Assessment of clogging phenomena in granular filter media used for stormwater treatment
- Authors: Kandra, Harpreet , McCarthy, David , Fletcher, Tim , Deletic, Ana
- Date: 2014
- Type: Text , Journal article
- Relation: Journal of Hydrology Vol. 512, no. (2014), p. 518-527
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- Description: Hydraulic performance of granular filter media and its evolution over time is a key design parameter for stormwater filtration and infiltration systems that are now widely used in management of polluted urban runoff. In fact, clogging of filter media is recognised as the main limiting factor of these stormwater treatment systems. This paper focuses on the effect of physical characteristics of filter media and flow-through rates on the clogging of stormwater filters. Five replicate experimental columns were constructed using zeolite, scoria, riversand and polymeric glass beads, and different flow-through rates were achieved using restricted outlets. The systems were dosed with semi-synthetic stormwater and the evolution of hydraulic performance and sediment removal rate was observed (for four filter media and across four flow rates) to investigate impacts of media type and flow rate. It was found that shape and smoothness of filter media grains had limited effect on clogging and sediment removal rate. All media except scoria clogged after similar volumes of stormwater but scoria-based filters were found to be highly variable in performance, most likely due to breakdown of its particles. Conversely, flow-through rate significantly affected clogging and sediment removal rate. For instance, in the case of zeolite filters, the systems with the lowest flow rate clogged after application of over 30. m of stormwater, while the unrestricted zeolite columns (with 200 times the flow rate) clogged after only 10. m of applied stormwater. At the same time, the zeolite filters with the lowest flow rate had an overall treatment efficiency of 88% compared with the unrestricted design's efficiency of 59%. Further work is needed to analyse the influence of filter bed design, stormwater inflow characteristics and drying and wetting regimes on clogging and to understand the location of the clogged material in these filters. © 2014 Elsevier B.V.
Assessment of impact of filter design variables on clogging in stormwater filters
- Authors: Kandra, Harpreet , Deletic, Ana , McCarthy, David
- Date: 2014
- Type: Text , Journal article
- Relation: Water Resources Management Vol. 28, no. 7 (2014), p. 1873-1885
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- Description: Stormwater filters are widely used in stormwater management, sometimes as standalone structures (e.g. stormwater filter beds), or as part of porous pavements, soak ways, infiltration basins and trenches. Due to the high levels of sediment present in stormwater, clogging is the main operational issue for these systems. A laboratory-based study was conducted to investigate the effect of filter bed design variables on the clogging phenomenon in non-vegetated stormwater filters with high infiltration rates. Design parameters studied include: filter media particle sizes (0.5 mm, 2 mm, 5 mm); depth of the filter bed (100 mm, 300 mm and 500 mm); and filter media packing configurations (layered or mixed). The size of filter media particles significantly impact the clogging process, as well as the overall sediment removal performance of the filters; filters with smaller particles had better sediment removal efficiency, but subsequently shorter lifespan. Deeper systems had longer lifespan compared with shallower ones, notwithstanding deeper systems removed more sediment over their life span. Having two layers of distinct sized media in the filter bed improved performance (e.g. volume of water treated; sediment removed) over the single-layered systems. However, the three-layered systems behaved similarly to two-layered systems. Mixed systems also showed improved performance, as compared with single-layered systems, and were similar to the three-layered systems. This study therefore suggests that simple modifications to a stormwater filtration system can help improve sediment removal performance and/or reduce maintenance intervals significantly, while only slightly affecting sediment removal performance. © 2014 Springer Science+Business Media Dordrecht.
Assessment of the impact of stormwater characteristics on clogging in stormwater filters
- Authors: Kandra, Harpreet , McCarthy, David , Deletic, Ana
- Date: 2014
- Type: Text , Journal article
- Relation: Water Resources Management Vol. 29, no. 4 (2014), p. 1031-1048
- Full Text: false
- Reviewed:
- Description: Hydraulic conductivity of granular filter media and its evolution over time is a key design parameter for stormwater filtration and infiltration systems that are now widely used in management of polluted urban runoff. In fact, clogging of filter media is recognised as the main limiting factor of these stormwater treatment systems. This paper focuses on the effect of stormwater characteristics on the clogging of stormwater filters. Effect of five different operational regimes has been tested in this study of sediment concentration; pollutant concentrations; stormwater sediment size; loading rate and stormwater loading/dosing regime and compared with the Base case. For each operational condition, five column replicates were tested. Results suggest that sediment concentration in stormwater is a significant parameter affecting hydraulic and treatment performance, eventually affecting longevity of these stormwater treatment systems. Further, the size of sediments (and their relation to the size of filter media grains) in stormwater was found to be an important parameter to be considered in design of coarse filters with high infiltration rates that are used for stormwater treatment. As expected, the addition of metals and nutrients had limited or no contribution to changes in hydraulic or sediment removal performance of the studied stormwater filters. Whilst loading rate was found to be an important parameter affecting the hydraulic and treatment performance of these systems, any variation in the stormwater loading regime had a limited effect on their performance. This study therefore develops an understanding of the effect of catchment characteristics on design of filters and hence their longevity and maintenance needs. © 2014, Springer Science+Business Media Dordrecht.