As climate change and freshwater scarcity worsen, demand grows to secure new reliable sources of potable water, including desalinated seawater and recycled wastewater. During a recent techno-economic assessment, our research group identified significant overlaps between desalination and potable reuse treatment trains. Significant energetic benefits, without the capital cost, footprint, and other concerns associated with building a new plant, could be obtained by blending seawater and wastewater upstream of potable reuse treatment plants.  In this work, for the first time, the technoeconomic ramifications of pre-treatment blending of seawater and treated wastewater for potable reuse applications are explored. The value of diluting either stream with the other is quantified in two parts: (1) diluting seawater with wastewater to reduce specific energy demand in the reverse osmosis process, and (2) diluting wastewater with seawater to reduce public health risks associated with direct potable reuse. This study is ongoing; results both from modeling and experimental work will be presented. One critical consideration is the speciation of the oxidants formed during chlorine addition to prevent biofouling. Wastewater chlorination produces chloramines by ammonia oxidation, and seawater chlorination produces free bromine by bromide oxidation. Blending the two produces bromamines, which are associated with the formation of certain toxic byproducts such as NDMA. Bromamine formation is expected to be a function of which stream is chlorinated, and whether the disinfection happens before or after blending. In addition to chemical considerations, specific energy demand associated with the reverse osmosis process will be modeled as a function of membrane properties and recovery rate. Parameters including blending ratio, pH, pre-disinfectant choice, membrane type, and recovery rate will be determined based on the results from the modeling work. Finally, bench-scale testing results from these treatment trains under different blending scenarios will be presented. The chemical composition and water quality of the blended stream after each treatment step will be determined via mass spectrometry. The results from this study will provide new insights into the implementation and optimization of desalination and potable reuse systems.

Seawater augmented reuse: Study of upstream blending for potable reuse

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.