MITIGATING START-UP PHOSPHORUS FLUSHING FROM WOODCHIP DENITRIFICATION BIOREACTORS: DETERMINING THE PHOSPHORUS BALANCE

Abstract

Nutrient pollution from agricultural sources is a critical issue in the 21ˢᵗ century. The goal of this study was to determine the magnitude and extent of woodchip phosphorus leaching from woodchip bioreactors, a technology used to treat high-nitrate waters. A 24-dy batch test showed phosphorus leaching occurred rapidly upon initial immersion of the woodchips, with a potential maximum of 30 mg of total phosphorus leached per kg of dry wt. woodchip. Operation of four pilot-scale bioreactors showed bioreactors removed rather than leached total phosphorus; however, dissolved reactive phosphorus was eluted from each of the four flow treatments albeit for different durations. The biosolids in the wastewater were likely a larger contributor to eluted phosphorus than the woodchips. To minimize negative potential effects of filtered biosolids, pre-filtration to remove solids or post-filtration to remove phosphorus should be incorporated into the treatment train if woodchip bioreactors are used to treat this type of wastewater.