Seasonal and diel variation in greenhouse gas emissions from septic system leach fields

Truhlar, Allison M.; Ortega, K. L.; Walter, M. Todd

doi:10.1007/s13762-019-02314-6

Cited by 11 publications

(19 citation statements)

References 22 publications

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“…Fluxes are, thus, expected to be highly variable on timescales of minutes to hours. This corroborates the previous findings that continuous or semi-continuous measurements are much more likely to detect periods of high fluxes (Somlai-Haase et al, 2017;Somlai et al, 2019;Truhlar et al, 2019). Vent flux values obtained from discrete measurements are, thus, challenging to compare between sites.…”

Section: Fluxes From the Ventssupporting

confidence: 90%

“…The weaker correlation between transitional soil moisture conditions compared to CO 2 fluxes suggests that CH 4 fluxes are more susceptible to short-term changes and immediate soil conditions, which is in line with observations by Fernández-Baca et al (2020), who found both STU and control soils to be either weak sinks or weak sources of CH 4 , except for periods of changing soil moisture conditions where they became net sources over the first 30 min following a simulated rain event. Truhlar et al (2016) also observed increasing soil CH 4 fluxes with increasing VWC, attributing it to the fact that with the methanotrophs are aerobic bacteria, whereas methanogens are anaerobic. This also aligns with more general findings of higher CH 4 emissions and uptake rates under changing soil moisture conditions, as well as with increasing temperature (Swenson et al, 2019;Le Mer and Roger, 2001).…”

Section: Environmental Drivers Of Ghg Fluxesmentioning

confidence: 82%

“…5). Truhlar et al (2016) andFernández-Baca et al (2020) found the STU to be net producers of N 2 O immediately after rain events; a similar trend was observed over trenches receiving PE where 60 % of N 2 O emission events were recorded after rainfall events within the preceding 3 h. Studies in other land use scenarios and soil columns have also found positive correlations between N 2 O emissions and soil moisture (Ambus and Christensen, 1995;Anderson et al, 2019), whereby maybe the rapidly changing soil moisture and redox conditions in the soils disrupt the balance of the microbial soil community, leading to periods of partial dentification.…”

Section: Environmental Drivers Of Ghg Fluxesmentioning

confidence: 99%

“…Most research on GHG emissions from wastewater to date has been carried out on centralised, large-scale treatment systems (Cakir and Stenstrom, 2005;Czepiel et al, 1993;Johansson et al, 2004;Yver Kwok et al, 2015;Masuda et al, 2015;Yoshida et al, 2014). Few studies, however, have directly measured GHG emissions from decentralised and/or on-site wastewater treatment systems (Diaz-Valbuena et al, 2011;Huynh et al" 2021;Somlai-Haase et al, 2017;Somlai et al, 2019;Truhlar et al, 2016;Wigginton et al, 2020), despite an estimated 20 % of the population relying on on-site wastewater treatment in the European Economic Area and the United States (EEA, 2013;US EPA, 2016). The proportion of these systems is significantly higher in low-and middle-income countries in comparison to the global average, reckoned to provide improved sanitation for up to 64 % of such countries' populations (Blackett et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

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Assessing the spatial and temporal variability of greenhouse gas emissions from different configurations of on-site wastewater treatment system using discrete and continuous gas flux measurement

2022

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Abstract. Global emissions linked to wastewater treatment are estimated to account for up to 1.5 % of total greenhouse gas (GHG) emissions globally. However, few studies have measured GHG emissions from domestic on-site treatment systems (DWWTSs) directly. In this study, two DWWTSs were monitored for 446 d and > 42 000 gas flux measurements were conducted using both discrete spot measurements and continuous flux chamber deployments. The observed GHG fluxes from biological activity in the soil and water phase were found to be highly spatially and temporally variable and correlated to environmental factors, water usage patterns and system design. In total, the results show that a septic tank discharging effluent into a well-designed soil treatment unit is estimated to emit a net 9.99 kg-CO2eq.cap-1yr-1, with approximately 63 %, 27 % and 10 % of the total CO2-equivalent net emissions in the form of CO2, CH4 and N2O, respectively. Emissions from the septic tank surface contributed over 50 % of total emissions and tended to be strongly underestimated by one-off discrete measurements, especially when episodic ebullitive events are to be considered. Fluxes from the soil treatment unit (STU) stemmed from both the soil surface and the vent system. Soil fluxes were mostly influenced by temperature but peaked regularly under conditions of rapidly changing soil water content. Vent fluxes were mostly governed by effluent, quality and a low number of high-emission events were responsible for the majority of total observed vent emissions. Owing to the strong overall spatial and temporal heterogeneity of observed fluxes from DWWTSs across all modules, future studies should focus on continuous deployments of a number of flux chambers over discrete measurements to accurately assess GHG emissions from on-site systems. This study also provided insights into managing GHG emissions from DWWTSs by different system configuration design, as well as indicating that the current IPCC emission factors for CH4 and N2O significantly overestimate emissions for on-site wastewater treatment systems.

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Section: Fluxes From the Ventssupporting

confidence: 90%

Section: Environmental Drivers Of Ghg Fluxesmentioning

confidence: 82%

Section: Environmental Drivers Of Ghg Fluxesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Assessing the spatial and temporal variability of greenhouse gas emissions from different configurations of on-site wastewater treatment system using discrete and continuous gas flux measurement

2022

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“…Actual processes within the drain field are far more complicated than those summarized in CW2D. In recent years greenhouse gas (GHG) emissions from wastewater application drain fields have received attention ( Somlai et al., 2019 ; Truhlar et al., 2019 ). Although not directly measured during the experiment nor included in the CW2D structure, GHG emission potentials (e.g.…”

Section: Resultsmentioning

confidence: 99%

Numerical assessment of a soil moisture controlled wastewater SDI disposal system in Alabama Black Belt Prairie

Dougherty

Chen

2021

Chemosphere

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To promote the environmental sustainability of rural sanitation, a soil moisture controlled wastewater subsurface drip irrigation (SDI) dispersal system was field tested in the Black Belt Prairie of Alabama, USA. The soil moisture control strategy was designed to regulate wastewater disposal timing according to drain field conditions to prevent hydraulic overloading and corresponding environmental hazard. CW2D/HYDRUS simulation modeling was utilized to explore difficult-to-measure aspects of system performance. While the control system successfully adapted hydraulic loading rate to changing drain field conditions, saturated field conditions during the dormant season presented practical application challenges. The paired field experiment and simulation model demonstrate that soil biofilm growth was stimulated in the vicinity of drip emitters. Although biofilm growth is critical in maintaining adequate COD and removal efficiencies, the efficient removal of biodegradable COD itself by soil biofilm limits denitrification of formed . Furthermore, stimulated soil biofilm growth can create soil clogging around drip emitters, which was discerned in the field experiment along with salt accumulation, both of which were verified by simulation. Comparable modeling of system performance in sand and clay media demonstrate that the placement of soil moisture sensors within the drain field can have pronounced impacts on system hydraulic performance, depending on the soil permeability. Overall, the soil moisture control strategy tested is shown as a viable supplemental technology to promote the environmental sustainability of rural sanitation systems.

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Laboratory-Scale Evaluation of the Effects of Water-Filled Pore Space on Emissions of CO2, CH4, N2O, and N2 from Soil-Based Wastewater Treatment

Anderson

Cooper

Amador

2019

Water Air Soil Pollut

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Seasonal and diel variation in greenhouse gas emissions from septic system leach fields

Cited by 11 publications

References 22 publications

Assessing the spatial and temporal variability of greenhouse gas emissions from different configurations of on-site wastewater treatment system using discrete and continuous gas flux measurement

Assessing the spatial and temporal variability of greenhouse gas emissions from different configurations of on-site wastewater treatment system using discrete and continuous gas flux measurement

Numerical assessment of a soil moisture controlled wastewater SDI disposal system in Alabama Black Belt Prairie

Laboratory-Scale Evaluation of the Effects of Water-Filled Pore Space on Emissions of CO2, CH4, N2O, and N2 from Soil-Based Wastewater Treatment

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