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    Simultaneous Bromate and Nitrate Reduction in Water Using Sulfur-Utilizing Autotrophic and Mixotrophic Denitrification Processes in a Fixed Bed Column Reactor
    (WILEY-BLACKWELL, 2014) Demirel, Sevgi; Uyanik, Ibrahim; Yurtsever, Adem; Celikten, Hakan; Ucar, Deniz
    Carcinogenic bromate (BrO3-) can be present in drinking water as a result of its formation from bromide (Br-) during ozonation. A fixed bed column reactor filled with elementel sulfur and limestone was operated for about six months under autotrophic and mixotrophic (autotrophic+heterotrophic) conditions at 30 degrees C. The reactor was operated at the hydraulic retention time (HRT) ranging from 16.5 to 10.1h at autotrophic conditions. Under mixotrophic conditions, 45mg/L NO3-N was removed completely at C/N ratio (mg CH3OH/mg NO3-N) between 0.55 and 1.66 at HRT of 10.1h. The average effluent pH was 7.8 and the sulfate concentration was lower than the Environmental Protection Agency limits at the mixotrophic stages. Efficient simultaneous BrO3- and nitrate removal was achieved at feed concentrations of 100-500 mu g/L BrO3- and 45mg/L nitrate under autotrophic and mixotrophic conditions. Effluent Br- measurements indicated that BrO3- was completely reduced without accumulation of by-products.
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    Simultaneous fluoride and nitrate removal from drinking water using mixotrophic denitrification processes in a fixed bed column reactor
    (Desalination Publ, 2019) Demirel, Sevgi; Uyanik, Ibrahim
    Nitrate and fluoride are water contaminants found together in some regions where agricultural activities are widespread. The concentration of these contaminants is important since nitrate causes methemoglobinemia in infants and fluride causes dental diseases. In this study, a fixed bed column reactor was used with sulfur and limestone media to remove these contaminants under simultaneously autotrophic and heterotrophic (mixotrophic) conditions at 30 degrees C. The reactor was operated under these conditions for 125 d and 49.7 mg/L of NO3-N and 5.3 +/- 0.4 mg/L of F- were removed at 95.0 and 90.0% efficiency, respectively. Effluent pH was 7.8 and alkalinity was not exceeded 200 mg/L. Removal mechanisms of nitrate and fluoride were biological denitrification and physicochemical ( adsorption and precipitation), respectively, since batch experiments agreed that the removal mechanism of fluoride was not biological. This study showed that both NO3- and F- can be removed in one reactor under mixotrophic conditions, simultaneously.