Sorptive removal of disinfection by-product precursors from UK lowland surface waters: Impact of molecular weight and bromide

Abstract

The current study compared the impact of three different unit processes, coagulation, granular activated carbon (GAC), and a novel suspended ion exchange (SIX) technology, on disinfection by-product formation potential (DBPFP) from two UK lowland water sources with medium to high bromide content. Specific attention was given to the influence of the organic molecular weight (MW) fraction on DBPFP as well as the impact of bromide concentration.While few studies have investigated the impact of MW fractions from Liquid Chromatography with Organic Carbon Detection (LC-OCD) analysis on dissolved organic carbon (DOC) removal by different processes, none have studied the influence of DOC MW fractions from this analysis on DBP formation. The impact of higher bromide concentration was to decrease the total trihalomethane (THM) and haloacetic acid (HAA) mass concentration, in contrast to previously reported studies. Results indicated that for a moderate bromide concentration source (135 µg/L), the THM formation potential was reduced by 22% or 64% after coagulation or SIX treatment, respectively. For a high bromide content source (210 µg/L), the THM formation potential removal was 47% or 69% following GAC and SIX treatment, respectively. The trend was the same for HAAs, albeit with greater differences between the two processes/feedwaters with reference to overall removal. A statistical analysis indicated

Thorough Validation of Optimized Size Exclusion Chromatography-Total Organic Carbon Analysis for Natural Organic Matter in Fresh Waters

“…This has been proven by Ruhl et al (2012), who investigated the elution behavior of a large set of low MW acid compounds with LC-OCD-OND and showed that their elution occurs over the entire humic substances peak and not only in the shoulder, which is denoted as the low MW acid peak [23,24]. LC-OCD-OND has been applied in various studies to investigate the performance of drinking water treatment processes and/or to assess the impact of altering NOM characteristics in the source water on these processes [25][26][27][28], e.g., MacKeown et al (2021) found a correlation between trihalomethane formation potential and the concentration of building blocks in the water [26]. A drawback of LC-OCD-OND is that its implementation and data interpretation are still relatively complex, which impedes its use in routine analysis.…”

Revealing the effect of anion exchange resin conditioning on the pH and natural organic matter model compounds removal mechanisms

“…Humic substances, the most abundant NOM fraction in ground and surface water, are anionic under neutral to basic pH and therefore a good overall removal by anion exchange resins (AER) is expected and experimentally confirmed. For the BP and LMWN fraction, having a lower charge density under these pH conditions, removal using AER is more challenging, resulting in low removal efficiencies [3,8,[14][15][16][17][18]. However, the remaining NOM can be of concern since biopolymers can e.g.…”

“…However, the remaining NOM can be of concern since biopolymers can e.g. be related to the hydrothermolytical formation of organic acids in steam circuits (introducing an increased corrosion risk) [19], fouling in water treatment processes based on membrane filtration [20] and are potential disinfection by-product precursors [17]. "…”

“…Moreover, it must be noted that the findings for a specific water type may not always be extrapolated for another water type (e.g. raw or pretreated surface water, different geographical location etc) [17].…”