Nitrogen Fate and Transport in a Conventional Onsite Wastewater Treatment System Installed in a Clay Soil: A Nitrogen Chain Model

Bradshaw, J. Kenneth; Radcliffe, D. E.; Šimůnek, Jiřı́; Wunsch, Assaf; McCray, John E.

doi:10.2136/vzj2012.0150

Cited by 11 publications

(20 citation statements)

References 19 publications

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“…The fitted value indicates that denitrification occurs when water contents rise above 42% of the value for field capacity. This threshold is <60% of the relative water content reported by Bradshaw et al (2013) and Beggs et al (2004) in OWTS drain fields. However, Schepers and Raun (2008) reported that denitrification can start in 20% water-filled pore space and increases with an increasing percentage of water-filled capacity, depending on the availability of C and NO 3 .…”

Section: Aquifer As Presented Inmentioning

confidence: 64%

Modeling the Effects of Onsite Wastewater Treatment Systems on Nitrate Loads Using SWAT in an Urban Watershed of Metropolitan Atlanta

et al. 2017

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Onsite wastewater treatment systems (OWTSs) can be a source of nitrogen (N) pollution in both surface and ground waters. In metropolitan Atlanta, GA, >26% of homes are on OWTSs. In a previous article, we used the Soil Water Assessment Tool to model the effect of OWTSs on stream flow in the Big Haynes Creek Watershed in metropolitan Atlanta. The objective of this study was to estimate the effect of OWTSs, including failing systems, on nitrate as N (NO-N) load in the same watershed. Big Haynes Creek has a drainage area of 44 km with mainly urban land use (67%), and most of the homes use OWTSs. A USGS gauge station where stream flow was measured daily and NO-N concentrations were measured monthly was used as the outlet. The model was simulated for 12 yr. Overall, the model showed satisfactory daily stream flow and NO-N loads with Nash-Sutcliffe coefficients of 0.62 and 0.58 for the calibration period and 0.67 and 0.33 for the validation period at the outlet of the Big Haynes Watershed. Onsite wastewater treatment systems caused an average increase in NO-N load of 23% at the watershed scale and 29% at the outlet of a subbasin with the highest density of OWTSs. Failing OWTSs were estimated to be 1% of the total systems and did not have a large impact on stream flow or NO-N load. The NO-N load was 74% of the total N load in the watershed, indicating the important effect of OWTSs on stream loads in this urban watershed.

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Section: Aquifer As Presented Inmentioning

confidence: 64%

Modeling the Effects of Onsite Wastewater Treatment Systems on Nitrate Loads Using SWAT in an Urban Watershed of Metropolitan Atlanta

et al. 2017

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“…The model included the nitrification of NH 4 -N and PMN to NO 3 -N as well as denitrification from NO 3 -N to dinitrogen/ nitrous oxide (N 2 /N 2 O). The intermediate product of nitrification, NO 2 -N, was ignored to simplify the chain model (Bradshaw et al 2013). The first-order reaction rates for the change in NH 4 -N + PMN (equation 6) and NO 3 -N (equation 7) concentrations that result from the N chain models were…”

Section: Methodsmentioning

confidence: 99%

“…Complete denitrification of NO 3 -N was assumed to occur under saturated conditions, and rate constants were set the same as for nitrification (table 2). Adsorption coefficients for NH 4 -N/PMN and NO 3 -N were 10 and 0.78 cm 3 g -1 for all soil horizons (table 2), and were based on values from Bradshaw et al (2013). Based on R 2 in model output, the adsorption coefficient was optimized across models using manual calibration to provide a more acceptable fit to observed NO 3 -N concentrations at the 8 and 75 cm depths.…”

Section: Soil Layer Particle Fraction (%) (Cm)mentioning

confidence: 99%

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Simulated nitrate leaching in annually cover cropped and perennial living mulch corn production systems

Andrews¹,

Sanders²,

Cabrera³

et al. 2019

Journal of Soil and Water Conservation

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Corn (Zea mays) grown in the southern Piedmont requires 200 to 280 kg nitrogen (N) ha-1 annually and requires up to 0.87 cm of water per day, making groundwater systems susceptible to nitrate (NO 3-) leaching. A perennial white clover (Trifolium repens L.) living mulch (LM) system may reduce NO 3-N leaching by using legume N to replace mineral N, though little information is available on such a system in the southern Piedmont. Therefore, a HYDRUS-1D model was used to simulate water and NO 3-N flux in three cover crop systems. Cereal rye (Secale cereal L.) (CR), crimson clover (Trifolium incarnatum L.) (CC), and a white clover LM were fertilized with 280, 168, and 56 kg N ha-1. The HYDRUS-1D model was calibrated and validated with observed water contents and NO 3-N data that were collected over two years. Water and NO 3-N flux models were created for each treatment and evaluated using coefficient of determination, percentage bias, and index of agreement, and showed good agreement to observed data. Nitrate leaching below 1 m in 2015/2016 was 23.5, 12.7, and 21.4 kg ha-1 for the CC, LM, and CR treatments, respectively, but was less than 1 kg ha-1 for all treatments in 2016/2017 due to prolonged drought. Differences in leached NO 3-N among treatments were attributed to variation in mineral N application rate and NO 3-N uptake by cover crops. Overall, results suggest that the use of a perennial LM system may reduce NO 3-N leaching when compared to annual CC and CR cover crop systems.

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“…The production of these gases during nitrification and denitrification is influenced by the concentration and diffusion rate of O 2 in the soil (Bollmann and Conrad, 1998; Zhu et al, 2013; Peng et al, 2014; Medinets et al, 2015). As it is difficult to measure O 2 in the soil, soil moisture content is often used as a proxy for both O 2 concentration and diffusion rate (Bradshaw et al, 2013b; Geza et al, 2014). Beggs et al (2011) observed that nitrification rates increased linearly at 10 to 15% volumetric water content (VWC) and decreased at 26 to 45% VWC.…”

mentioning

confidence: 99%

Fate of Effluent‐Borne Nitrogen in the Mounded Drainfield of an Onsite Wastewater Treatment System

2015

Vadose Zone Journal

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Core Ideas Water filled porosity (WFP) controlled N dynamics in the drainfields. Sand layer was hotspot for nitrification due to 0.07–0.32 WFP. Soil layer was hotspot for denitrification due to 0.55–0.91 WFP. Organic N was mobile in the vadose zone and leached below drainfields. Onsite wastewater treatment systems (OWTS), commonly known as septic systems, are increasingly recognized as a potential source of nitrogen in the shallow groundwater. Our objective was to investigate the effect of hydrological and biogeochemical factors in the vadose zone on the fate of effluent‐borne N in the drainfields of a drip‐dispersal OWTS. Three lysimeters (152.4 cm long, 91.4 cm wide, and 91.4 cm high) were constructed using pressure‐treated wood to mimic OWTS drainfields. Each lysimeter had three distinct layers of gravel–sand mixture, soil, and commercial sand. A drip tube, which was covered with commercial sand before planting St. Augustine grass (Stenotaphrum Trin.) on the top and sides of the lysimeters, dispersed 9 L of septic tank effluent (STE) per day on top of the stacked layers. Each lysimeter was instrumented with 10 multi‐probe sensors to determine the water content, electrical conductivity (EC), and temperature in the center and sides of sand and soil layers. Leachate samples were collected over 67 events, which consisted of one sample every 24 h for 15 d (n = 15) and weekly flow‐weighted composite samples (n = 52). In all events, the pH, EC, and chloride were lower in the leachate than STE. Daily multi‐probe data showed that EC was greater in the center than sides of the lysimeters due to more STE interaction. Sensor water content data were used to calculate water filled porosity (WFP), which was greater in the soil (0.55–0.9) than sand (0.07–0.32) due to the textural differences. Mean total N was 70 mg L−1 in the STE, which reduced to 27.4 mg L−1 in the leachate likely due to the denitrification in the soil layer. The dominance of NOx–N in the leachate (61%) as compared to STE (0.6%) was attributed to the nitrification in the sand layer. Higher proportion of organic N in the leachate (39%) than STE (16%) suggests that organic N was mobile in the vadose zone and leached below the drainfields. We conclude that hydrological and biogeochemical controls in the vadose zone play an important role in N transformations and transport of NOx–N and organic N below OWTS drainfields.

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Nitrogen Fate and Transport in a Conventional Onsite Wastewater Treatment System Installed in a Clay Soil: A Nitrogen Chain Model

Cited by 11 publications

References 19 publications

Modeling the Effects of Onsite Wastewater Treatment Systems on Nitrate Loads Using SWAT in an Urban Watershed of Metropolitan Atlanta

Modeling the Effects of Onsite Wastewater Treatment Systems on Nitrate Loads Using SWAT in an Urban Watershed of Metropolitan Atlanta

Simulated nitrate leaching in annually cover cropped and perennial living mulch corn production systems

Fate of Effluent‐Borne Nitrogen in the Mounded Drainfield of an Onsite Wastewater Treatment System

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