Sewage sludge pretreatment: current status and future prospects.

Sewage sludge is regarded by wastewater treatment plants as problematic, from a financial and managerial point of view. Thus, a variety of disposal routes are used, but the most popular is methane fermentation. The proportion of macromolecular compounds in sewage sludges varies, and substrates treated in methane fermentation provide different amounts of biogas with various quality and quantity. Depending on the equipment and financial capabilities for methane fermentation, different methods of sewage sludge pretreatment are available. This review presents the challenges associated with the recalcitrant structure of sewage sludge and the presence of process inhibitors. We also examined the diverse methods of sewage sludge pretreatment that increase methane yield. Moreover, in the field of biological sewage sludge treatment, three future study propositions are proposed: improved pretreatment of sewage sludge using biological methods, assess the changes in microbial consortia caused with pretreatment methods, and verification of microbial impact on biomass degradation.

Influence of the autochthonous cellulolytic bacteria on the domestic compost process improvement.

This work aimed to determine the influence of the inoculation of autochthonous cellulolytic bacteria on the composting process without any modifications of physical or chemical parameters. Bacteria with cellulolytic abilities were isolated from composted material containing food and plant leftovers and identified as Bacillus licheniformis, Bacillus altitudinis, and Lysinibacillus xylanilyticus. The experimental composter containing garden and household wastes was inoculated with bio-vaccine prepared as a mixture of isolated cellulolytic bacterial strains and composted for the next 96 days parallelly to the control composter without the inoculation. During the experiment, changes in temperature, humidity, the content of the humic acids (HAs), organic carbon, nitrogen, and C : N ratio were determined. As the particular microbial groups play a key role in the composting process, the biodiversity of the microorganisms present in the composter as well as the number of psychrophilic, mesophilic, and sporeforming microorganisms, Actinomycetes, and fungi were analyzed. The changes in the abundance of particular bacterial groups were convergent with temperature changes in the temperature of composting material. The composting material inoculated with autochthonous microorganisms was characterized by higher HA content and lower biodiversity. The inoculation with autochthonous microorganisms positively influenced the composting material in the corners for the entire process and in the middle of the container for 61 days. Thus, the effect of inoculation depended on the localization of the process inside the container subjected to biopreparation.