Predicting and minimising bromate formation in indirect potable reuse with AMOZONE - the SWIFT project (US)

SWIFT (swiftva.com) is the largest ozone-based indirect potable reuse (IPR) project in the world (article on SWIFT available). In a matter of a decade, IPR capacity bill be brought to 100MGD (ca. 380.000 m³/day). Our client HRSD (VA, US),hired AM-TEAM to develop and calibrate AMOZONE, a novel kinetic ozonation model that predicts bromate formation and micropollutant removal. We work closely together with Dynamita, the company behind the simulation platform SUMO (dynamita.com).

The main objectives were to assess:

• Different bromate mitigation strategies and analyse pros and cons
• Target contaminant removal performance (e;g. 1-4, dioxane)
• Operational cost

For any wastewater effluent or drinking water matrix, AMOZONE predicts:

• Ozone transfer and decay
• Organic matter conversion (DOC, COD, UV254)
• Target contaminant removal (numerous individual substances)
• Bromate formation
• Bromate mitigation (e.g. by monochloramine, H2O2, ...)

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We started modelling the SWIFT pilot ozonation train, consisting of a sidestream injection or bubble configuration, and five transfer and reaction columns. This train is given in the below figure: schematic (left),picture (middle) and SUMO model (right).

The below figure illustrates the predictive power of the model for one of the SWIFT pilot plants, but also for the Dutch advanced drinking water treatment plant in Bergambacht (Netherlands) operated by Dunea. The impact of bromate suppression and the predictive performance of target contaminant removal is excellent.

The model can then be used to run different scenarios and investigate bromate formation. The addition of monochloramine clearly reduces bromate, but also reduces the removal of some TrOCs, mainly those which are dominantely removed by HO radicals, such as 1,4-dioxane. Bromate suppression is hence a tradeoff between bromate suppression, target contaminant removal performance and operational cost.

Conclusions

The AMOZONE ozonation simulation model was succesfully calibrated for multiple of HRSD's wastewater treatment plants. It will now be used for smart plant design and operation. Coupled with CFD, it allows for effective reactor design. In the operational stage, AMOZONE can run as a digital twin monitoring bromate and target contaminant removal in real-time.

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