Progress 04/01/07 to 03/30/14
Outputs
Target Audience:Sceintific community,state and municipal government officials, extension service, homeowners Changes/Problems:I served on an expert panel in 2015 for EPA that was tasked with estimating what percentage of theN that went into OWTS was lost before it reached third-order or larger streams in the Chesapeake Bay watershed as part of the Bay TMDL. I used the data from our project to develop estimates for soil losses as a function of soil texturein all regions and for groundwater losses in the Piedmont region of the Bay. These results will be used in the Phase-6 version of the Bay models to estimate the contribution of OWTS to the Bay N. What opportunities for training and professional development has the project provided?We have trained 4 graduate students (1 MS, 3 PhDs) on this project How have the results been disseminated to communities of interest?The results have been communitcated to the scientific community through the journal articles and in conferences where we have made presentations and written papers. Within Georgia, the results have been presented in a number of meetings with state and municipal officials. We conducted a workshop for professionals working on OWTS in Georgia.We developed a video for homeowners. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
We used the HYDRUS-2D model to show that in a typical OWTS approximately 50% of the total nitrogen (N) in the system was lost (presumably to denitrification) within a depth of 1.5 m below the trench in a clay soil. We used our calibratedmodel to estimate N losses in the 11 other textural classes. The watershed scale work was not done in the Lake Allatoona watershed, but rather in the Ocmulgee watershed near Atlanta becasue we got a NIFA grant for this work. The grant focused on the effect of OWTS on stream flow, N, and bacteria under base flow conditions. We have shown that OWTS contribute N to streams when the OWTS density (number of systems per square km) is high. Bacteria with a human specific marker were identified on some sampling dates (winter high base flow). We are still working on the analysis of the effect on stream flow, but we expect to show that stream base flow increases with OWTS density.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Habteselassie, M., J.K. Bradshaw, and D.E. Radcliffe. 2013. Preliminary study on the effect of wastewater storage in septic tank on E. coli concentration. Water. 5:1141-1151.
- Type:
Journal Articles
Status:
Published
Year Published:
2014
Citation:
Oliver, C.W., D.E. Radcliffe, L.M. Risse, M. Habteselassie, R. Mukundan, and J. Jeong. 2014. Quantifying the contribution of on-site wastewater treatment systems to stream discharge using the SWAT model. J. Environ. Qual. 43:539-548.
- Type:
Journal Articles
Status:
Published
Year Published:
2014
Citation:
Oliver, C.W., L.M. Risse, D.E. Radcliffe, M. Habteselassie, and J. Clarke. 2014. Evaluating potential impacts of on-site wastewater treatment systems on the nitrogen load and baseflow in streams of watersheds in Metropolitan Atlanta, Georgia. Trans. ASABE. 57:1121-1128.
- Type:
Journal Articles
Status:
Published
Year Published:
2014
Citation:
Sowah, R., H. Zhang, D.E. Radcliffe, E. Bauske, and M. Habteselassie. 2014. Evaluating the influence of septic systems and watershed characteristics on stream fecal pollution in suburban watersheds in Georgia, USA. J. Applied Microbiology. 117:1500-1512.
- Type:
Journal Articles
Status:
Published
Year Published:
2015
Citation:
Radcliffe, D.E., D.K. Reid, K. Blomb�ck, C.H. Bolster, A.S. Collick, Z.M. Easton, W. Francesconi, D.R. Fuka, H. Johnsson, K. King, M. Larsbo, M.A. Youssef, A.S. Mulkey, N.O. Nelson, K. Persson, J.J. Ramirez-Avila, F. Schmieder, and D.R. Smith. Applicability of models to predict phosphorus losses in drained fields: A review. J. Environ. Qual. In press.
|
Progress 01/01/12 to 12/31/12
Outputs
OUTPUTS: In 2012 (the sixth year of our project), we completed work on both objectives. In regard to the first objective: modeling on-site wastewater systems (OWTSs), we submitted two articles to the Vadoze Zone Journal on the OWTS field experiment and these were accepted in March of 2013. In new work, we used the HYDRUS model developed in the field experiment on a clay soil to test the hydraulic performance and N treatment for all 12 textural classes using two years of weather data from the field experiment. We found that soil texture had a strong effect on OWTS performance. In terms of hydraulic performance, the design hydraulic loading rates of Radcliffe and West (2009) were adequate except for the sandy clay textural class in which the rate was too high and caused continuous ponding in the trench. Nitrogen assimilation varied widely among soils (from 1% in the sand class to 75% in the sandy clay class) due to the effect of water content on denitrification. Minimum lot sizes to protect groundwater ranged from 0.26 to 1.13 ha and were largest for medium-textured soils where denitrification and recharge were intermediate. In regard to the second objective on modeling watershed-scale effects, we developed a SWAT model for Big Haynes Creek in Gwinnett County, Georgia. The model was calibrated and validated using data from a USGS gage station. This watershed is 44 square km in area, 66% low-to-medium density urban landuse, with 4,011 OWTSs in 2011. Stream discharge was modeled with and without the presence of OWTSs in order to quantify their influence on water quantity. There was a 3.1% increase in total water yield at the watershed-scale and a 5.9% increase at the subbasin-scale. The percent change in water yield between simulations was the greatest in dry years implying that the influence of OWTSs on the water yield within the watershed is greatest under drought conditions. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Our results show that the method used in the Georgia OWTS manual to determine minimum lot sizes for OWTS may be overestimating recharge by assuming that it is 50% or rainfall. Our simulations showed that recharge varies from 13% in the sandy clay and silty clay classes to 44% in the sand class. As a result, the Georgia recommendations for minimum lot size underestimate the area required for all soil classes except the sandy clay and clay classes.
Publications
- Habteselassie, Mussie Y., Radcliffe, David E., Huang, Qingguo, Risse, Lawrence M., Mullen, Jeffrey D.. 2012. Watershed-scale Impacts of On-site Wastewater Treatment Systems on Water Quality and Quantity: Preliminary Results for Water Quality Indicators. Land Grant and Sea Grant National Water Conference. Portland, OR. May 2012.
- Radcliffe, David E., Clarke, John, Habteselassie, Mussie Y., Huang, Qingguo, Mullen, Jeffrey D., Risse, Lawrence M., Oliver, Chris. 2012 Watershed-scale effects of on-site wastewater treatment systems on water quality and quantity: Preliminary results for discharge and nitrogen. Land Grant and Sea Grant National Water Conference. Portland, OR. May 2012.
- Bradshaw, J. K., Radcliffe, D. E., Simunek, J., Wunsch, A., McCray, J. 2013. Nitrogen fate and transport in a conventional onsite wastewater treatement system installed in a clay soil: A nitrogen chain model. To appear in Vadose Zone Journal.
- Bradshaw, J. K., Radcliffe, D. E. 2013. Nitrogen fate and transport in a conventional onsite wastewater treatement system installed in a clay soil: Experimental results. To appear in Vadose Zone Journal.
- Habteselassie, Mussie Y., Radcliffe, David E., Risse, Lawrence M., Huang, Qingguo, Zhang, Hao. 2012. Evaluation of the impact of on-site wastewater treatment systems on water quality in urbanizing watersheds. Soil Science Society of America Annual Meetings. Cincinnati, OH. October 2012.
- Oliver, Chris, Radcliffe, David E., Risse, Lawrence M., Habteselassie, Mussie Y.Annual Meeting. 2012. The impact of onsite wastewater treatment systems on the nitrogen load and baseflow in urbaninzing watersheds of Metropolitan Atlanta, Georgia.. Soil Science Society of America Annual Meetings. Cincinnati, OH. October 22, 2012.
- Radcliffe, David E.. 2012. Soil texture effects on hydraulic performance and nitrogen treatment of on-site wastewater systems. Soil Science Society of America Annual Meeting. Cincinnati, OH. October 22, 2012.
|
Progress 01/01/11 to 12/31/11
Outputs
OUTPUTS: In 2011 (the fifth year of our project), most of our work was related to the first objective: modeling on-site wastewater systems (OWSs). The modeling work is based on a onsite wastewater treatment system (OWTS) field experiment in Griffin, GA. A nitrogen (N) chain model with water-content dependent first-order transformation rates for nitrification and denitrification was developed. The overall predicted soil pressure heads and solute concentrations were similar to data collected from the field experiment. The calibrated model made it possible to estimate water and solute fluxes in the drainfield and N losses from the OWTS. The estimated annual N loss from leaching at the lower boundary of the experimental drainfield was 2.01 kg yr-1. Scaled up to an OWTS size typical for GA and a zoning density of 5 homes ha-1, the N load to groundwater would be 30.9 kg ha-1 yr-1, which is comparable to agricultural production losses to groundwater. The model predicted 76% of the N removal in the system was from denitrification, whereas plant uptake and change in N storage accounted for <5% of the N loss. These estimates were specific to clay-textured soils and should be valuable to TMDL developers who need to predict load allocations for non-point sources in the Piedmont. In regard to the second objective, we received funding to model the effect of OWTS on water quantity and quality at the watershed scale in part of the metro Atlanta area. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
A recent review found that out of 83 studies of N in OWTS drainfields, most of the work had been done on sands with only 4 had been done on clay soils. Since the clay soils are likely to be wetter that the sands, N losses to dentrification could be greater in clays. Our results show that denitrifcation removed for over 70% of the N input to the OWTS. Most design standards assume that denitrification accounts for 50% or less. Despite the high loss to denitrification, the groundwater load we estimated with our model is substantial when home density is high. Our model estimates should be valuable to total maximum daily load (TMDL) developers who need to predict load allocations for non-point sources. These estimates were also specific to clay textured soils, which should be valuable for modeling N transport from OWTSs on a regional scale (i.e. Piedmont).
Publications
- Radcliffe, D. E., Bradshaw, J. K. (2011). A nitrogen chain model for on-site wastewater systems. Madison, WI: Soil Science Society of America. a-c-s.confex.com/crops/2011am/webprogram/Paper64915.html
- Bradshaw, J., Radcliffe, D. E. (2011). Nitrogen losses in a Piedmont onsite wastewater system. Madison, WI: Soil Science Society of America. a-c-s.confex.com/crops/2011am/webprogram/Paper66641.html
- Radcliffe, D. E., Bradshaw, J. K. (2011). A nitrogen model for onsite wastewater systems. April 11-13, 2011: Proceedings of the 2011 Georgia Water Resources Conference. www.gawrc.org/2011paper_pdfs/5.2.3Radcliffe.pdf
- Mckinley, R., Radcliffe, D. E., Mukundan, R. (2011). Correlating sub-basin sediment fingerprints with land use in the Southern Piedmont. April 11-13, 2011: Proceedings of the 2011 Georgia Water Resources Conference. www.gawrc.org/2011paper_pdfs/Poster7.1789McKinley.pdf
- Bradshaw, J. K., Radcliffe, D. E. (2011). Nitrogen dynamics in a Piedmont onsite wastewater treatment system. April 11-13, 2011: Proceedins of the 2011 Georgia Water Resources Confernce. www.gawrc.org/2011paper_pdfs/5.1.4Bradshaw.pdf
|
Progress 01/01/09 to 12/31/09
Outputs
OUTPUTS: In 2009 (the third year of our project), most of our work continued to be related to the first objective: modeling on-site wastewater systems (OWSs). The modeling work is based on an experiment in Griffin Georgia. At the site, we have installed a typical residential OWS with three 10-m long trenches. The soil surrounding the trenches is instrumented with water content sensors (TDR), automated and manual tensiometers, and suction samplers. Water level sensors are installed in the trenches. Wastewater is brought from the inlet to a nearby waste water treatment plant (with a service area that is almost entirely residential) twice a week and pumped into a storage tank. The storage tank feeds into a septic tank in three doses per day. From the septic tank, effluent flows to the trenches through a distribution box. We collect samples monthly from over 60 suction samplers. These samples are analyzed for total nitrogen (TN), ammonium (NH4), and nitrate (NO3). Sampling began in April 2009 and we have analyzed the samples through January 2010. In addition to the suction samplers, we collect samples from the septic tank outlet. Water level sensors indicate that water is ponding in the trenches and that the soil is very near saturation surrounding the trenches. Total N at the septic tank outlet has varied between 32 and 52 mg/L and NH4 at the outlet has varied between 16 and 45 mg/L. Nitrate concentrations at the septic tank outlet have been less than 0.2 mg/L. Nitrate concentrations in the soil were very low (< 2 mg/L) for the first couple of months, but have risen steadily since then. The highest concentration measured in the last sampling (Jan 2010) was 53 mg/L at a point 15 cm below the trench. On the same date, many samplers had NO3 concentrations in the 5-20 mg/L range. Some of these samplers were at depths 90 cm below the trench and displaced horizontally as much as 80 cm from the edge of the trench. In comparing the model predictions to the experimental data, the model predicts that almost all of the nitrogen will be converted to NO3 and then to N2 gas through denitrification before or shortly after it enters the soil. Our future work will focus on why the model seems to over-predict denitrification. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Current models for predicting N assimilation in soils with OWS are simple mass balance models that rely on an assumed rate of denitrification. A mechanistic model that accurately simulated nitrogen transformations would be an important contribution to estimating the impact that OWS have on stream and ground water quality.
Publications
- Radcliffe, D. E. 2009. Spreadsheet for converting saturated hydraulic conductivity to long term acceptance rate for on-site wastewater systems. Washington, DC: National Water Program USDA NIFA.
- Radcliffe, D. E., Bradshaw, K. 2009. Time-variable hydraulic potential surrounding an onsite wastewater drainfield. Abstract 55977. Pittsburgh, PA, November 1-5, 2009: Soil Science Society of America Annual Meeting.
- Radcliffe, D. E., Schoumans, O., Freer, J. 2009. Diffuse phosphorus models in the U.S. and Europe: Their usages scales and uncertainties. J. Environ. Qual. 38:1956-1967.
- Radcliffe, D. E., Lin, Z., Risse, L. M., Romeis, J. J., Jackson, C. R. 2009. Modeling phosphorus in the Lake Allatoona watershed using SWAT: I. Developing phosphorus parameter values. J. Environ. Qual. 38:111-120.
- Lin, Z. and D.E. Radcliffe. 2009. Modeling Phosphorus in the Lake Allatoona watershed using SWAT: II. Effect of landuse change. J. Environ. Qual. 38:121-129.
- Finch, S. D., Radcliffe, D. E., West, L. T. 2009. Modeling sidewall and bottom flow in on-site wastewater management systems. J. Hyd. Eng., 13:693-701.
- Radcliffe, D. E., West, L.T. 2009. Spreadsheet for converting saturated hydraulic conductivity to long-term acceptance rate for on-site wastewater systems. Soil Survey Horizons. 50:20-24.
- McCray, J., Lowe, K., Geza, M., Drewes, J., Roberts, J., Wunsch, A., Radcliffe, D. E., Amador, J., Atoyan, J., Boving, T., Kalen, D., Loomis, G. 2009. State of the Science: Review of Quantitative Tools to Determine Wastewater Soil Treatment Unit Performance. Water and Environmental Research Foundation. www.werf.org
- Radcliffe, D. E., West, L. T. 2009. Design hydraulic loading rates for on-site wastewater systems. Vadose Zone Journal. 8:64-74.
|
Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: In 2008 (the second year of our project), most of our work continued to be related to the first objective: modeling on-site wastewater systems (OWSs). We received funding from the Water Environment Foundation (WERF) for a project entitled "Development of quantitative tools to determine the expected performance of unit processes and wastewater soil treatment units". This project is in cooperation with the Colorado School of Mines and the University of Rhode Island. Our part of the project is to develop a HYDRUS model that will predict nitrogen and phosphorus losses to groundwater from a typical OWS. First, we wrote a literature review of nitrogen (N) and phosphorus (P) modeling as it might apply to OWSs. This will be posted on the WERF website. The review covered 61 N papers and 42 P papers. Some of the major conclusions regarding N were: 1) the biggest question in modeling N in OWSs is under what conditions and to what extent does denitrification occur; 2) several studies indicate that differences in soil texture, structure or drainage class are likely to affect denitrification; 3) a number of studies have used the HYDRUS model framework including a nitrogen model for two-dimensional simulations of a constructed wetland (CW2D), but no HYDRUS models of N assimilation in OWSs have been developed. We've concentrated on the development of a two-dimensional HYDRUS model that will adapt the CW2D equations to a conventional gravel OWS. We have developed a finite element mesh that will run simulations that include the gravel space within the model domain and include a biomat. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Our work is part of a national project to develop simple tools for predicting how effective OWSs in different soils will be in treating nutrients in wastewater. The data generated from our HYDRUS model will be used to develop these simple tools. The tools will guide state planners in developing regulations of housing density in areas where OWSs might contribute to groundwater pollution.
Publications
- Finch, S.D., D.E. Radcliffe, and L.T. West. 2008. Modeling trench sidewall and bottom flow in on-site wastewater systems. J. Hydrologic Eng. 13: 693-701.
|
Progress 01/01/07 to 12/31/07
Outputs
In 2007 (the first year of our project), most of our work was related to modeling on-site wastewater systems (objective 1). Design hydraulic loading rates are used in specifying the length of drainfield trench line required for onsite wastewater systems (OWSs). These requirements vary widely among states and local jurisdictions and are often based on limited empirical evidence. Our objective was to develop a method for estimating the design hydraulic loading rates based on soil and biomat hydraulic properties. We used a two-dimensional computer model (HYDRUS) to determine the steady flux through the trench bottom for the 12 USDA soil textural classes with five cm of wastewater ponded in the trench as an estimate of the performance under normal operating conditions. We used two sets of boundary conditions at the bottom of the soil profile: a deep water table and a shallow water table. We also tested how well a simple equation developed by Bouma and co-workers estimated
the bottom flux. To estimate the design hydraulic loading rate, we took 50% of the steady trench bottom flux as a safety factor. Despite the wide range in saturated hydraulic conductivities of the soil textural classes (8.18 to 642.98 cm/day), the steady flow through the bottom of the trench in these soils fell in a narrow range of 2.64 to 16.54 cm/day. With a modification to account for unsaturated flow within the biomat, the Bouma equation produced remarkably accurate estimates of trench bottom flux for all soil textural classes. Based on our estimates of design hydraulic loading rate, we divided the soil textural classes into four groups. Our results show that medium textured soils should have higher design hydraulic loading rates due to the importance of unsaturated flow in OWS hydraulic performance.
Impacts
Our work is showing that computer models can be used to develop guidelines for the required hydraulic loading of on-site wastewater systems based on soil and biomat hydraulic properties, instead of the conventional approach based on limited empirical evidence. This is a clear example of learning from models.
Publications
- Radcliffe, D.E., and L.T. West. 2007. Modeling long term acceptance rates for OWMSs. Proceedings 11th National Symposium on Individual and Small Community Sewage Systems, October 20-24, 2007, Warwick, RI.
- Lin, Z., D.E. Radcliffe, M.B. Beck, and L.M. Risse. 2007. Modeling phosphorus in the upper Etowah River basin: Identifying sources under uncertainty. Water Science and Technology. 56: 29-37.
|
|