Homepage of  Prof. W. Bauwens Towards the " good ecological status” in river Zenne: re-evaluating Brussels’ wastewater management
Updated : January 9, 2009
	Funding : Period : www : Publications :	Environment Impulse Programme of the Brussels-Capital Region 05/2009 - 04/2012
	Background and objectives Sewage contaminated river ecosystems, such as the Zenne River in Brussels, receive high loads of organic material, sediments, pollutants like trace metals and pathogenic micro-organisms with severe consequences for the river’s ecology and increased sanitary risks for riparian population. In Brussels, in spite of large investments made for the construction and maintenance of sewage collectors and WWTPs, specific problems still persists and water quality is still very poor. We are far from the objective of ‘good ecological status’ reclaimed for 2015 by the European Water Framework Directive (WFD2000). An optimization of Brussels sewage management is thus crucial but its interactions with the ecological status of the river are complex. This project aims at the evaluation of the effects of Brussels’ wastewater management on the ecological functioning of the Zenne River, with the intention to provide expert advice on the optimisation of future sewage management actions in Brussels. We will develop the appropriate analytical tools allowing easy monitoring of specific environmental variables (sensors for toxic metals, an automatic measuring system for harmful bacteria and a surface water image analysis system for the evaluation of sediment loads) .Additionally we will develop a model that will allow us to explore various scenarios representing possible future wastewater management options in Brussels. Project partners · Vrije Universiteit Brussel o ANCH: Faculty of Sciences - Chemistry Department - Lab for Analytical and Environmental Chemistry (Nathalie Brion, Marc Elskens and Willy Baeyens) o HYDR: Faculty of Engineering Sciences - Department of Hydrology and Hydraulic Engineering (Willy Bauwens and Margaret Chen) · Université Libre de Bruxelles o ESA: Faculty of Sciences - Ecole Interfacultaire de Bioingénieurs - Ecology and Aquatic Systems (Pierre Servais) o WPC: Faculty of Applied Sciences - Department of Water Pollution Control (Michel Verbanck) Work packages · WP1: Collection of existing data for the last 20 years (WPC) · WP2: Sampling method development and/or optimisation (ANCH) o Task 1: Development of an automatic monitoring station with specific sensors for trace metal assessment (ANCH) o Task 2: Development of an automatic measuring tool for faecal bacteria (ESA) o Task 3: Development of a standard method for the determination of the biodegradable fraction of organic matter (ANCH) o Task 4: Use of deformed water surface images to deduce friction effects and particle fluxes in an alluvial river (WPC) o Task 5: Designing and testing of an automatic measuring cabin for the continuous monitoring of water quality (HYDR) · WP3: Determination of material loads and dynamics in the river Zenne and in the wastewater: temporal and spatial variability (ESA) o Task 1: Material loads § Task 1.1 Basic physicochemical parameters (WPC and HYDR) § Task 1.2. Carbon, nitrogen and phosphorus pools in the river water and in the wastewater effluents (ANCH, ESA, WPC) § Task 1.3. Determination of Cu, Cd, Zn, Pb and As (ANCH) § Task 1.4. Suspended solid loads (HYDR) § Task 1.5. Pathogenic micro-organisms (ESA) o Task 2: Material dynamics § Task 2.1. Characterization of the Organic matter: biodegradability and oxygen demand (ESA, WPC, ANCH) § Task 2.2. Nitrogen transformation rates (nitrification, ammonification, uptake) (ANCH) § Task 2.3. Carbon transformation processes (ANCH) § Task 2.4. Bacterial production and respiration (ESA) § Task 2.5. Fate of faecal bacteria in the river (ESA) · WP4: Development and validation of models (HYDR) o Task 1: Development of a hydrologic-hydraulic model for the river Zenne (HYDR) o Task 2: Development of a C-N-P model (HYDR) o Task 3: Development of a sediment transport model (WPC) o Task 4: Developemnt of a faecal bacteria model (ESA) o Task 5: Development of a metal transport-exchange-transformation model (ANCH) o Task 6: Integration of the different models (HYDR) o Task 7: Model application (ANCH) · WP5: Creation of an expert consortium for water managers (ANCH) Tasks coordinated and/or executed by HYDR WP3: Determination of material loads and dynamics in the river Zenne and in the wastewater: temporal and spatial variability (ESA) WP3 - Task 1.1: Basic physicochemical parameters Basic physico-chemical parameters will be determined off line at a number of stations during sampling campaigns, using specific sensors for pH, conductivity, oxygen and temperature. Simultaneously, water flow velocities will be measured at selected stations both vertically along the water column and longitudinally along the river. WP3 - Task 1.4: Suspended solid loads Suspended solid load and its transport are one of the key parameters to understand the dynamic and complicated hydrological systems of the Zenne River. Transport, distribution and deposition of suspended solid are of primary importance. Suspended solid influences the transport of mass load and transmission of energy through the water column. Sedimentation of suspended solid is a major pathway for transfer of nutrients from surface water to the bottom; thereby it plays a crucial role in nutrient budgets. Suspended solid also consists of various particles that offer abundant surface area for adsorption of numerous hydrophobic substances, such as chemical elements including trace metals, organisms and some contaminants and may go through cycles of adsorption and desorption with continuous mixing, deposition and resuspension under various river flow conditions. Despite the various research programs on the Zenne River, there is still scarcity of data and information on the physical processes controlling the sediment transport. Systematic field study is therefore crucial for the development of numerical models for hydraulic as well as sediment transport and sustainable management strategies. Measurements will be focused on variations of water depth, flow velocity and suspended solid concentration both vertically along the water column and longitudinally along the river. Particle size analysis will be performed on selected samples to determine size spectra of suspended solid. Attempt will be made to interpret relation between particle size, flow condition, trace metals and microbial activities. WP4: Development and validation of models (HYDR) The assessment of the integrated water quality for river basins in the framework of the analysis of different management scenario's requires numerical models for the different aspects of the problem (water quantity, physico-chemistry, microbiology,...). While many models already exist for subcomponents of the system, the integration of these models poses a problem. The solution proposed by the EU consists of a common standard for allowing the exchange of data between different submodels: the OpenMI standard. This standard will be adopted by the project, which will not only allow to link the different new model components that will be developed in this project (e.g. the sediment model, the bacterial model, the metal model) but will also make it possible for other users to adopt these new developments. WP4 - Task 1: Development of a hydrologic-hydraulic model for the river Zenne (HYDR) The water quantity and the water fluxes are key parameters to the modelling of all the fluxes and processes related to the pollutants. With this respect, the Zenne basin consists of a quite complex system, consisting of the following interacting subsystems: the actual river, the canal and the different sewer systems and waste water treatment plants along the river. The situation is further complicated by the fact that the flow regime in the downstream part of the river is influenced by tidal cycles. As these systems interact with each other (e.g. river flows are diverted to the canal upstream of Brussels but part of this flow re-enters the river downstream; the sewer system of Brussels emits to the river, but the river may also cause backwater or even return flow in the sewer system), an integrated hydraulic model needs to be developed, including all the major components of the system. The hydraulic model will consist of the River Zenne between Lembeek and the mouth of the river, the canal between Ittre and Kapelle-op-den-bos and the major collectors of the sewer system in Brussels (as far as they are influenced by the river or the canal). The modelling of the inflows will be performed by means of a semi-distributed hydrologic model (SWAT) for the rural basins and by means of a simplified sewer model (COSIMAT) for the sewer system. The latter will also include a simplified model for the representation of the waste water treatment plants. While the model develop can rely upon previous work on the hydrologic modelling of the Zenne basin (e.g. van Griensven, 2002), the different subcomponents need to be integrated, expanded and actualized. With regard to the integration, it is referred to Task 6. The expansion includes the use of radar data for the assessment of the areal distribution of the rainfall, for which collaboration will be sought with the Royal Meteorological Institute. The actualization will include an update of the land use in the basin, based on remote sensing data. For the calibration of the models, data of the Brussels and Flemish Region will be used. WP4 - Task 2: Development of a C-N-P model The modelling of the carbon, nitrogen and phosphorous cycles requires the modelling of the emissions of these compounds and of the in-stream processes. With regard to the latter, the Qual2E approach is most commonly used. One of the problems with this approach however is the fact that the state variables of this model are different from the state variables used in the modelling of wastewater treatment plants. To overcome this and other limitations, the River Water Quality Model (RWQM) - an adaptation of the Activated Sludge Model for wastewater treatment plants to the river environment - will be used in the framework of this project. The emission of the diffuse sources of C, N and P will be modelled by means of the SWAT model, while the above mentioned model for sewers and WWTP will be extended with water quality modules, compatible with the RWQM approach. As for the previous task, this task can build on previous work that needs to be actualised and extended. The major extension concerns a reformulation and subsequent calibration of the RWQM component that was previously developed in discrete form and needs to be implemented in a finite difference scheme. The calibration of the models will be based on data of the Brussels and Flemish Region and on data of the measurement campaigns (WP3). WP4 - Task 6: Integration of the different models (HYDR) The different models will be linked to each other through OpenMI. The OpenMI standard is a model component interface definition for computational models in the water domain. Model components that comply with this standard can be configured to exchange data during computation (at run-time). This means that combined systems can be created, based on OpenMI-compliant models from different providers. The standard supports two-way links where the models mutually depend on calculation results from each other. Linked models may run asynchronously with respect to time steps and data represented on different geometries (grids) can be exchanged. The application of open MI requires that each of the models discussed above should be adapted, to comply with the open MI standard. Task 6 deals with the development of the OpenMI interface. The HYDR team BAUWENS Willy, coordinator of the HYDR team, team leader for WP4. CHEN Margaret, guest professor, team leader for WP3. JOSSENT Jiri, Civil Engineer, PhD researcher, expert on SWAT. DAMS Jef, MSc in Water Resources Engineering, PhD researcher (IWT), expert on the use of remote sensing data for land use determination. NN1, researcher (MSc Informatics), setting of the guidelines for the open MI software development NN2, researcher (MSc Engineering), research on suspended sediment transport NN3, researcher (MSc Engineering), research on catchment and urban drainage modelling NN4, researcher (MSc Bio-engineering or similar), research on river water quality modelling NN5, researcher (MSc Informatics or similar), research on OpenMI.