Options and limitations for bromate control during ozonation of wastewater

Abstract

Wastewater treatment plants (WWTPs) are important point sources for micropollutants, which are harmful to freshwater organisms. Ozonation of wastewater is a powerful option to abate micropollutants, but may result in the formation of the potentially toxic oxidation by-product bromate in bromide-containing wastewaters. This study investigates options to reduce bromate formation during wastewater ozonation by (i) reducing the bromide concentration of the wastewater, (ii) lowering the ozone dose during wastewater treatment and (iii) adding hydrogen peroxide to limit the lifetime of ozone and quench the intermediates of the bromate formation pathway. Two examples demonstrate that a high share of bromide in wastewater can originate from single point sources (e.g., municipal waste incinerators or landfills). The identification of major point sources requires laborious sampling campaigns, but may facilitate the reduction of the bromide load significantly. To reduce the bromate formation by lowering the ozone dose interferes with the aim to abate micropollutants. Therefore, an additional treatment is necessary to ensure the elimination of micropollutants. Experiments at a pilot-plant illustrate that a combined treatment (ozone/powdered activated carbon) allows to eliminate micropollutants with low bromate yields. Furthermore, the addition of hydrogen peroxide was investigated at bench-scale. The bromate yields could be reduced by ∼50% and 65% for a hydrogen peroxide dose of 5 and 10 mg L, respectively. In conclusion, there are options to reduce the bromate formation during wastewater ozonation, however, they are not simple with sometimes limited efficiency.

Persistent contaminants of emerging concern in ozone‐biofiltration systems: Analysis from multiple studies

“…A bench-scale study showed that an O 3 :TOC ratio > 0.9 could lead to increased bromate concentration in ozonated effluent (Trussell et al, 2016); thus, the investigators concluded that there should be a balance between oxidation of trace organic compounds and bromate formation. Common bromate control strategies include bromide quenching (specifically the oxidized form, HOBr) using the chloramine-ammonia process or peroxide addition and pH adjustment (Soltermann et al, 2017). Figure 3a shows increasing bromate concentration with an increasing O 3 :DOC ratio in a systematic full-scale study (project I).…”

Controlling disinfection byproducts from treated wastewater using adsorption with granular activated carbon: Impact of pre-ozonation and pre-chlorination

“…Bromate mitigation strategies (e.g., pH depression, ammonia, chloramines, and hydrogen peroxide) involving bromide sequestration or manipulating the ozone/hydroxyl radical pathways have been studied for decades in drinking water applications ( Buffle et al., 2004 ; Pinkernell and Von Gunten, 2001 ; and Wert et al., 2007 ). However, these bromate mitigation strategies have only been limitedly studied in wastewater matrices ( Soltermann et al., 2017 ), which generally have much higher ozone demand.…”

Direct potable reuse using full advanced treatment versus ozone biofiltration: A cost comparison

“…The DPR pilot effluent bromate was close to the primary MCL of 10 μg/L when FWH WRC effluent was blended at 25% with 75% Lake Lanier water. Assuming a hydrogen peroxide dose of 10 mg/L for significant (65%) reduction in bromate formation (Soltermann, Abegglen, Tschui, & Stahel, 2017), the cost of bromate addition may be estimated to be $657,000 annually. NDMA was also observed to be above the California notification level of 10 ng/L at this blend.…”