Effect of anaerobic digestionand lime stabilization on sewage sludge carbon and nitrogen mineralization

Abstract

This work aims to evaluate the N and C mineralization in a Haplic Arenosol amended with 3 different sewage sludge: mixture of primary and secondary sewage sludge (MSS), anaerobically digested sewage sludge (DSS) and anaerobically digested sewage sludge treated with quicklime (LimeDSS). Two aerobic incubations, one to follow N mineralization and the other one to assess CO₂ emissions, were performed during 140 days. MSS promoted soil N immobilization during the first days of incubation and higher CO₂ emissions (46% of the applied C was lost), consequence of a high content of non-stabilized organic matter. In DSS there was nitrogen net mineralization but only 17% of the applied carbon was mineralized, showing that anaerobic digestion stabilized the sludge organic matter. Sewage sludge treatment with quicklime reduced its NH₄⁺ content, but enhanced carbon (40%) and nitrogen (39.2%) mineralization after soil application. Anaerobic digested sewage sludge (DSS) seems to be the most interesting treatment, since it ensured a high level of available N to plants and a great contribution to C sequestration in soil.