Isolation of novel bacteria within the Chloroflexi capable of reductive dechlorination of 1,2,3-trichloropropane.

Two strictly anaerobic bacterial strains were isolated from contaminated groundwater at a Superfund site located near Baton Rouge, LA, USA. These strains represent the first isolates reported to reductively dehalogenate 1,2,3-trichloropropane. Allyl chloride (3-chloro-1-propene), which is chemically unstable, was produced from 1,2,3-trichloropropane, and it was hydrolysed abiotically to allyl alcohol and also reacted with the sulfide- and cysteine-reducing agents in the medium to form various allyl sulfides. Both isolates also dehalogenated a variety of other vicinally chlorinated alkanes (1,2-dichloropropane, 1,2-dichloroethane, 1,1,2-trichloroethane, 1,1,2,2- tetrachloroethane) via dichloroelimination reactions. A quantitative real-time PCR (qPCR) approach targeting 16S rRNA genes indicated that both strains couple reductive dechlorination to cell growth. Growth was not observed in the absence of hydrogen (H2) as an electron donor and a polychlorinated alkane as an electron acceptor. Alkanes containing only a single chlorine substituent (1-chloropropane, 2-chloropropane), chlorinated alkenes (tetrachlorothene, trichlorothene, cisdichloroethene, trans-dichloroethene, vinyl chloride) and chlorinated benzenes (1-chlorobenzene and 1,2- dichlorobenzene) were not dechlorinated. Phylogenetic analysis based on 16S rRNA gene sequence data showed these isolates to represent a new lineage within the Chloroflexi. Their closest previously cultured relatives are 'Dehalococcoides' strains, with 16S rRNA gene sequence similarities of only 90%.

Effect of sorption and desorption-resistance on biodegradation of chlorobenzene in two wetland soils.

Bioavailability of chlorobenzenes (CBs) in soils to microbial populations has implications for remediation of waste sites with long histories of contamination. Bioavailability of CB was assessed using mineralization assays for two types of wetland soils with contrasting properties. The rate and extent of CB mineralization were greater than predicted by mathematical models which assume instantaneous desorption followed by biodegradation. The freshly added CB was degraded with initial mineralization rates (IMRs) of 0.14microgL(-1)h(-1) and 1.92microgL(-1)h(-1) for marsh soil and wetland soil respectively. These values indicate that CB-degrading bacteria had an access to the sorbed CB. Mineralization assays were also performed for wetland soils after the CB was aged for 1, 7 and 31 days. The results revealed that even a desorption-resistant part of the sorbed CB was degraded although the degradation occurred at lower rates and to a lesser extent.

Chemical and microbiological parameters in New Orleans floodwater following Hurricane Katrina.

Hurricane Katrina, rated as a Category 4 hurricane on the Saffir-Simpson scale, made landfall on the U.S. Gulf Coast near New Orleans, Louisiana on Monday, August 29, 2005. The storm brought heavy winds and rain to the city, and several levees intended to protect New Orleans from the water of Lake Pontchartrain were breached. Consequently, up to 80% of the city was flooded with water reaching depths in excess of three meters in some locations. Research described in this paper was conducted to provide an initial assessment of contaminants present in floodwaters shortly after the storm and to characterize water pumped out of the city into Lake Pontchartrain once dewatering operations began several days after the storm. Data are presented which demonstrate that during the weeks following the storm, floodwater was brackish and well-buffered with very low concentrations of volatile and semivolatile organic pollutants. Dissolved oxygen was depleted in surface floodwater, averaging 1.6 mg/L in the Lakeview district and 4.8 mg/L in the Mid-City district. Dissolved oxygen was absent (< 0.02 mg/L) at the bottom of the floodwater column in the Mid-City district 9 days afterthe storm. Chemical oxygen demand (Mid-City average = 79.9 mg/L) and fecal coliform bacteria (Mid-City average = 1.4 x 10(5) MPN/100 mL) were elevated in surface floodwater but typical of stormwater runoff in the region. Lead, arsenic, and in some cases, chromium, exceeded drinking water standards but with the exception of some elevated Pb concentrations generally were typical of stormwater. Data suggest that what distinguishes Hurricane Katrina floodwater is the large volume and the human exposure to these pollutants that accompanied the flood, rather than very elevated concentrations of toxic pollutants.

Assessment of microbial populations in methyl ethyl ketone degrading biofilters by denaturing gradient gel electrophoresis.

Denaturing gradient gel electrophoresis (DGGE) analysis of polymerase chain reaction-amplified genes coding for 16S rRNA was used to assess differences in bacterial community structure as a function of spatial location along the height of two biofilters used to treat a model waste gas stream containing methyl ethyl ketone (MEK). One of the laboratory-scale biofilters was operated as a conventional continuous-flow biofilter (CFB) and the other was operated as a sequencing batch biofilter (SBB). Both biofilters, inoculated with an identical starting culture and operated over a period lasting more than 300 days, received the same influent MEK concentration and same mass of MEK on a daily basis. The systems differed, however, in terms of the fraction of time during which contaminated air was supplied and the overall operating strategy employed. DGGE analysis indicated that microbial community structures differed as a function of height in each of the biofilters. The DGGE banding patterns also differed between the two biofilters, suggesting that operating strategies imposed on the biofilters imparted a sufficiently large selective pressure to influence microbial community structures. This may explain, in part, the superior performance of the SBB over the CFB during model transient loading conditions, and it may open new possibilities for purposely manipulating the microbial populations in biofilters treating gas-phase contaminants in a manner that leads to more favorable treatment performance.

Sequencing batch biofilter operation for treatment of methyl ethyl ketone (MEK) contaminated air.

Biofiltration is increasingly used as a method for decontaminating gas streams containing low concentrations of biodegradable volatile organic compounds. In typical biofilter installation control is quite passive and is often restricted to adjustment of the medium's moisture content or nutrient supply. Although inexpensive, such operation limits implementation of engineering decisions that could improve performance during normal operation orallow effective handling of the short-term variations in the waste stream typical of industrial operations. This paper describes how sequencing batch operation can be applied to biofilters designed and operated as controlled, unsteady-state, periodic processes for the destruction of gas-phase contaminants. In the studies described herein, the impact of sequencing batch operation was assessed in a methylethyl ketone degrading biofilter over a 130-day period. The biofilter was packed with a polyurethane foam medium that contained activated carbon. Methyl ethyl ketone and carbon dioxide concentrations were monitored during both normal steady loading conditions and short-term, unsteady-state transient loading conditions (i.e., shock loading). A gas stream containing 106 ppm, methyl ethyl ketone was used for normal loading studies, and several model shock loads consisting of 530 ppm, methyl ethyl ketone for a duration of one hour were used to assess system response to transient loads. Data are presented which clearly demonstrate that sequencing batch operation can be successfully applied to biofilters treating methyl ethyl ketone contaminated air streams. Such operation can increase an operator's ability to minimize contaminant emission during transient periods of elevated contaminant loading.

Biodegradation of volatile organic compounds by five fungal species.

Five fungal species, Cladosporium resinae (ATCC 34066), Cladosporium sphaerospermum (ATCC 200384), Exophiala lecanii-corni (CBS 102400), Mucor rouxii (ATCC 44260), and Phanerochaete chrysosporium (ATCC 24725), were tested for their ability to degrade nine compounds commonly found in industrial off-gas emissions. Fungal cultures inoculated on ceramic support media were provided with volatile organic compounds (VOCs) via the vapor phase as their sole carbon and energy sources. Compounds tested included aromatic hydrocarbons (benzene, ethylbenzene, toluene, and styrene), ketones (methyl ethyl ketone, methyl isobutyl ketone, and methyl propyl ketone), and organic acids ( n-butyl acetate, ethyl 3-ethoxypropionate). Experiments were conducted using three pH values ranging from 3.5 to 6.5. Fungal ability to degrade each VOC was determined by observing the presence or absence of visible growth on the ceramic support medium during a 30-day test period. Results indicate that E. lecanii-corni and C. sphaerospermum can readily utilize each of the nine VOCs as a sole carbon and energy source. P. chrysosporium was able to degrade all VOCs tested except for styrene under the conditions imposed. C. resinae was able to degrade both organic acids, all of the ketones, and some of the aromatic compounds (ethylbenzene and toluene); however, it was not able to grow utilizing benzene or styrene under the conditions tested. With the VOCs tested, M. rouxiiproduced visible growth only when supplied with n-butyl acetate or ethyl 3-ethoxypropionate. Maximum growth for most fungi was observed at a pH of approximately 5.0. The experimental protocol utilized in these studies is a useful tool for assessing the ability of different fungal species to degrade gas-phase VOCs under conditions expected in a biofilter application.

Polyurethane foam based biofilter media for toluene removal.

Polyurethane foam medium was manufactured and analyzed to determine its suitability as a solid support medium for use in gas-phase biofilters. Physical and chemical studies were conducted to determine the medium's characteristics. The medium's ability to support an active biofilm capable of degrading volatile organic compounds was assessed using a laboratory scale biofilter fed a model waste stream containing toluene for more than 250 days with empty bed residence times (EBRTs) ranging from two to four minutes. Results are presented that show how a polyurethane foam medium with high porosity, suitable pore size, low density, and an ability to sorb water was able to remove over 99% of the influent toluene when fed at a concentration of 200 ppm. An operating strategy is described which effectively prevented two problems common to conventionally operated biofilter systems: nutrient limitations and biosolid accumulation.

Period biofilter operation for enhanced performance during unsteady-state loading conditions.

In conventional biofilter operation, contaminated air is passed continuously through packed beds containing microbial consortia capable of contaminant biotransformation. This paper describes how biofilters can be designed and operated as controlled unsteady-state, periodic processes for the destruction of gas-phase contaminants. Such operation, previously limited to applications in wastewater treatment and soil remediation, increases an operator's ability to control the physiological state, "robustness," and spatial distribution of the microbial communities established within the biofilter and, thus, minimizes uncertainties that often accompany design and operation of biological systems. Results are presented from toluene degrading biofilters that used polyurethane foam packing medium. These studies demonstrate how controlled periodic operations can enhance contaminant removal during transient periods of elevated contaminant load.

Intracellular dynamics of ribonucleic acid (RNA) and protein in microorganisms from periodically operated biofilters.

Conventional biofilters are designed and operated as continuous flow processes where the reactors receive a constant stream of contaminated air. Recent research has shown that periodically operated biofilters can remove a greater mass of contaminants during shock loads than equally sized continuously loaded biofilters. Preliminary experiments were conducted to investigate effects of periodic operation on physiological state of biofilter microorganisms. Relative concentrations of two macromolecular components of microbial cells, RNA and protein, were quantified in biosolids samples removed from biofilters operated under different periodic and continuous loading strategies. Preliminary studies presented herein suggest that the physiological state of the microbial population present in the periodically operated biofilter differs from that of those present in the biofilter operated continuously supplied air.

Effect of nitrogen limitation on performance of toluene degrading biofilters.

The literature reports conflicting observations regarding the need for nutrient addition to biofilters treating contaminated gases. Such conflicts are often based on quasi-steady-state performance data collected on biofilters operated under continuous loading conditions. In the studies described herein, the impact of nitrogen limitations on two toluene-fed biofilters was assessed over a 97-day period. The biofilters were packed with polyurethane foam medium and contained different initial levels of nitrate-nitrogen. Toluene and CO2 concentration profiles were monitored during both normal steady loading conditions and short-term, unsteady-state transient loading conditions (e.g., shock loads). Packing medium samples were periodically removed and analyzed to quantify changes in nitrate-nitrogen content over time. Data are presented which show that over long-time periods (several months), nutrient-induced kinetic limitations diminished biofilter performance during transient, unsteady-state conditions even when performance during normal steady loading was not adversely affected. Elemental analysis of biomass removed from the biofilters support nitrate-nitrogen and CO2 concentration profile data and clearly illustrate how kinetically limited biofilters fail during shock loads even when there is an overall stoichiometric excess of nutrients.