Trihalomethanes : from precursors to management strategies

Abstract

Investigation and characterisation of dissolved organic carbon (DOC) in raw and treated water from six case study sites located across Scotland identified the main aspects that influenced the formation of trihalomethanes (THMs) during and after disinfection. DOC and temperature were the main drivers of THMs found in this research. However, other variables such as bromide also played an important role in driving reactions towards brominated species of THMs. DOC quality, essentially of humic and fulvic origin remained constant along the year, but quantity affected THMs yields due to seasonal changes. Further DOC characterisation showed that treatment by coagulation or membrane filtration successfully removed hydrophobic DOC leaving a larger proportion of hydrophilic DOC in treated waters. This investigation identified two main groups of organic substances that corresponded to the hydrophilic fraction of DOC: phenolics and carboxylic acids. The final stage of the experimental work lead to the application of adsorption with activated carbon (AC) to remove these compounds from the treatment although at large doses. This work also presents a cost benefit analysis of two potential strategies to manage THMs precursors: the use of Ultraviolet (UV) scan sensors and AC adsorption. These technologies contribute to the enhancement of the industrial sponsors’ processes by improving compliance with regulatory quality and public health standards.