Partial ozonation pre-treatment for sludge solubilization and simultaneous degradation of bisphenol A: quantification studies

Abstract

Ozonation pre-treatment was investigated for the enhancement of sludge solids and organic matter solubilization and simultaneous degradation of bisphenol A (BPA), an endocrine disruptor compound from wastewater sludge (WWS). The ultrafast method (15 s per sample) used for the analysis of BPA in WWS is based on Laser Diode Thermal Desorption/Atmospheric Pressure Chemical Ionization coupled to tandem Mass Spectrometry. The statistical methods used for optimization studies comprised the response surface method with fractional factorial designs and central composite designs. The ozonation pre-treatment process was carried out with four independent variables, namely WWS solids concentration (15–35 g l ⁻¹), pH (5–7), ozone dose (5–25 mg g ⁻¹ SS) and ozonation time (10–30 min). It was observed that among all the variables studied, ozone dose had more significantly (probability (p)<0.001) affected the efficiency of the ozonation pre-treatment by increasing sludge solids (suspended solids (SS) and volatile solids) solubilization and organic matter (soluble chemical oxygen demand and soluble organic carbon) increment and BPA degradation from WWS. During the optimization process, it was found that higher BPA degradation (100%) could be obtained with 24 g l ⁻¹ SS, 6.23 pH with an ozone dose of 26.14 mg g ⁻¹ SS for 16.47 min ozonation time. The higher ozone dose used in this study was observed to be cost effective on the basis of solids and organic matter solubilization and degradation of BPA.

Keywords:

• bisphenol A
• ozonation
• solubilization
• surface response methodology
• wastewater sludge

Acknowledgements

The authors are thankful to the Natural Sciences and Engineering Research Council of Canada (Discovery Grant 355254) for financial support. Thanks to the Fonds Québécois de la Recherche sur la Nature et les Technologies (FQRNT), Québec, Natural Sciences and Engineering Research Council of Canada (NSERC) and Phytronix Technologies, Québec for providing a Ph.D. scholarship (BMP Innovation) to D.P. Mohapatra. The views or opinions expressed in this article are those of the authors and should not be construed as opinions of the U.S. EPA.