Abstract
The removal of particulate matter (PM) by filter media during filtration process can mitigate the pavement runoff pollution effectively. However, this process also makes the filter media prone to clogging. To better understand the size ranges of PM captured by filter media and the subsequent impact on the clogging process, filtration test and clogging test were conducted on five types of filter media. The effect of layer thickness and grain size of different filter media on particle removal efficiency was evaluated, based on the results of PM removal rate and the particle size distribution. The subsequent long-term clogging characteristics of different filter media were also investigated. The results showed that filter media presented different capabilities to capture PM, which could be enhanced by less layer thickness or finer grain size. Normally, PM with the size range of over 49 μm could be captured effectively if proper layer thickness and grain size of filter media were selected. Besides, PM removal rate was not related to the clogging resistance of filter media. Though it can capture a larger amount of PM, Vesuvianite still maintained remarkable clogging resistance. The results will be beneficial to filter media selection and system design optimization for pavement runoff treatment.
Highlights
Pavement runoff has been considered as a major pollution source to adjacent receiving watershed [1,2,3]. e pollutants in pavement runoff mainly consist of particulate matter, chemical oxygen demand (COD), nutrients and heavy metals [4], which commonly have highly polluted concentrations [5, 6]
E particulate matter (PM) in pavement runoff originates from road-deposited sediments accumulated on the pavement surfaces, which will be washed off during rainy days [13]. e concentration and the particle size distribution (PSD) of PM are highly related to the clogging phenomenon
Charters [21] investigated PSD in the untreated runoff collected from pavement, concrete roof, copper roof, etc., in New Zealand, and the results showed that pavement runoff contained much higher TSS concentration, while the peak particle size range was between 60 and 100 μm
Summary
Pavement runoff has been considered as a major pollution source to adjacent receiving watershed [1,2,3]. e pollutants in pavement runoff mainly consist of particulate matter (normally characterized by total suspended solids, TSS), chemical oxygen demand (COD), nutrients (normally characterized by total nitrogen, TN, and total phosphorus, TP) and heavy metals [4], which commonly have highly polluted concentrations [5, 6]. Charters [21] investigated PSD in the untreated runoff collected from pavement, concrete roof, copper roof, etc., in New Zealand, and the results showed that pavement runoff contained much higher TSS concentration, while the peak particle size range was between 60 and 100 μm. The PSD changes of PM in runoff treated by filter media can reflect the capability of filter media to capture PM, and infer the size ranges of captured PM which will cause clogging. Erefore, the primary objective of this study was to evaluate the capability to capture PM and the corresponding clogging characteristics of different types of filter media. The PSD changes in the untreated and treated runoff were determined by a laser particle analyzer, and the PM capture capability of the filter media was comprehensively analyzed.
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