Suspended solids transport: an analysis based on turbidity measurements and event based fully calibrated hydrodynamic models

Abstract

Modelling suspended solids transport is a key issue for predicting the pollution load discharged by CSOs. Nonetheless, there is still much debate on the main drivers for suspended solids transport and on the modelling approach to be adopted. Current sewer models provide suspended solids transport models. These models, however, rely upon erosion-deposition criteria developed in fluvial environments, therewith oversimplifying the sewer sediment characteristics. Consequently, the performance of these models is poor from a theoretical point of view. To get an improved understanding of the temporal and spatial variations in suspended solids transport, a measuring network was installed in the sewer system of Loenen in conjunction with a hydraulic measuring network from June through December 2001. During the measuring period, 15 storm events rendered high-quality data on both the hydraulics and the turbidity. For each storm event, a hydrodynamic model was calibrated using the Clemens' method. The conclusion of the paper is that modelling of suspended solids transport has been and will be one of the challenges in the field of urban drainage modelling. A direct relation of either shear stress or flow velocity with turbidity could not be found, likely because of the time varying characteristics of the suspended solids.

Relationship between turbidity and total suspended solids concentration within a combined sewer system

“…Recent studies have demonstrated how it can be used to control and evaluate effiuent quality (Langeveld et al 2005;Lawler et al 2006), but it must be emphasized that the use of suitable methods is mandatory to obtain reliable and accurate continuous turbidity measurements within the sewer system over short time steps (Joannis et al 2008).…”

Efficiency of a turbidity-based, real-time control strategy applied to a retention tank: a simulation study

“…The development potential of quality-based RTC strategies bowever is constrained by a lack of available quality data in sewer systems. Recent studies bave doi: lü,2166/wst,20U,545 demonstrated the use of continuous turbidity measurements in monitoring and assessing sewer system effluent quality (Langeveld et al 2005;Joannis et al 2007). Turbidity is well correlated witb suspended solids (SS) in sewer systems (Ruban et al 2001;Mels et al 2004;Fletcber & Delefic 2007;Lacour et al 2009), and SS are recognised as tbe primary source of pollution transfer witbin sewer systems (Chebbo et al 1995;Ashley et al 2005).…”

Identifying Critical Elements in Sewer Networks Using Graph-Theory

“…Both systems have been used several times in other studies and are also extensively calibrated [17][18][19][20]. Table 1 shows the characteristics and Figures 1 and 2 show the layout of the systems.…”