Browsing by Author "Bond, Tom"

Now showing 1 - 3 of 3
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    Chemical and biological oxidation of NOM surrogates and effect on HAA formation
    (Elsevier, 2009-06) Bond, Tom; Goslan, Emma Harriet; Jefferson, Bruce; Roddick, F.; Fan, L.; Parsons, Simon A.
    Formation of disinfection by-products (DBPs) can be controlled by removal of disinfection by-product precursors before disinfection. Variable success has been reported, depending on the treatment used and water tested. Chemical and biological oxidations are candidate technologies to control DBP formation. Given the uncertainty over the identity of DBP precursors, the use of surrogates of natural organic matter (NOM) allows fundamental probing of the links between compound character, removal and DBP formation. Nine compounds were chosen to represent NOM and their removal by two advanced oxidation processes (AOPs), UV-C irradiation and biological treatment compared while haloacetic acid (HAA) formation before and after treatment was measured. Although AOPs were able to fully remove all compounds, incomplete mineralisation led to increased HAA levels, dramatically in the case of two amino acids. Biological treatment was effective in removing amino acids but also moderately increased the HAA formation potential (HAAFP) of hydrophilic compounds. These findings indicate waters with high amino acid concentrations will be susceptible to raised HAA levels following AOP treatment and careful process selection for HAA control is required in such cases.
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    The formation of disinfection by-products from the chlorination and chloramination of amides
    (Elsevier, 2020-01-18) Sfynia, Chrysoula; Bond, Tom; Kanda, Rakesh; Templeton, Michael R.
    This study examined the potential of six aliphatic and aromatic amides, commonly found in natural waters or used as chemical aids in water treatment, to act as organic precursors for nine haloacetamides (HAcAms), five haloacetonitriles (HANs), regulated trihalomethanes (THMs) and haloacetic acids (HAAs) upon chlorination and chloramination. The impact of key experimental conditions, representative of drinking water, including pH (7 & 8), retention time (4 & 24 h) and bromide levels (0 & 100 μg/L), on the generation of the target DBPs was investigated. The highest aggregate DBP yields upon chlor(am)ination were reported for the aromatic and hydrophobic hydroxybenzamide; 2.7% ± 0.1% M/M (chlorination) and 1.7% M/M (chloramination). Increased reactivity was observed in aliphatic and hydrophilic compounds, acrylamide (2.5 ± 0.2% M/M) and acetamide (1.3 ± 0.2% M/M), in chlorination and chloramination, respectively. The addition of bromide increased average DBP yields by 50–70%. Relative to chlorination, the application of chloramines reduced DBP formation by 66.5% (without Br−) and by 46.4% (with Br−). However, bromine incorporation in HAAs and HAcAms was enhanced following chloramination, of concern due to the higher toxicological potency of brominated compounds.
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    Treatment of disinfection by-product precursors
    (Cranfield University, 2009-03) Bond, Tom; Jefferson, Bruce
    Natural organic matter (NOM) in drinking water forms disinfection byproducts (DBPs) through reactions with disinfectants, typically chlorine. Many DBPs are harmful to human health. Potentially the most effective means of controlling DBPs is to remove NOM precursors before disinfection. However, both DBP formation and removal of precursors in natural waters are variable and unpredictable, reflecting the diverse and variable nature of NOM. To better understand the relationships between DBP formation, compound character and treatment, experiments were undertaken with a range of NOM surrogates, assessing both DBP formation and treatability. Activated aromatics, β-dicarbonyls, masked β-dicarbonyls and amino acids were indentified as reactive precursor categories. No correlations were found between compound physicochemical properties and DBP formation. This indicates reliable bulk predictors of DBP formation are unlikely to exist in natural waters. In contrast, treatability was explicable in terms of compound physicochemical properties. Levels of removal by coagulation and anion exchange were controlled by amount of anionic charge, while molecular weight and hydrophobicity also affect removal by activated carbon and nanofiltration. Advanced oxidation processes (AOPs) at high doses was able to completely mineralise all NOM surrogates, however at lower doses DBP formation can be increased, dramatically in the case of two amino acids. Biotreatment is effective in removing amino acids but can cause moderate increases in DBP levels. A DBP control strategy is outlined based on this information. Where a high proportion of DBP precursors are highly-anionic aromatic compounds, coagulation may be sufficient for DBP control. Where reactive precursors are moderately-anionic carboxylic acids, ion exchange should be considered. In waters where less-treatable NOM has a high DBPgenerating capacity, activated carbon should be investigated for removal of neutral or weakly-charged aromatic precursors and a (hydrophobic) nanofiltration membrane for neutral or weakly-charged amino acids or carbohydrates.