The Use of a Respirometric Technique for Assessing the Evolution of the Stability of a Sewage Sludge Compost Developed under Full-Scale Conditions

Composting is one of the best ways to properly manage the high production of sewage sludge with the aim of obtaining sanitized products with a stable organic matter. The evolution of the stability of a compost consisting of sewage sludge, straw and sawdust, developed under full-scale conditions, was analyzed. The stability was assessed by a respirometric assay performed for 30 days, where the O2 consumption and CO2 production was continuously measured by an automatic respirometer. Important reductions were observed in the respirometric parameters, changes which mainly occurred in the samples taken during the first 40-50 days of composting. After this period, the few changes observed and the low levels of respiration suggested compost stability. The maximum rates and the cumulative values of CO2 and O2 after 8 days of incubation seemed to be the most useful respirometric parameters for compost monitoring. _____________________________________________________________________________________________________________