Bacterium Providencia rettgeri YL was found to exhibit an unusual ability to heterotrophically nitrify and aerobically denitrify various concentrations of ammonium (NH4+-N). In order to further understand its removal ability, several experiments were conducted to identify the growth and ammonium removal response at different carbon to nitrogen (C/N) mass ratios, shaking speeds, temperatures, ammonium concentrations and to qualitatively verify the production of nitrogen gas using gas chromatography techniques. Results showed that under optimum conditions (C/N 10, 30°C, 120 r/min), YL can significantly remove low and high concentrations of ammonium within 12 to 48 h of growth, respectively. The nitrification products hydroxylamine (NH2OH), nitrite (NO2-) and nitrate (NO3-) as well as the denitrification product, nitrogen gas (N2), were detected under completely aerobic conditions.
The performances and kinetic parameters of Fenton oxidation of 2,4-and 2,6-dinitrotoluene(DNT)in water-acetone mixtures and explosive contaminated soil washing-out solutions were investigated at a laboratory scale.The experimental results show that acetone can be a significant hydroxyl radical scavenger and result in serious inhibition of Fenton oxidation of 2,4-and 2,6-DNT.Although no serious inhibition was found in contaminated soil washing-out solutions,longer reaction time was needed to remove 2,4-and 2,6-DNT completely,mainly due to the competition of hydroxyl radicals.Fenton oxidation of 2,4-and 2,6-DNT fit well with the first-order kinetics and the presence of acetone also reduced DNT’s degradation kinetics.Based on the comparison and matching of retention time and ultraviolet(UV)spectra between high performance liquid chromatography(HPLC)and standards,the following reaction pathway for 2,4-DNT primary degradation was proposed:2,4-DNT→2,4-dinitro-benzaldehyde→2,4-dinitrobenzoic acid→1,3-dinitrobenzene→3-nitrophenol.
