Abstract
Contaminated runoff stormwater from urban environments carries several contaminants to water bodies, thereby affecting the health of living beings and ecological systems. Among all the contaminants, heavy metals possess high toxicity and impact water quality. The stormwater management through green infrastructures composed by adequate materials can provide an excellent solution, simultaneously ensuring the appropriate hydraulic performance and contaminant removal rate. The proposed research aims at the elimination of heavy metals (i.e. Ni, Cu, Zn, Cd and Pb) through column experiments by selecting four possible and novel treatments for urban stormwaters. Two lightweight aggregates (Arlita and Filtralite) were tested separately and in combination with CaCO3. The study determines the efficiency and lifetime of each treatment by varying the interaction time between the filter materials and contaminated water and the type of filter. The observed removal mechanisms were closely related to the changes in pH due to the interactions between water and different materials. The reductions in heavy metal concentrations depend on the type of heavy metal, interaction time and type of filter material. Results indicate that the combined use of CaCO3, Arlita and Filtralite did not improve the removal rates of heavy metals. However, it decreased the efficiency of the decontamination process. The significance of this study lies on the removal efficiency of Arlita and Filtralite as decontamination treatments. Both the tested lightweight aggregates led to a considerable decrease in the heavy metal concentrations in urban runoff stormwater although Filtralite was particularly efficient. After 4 weeks, the treatments were still successfully reducing and stabilising 99% of the heavy metals in the contaminated stormwater. These results confirm that the lifetime of the tested lightweight aggregates is adequate and emphasise, as a novel application of these materials, on their feasibility for the improvement of urban stormwater quality.
Highlights
Runoff is one of the main components of the water cycle
This study aims to evaluate the removal efficiency of heavy metals from urban runoff stormwater using two Lightweight aggregates (LWAs) classified as light-expanded clay aggregate (LECA) which include commercial trademarks such as Arlita or Filtralite
We can conclude that in dynamic experiments a brief time of interaction between the particles of Arlita or Filtralite, and the aqueous solutions was sufficient to reduce the concentration of heavy metals by up to > 74%, using the different filter materials (i.e. Arlita, Filtralite and CaCO3)
Summary
Runoff is one of the main components of the water cycle. In partic ular, surface runoff is extremely important in urban areas because their characteristic impervious features contribute to an increase in the water runoff volumes and negatively affect the hydrologic cycle in such en vironments (Wang et al, 2017a). Contaminated stormwater is one of the main elements responsible for non-point source water pollution (Pitt et al, 1995; Zgheib et al, 2012). Flooding has been traditionally considered as the most important outcome of such failures; worldwide communities have addressed the problem of stormwater quality by proposing strategies and novel infrastructures (Fu et al, 2019; Haghighatafshar et al, 2018; Hamouz et al, 2018). Pollution problems caused by runoff stormwater have been increasingly attracting concern. It has been considered how runoff stormwater can carry contaminants from urban environments to surface water sources (Ortega Sandoval et al, 2019).
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