Formation of halogenated disinfection by-products during microfiltration and reverse osmosis treatment: Implications for water recycling

Abstract

A suite of 34 disinfection by-products (DBPs), including 8 halomethanes, 9 haloacetic acids, 6 haloacetonitriles, 6 haloaldehydes, 4 haloketones and the halonitromethane chloropicrin, were monitored in two microfiltration (MF) and reverse osmosis (RO) treatment plants as part of a larger study of chemical removal by MF/RO treatment for water recycling purposes. Both DBP detection frequency and concentration increased during treatment, and this was attributed to a chloramination step used to minimize RO membrane fouling. The degree of DBP formation was particularly related to plant residence time, with DBPs falling into two distinct groups; the first group in which DBP concentration increased with increasing residence time (e.g. chloroform and bromochloroacetaldehyde) and a second group in which increased residence time did not affect the concentration (e.g. dichloroacetic acid and 1,1-dichloropropanone). These results indicate that MF/RO plant design and wastewater quality are both important factors in minimising DBP formation within MF/RO treatment. RO rejection was influenced by several chemical-specific properties, including pKa, log Kow and DBP class. Rejection of haloacetic acids, present as charged molecules, was consistently better than 90% and did not alter with log Kow. For all other DBPs, present as neutral molecules, rejection was much more variable, and decreased with decreasing log Kow, although the effect of MW and log Kow on rejection could not be separated. The DBP formation described in this study lead to variable estimations of DBP removal by RO and thus it is recommended that DBPs are used as indicators of RO removal efficiency with caution, and only after DBP formation within RO treatment has been studied.

Safe Drinking Water? Effect of Wastewater Inputs and Source Water Impairment and Implications for Water Reuse

“…For example, in a recent study by Linge et al, full-scale plants in Perth, Australia, had several DBPs (THMs, dihalomethanes, HAAs, haloacetonitriles, and haloketones) in their MF/RO effluents that were not otherwise present in the incoming secondary wastewater or were initially present at significantly lower levels [162]. This is because MF/RO treatment typically includes chloramination of wastewater before MF to minimize RO membrane fouling [162,163], and thus, chloramination DBPs can form. The majority of DBPs are typically small, neutral molecules that show intermediate or poor RO rejection.…”

“…Plant residence time played an important role in the levels of DBPs observed, which resulted in greater frequency of detections at the full-scale plants vs. pilot-scale plants (which have smaller residence times). An unusual finding was the consistent detection of two dihalomethanes: dibromomethane and bromochloromethane, which are not routinely monitored and may be more toxicologically important than the regulated THMs [162]. It was suggested that DBP precursor removal should be optimized in secondary wastewater, such as implementing advanced biological treatment upstream of MF and RO processes.…”

Synthesis of robust flexible polyethersulfone ultrafiltration membranes supported on non-woven fabrics for separation of NOM from water

“…The dangers of HA in water manifest as a result of the use of disinfection processes such as chlorination. HA combines with disinfectants to form disinfection by-products (DBPs), such as trihalomethanes, halonitromethanes, haloacetonitriles, haloamides, halofuranones, iodo-acids and others, which are known to be carcinogenic and have the potential of causing adverse effects to human life (Fan et al, 2014;Hu et al, 2016;Jian et al, 2016;Kim et al, 2015;Linge et al, 2013;Xue et al, 2014).…”

Electrochemical removal of haloacetic acids in a three-dimensional electrochemical reactor with Pd-GAC particles as fixed filler and Pd-modified carbon paper as cathode

“…The Disinfectants/Disinfection Byproducts Rule established a maximum contaminant level (MCL) of 60 mg/L for the sum of five HAAs (HAA5 ¼ MCAA þ MBAA þ DCAA þ DBAA þ TCAA) under the Stage I (Pontinus, 1999). Biodegradation and reverse osmosis are used to remove HAAs from chlorinated water (Linge et al, 2013;McRae et al, 2004). The reverse osmosis treatment may generate a polluted waste that should be treated (Linge et al, 2013).…”

“…Biodegradation and reverse osmosis are used to remove HAAs from chlorinated water (Linge et al, 2013;McRae et al, 2004). The reverse osmosis treatment may generate a polluted waste that should be treated (Linge et al, 2013). Biodegradation may cause bacterial contamination in the treated water (McRae et al, 2004).…”