The objective of this study was to analyze the pH curves of three representative soils of the Metropolitan Region of Curitiba for determining the maximum annual application rates of sewage sludge sanitized by prolonged alkaline stabilization process (EAP sludge), as stated in the legislation, and for comparison with the methodology of base saturation (V%). The soils were incubated with six doses of sludge EAP (pH 9.2) and pH measured on 5 dates, up to 75 days. The Inceptisol from Piraquara with the cation exchange capacity and higher carbon content reached the pH 7 with 49 t ha-1 of total solids (ST); the Oxisol with 38 t ha-1 of ST, and to Inceptisol from Pinhais, the most restrictive, indicated that the annual application of sludge EAP shall not exceed the 31 t ha-1 of ST. Caution in selecting representative soil was suggested. The method V% recommended EAP sludge quantities equal or slightly higher than that reached pH 6 by the method of incubation.
Resolution CONAMA 375/2006; incubation; biosolids; agricultural use of sewage sludge
