BIOLOGICAL AND CHEMICAL MINERALIZATION OF PYRIDINE

A comparison was made between biological and chemical mineralization o f pyridine, an N-heterocyclic pollutant, in a liquid culture and a slu rry of ground water and subsurface sediment. A bacterial culture of an Alcaligenes sp. that degrades pyridine was found to be more effective at oxidizing [2,6-C-14]pyridine to (CO2)-C-14 than Fenton's reagent. Alcaligenes sp. converted 73.1% of the C-14-labeled pyridine to (CO2)- C-14, whereas the Fenton reagent converted 65.6% of the compound. In t he case of bacteria, the remaining chemical was incorporated primarily into biomass (9.2%), whereas the remaining pyridine was converted to unidentified products (16.3%) by the Fenton reagent. However, based on chromatographic analysis, these compounds were not mono-hydroxylated pyridines. Mineralization of pyridine by Fenton's reagent was affected by the concentration of H2O2 and by the concentration and oxidation s tate of available iron. Maximal mineralization occurred at a concentra tion of more than 0.15% H2O2 (44 mM), 1 mM Fe3+, or 2 mM Fe2+. Further more, the rates of both microbial and chemical mineralization were inf luenced by the initial pyridine concentration. Maximum specific rates of mineralization were 6.5 mug/h/mg biomass for the bacteria and 2.7 m ug/h/mg Fe2+ for the Fenton reagent. The feasibility of using Fenton's reagent for treating ground water and subsurface sediments polluted w ith pyridine was found to be limited, because only 24.5% of the pyridi ne was converted to CO2. In contrast, when cultures of the Alcaligenes sp. were used to treat ground water, as much as 54.4% of the labeled compound was mineralized to (CO2)-C-14.