Low flow water quality in rivers; septic tank systems and high-resolution phosphorus signals

The Water Quality of the River Enborne, UK: Observations from High-Frequency Monitoring in a Rural, Lowland River System

“…Of the 163 registered consented discharges, 78 connect directly to a watercourse, but the proportion is unlikely to be as high overall (until recently, a direct connection was the main reason for registration). Directly-connected STSs would be expected to have more effect on watercourses than those where the water soaks away to groundwater, which would be expected to remove much of the P and some of the N. Recent research has demonstrated the significance of septic tank discharges on the quality of river systems and processes of in-stream P and N cycling [33][34][35]76], but more information about them is needed in order to assess their effects. The significant contribution of STS and STW discharges to flows also has important implications when considering the future water quality of the systems as the increasing pressures of urbanisation, abstraction and climatic variability further alter the balance between STW discharges and river flows [21,67,77].…”

“…In groundwater-dominated systems, historic contamination can also influence current water quality [32]. The importance of additional sources, such as septic tanks, sewage misconnections and combined sewer overflows on the water quality of river systems has also been highlighted in recent years (e.g., [33][34][35]). There is a lot of debate over whether nutrient releases from point or diffuse sources pose the greatest risk to streamwater quality (e.g., [14,36]).…”

The potamochemical symphony: new progress in the high-frequency acquisition of stream chemical data

“…In this study, the authors demonstrate the "act of discovery" permitted by such sampling scheme, by showing that the high sampling frequency of river hydrochemistry over sufficiently long time spans reveals patterns related to hydrological and biological drivers that are imperceptible at lower sampling frequency. Automated approaches, developed using probes installed directly in the river (Rozemeijer et al, 2010a;Macintosh et al, 2011;Cassidy and Jordan 2011;Dåbakk et al, 1999;Glasgow et al, 2004;Zhu et al, 2010;Yang et al, 2008), or using online instrumental devices in which continuously pumped water is injected (Rozemeijer et al, 2010b;Zabiegala et al, 2010;Jordan and Cassidy, 2011), are alternatives to sampling methods requiring human intervention. Several papers have been published over the last decade reporting existing devices mostly focused on monitoring dissolved N or P and organic matter (Clough et al, 2007;Kunz et al, 2012;Aubert et al, 2013b;Escoffier et al, 2016).…”

Assessment of a novel development policy for the control of phosphorus losses from private sewage systems to the Loch Leven catchment, Scotland, UK

“…Limited evidence of PSS impacts on waterbody P (May et al, 2010). The impact of PSS on 92 P concentrations in receiving waters is expected to increase in rural catchments 93 under low-flow conditions when dilution levels are reduced (Foy et al, 2003;May et 94 al., 2010;Macintosh et al, 2011 Loch Leven has a long and well-documented history of nutrient pollution, catchment 148 management and recovery Spears, 2012a, 2012b;May et al, 2012).…”

“…In this study, reductions were not 345 observed and this would not be enough to accommodate the TP reduction assumed 346 in the 125% rule from upgrading from primary to secondary treatments. Gill (2009) , raising concern that, during low flow 364 summer months when dilution capacity is reduced and ecological sensitivity is 365 greatest, such SRP delivery could promote eutrophication (Macintosh et al, 2011).…”