title: Temporal variability in domestic point source discharges and their associated impact on receiving waters.
abstract: Discharges from the widely distributed small point sources of pollutants such as septic tanks contribute to microbial and nutrient loading of streams and can pose risks to human health and stream ecology, especially during periods of ecological sensitivity. Here we present the first comprehensive data on the compositional variability of septic tank effluents (STE) as a potential source of water pollution during different seasons and the associated links to their influence on stream waters. To determine STE parameters and nutrient variations, the biological and physicochemical properties of effluents sampled quarterly from 12 septic tank systems were investigated with concurrent analyses of upstream and downstream receiving waters. The study revealed that during the warmer dryer months of spring and summer, effluents were similar in composition, as were the colder wetter months of autumn and winter. However, spring/summer effluents differed significantly (P<0.05) from autumn/winter for concentrations of biological oxygen demand (BOD), arsenic, barium (Ba), cobalt, chromium, manganese, strontium (Sr), titanium, tungsten (W) and zinc (Zn). With the exception of BOD, Ba and Sr which were greater in summer and spring, the concentrations of these parameters were greater in winter. Receiving stream waters also showed significant seasonal variation (P≤0.05) in alkalinity, BOD, dissolved organic carbon, sulphate, sulphur, lithium, W, Zn and Escherichiacoli abundance. There was a clear significant influence of STE on downstream waters relative to upstream from the source (P<0.05) for total suspended solids, total particulate P and N, ammonium-N, coliforms and E. coli. The findings of this study found seasonal variation in STE and place effluent discharges as a factor affecting adjacent stream quality and call for appropriate measures to reduce or redirect STE discharges away from water courses.
authors.affiliation: The James Hutton Institute, Craigiebuckler, Aberdeen AB15 8QH, Scotland, UK. Electronic address: samia.richards@hutton.ac.uk.
authors.forename: Samia
authors.initials: S
authors.lastname: Richards
authors.affiliation: Bangor University, Bangor, Gwynedd LL57 2UW, UK.
authors.forename: Paul J A
authors.initials: PJ
authors.lastname: Withers
authors.affiliation: The James Hutton Institute, Craigiebuckler, Aberdeen AB15 8QH, Scotland, UK.
authors.forename: Eric
authors.initials: E
authors.lastname: Paterson
authors.affiliation: Agri-Food and Biosciences Institute, Newforge Lane, Belfast BT9 5PX, UK.
authors.forename: Colin W
authors.initials: CW
authors.lastname: McRoberts
authors.affiliation: The James Hutton Institute, Craigiebuckler, Aberdeen AB15 8QH, Scotland, UK.
authors.forename: Marc
authors.initials: M
authors.lastname: Stutter
mesh_terms: D004784:Environmental Monitoring; D045483:Rivers / Q000737:chemistry; D012606:Scotland; D012621:Seasons; D014865:Waste Disposal, Fluid; D062065:Wastewater / Q000032:analysis*; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014877:Water Pollution, Chemical / Q000032:analysis*
chemical_list: D062065:Wastewater; D014874:Water Pollutants, Chemical
keywords: Eutrophication; Microbial populations; Phosphorus; Septic tank effluent discharge; Water quality