Organic mulch biowall for PAH contaminated groundwater remediation

Organic mulch was used as an alternative supporting material in permeable, biological, barrier walls to prevent migration of PAHs. Three types of organic mulch, cypress bark (C), hardwood bark (H) and pine bark nuggets (P) were selected as potential media to capture pollutants or to support PAH-degrading microorganisms. Among the media, the hardwood mulch was selected for biowall testing. To simulate the fate and transport of PAHs in the subsurface biowall under aerobic conditions, two lab scale mulch-biofilm column reactors were operated. Naphthalene was chosen as the model PAH in these studies and was supplied at a loading rate of 50.9 g m−2 day−1. During the initial operation period of up to 372 pore volumes, the PAH removal efficiency remained stable at over 99%, due to sorption and biodegradation. After that, the mulch-biowall system showed variable removal efficiencies, in the range of 77–99.99%.