Abstract:
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.
