Lime Stabilization of Wastewater Sludges

The standard lime stabilization process and two process modifications are effective procedures for reducing fecal streptococcus concentrations (disinfection) in wastewater sludges. Depending on the process modification, fecal streptococcus concentrations in treated sludges ranged from a 7-log decrease to a 3-log increase over seven days. Three to seven log reductions are associated with treated sludges meeting the Environmental Protection Agency (EPA) criterion of pH ≥ 12 two hours after lime addition. Poor reductions or substantial increases in fecal streptococcus concentrations are associated with treated sludges which do not meet the EPA criterion. Lime stabilization is particularly suitable for landfilling or agricultural utilization of wastewater sludges, and one of the process modifications can be effectively incorporated into any sludge processing scheme.