RESEARCH WATCH
BIODEGRADATION Bioavailability study The availability of persistent organic compounds in soils for biodegradation declines over time. The partitioning of organic compounds into organic solids or the movement of organic compounds into nanopores are two mechanisms that might explain this. P. B. Hatzinger and M. Alexander evaluated the biodegradability of phenanthrene and 4-nitrophenol sequestered in porous silica nanopores and in nonporous or~ ganic solids. Rates of biodegradation decreased as the amount of silica and the amount of substrate in silica pores increased When phenanthrene was sequestered in solid alkanes waxes and low molecular weight polymers rates markedly decreased Results suggest but cannot prove that diffusion into nanopores or partitioning into solid organic matter can limit biodeeradation in soils (Fnviran Taxirnl Chem 1997 7,(111 2215-2221)
Carbon tetrachloride removal The biodegradation of carbon tetrachloride (CT), a groundwater contaminant resistant to spontaneous degradation, can be facilitated by optimizing prevailing environmental conditions. G. Jin and A. J. Englande, Jr., performed laboratory studies to investigate biodegradation kinetics of CT by Escherichia coli K-12 under varying oxidation-reduction potential conditions. By using titanium(III) citrate as a reducing agent, significant compound degradation was observed when bacterial cultures experienced low initial oxidationreduction potential conditions By optimizing conditions >80% removal of carbon tetrachloride was achieved in 300 hours The results of this study can be used to develop an in situ system for biodegradation of chloroorganic compounds {Water Environ Res 1997 69(6) 1100-1105)
Mobility of copper in soils Knowledge of metal adsorption and complexation processes in soils is needed to predict metal solubility, speciation, and transport. P. Romkens and J. Dolfing studied the distribution of copper among low molecular weight and high molecular weight fractions of soil organic matter. Results indicate that low molecular weight, more soluble organic matter components had a greater capacity for copper binding than did the high molecular weight, less soluble fraction, which exhibited a greater affinity for copper. Addition of calcium, simulating the liming of soils, caused flocculation of most of the high molecular weight fraction and associated copper, whereas the low molecular weight components remained dissolved and bound to copper. These findings highlight the potential importance of low molecular weight organic matter components in controlling the mobility of trace metals in soils. (Environ. Sci. Technol., ,his iisue, pp. 366-369)
BIOREMEDIATION Industrial effluent cleanup The ability of microorganisms to remove heavy metals from aqueous solutions by various mechanisms has generated interest in their potential for treating industrial effluents. P. Yong and L. E. Macaskie studied the effect of increased substrate concentration on a Citrobacter species (sp.) that accumulates heavy metals as cell-bound metal phosphates in stirred-tank and plug-flow reactors (STR and PFR, respectively). A significant increase in metal re~ moval was observed for Citrobacter sp. cells in the PFR but not in the STR. Inhibition of Citrobacter phosphatase by nitrate interferes with remediation of effluents and was found to be concentration-dependent and reversible The authors developed a model to predict the decrease in flow rate needed to compensate for nitrate interference {Biotechnol Bioem 1997 55(6) 821-830)
Phosphorus removal Biological treatment systems for the removal of phosphorus can be used more effectively if rates of volatile fatty acid (VFA) production and uptake processes by different groups of bacteria are known. S. Danesh and
0013-936X/98/0932-99A$15.00/0 © 1998 American Chemical Society
J. A. Oleszkiewicz isolated and characterized two processes using a bench-scale, anaerobic sequencing batch reactor and a biological, nutrient-removal sequencing batch reactor. Reaction conditions were varied, and VFA production and uptake were evaluated. Results indicate that biological removal of phosphorus can be improved by prefermentation of degritted wastewater before nutrient removal. (Water Environ. Res. 1997,69, 1106-1101)
GREEN CHEMISTRY Composting degradable polymers The behavior of degradable polymers disposed of in waste streams has been studied, but their behavior in compost has not been well characterized. M. Day and co-workers examined degradable polymer behavior in a laboratory-scale composting system, a thermal hydrolytic environment consisting of water at 60 °C, and a thermal-oxidative dry oven environment. Results indicate that physical reorganization of polymeric structures can occur at composting environment temperatures. However, although polyethylenebased samples (compost bags)
FEB. 1, 1998 / ENVIRONMENTAL SCIENCE & TECHNOLOGY / NEWS • 9 9 A
