Francois Clemens

Bio: Francois Clemens is an academic researcher from Delft University of Technology. The author has contributed to research in topics: Sanitary sewer & Combined sewer. The author has an hindex of 23, co-authored 170 publications receiving 2032 citations. Previous affiliations of Francois Clemens include Norwegian University of Science and Technology & City University of New York.

Integrated real time control of SST operation at WWTP Eindhoven: Design and gain

Abstract: At the wastewater treatment plant (WWTP) Eindhoven in the Netherlands a new control for the operation of the storm water settling tank (SST) bypass of the biological treatment has been implemented taking into account the in-sewer storage of the connected catchment areas. Based on the integrated principle that the SST discharges should be either minimised (no chance of CSO spilling) or maximised (change of CSO spilling), to minimise the pollution of the surface water. The average theoretical gain of the new control, based on 35 months of measurements, was estimated to be a 40% reduction in discharged volume. Preliminary results for the practical gain, based on 4 months of measurements, show a decrease of 49%. The event mean discharge has increased from 39 to 45·10 3 m 3 . The new SST control therefore functions as intended: it prevents unnecessary discharges, while increasing the discharged volume when the SST is operated.

Emulation of a Detailed Urban Drainage Simulator to Be Applied for Short-Term Predictions

Abstract: The challenge of this study is to investigate on applicability of a data-driven Gaussian Process Emulator (GPE) technique to develop a surrogate model for a computationally expensive and detailed urban drainage simulator. The novelty is the consideration of (short) time series for the simulation inputs and outputs. Such simulation setup is interesting in applications such as Model Predictive Control (MPC) in which numerous, fast and frequent simulation results are required. Here, an emulator is developed to predict a storage tank’s volume in a small case study in Luxembourg. Three main inputs are considered as the GPE’s parameters: initial volume in the tank, the level in which the outlet pump of the tank must start to work, and the time series of expected rainfall in the upcoming 2 h. The output of interest is the total volume of the storage tank for the next 24 h. A dataset of 2000 input-output scenarios were produced using different possible combinations of the inputs and running the detailed simulator (InfoWorks® ICM). 80% of the dataset were applied to train the emulator and 20% to validate the results. Distributions of Nash-Sutcliffe efficiency and Volumetric Efficiency are presented as indicators for quantification of the emulation error. Based on the preliminary results, it can be concluded that the introduced technique is able to reduce the simulations runtime significantly while imposing some inevitable accuracy cost. More investigation is required to validate the more generic applicability of this technique for multiple outputs and interactions between different urban drainage components.

Investment decisions based on model simulations, accountability

Abstract: Since 1995, in the Netherlands guidelines have been used by practitioners in the field of urban drainage to determine the hydraulic and environmental performance of combined sewer systems, as required by the water boards responsible for quality control of surface waters. These guidelines should guarantee a certain quality level of master plans, generally produced by consultants. We checked ten representative master plans issued over the last six years on quality, verifiability and completeness. We also checked on computed output differences in relation to the allowable mass balance error of the software used. From this sample study it may be concluded that the quality of model application is generally speaking very poor; at least one cannot be sure of the quality as no data whatsoever to access the quality is presented in most cases. None of the parties involved (municipalities, consultants, water boards) seem to take accountability for the large investments based on modelling results of unknown quality. This situation should be altered by renewed interest in responsible model application, more budget for monitoring and model calibration and enforcement of water quality demands based on factual system performance and not only simulation results.

Measuring the solids loading of urban drainage systems via run off

Abstract: Sewer and urban drainage systems deal with the runoff of areas that lack infiltration capacity. During wet weather, solids that are present on the street are (re)mobilised and transported to the drainage system by the runoff. These solids and their associated pollutants can have detrimental effects on receiving water quality. This paper presents a new measurement device which has been developed to measure the inflow of solids in gully pots. This device has been applied to 100 gully pots over a period of a year, rendering a large dataset of solid inflows to the sewer. The results indicate that only 25% of solids is captured in gully pots without this device. This renders a huge potential for further optimisation of gully pot management, which is typically optimised towards prevention of blockage rather than removing a maximum amount of solids.

Water quality based RTC using UV/VIS sensors (extended abstract)

Abstract: Kallisto is a large scale research project at water board De Dommel in The Netherlands, in cooperation with several partners (Weijers et al, 2011). It consists of quantitative and qualitative continuous on line measurements and extended modelling of the WWTP (Waste Water Treatment Plant) Eindhoven, the contributing sewer systems and the river Dommel. The overall goal of the project is to optimise the performance of the total wastewater system by using impact based Real Time Control (RTC) in order to comply with the WFD (water framework directive).

Climate Change 2007: The Physical Science Basis.

Abstract: Cause, conseguenze e strategie di mitigazione Proponiamo il primo di una serie di articoli in cui affronteremo l’attuale problema dei mutamenti climatici. Presentiamo il documento redatto, votato e pubblicato dall’Ipcc - Comitato intergovernativo sui cambiamenti climatici - che illustra la sintesi delle ricerche svolte su questo tema rilevante.

Boundary Layer Theory

Abstract: The boundary layer equations for plane, incompressible, and steady flow are $$\matrix{ {u{{\partial u} \over {\partial x}} + v{{\partial u} \over {\partial y}} = - {1 \over \varrho }{{\partial p} \over {\partial x}} + v{{{\partial ^2}u} \over {\partial {y^2}}},} \cr {0 = {{\partial p} \over {\partial y}},} \cr {{{\partial u} \over {\partial x}} + {{\partial v} \over {\partial y}} = 0.} \cr }$$