Changes in the quality of river water before, during and after a major flood event associated with a La Niña cycle and treatment for drinking purposes

Mohamad Fared Murshed , Zeeshan Aslam , Rosmala Lewis , Christopher Chow , Dongsheng Wang , Mary Drikas , John van Leeuwen


Received December 18, 2013,Revised February 12, 2014, Accepted , Available online October 22, 2014

Volume 26,2014,Pages 1985-1993

The treatment of organics present in the lower reaches of a major river system (the Murray- Darling Basin, Australia) before (March-July 2010), during (December 2010-May 2011) and after (April-December 2012) a major flood period was investigated. The flood period (over 6 months) occurred during an intense La Niña cycle, leading to rapid and high increases in river flows and organic loads in the river water. Dissolved organic carbon (DOC) increased (2-3 times) to high concentrations (up to 16 mg/L) andwas found to correlatewith river flow rates. The treatability of organics was studied using conventional jar testswith alumand an enhanced coagulationmodel (mEnCo©). Predicted mean alum dose rates (per mg DOC) were higher before (9.1 mg alum/mg DOC) and after (8.5 mg alum/mg DOC) than during the flood event (8.0 mg alum/mg DOC), indicating differences in the character of the organics in raw waters. To assess the character of natural organic matter present in raw and treated waters, high performance size exclusion chromatography with UV and fluorescence detectors were used. During the flood period, high molecular weight UV absorbing compounds (>2 kDa) were mostly detected in waters collected, but were not evident in waters collected before and afterwards. The relative abundances of humic-like and protein-like compounds during and following the flood period were also investigated and found to be of a higher molecular weight during the flood period. The treatability of the organics was found to vary over the three climate conditions investigated. © 2014 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences.

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