Performance evaluation and a sizing method for hydrodynamic separators treating urban stormwater runoff

Separation of particulate matter (PM) is the most important process to achieve a reduction of contaminants present in road runoff. To further improve knowledge about influencing factors on the settling of road-deposited sediment (RDS), samples from three sites were collected. Since particle size distribution (PSD) has the strongest effect on settling, the samples were sieved to achieve comparable PSDs so that the effects of particle density, shape, fluid temperature, and deicing salt concentration on settling could be assessed using settling experiments. Based on the experimental data, a previously proposed model that describes the settling of PM was further developed and validated. In addition, RDS samples were compared to a standard mineral material, which is currently in use to evaluate treatment efficiency of stormwater quality improvement devices. The main finding was that besides PSD, particle density is the most important influencing factor. Particle shape was thoroughly described but showed no significant improvement of the prediction of the settled mass. Temperature showed an effect on PM settling; deicing salts were negligible. The proposed models can sufficiently predict the settling of RDS in settling column experiments under varying boundary conditions and are easily applicable.

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“…The PSD of the preprocessed RDSs were modeled using a Weibull cumulative probability density function [9,46,47], following Equation (1)…”

Section: Modeling Of Settling Experimentsmentioning

confidence: 99%

“…where W(d, λ, κ) = mass fraction less than d (-); d = particle diameter (µm); λ = shape parameter (-); κ = scale parameter (-) [9,46,47]. The determined λ and κ were 85.09 and 1.247 for the used PSD.…”

Section: Modeling Of Settling Experimentsmentioning

confidence: 99%

Settling of Road-Deposited Sediment: Influence of Particle Density, Shape, Low Temperatures, and Deicing Salt

Rommel

Gelhardt

Welker

2020

Water

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“…Selbig and Fienen [40] proposed the usage of the Rosin-Rammler distribution, which is equivalent to the Weibull distribution. This approach was continued by Lee et al [41]. Based on this knowledge, this method was used to generate a synthetic PSD.…”

Section: Retention Of Suspended Solidsmentioning

confidence: 99%

“…where W(d, λ, κ) = mass fraction less than d (−); d = particle diameter (µm); λ = shape parameter (−); κ = scale parameter (−) [40]. For our simulation we used λ = {9.3, 60, 116}, equal to a d 50 from 6 to 75 µm, and κ was fixed to 0.84 [41].…”

Section: Retention Of Suspended Solidsmentioning

confidence: 99%

Influence of Temperature and De-Icing Salt on the Sedimentation of Particulate Matter in Traffic Area Runoff

Rommel

2018

Water

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Stormwater quality improvement devices use sedimentation as a pre-treatment step to separate contaminant laden particulate matter (PM) from traffic area runoff. Multiple studies describe worse settling behavior during the cold season. This paper is written in response to a decreased PM retention that was observed in the cold season during a 20-month monitoring of a sedimentation tank. However, the data was insufficient to assess the two factors that influence sedimentation during the cold season—temperature and de-icing salt application. Therefore, simplified discrete particle settling models were used to determine the influence of temperature and de-icing salt. These influences were compared to other factors, like overflow rate, particle density, and particle size distribution. To calculate the effect of temperature and de-icing salt on density and viscosity, two empirical models were applied for the first time in this field. The calculations showed that de-icing salt (NaCl) had a negligible influence on the retention of PM. However, reducing the temperature from 20 °C to 5 °C was shown to decrease the total suspended solid removal efficiency by up to 8%. The order of influencing factors was found to be particle size distribution >> overflow rate > particle density > temperature.

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“…Proprietary sedimentation systems include oversized pipes (pipe sedimentation), lamella settlers, hydrodynamic separators and combinations with filtration-adsorption media. 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).…”

Section: Introductionmentioning

confidence: 99%

Evaluation and sizing of proprietary sedimentation devices for decentralised stormwater treatment

Houlker¹,

Pasing²,

Gesterding³

2022

Water Science &Amp; Technology

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Suspended solids removal is a key performance measure for proprietary stormwater treatment devices. Various technologies are available, with manufacturers claiming hydrodynamic separators offer performance advantages. However, it is important to assess manufacturers' claims. Accordingly, this study seeks to compare the performance of proprietary devices, by applying dimensional analysis to third party certification data and experimental data from uncertified devices, and determine the accuracy of a single parameter estimation (Hazen or Péclet number) of removal efficiency. Statistical analysis indicates that device performance is well described by a single parameter estimation, transitioning from Hazen (NSE = 0.81 and RMSE = 5.1%) at low surface loading rates (SLR) in all technology types (high removal efficiency), to Péclet (NSE = 0.5 to 0.61 and RMSE = 5.9% to 4.3%) at higher SLR (low removal efficiency) for hydrodynamic separators. This indicates that performance at low SLR is well explained by gravity separation in all technology types, whilst in hydrodynamic separators removal at high SLR is better explained by gravity separation plus advection. Consequently, when high (>80%) removal efficiency is required there is no performance advantage between technology types. However, when low (<50%) removal efficiency is required hydrodynamic separators offer a 33% increase in treatment area.

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Performance evaluation and a sizing method for hydrodynamic separators treating urban stormwater runoff

Cited by 9 publications

References 0 publications

Settling of Road-Deposited Sediment: Influence of Particle Density, Shape, Low Temperatures, and Deicing Salt

Settling of Road-Deposited Sediment: Influence of Particle Density, Shape, Low Temperatures, and Deicing Salt

Influence of Temperature and De-Icing Salt on the Sedimentation of Particulate Matter in Traffic Area Runoff

Evaluation and sizing of proprietary sedimentation devices for decentralised stormwater treatment

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