Particle separation from road runoff by a decentralised lamella system – laboratory tests and experiences in the field

Abstract

A new decentralised settling system based on the principle of lamella separation was developed for the treatment of road runoff. Two different laboratory test methods, the DIBt (Deutsches Institut für Bautechnik) procedure and our own approach, were applied in order to evaluate the efficiency of the system based on the separation of fine mineral particles and a mixture of mineral and organic particles, respectively. Overall efficiencies (88% after DIBt and 61% according to our own method) were comparable to results obtained for commercial systems. The lamella system was then applied in the field for 1 year to treat runoff from a road area of 420 m. The amount of solids separated that was calculated from a mass balance (10.1 kg) was consistent with the amount of sediments measured (8.6 kg). However, the average separation efficiency was only 30% in the field study. This is related to the size and composition of the particles in runoff, which are not represented well by the material used for the test procedures. It is concluded that the test methods should be improved, and that more field studies are needed in order to obtain a better understanding of the settling behaviour of particles in road runoff.

Evaluation and sizing of proprietary sedimentation devices for decentralised stormwater treatment

“…This intimates that the estimations reflect the trend that higher SLR results in lower η, but over-estimates η at a given SLR, as can be seen in Figure 4. This can be ascribed to the impact of hydraulic shortcutting and maldistribution reducing effective surface area (Boogaard et al 2017), and is noted in the literature as a common cause of underperformance in lamella separators Boogaard et al 2017;Fettig et al 2017), with a lamella separator (L4) being the worst performing device in this study (Figure 4). Studying separation efficiency as a function of hydraulic conditions and settling velocity, Luyckx et al (2005) noted that a reliable predictive model is dependent on an accurate description of hydraulic conditions, whilst settling velocity (PSD and density) influence field performance.…”

“…Hydrodynamic separators are becoming popular due to their practical benefits of being easily retrofitted into existing chambers (Lee et al 2014) and high treatment efficiencies through the use of fixed internal structures to induce both gravitational settling and advection (Fenner & Tyack 1997;Wilson et al 2009). However, stormwater professionals are often reliant on manufacturer reported removal efficiencies when assessing device performance, as there is currently no European or international standard for proprietary devices (Dierkes et al 2015) and field studies note variable device performance (Faram et al 2007;Lee et al 2014;Fettig et al 2017). Manufacturers rely on a patchwork of national and local testing protocols to provide standardised third-party confirmation of performance (Dierkes et al 2015).…”

“…The scientific literature addressing the link between technology type, performance estimation (removal efficiency at design flow rate) and experimental measurement is inconsistent, with practitioners doubting manufacturer performance claims (Pretorius 2012;Minton 2013). Studies have found little difference in performance between technology types (Boogaard et al 2017;Li & Sansalone 2022b), little difference between designs of a given technology type (Wilson et al 2009), and variability between technology types (Fettig et al 2017). Studies at low (1-16 m h À1 ) SLR have indicated the dominance of gravity separation for lamella, sedimentation pipes and hydrodynamic separators, and therefore little difference in performance (Boogaard et al 2017).…”

Simulation and optimization of a lamella settler for cattle feedlot wastewater treatment and nutrients recovery. Experimental validation in the field

“…Packed-lamella settlers, often used for enhanced sedimentation basins, have also been analyzed (Takata and Kurose, 2017). Other configurations of lamella settlers are under research, including decentralized systems for runoff treatment (Fettig et al, 2017). Scarce information is available regarding a complete analysis of both the fluid flow and solids behavior, and about the flow path influence on the lamella performance.…”