Chemical Engineering Science, Vol.81, 20-27, 2012
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 center dot 7H(2)O 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 mu g 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. (C) 2012 Elsevier Ltd. All rights reserved.