Evaluation of Stability and Maturity Parameters in Wastewater Sludge Composting with Different Aeration Strategies and a Mixture of Green Plant Wastes as Bulking Agent

Abstract

The aim of this study was to investigate the influence of bulking agent volumetric ratio on the stability and maturity parameters in composting process of anaerobically digested sludge (ADS) with different aeration strategies. Two main influencing factors including aeration method (aerated static pile and windrow process) and proportion of green plant wastes (GPW) and ADS (1:1,2:1 and 3:1, GPW: ADS) were investigated through the evaluation of physicochemical and biological parameters during the 83 days of composting. Heavy metals concentration, germination index (GI), and microbiological indicators were also determined in the final products. The results showed that windrow method was superior to the aerated static piles, since the former enhances the composting process by favoring organic matter (OM) stabilization. Based on these results it appears that windrow method with 2:1 mixture of GPW: ADS was best for ADS composting due to the highest OM degradation ability and maximum GI in the final product.