Brookes, Justin D.Drikas, MaryTomlinson, Adam John2019-07-292019-07-292018http://hdl.handle.net/2440/120297Exposure to halogenated organic compounds known as disinfection by-products (DBPs) has been associated with congenital birth defects and increased occurrences of bladder and colorectum cancers. The suite and hence toxicity of the DBPs produced upon disinfection is best understood by the chemical composition and concentration of the reactive natural organic matter (NOM), which in turn is determined by the biogeophysical conditions of the catchment. Local meteorological conditions influence the relative allochthonous ( external) and autochthonous (internal) organic matter loads contributing towards the total carbon budget of the aquatic system. This thesis investigates the correlation of autochthonous organic matter with DBP formation by focusing on role of phytoplankton precursors towards the formation ofDBPs. The relative contribution of allochthonous and autochthonous NOM sources towards DBP formation was investigated by comparing winter inflows during a rainfall event and summer phytoplankton blooms. Winter inflows increased the relative contribution of allochthonous organic matter, correlating with the highest measured concentration of dissolved organic carbon (DOC). However, this did not coincide with the highest DBP formation recorded. Instead, summer phytoplankton blooms were significantly more reactive per milligram of DOC producing significantly higher concentrations of DBPs than winter inflows. Further, summer phytoplankton blooms increased the concentration of unknown DBPs (UTOX) and produced more genotoxic nitrogenous DBPs (N-DBPs). Phytoplankton organic precursors are often associated with a higher composition of hydrophilic organic matter, which is often recalcitrant to conventional treatment. This could potentially result in higher DBP formation after conventional treatment during periods where autochthonous NOM loads account for significant proportion of the carbon budget. The correlation between hydrophobic and hydrophilic properties was investigated via a linear model. This analysis highlighted the significant contribution of highly recalcitrant, hydrophilic neutrals towards the formation of DBPs, UTOX and towards specific categories ofDBP compounds. The relative hydrophilic and hydrophobic composition of phytoplankton is determined by the cells chemical composition and biological processes, which vary significantly between each species. Simulated phytoplankton blooms of Dolichospermum circinale ( cyanobacteria) and Ankistrodesmus sp. (green algae) were compared to determine their relative DBP formation upon chlorination. It was determined that Ankistrodesmus sp. contributed significantly more towards total DBP formation than D. circinale relative to their cellular biovolume. However, D. circinale produced higher concentrations of NDBPs which increases the relative genotoxicity of the DBPs formed. Finally, the removal efficiency of DBP precursors was investigated during a substantial surface phytoplankton bloom. The bulk of the phytoplankton bloom did not enter the treatment plant during this investigation due to thermal stratification of the reservoir and alteration in offtake height. The conventional treatment was efficient at removing the bulk of the organic matter however; the concentration of charged neutrals remained insignificantly affected. The product water contained significantly higher concentrations ofDBPs during the phytoplankton bloom in comparison to historic values however; the treated water would comply with the drinking water guidelines. Total unregulated DBP formation was still significant and was comprised of 44.8% of unknown DBPs.enWater treatmentchlorinationdisinfection by-productsphytoplanktonalgaeThesis