Enhanced dewatering of activated sludge by acid assisted Heat–CaO2 treatment: Simultaneously removing heavy metals and mitigating antibiotic resistance genes

Abstract High water content and accumulation of heavy metals and antibiotic resistance genes (ARGs) in sewage sludge limit its application. Fenton process has been widely used in sludge dewatering, but the use of hydrogen peroxide (H2O2) and generation of acid sludge are the main drawbacks. Here, a novel method of heat-CaO2 treatment was proposed to enhance sludge dewatering. Results showed that CaO2 (12.5 mg/g dry solids (DS)) combined with heat at 60 °C significantly improved the sludge dewaterability, e.g. the water content decreased from 79.9% to 69.2% and the specific resistance to filtration (SRF) decreased from 9.21 × 1013 to 1.51 × 1013 m/kg. At 62.5 mg CaO2/g DS, the final pH of filtrate was close to neutral and the good dewatering performance was still achieved. The improvement of sludge dewaterability was closely correlated with the decomposition of tightly-bound extracellular polymeric substances (EPS), lysis of the sludge cells, and increased particle size of the flocs. The distribution of bacterial community in the sludge has changed, leading to the decreases in the percentage of some ARGs. The concentrations of typical heavy metals wrapped in the sludge colloid network dramatically reduced. Economic analyses showed that the heat-CaO2 treatment was a promising method for sludge disposal.