The potential benefits of utilizing ferrate (Fe(VI)) in drinking water treatment have been noted by many researchers over a long time period yet no significant implementation has occurred in the drinking water industry. Researchers have most commonly utilized ideal controlled laboratory conditions to isolate the oxidation and disinfection performance of ferrate, usually for specific target compounds.  While significant understanding of fundamental ferrate chemistry has been gained, there has been a lack of assessment of the impacts of ferrate addition to natural waters under conditions that would be used in full-scale drinking water treatment. With support from the US Environmental Protection Agency, researchers at the University of Massachusetts Amherst have been studying implementation of ferrate oxidation for natural waters using batch and continuous flow treatment processes at the laboratory scale.  Ferrate has been dosed to raw water as a pre-oxidant prior to coagulation and solid/liquid separation and ferrate has been dosed as an intermediate oxidant after coagulation and particle removal by clarification.  Treatment performance impact assessment has included evaluation of natural organic matter removal as measured by total organic carbon, UV254 absorbance and disinfection by-product formation potential (DBPFP) as well as an evaluation of ferrate impacts on particle removal and filtration head loss, especially in light of the formation of ferric iron particles from Fe(VI) reduction to Fe(III).  Results to-date show that ferrate has beneficial oxidation impacts that are similar to the use of ozone and that oxidation of DBP precursors is most effective for intermediate ferrate oxidation. Continuous flow experiments have shown no significant detrimental impact of ferrate resultant particles on solid-liquid separation or media filter head loss development in either pre-oxidation or intermediate oxidation mode.  Other challenges for implementation include the need for commercial production of a stable ferrate salt (e.g., K<sub>2</sub>FeO<sub>4</sub>) as well as a reasonably stable concentrated feed solution for daily use.  Demonstration of ferrate disinfection performance and the ability to assess ferrate exposure could also significantly impact future implementation of ferrate for drinking water treatment.

Implementation of ferrate for drinking water treatment

253rd National Meeting (2017)

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