Presentation on theme: "1 Evaluation of Water Contamination from Consumer Product Uses Rick Reiss SOT DC Spring Symposium April 15, 2010."— Presentation transcript:
1 Evaluation of Water Contamination from Consumer Product Uses Rick Reiss SOT DC Spring Symposium April 15, 2010
2 Introduction Many consumer products are disposed of down residential drains Transported into sewer systems and potentially released into the environment Contaminate waterways leading to risk to aquatic species Potentially make its way into drinking water Sorb to sludge in sewage treatment plants Some sludge is used as biosolids for agricultural amendment Potential for terrestrial exposures
3 Factors Affecting Potential Risks Quantities used Methods of disposal Dilution into waterway Physicochemical properties Binding to organic matter Aquatic degradation Toxicity to aquatic organisms
4 Summary of Reconnaissance Studies USGS has performed surveys in streams, surface water sources of drinking water, and groundwater Found a variety of antimicrobials, fragrances, flavoring chemicals, pesticides, plasticizers, cosmetics, etc. However, the low levels of most detections raises questions about whether there is a risk Many potential chemicals have not been measured
6 Approach Triclosan (2,4,4’-trichloro-2’-hydroxydiphenyl ether) is a broad spectrum bactericide Generally low human toxicity, but high toxicity to algae Recent studies address estrogenic activity Used soaps, detergents, surface cleansers, disinfectants, cosmetics, pharmaceuticals, and oral hygiene products. Most (~95%) of the uses are disposed of down residential drains
7 Purpose of the Study Estimation of the distribution of triclosan concentrations in reaches following WWTP discharge. Based on: Characteristics of reaches Discharge mass from WTTP Physicochemical properties Estimation of risk to aquatic organisms based on most sensitive species in phylogenic groups.
8 Significant Factor Affecting Loading: Dilution at Outfall
9 Factors Affecting Triclosan Loading into Rivers Triclosan loading into river Influent concentration Removal efficiency in WWTP Physical properties of river Dilution pH Suspended sediment concentration Organic carbon content of sediment Physicochemical properties
10 Development of an Aquatic Exposure Model Steady-state model accounting for ionization, sorption with suspended sediment, and complexation with dissolved organic carbon (DOC). Downstream dissipation modeled from results of die- away studies. Probabilistic inputs developed for effluent concentration, pH, stream velocity, suspended sediment concentration (including organic carbon content), and DOC concentration
11 Characteristics of Reaches EPA’s Clean Water Needs Survey contains extensive data for WWTP facilities. Mean flow, low flow, velocity, pH, and discharge volume Of the 16,024 WWTPs in 1996, sufficient data were available for 11,010 facilities.
14 Triclosan Removal in Wastewater Treatment Plants
15 Wastewater Treatment Removal Significant removal due to high sorption to sludge Removal rates: Activated sludge: 94 to 96 percent (4 plants) Trickling filter: 58 to 96 percent (4 plants) Distribution of U.S. treatment plants: (1) activated sludge: 86%, (2) trickling filter: 12%, and (3) primary treatment: 2%.
16 Physicochemical Properties of Triclosan PropertyValue Molecular Weight289.6 Water Solubility12 mg/L Dissociation constant ( pK a )8.14 at 20 o C Vapor pressure7x10-4 Pa at 25 o C Partition coefficient (log K ow )4.8 Aerobic biodegradation in soil17.4-35.2 day half-life Aqueous photolysis41-min half-life at pH of 7 and 25 o C Adsorption to suspended solids ( K oc )47,454 mg/g
17 Correlation Between Suspended Sediment and Organic Carbon Content
18 Triclosan Die-Away Studies Triclosan dissipation in an 8 kilometer stretch of Cibalo Creek in south central Texas (Morrall et al.): Half-life, dilution-corrected, was 12.8 hours. Half-life, including dilution, was 5 hours Measured triclosan dissipation in the River Aire in the U.K. (Sabaliunus et al.): Half-life, including dilution, was 3.3 hours
19 Summary of Probabilistic Analysis Data on stream characteristics for 11,010 reaches obtained from Needs survey for both mean and low flow dilutions. Suspended sediment and DOC concentration from USGS data, and organic carbon content from correlation. Environmental fate properties of triclosan (e.g., sorption). Die-away rate
23 Margins of Safety 5 Miles Downstream, Low Dissipation (Low Flow)
24 Margins of Safety 5 Miles Downstream, High Dissipation (Low Flow)
25 Summary of Case Study There should be no direct effects to fish, plants or invertebrates due to triclosan exposures from WWTPs There may be some effects to algae for reaches where the dilution is low (or when the dilution is low) Uncertainties exist regarding degradates of triclosan in water, particularly due to photolysis
26 CASE STUDY #2 – TRICLOSAN TERRESTRIAL EXPOSURES
27 Introduction Triclosan has a high potential to sorb with organic matter Sludge is wastewater treatment plants is very rich in organic matter Some wastewater sludge is used as soil amendments in agriculture
28 Exposure Pathways Direct exposure Earthworms Soil microorganisms Terrestrial plants Secondary exposures Consumption of earthworms (birds and mammals) Fish exposed in water from wastewater effluent (birds and mammals)
36 Conclusions Everything must go somewhere! Especially things that don’t degrade quickly and/or stick to organic matter Risk assessment methods can be applied to address potential exposures in aquatic and terrestrial environments Can be used to differentiate real risks from mere exposures