Destroying the structure of extracellular polymeric substance to improve the dewatering performance of waste activated sludge by ionic liquid.

The disposal and resource utilization of waste activated sludge (WAS) is a big challenge for its high moisture content. Ionic liquid (IL), 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([EMIM][OTf]), was innovatively used as a conditioner to improve the dewatering performance of WAS. The WAS was characterized by flocs size, three-dimensional excitation-emission matrix (3D-EEM), zeta potential, Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscope (SEM) for the investigation of intensification mechanism. The results showed that the dewatering performance of WAS conditioned by [EMIM][OTf] was significantly improved. The moisture content was successfully decreased to 64.99±0.92 %, and the intensification mechanism was investigated. The results showed that the structures of extracellular polymeric substance (EPS) were destroyed by [EMIM][OTf]. It brought a sharp decrease of the contents of polysaccharides (PS), proteins (PN), humic acid (HA) and fulvic acid (FA) in tightly bound extracellular polymeric substance (TB-EPS) structure. The inactivation of microbial cells promoted the disintegration of flocs. Large flocs were converted into unstable small particles and biopolymers. In addition, the negative charges of WAS were also neutralized for dissolution of biopolymers in [EMIM][OTf], and the electrostatic repulsion between flocs was weakened. [EMIM][OTf] was easily recycled five times. The research results indicate that specific IL, such as [EMIM][OTf], is a potential conditioner to improve the dewatering performance of WAS.