Mechanistic insights into promoted dewaterability, drying behaviors and methane-producing potential of waste activated sludge by Fe2+-activated persulfate oxidation. (15th November 2021) - Tan, Yujie
Abstract: Sludge management represents a critical challenge because of complex compositions and poor dewaterability. Fe 2+ -activated persulfate oxidation (Fe 2+ /S2 O8 2− ) is an effective, and widely investigated method for enhancing sludge dewatering. However, the potential effects of Fe 2+ /S2 O8 2− on sludge drying efficiency, anaerobic biodegradation behaviors and potential recycling of sludge residua are not yet well-known. In this study, a new sludge disposal route (step i: enhanced dewatering via Fe 2+ /S2 O8 2−, and step ii: drying-incineration or anaerobic digestion) was proposed and appraised comprehensively. Results showed that Fe 2+ /S2 O8 2− oxidation destroyed extracellular polymeric substances, lysed sludge cells and enhanced the dewaterability greatly. Capillary suction time and mechanical filtration time at 2.0/1.6 mmol-Fe 2+ /S2 O8 2− /g-VS decreased by 88.0% and 79.6%, respectively. Moreover, 89.8% of micro-pollutants (e.g., methylbenzene, ethylbenzene, p -m-xylene and o -xylene) in sludge were removed. Besides, the pretreatment was able to alter sludge drying behaviors and methane-producing potential. Pretreated sludge exhibited faster drying rate and shorter lag-time for methane production. Incineration residua of dewatered sludge could be re-coupled with S2 O8 2− as the conditioner to enhance sludge dewaterability, thereby reducing the chemical input and disposal cost. This study provides a novel, self-sustainable strategy for sludge management, reutilization and final safe disposal. Highlights: A comprehensive sludge treatment route was proposed. The capillary suction time of sludge was reduced by 87.9% within 1 min. Fe 2+ /S2 O8 2− pretreatment efficiently removed micro-pollutants. Fe 2+ /S2 O8 2− pretreatment reduced mechanical filtration and drying time. Sludge ash can replace Fe 2+ to activate S2 O8 2− for improving sludge dewaterability.