Disinfection By-products in Drinking Water
CHAPTER 18: Impacts of Ferrate Treatment on Natural Organic Matter, Disinfection By-Products, and Bromide
Published:29 Sep 2015
Y. Jiang, J. E. Goodwill, J. E. Tobiason, and D. A. Reckhow, in Disinfection By-products in Drinking Water, ed. K. C. Thompson, S. Gillespie, and E. Goslan, The Royal Society of Chemistry, 2015, pp. 151-160.
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This research investigated the impacts of ferrate (Fe(VI)) oxidation and subsequent conventional water treatment on natural organic matter (NOM), disinfection byproducts (DBPs), and bromide. Results showed that DBP precursor removal by the processes under investigation followed the order of: intermediate-ferrate treatment (ferrate added after coagulation) > ferric chloride coagulation alone ≈ pre-ferrate treatment followed by coagulation > direct ferrate oxidation alone. At typical Fe(VI) doses, direct Fe(VI) oxidation could significantly decrease DBP formation potentials (DBPFPs), i.e., trihalomethanes (THMs) 16−39%, trihaloacetic acids (THAAs) −8–46%, dihaloacetic acids (DHAAs) −2–17%, and dihaloacetonitriles (DHANs) 15–46%. In addition to achieving an effectiveness similar to ferric chloride coagulation for DBP precursor removal, pre-ferrate treatment may also allow the use of lower coagulant doses due to the Fe(III) introduced by Fe(VI) decay. On the other hand, intermediate-ferrate may result in substantially decreased concentrations of DBPs in the finished water due to prior removal of precursor compounds by coagulation. In addition, Fe(VI) will slowly oxidize bromide, forming low levels of active bromine and bromate. This is not expected to cause a serious problem as the levels are quite low.