Geert Boeije

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.

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.

Mode of action and aquatic exposure thresholds of no concern

Threshold concepts of toxicological concern are based on the possibility of establishing an exposure threshold value for chemicals below which no significant risk is to be expected. The objective of the present study is to address environmental thresholds of no toxicological concern for freshwater systems (ETNCaq) for organic chemicals. We analyzed environmental toxicological databases (acute and chronic endpoints) and substance hazard assessments. Lowest numbers and 95th-percentile values were derived using data stratification based on mode of action (MOA; 1 = inert chemicals; 2 = less inert chemicals; 3 = reactive chemicals; 4 = specifically acting chemicals). The ETNCaq values were derived by multiplying the lowest 95th percentile values with appropriate application factors; ETNCaq,MOA1-3 is approximately 0.1 microg/L. A preliminary analysis with complete MOA stratification of the databases shows that in the case of MOA1 or MOA2, the ETNCaq value could be even higher than 0.1 microg/L. A significantly lower ETNCaq,MOA4 value was observed based on the long-term toxicity information in the European Centre for the Ecotoxicology and Toxicology of Chemicals database. Application of the ETNCaq value in a tiered risk-assessment scheme may help chemical producers to set data-generation priorities and to refine or reduce animal use. It also may help to inform downstream users concerning the relative risk associated with their specific uses and be of value in putting environmental monitoring data into a risk-assessment perspective.

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.