Ferro-sonication and partial ozonation pre-treatment and biotransformation of wastewater sludge for degradation of bisphenol A: Rheology studies

The effect of physico-chemical pre-treatment processes, including ferro-sonication (FS) and partial ozonation (OZ) on the rheology of wastewater sludge (WWS) was investigated. The ferro-sonication and partial ozonation pre-treatment was carried out at optimum conditions: 163 min ultrasonication time, 2.71 mg L−1 FeSO4·7H2O with pH 2.81 and 26.16 mg g−1 SS ozone dose, 16.47 min ozonation time at pH 6.23, respectively. Raw and pre-treated sludge depicted non-Newtonian and pseudoplastic behavior with 85%–97% confidence of fit into Bingham, Casson, Power and IPC paste models for solids concentration ranging from 15 g L−1 to 35 g L−1. Among all the rheological models studied, the power law was more prominent (confidence of fit 90% to 97%) in describing the rheology of the raw and pre-treated sludge. Pre-treatment of WWS led to decrease in pseudoplasticity due to decrease in consistency index K and increase in flow behavior index n. Further, the effects of FS and OZ pre-treatment of WWS on particle size change and on the degradation of bisphenol A (BPA), an endocrine disruptor were also investigated. The results showed a decrease in viscosity and particle size together with a higher degradation of BPA from WWS. BPA degradation by laccases produced by Sinorhizobium meliloti in raw and pre-treated sludge was also determined. Higher activity of laccase (366 U L−1) was observed in partially ozonated sludge, resulting in higher removal of BPA (0.16 μg g−1) from WWS. The findings presented in this manuscript are potentially interesting to researcher studying the behavior of sewage sludge in wastewater treatment and removal of trace organic contaminants.

Hightlights
► Power law was more prominent to depict non-Newtonian and pseudoplastic behavior of sludge.
► Pre-treatment of sludge led to decrease in consistency index K and increase in flow behavior index n.
► Decrease in viscosity and particle size during pre-treatment led to higher degradation of bisphenol A.
► Laccase produced by Sinorhizobium meliloti capable of degrading bisphenol A from sludge.
► Higher activity of laccase resulting higher degradation of bisphenol A from sludge.