Pre-Treatment of Sludges Before Aerobic Digestion to Enhance Sludge Quality

Bench scale experimentation was completed to assess the potential of using a short residence time pre-treatment reactor upstream of aerobic digestion to enhance the destruction of pathogens. The impact of aeration, temperature, hydraulic residence time, solids concentration, feeding frequency and mechanical shearing on the pre-treatment process was investigated. Subsequent testing evaluated the operation of selected pretreatment conditions in a staged configuration with a conventional aerobic digester. Either highly aerobic or highly reducing conditions were observed to be most effective in reducing the concentrations of E. coli. and Salmonella spp. in the pre-treatment reactor. When operated in series with the aerobic digesters, the more highly reducing conditions in pre-treatment were found to enhance die-off of the organisms in the subsequent aerobic digestion.