Enhanced Recovery of Alginate-like Extracellular Polymers (ALE) from Waste-Activated Sludge Using Sodium Percarbonate: Performance and Characteristics

Resource recovery from waste-activated sludge is of great practical significance to achieve sustainable wastewater treatment. Alginate-like extracellular polymers (ALE), a typical class of extracellular polymer substances, are valuable bio-based products with broad application prospects. However, due to the low extraction efficiency of the current method, its practical applications are severely limited. In this study, sodium percarbonate (SPC) was first applied to enhance ALE extraction from conventional activated sludge to replace the sodium carbonate (SC) in the heating-SC method. The results showed that the ALE extracted by the heating-SPC method increased by 30.11% compared to the heating-SC method, and the alginate equivalent was slightly improved. Monosaccharide composition analysis showed that the ALE primarily comprised galactose and glucose, indicating the potential for biomedical applications. The particle size distribution and extracellular polymeric substances (EPS) composition of the sludge indicated that SPC could improve the cracking of the sludge flocs and the organic release. In addition, due to SPC’s ability to oxidize, the molecular composition of the ALE extract changed. In conclusion, SPC used as a substitute for SC in the heating-SC method could be effectively employed to recover ALE from waste-activated sludge. In future studies, further optimization of the operational conditions needs to be considered.