Microwave treatment of sewage sludge (Bosnia and Herzegovina)

This research explored the efficiency and effectiveness of a pilot-scale microwave technology in treating sludge from the wastewater treatment plant in Mostar city in Bosnia and Herzegovina, and analysed the potential for reuse of the treated sludge as a fertiliser or biofuel. During the study, sludge was obtained from three sludge storage areas with different storage times. The sludge thickness was varied as 2 cm, 5 cm and 9 cm while maintaining the same mass of 0.8 kg to evaluate how this would affect the sludge drying rate, moisture content, and pathogen concentration change over time. The sludge was dried to 85% total solids (TS) and analysed to assess its potential for reuse, including microbiological tests (E. coli), total nitrogen (TN), total phosphorous (TP) and calorific values. The microwave treatment unit achieved a 60% sludge volume reduction and minimal COD, TN, TP and VS reductions. The dried sludge had adequate nutrient concentrations to be used as fertiliser and had calorific values adequate for combustion. The E. coli removal efficiency was not tested as the concentrations in the sludge before microwave exposure were undetectable.