Seasonal variation in the nature of DOM in a river and drinking water reservoir of a closed catchment.
Dissolved organic matter (DOM) in surface waters used for drinking purposes can vary markedly in character depending on its source within catchments and the timing and intensity of rainfall events. Here we report the findings of a study on the character and concentration of DOM in waters collected during different seasons from Myponga River and Reservoir, South Australia. The character of DOM was assessed in terms of its treatability by enhanced coagulation and potential for disinfection by-product i.e. trihalomethane (THM) formation. During the wet seasons (winter and spring), water samples from the river had higher DOC concentrations (X¯: 21 mg/L) and DOM of higher average molecular weight (AMW: 1526 Da) than waters collected during the dry seasons (summer and autumn: DOC: 13 mg/L; AMW: 1385 Da). Even though these features led to an increase in the percentage removal of organics by coagulation with alum (64% for wet compared with 53% for dry season samples) and a lower alum dose rate (10 versus 15 mg alum/mg DOC removal), there was a higher THM formation potential (THMFP) from wet season waters (treated waters: 217 μg/L vs 172 μg/L). For reservoir waters, samples collected during the wet seasons had an average DOC concentration (X¯: 15 mg/L), percentage removal of organics by alum (54%), alum dose rates (13 mg/mg DOC) and THMFP (treated waters: 207 μg/L) that were similar to samples collected during the dry seasons (mean DOC: 15 mg/L; removal of organics: 52%; alum dose rate: 13 mg/mg DOC; THMFP: 212 μg/L for treated waters). These results show that DOM present in river waters and treatability by alum are highly impacted by seasonal environmental variations. However these in reservoir waters exhibit less seasonal variability. Storage of large volumes of water in the reservoir enables mixing of influent waters and stabilization of water quality.
School of Natural and Built Environments, University of South Australia, South Australia, 5095, Australia.
John
J
Awad
School of Natural and Built Environments, University of South Australia, South Australia, 5095, Australia; SKLEAC, Research Centre for Eco-environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing, 100085, China. Electronic address: John.vanleeuwen@unisa.edu.au.
John
J
van Leeuwen
School of Natural and Built Environments, University of South Australia, South Australia, 5095, Australia; Australian Water Quality Centre, SA Water Corporation, 250 Victoria Square, Adelaide, South Australia, 5000, Australia; SKLEAC, Research Centre for Eco-environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing, 100085, China.
Christopher W K
CWK
Chow
School of Agriculture, Food & Wine and Waite Research Institute, The University of Adelaide, Urrbrae, South Australia, 5064, Australia.
Ronald J
RJ
Smernik
School of Natural and Built Environments, University of South Australia, South Australia, 5095, Australia.
Sharolyn J
SJ
Anderson
School of Biological Sciences, The University of Adelaide, North Terrace, South Australia, 5005, Australia; South Australian Research and Development Institute, Urrbrae, South Australia, 5064, Australia.
Jim W
JW
Cox
D002980:Climate; D060766:Drinking Water / Q000032:analysis* / Q000737:chemistry*; D004784:Environmental Monitoring; D005618:Fresh Water / Q000032:analysis* / Q000737:chemistry*; D009930:Organic Chemicals / Q000032:analysis*; D045483:Rivers / Q000737:chemistry*; D012621:Seasons; D013021:South Australia
D060766:Drinking Water; D009930:Organic Chemicals
Seasonal variation; Surface waters; THMFP; Treatability of organic