Papers & ReportsHome and Personal Care Products, Water/Wastewater Assessments2017
Use of Prospective and retrospective risk assessment methods that simplify chemical mixtures associated with treated domestic wastewater discharges
A framework is presented that is intended to facilitate the evaluation of potential aquatic ecological risks resulting from discharges of down‐the‐drain chemicals. A scenario is presented using representatives of many of the types of chemicals that are treated domestically. Predicted environmental chemical concentrations are based on reported loading rates and routine removal rates for 3 types of treatment: trickling filter, activated sludge secondary treatment, and activated sludge plus advanced oxidation process as well as instream effluent dilution. In tier I, predicted effluent concentrations were compared with the lowest predicted‐no‐effect concentration (PNEC) obtained from the literature using safety factors as needed. A cumulative risk characterization ratio (cumRCR) < 1.0 indicates that risk is unlikely and no further action is needed. Otherwise, a tier 2 assessment is used, in which PNECs are based on trophic level. If tier 2 indicates a possible risk, then a retrospective assessment is recommended. In tier 1, the cumRCR was > 1.0 for all 3 treatment types in our scenario, even though no chemical exceeded a hazard quotient of 1.0 in activated sludge or advanced oxidation process. In tier 2, activated sludge yielded a lower cumRCR than trickling filter because of higher removal rates, and the cumRCR in the advanced oxidation process was << 1.0. Based on the maximum cumulative risk ratio (MCR), more than one‐third of the predicted risk was accounted for by one chemical, and at least 90% was accounted for by 3 chemicals, indicating that few chemicals influenced the mixture risk in our scenario. We show how a retrospective assessment can test whether certain chemicals hypothesized as potential drivers in the prospective assessment could have, or are having, deleterious effects on aquatic life.
Diamond, J., Altenburger, R., Coors, A., Dyer, S.D., Focazio, M., Kidd, K., Koelmans, A.A., Leung, K.M.Y., Servos, M.R., Snape, J., Tolls, J., Zhang, X. (2017), Use of prospective and retrospective risk assessment methods that simplify chemical mixtures associated with treated domestic wastewater discharges. Environ Toxicol Chem. 37: 690-702. doi.org/10.1002/etc.4013
Papers & ReportsHome and Personal Care Products, Human Pharmaceuticals, Water/Wastewater Assessments2015
A framework for screening sites at risk from contaminants of emerging concern
Trace levels of a variety of currently unregulated organic chemicals have been detected in treated wastewater effluents and surface waters that receive treated effluents. Many of these chemicals of emerging concern (CECs) originate from pharmaceuticals and personal care products that are used widely and that frequently are transported “down the drain” to a wastewater treatment plant (WWTP). Actual effects of CECs on aquatic life have been difficult to document, although biological effects consistent with effects of some CECs have been noted. There is a critical need to find appropriate ways to screen wastewater sites that have the greatest potential of CEC risk to biota. Building on the work of several researchers, the authors present a screening framework, as well as examples based on the framework, designed to identify high‐risk versus lower‐risk sites that are influenced by WWTP effluent. It is hoped that this framework can help researchers, utilities, and the larger water resource community focus efforts toward improving CEC risk determinations and management of these risks.
Diamond, J., Munkittrick, K., Kapo, K.E., Flippin, J. (2015), A framework for screening sites at risk from contaminants of emerging concern. Environ Toxicol Chem. 34: 2671-2681. doi:10.1002/etc.3177
PresentationsHome and Personal Care Products2018
Estimating environmental emissions and aquatic fate of sludge-bound CECs using spatial modeling and US datasets
In the US, 50% of the sludge produced during wastewater treatment is recycled to land (www.epa.gov/biosolids). Some chemicals in consumer products may be highly removed during the wastewater treatment process due to sorption and binding to organic matter, ending up in sludge solids where it has the potential to be applied to land surfaces, subject to erosion or runoff processes potentially entering nearby surface waters. However, biosolids mass applied to land is not evenly distributed across the US landscape due to variable population density, local sludge management practices, and availability of land application sites. We have developed a proof-of-concept model to aide in the prospective assessment of CECs contained in WWTP sludge applied to land. This spatially-explicit, national model is based on publicly available datasets, combined with a spatial-hydrologic framework containing geographically variable emissions linked to a river network allowing for environmental transport via surface water. The hydrologic framework is based on a set of basins and rivers (www.hydrosheds.org) linked to emission characteristics for over 77,000 sub-basins. Emission characteristics are derived from facility data in the USEPA Clean Watersheds Needs Survey (www.epa.gov/cwns) to estimate consumer product usage linked to wastewater treatment, and spatially-variable data on biosolid applications. The USDA Cropland Data Layer (www.nass.usda.gov) provides potential land application sites, from which proximity to surface water plays a role in the potential for CECs to transport from land to freshwater (using a meta-model estimated from pesticide assessment models). Concentrations of CECs are routed through the river network based on local river attributes (e.g., flow) combined with assumptions about chemical fate in the aquatic environment. Results of various simulations show the spatial patterns of biosolids applications, potential to enter surface water, and estimated freshwater concentrations of an ingredient in a hypothetical consumer product. Implications of altering model assumptions are discussed. While the presented material is a simulated example of the environmental emission and fate of a consumer product ingredient, it represents a viable approach to assessing whether this pathway via land applied biosolids may be of concern for consumer product chemicals, and ultimately helping to inform environmental policy on this subject.
Christopher Holmes, Joshua Amos, Amy Ritter, and Marty Williams (Waterborne Environmental). Estimating environmental emissions and aquatic fate of sludge-bound CECs using spatial modeling and US datasets. Platform SETAC 2018. Sacramento, CA.
PostersHome and Personal Care Products2017
A Framework for Dynamic Estimation of Aquatic Environmental Concentrations of Microplastics Via WWTP Discharge
Down-the-drain exposure models provide a valuable screening-level tool for estimating environmental exposure to substances which are treated and discharged at municipal wastewater treatment plants (WWTPs). Microplastics enter WWTPs from a variety of sources. As such, exposure models traditionally used for chemicals may also be utilized for particle emissions into the environment from WWTP discharge. These models often account for removal in WWTP as well as in-river decay processes. However, in light of incomplete and changing knowledge on microplastic fate in surface waters, we developed a framework in which microplastic use rates and general properties can be used to estimate the range of expected environmental concentrations depending on assumptions about removal and decay. We developed a web-based tool incorporating 10 removal rates and 10 decay rates encompassing the typical and extreme ranges of possible values. Each of the 100 model runs produces a distribution of Predicted Environmental Concentration (PECs) representing each effluent impacted stream as described by the iSTREEM® model which estimates spatially-explicit concentrations of chemicals in effluent and receiving waters across the US. Output visualization in the interactive tool includes a broad view of all possible combinations in a matrix format, and a detailed view of the full distribution of PECs for individual model runs. Within the matrix, each of the 100 individual cells correspond to a selected percentile of the PEC distribution (e.g., 95th percentile) for tha combination of removal and decay. We demonstrate the utility of this framework using WWTP influent loadings of polyethylene microbeads from liquid soaps and shower gels estimated using per-capita usage (Gouin et al 2011) and combine with individual facility population served and flow estimates using the iSTREEM model. We can the investigate the question … What kind of environmental concentrations might we estimate using these emissions? This dynamic framework can be used to help inform environmental exposure assessments by readily providing PECs based on varying model inputs on WWTP removal and in-stream decay rates for microplastics, which continues to evolve as more research is conducted. While this framework was applied to the US at a national scale, the framework itself is not geographic-dependent and could function equally well utilizing PEC distributions from Europe or elsewhere.
C.M. Holmes, R. Vamshi, N.Maples-Reynolds (Waterborne Environmental); I.A. Davies, B. Jonas (Personal Care Products Council), S.D. Dyer (The Procter & Gamble
Company / Environmental Stewardship and Sustainability Organization). A Framework for Dynamic Estimation of Aquatic Environmental Concentrations of Microplastics Via WWTP Discharge. SETAC EU 2017. Poster.
PresentationsHome and Personal Care Products2017
Integrating Treatment Facility and River Network Information to Model Spatially-Explicit Environmental Concentrations of Down-The-Drain Substances: ISTREEM
iSTREEM® is a web-based model which estimates spatially-explicit environmental concentrations of down-the-drain chemicals in effluent and receiving waters across the USA. Concentrations are estimated at the discharge points of over 10,000 municipal wastewater treatment plants (WWTPs) and downstream receiving waters covering more than 350,000 km of rivers. The model incorporates WWTP information on population served, treatment type, and facility flow which are linked to a commonly used hydrology framework providing flow and hydrologic connectivity between facilities and downstream sites. As part of the hydrologic routing, a first-order decay is implemented to simulate environmental processes that remove chemical from the water column. The model allows for regional use rates to better simulate potential geographic variability in emissions, as well as differing removal rates to account for different facility treatment types. Given the assumption of temporally constant emission, the model is able to efficiently execute as a single, annual model run. The publicly available web-based model (www.iStreem.org) exemplifies open access to modeling resources, with no software installation required, and computation resources for model runs performed by the iSTREEM server. Users are able to save and retrieve runs, interact with results in a map format, or download source data and model results for more in-depth analysis by the user, including linking to desktop mapping software. The model, sponsored by the American Cleaning Institute (ACI, www.cleaninginstitute.org), is a valuable tool for both promoting product and ingredient stewardship and potential regulatory compliance for chemical suppliers and manufacturers of formulated products. The framework and modular nature of the model allow it to be applied to different geographies beyond the current USA-wide dataset.
C.M. Holmes, R. Vamshi (Waterborne Environmental); P. DeLeo, D. Ferrer (American Cleaning Institute); S.D. Dyer (The Procter & Gamble Company / Environmental Stewardship and Sustainability Organization). Integrating Treatment Facility and River Network Information to Model Spatially-Explicit Environmental Concentrations of Down-The-Drain Substances: ISTREEM. Presentation. SETAC Europe 2017.
PresentationsHome and Personal Care Products2017
Estimating Sewer Residence Time at the National Scale to Enable Probabilistic Risk Assessment of Down-The-Drain Household Consumer Product Ingredients
Many household consumer product ingredients disposed of down-the-drain can undergo significant degradation in the sewer system prior to being treated and discharged from a wastewater treatment facility. Understanding the distribution of sewer residence times for wastewater at the national scale, in combination with in-sewer biodegradation data for specific chemicals, can provide a more realistic assessment of environmental exposure and risk. However, the availability of data for sewer residence times at the national or regional scale is currently limited. We overview how commonly-available data resources such as road networks, land use and population data, and wastewater treatment facility data can be analyzed spatially to estimate the distribution of sewer residence times at a national or regional scale. This approach was developed using case study sewer system data and extrapolated to a national dataset of over 3,400 wastewater treatment facilities across the U.S., yielding a national median residence time of 3.3 hours. We demonstrate how sewer residence time distributions derived by this spatial approach can be used as a tool to enable probabilistic risk assessment of down-the-drain household consumer product ingredients for a given country or region.
K.E. Kapo, R. Vamshi, M. Sebasky, C.M. Holmes (Waterborne Environmental), M. Paschka, K. McDonough (P&G). “Estimating Sewer Residence Time at the National Scale to Enable Probabilistic Risk Assessment of Down-The-Drain Household Consumer Product Ingredients”. Presentation. SETAC EU 2017.
PostersHome and Personal Care Products2016
A Spatial Approach for Estimating the National Distribution of Sewer Residence Times for Wastewaters in the U.S.
Sewer residence time can have a significant influence on the environmental fate and transport of wastewater constituents, including down-the-drain household consumer product ingredients. In this study, best-available data resources and geoprocessing tools were used to develop a spatial approach for estimating the national distribution of sewer residence times for wastewaters in the U.S. Case studies estimating sewer residence times for two municipalities demonstrated that road networks could be used as a spatial proxy for sewer networks when the latter data is not available. The approach was then extrapolated to a national dataset of >3,400 wastewater treatment plant (WWTP) facilities across the U.S. to estimate the national distribution of sewer residence times, with an estimated national median sewer residence time of 3.3 hours. Sewer residence times for smaller WWTP facilities (< 1 million gallons per day) were comparatively shorter than larger facilities, however the latter comprised a greater proportion of the overall national wastewater volume. The sewer residence time distributions derived in this study can be combined with in-sewer biodegradation data to estimate WWTP influent concentrations of down-the-drain household consumer product ingredients as part of a national-scale probabilistic risk assessment.
Katherine Kapo, Raghu Vamshi, Megan Sebasky (Waterborne), Michael Paschka, Kathleen McDonough (P&G). “A Spatial Approach for Estimating the National Distribution of Sewer Residence Times for Wastewaters in the U.S.” Poster. SETAC NA 2016.
PresentationsHome and Personal Care Products2016
Spatial Improvements Leading to Advances in Down-the-Drain Chemical Exposure Modeling with iSTREEM® 2.0
iSTREEM® (“in-stream exposure model”) is a publicly-available web-based model (www.istreem.org) that estimates down-the-drain chemical concentrations in waste water treatment plant (WWTP) effluents, drinking water intakes (DWI), and in streams impacted by domestic waste water effluent across the continental U.S. and a number of watersheds in Canada under mean annual and low-flow (7Q10) conditions. Major upgrades to the model’s underlying data were made by incorporating higher-resolution and more current spatial datasets, leading to the release of iSTREEM® 2.0. The presentation provides an overview of the development of iSTREEM® 2.0, including how specific data needs were addressed and major assumptions considered in developing the model. The model river network was upgraded to a higher-resolution hydrologic dataset based on the USEPA and USGS NHDPlus version 2, which constitutes about 228,000 river segments totaling 243,000 river miles across continental U.S. For all the river segments, estimated mean annual flows were derived from NHDPlus, but low flows (7Q10) were exclusively developed for iSTREEM® 2.0. WWTP and associated facility level information were derived from the most recent USEPA Clean Watershed Needs Survey 2012 dataset, which includes about 13,000 facilities accounting for a total population of 175 million and effluent flow of 25,000 MGD. WWTP facilities were associated to the river network by applying techniques developed by USEPA. Enhancements to the model algorithm has made it possible to run the simulations efficiently and examine chemical exposure at a detailed spatial scale over a large geography (river basins or U.S.). Model simulation results are accessible to users in tabular (MS Excel) and spatial (MS Access) data formats for easy interpretation and further customization. A case study comparing prior version of the model and latest iSTREEM® 2.0 for the U.S will be presented to examine the impact of recent upgrades to model results – with focus on the national distribution of flows (mean and 7Q10’s), effluent PEC’s, water use, dilution factors, and receiving surface water PEC’s. The developments to iSTREEM® improves its utility as a tool to support environmental exposure assessments by a variety of users for environmental risk assessments across multiple commodity groups (personal care products, pharmaceuticals, food additives, pesticides, etc.).
Raghu Vamshi, Katherine Kapo, Chris Holmes (Waterborne), Paul DeLeo, Darci Ferrer (American Cleaning Institute). “Spatial Improvements Leading to Advances in Down-the-Drain Chemical Exposure Modeling with iSTREEM® 2.0“. Presentation. SETAC NA Orlando. 2016.
PresentationsHome and Personal Care Products2016
A Framework for Dynamic Estimation of Environmental Concentrations of Microplastics in WWTP Effluents and Receiving Waters at a National Scale
Down-the-drain exposure models provide a valuable screening-level tool for estimating environmental exposure to product ingredients which are treated and discharged at municipal wastewater treatment plants. Microplastics, plastic particles smaller than 5 mm diameter, enter wastewater treatment plants (WWTP) due to a variety of sources. Exposure modeling was performed using the iSTREEM® model, a publicly-available web-based model supported by the American Cleaning Institute (www.istreem.org) which estimates spatially-explicit concentrations of chemicals in effluent and receiving waters across the U.S. WWTP influent loadings of microbeads were estimated using per-capita usage derived from market manufacture survey (Gouin et al 2015) combined with individual facility population served and flow estimates within the iSTREEM® model. The analysis used multiple values for removal during treatment based on total suspended solid removal data and a wide range of in-stream decay rates, resulting in a variety of potential environmental exposure estimates. The removal and decay rates have a non-linear effect across the varying facilities & stream segments in the US landscape. Therefore, we developed an approach which leverages the advantages of the iSTREEM® model (national scope, individual facilities, and distributions of output) with the ability to screen for potential concern based on uncertain (and dynamic) removal and decay rates. This allows for flexibility in modeling the environmental concentration of microbeads regardless of size, weight, or physicochemical properties. We developed a 2-dimensional matrix with removal rate and decay rate as the primary axes. The individual cells within the array will then correspond to a reasonable worst-case Predicted Environmental Concentration (PEC) (e.g. 95th percentile) based on the national iSTREEM® results. These concentrations are based on a proxy quantity of microbeads which can be easily scaled. Therefore, with the matrix it is possible to supply an approximate removal and decay rate for the microplastic of interest and assess the estimated exposure by scaling the matrix value using the relationship between the substance quantity of interest and the proxy. This matrix framework can be used to help inform environmental exposure assessments by readily providing concentrations based on varying model inputs on WWTP removal and in-stream decay rates for microplastics, which continues to evolve as more research is conducted.
Nikki Maples-Reynolds, Chris M. Holmes, Raghu Vamshi (Waterborne), Iain A. Davies, Beth A. Lange (Personal Care Products Council), Scott Dyer (The Procter & Gamble Company). “A Framework for Dynamic Estimation of Environmental Concentrations of Microplastics in WWTP Effluents and Receiving Waters at a National Scale.” Presentation. SETAC NA. 2016.
PresentationsHome and Personal Care Products2016
Ecological Exposure Assessment Approaches for Indoor Use Pyrethroids in POTW Effluent
- Session title: Environmental Risk Assessment of Down-the-Drain Chemicals
- Presentation type: Presentation
- Presentation room: Commonwealth Hall A1 at 2:35PM
- Presentation date: Thursday, August 25, 2016
- Presenting Author: Chris Holmes
Indoor use pesticides are regulated for potential environmental impacts after movement down the drain and eventual release from publicly owned treatment works (POTWs). Pyrethroids are commonly used within the home for applications such as general household insect control (including ants, cockroaches, fleas and bedbugs) by both professional and homeowner application, for houseplant protection, as an insect repellent on clothing, and for the maintenance of pet health. Depending on the application type, some portion of the pyrethroid may be disposed of down the drain via cleaning of hard surfaces after application, washing of clothing or bedding after treatment, and bathing pets indoors. As pyrethroids traverse the sewer system and eventually are released from wastewater treatment plants, a large fraction is removed from the effluent water due to the extremely high hydrophobicity of pyrethroids and the prevalence of organic material to which it can adsorb. However, some pyrethroid residues do pass through to the POTW effluent along with dissolved organic matter and these are mixed into river flow. It is at this point (as well as for downstream river reaches), that an assessment of the potential ecological effects of the bioavailable fraction of pyrethroids must be conducted. Using results for several pyrethroids, this presentation will discuss the relevant aspects that should be considered in an ecological risk assessment. In addition, a tiered approach for conducting an exposure assessment using models at various spatial scales will be presented along with an evaluation of the potential impact of various sources of uncertainty in these assessments. Comprehensive pyrethroid POTW monitoring data are available to help provide context for refined model output.
Chris Holmes* , Stephanie Herbstritt, Amy Ritter (Waterborne Environmental), Scott Jackson (BASF Corporation), Russell Jones (Bayer CropScience), Paul Hendley (Phasera Ltd.), Richard Allen (Valent USA Corportation), Gary Mitchell (FMC Corporation). “Ecological Exposure Assessment Approaches for Indoor Use Pyrethroids in POTW Effluent”. Presentation. ACS 2016.