Integrated Waste Management Combining Anaerobic and Aerobic Treatment: A Case Study

Abstract

The aim of this work was to study the feasibility of composting, as a post-treatment option, to manage the solid fraction of anaerobically digested pig slurry (SFP) produced in an industrial waste treatment plant, together with other wastes processed in the facility (sewage sludge (SS), paper mill sludge (PS) and pig hair waste (PW), and two bulking agents [maize straw (MS) and wheat straw (WS)]. Six composting mixtures were prepared (percentage on fresh weight basis): P1 (100 % SFP), P2 (80 % SFP + 20 % MS), P3 (60 % SFP + 40 % MS), P4 (35 % SFP + 35 % SS + 30 % mixture of MS and WS), P5 (35 % SFP + 35 % PS + 30 % mixture of MS and WS) and P6 (35 % SFP + 35 % PW + 30 % mixture of MS and WS). Throughout the composting process, temperature evolution was monitored and physico-chemical and chemical parameters were determined. Furthermore, the evolution of the microbial community structure was assessed by the real time PCR technique. The use of the bulking agents influenced positively the composting development, especially in the mixtures P2 and P5. In general, all the composts showed a good degree of maturity and absence of phytotoxicity, but the use and proportions of determined raw materials (PS, SS and SFP) produced composts with several limiting aspects (high salinity and/or notable contents in Cu and Zn) for their agricultural use. The increase of the ratio fungi/eubacteria by the end of the process was consistent with the maturity of the produced compost and the good performance of the process.