Papers & ReportsWater/Wastewater Assessments2017
Estimation of U.S. sewer residence time distributions for national-scale risk assessment of down-the-drain chemicals
Sewer residence time (the amount of time a given volume of wastewater resides in a sewer system prior to treatment) can have a significant influence on predictions of environmental fate and transport of wastewater constituents and corresponding risk assessment. In this study, a geographic information systems-based approach for estimating the distribution of sewer residence times for the U.S. was developed using road networks as a spatial proxy for sewer networks. The suitability of the approach was evaluated using case study municipalities, and the approach was subsequently extrapolated to 3422 wastewater treatment facilities of varying size across the U.S. to estimate a national distribution of sewer residence times. The estimated national median residence time for the U.S. was 3.3 h. Facilities serving smaller municipalities (< 1 million gallons per day) had comparatively shorter sewer residence times to facilities serving larger municipalities, though the latter comprise a greater proportion of overall national wastewater volume. The results of this study provide an important data resource in combination with chemical in-sewer biodegradation data to enable probabilistic risk assessment of consumer product chemicals disposed of down the drain.
Kapo, K.E., Paschka, M., Vamshi, R., Sebasky, M., McDonough, K. (2017), Estimation of U.S. sewer residence time distribution for national-scale risk assessment of down-the-drain chemicals. Science of The Total Environment, Volumes 603-604, 445-452. doi.org/10.1016/j.scitotenv.2017.06.075
Papers & ReportsWater/Wastewater Assessments2016
istreem®: An approach for broad-scale in-stream exposure assessment of “down-the-drain” chemicals
The “in‐stream exposure model” iSTREEM®, a Web‐based model made freely available to the public by the American Cleaning Institute, provides a means to estimate concentrations of “down‐the‐drain” chemicals in effluent, receiving waters, and drinking water intakes across national and regional scales under mean annual and low‐flow conditions. We provide an overview of the evolution and utility of the iSTREEM model as a screening‐level risk assessment tool relevant for down‐the‐drain products. The spatial nature of the model, integrating point locations of facilities along a hydrologic network, provides a powerful framework to assess environmental exposure and risk in a spatial context. A case study compared national distributions of modeled concentrations of the fragrance 1,3,4,6,7,8‐Hexahydro‐4,6,6,7,8,8,‐hexamethylcyclopenta‐γ‐2‐benzopyran (HHCB) and the insect repellent N,N‐Diethyl‐m‐toluamide (DEET) to available monitoring data at comparable flow conditions. The iSTREEM low‐flow model results yielded a conservative distribution of values, whereas the mean‐flow model results more closely resembled the concentration distribution of monitoring data. We demonstrate how model results can be used to construct a conservative estimation of the distribution of chemical concentrations for effluents and streams leading to the derivation of a predicted environmental concentration (PEC) using the high end of the concentration distribution (e.g., 90th percentile). Data requirements, assumptions, and applications of iSTREEM are discussed in the context of other down‐the‐drain modeling approaches to enhance understanding of comparative advantages and uncertainties for prospective users interested in exposure modeling for ecological risk assessment.
Kapo, K.E., DeLeo, P.C., Vamshi, R., Holmes, C.M., Ferrer, D., Dyer, S.D., Wang, X., White-Hull, C. (2016), iSTREEM®: An approach for broad-scale in-stream exposure assessment of “down-the-drain” chemicals. Integr Environ Assess Manag. 12: 782-792. doi.org/10.1002/ieam.1793
Papers & ReportsWater/Wastewater Assessments2016
Eco-epidemiology of aquatic ecosystems: Separating chemicals from multiple stressors
A non-toxic environment and a good ecological status are policy goals guiding research and management of chemicals and surface water systems in Europe and elsewhere. Research and policies on chemicals and water are however still disparate and unable to evaluate the relative ecological impacts of chemical mixtures and other stressors. This paper defines and explores the use of eco-epidemiological analysis of surveillance monitoring data sets via a proxy to quantify mixture impacts on ecosystems. Case studies show examples of different, progressive steps that are possible.
Case study data were obtained for various regions in Europe and the United States. Data types relate to potential stressors at various scales, concerning landscape, land-use, in-stream physico-chemical and pollutant data, and data on fish and invertebrates. The proxy-values for mixture impacts were quantified as predicted (multi-substance) Potentially Affected Fractions of species (msPAF), using Species Sensitivity Distribution (SSD) models in conjunction with bioavailability and mixture models.
The case studies summarize the monitoring data sets and the subsequent diagnostic bioassessments. Variation in mixture toxic pressures amongst sites appeared to covary with abundance changes in large (50-86%) percentages of taxa for the various study regions. This shows that an increased mixture toxic pressure (msPAF) relates to increased ecological impacts. Subsequent multi-stressor evaluations resulted in statistically significant, site-specific diagnosis of the magnitudes of ecological impacts and the relative contributions of different stress factors to those impacts. This included both mixtures and individual chemicals. These results allow for ranking stressors, sites and impacted species groups. That is relevant information for water management.
The case studies are discussed in relation to policy and management strategies that support reaching a non-toxic environment and good ecological status. Reaching these goals requires not only focused sectoral policies, such as on chemical- or water management, but also an overarching and solution-focused view.
Posthuma, L., Dyer, S.D., de Zwart, D., Kapo, K.E., Holmes, C.M., Burton Jr., G.A. (2016), Eco-epidemiology of aquatic ecosystems: Separating chemicals from multiple stressors. Science of The Total Environment, Volume 573, 1303-1319.
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.
Exposure and effects of clothianidin residues in corn pollen: Honey bee colony simulation in a field setting
As managed pollinator species, honey bees provide major pollination services to a wide variety of crops across the globe. At the same time, they are potentially vulnerable to the effects of systemic neonicotinoids because residues can occur in pollen and nectar collected by the bees. However, the assessment of potential effects of neonicotinoids on colonies in field studies is challenging because multiple environmental conditions interact with the colonies’ health. Honey bee colony models such as BEEHAVE provide the opportunity to assess potential influx of residues into a colony via different routes, and their effects on bees in the hive can be dependent on their stage-dependent consumption rates and sensitivities. We extended BEEHAVE to represent exposure to clothianidin via residues in pollen from treated corn fields. Landscapes around the colonies were simulated using land cover data from sites across the Midwest of the United States. Simulated foragers collect pollen from flower resources across the landscape including corn pollen during the corn blooming period. Clothianidin residues are consumed by larvae and worker bees. Different residue levels in corn pollen were applied to assess impacts on honey bee colonies over a one-year cycle. Clothianidin effects on colony strength were only observed if unrealistically high residue levels in the pollen were simulated. The landscape composition significantly impacted the collection of pollen (residue exposure) from the corn fields, resulting in higher colony-level effects in landscapes with low proportions of semi-natural land. The case study with the mechanistic honey bee colony model presents a path to the application of such models in the context of pesticide risk assessment.
Amelie Schmolke (Waterborne Environmental), Farah Abi-Akar (Waterborne Environmental), Silvia Hinarejos (Sumitomo). Exposure and effects of clothianidin residues in corn pollen: Honey bee colony simulation in a field setting. Platform SETAC 2018. Sacramento, CA.
Applying a mechanistic honey bee colony model to assess multiple factors impacting colony overwintering survival
Honey bee colony feeding studies are one type of Tier II semi-field studies designed to determine potential effects of pesticides on free-foraging whole colonies during and after dietary intake of a known pesticide concentration. These studies represent a progressively more realistic level of refinement for pollinator studies compared to individual laboratory-based studies since they are intended to reflect a worst-case exposure scenario in the field. Colony feeding studies are designed to test toxicity over a foraging season and following overwintering period. However, such studies are very cost- and time-intensive to conduct, and high overwintering losses of control hives have been observed in some studies. Loss of control colonies indicates that stressors other than pesticides, e.g. resource availability, weather, diseases and beekeeping activities, likely influence colony overwintering survival, confounding the assessment of impacts caused by pesticides. Honey bee colony models have been gaining interest as tools in pesticide risk assessment to inform study design and ultimately, colony-level risks to honey bees. In the current study commissioned by the Pollinator Research Task Force, we apply the honey bee colony model BEEHAVE to simulate colony dynamics observed in negative control colonies from multiple colony feeding studies. Detailed landscape-level data inform the resource availability for the simulated foragers in the model. In addition, weather data, initial colony condition and feeding patterns were analyzed across studies and translated to model inputs. In a calibration step, we adjusted parameters in BEEHAVE to achieve simulated dynamics corresponding to colony conditions reported in the studies. Study data collected in summer and fall were analyzed for predictors of overwintering success of individual colonies. BEEHAVE simulations with different combinations of external factors were used to assess their importance for colony condition. Colony conditions at study initialization and feeding patterns both influenced the colony condition in the fall, and thus, the probability of overwintering survival. Model simulations can be used to estimate colony-level outcomes under conditions deviating from those in the studies to inform study design and extend the use of the available data. Pesticide effects can be included in future model analyses, and analyzed in the context of multiple factors that impact colony health and overwintering success.
Amelie Schmolke (Waterborne Environmental), Farah Abi-Akar (Waterborne Environmental), Nika Galic (Syngenta), Silvia Hinarejos (Sumitomo). Applying a mechanistic honey bee colony model to assess multiple factors impacting colony overwintering survival. Platform SETAC 2018. Sacramento, CA.
Combining an individual-based model and an aquatic food web-ecosystem model to assess ecological risks: A case study with the endangered Topeka shiner
The Comprehensive Aquatic System Model (CASM) is a process-based integrated bioenergetics and habitat quality model that simulates population, community, and ecosystem-level effects of chemical stressors based on an aggregated population structure defined by an average-sized individual. An individual-based bioenergetics and population model (IBM) was developed for the endangered Topeka shiner (Notropis topeka) to incorporate detailed life-history and age-specific and size-specific attributes of population dynamics not represented in the CASM. The models were executed in tandem with daily IBM population growth dynamics transferred to CASM, which in turn computed the corresponding daily modifications to the food web. The CASM food web results were transferred back to the IBM in the form of adjusted Topeka shiner prey biomass values. This uniquely integrated model combination was implemented to simulate potential ecological risks for Topeka shiner in a generalized Iowa headwater pool, representative of known Midwestern habitat and range for this species. Ecological risks were computed using time-integrated differences between the population biomass values of 365-day baseline and exposure simulations. Risks were estimated for example daily pesticide exposures of varying magnitude, timing, and duration. Potential direct toxic effects to Topeka shiners were modelled within the IBM. The resulting modelled impacts on population biomass were used by the CASM to compute corresponding food web-ecosystem effects. The IBM provided the capability to examine the potential population-level risks based on detailed sensitivities of early life stages and adults to pesticide exposures. The CASM extended the IBM assessment capability by extrapolating potential direct effects on Topeka shiners to associated indirect changes in headwater pool community structure and ecosystem function. The presentation highlights the advantages afforded by the integrated IBM-CASM modeling approach to ecological risk assessment.
Steven Bartell (Cardno), Amelie Schmolke (Waterborne Environmental), Colleen Roy (Waterborne Environmental), Nicholas Ralston (University of North Dakota), Daniel Perkins (Waterborne Environmental), Nika Galic (Syngenta), Richard Brain (Syngenta). Combining an individual-based model and an aquatic food web-ecosystem model to assess ecological risks: A case study with the endangered Topeka shiner. Platform SETAC 2018. Sacramento, CA.
A US, field-scale, herbicide spray drift deposition and biological evaluation study: Methods and implications for risk assessment
Spray drift from pesticide applications is considered as a potential route of exposure in environmental risk assessment. Typically, spray drift deposition is modeled using terrestrial plant effects endpoint derived from worst-case, full rate direct spray studies, and combined in the risk assessment framework to represent extreme worst-case risk to non-target organisms. The objective of this work was to merge observed plant effects with spray drift exposure in a single study. A 40-acre field-scale, spray drift study was developed to simultaneously measure spray drift deposition, airborne interception, and potential biological effects of an herbicide under conservative drift conditions and a relatively low-drift nozzle. This study was conducted in four replications, each with a two-swath spray pattern (90 ft per swath) upwind of a deposition zone (perpendicular to wind direction), generally following the generic U.S. Environmental Protection Agency verification protocol, Testing Pesticide Application Spray Drift Reduction Technologies for Row and Field Crops. Within each replicate application, an array of three perpendicular sampling lines were used to measure drift deposition out to 400 ft, airborne interception out to 75 ft, and potential direct plant effects at set distances (5, 15, 25, 23, and 45 ft) from the edge of the downwind spray application . At each distance and sampling line, further replication of spray drift deposition, airborne interception, and biological effects were assessed in replicated fashion in a nested, replicated design. The timing of the herbicide application for each of the four replications targeted steady wind speeds between 8 to 12 mph. Wind direction was measured within a 30-degree angle of the downwind field orientation to ensure that spray drift would travel toward the collection area and across the furthest sampling points. Results from this study design refine effects determined in laboratory studies under worst-case exposure scenarios (i.e. direct over the top application) by addressing how terrestrial non-target plants actually experience exposure under natural conditions in the field, which can better inform risk assessment and risk management decisions.
Daniel Perkins (Waterborne Environmental), Greg Goodwin (Waterborne Environmental), Greg Kruger (University of Nebraska-Lincoln), Abby Lynn (All Aspects Consulting), Farah Abi-Akar (Waterborne Environmental), Richard Brain (Syngenta). A US, field-scale, herbicide spray drift deposition and biological evaluation study: Methods and implications for risk assessment. Platform SETAC 2018. Sacramento, CA.
Influence of particle size on prospectively modeled environmental concentrations of microplastics in the Sandusky River watershed
The presence of nano- and microplastics (MPs; particles < 5 mm) in the aquatic environment is a topic of increasing discussion and research. Although measurement and monitoring data are indispensable, there is a need to prospectively estimate concentrations to enable forward-looking assessments and to guide analysis of retrospective ecological analyses. For traditional chemicals, fate and exposure models have been proven to be very helpful and are widely used. However, to date few models exist that simulate the transport and fate of MPs in freshwater systems. This presentation presents simulations of the transport and fate of various-sized MPs emitted from wastewater treatment plants into freshwater riverine systems, and tracks concentrations moving downstream from headwater into Lake Erie. We linked the NanoDUFLOW model (a detailed MP aggregation-sedimentation model integrated in a hydrological and particle transport model) with iSTREEM® (developed to estimate chemical concentration distributions for all rivers receiving WWTP discharges in the US) for a range of particle sizes. This combines the mechanistic realism of NanoDUFLOW, accounting for formation and settling of heteroaggregates, with the US well-established iSTREEM implementation. Depth dependent in-stream first order removal rate constants simulated with NanoDUFLOW were combined with standard iSTREEM output which simulated the emission, transport and water column concentrations of different MP sizes. We modeled floating as well as non-buoyant MP, for sizes ranging from 100 nm to 1000 µm. We also modeled a combined mixture of particle sizes based on effluent measurements from Mason et al (2016). Simulations were spatially explicit with MP concentrations being modeled for the Sandusky River watershed in Ohio containing over 300 miles of river downstream of 20 WWTPs. Modelling results show the effects of population density, MP size and environmental conditions on riverine concentrations and export to Lake Erie. Buoyant as well as the smallest non-buoyant MP fractions can be transported over long distances, reaching receiving waters such as the Great Lakes. In contrast, larger non-buoyant MPs settle more locally in the vicinity of the WWTPs.
Christopher Holmes (Waterborne Environmental), Albert Koelmans (Wageningen University), Scott Dyer (Waterborne Environmental). Influence of particle size on prospectively modeled environmental concentrations of microplastics in the Sandusky River watershed. Poster SETAC 2018. Sacramento, CA.