Transfer of coliform bacteria to duckweed harvested from anaerobic baffled reactor effluent

Abstract

Efforts to recover nutrients from wastewater have drawn interest in effluent polishing with duckweed, a small angiosperm known to grow in high nutrient environments. One important consideration is that pathogens may be transferred to suspended duckweed biomass and ultimately spread into agricultural or other environmental settings. Our objective was to evaluate transfer of fecal indicator bacteria to duckweed (Lemna minor and Wolffia arrhiza) from anaerobic baffled reactor effluent. The presence of duckweed resulted in significant removal (~1.5-log) of Escherichia coli and >65% decrease in turbidity in reactors. There was E. coli transfer of ~7-log CFU/g from effluent to harvested duckweed, and viable E. coli persisted (at 3.6-log CFU/g) even after several days of biomass drying, representing a health risk for agricultural applications.