Environmental Engineering Reference
In-Depth Information
100
80
60
40
Particle size of Osorb-metal
0.2-2.0 mm (10-60 mesh)
0.125-0.2 mm (60-120 mesh)
<0.125 mm (>120 mesh)
20
0
Al-Osorb
Fe-Osorb Mg-Osorb Ni-Osorb Zn-Osorb
FIGURE 33.4
Removal eficiency of atrazine treated with different particle sizes of Osorb-metal composites (1% w/v)
for
1 min. Initial concentration of atrazine was 1000 μg/L.
increased in both base sand and soil mix media (a mixture of 60% sand, 20% compost, and
20% topsoil), signiicantly higher removal eficiency of nutrients was observed, achieving
99% removal with Fe-Osorb- and Zn-Osorb-amended media (Figures 33.5 and 33.6). The
results indicate that zerovalent metals in the Osorb matrix likely increased the reductive
transformation and adsorption capacity for nutrient during intermittent wetting and dry-
ing conditions created in the bioretention systems.
Removal of atrazine was also signiicantly improved in the Osorb-metal composites
amended media (Figure 33.7), in average 45% increase at the unsaturated design and 35%
increase at the saturated design, indicating that the Osorb-metal composites amended
media effectively capture and remove atrazine, even in the sand.
33.12 Field-Scale Testing
Two ield-scale bioretention systems (rain gardens), one with standard bioretention media
and one with Fe-Osorb-enhanced media, were constructed at the campus of the College
of Wooster, Ohio (Figure 33.8). The systems were tested to examine the effectiveness of
the Fe-Osorb-enhanced bioretention system over the standard system for runoff pollutant
removal. The source of runoff was the two parking lots adjacent to the systems. The irst
bioretention system has a traditional underdrainage design with typical bioretention ill
media that consists of 60% sand, 20% soil, and 20% compost, used as a standard (control).
Fill media of the second bioretention system, however, have been mixed with 1% (w/w)
of Fe-Osorb to improve treatment performance. Each bioretention system has a depth of
2.5 ft with surface area of 10 ft by 15 ft (150 ft
2
) to handle a 2.54 cm/h (1 in/h) rainfall.
In 2011, ield-scale experiments were conducted under natural and simulated runoff
events. The data show that (i) Fe-Osorb-enhanced bioretention system improved the
removal eficiency of fertilizer runoff (i.e., nitrate and phosphate) by >40% compared with
