Diederik Schowanek

Development of a geography-referenced regional exposure assessment tool for European rivers - great-er contribution to great-er #1

Abstract The objective of the GREAT-ER project is to develop and validate a powerful and accurate aquatic chemical exposure prediction tool for use within the EU environmental risk assessment schemes. Current techniques to estimate regional predicted environmental concentrations (PECs) use a generic multimedia ‘unit world’ approach and do not account for spatial and temporal variability in landscape characteristics, river flows and/or chemical emissions. Hence, the results are merely applicable on a generic screening level since these models do not offer a realistic prediction of actual steady-state background concentrations. A software system will be developed to calculate the distribution of predicted environmental concentrations (PECs) of down-the-drain chemicals in European surface waters on both a river and catchment area level. Data on dissolved oxygen, biological oxygen demand and ammonia will also be used to assess water quality and to provide data for calibration and verification. The system will use a Geographic Information System (GIS) for data storage and visualization, combined with simple mathematical models for the prediction of chemical fate. Hydrological databases and models will be used to determine river flows. This refined exposure assessment tool should significantly enhance the accuracy of current local and regional exposure estimation methods. The new exposure assessment methodology will integrate specific environmental information and be worked out in a geographically-referenced framework, ultimately on a pan-European scale. The initial data collection, collation and model application will be applied to two pilot study areas, representative of different hydrological and climatological situations in Europe. A blueprint of the methodology will be developed and applied to these pilot study areas, which will allow refining, optimization and verification of the system.The ultimate objective is to implement GREAT-ER for the entire European Union.This work will be performed in the second phase of the project, after the initial three years which are limited to the development of the methodology and verification in the pilot study areas.

Biodegradation of [S,S], [R,R] and mixed stereoisomers of Ethylene Diamine Disuccinic Acid (EDDS), a transition metal chelator

An in-depth biodegradation test program was executed on the hexadentate ligand Ethylene Diamine Di Succinate (EDDS). The EDDS structure contains two chiral carbon atoms, and has three stereoisomers ([R,R], [R,S]/[S,R], [S,S]). Our research has focused on the isomer mixture (i.e. 25%[S,S]; 25%[R,R]; 50%[S,R]/[R,S], as produced from the reaction of ethylene diamine with maleic anhydride) and on the single [S,S]- and [R,R]-isomers. Biodegradation screening of the 14C-labelled EDDS isomer mixture in a Batch Activated Sludge (BAS) test with various inocula revealed incomplete mineralization, up to ca. 65% after 28 days. N-(2-aminoethyl) aspartic acid (AEAA), probably the d-isomer, was identified as the major portion of the 14C-material remaining in solution. Further testing revealed that the [S,S]-isomer is rapidly and completely mineralized in all test systems. By contrast, [R,R]-EDDS remained undegraded in a Sturm (OECD 301B) test, but was very slowly biotransformed into the recalcitrant metabolite AEAA in a BAS test. The [S,R]/[R,S] form undergoes biotransformation to AEAA in both high and low biomass systems. In a sewage treatment simulation test (OECD 303) the steady state DOC removal of mixture-EDDS in a CAS test was limited to 25-35%, even after extensive pre-acclimation, while the [S,S]-isomer achieved nearly complete removal (96%). This study illustrates the importance stereospecificity may have on the biodegradation and metabolite formation of a chemical. A biodegradation scheme for the different EDDS stereoisomers is proposed.

Comparison between three different LCIA methods for aquatic ecotoxicity and a product Environmental Risk Assessment – Insights from a Detergent Case Study within OMNIITOX

Background and ObjectiveIn the OMNIITOX project 11 partners have the common objective to improve environmental management tools for the assessment of (eco)toxicological impacts. The detergent case study aims at: i) comparing three Procter &c Gamble laundry detergent forms (Regular Powder-RP, Compact Powder-CP and Compact Liquid-CL) regarding their potential impacts on aquatic ecotoxicity, ii) providing insights into the differences between various Life Cycle Impact Assessment (LCIA) methods with respect to data needs and results and iii) comparing the results from Life Cycle Assessment (LCA) with results from an Environmental Risk Assessment (ERA).Material and MethodsThe LCIA has been conducted with EDIP97 (chronic aquatic ecotoxicity) [1], USES-LCA (freshwater and marine water aquatic ecotoxicity, sometimes referred to as CML2001) [2, 3] and IMPACT 2002 (covering freshwater aquatic ecotoxicity) [4]. The comparative product ERA is based on the EU Ecolabel approach for detergents [5] and EUSES [6], which is based on the Technical Guidance Document (TGD) of the EU on Environmental Risk Assessment (ERA) of chemicals [7]. Apart from the Eco-label approach, all calculations are based on the same set of physico-chemical and toxicological effect data to enable a better comparison of the methodological differences. For the same reason, the system boundaries were kept the same in all cases, focusing on emissions into water at the disposal stage.Results and DiscussionSignificant differences between the LCIA methods with respect to data needs and results were identified. Most LCIA methods for freshwater ecotoxicity and the ERA see the compact and regular powders as similar, followed by compact liquid. IMPACT 2002 (for freshwater) suggests the liquid is equally as good as the compact powder, while the regular powder comes out worse by a factor of 2. USES-LCA for marine water shows a very different picture seeing the compact liquid as the clear winner over the powders, with the regular powder the least favourable option. Even the LCIA methods which result in die same product ranking, e.g. EDIP97 chronic aquatic ecotoxicity and USES-LCA freshwater ecotoxicity, significantly differ in terms of most contributing substances. Whereas, according to IMPACT 2002 and USES-LCA marine water, results are entirely dominated by inorganic substances, the other LCIA methods and the ERA assign a key role to surfactants. Deviating results are mainly due to differences in the fate and exposure modelling and, to a lesser extent, to differences in the toxicological effect calculations. Only IMPACT 2002 calculates the effects based on a mean value approach, whereas all other LCIA methods and the ERA tend to prefer a PNEC-based approach. In a comparative context like LCA the OMNIITOX project has taken the decision for a combined mean and PNEC-based approach, as it better represents the ‘average’ toxicity while still taking into account more sensitive species. However, the main reason for deviating results remains in the calculation of the residence time of emissions in the water compartments.Conclusion and OutlookThe situation that different LCIA methods result in different answers to the question concerning which detergent type is to be preferred regarding the impact category aquatic ecotoxicity is not satisfactory, unless explicit reasons for the differences are identifiable. This can hamper practical decision support, as LCA practitioners usually will not be in a position to choose the ’right’ LCIA method for their specific case. This puts a challenge to the entire OMNIITOX project to develop a method, which finds common ground regarding fate, exposure and effect modelling to overcome the current situa-tion of diverging results and to reflect most realistic conditions.

Adaptation of the CAS test system and synthetic sewage for biological nutrient removal: Part I: Development of a new synthetic sewage

A new synthetic medium has been developed for routine use in laboratory-scale sewage treatment simulation and biodegradation tests, such as OECD guideline 302A & 303A or ISO method 11733. The new medium, Syntho, was designed to meet the following objectives: 1) to be more representative of real sewage than the existing standard OECD synthetic sewage, 2) the COD:N:P ratio and mineral composition must allow a good degree of biological nutrient (N, P) removal, and 3) the medium should result in stable unit operation, including good sludge settling and minimal need for control actions. The IAWQ Activated Sludge Model No. 2 (ASM2,) was used to help design the medium and predict reactor performance for different possible media compositions. The results obtained with Syntho indicate that Continuous Activated Sludge (CAS) units with or without nutrient removal can be operated routinely on this feed. The new medium was also characterized by means of a respiration test. The different influent fractions applied in the model were validated, and a respiration profile indicated that Syntho is a close approximation of real sewage.

New PEC definitions for river basins applicable to GIS-based environmental exposure assessment.

By means of GREAT-ER (Geo-Referenced Regional Exposure Assessment Tool for European Rivers) aquatic chemical fate simulations can be performed for river basins. To apply the resulting digital maps with local (river stretch specific) predicted concentrations in regional aquatic exposure and risk assessment, the output has to be aggregated to a (single) value representative of exposure in the catchment. Two spatially aggregated PEC definitions are proposed for this purpose: PECinitial (unweighted aggregation of concentrations just downstream of wastewater emissions) and PECcatchment (weighted aggregation of all average stretch concentrations). These PECs were tested using simulations for two pilot study catchments (Calder and Went, UK). This confirmed the theoretical considerations which led to the definitions, and it illustrated the need for weighting to resolve scale-dependencies.

Effects of nutrient trace metal speciation on algal growth in the presence of the chelator [S,S]-EDDS

This study tests the hypothesis that the apparent toxicity of strong chelators in standard algal growth inhibition tests (e.g. method OECD 201, EC C.3., ISO 8692) is related to essential trace metal bioavailability. This hypothesis was investigated for the chelator [S,S]-ethylene diamine disuccinate ([S,S]-EDDS) and the green alga Chlorella vulgaris. Metal speciation calculations were used to help design the algal growth experiments and interpret the data. Results suggest that interaction of the chelator with trace metals alters the free metal concentration and affects algal population growth, as opposed to a direct interaction between the alga and the chelator (toxicity sensu stricto). Even low levels of [S,S]-EDDS (i.e. 3 mg l-1 or less) reduce the free p(Cu) and p(Zn) (p(Metal) = -log[Metal]) in standard OECD medium below 16 and 11, respectively, which are the minimum levels required to support algal growth. Nutrient deficiency was overcome by supplementing the medium with appropriate amounts of the trace metals Cu, Zn and Co, but not by increasing the hardness of the medium. A short-term photosynthesis inhibition experiment with the alga Selenastrum capricornutum in metal-free medium showed only a minimal effect of[S,S]-EDDS on the 14C-CO2 fixation rate. About 10% inhibition was observed at 100 mg [S,S]-EDDS l-1, i.e. the EC50 for CO2 fixation is greater than 100 mg l-1. Results from this study illustrate that the standard algal growth inhibition test is not well suited to the assessment of algal toxicity (sensu stricto) of strong chelators. The no-effect level and EC50 value are probably overestimated by at least one order of magnitude for [S,S]-EDDS. The study also illustrates the importance of speciation calculations when assessing algal inhibition by chelators.

Phosphonate utilization by bacteria in the presence of alternative phosphorus sources.

Batch and continuous culture experiments were carried out to investigate the effect of orthophosphate and p-nitrophenylphosphate on the utilization of various phosphonates as a P source by bacteria. Detailed tests with methylphosphonate as a model phosphonate and the phosphonate-degrading Pseudomonas paucimobilis strain MMM101a revealed that, in contrast with the majority of literature data, the phosphates did not suppress phosphonate utilization. Under conditions of P stress, strain MMM101a simultaneously took up both P-sources, with a preference for the phosphate-P. Study of the kinetic parameters for strain MMM101a, growing on the different P sources revealed similar, rather low, maximum growth rates (ca. 0.15 h-1). However, the affinity for orthophosphate (Ks: 0.17 μM), was more than two orders of magnitude higher than for methylphosphonate (Ks: 66 μM), which might account for the preferential uptake of orthophosphate. Cellular phosphorus yields in continuous cultures varied considerably with the conditions applied. The results suggest that phosphonate degradation can occur also in environments with substantial backgrounds of phosphate.

Comprehensive review of several surfactants in marine environments: Fate and ecotoxicity

Surfactants are a commercially important group of chemicals widely used on a global scale. Despite high removal efficiencies during wastewater treatment, their high consumption volumes mean that a certain fraction will always enter aquatic ecosystems, with marine environments being the ultimate sites of deposition. Consequently, surfactants have been detected within marine waters and sediments. However, aquatic environmental studies have mostly focused on the freshwater environment, and marine studies are considerably underrepresented by comparison. The present review aims to provide a summary of current marine environmental fate (monitoring, biodegradation, and bioconcentration) and effects data of 5 key surfactant groups: linear alkylbenzene sulfonates, alcohol ethoxysulfates, alkyl sulfates, alcohol ethoxylates, and ditallow dimethyl ammonium chloride. Monitoring data are currently limited, especially for alcohol ethoxysulfates and alkyl sulfates. Biodegradation was shown to be considerably slower under marine conditions, whereas ecotoxicity studies suggest that marine species are approximately equally as sensitive to these surfactants as freshwater species. Marine bioconcentration studies are almost nonexistent. Current gaps within the literature are presented, thereby highlighting research areas where additional marine studies should focus.

Quantitative in situ monitoring of organohalogen compounds in domestic sewage resulting from the use of hypochlorite bleach

A field monitoring program was carried out on the sewage of five large apartment blocks in the city of Parma, Italy, to verify under realistic conditions existing laboratory data and model calculations on organohalogen formation by domestic hypochlorite (NaOCl) bleach usage. The average adsorbable organic halogens (AOX) level was determined for three distinct experimental phases: an “undisturbed period,” a “no bleach period,” and a “controlled bleach usage period.” The study involved participation of the site inhabitants in the second and third phases. In line with what could be predicted from the hypochlorite chemistry, an effect of the use of hypochlorite bleach on the AOX concentration in domestic sewage was detected. In a laboratory simulation conducted in parallel with the field study, the degree of NaOCl-to-AOX conversion ranged from 0.75 to 2.25% (w/w). The degree of conversion in the field study itself was of the order of 1.5% (or 0.075% when expressed for a typical bleach product containing 5% NaOCl). Under the specific conditions of the site, the difference in average AOX concentration in sewage between the “no bleach” and the “undisturbed” bleach use period was of the order of 37 μg·1−1 (P < 0.05). The average bleach-related AOX emission at the study site was around 7 mg·(inhabitant·day)−1. Overall, these figures correspond well with existing literature data. Linking the measured amounts of AOX with available ecotoxicity data for treated domestic effluents and their organohalogen constituents, it can be considered unlikely that the organohalogens formed by domestic bleaching will exert or trigger any adverse environmental effect.

Adapting SimpleTreat for simulating behaviour of chemical substances during industrial sewage treatment

The multimedia model SimpleTreat, evaluates the distribution and elimination of chemicals by municipal sewage treatment plants (STP). It is applied in the framework of REACH (Registration, Evaluation, Authorization and Restriction of Chemicals). This article describes an adaptation of this model for application to industrial sewage treatment plants (I-STP). The intended use of this re-parametrized model is focused on risk assessment during manufacture and subsequent uses of chemicals, also in the framework of REACH. The results of an inquiry on the operational characteristics of industrial sewage treatment installations were used to re-parameterize the model. It appeared that one property of industrial sewage, i.e. Biological Oxygen Demand (BOD) in combination with one parameter of the activated sludge process, the hydraulic retention time (HRT) is satisfactory to define treatment of industrial wastewater by means of the activated sludge process. The adapted model was compared to the original municipal version, SimpleTreat 4.0, by means of a sensitivity analysis. The consistency of the model output was assessed by computing the emission to water from an I-STP of a set of fictitious chemicals. This set of chemicals exhibit a range of physico-chemical and biodegradability properties occurring in industrial wastewater. Predicted removal rates of a chemical from raw sewage are higher in industrial than in municipal STPs. The latter have typically shorter hydraulic retention times with diminished opportunity for elimination of the chemical due to volatilization and biodegradation.