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W. D. Robertson - One of the best experts on this subject based on the ideXlab platform.
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review of phosphorus attenuation in groundwater plumes from 24 Septic Systems
Science of The Total Environment, 2019Co-Authors: W. D. Robertson, Dale R Van Stempvoort, Sherry L. SchiffAbstract:Abstract This study reviews phosphorus (P) concentrations in groundwater plumes from 24 on-site wastewater treatment Systems (Septic Systems) in Ontario, Canada. Site investigations were undertaken over a 30-year period from 1988 to 2018 at locations throughout the province that encompass a variety of domestic wastewater types and geologic terrain. The review focuses on P behaviour in the drainfield sediments and in the proximal plume zones, within 10 m of the drainfields, where plume conditions were generally at steady state. At these sites, mean soluble reactive phosphorus (SRP) values in the Septic tank effluent ranged from 1.8 to 13.8 mg/L and averaged 8.4 mg/L. Phosphorus removal in the drainfields averaged 90% at sites where sediments were non calcareous (13 sites) and 66% at sites where sediments were calcareous (11 sites). Removal considering both the drainfields and proximal plume zones, averaged 97% at the non-calcareous sites and 69% at the calcareous sites, independent of the site age or loading rate. At 17 of the 24 sites, mean SRP concentrations in the proximal groundwater plumes (within 10 m) declined to ≤1 mg/L, which is a common treatment level for P at sewage treatment plants. Zones of P accumulation were present in almost all of the drainfields, where sand grains exhibited distinct secondary coatings containing P, demonstrating that mineral precipitation was likely the dominant cause of the P retention observed at these sites. This review confirms the often robust capacity for phosphorus removal in properly functioning Septic Systems. At the majority of these sites (17/24), P retention meets or exceeds removal that would normally be achieved during conventional sewage treatment. This challenges the necessity of avoiding Septic System use in favor of communal sewer Systems, when limiting phosphorus loading to nearby water courses is a principal or major concern.
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phosphorus and nitrogen loading to lake huron from Septic Systems at grand bend on
Journal of Great Lakes Research, 2019Co-Authors: Simon Baer, John Spoelstra, W. D. Robertson, Sherry L. SchiffAbstract:Abstract Groundwater nutrient loading to L. Huron was assessed along a 1.7 km section of beach at Grand Bend, ON, Canada, where Septic Systems are used for wastewater disposal. The artificial sweetener acesulfame (ACE) was detected in all groundwater samples (7–842 ng/L, n = 78), revealing that the entire surficial aquifer was impacted by Septic System wastewater. Nitrate concentrations (3.5 ± 1.4 mg/L, n = 78) were correlated with ACE (r2 = 0.54), indicating that Septic Systems contribute to nitrate loading in the aquifer. Chloride was also elevated (37 ± 11 mg/L, n = 78), but was not correlated with ACE (r2 = 0.008), indicating a non wastewater source was dominant, likely road salt. Soluble reactive phosphorus (SRP) values were low (5.3 ± 9.3 μg/L, n = 77) and were not correlated with ACE (r2 = 0.006). Sediment profiling below two of the Septic System drain-fields, showed that the sand grains had distinct secondary coatings containing P, indicating that mineral precipitation reactions played a role in limiting P concentrations present in the aquifer. Groundwater nutrient loading to the lake was estimated at 13,000 kg N/year from NO3− and 1.9 kg P/year from SRP. These amounts are insignificant compared to nutrient loading from a stream that drains an agricultural catchment and discharges to the lake at the north end of the study site (Parkhill Creek). This calls into question, in some cases, the rationale of decommissioning properly functioning Septic Systems as a mitigation measure for reducing nutrient loading to nearby water courses.
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degradation of sucralose in groundwater and implications for age dating contaminated groundwater
Water Research, 2016Co-Authors: W. D. Robertson, John Spoelstra, Dale R Van Stempvoort, S. J. Brown, Sherry L. SchiffAbstract:Abstract The artificial sweetener sucralose has been in use in Canada and the US since about 2000 and in the EU since 2003, and is now ubiquitous in sanitary wastewater in many parts of the world. It persists during sewage treatment and in surface water environments and as such, has been suggested as a powerful tracer of wastewater. In this study, longer-term persistence of sucralose was examined in groundwater by undertaking a series of three sampling snapshots of a well constrained wastewater plume in Canada (Long Point Septic System) over a 6-year period from 2008 to 2014. A shrinking sucralose plume in 2014, compared to earlier sampling, during this period when sucralose use was likely increasing, provides clear evidence of degradation. However, depletion of sucralose from a mean of 40 μg/L in the proximal plume zone, occurred at a relatively slow rate over a period of several months to several years. Furthermore, examination of Septic tank effluent and impacted groundwater at six other sites in Canada, revealed that sucralose was present in all samples of Septic tank effluent (6–98 μg/L, n = 32) and in all groundwater samples (0.7–77 μg/L, n = 64). Even though sucralose degradation is noted in the Long Point plume, its ubiquitous presence in the groundwater plumes at all seven sites implies a relatively slow rate of decay in many groundwater Septic plume environments. Thus, sucralose has the potential to be used as an indicator of ‘recent’ wastewater contamination. The presence of sucralose identifies groundwater that was recharged after 2000 in Canada and the US and after 2003 in the EU and many Asian countries.
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nitrate removal rates in a 15 year old permeable reactive barrier treating Septic System nitrate
Ground Water Monitoring and Remediation, 2008Co-Authors: W. D. Robertson, J L Vogan, P S LombardoAbstract:Permeable reactive barriers (PRBs) have gained popularity in recent years as a low-cost method for ground water remediation. However, their cost advantage usually requires that these barriers remain maintenance free for a number of years after installation. In this study, sediment cores were retrieved from a pilot-scale PRB consisting of a sand and wood particle (sawdust) mixture that has been in continuous operation for 15 years treating nitrate from a Septic System plume in southern Ontario (Long Point site). Reaction rates for the 15-year-old media were measured in dynamic flow column tests and were compared to rates measured in year 1 using the same reactive mixture. Nitrate removal rates in the 15-year-old media varied, as expected, with temperature in the range of 0.22 to 1.1 mg N/L/d at 6 � Ct o 10� C to 3.5 to 6.0 mg N/L/d at 20 � Ct o 22 � C. The latter rates remained within about 50% of the year 1 rates (10.2 6 2.7 mg N/L/d at 22 � C). Near the end of the year 15 column test, media particles >0.5 mm in diameter, containing most of the wood particles, were removed from the reactive media by sieving. Nitrate removal subsequently declined by about 80%, indicating that the wood particles were the principal energy source for denitrification. This example shows that some denitrifying PRBs can remain maintenance free and be adequately reactive for decades.
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fate of pharmaceutical and trace organic compounds in three Septic System plumes ontario canada
Environmental Science & Technology, 2008Co-Authors: Cherilyn Carrara, W. D. Robertson, Carol J Ptacek, David W Blowes, M C Moncur, Ed Sverko, Sean BackusAbstract:Three high volume Septic Systems in Ontario, Canada, were examined to assess the potential for onsite wastewatertreatment Systems to release pharmaceutical compounds to the environment and to evaluate the mobility of these compounds in receiving aquifers. Wastewater samples were collected from the Septic tanks, and groundwater samples were collected below and down gradient of the infiltration beds and analyzed for a suite of commonly used pharmaceutical and trace organic compounds. The Septic tank samples contained elevated concentrations of several pharmaceutical compounds. Ten of the 12 compounds analyzed were detected in groundwater at one or more sites at concentrations in the low ng L(-1) to low microg L(-1) range. Large differences among the sites were observed in both the number of detections and the concentrations of the pharmaceutical compounds. Of the compounds analyzed, ibuprofen, gemfibrozil, and naproxen were observed to be transported atthe highest concentrations and greatest distances from the infiltration source areas, particularly in anoxic zones of the plumes.
Sherry L. Schiff - One of the best experts on this subject based on the ideXlab platform.
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Septic Systems contribute artificial sweeteners to streams through groundwater
Journal of Hydrology X, 2020Co-Authors: John Spoelstra, Sherry L. Schiff, S. J. BrownAbstract:Abstract Artificial sweeteners are ubiquitous constituents of sanitary wastewater and are not completely attenuated by wastewater treatment processes. Consequently, artificial sweeteners are increasingly employed as a tool to detect wastewater and help evaluate its impact on aquatic environments. In rural areas, Septic Systems are known point sources of artificial sweeteners to groundwater, however the potential contribution of artificial sweeteners to streams via this pathway is unknown. We analyzed 294 samples from 173 stream sites in Southern Ontario, Canada, for acesulfame, saccharin, cyclamate, and sucralose, and found that 91% had one or more of these compounds present. The stream sites sampled did not have municipal wastewater treatment plants upstream and therefore Septic System effluent was the most likely source of the artificial sweeteners. Acesulfame, which is the most recalcitrant of the four artificial sweeteners, was by far the most ubiquitous in streams, with a 91% detection frequency, compared to 27, 8, and 3% for saccharin, cyclamate, and sucralose, respectively. Stream concentrations ranged from non-detectable to maximum values of 225, 380, 204, and 291 ng/L for acesulfame, saccharin, cyclamate, and sucralose, respectively. We calculated that water from Septic effluent contributed from
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review of phosphorus attenuation in groundwater plumes from 24 Septic Systems
Science of The Total Environment, 2019Co-Authors: W. D. Robertson, Dale R Van Stempvoort, Sherry L. SchiffAbstract:Abstract This study reviews phosphorus (P) concentrations in groundwater plumes from 24 on-site wastewater treatment Systems (Septic Systems) in Ontario, Canada. Site investigations were undertaken over a 30-year period from 1988 to 2018 at locations throughout the province that encompass a variety of domestic wastewater types and geologic terrain. The review focuses on P behaviour in the drainfield sediments and in the proximal plume zones, within 10 m of the drainfields, where plume conditions were generally at steady state. At these sites, mean soluble reactive phosphorus (SRP) values in the Septic tank effluent ranged from 1.8 to 13.8 mg/L and averaged 8.4 mg/L. Phosphorus removal in the drainfields averaged 90% at sites where sediments were non calcareous (13 sites) and 66% at sites where sediments were calcareous (11 sites). Removal considering both the drainfields and proximal plume zones, averaged 97% at the non-calcareous sites and 69% at the calcareous sites, independent of the site age or loading rate. At 17 of the 24 sites, mean SRP concentrations in the proximal groundwater plumes (within 10 m) declined to ≤1 mg/L, which is a common treatment level for P at sewage treatment plants. Zones of P accumulation were present in almost all of the drainfields, where sand grains exhibited distinct secondary coatings containing P, demonstrating that mineral precipitation was likely the dominant cause of the P retention observed at these sites. This review confirms the often robust capacity for phosphorus removal in properly functioning Septic Systems. At the majority of these sites (17/24), P retention meets or exceeds removal that would normally be achieved during conventional sewage treatment. This challenges the necessity of avoiding Septic System use in favor of communal sewer Systems, when limiting phosphorus loading to nearby water courses is a principal or major concern.
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phosphorus and nitrogen loading to lake huron from Septic Systems at grand bend on
Journal of Great Lakes Research, 2019Co-Authors: Simon Baer, John Spoelstra, W. D. Robertson, Sherry L. SchiffAbstract:Abstract Groundwater nutrient loading to L. Huron was assessed along a 1.7 km section of beach at Grand Bend, ON, Canada, where Septic Systems are used for wastewater disposal. The artificial sweetener acesulfame (ACE) was detected in all groundwater samples (7–842 ng/L, n = 78), revealing that the entire surficial aquifer was impacted by Septic System wastewater. Nitrate concentrations (3.5 ± 1.4 mg/L, n = 78) were correlated with ACE (r2 = 0.54), indicating that Septic Systems contribute to nitrate loading in the aquifer. Chloride was also elevated (37 ± 11 mg/L, n = 78), but was not correlated with ACE (r2 = 0.008), indicating a non wastewater source was dominant, likely road salt. Soluble reactive phosphorus (SRP) values were low (5.3 ± 9.3 μg/L, n = 77) and were not correlated with ACE (r2 = 0.006). Sediment profiling below two of the Septic System drain-fields, showed that the sand grains had distinct secondary coatings containing P, indicating that mineral precipitation reactions played a role in limiting P concentrations present in the aquifer. Groundwater nutrient loading to the lake was estimated at 13,000 kg N/year from NO3− and 1.9 kg P/year from SRP. These amounts are insignificant compared to nutrient loading from a stream that drains an agricultural catchment and discharges to the lake at the north end of the study site (Parkhill Creek). This calls into question, in some cases, the rationale of decommissioning properly functioning Septic Systems as a mitigation measure for reducing nutrient loading to nearby water courses.
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degradation of sucralose in groundwater and implications for age dating contaminated groundwater
Water Research, 2016Co-Authors: W. D. Robertson, John Spoelstra, Dale R Van Stempvoort, S. J. Brown, Sherry L. SchiffAbstract:Abstract The artificial sweetener sucralose has been in use in Canada and the US since about 2000 and in the EU since 2003, and is now ubiquitous in sanitary wastewater in many parts of the world. It persists during sewage treatment and in surface water environments and as such, has been suggested as a powerful tracer of wastewater. In this study, longer-term persistence of sucralose was examined in groundwater by undertaking a series of three sampling snapshots of a well constrained wastewater plume in Canada (Long Point Septic System) over a 6-year period from 2008 to 2014. A shrinking sucralose plume in 2014, compared to earlier sampling, during this period when sucralose use was likely increasing, provides clear evidence of degradation. However, depletion of sucralose from a mean of 40 μg/L in the proximal plume zone, occurred at a relatively slow rate over a period of several months to several years. Furthermore, examination of Septic tank effluent and impacted groundwater at six other sites in Canada, revealed that sucralose was present in all samples of Septic tank effluent (6–98 μg/L, n = 32) and in all groundwater samples (0.7–77 μg/L, n = 64). Even though sucralose degradation is noted in the Long Point plume, its ubiquitous presence in the groundwater plumes at all seven sites implies a relatively slow rate of decay in many groundwater Septic plume environments. Thus, sucralose has the potential to be used as an indicator of ‘recent’ wastewater contamination. The presence of sucralose identifies groundwater that was recharged after 2000 in Canada and the US and after 2003 in the EU and many Asian countries.
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Persistence of artificial sweeteners in a 15-year-old Septic System plume
Journal of Hydrology, 2013Co-Authors: William D. Robertson, John Spoelstra, Dale R Van Stempvoort, S. J. Brown, D. K. Solomon, J. Homewood, Sherry L. SchiffAbstract:Summary Groundwater contamination from constituents such as NO 3 - , often occurs where multiple sources are present making source identification difficult. This study examines a suite of major ions and trace organic constituents within a well defined Septic System plume in southern Ontario, Canada (Long Point site) for their potential use as wastewater tracers. The Septic System has been operating for 20 years servicing a large, seasonal-use campground and tritium/helium age dating indicates that the 200 m long monitored section of the plume is about 15 years old. Four parameters are elevated along the entire length of the plume as follows; the mean electrical conductivity value (EC) in the distal plume zone is 926 μS/cm which is 74% of the mean value below the tile bed, Na + (14.7 mg/L) is 43%, an artificial sweetener, acesulfame (12.1 μg/L) is 23% and Cl − (71.5 mg/L) is 137%. EC and Cl − appear to be affected by dispersive dilution with overlying background groundwater that has lower EC but has locally higher Cl − as result of the use of a dust suppressant (CaCl 2 ) in the campground. Na + , in addition to advective dilution, could be depleted by weak adsorption. Acesulfame, in addition to the above processes could be influenced by increasing consumer use in recent years. Nonetheless, both Na + and acesulfame remain elevated throughout the plume by factors of more than 100 and 1000 respectively compared to background levels, and are strong indicators of wastewater impact at this site. EC and Cl − are less useful because their contrast with background values is much less (EC) or because other sources are present (Cl − ). Nutrients ( NO 3 - , NH 4 + , PO 4 3 - , K + ) and pathogens ( Escherichia coli ) do not persist in the distal plume zone and are less useful as wastewater indicators here. The artificial sweetener, acesulfame, has persisted at high concentrations in the Long Point plume for at least 15 years (and this timing agrees with tritium/helium-3 dating) and this compound likely occurs at uniquely high concentrations in domestic wastewater. As such, it holds considerable promise as a powerful new tracer of wastewater impact in groundwater.
John A Cherry - One of the best experts on this subject based on the ideXlab platform.
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impacts on a sand aquifer from an old Septic System nitrate and phosphate
Ground Water, 1996Co-Authors: J. Harman, W. D. Robertson, John A Cherry, Lucio ZaniniAbstract:Four hundred ground-water sampling points were used to delineate a plume in an unconfined sand aquifer at a 44 year old Septic System servicing a school in Ontario, Canada. A bromide tracer test indicated a residence time of one to two weeks for sewage effluent in the 1.6 meter unsaturated zone beneath the tile bed. This is sufficient time for the oxidation of all nitrogen to nitrate to be complete and for the content of dissolved organic carbon to decrease from about 19 mg/l in the Septic tank to about 1 mg/l at the water table. The 15m wide plume core emanates more than 110 meters downgradient of the tile bed, has detectable dissolved oxygen, high nitrate (20–120 mg/l as N), chloride (42–209 mg/l), sodium (34–101 mg/l), calcium (120–249 mg/l), and above background sulphate, and potassium. Ground-water flow velocity at this site is rapid (100 m/yr); thus the mapped extent of the plume (110 m) represents about one year effluent loading. Phosphate (PO43-) concentrations at the water table (∼ 1–2 mg/l as P) appear to have reached steady state at values significantly lower than that of the effluent (9 mg/l as P). Steady-state concentrations suggest that mineral precipitation reactions control attenuation in the unsaturated zone. A comparison of phosphate sorbed (74 mg/kg) and total P in the soil (1000 mg/kg) suggests that precipitation is a more important process in the unsaturated zone than is sorption. PO43- levels in the plume, however, remain elevated (0.3–1.8 mg/l as P) relative to background levels in ground water (<0.01 mg/l as P) up to 75 meters away from the tile bed. This migration distance of PO43- in ground water is greater than that observed at other younger Septic System sites. The extent of the plume at this site suggests that long-term PO43- migration in the ground-water zone may be controlled by adsorption processes that allow slow but progressive advancement of PO43-.
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biogeochemical evolution of domestic waste water in Septic Systems 1 conceptual model
Ground Water, 1994Co-Authors: Sheryl R Wilhelm, Sherry L. Schiff, John A CherryAbstract:This paper presents a conceptual model, developed by synthesizing the results of many researchers, which describes the geochemical evolution of domestic waste water in conventional on-site Septic Systems as the result of the interactions of a few major constituents. As described by the model, the evolution of waste water is driven by the microbially catalyzed redox reactions involving organic C and N in waste water and occurs in as many as three different redox zones. Anaerobic digestion of organic matter and production of CO2, CH4, and NH4+ predominate in the first zone, which consists mainly of the Septic tank. In the second zone, gaseous diffusion through the unsaturated sediments of the drain field supplies O2 for aerobic oxidation of organic C and NH4+ and a consequent decrease in waste-water alkalinity. The NO3− formed by NH4+ oxidation in this zone is the primary adverse impact of Septic Systems at most sites and is generally an unavoidable consequence of the proper functioning of conventional Septic Systems. If adequate O2 is not available in the drain field, aerobic digestion is incomplete, and the accumulation of organic matter may cause Septic-System failure. In the third redox zone, NO3 is reduced to N2 by the anaerobic process of denitrification. However, this setting is rarely found below Septic Systems due to a lack of labile organic C in the natural setting. Consideration of the changing redox and pH conditions in each zone aids our understanding of the fate of other constituents in Septic Systems.
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stable isotopes of oxygen and nitrogen in source identification of nitrate from Septic Systems
Ground Water, 1993Co-Authors: Ramon Aravena, M. L. Evans, John A CherryAbstract:Stable isotopes, 15N and 18O, have been used as tracers to differentiate a contaminant nitrate plume emanating from a single domestic Septic System, in a ground-water System characterized by high and similar nitrate content outside and inside of the contaminant plume. A good delineation of the nitrate plume of Septic origin was obtained using 15 N analysis in nitrate. The 15N content ofthe nonplunie nitrate is in agreement with the sources of nitrate: solid cattle manure, synthetic fertilizer (NH4-NO3), and soil organic nitrogen, at the study site. 18O analysis in nitrate did not provide enough isotopic contrast to permit separation of nitrate derived from the Septic System and that in the surrounding ground water, derived from agricultural fertilizer sources. 18O data indicated that nitrification of ammonium is the main process responsible for formation of nitrate at the study site. 18O in ground water clearly delineated the ground-water plume associated with the Septic System and suggest that this tracer should be considered in studies related with contaminant plumes of different origin.
Sheryl R Wilhelm - One of the best experts on this subject based on the ideXlab platform.
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biogeochemical evolution of domestic waste water in Septic Systems 2 application of conceptual model in sandy aquifers
Ground Water, 1996Co-Authors: Sheryl R Wilhelm, Sherry L. Schiff, W. D. RobertsonAbstract:Aqueous geochemical data from unconfined sand aquifers beneath two operating domestic Septic Systems are used to illustrate and evaluate a conceptual model of Septic-System geochemistry. This model emphasizes the changing redox and alkalinity conditions in the Septic System and the subsurface. The Septic-tank effluents flow as distinct plumes downward through the unsaturated zones and then primarily laterally in the ground-water zones. The composition of the effluent was measured at several points in each System. At each site, the Septic-tank effluent underwent aerobic oxidation in the unsaturated zone, which caused conversion of NH4+ to NO3−, organic C to CO2 and organic S to SCh42-. At the first site, calcium carbonate dissolution in the unsaturated zone buffered the acidity released by the redox reactions. In contrast, the second System was poorly buffered and the pH dropped from 6.7 to 4.9 as aerobic oxidation occurred. Below the water table a small amount of aerobic oxidation occurred at each site. Nitrate-N concentrations in the cores of both plumes were above 25 mg/1 as the plumes traveled from the Septic Systems. At the second site, the ground-water plume discharges to a river at the edge of the property. As the effluent flowed through the organic C-rich sediments of the river bed, NO3− disappeared and alkalinity increased, presumably due to denitrification. Differences in sediment composition at the two sites also led to different behaviors of Fe, Al, and possibly PO43-. The conceptual model offers an organized approach to interpreting the major geochemical trends observed in the two Systems, which are determined mostly by the well-aerated unsaturated zones below the drain fields and the amount of buffering material present in the sediments.
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biogeochemical evolution of domestic waste water in Septic Systems 1 conceptual model
Ground Water, 1994Co-Authors: Sheryl R Wilhelm, Sherry L. Schiff, John A CherryAbstract:This paper presents a conceptual model, developed by synthesizing the results of many researchers, which describes the geochemical evolution of domestic waste water in conventional on-site Septic Systems as the result of the interactions of a few major constituents. As described by the model, the evolution of waste water is driven by the microbially catalyzed redox reactions involving organic C and N in waste water and occurs in as many as three different redox zones. Anaerobic digestion of organic matter and production of CO2, CH4, and NH4+ predominate in the first zone, which consists mainly of the Septic tank. In the second zone, gaseous diffusion through the unsaturated sediments of the drain field supplies O2 for aerobic oxidation of organic C and NH4+ and a consequent decrease in waste-water alkalinity. The NO3− formed by NH4+ oxidation in this zone is the primary adverse impact of Septic Systems at most sites and is generally an unavoidable consequence of the proper functioning of conventional Septic Systems. If adequate O2 is not available in the drain field, aerobic digestion is incomplete, and the accumulation of organic matter may cause Septic-System failure. In the third redox zone, NO3 is reduced to N2 by the anaerobic process of denitrification. However, this setting is rarely found below Septic Systems due to a lack of labile organic C in the natural setting. Consideration of the changing redox and pH conditions in each zone aids our understanding of the fate of other constituents in Septic Systems.
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chemical fate and transport in a domestic Septic System unsaturated and saturated zone geochemistry
Environmental Toxicology and Chemistry, 1994Co-Authors: Sheryl R Wilhelm, Sherry L. Schiff, W. D. RobertsonAbstract:Monitoring the Septic System at a single family home provides quantitative information on geochemical evolution of Septic tank effluent along its travel path In both the unsaturated and saturated (groundwater) zones, microbiological and chemical reactions occur that bring the effluent closer to equilibrium with the subsurface conditions In the unsaturated zone, 90% of the DOC is removed from the effluent, mostly by aerobic oxidation, and NH+4 in the effluent is almost completely ox ldized to NO−3 As these reactions occur in the tile field, the oxygen content of the soil gas is partially depleted Calcite dissolution from the soils in the unsaturated zone buffers the acidity of the oxidation reactions and increases Ca2+ concentrations In the saturated zone, organic carbon oxidation in the effluent plume apparently decreases dissolved oxygen concentrations to <10 mg/L Potassium is retarded relative to other cations, and dissolved PO43 from the effluent is detectable in the ground water directly beneath the tile field but appears to be advancing very slowly, if at all, within the plume In addition NO3− concentrations remain above drinking-water standards (10 mg/L NO3 N) in the groundwater plume
Drew C. Mcavoy - One of the best experts on this subject based on the ideXlab platform.
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modeling the fate and transport of household chemicals in Septic Systems
Ground Water, 1998Co-Authors: Drew C. Mcavoy, James Szydlik, Jerald L SchnoorAbstract:A mathematical model was developed for the purpose of predicting the fate and transport of down-the-drain household chemicals in Septic Systems. The model was tested with field data collected from a typical Septic System located near Cambridge, Ontario, Canada. Model simulations were in good agreement with field data for the laundry detergent builders tartrate monosuccinate (TMS) and tartrate dissuccinate (TDS). The model was also independently verified with phosphate data collected from the study site. A sensitivity analysis showed little change in model predictions when the distribution coefficient and biodegradation rate constants were varied by 10%. Results from this study support that this model is satisfactory as a screening level tool for predicting the fate and transport of household chemicals in Septic Systems.
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chemical fate and transport in a domestic Septic System sorption and transport of anionic and cationic surfactants
Environmental Toxicology and Chemistry, 1994Co-Authors: Drew C. Mcavoy, C E White, B L Moore, Robert A RapaportAbstract:The sorption and transport of linear alkylbenzene sulfonate (LAS) and dialkyl quaternary ammonium compounds [ditallow dimethyl ammonium chloride (DTDMAC) and distearyl dimethyl ammonium chloride (DSDMAC)] were determined within the upper soil horizons and in the aquifer below a Septic tank tile field at a study site in Ontario. Sorption of LAS was greatest immediately below the tile field (Kd = 17 L/kg) within the upper unsaturated soil horizons and lowest in the aquifer (Kd = 1 L/kg). LAS sorption appeared to be controlled by a hydrophobic mechanism and was positively correlated with the organic carbon (r = 0.9) and the clay content (r = 0.9) in the subsurface environment. The sorption of DTDMAC/DSDMAC (Kd = 25-62 L/kg) was an order of magnitude higher than LAS but showed no trend throughout the subsurface environment. The retention of DTDMAC/DSDMAC was believed to be by ion exchange within the clay interlayer basal spaces. Samples collected from the field showed concentrations of DTDMAC to range from approximately 60 mg/kg in the tile field gravel to <2 mg/kg within 10 cm of soil below the tile field gravel. Concentrations of LAS were approximately 20 mg/kg in the tile field gravel and diminished to < 1 mg/kg within 5 cm of soil below the tile field gravel. Soil solution and aquifer concentrations of LAS were always <50 μg/L and usually below the detection limit of 10 μg/L in the aquifer. Concentrations of DTDMAC in the aquifer were below the limit of detection (4 μg/L). Mathematical calculations illustrated the importance of biodegradation and sorption as removal mechanisms of these materials in subsurface environments.
