RESEARCH WATCH
BIOREMEDIATION Aerobic DBE treatment 1,2-Dibromoethane (DBE) is a potentially carcinogenic environmental contaminant of soil and groundwater. Most DBE biodegradation studies have been performed under anaerobic conditions with pollutants in the parts-per-billion range. L. M. Freitas dos Santos and colleagues investigated the potential for aerobic degradation of DBE, which has distinct advantages. They used a mixed bacterial culture, selected and enriched for mineralizing DBE and DBE concentrations ranging up to 1 g/L. Complete mineralization of DBE occurred The cultures also degraded other halogenated compounds including bromoethanol which had not been reported as biodegradable beforp This findint? could lead to aerobic remediation s y s t e m s for DBE nr o t h e r h a l o e e nateri r o m p o u n d s {Ann] Envimn Mirrnhinl 199R fiP 4fi7IS-77)
Enhanced PCP degradation Certain microorganisms degrade pentachlorophenol (PCP) under test conditions and show potential for bioremediation of contaminated soils, but they work poorly in actual PCP-contaminated soil. R. Miethling and U. Karlson investigated accelerating mineralization of PCP in soil by inoculation with two organisms, Mycobacterium chlorophenolicum PCP 1 and Sphingomonas chlorophenolica RA2. Spiked concentrations of 30 mg/kg and 100 mg/kg were used for each organism and compared with PCP mineralization by indigenous bacteria Inoculation with S chlorophenolica RA2 under specific conditions substantially decreased mineralization at 30 mg/kg and effective than uninoculated soil at 1D0 rr\(j/]cQ Inoculation with M chlorophenolicum PCP 1 rpQlllted in only slight increases r o m n a r e d with u n i n o n i l a t e d soil (Ann! rnn Mirrnhinl lQQfi K? 4^Kl-fifil
A better way to quantitate Analytical chemists move through two stages in performing quantitative determinations: first they decide whether a substance is present in a sample and then whether the concentration is high enough to quantitate. The first step depends on a compound's detection limit and the second on its quantification limit. R. D. Gibbons and co-workers propose an alternative minimum level (AML), a new method for calculating the quantitation limit. It uses measurements at multiple spike concentrations. Unlike earlier methods, it directly models the relationship between variability and concentration and can incorporate variability from different laboratories, instruments, and analysts. Consequently, results are unaffected by the choice of spike concentration. The report includes detailed illustrations of computing AML using EPA research data on ICPMS Method 1638 for cadmium in reagent water. (Environ. Sci. Technol., ,his issue, 2001-77)
Dioxins and white rot fungi Polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) are well-established environmental hazards that generally resist microbial degradation. S. Takada and colleagues investigated use of a white rot fungus, Phanerochaete sordida YK-624, to degrade the compounds. Mixtures of most toxic congeners of PCDD and PCDF were studied in a stationary, lownitrogen medium, and degradation rates were compared with those of Phanerochaeee chrysosporium. Degradation by P. sordida YK-624 ranged between 40% and 76% for PCDDs and 45% and 70% for PCDFs Results demonstrated that both P. sordida YK-624 and P chrysosporium substantially degraded the mixtures of PCDD a n d PCDF {Ann] Fnvimn rrnhinl 1 QQfi f\"? 43?^—?R\
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BIOTREATMENT Biofilter microbes Previous research has established the spatial distribution of microorganisms in biofilters, but there are little qualitative data on microbial habitats inside biofilters. T. S. Webster and co-workers studied microbial populations during biofiltration of airstreams containing hydrogen sulfide and volatile organic com-
3 0 0 A • VOL. 31, NO. 7, 1997 / ENVIRONMENTAL SCIENCE & TECHNOLOGY / NEWS
pounds (VOCs) at a municipal wastewater facility. The filters contained granular-activated carbon and yard-waste compost. Microbes in both media showed increased densities and varying degrees of environmental stress and were dominated by Gram-negative bacteria. Decreases in pH had no effect on the removal of the compounds. The efficiency of the removal was greater than 99% for hydrogen sulfide and greater than 70% for VOCs. The microbial communities adapted to the difficult environmental conditions with emergence organisms tolerant to low pH levels {Biotechnol Bioene 1997 53 296-303)
Biofilter performance Biofilters with styrene-degrading fungi growing on perlite have been well defined in terms of the support material, microbial population, and biofilm characteristics. H. H. J. Cox and colleagues reported validation of a model to describe styrene degradation in these filters, which are used to purify waste gases in the plastics industry. Their experimental biofilter, which contained mixed populations of the fungus Exophiala jeanselmei, operated for more than one year with a maximal styrene degradation rate of 62 g/(m 3 h) At high concentration the TT"1 J 1 Y -
imal degradation rate could be increased to 91 e7(m 3 h) Average bio-
0013-936X/97/0931-300A$14.00/0 © 1997 American Chemical Society
