Evaluation of Dewatering Devices for Producing High-Solids Sludge Cake

摘要

Pilot-plant dewatering tests were made to establish design and operating parameters for dewatering municipal wastewater sludges on recessed plate filter presses (both diaphragm and fixed volume types), continuous belt presses, and retrofit units for a vacuum filter. Results from the 1.5-year study showed that when dewatering lime and ferric chloride-conditioned sludges, the recessed plate presses consistently produced a 30-40% solids filter cake. Feed solids to the units averaged 5% total solids with a range from 2.4 to 10%. Various ratios of waste-activated to primary sludge solids, with emphasis on the 2/1 ratio, were tested. Belt presses produced cake solids from 25-30% when the polymer conditioning dosage was optimized. When used as a retrofit device to a vacuum filter, the belt press gave cake solids in the 30-40% range during laboratory-scale tests. Design parameters are developed to dewater a mixture of 67% secondary and 33% primary sludge in a full-scale plant installation. The estimated costs for dewatering plus final disposal by either incineration or composting are also presented.