Microbiology of the decomposition of fibrous wastes

The literature of anaerobic sludge digestion and methane fermentation was reviewed;Observations were made on the quantity and quality of gas evolved, reaction (pH), microscopic examinations, and aerobic and anaerobic bacterial counts of samples of sewage solids digested at 28--30°C and at 50--55°C;Bacterial isolations were made at intervals during the course of the fermentation of the samples of sewage solids;Methane was not produced in sewage solids stored at 28--30°C or 50--55°C without adjustment of reaction, which remained very acid, approximately pH 5.0;The optimum reaction for methane development was pH 7.0--7.4 at both 28--30°C and 50--55°C;The bacterial counts did not correlate with active methane fermentation;A large proportion of the micro-organisms, from the anaerobic fermenting sewage solids, growing on various standard media were facultative forms;Fat splitting, proteolytic, and gelatin liquefying micro-organisms were found to be more prevalent in the earlier stages of fermentation than the later stages;Hydrogen sulphide producing micro-organisms were very prevalent during the entire period of fermentation;Higher bacterial counts were obtained with Bacto peptone iron agar than with nutritive caseinate agar, Frazier\u27s gelatin agar, or meat infusion---cottonseed oil---nile blue sulphate agar;Microscopic examinations were helpful in observing the changes in the types of prevalent micro-organisms during the course of fermentation and some forms which have been described in the literature as associated with methane fermentation were observed. Peculiar egg-shape rods, which might be associated with methane fermentation, were also observed;Thermophilic methane producers are probably not acclimatized mesophilic forms;Some of the mesophilic facultative bacterial species isolated from the fermenting mixtures of sewage solids were Bacillus subtilis, Bacillus prausnitzii, Micrococcus sphaeroides, Achromobacter liquefaciens and Serratia corollina. Two thermophilic facultative species were identified as Bacillus cylindricus and Bacillus thermocellulolyticus