Chalcopyrite-activated sodium percarbonate oxidation for sludge dewaterability enhancement: Synergetic roles of •OH and 1O2

Efficient dewatering of sewage sludge is an energy-and carbon-saving procedure of sludge treatment in wastewater treatment facilities. Due to the limiting factors of hydrophilic extracellular polymeric substances, it is crucial to weaken the water-holding capacity and hydrophilicity for high-performance sludge-water separation. The current study successfully put forward a combination process of chalcopyrite + sodium percarbonate (SPC) to proficiently facilitate sludge dewaterability. Results showed that after the optimized treatment, the water removal efficiency augmented from 51.3 to 94.9%, while the water content of sludge cake declined from 90.1 to 52.0 wt%. Mechanism investigation demonstrated that the chalcopyrite + SPC system could consecutively generate reactive oxygen species via strong Fe3+/Fe2+ and Cu2+/Cu+ conversion cycles. The dominant reactive radical center dot OH and non-radical 1O2 could effectively degrade the macromolecular EPS into low-molecular bio-polymers, decrease the high-polarity hydrophilic protein secondary structure and amino acids, and further reduce water-holding interfacial affinity. Afterward, the electrostatic force and interfacial free energy were decreased and turned out to enhance self-flocculation and flowability. Accordingly, bound water reduction and sludge-water separation efficiency were promoted. Furthermore, the chalcopyrite + SPC system could be viewed as a surrogate to Fenton/Fenton-like strategies for sludge dewaterability with economic advantage and low environmental risk. These findings inspire the application prospect of the chalcopyrite + SPC conditioning technique, which expects to save energy and reduce carbon emissions.

Automated summary

Efficient dewatering of sewage sludge is achieved using the combination process of chalcopyrite and sodium percarbonate (SPC). This process effectively weakens the water-holding capacity and hydrophilicity of sludge, leading to improved sludge-water separation. The chalcopyrite + SPC system generates reactive oxygen species that degrade the macromolecular extracellular polymeric substances (EPS), reduce water-holding affinity, and enhance self-flocculation and flowability. This system can be considered as an economically advantageous and environmentally friendly alternative to Fenton/Fenton-like strategies for sludge dewaterability.