Role of extracellular polymeric substances in enhancement of phosphorus release from waste activated sludge by rhamnolipid addition

• RL pretreatment was successfully developed to enhance P release from WAS.
• The cumulative PO43−–P was better fitted with pseudo-first-order kinetic model.
• This was the first time to explore the role of EPSs in P-release from WAS.
• Changes of metal elements, P fractions and species in EPSs had been investigated.
• Release contributions of P from EPSs/(cells + others) to liquid had been identified.

This study investigated the role of extracellular polymeric substances (EPSs) in enhanced performance of phosphorus (P) release from waste activated sludge (WAS) by adding rhamnolipid (RL). Results showed that compared to WAS without pretreatment, the released PO43−–P increased with RL addition from 0 to 0.2 g/g TSS (total suspended solid), and increased by 208% under the optimal condition (0.1 g RL/g TSS and 72-h fermentation time). The cumulative PO43−–P was better fitted with pseudo-first-order kinetic model. Moreover, the contents of metal ions increased in liquid but decreased in EPSs linearly with RL addition increasing, and WAS solubilizations were positively correlated with the released metal ions. The enhanced total dissolved P mainly came from cells and others (69.39%, 2.27-fold higher than that from EPSs), and PO43−–P was the main species in both liquid and loosely bound EPSs, but organic P should be non-negligible in tightly bound EPSs.

Figure optionsDownload as PowerPoint slide