Abstract
The effects of synthetic goethite (α-FeOOH) used as the catalyst in catalytic ozonation for the degradation of disinfection by-product (DBP) precursors are investigated. A biofiltration column applied following the catalytic ozonation process is used to evaluate the efficiency of removing DBP precursors via biotreatment. Ozone can rapidly react with aromatic compounds and oxidize organic compounds, resulting in a decrease in the fluorescence intensity of dissolved organic matter (DOM). In addition, catalytic ozonation can break down large organic molecules, which causes a blue shift in the emission-excitation matrix spectra. Water treated with catalytic ozonation is composed of low-molecular structures, including soluble microbial products (SMPs) and other aromatic proteins (APs). The DOM in SMPs and APs is removed by subsequent biofiltration. Catalytic ozonation has a higher removal efficiency for dissolved organic carbon and higher ultraviolet absorbance at 254 nm compared to those of ozonation without a catalyst. The use of catalytic ozonation and subsequent biofiltration leads to a lower DBP formation potential during chlorination compared to that obtained using ozonation and catalytic ozonation alone. Regarding DBP species during chlorination, the bromine incorporation factor (BIF) of trihalomethanes and haloacetic acids increases with increasing catalyst dosage in catalytic ozonation. Moreover, the highest BIF is obtained for catalytic ozonation and subsequent biofiltration.
Highlights
Disinfection by-products (DBPs) are regulated in many countries, due to their genotoxicity, mutagenicity and carcinogenicity [1]
ultraviolet absorbance at 254 nm (UV254) increased with increases in the catalyst dosage in catalytic ozonation
The effects of α-FeOOH catalyst used in catalytic ozonation on the structural changes of dissolved organic matter (DOM), water quality parameters (DOC and UV254) and DBP formation potential (THMs and HAA9) were investigated
Summary
Disinfection by-products (DBPs) are regulated in many countries, due to their genotoxicity, mutagenicity and carcinogenicity [1]. Few studies have discussed the structural changes in DOM caused by catalytic ozonation and their influence on DBPFP [6,15] Another important issue regarding the formation of DBPs is that water containing bromide ion (Br−) will influence the species of THM and HAA during chlorination and might cause the formation of bromate after the ozonation treatment [16]. Goethite (α-FeOOH) is used as the catalyst in a fluidized-bed reactor (FBR) for the purpose of catalytic ozonation followed by biofiltration This system is constructed to investigate the transformation of DOM via emission-excitation matrix (EEM) spectra, to evaluate the removal efficiency of dissolved organic carbon (DOC), ultraviolet absorbance at 254 nm (UV254) and specific ultraviolet absorbance (SUVA) and C-DBP (THMs and HAAs) formation potential during chlorination. The bromine impact factor (BIF) of C-DBPs and bromate concentrations are investigated in order to study the formation and speciation of DBPs under various operating conditions and treatment processes
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