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.

Passive sampling screening method using thin-layer chromatography plates.

An in situ solid-phase extraction method, thin-layer chromatography (TLC) passive sampling, was investigated as a screening method for determining the presence of organic compounds in water using laboratory experiments and field applications. The TLC passive sampler developed in this research enables the spatial and temporal distributions of organic compounds to be determined qualitatively with little expense. The materials for the sampler developed here cost dollar 1.60 each. By first identifying the areas where a pollutant is present using the TLC passive sampling screening method, total analytical costs for monitoring programs may be reduced by eliminating unnecessary conventional analyses for locations where the pollutant is not present. Two organophosphorus pesticides, diazinon and chlorpyrifos, were used as a model for the development and as a potential application of the TLC passive sampling method. Passive sampler adsorption kinetics, enrichment factors, and extraction efficiencies were determined from batch experiments with exposure times ranging from 1 h to 4 weeks. In field applications, TLC passive sampling was conducted in natural and engineered systems with two silica gel extraction media, C2 and C18. Diazinon and chlorpyrifos were detected by analyzing the adsorbed compounds by high-performance liquid chromatography with ultraviolet detection.

Hydrogenotrophic denitrification in a microporous membrane bioreactor.

Hydrogenotrophic denitrification of nitrate contaminated groundwater in a bench-scale microporous membrane bioreactor has been investigated. To prevent microbial contamination of the effluent from the reactor the nitrate-laden water treated was separated from the denitrifying culture with a 0.02 microm pore diameter membrane. Equal pressure was maintained across the membrane and nitrate was removed by molecular diffusion through the membrane and into the denitrifying culture. The system was operated with a hydrogenotrophic denitrification culture to circumvent the addition of an organic substrate to the water. Removal efficiencies ranging from 96% to 92% were achieved at influent concentrations ranging from 20 to 40 mg/L NO3(-)-N. The flux values achieved in this study were 2.7-5.3 g NO3-N m 2d(-1). The microporous membrane served as an effective barrier for preventing microbial contamination of the product water as evidenced by the effluent heterotrophic plate count of 9 (+/- 3.5) CFU/mL. The hydrogenotrophic culture was analyzed using available 16S and 23S rRNA-targeted oligonucleotide probes. It was determined that the enrichment process selected for organisms belonging to the beta subclass of Proteobacteria. Further analysis of the hydrogenotrophic culture indicated that the organisms may belong to the beta-3 subgroup of Proteobacteria and have yet to be identified as hydrogenotrophic denitrifiers.

Nutrient Limitation in a Compost Biofilter Degrading Hexane.

A laboratory-scale compost-based biofilter was operated over a six-month period to study the requirements for removal of n-hexane from air. Hexane is a relatively short chain aliphatic hydrocarbon with a high Henry's coefficient and a low water solubility. Acclimation of the biofilter was slow, but removal efficiencies around 80% were achieved after one month of operation. However, performance decreased during the next two months of operation to 50% removal efficiency. Nutrient limitation was proposed as a reason for the decrease in reactor performance. After the addition of a concentrated nitrogen solution, reactor performance increased almost immediately to >99%. Removal efficiency remained above 99% for the following two months of operation at inlet concentrations of 0.7 g/m3 (200 ppmv), at superficial bed velocities approaching 50 m/h, and empty bed residence times of about one minute. Thus, nutrient availability may well limit biofilter performance even in compost- based units. It was shown that nutrients can be added effectively in a soluble form if compost quality is poor and a method is proposed for the evaluation of compost quality.