Laboratory study of stormwater biofiltration in low temperatures: total and dissolved metal removals and fates

The filter material accounts for the majority of metal removal in stormwater bioretention systems.

“However, the filter material accounts for the majority of metal removal (Muthanna et al., 2007; Blecken et al., 2009, Blecken et al., 2011) and hence, filter material composition is crucial for achieving effective dissolved metal treatment.”

Several pilot-scale studies have shown LTU top-layer to be an efficient metal adsorbent.

“Several pilot-scale studies (Blecken et al., 2011; Søberg et al., 2017) have shown this material to be an efficient metal adsorbent.”

The bioretention systems examined in the cited studies were relatively young (<2 years) and found metals to be adsorbed in the top 5 cm of the filter material, so these systems were far from saturated with metals.

“Moreover, the bioretention systems examined in the cited studies (Muthanna et al., 2007; Hatt et al., 2008; Blecken et al., 2011; Wang et al., 2017; Søberg et al., 2017) were relatively young (<2 years) and found metals to be adsorbed in the top 5 cm of the filter material. Hence, these systems were far from saturated with metals.”

Conflicting results have been observed in previous studies regarding removal of dissolved metals in stormwater bioretention systems: some found efficient retention, while others found substantial leaching.

“Conflicting results have been observed in previous studies regarding removal of dissolved metals in stormwater bioretention systems. Some have found that dissolved metals are efficiently retained (e.g. Blecken et al., 2011; Wang et al., 2017), while others have found substantial leaching (e.g. Muthanna et al., 2007; Hatt et al., 2008; Søberg et al., 2017).”

LTU-TOP efficiently removed metals in pilot-scale bioretention facilities under various ambient conditions, despite showing very low adsorption capacities in the present study.

“Although it showed very low adsorption capacities in the present study (Fig. 2), LTU-TOP efficiently removed metals in pilot-scale bioretention facilities under various ambient conditions (e.g. Blecken et al., 2009; Blecken et al., 2011; Søberg et al., 2017).”