Variability by the assessment of bromate formation in wastewater treatment

The ecological toxicity of micropollutants is becoming increasingly problematic, with wastewater treatment plants occupying a pivotal position in the mitigation thereof. However, wastewater treatment plants are not primarily designed to eliminate micropollutants, necessitating the use of advanced treatment technologies such as ozonation. Although ozonation is an effective method for the removal of micropollutants, it can also result in the formation of potentially harmful transformation products, such as bromate. The lack of standardization in batch ozonation experiments, which are often used to assess ozone demand, has resulted in inconsistent bromate formation results between laboratory tests and real-scale operations. This study addresses the variability in bromate formation across laboratory tests, with the support of CFD simulations of the experimental setup, in comparison to full-scale applications. Consequently, bromate formation was investigated in both a conventional ozonation plant and with an innovative ozone injection mechanism, namely ozone strong water (OSW) dosing, which was installed at the wastewater treatment plant in Duisburg-Vierlinden, Germany. These observations were then compared to those made at the laboratory scale. The results demonstrated that bromate levels reached up to seven times the target level in laboratory tests (10 μg/L), whereas full-scale operations exhibited significantly lower or no bromate formation. The application of the OSW technology resulted in an additional reduction in bromate formation compared to the standard ozonation process. • Laboratory results overestimate bromate risks compared to full-scale ozonation performance. • Ozone hotspots during injection correlate with higher bromate formation. • Injection speed and local mixing are key factors influencing bromate formation in ozonation. • CFD simulations reveal key factors influencing bromate formation and hotspots. • OSW-system provides effective bromate control for advanced treatment scenarios.