Natural attenuation of nitrogen loading from septic effluents: Spatial and environmental controls

Meile, Christof; Porubsky, William; Walker, Robert L.; Payne, Kathryn M.

doi:10.1016/j.watres.2009.11.019

Cited by 29 publications

(17 citation statements)

References 30 publications

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“…During the growing season, septic system effluent may be quickly immobilized along hydrological pathways before it reaches the stream network. Other research has shown increased septic system distance from surface water can decrease septic influence on surface water N [ Meile et al , 2010]; however, septic NO 3 − removal can be limited if carbon is limiting microbial denitrification [ Colman et al , 2004]. It is possible that hydrologic connectivity between septic systems and the streams was limited or nonexistent preventing septic effluent transport to the stream.…”

Section: Discussionmentioning

confidence: 99%

Quantifying watershed sensitivity to spatially variable N loading and the relative importance of watershed N retention mechanisms

Gardner

McGlynn

Marshall

2011

Water Resources Research

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[1] The link between watershed nitrogen (N) loading and watershed nitrate (NO 3 À ) export is poorly understood yet critical to addressing the growing global problem of watershed N enrichment. We introduce the Big Sky nutrient export model (BiSN) which incorporates spatial stream water chemistry, data from instream tracer additions and geologic weathering experiments, and terrain and land use analysis to quantify the spatial variability of watershed sensitivity to N loading and the relative importance of upland, riparian, and instream N retention (storage, removal, or transformation) across land use/land cover (LULC) and landscape positions. Bayesian Markov chain Monte Carlo (MCMC) methods were used for model specification and were helpful in assessing model and parameter uncertainty and advancing understanding of the primary processes governing watershed NO 3 À export. Modeling results revealed that small amounts of wastewater loading occurring in watershed areas with short travel times to the stream had disproportionately large impacts on watershed nitrate (NO 3 À ) export compared to spatially distributed N loading or localized N loading in watershed areas with longer travel times. In contrast, spatially distributed N inputs of greater magnitude (terrestrial storage release and septic systems) had little influence on NO 3

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Section: Discussionmentioning

confidence: 99%

Quantifying watershed sensitivity to spatially variable N loading and the relative importance of watershed N retention mechanisms

Gardner

McGlynn

Marshall

2011

Water Resources Research

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“…These gradients drive microbially mediated chemical transformations that modify solute concentrations in groundwater prior to discharge. Chemical transformations in coastal aquifers include dissolved organic carbon (DOC) degradation (Kroeger & Charette, ), aerobic respiration (Slomp & Van Cappellen, ), denitrification (Meile et al, ; Santos et al, ), nitrification (Ullman et al, ), anaerobic ammonium oxidation (Slomp & Van Cappellen, ), dissimilatory

{NO}_{3}^{-}

reduction to ammonium (Santoro, ), sulfate reduction (McAllister et al, ), and iron oxidation (Charette & Sholkovitz, ). Iron oxidation leads to precipitation of iron oxides onto sediment surfaces that adsorb and sequester solutes including phosphate and arsenic along groundwater flow paths (Charette & Sholkovitz, ; Jung et al, ).…”

Section: Introductionmentioning

confidence: 99%

“…Conversely, low groundwater velocities and high DOC oxidation rates increased denitrification rates and significantly reduced

{NO}_{3}^{-}

fluxes across the aquifer‐ocean interface (Spiteri et al, ). Meile et al () assessed the role of point‐source septic systems as potential N sources by evaluating the importance of the freshwater gradient, DOC reactivity, and septic system setback distance on

{NO}_{3}^{-}

removal along the lower interface. Hydrologically more complex reactive transport models have demonstrated the importance of tides on regulating the fate of chemicals in coastal aquifers.…”

Section: Introductionmentioning

confidence: 99%

Physical Controls on Biogeochemical Processes in Intertidal Zones of Beach Aquifers

Heiss

Post

Laattoe

et al. 2017

Water Resources Research

100

103

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Marine ecosystems are sensitive to inputs of chemicals from submarine groundwater discharge. Tidally influenced saltwater‐freshwater mixing zones in beach aquifers can host biogeochemical transformations that modify chemical loads prior to discharge. A numerical variable‐density groundwater flow and reactive transport model was used to evaluate the physical controls on reactivity for mixing‐dependent and mixing‐independent reactions in beach aquifers, represented as denitrification and sulfate reduction, respectively. A sensitivity analysis was performed across typical values of tidal amplitude, hydraulic conductivity, terrestrial freshwater flux, beach slope, dispersivity, and DOC reactivity. For the model setup and conditions tested, the simulations demonstrate that denitrification can remove up to 100% of terrestrially derived nitrate, and sulfate reduction can transform up to 8% of seawater‐derived sulfate prior to discharge. Tidally driven mixing between saltwater and freshwater promotes denitrification along the boundary of the intertidal saltwater circulation cell in pore water between 1 and 10 ppt. The denitrification zone occupies on average 49% of the mixing zone. Denitrification rates are highest on the landward side of the circulation cell and decrease along circulating flow paths. Reactivity for mixing‐dependent reactions increases with the size of the mixing zone and solute supply, while mixing‐independent reactivity is controlled primarily by solute supply. The results provide insights into the types of beaches most efficient in altering fluxes of chemicals prior to discharge and could be built upon to help engineer beaches to enhance reactivity. The findings have implications for management to protect coastal ecosystems and the estimation of chemical fluxes to the ocean.

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“…These similarities suggest that conventional septic systems and some sewers may not differ in nitrogen attenuation, depending on adequate setbacks and the density of septic systems. Meile et al (2010) found that increasing setback distances may increase TN reductions through denitrification processes.…”

Section: Discussionmentioning

confidence: 99%

Wastewater Nitrogen Contributions to Coastal Plain Watersheds, NC, USA

Iverson

O’Driscoll

Humphrey

et al. 2015

Water Air Soil Pollut

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Nitrogen inputs to coastal watersheds have been linked to eutrophication. However, the role that domestic sources of wastewater play in contributing nitrogen to coastal watersheds is not well known in the southeastern USA. In a yearlong study (2011)(2012), nitrogen concentrations were compared in watersheds served by septic systems and a centralized sewer system in the Coastal Plain of North Carolina. Surface and groundwater samples from septic systems and sewer watersheds were analyzed for total dissolved nitrogen (TDN), total nitrogen, and nitrogen and oxygen isotopes in nitrate. Groundwater beneath the drainfield and adjacent to streams had median concentrations of TDN at 5.9 and 4.4 mg/L, respectively. Additionally, median groundwater-transported loads of TDN to the stream from septic systems sites (0.6 kg-TDN/year) were significantly greater than sites in sewer watersheds (0.2 kg-TDN/year). Isotopic analyses revealed that effluent from septic systems was the primary source of nitrate in watersheds served by septic systems, while fertilizer and/or soil organic matter were dominant sources of nitrate in sewer watersheds. Nitrogen exported from septic systems contributed to elevated nitrogen concentrations in groundwater and streams throughout the watershed, whereas nitrogen exports from sewers were focused at a single point source and affected surface water concentrations. Based on watershed TDN exports from septic systems minus TDN exports from sewers watersheds, it was e s t i m a t e d t h a t s e p t i c s y s t e m s c o n t r i b u t e d 1.6 kg TDN/ha/year to watershed exports of TDN. Overall, septic systems and sewers contributed to elevated nitrogen loading and should be considered in nutrient-sensitive watershed management.

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Natural attenuation of nitrogen loading from septic effluents: Spatial and environmental controls

Cited by 29 publications

References 30 publications

Quantifying watershed sensitivity to spatially variable N loading and the relative importance of watershed N retention mechanisms

Quantifying watershed sensitivity to spatially variable N loading and the relative importance of watershed N retention mechanisms

Physical Controls on Biogeochemical Processes in Intertidal Zones of Beach Aquifers

Wastewater Nitrogen Contributions to Coastal Plain Watersheds, NC, USA

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