UCLA

Abstract We conducted a column study to better understand the relative effects of plants, design elements, and operating conditions on pollutant removal in stormwater biofilters in southern California under local conditions. We planted five southern California native species (Baccharis pilularis, Carex praegracilis, Juncus patens, Leymus condensatus, and Muhlenbergia rigens) in experimental biofilter columns fitted with a saturated zone and evaluated pollutant removal during weekly dosing and following a 52-day dry period. Columns planted with C. praegracilis and J. patens were also evaluated under conditions of fortnightly dosing and without the presence of a saturated zone. During weekly dosing, planted columns had a total nitrogen removal efficiency of 46% on average whereas removal was 8% in unplanted columns. B. pilularis and M. rigens performed better than other species at nitrogen removal. The presence of a saturated zone improved nitrogen removal and metal removal, but only before the 52-day dry period. With a few exceptions, local best management practice effluent concentrations limits were exceeded but performed similarly to existing southern California biofilters. Nitrogen removal decreased slightly under a fortnightly dosing frequency, which better represented rainfall event frequency in Los Angeles when compared to weekly dosing.