Comparative copper toxicity impact and enzymatic cascade effect on Biosorption Activated Media and woodchips for nutrient removal in stormwater treatment

Copper, a commonly occurring heavy metal in stormwater runoff, was tested for its inhibitory effects on key nitrogen cycle bacteria in Biosorption Activated Media (BAM) and woodchip. The information in this paper is used to show that copper can enhance the denitrification process through enzyme cascade reactions since nitrous reductase is the enzyme responsible for the last step of denitrification and is largely dependent on copper as its cofactor. However, media characteristics are critical for assessing multi-enzymatic cascade reactions from the microbial ecology point of view. Moreover, both media showed significant copper removal through various mechanisms at 30 cm depth. The bioactivity evaluation indicates that other bacteria (fermentative bacteria, etc.) can be largely depressed with the presence of copper, hence the biofilm structure would be more vulnerable under shearing effects, which may result in holistic depression on the microbial community.