Polyhydroxyalkanoates as a Carbon Source for Denitrification of Waters

Polyhydroxybutyrates (PHB; a bacterially produced biodegradable plastic) was used as a carbon source for biological denitrification of water. The use of a solid, non-water soluble bioplastic in the denitrification process reduces the need for monitoring and dosing of the carbon source. Denitrification rates at four different salt concentrations (0, 5, 15 and 30 ppt) using synthetic salt water were determined. The mean denitrification rates varied from 2.4 to 3.2 kg-NO₃N/m₃-day, with the highest rate in water with a salinity of 15 ppt. While differences in denitrification rates were observed, they were not statistically significant. Additionally, denitrification rates were higher at higher nitrate concentrations. The denitrification rates had no significant differences with PHA of different molecular weights. Hydrogen sulfide production was not observed in any of the studies, even 45 days after the depletion of nitrates. The mean bioplastic consumption was 2.92 ± 2.70 mg/mg of NO₃-N reduced.