Influence of intermittent wetting and drying conditions on heavy metal removal by stormwater biofilters.
Biofiltration is a technology to treat urban stormwater runoff, which conveys pollutants, including heavy metals. However, the variability of metals removal performance in biofiltration systems is as yet unknown. A laboratory study has been conducted with vegetated biofilter mesocosms, partly fitted with a submerged zone at the bottom of the filter combined with a carbon source. The biofilters were dosed with stormwater according to three different dry/wet schemes, to investigate the effect of intermittent wetting and drying conditions on metal removal. Provided that the biofilters received regular stormwater input, metal removal exceeded 95%. The highest metal accumulation occurs in the top layer of the filter media. However, after antecedent drying before a storm event exceeding 3-4 weeks the filters performed significantly worse, although metal removal still remained relatively high. Introducing a submerged zone into the filter improved the performance significantly after extended dry periods. In particular, copper removal in filters equipped with a submerged zone was increased by around 12% (alpha=0.05) both during wet and dry periods and for lead the negative effect of drying could completely be eliminated, with consistently low outflow concentrations even after long drying periods.
Blecken
Godecke-Tobias
GT
Urban Water, Department of Civil, Mining and Environmental Engineering, Luleå University of Technology, Luleå, Sweden. godble@ltu.se
Zinger
Yaron
Y
Deletić
Ana
A
Fletcher
Tim D
TD
Viklander
Maria
M
D002104:Cadmium / Q000302:isolation & purification; D003300:Copper / Q000302:isolation & purification; D005374:Filtration / Q000295:instrumentation; D007854:Lead / Q000302:isolation & purification; D019216:Metals, Heavy / Q000302:isolation & purification*; D013997:Time Factors; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000302:isolation & purification*; D018508:Water Purification / Q000295:instrumentation / Q000379:methods*; D015032:Zinc / Q000302:isolation & purification
D019216:Metals, Heavy; D014874:Water Pollutants, Chemical; D002104:Cadmium; D007854:Lead; D003300:Copper; D015032:Zinc