anaerobic microorganism. It also drives microorganism contact substance,which will promote the decomposition and the speed of methane production. Many kinds ofcoccuses and bacillus are set in the cracks of like-coral-reef biofilm. The main bacteria coloniesin the biofilm are methanosaeta and methanosarcina. According to the literature, sarcina is oneof the methanogen that can produce methane in high performance. The remaining of sarcina willapparently improve methane production.