Trace Organic Chemicals Research Articles

Performance Dynamics of Trace Organic Chemicals in Onsite Treatment Units and Systems

The purpose of this work is to improve our understanding regarding presence and attenuation of TOrC in onsite wastewater systems. A full-scale septic tank and sequencing batch membrane bioreactor (SBMBR) were used to provide water for the experiments conducted. Bench-scale soil columns were used to simulate the performance of soil absorption systems. Effluent from both STE and SBMBR were used in soil column experiments.The objectives of this study were to investigate the fate and occurrence of trace organic contaminants (TOrC) in Onsite Wastewater Systems (OWS). The data collected over the course of this study highlighted the lack of detailed TOrC occurrence data for onsite systems. As such a more robust sampling campaign was completed to characterize the occurrence and standard deviation of TOrC occurrence in septic tank effluents (STE). These results were compared with the variability of TOrC occurrence in advanced above ground treatment effluent. The main objective of the study was to detail the role of the quantity and type of organic matter in infiltrating water on the attenuation of TOrC. The rate at which water is applied to the subsurface may be important in the performance of soil absorption systems.The analytical methods and experimental approach used for this study are presented in Chapter 2.0. The occurrence of TOrC in septic tanks serving different unique sewersheds and above ground treatment steps are detailed in Chapter 3. Chapter 4 discusses the role of soil absorption systems on further treatment of TOrC in OWS, specifically the role of loading rate and the amount and type of organic carbon present in infiltrating water. Finally some conclusions and recommendations for future work are presented.This title belongs to WERF Research Report Series.ISBN: 9781843395300 (eBook)

Using Legacy Data to Relate Biological Condition to Cumulative Aquatic Toxicity in the Willamette River Basin (Oregon, USA)

In the Willamette River Basin (Oregon, USA), various residential, municipal, industrial, and agricultural activities produce physical, biological, and chemical stressors that may impinge on the basin's aquatic ecosystems. For > 30 years, numerous water-quality and biological-condition data have been accumulated by often disparate monitoring programs. This diagnostic analysis explored whether these legacy data could be used to correlate the presence of chemical stressors with biological condition impacts with the understanding that association is not necessarily causation. Other natural or anthropogenic stressors that may also impact biological conditions were not considered in this study. Acute-toxicity indices were calculated separately for trace metals and organic chemicals detected in surface waters between 1994 and 2010 and then compared with land-use metrics and vertebrate- and invertebrate-assemblage indices from surveys conducted basin-wide during this same period. Half of the possible relations between land use, biological condition, and toxicity were statistically significant at p ≤ 0.10. These results suggest that conditions for aquatic receptors improve either as agricultural or urban land decreases or as forested land increases and that chemical mixtures (primarily involving pesticides) may have impacted components of the basin's aquatic ecosystems. There may be a need for strengthened chemical-management practices on agricultural and urban lands and for maintaining undisturbed forested land to limit chemical migration into adjacent waters. Although these results indicate some utility for legacy data, they also suggest that a more defensible assessment of chemical stressors requires a program specifically designed for that purpose.

The pros and cons of using nanofiltration in lieu of reverse osmosis for indirect potable reuse applications

In recent years, considerable interest has been given to using nanofiltration (NF) in lieu of reverse osmosis (RO) for water reclamation applications. This work first examined the operational and rejection performance of several NF membranes compared to a commonly employed RO (ESPA2) membrane at a water reclamation facility. Rejection performance of the NF membranes mainly differed for monovalent ions, however, operational performance characterized by specific flux and flux decline differed substantially among the membranes evaluated. Based on preliminary testing, a promising NF membrane (NF270) was selected for pilot-scale testing and compared to pilot- and full-scale operation of the ESPA2 membrane. While the ESPA2 membrane exhibited significant flux decline primarily due to second stage scale formation, the NF270 membrane exhibited minimal flux decline, presumably due to the partial passage of sparingly soluble salts. Additionally, the NF270 membrane operated at a specific flux double that of the ESPA2 membrane and exhibited minimal flux decline at elevated recovery (87–88%). The major limitation with the NF270 membrane is the poor rejection of nitrate and inability to meet the California TOC requirements of less than 0.5 mg L −1. NF270 membrane permeate TOC concentrations were only marginally greater than the ESPA2 membrane and averaged 0.62 mg L −1 during 1300 h of testing. The rejection of a wide range of trace organic chemicals was evaluated during ESPA2 and NF270 membrane pilot-scale testing. Analysis of feed and permeate samples collected during NF270 membrane testing revealed that although more compounds could be detected in NF270 membrane permeate samples compared to the ESPA2 membrane, concentrations with the exception of atenolol and TCEP were consistently less than 100 ng L −1, which is significantly below any toxicological threshold level. An economic analysis using information gained through pilot-scale testing and full-scale operation revealed that significant cost savings could be achieved by using a low-pressure NF, such as the NF270 membrane.

Sorption of emerging trace organic compounds onto wastewater sludge solids

This work examined the sorption potential to wastewater primary- and activated-sludge solids for 34 emerging trace organic chemicals at environmentally relevant concentrations. These compounds represent a diverse range of physical and chemical properties, such as hydrophobicity and charge state, and a diverse range of classes, including steroidal hormones, pharmaceutically-active compounds, personal care products, and household chemicals. Solid-water partitioning coefficients ( K d ) were measured where 19 chemicals did not have previously reported values. Sludge solids were inactivated by a nonchemical lyophilization and dry-heat technique, which provided similar sorption behavior for recalcitrant compounds as compared to fresh activated-sludge. Sorption behavior was similar between primary- and activated-sludge solids from the same plant and between activated-sludge solids from two nitrified processes from different wastewater treatment systems. Positively-charged pharmaceutically-active compounds, amitriptyline, clozapine, verapamil, risperidone, and hydroxyzine, had the highest sorption potential, log K d = 2.8–3.8 as compared to the neutral and negatively-charged chemicals. Sorption potentials correlated with a compound’s hydrophobicity, however the higher sorption potentials observed for positively-charged compounds for a given log D ow indicate additional sorption mechanisms, such as electrostatic interactions, are important for these compounds. Previously published soil-based one-parameter models for predicting sorption from hydrophobicity (log K ow > 2) can be used to predict sorption for emerging nonionic compounds to wastewater sludge solids.

Chemical monitoring strategy for the assessment of advanced water treatment plant performance

A pilot-scale plant was employed to validate the performance of a proposed full-scale advanced water treatment plant (AWTP) in Sydney, Australia. The primary aim of this study was to develop a chemical monitoring program that can demonstrate proper plant operation resulting in the removal of priority chemical constituents in the product water. The feed water quality to the pilot plant was tertiary-treated effluent from a wastewater treatment plant. The unit processes of the AWTP were comprised of an integrated membrane system (ultrafiltration, reverse osmosis) followed by final chlorination generating a water quality that does not present a source of human or environmental health concern. The chemical monitoring program was undertaken over 6 weeks during pilot plant operation and involved the quantitative analysis of pharmaceuticals and personal care products, steroidal hormones, industrial chemicals, pesticides, N-nitrosamines and halomethanes. The first phase consisted of baseline monitoring of target compounds to quantify influent concentrations in feed waters to the plant. This was followed by a period of validation monitoring utilising indicator chemicals and surrogate measures suitable to assess proper process performance at various stages of the AWTP. This effort was supported by challenge testing experiments to further validate removal of a series of indicator chemicals by reverse osmosis. This pilot-scale study demonstrated a simplified analytical approach that can be employed to assure proper operation of advanced water treatment processes and the absence of trace organic chemicals.

Diagnostic Tools to Evaluate Impacts of Trace Organic Compounds Final Report

With the advent of improved analytical detection capabilities, a variety of organic chemicals have been found in trace amounts (Trace Organic Chemicals, TOrCs) in surface waters, sediment, and fish tissue. These TOrCs include pharmaceuticals, personal care products, surfactants, and other currently unregulated chemicals. This WERF sponsored research presents a preliminary screening process and ecological diagnostic approaches that could be used to help prioritize and evaluate treated wastewater-influenced sites that may be most at risk from trace organic chemical (TOrC) exposure. Identifying or predicting ecological effects of TOrCs in typical aquatic systems is challenging, requiring a variety of tools that can diagnose effects at multiple scales of ecological organization. Development of a prioritization process is the goal of Task 1 of this research and the focus of this report. This research developed three approaches to prioritize TOrCs: 1) risk-based, 2) chemical persistence, bioaccumulation potential, and toxicity (PBT), and 3) a hybrid based on risk, persistence, and bioaccumulation potential. Using an occurrence database compiled from over 100 monitoring studies, the three prioritization approaches were applied to over 500 TOrCs that have been detected in water or effluent samples in the U.S. over the past 10 years. Types of TOrCs identified as high priority differed among approaches: steroids/hormones, pharmaceuticals, and surfactants comprised most of the high priority TOrCs based on risk while pesticides, industrial chemicals, and PAHs comprised most of the high priority TOrCs based on a PBT approach. Except for the synthetic hormones and steroids, results of all three prioritization approaches yielded only a few pharmaceuticals of high priority. Using a risk-based prioritization approach, predicted chronic toxicity endpoints were more sensitive than endpoints based on estrogenic activity for most TOrCs. The prioritization list(s) resulting from this work is not necessarily intended to be viewed as a list of compounds to be monitored or for which water quality criteria should be developed. The process of developing the list(s) is as important as the list(s) itself and the appropriate use of any resulting list(s) will depend largely on the goals of the user. This title belongs to WERF Research Report Series . ISBN: 9781843395478 (Print) ISBN: 9781780403335 (eBook)

Testing Diagnostic Tools for Trace Organic Compounds and Multiple Stressors Case Studies

The screening Trace Organic Chemical (TOrC) ecological risk approach, developed previously, was evaluated using seven case studies, located in Pennsylvania, Ohio, Colorado, California, and Ontario, Canada. Sites represented a range of complexity, types of biological impacts, and wastewater effluent dilution at low flow. Several different techniques for diagnosing potential effects of TOrCs were incorporated in these case studies including U.S. EPA's causal analysis framework, CADDIS; Canada's Environmental Effects Monitoring (EEM) approach; the consumer products ROUT model and the pharmaceutical model PhATE to predict concentrations of certain TOrCs at a wastewater-influenced site; and ecological modeling (Comprehensive Aquatic Systems Model, CASM). Both prospective and retrospective assessments are represented in these case studies illustrating how various tools can be used to determine whether TOrCs are or could be a cause of biological impairment. At most sites, high priority TOrC data (using any of the TOrC prioritization approaches previously developed in this project) were unavailable. At five of the seven sites, the screening approach indicated a potential for risk due to TOrCs based on the type of wastewater treatment available (secondary treatment with little or no nutrient removal, potential input sources of TOrCs present in addition to domestic sources) and the relatively high effluent concentration under low flow conditions. Except for two sites, data were unavailable for at least one level of biological organization making it difficult to evaluate TOrCs as a cause of impairment. The lack of diagnostic TOrC exposure data (i.e., suborganismal or organismal measures indicative of exposure to a certain class of TOrCs), or organism effects data (e.g., intersex, lesions) at most sites restricted the researchers' ability to diagnose whether certain TOrCs could have contributed to observed biological impairment at these sites. Their analyses confirm that the comprehensiveness and sensitivity of the population/community assessment is a critical factor affecting the success of diagnostic analyses. Indices of biological integrity (IBI) and most metrics that constitute such indices, offered little definitive diagnostic information regarding risks due to TOrCs, but were useful in supporting or eliminating other types of stressors such as excess nutrients and habitat quality. None of the case studies examined had sufficient TOrC data with which to demonstrate linkages between concentrations of specific TOrCs or groups of TOrCs and organism effects. However, results from two sites suggested that TOrC concentrations exceeding conservative screening threshold values may not result in observed effects at either the organism or population level based on the endpoints measured. While some of the case studies demonstrated apparent linkages between exposure to estrogenic chemicals and organism effects, none had sufficient information to definitively link organism and population/community level effects. Defining the conditions under which organism TOrC effects are likely to manifest as a population-level effect at a site should be a critical component of Phase 2. This title belongs to WERF Research Report Series . ISBN: 9781843395393 (eBook)

Development of Diagnostic Tools for Trace Organic Compounds and Multiple Stressors

This WERF sponsored research presents a preliminary screening process and ecological diagnostic approaches that could be used to help prioritize and evaluate treated wastewater-influenced sites that may be most at risk from trace organic chemical (TOrC) exposure. This work builds on the TOrC prioritization research completed earlier in this research and demonstrates how current diagnostic approaches used in the U.S. (CADDIS) and Canada (Environmental Effects Monitoring) could be extended to evaluate potential risks due to TOrCs. The screening process uses indicators in four categories: (1) wastewater influent and population served, (2) wastewater treatment characteristics, (3) ecological characteristics of the site, and (4) exposure or effects information from the site if available. The indicators included in the screening process are hypotheses, to be tested further using case studies in this research, and should not be taken as validated measures to be used to infer TOrC issues at a site. The diagnostic approach described in this research could be applied prospectively (could ecological effects due to TOrCs occur at my site?) and retrospectively (I have observed ecological effects at my site; are TOrCs a contributing cause?). However, given our current lack of knowledge concerning modes of action for many TOrCs, as well as the factors that determine whether TOrC effects on individuals are translated to community-level ecological effects, the diagnostic approach in this research focuses on retrospective applications at this time. The screening process has been used with some modification for sites in the Ohio Erie Drift Plain ecoregion and some of these, as well as other sites, will be evaluated using diagnostic approaches in Task 3 (case studies) of this research. A web-based database application ( ) has been developed for this project to help end users eventually search and evaluate TOrC data collected by many organizations in the U.S. and to assist in screening and diagnosing risks due to TOrCs. Comments are welcome on the various search features and metadata available for TOrCs within the current database. This title belongs to WERF Research Report Series . ISBN: 9781843395348 (eBook)

Diagnostic Tools to Evaluate Impacts of Trace Organic Compounds Prioritization Framework for Trace Organic Compounds

With the recent advent of improved analytical and biomarker detection capabilities, a variety of organic chemicals have been found in trace amounts (Trace Organic Chemicals, TOrCs) in surface waters and fish tissue. TOrCs include pharmaceuticals, personal care products, surfactants, pesticides, flame retardants, and other organic chemicals, some with unknown modes of action or effects. Identifying or predicting ecological effects of TOrCs in typical aquatic multi-stressor situations is challenging, requiring a variety of epidemiological tools that together, can diagnose effects at multiple scales of ecological organization. Five objectives were addressed in this research: (1) develop and apply a procedure to prioritize which TOrCs are of most concern; (2) develop and test a conceptual site screening framework; (3) evaluate and test diagnostic approaches to identify potential risks due to TOrCs using various case studies; (4) develop a relational database and user interface with which the water resource community can enter, store, and search TOrC exposure data in the U.S.; and (5) foster partnerships and transfer knowledge gained in this research to the water quality community. TOrC fate, effects, and occurrence data were compiled in a database for over 500 organic chemicals based on over 100 published studies representing more than 50 organizations and 700 sites. Alternative risk-based prioritization processes and draft lists of high priority TOrCs were developed. A preliminary site screening and diagnostic framework was developed and evaluated using seven different case study sites. EPA's causal analysis (stressor identification) procedures, Canada's Environmental Effects Monitoring (EEM) procedure, the ecosystem model CASM (Comprehensive Aquatic System Model), and several other specialized diagnostic tools were used and evaluated. A relational database based on Tetra Tech's EDAS2 was developed using the Microsoft platform. The modified version of EDAS2, built on the EPA WQX data model, provides web-based data queries using a combination of tabular data for downloads and a visual map interface that allows the user to view, query, and select sites from the map having chemical or biological data. The database is not discussed in this report but can be accessed through WERF. This Final Report summarizes all other approaches used and results obtained in this research, discusses critical data gaps and other important uncertainties, and provides testable hypotheses and recommendations for Phase 2 testing and analyses.This title belongs to WERF Research Report Series.ISBN: 9781843395355 (eBook)

Chemical monitoring strategy for the assessment of advanced water treatment plant performance

A pilot-scale plant was employed to validate the performance of a proposed full-scale advanced water treatment plant (AWTP) in Sydney, Australia. The primary aim of this study was to develop a chemical monitoring program that can demonstrate proper plant operation resulting in the removal of priority chemical constituents in the product water. The feed water quality to the pilot plant was tertiary-treated effluent from a wastewater treatment plant. The unit processes of the AWTP were comprised of an integrated membrane system (ultrafiltration, reverse osmosis) followed by final chlorination generating a water quality that does not present a source of human or environmental health concern. The chemical monitoring program was undertaken over 6 weeks during pilot plant operation and involved the quantitative analysis of pharmaceuticals and personal care products, steroidal hormones, industrial chemicals, pesticides, N-nitrosamines and halomethanes. The first phase consisted of baseline monitoring of target compounds to quantify influent concentrations in feed waters to the plant. This was followed by a period of validation monitoring utilising indicator chemicals and surrogate measures suitable to assess proper process performance at various stages of the AWTP. This effort was supported by challenge testing experiments to further validate removal of a series of indicator chemicals by reverse osmosis. This pilot-scale study demonstrated a simplified analytical approach that can be employed to assure proper operation of advanced water treatment processes and the absence of trace organic chemicals.

Indicator compounds for assessment of wastewater effluent contributions to flow and water quality

Numerous studies have reported the presence of trace (i.e., ng/L) organic chemicals in municipal wastewater effluents, but it is unclear which compounds will be useful to evaluate the contribution of effluent to overall river flow or the attenuation processes that occur in receiving streams. This paper presents a new approach that uses a suite of common trace organic chemicals as indicators to assess the degree of impact and attenuation of trace organic chemicals in receiving streams. The utility of the approach was validated by effluent monitoring at ten wastewater treatment plants and two effluent-impacted rivers with short retention times (<17h). A total of 56 compounds were particularly well suited as potential indicators, occurring frequently in effluent samples at concentrations that were at least five times higher than their limit of quantification. Monitoring data from two effluent-impacted rivers indicated that biotransformation was not important for these two river stretches, whereas photolysis attenuation was possibly important for the shallow river. The application of this approach to receiving waters and water reclamation and reuse systems will allow for more effective allocation of resources in future monitoring programs.

Trace Organic Chemicals in Biosolieds-Amended Soils: State-of-the-Science Review

The presence of trace organic chemicals (TOrCs) in municipal biosolids in the U.S. has received considerable attention by the public and scientific community over the last several years. Of particular concern is whether the presence of TOrCs in biosolids results in significant risks to public health and the environment upon land application of the biosolids. While the U.S. Environmental Protection Agency has evaluated the risks associated with dioxins present in biosolids-amended soils, to date, no other TOrCs, particularly those of emerging concern, have been subjected to complete risk assessments with respect to the land application of municipal biosolids. This study identified the scientific data gaps that should be filled if appropriate risk assessments are to be conducted. The focus of this effort was to compile data from published peer-reviewed literature that addresses the occurrence, mobility, persistence, bioaccumulation, toxicity, and microbial impacts of biosolids-borne TOrCs in soils. In addition, an evaluation of the current modeling approaches employed to evaluate the risks of biosolids-borne TOrCs was conducted. This title belongs to WERF Research Report Series . ISBN: 9781843393931 (Print) ISBN: 9781780403441 (eBook)

A multi-barrier osmotic dilution process for simultaneous desalination and purification of impaired water

Osmotically driven membrane processes use chemical potential difference between two aqueous solutions as a driving force for separation and concentration of feed streams or for recovery of energy. Forward osmosis was extensively studied in recent years and demonstrated that it can be successfully utilized in many applications of water treatment. In a new approach, the salinity difference between seawater and impaired water, such as reclaimed water, is used as a driving force for osmotic dilution of seawater before desalination. The osmotic dilution approach may provide at least four major benefits related to water and energy resources. These include lower energy desalination of seawater, multi-barrier protection of drinking water, reduction in reverse osmosis membrane fouling due to impurities in impaired water, and beneficial reuse of impaired water. The osmotic dilution process was investigated on both bench- and pilot-scales. Both secondary and tertiary treated effluents from a domestic wastewater treatment plant and impaired surface water were used as feed water to the process. Flux decline was minimal and under specific flow condition it was observed that membrane fouling was negligible. Additionally, the multiple membrane barriers provided high rejection of both organic and inorganic solutes and of trace organic chemicals.

Attenuation of total organic carbon and unregulated trace organic chemicals in U.S. riverbank filtration systems

There is increasing concern regarding the presence of unregulated trace organic chemicals in drinking water supplies that receive discharge from municipal wastewater treatment plants. In comparison to conventional and advanced drinking water treatment, riverbank filtration represents a low-cost and low-energy alternative that can attenuate total organic carbon (TOC) as well as trace organic chemicals (TOrC). This study examined the role of predominant redox conditions, retention time, biodegradable organic carbon, and temperature to achieve attenuation of TOC and TOrC through monitoring efforts at three full-scale RBF facilities in different geographic areas of the United States. The RBF systems investigated in this study were able to act as a reliable barrier for TOC, nitrogen, and certain TOrC. Temperature (seasonal) variation played an important role for the make-up of the river water quality and performance of the RBF systems. Temperatures of less than 10 °C did not affect TOC removal but resulted in diminished attenuation of nitrate and select TOrC.

Genotoxicity study of photolytically treated 2-chloropyridine aqueous solutions

2-Chloropyridine (2-CPY) has been identified as a trace organic chemical in process streams, wastewater and even drinking water. Furthermore, it appears to be formed as a secondary pollutant during the decomposition of specific insecticides. As reported in our previous work, 2-CPY was readily removed and slowly mineralised when subjected to ultraviolet (UV) irradiation at 254 nm. Moreover, 2-CPY was found to be genotoxic at 100 μg ml −1 but it was not genotoxic at or below 50 μg ml −1. In this work 2-CPY aqueous solutions were treated by means of UV irradiation at 254 nm. 2-CPY mineralisation history under different conditions is shown. 2-CPY was found to mineralise completely upon prolonged irradiation. Identified products of 2-CPY photolytic decomposition are presented. Solution genotoxicity was tested as a function of treatment time. Aqueous solution samples, taken at different photo-treatment times were tested in cultured human lymphocytes applying the cytokinesis block micronucleus (CBMN) assay. It was found that the solution was genotoxic even when 2-CPY had been practically removed. This shows that photo-treatment of 2-CPY produces genotoxic products. Upon prolonged irradiation solution genotoxicity values approached the control value.

The role of organic matter in the removal of emerging trace organic chemicals during managed aquifer recharge

This study explored the effect of different bulk organic carbon matrices on the fate of trace organic chemicals (TOrC) during managed aquifer recharge (MAR). Infiltration through porous media was simulated in biologically active column experiments under aerobic and anoxic recharge conditions. Wastewater effluent derived organic carbon types, differing in hydrophobicity and biodegradability (i. e., hydrophobic acids, hydrophilic carbon, organic colloids), were used as feed substrates in the column experiments. These carbon substrates while fed at the same concentration differed in their ability to support soil biomass growth during porous media infiltration. Removal of degradable TOrC (with the exception of diclofenac and propyphenazone) was equal or better under aerobic versus anoxic porous media infiltration conditions. During the initial phase of infiltration, the presence of biodegradable organic carbon (BDOC) enhanced the decay of degradable TOrC by promoting soil biomass growth, suggesting that BDOC served as a co-substrate in a co-metabolic transformation of these contaminants. However, unexpected high removal efficiencies were observed for all degradable TOrC in the presence of low BDOC concentrations under well adopted oligotrophic conditions. It is hypothesized that removal under these conditions is caused by a specialized microbial community growing on refractory carbon substrates such as hydrophobic acids. Findings of this study reveal that the concentration and character of bulk organic carbon present in effluents affect the degradation efficiency for TOrC during recharge operation. Specifically aerobic, oligotrophic microbiological soil environments present favorable conditions for the transformation of TOrC, including rather recalcitrant compounds such as chlorinated flame retardants.

Applying Surrogates and Indicators to Assess Removal Efficiency of Trace Organic Chemicals during Chemical Oxidation of Wastewaters

To respond to concerns associated with wastewater-derived contaminants water utilities are looking for new approaches for monitoring trace organic chemicals in conventional and advanced water treatment processes. This study examines the use of a combination of surrogate parameters and indicator compounds tailored to monitor the removal efficiency of advanced oxidation processes employed by treatment plants engaged in indirect potable water reuse programs. Potential surrogate parameters and indicator compounds, identified by reviewing previous publications and classified by their structural properties, were tested in pilot- and full-scale treatment systems. Dilantin, DEET, meprobamate, and iopromide are good indicators to assess optimized oxidation conditions while ozonating tertiary-treated wastewaters. UVA reduction, ozone byproduct formation, such as simple organic acids, and ozone exposure correlated with "sweet spot" compounds, where ozone exposure correlated with trace organic removal across five tertiary-treated wastewaters. Findings indicate that the proposed framework can serve as a conservative monitoring approach for advanced oxidation processes as well as other indirect potable reuse processes to ensure proper removal of identified and unidentified wastewater-derived organic contaminants, to detect failures in system performance, and is protective of public health.

Sources of priority substances entering an urban wastewater catchment—trace organic chemicals

The implementation of new legislation such as the Water Framework Directive (WFD) requires Member States to gain a better understanding of priority substances entering surface waters. This will include inputs from wastewater treatment works as well as from other urban, industrial and agricultural sources. There is currently a lack of available data regarding the magnitude and sources of organic priority substances entering treatment works. As a consequence the concentrations of organic priority substances including PAHs, surfactants, polybrominated diphenylethers (PBDEs), diethylhexyl phthalate (DEHP), pesticides and solvents were determined in the wastewater from an urban catchment located in the UK, as part of a project undertaken for UK Water Industry Research (UKWIR). Most organic priority substances were detected in the μg/l range. Significant variations in the concentration of linear alkylbenzene sulphonate (LAS), DEHP, PBDEs and nonylphenol ethoxylates (NPEOs), in particular, were observed for the different sources. The greatest differences were evident between new and older domestic discharges. Solvent levels varied considerably reflecting use and production within the catchment. Chloroform levels were highest in domestic effluent, while trichloroethene and tetrachloroethene were detected only in commercial samples.

Laser scanning confocal microscopic investigations of simulated nuclear waste structures

Researchers at the Department of Energy's Savannah River Technology Center are using advanced microscopy techniques to understand the effects of trace organic chemical additions on nuclear waste slurry flow properties. Trace organic chemicals, surfactants (rheology modifiers), are being used in all types of industries to modify the flow properties of various commercial chemicals. Nuclear waste treatment at the Department of Energy's weapons production facilities, Savannah River Site and Hanford Reservation, is limited by the viscosity of the nuclear waste slurries as the material is processed through a variety of waste treatment and immobilization processes. The picture was taken using a laser scanning confocal microscope.

Trace organic compounds in the marine environment

Trace organic chemicals include a range of compounds which, due to a combination of their physico-chemical properties and toxicological implications, have been described as a serious threat to the biotic environment. A global treaty to regulate the manufacture and release of some of the most persistent trace chemicals has been promulgated and signed. The marine environment is an important sink for many trace chemicals, some of which accumulate in the marine food chain and in particular in marine mammals. With respect to the global distribution of trace organic chemicals, the levels of organohalogen compounds in the Southern Hemisphere are comparatively lower for a given environmental compartment and latitude compared to the Northern Hemisphere. A debate is currently evolving about the toxicity of alternative halogen substitutions such as bromine instead of chlorine and also of mixed halogen substitution. Recently a series of potentially natural bioaccumulative and persistent organohalogen chemicals have been found in marine mammals and turtles at levels in excess of those of anthropogenic trace organochlorines including PCBs and DDE. Little is known about the sources, behaviour and effects of natural trace organic chemicals. This manuscript presents an overview on the occurrence of trace organic chemicals in different compartments of the aquatic environment. Important knowledge gaps with regards to trace chemicals in the marine environment are presented.