Digested Sludge Disposal on Crop Land

After exhaustive study to determine the best solids disposal solution, The Metropolitan Sanitary District of Greater Chicago concluded that digestion followed by land disposal could cope with Chicago's 1,000 tons (907,000 kg)/day of sludge successfully at a cost of $20 to $23/ton ($0.022 to $0.025/kg). Research designed to determine groundwater contamination, the effect of heavy metals, and crop irrigation parameters was conducted by the University of Illinois and the District. Kenaf and corn were used as the experimental vegetables. An 8-acre (3.2-ha) and a 30-acre (12.2-ha) plot were used for the tests. Crops responded favorably to digested sludge, odors and flies were not problems, and nitrate rates in drainage waters increased.