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.

Microbial risk assessment for urban pluvial flooding

Abstract: Public health risks of urban pluvial flooding have so far received little attention in technical discussions. In this paper, the results of pathogen measurements in the sewer system of Utrecht and an urban flooding experiment are presented and used in an application of Quantitative Microbial Risk Assessment, an existing risk analysis method for the quantification of infection probabilities. This method uses ingested doses of pathogenic organisms for the calculation of infection probabilities. Ingested dose estimations are based on pathogen measurements. These samples have been analysed for concentrations of Campylobacter, Cryptosporidium and Giardia. Dose-response relations from literature are used to calculate infection probabilities for flood events. The results show that mean probabilities of obtaining a Campylobacter or Giardia infection as a result of contact with urban flood water are 2.8% and 0.6% per event respectively for adults and at least 5.7% and 1.0% per event for children, respectively. Infection probabilities for Cryptosporidium are about 1000 times lower than for Giardia. The infection probabilities found indicate that the health risk of urban flooding is higher than that of swimming in recreational freshwater environments, based on a comparison to the values for ‘acceptable risk’ as defined by the WHO for bathing water.

Solids dynamics in gully pots

Abstract: Runoff entering urban drainage systems contains suspended solids, which carry pollutants and may cause blockages in downstream parts of the system (for example infiltration facilities). Suspended s...

Calibration of hydrodynamic model-driven sewer maintenance

Abstract: Sewer performance is typically assessed using hydrodynamic models assuming the absence of in-sewer defects As a consequence, hydraulic performance calculated by models is likely to be overestimated, while the real hydraulic performance of the sewer system remains unknown This article introduces the concept of ‘hydraulic fingerprinting’ based on model calibration to identify in-sewer defects affecting hydraulic performance Model calibration enables detection of changes in hydraulic properties of the sewer system Each model calibration results in a set of model parameter values, their uncertainties and residuals The model parameter values also incorporate the antecedent condition of the catchment of the event calibrated and are therefore less suitable to identify in-sewer defects The residuals on the other hand, and more specifically their absolute values, statistical properties and the correlation between residuals at different monitoring locations are suitable as indicators of the occurrence

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 $$\matrix{ {u{{\partial u} \over {\partial x}} + v{{\partial u} \over {\partial y}} = - {1 \over \varrho }{{\partial p} \over {\partial x}} + v{{{\partial ^2}u} \over {\partial {y^2}}},} \cr {0 = {{\partial p} \over {\partial y}},} \cr {{{\partial u} \over {\partial x}} + {{\partial v} \over {\partial y}} = 0.} \cr }$$