title: Influence of seasonal fluctuation and loading rates on microbial and chemical indicators during semi-continuous anaerobic digestion.
abstract: Minimal attention is paid towards the performance of the 40 million small-scale digesters which frequently operate at psychrophilic temperatures. Understanding the levels of microbial and chemical indicators at various loading rates and temperatures is useful for improving treatment efficiency and management strategies for small-scale digesters. In this study, semi-continuous anaerobic digesters were operated in replicate at four different loading rates (control, 0.3, 0.8 and 1.3 kg VS/m(3)/day) and housed in an environment that simulated seasonal change (27.5°C,10°C and 27.5°C). The results illustrate that class B quality biosolids were generated for all treatments as per guidelines from the United States Environmental Protection Agency (USEPA). The simulated seasonal change did not influence Escherichia coli or faecal coliform levels, while it did appear to have an effect upon levels of Enterococci. Reduced loading rates led to a more stable environment (in terms of pH, levels of volatile fatty acids (VFAs) and total inorganic carbonate (TIC)) as well as lower levels of indicator bacteria, but generated slightly lower biogas volumes (high--53.23 L vs. low--53.19 L) over the course of the study. The results provide important data to improve the performance of small-scale psychrophilic digesters, specifically by reducing loading rates to prevent souring during winter months.
authors.affiliation: a Division of Environmental Health Sciences, College of Public Health , The Ohio State University , 406 Cunz Hall, 1841 Neil Avenue, Columbus , OH 43210-1057 , USA.
authors.forename: James
authors.initials: J
authors.lastname: Rosenblum
authors.forename: Michael
authors.initials: M
authors.lastname: Bisesi
authors.forename: Juan
authors.initials: J
authors.lastname: Castano
authors.forename: Abigal
authors.initials: A
authors.lastname: Tamkin
authors.forename: Richard
authors.initials: R
authors.lastname: Ciotola
authors.forename: Jiyoung
authors.initials: J
authors.lastname: Lee
authors.forename: Jay
authors.initials: J
authors.lastname: Martin
mesh_terms: D000693:Anaerobiosis; D056804:Biofuels / Q000032:analysis; D019149:Bioreactors; D004203:Disinfection; D016983:Enterococcus; D004926:Escherichia coli; D006863:Hydrogen-Ion Concentration; D012621:Seasons; D013696:Temperature
chemical_list: D056804:Biofuels
keywords: anaerobic digestion; biosolids; faecal indicators; psychrophilic; waste management