Tobias Bleninger

Occurrence of selected estrogens in mangrove sediments

This paper presents results related to the occurrence and distribution of estrogens along the Brazilian coast. Three mangrove areas were chosen to evaluate the presence of estrogens in surface sediments of mangrove forests. The presence of estrogens was observed in all studied sites. 17-α-Ethinylestradiol (EE2), a synthetic estrogen, was the most common and has been found in higher concentration (0.45-129.78 ng/g) compared to 17-β-estradiol (E1) and estrone (E2) (both being natural estrogens). The concentrations of E1 and E2 ranged from 0.02 to 49.27 ng/g and 0.03 to 39.77 ng/g, respectively. Theoretically, under anaerobic conditions EE2 can be reduced to E1 even in environments such as sediments of mangrove forests, which are essentially anaerobic. Even if the concentrations of estrogens seem to be insignificant in some samples, the effects remain uncertain.

Dynamic coupling of near field and far field models for simulating effluent discharges

In many cases, (processed) wastewater or thermal effluents are discharged into the marine environment, rivers or lakes. To accurately determine the dispersion, recirculation and environmental impacts of outfall plumes, it is important to be able to model the different characteristics of the outfall plume in detail - from the near field (metres around the outfall) to the far field (up to kilometres away). The solution for engineering practice is to combine different types of models (near and far field models) that each focus on specific scales, with corresponding optimised resolutions and processes. However, to adequately describe the hydrodynamic processes on these different scales, it is essential to couple these models in a dynamic and comprehensive way. To achieve this, a dynamic coupling between the open-source Delft3D-FLOW far field model and the CORMIX near field expert system is proposed. This coupled modelling system is able to use the computed far field ambient conditions in the near field computations and, conversely, to use the initial near field dilution and mixing behaviour in the far field model. Preliminary results are presented to provide a first indication of the potential of the method for modelling the complete trajectory of effluent outfall plumes, allowing an accurate assessment of the environmental effects and the design of possible mitigating measures.

Management of point source discharges into rivers: Where do environmental quality standards in the new EC‐water framework directive apply?

Abstract The “combined approach” in the new EC‐Water Framework Directive (WFD) consisting of environmental quality standards in addition to emission limit values promises improvements in the quality characteristics of surface waters. However, the specification of where in the water body the environmental quality standards apply is missing in the WFD. This omission will limit its administrative implementation. A clear mixing zone regulation is needed so that the quality objectives of the WFD are not jeopardized. This need is demonstrated using the examples of point source discharges into rivers. Furthermore, water authorities will have to make increased use of predictive modeling techniques for the implementation of the “combined approach”.

Long-term hydrodynamic modeling of the Arabian Gulf

A 3-D prognostic baroclinic hydrodynamic model of the Arabian Gulf (AG) was developed using Delft3D-FLOW. The model was forced with long-term time averaged climatological data over the computational domain and long-term salinity and temperature boundary conditions applied at its tidal open boundary. The model simulation results were thoroughly validated against measured tides from 5 stations and measured currents at 4 locations in the central and southern parts. Water salinity and temperature were validated in space and time using observations spanning over 73 years from 1923 to 1996 for the AG, the Strait of Hormuz and the Gulf of Oman. The bottom flow of the AG basin at the vicinity of the Strait of Hormuz was also validated against the available measurements. Seasonal evaporation and surface density spatial distribution maps were produced and compared with available records. The developed model setup successfully generated the AG seasonal stratification and hydrographic conditions.

Coupling bacterial decay and hydrodynamic models for sewage outfall simulation

The evaluation of wastewater concentrations in coastal environments has to be accurate for water quality control. The description of the physical process in a comprehensive model is a complex task. Due to the different spatial and temporal scales involved, the use of different numerical models is required: far-field hydrodynamic models; near-field and pollutant transport models. In this paper, a coupled application of these models is described. Capabilities and limitations of modelling techniques applied to wastewater mixing and dispersion from submerged multiport discharges are discussed for environmental impact analysis. The recommended procedure combines a near-field mixing zone model, such as NRFIELD, with the Lagrangian far-field flow and water quality models within SisBaHia® (http://www.sisbahia.coppe.ufrj.br/). The results showed that the model coupling improves the description and analysis of treated wastewater discharges over large scales. This allows a more realistic evaluation of the environmental impact due to domestic sewage discharges in coastal waters.

Combining autonomous underwater vehicle missions with velocity and salinity measurements for the evaluation of a submerged offshore SWRO concentrate discharge

High salinity discharges from seawater reverse osmosis (SWRO) plants into the marine environment may adversely affect water quality in the area surrounding the outfall. In general, very little systematic information on the potential impacts from full-scale operations on marine biota is available and even less to quantify such impacts for regulatory purposes. Scientifically validated and efficient planning tools in the form of predictive models and expert systems are normally used to assist regulators with regard to possible impacts on the marine environment. Numerical modeling has always been an efficient tool for predicting wastewater discharges and also more recently for high salinity discharges into seawater. The purpose of this study was to combine a series of propulsion-driven autonomous underwater vehicle missions with velocity and salinity measurements for the effective evaluation of a submerged offshore SWRO concentrate discharge near the campus of the King Abdullah University of Science and Technology. The Cornell Mixing Zone Expert System was additionally utilized in order to assess discharge performance under different ambient velocity magnitudes. The paper therefore focuses on the evaluation of an existing SWRO desalination discharge with emphasis on the regulatory framework of the mixing zone. The objective of this case study is to develop an approach that can be followed by SWRO plant operators and environmental competent agencies for establishing regulatory mixing zones for SWRO plants in the Kingdom of Saudi Arabia and worldwide, based on robust field monitoring.

Reservoir 1D heat transport model

Thermal stratification in lakes, hydropower or drinking water reservoirs occurs mainly by the effect of temperature on water density. One-dimensional heat transport models are widely used to simulate vertical temperature profiles since vertical temperature gradients are dominant in reservoirs. Many applications have been made using one-dimensional models, however, there are still features to be improved to reproduce physical processes or allow for better data analysis. The article describes an unsteady one-dimensional heat transport model with high spatial and temporal resolution, including an energy conservation analysis of three numerical schemes: explicit and implicit finite difference and implicit finite volume methods. It is also simulated thermal diffusivity related to advection for run-of-river reservoirs. An application of the one-dimensional heat transport model (MTCR-1) is performed in Vossoroca reservoir (located near to Curitiba, Brazil), comparison with measured data and characterization of the mixing and stratification periods using physical indices are presented.

Tiered Modeling Approach for Desalination Effluent Discharges

The mixing behavior of desalination plant effluents in the receiving waters is significantly influenced by the effluent density, which is dominated by the varying effluent salinity and temperature. The dense RO (reverse osmosis) effluent flow has the tendency to fall as a negatively buoyant plume. The MSF (multi-stage-flash) effluent is distinguished by a neutral to positive buoyancy flux that causes the plume to rise. This chapter describes the principle steps to model effluent dispersion in the receiving environment and to improve discharge design and siting. The different modeling tools are described and applied for typical case studies. A modelling framework for the environmental-hydraulic design of the outfall system for desalination plants has been developed and combined with a tiered approach to facilitate discharge assessments. Furthermore, environmental regulations and opportunities for site-specific, ecologically relevant criteria are discussed. The tiers include initial screening methods, using rapid assessment tools to determine the significance of the discharge. Length-scale based flow classification, nomograms, and empirical dilution equations are applied for that. Subsequent application of mixing zone models improves the discharge design and allows for assessment of potential environmental impacts. The discharge siting is then improved by considering also water quality parameters using a combined modeling approach coupling a near-field model to a far-field model. The final tier presents a dynamically coupled modeling system, which is necessary for large discharge flows and complex environmental conditions, where a feedback mechanism is necessary to couple both models. Results indicate that the tiered approach applied to modeling methods is capable to assess potential impacts of desalination plant effluents on the receiving waters and to improve the discharge system.

Application of Randomly Firing Jet Arrays for Electrodeposition

cVA fur Wasserbau/Hydrologie/Glaziologie, 8092 Zurich, Switzerland Randomly firing jet arrays can be used for large-scale electrodeposition from dilute solutions for which tertiary current distribution prevails, for example, the electrodeposition of Cu‐In‐Se layers, which are promising compounds for thin-layer solar devices. For this type of electrodeposition, a stirring system is needed to enhance the mass-transfer rate toward the cathode. The studied stirring system is a modular jet array firing in the horizontal direction, submerged in the tank containing the electrolyte. A dilute Cu electrolyte was used to investigate and optimize the hydrodynamic conditions determined by the stirring system. Two parameters were investigated to vary the hydrodynamic conditions: the mesh of the jet nozzles and the distance between the jet nozzles and the cathode. An optimized configuration was found, allowing the jets to merge and create a homogeneous tertiary distribution. Random sequential activation of the jets was used with the optimized configuration, and the resulting copper layer exhibited higher homogeneity than those resulting from continuous activation of the jets.