An aerobic sequencing batch reactor for 2,4,6-trinitrophenol (picric acid) biodegradation

A bench scale sequencing batch reactor (SBR) was designed and tested for degradation of 2,4,6-trinitrophenol (TNP) or picric acid-contaminated wastewater or groundwater. Under varying temperatures (25, 15 and 10 degrees C) and influent concentrations (40-200 mg/L TNP) a stable biomass was developed that was consistently capable of degrading the explosive compound to below regulatory drinking water limits (0.057 mg/L). The reactor was initially seeded with a nitroaromatic and nitramine degrading isolate Rhodococcus opacus strain JW01. Kinetic growth modeling was conducted revealing micro(max) values at 25, 15 and 10 degrees C of 0.14, 0.08 and 0.04 d(-1), while the modeled K(s) values were 0.68, 1.11 and 1.24 mg/L, respectively. Overall TNP removal efficiency in the SBR was on average > 99.9% over the 2000 hours of operation. Removal of TNP to below drinking water standards, with low residual dissolved carbon and significant release of nitrogen from the parent compound was accomplished.