Full-scale thermophilic digestion at the west-southwest sewage treatment works, Chicago, Illinois

Abstract

To increase the solids-processing capacity of its largest sewage plant, the Chicago Sanitary District considered converting its mesophilic digestion facility to thermophilic operation rather than expanding the plant. A 130-week performance test demonstrated the energy self-sufficiency of a thermophilic digester operated at a 7-day detention time and thus processing twice as much sludge as the mesophilic unit. Its energy self-sufficiency depends on the feed solids concentration, gas production rate, and heating-plant efficiency.