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

Steffen Rommel,Brigitte Helmreich

doi:10.3390/w10121738

Abstract

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.

Highlights

Traffic area runoff is contaminated by, amongst others, wear of pavement and vehicles, leakage, and atmospheric deposition [1,2,3,4,5,6]
This study examines the de-icing salt nonlinear. Because de-icing salt (NaCl) concerning the by far greatest application rate [7,29]
Because fine solids between 0.45 μm and 63 μm (SS63) are prevalent in traffic area runoff [30,35,36,37] and showed a significant worse settling behavior, this study focused on those particles

Summary

Introduction

Traffic area runoff is contaminated by, amongst others, wear of pavement and vehicles, leakage, and atmospheric deposition [1,2,3,4,5,6]. Abrasives and de-icing salts are applied on roads to ensure traffic safety [7,8]. This application directly causes a higher load of particulate matter (PM) to be present on the road surface [8]. This PM is associated with higher concentrations of contaminants in traffic area runoff due to higher wear and tear of pavement and vehicles, as well as an increased corrosion, enhanced by de-icing salts [9,10,11]. Because most contaminants are particulate bound, an effective removal of PM from traffic area runoff needs to be considered before it is discharged into groundwater or surface water

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