Online monitoring of bromate in treated wastewater: implications for potable water reuse

Abstract

Continuous monitoring of bromate ions, a disinfection by-product of the ozonation of wastewater, may improve the safety of recycled water for potable use. A recently developed elemental analyzer can determine bromate ion concentrations online. However, dissolved organics present in wastewater interfere with the detection of bromate ions. The aim of this study was to develop a nanofiltration (NF) membrane-based pre-treatment system to remove the interfering substances present in treated wastewater prior to the online analysis. The NF pre-treatment system was optimized to ensure the removal of the interfering substances from the membrane bioreactor (MBR)-treated wastewater without altering the bromate ion concentration. We determined a permeate flux of 1 L m⁻² h⁻¹ and a feed temperature of 35 °C as optimal pre-treatment conditions for online analysis. Furthermore, the continuous monitoring of MBR-treated wastewater, containing different bromate ion concentrations (0–12 μg L⁻¹), for three days revealed a strong correlation between the concentrations determined using the online analyzer and liquid chromatography coupled with tandem mass spectrometry. Thus, this study demonstrates the potential utility of the online bromate ion analyzer coupled with NF pre-treatment system to monitor the rate of bromate ion formation during ozonation.