Investigation of disinfection byproducts formation in ferrate(VI) pre-oxidation of NOM and its model compounds followed by chlorination

• Alterations in structural properties of natural organic matter by Fe(VI) were observed.
• Formation of DBP depends highly on Fe(VI) dose.
• THM formation usually decreases in Fe(VI) pre-oxidation and subsequent chlorination.
• Both kinetics and products of Fe(VI)/chlorine oxidation determine N-DBP and C-DBP formation.

This study investigated the effect of disinfection by-products (DBPs) formation in pre-oxidation with ferrate(VI) (FeVIO42−, Fe(VI)) and relationship between subsequent chlorination of Suwannee river natural organic matter (SRNOM) and eight model compounds containing moieties of alcohol, aldehyde, amines, amino acids, and phenol. The DBPs studied were trihalomethanes (THMs), chloral hydrate (CH), haloacetonitriles (HANs), and trichloronitromethane (TCNM). When the interaction of Fe(VI) and SRNOM was independently examined at pH 7.0, a decrease was seen in dissolved organic carbon and in the hydrophobic and hydrophilic fractions of NOM. With the model compounds, the results showed that Fe(VI) pre-oxidation and subsequent chlorination decreased the formation of THMs with most of the compounds except amines and glycine. The effect of Fe(VI) preoxidation on CH and HANs formation from model compounds varied and was dependent on ferrate doses. Fe(VI) pre-oxidation significantly enhanced TCNM formation, compared to without pre-oxidation, from subsequent chlorination of methylamine, dimethylamine and glycine and the formation increased with increasing doses of ferrate. Correlations of DBPs formation between SRNOM and model compounds were sought to identify the moieties involved in influencing the formation of DBPs. The generation of DBPs is described using the parent molecules and the kinetics and reaction products of Fe(VI)/chlorine oxidation.

Figure optionsDownload as PowerPoint slide