Absorbance data collected from an online UV absorbance spectrophotometer installed for water quality monitoring at a conventional drinking water treatment plant was used to develop surrogate parameters for treatment process monitoring and optimisation. Surrogate parameters were developed via data analysis of collected online data as well as by targeted selection from previous research knowledge. These parameters were validated in the field using the same online spectrophotometer to gauge their response to events caused by operational changes, such as high chlorine demand and changes in natural organic matter (NOM). Almost all parameters generated responses comparable to the commonly used process assessment UV online parameter, absorbance at 254nm. Some parameters, such as the derivative of absorbance at 290nm and the second derivative of absorbance at 310nm, generated responses far exceeding the standard monitoring parameter, making them potentially useful tools for control of operational treatment processes. It is hoped that in future, these and other novel UV absorbance parameters can be monitored simultaneously to reflect water quality change to further the application of this technology in optimisation of water treatment.
Taste-and-odour complaints are a leading cause of consumer dissatisfaction with drinking water. The aim of this study was to determine odour threshold concentration ranges and descriptors, using a Western Australian odour panel, for chlorine, bromine, chlorine added to bromide ions, the four major regulated trihalomethanes (THMs), and combined THMs. An odour panel was established and trained to determine odour threshold concentration ranges for odorous compounds typically found in drinking water at 25 degrees C, using modified flavour profile analysis (FPA) techniques. Bromine and chlorine had the same odour threshold concentration ranges and were both described as having a chlorinous odour by a majority of panellists, but the odour threshold concentration range of bromine expressed in free chlorine equivalents was lower that that of chlorine. It is likely that the free chlorine equivalent residuals measured in many parts of distribution systems in Western Australia are comprised of some portion of bromine and that bromine has the potential to cause chlorinous odours at a lower free chlorine equivalent concentration than chlorine itself. In fact, bromine is the likely cause of any chlorinous odours in Western Australian distributed waters when the free chlorine equivalent concentration is between 0.04 and 0.1 mg L(-1). Odour threshold concentrations for the four individual THMs ranged from 0.06-0.16 mg L(-1), and the odour threshold concentration range was 0.10 + or - 0.09 mg L(-1) when the four THMs were combined (in equal mass concentrations). These concentrations are below the maximum guideline value for total THM concentration in Australia so odours from these compounds may possibly be observed in distributed waters. However, while the presence of THMs may contribute to any sweet/fragrant/floral and chemical/hydrocarbon odours in local drinking waters, the THMs are unlikely to contribute to chlorinous odours.
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