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Anaerobic biodegradation in sewage sludge of polyhydroxybutyrate (PHB) was investigated. Evolved gaseous carbon was measured to assess biodegradability according to ASTM D5210. Mass-loss experiments were performed to determine degradation kinetics. Changes in the polymer properties were investigated. The impact of a natural plasticizer [tributyl citrate (TBC)] on biodegradation was determined. Polylactic acid was also biodegraded for comparison. Melt-pressed plates of PHB (with thicknesses of 0.24, 0.5, 1.2, 3.5, and 5.0 mm) were biodegraded to investigate the relationship between initial mass:initial surface area ratios and decay rates. Scanning electron microscopy micrographs of degraded specimens were recorded for visual illustration of the degradation process. A relationship between initial mass:initial surface area and degradation rates indicates that the thickness and surface area of the material affect its degradation. The degradation rates were impacted by the sewage sludge activity. TBC additive hindered PHB's rate of degradation. Thermal properties, molecular bonding, and molecular weight measured by differential scanning calorimetry, Fourier transform infrared, and size exclusion chromatography, respectively, were only slightly affected by biodegradation, indicating that recycling PHB will not affect its performance. DOI: 10.1061/(ASCE)EE.1943-7870.0000208 CE Database subject headings: Biodegradation; Plastics; Anaerobic treatment; Sewage sludge. Author keywords: Biodegradation; Plastics; Polyhydroxyalkanoate; Bioplastic; Anaerobic treatment; Sewage sludge.

Artificial groundwater recharge for drinking water production involves infiltration of surface water through sandy soil and its capture into a groundwater aquifer. The transformation of aqueous organic matter is one of the central issues in this process. The purpose of this work was to assess the potential of indigenous microorganisms in the source water to contribute in the aqueous organic matter biodegradation. For this purpose, microorganisms were enriched from the source water in a fluidized-bed reactor (FBR) and used for kinetic studies on biodegradation of organic matter at ambient temperature range. Lake water (total organic carbon 5.8 mg [L.sup.-1]) was continuously fed to the FBR containing porous carrier material to support biomass retention. In the inlet and outlet water there were on average 21 [+ or -] 6 and 13 [+ or -] 5 x [10.sup.5] cells [mL.sup.-1], respectively. Biofilm accumulation (as volatile solids) reached 13.1 mg [g.sup.-1] dw cartier. In the continuous-flow mode and the batch tests, the highest oxygen consumption rate appeared in the summer, followed by the fall, spring, and winter. At low temperatures, the biodegradation of aqueous organic matter was relatively rapid initially for labile fractions followed by a slower phase for refractory fractions. The average temperature coefficient ([Q.sub.10]) in the system was 2.3 illustrating a strong temperature dependency of oxygen consumption. The isotopic analysis of dissolved inorganic carbon [[delta].sup.13][C.sub.DIC] analysis revealed 27 and 69% mineralizations of dissolved organic carbon at 23 and 6[degrees]C over 65 and 630 min, respectively. These results can be used to construct additional input parameters in modeling applications of artificial groundwater recharge process. The biological component especially, i.e., the biodegradation, is difficult to predict for on-site applications without experimental proof and thus the interpretation in this study will help formulate design predictions for the process. DOI: 10.1061/(ASCE)EE.1943-7870.0000197 CE Database subject headings: Organic carbon; Groundwater recharge; Fluidized beds; Biomass; Biodegradation; Aquifers; Bacteria; Lakes. Author keywords: Organic carbon; Groundwater recharge; Fluidized beds; Biomass; Biodegradation; Aquifers.

In forest ecosystems, litterfall that collects in trapping devices, to quantify organic matter and nutrient inputs, is exposed to periods of wetting, drying, freezing, and thawing. These fluctuating environmental conditions may influence the microbial community structure inhabiting the leaves and may result in the loss of mobile nutrients, leading to an underestimation of actual organic matter and nutrient inputs. The objectives of this study were to evaluate the influence of (i) different quantities of moisture (LOW = 30 mm, MED = 60 mm, HI = 100 mm) and (ii) freeze-thaw (FT) on leaf (sugar maple (Acer saccharum Marsh.), American basswood (Tilia americana L.), and American beech (Fagus grandifolia Ehrh.)) microbial activity and community structure. There was a significantly greater (p < 0.05) C[O.sub.2] production rate in LOW and FT treatments for sugar maple and beech, and in HI and FT treatments for basswood. A similar trend occurred for leaf nitrogen concentration but not for carbon (C). Utilization of C substrates was up to 10% greater in the FT treatments. Principal components analysis on the activity of C source utilization showed a distinct clustering between leaf species and between treatments following a pattern similar to that of microbial respiration. Results from this study suggested that the collection of litter should take place more frequently during seasons when frost is imminent. Resume: Dans les ecosystemes forestiers, la collecte de chute de litiere dans des dispositifs d'interception, pour quantifier les apports de matiere organique et de nutriments, est exposee a des periodes d'humidification, de sechage, de gel et de de-gel. Ces conditions environnementales fluctuantes peuvent influencer la structure des communautes microbiennes qui habitent les feuilles et entrainer la perte des nutriments mobiles menant a une sous-estimation de la quantite reelle de matiere organique et de nutriments. Les objectifs de cette etude consistaient a evaluer l'influence de (i) differents niveaux d'humidite (LOW = 30 mm, MED = 60 mm et HI = 100 mm) ainsi que du (ii) gel et degel (FT) sur lactivite et la structure des communautes microbiennes presentes sur les feuilles d'erable a sucre (Acer saccharum Marsh.), de tilleul d'Amerique (Tilia americana L.) et de hetre a grandes feuilles (Fagus grandifolia Ehrh.). Le taux de production de CO2 etait significativement plus eleve (p < 0,05) dans les traitements LOW et FT pour l'erable a sucre et le hetre et dans les traitements HI et FT pour le tilleul. La concentration d'azote (N) foliaire suivait la meme tendance mais ce n'etait pas le cas pour le C. L'utilisation des substrats de C etait jusqu'a 10% plus elevee dans les traitements FT. L'analyse en composantes principales de l'utilisation des sources de C a montre qu'il y avait un regroupement distinct sur la base des especes de feuilles et des traitements suivant ainsi un patron similaire a celui de la respiration microbienne. Les resultats de cette etude indiquent que la recolte de litiere devrait etre faite plus frequemment durant les saisons ou des periodes de gel et degel sont imminentes. [Traduit par la Redaction], Introduction The degradation of leaf litter in forest ecosystems is an important process that regulates the availability, mobility, and cycling of organic matter, such as carbon (C) and nutrients. The [...]

The poly(ethylene terephthalate-co-ethyleneoxide-co-DL-lactide) copolymers were successfully prepared by the melt reaction between poly(ethylene terephthalate), poly(ethylene glycol), and DL-oligo(lactic acid) without any catalysts. The transesterification between ethylene terephthalate, ethyleneoxide, and lactide segments during the reaction was confirmed by the [.sup.1]H NMR analysis. The effect of reaction temperatures and the starting feed ratios on the molecular micro structures, molecular weights, solubility, thermal properties, and degradability of the copolyesters was extensively studied. The values of crystallization temperature, melting temperature, crystallization, and melting enthalpy of the copolyesters were found to be influenced by the reaction temperatures, starting feed ratios, etc. The copolyesters showed good tensile properties and were found to degrade in the soil burial experiments during the period of 3 months. The morphology of the copolyester films were also investigated by scanning electron microscopy during soil burial degradation. POLYM. ENG. SCI., 50:76-83, 2010. [C] 2009 Society of Plastics Engineers, INTRODUCTION Aromatic polyesters such as poly(ethylene terephthalate) (PET) are widely used in the field of packaging, textile, and engineering plastics for their good moldability, mechanical properties, and thermal stabilities (1). [...]

Sodium (Na) is uncommon in plants but essential to the metabolism of plant consumers, both decomposers and herbivores. One consequence, previously unexplored, is that as Na supplies decrease (e.g., from coastal to inland forests), ecosystem carbon should accumulate as detritus. Here, we show that adding NaCl solution to the leaf litter of an inland Amazon forest enhanced mass loss by 41%, decreased lignin concentrations by 7%, and enhanced decomposition of pure cellulose by up to 50%, compared with stream water alone. These effects emerged after 13-18 days. Termites, a common decomposer, increased 7-fold on +NaCl plots, suggesting an agent for the litter loss. Ants, a common predator, increased 2-fold, suggesting that NaCl effects cascade upward through the food web. Sodium, not chloride, was likely the driver of these patterns for two reasons: two compounds of Na (NaCl and NaP[O.sub.4]) resulted in equivalent cellulose loss, and ants in choice experiments underused Cl (as KCl, Mg[Cl.sub.2], and Ca[Cl.sub.2]) relative to NaCl and three other Na compounds (NaN[O.sub.3], [Na.sub.3]P[O.sub.4], and [Na.sub.2]S[O.sub.4]). We provide experimental evidence that Na shortage slows the carbon cycle. Because 80% of global landmass lies > 100 km inland, carbon stocks and consumer activity may frequently be regulated via Na limitation. biogeochemistry | biogeography | decomposition | fungi | termites www.pnas.org/cgi/doi/10.1073/pnas.0906448106

Petroleum-hydrocarbon-degrading bacteria were obtained after enrichment on crude oil (as a 'chocolate mousse') in a continuous supply of Indonesian seawater amended with nitrogen, phosphorus and iron nutrients. They were related to Alcanivorax and Marinobacter strains, which are ubiquitous petroleum-hydrocarbon-degrading bacteria in marine environments, and to Qceanobacter kriegii (96.4-96.5% similarities in almost full-length 16S rRNA gene sequences). The Oceanobacter-related bacteria showed high n-alkane-degrading activity, comparable to that of Alcanivorax borkumensis strain SK2. On the other hand, Alcanivorax strains exhibited high activity for branched-alkane degradation and thus could be key bacteria for branched-alkane biodegradation in tropical seas. Oceanobacter-related bacteria became most dominant in microcosms that simulated a crude oil spill event with Indonesian seawater. The dominance was observed in microcosms that were unamended or amended with fertilizer, suggesting that the Oceanobacter-related strains could become dominant in the natural tropical marine environment after an accidental oil spill, and would continue to dominate in the environment after biostimulation. These results suggest that Oceanobacter-related bacteria could be major degraders of petroleum n-alkanes spilt in the tropical sea. DOI 10.1099/mic.0.030411-0

Bacillus subtilis produces [alpha]-L-arabinofuranosidases (EC 3.2.1.55; AFs) capable of releasing arabinosyl oligomers and L-arabinose from plant cell walls. Here, we show by insertion-deletion mutational analysis that genes abfA and xsa(asd), herein renamed abf2, encode AFs responsible for the majority of the intracellular AF activity in B. subtilis. Both enzyme activities were shown to be cytosolic and functional studies indicated that arabino-oligomers are natural substrates for the AFs. The products of the two genes were overproduced in Escherichia coli, purified and characterized. The molecular mass of the purified AbfA and Abf2 was about 58 kDa and 57 kDa, respectively. However, native PAGE gradient gel analysis and cross-linking assays detected higher-order structures (>250 kDa), suggesting a multimeric organization of both enzymes. Kinetic experiments at 37 [degrees]C, with p-nitrophenyl-[alpha]-L-arabinofuranoside as substrate, gave an apparent [K.sub.m] of 0.498 mM and 0.421 mM, and [V.sub.max] of 317 U [mg.sup.-1] and 311 U [mg.sup.-1] for AbfA and Abf2, respectively. The two enzymes displayed maximum activity at 50 [degrees]C and 60 [degrees]C, respectively, and both proteins were most active at pH 8.0. AbfA and Abf2 both belong to family 51 of the glycoside hydrolases but have different substrate specificity. AbfA acts preferentially on (1[right arrow]5) linkages of linear [alpha]-1,5-L-arabinan and [alpha]-1,5-linked arabino-oligomers, and is much less effective on branched sugar beet arabinan and arabinoxylan and arabinogalactan. In contrast, Abf2 is most active on (1[right arrow]2) and (1[right arrow]3) linkages of branched arabinan and arabinoxylan, suggesting a concerted contribution of these enzymes to optimal utilization of arabinosecontaining polysaccharides by B. subtilis.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jenvman.2007.01.038 Byline: A. Salinas-Martinez (a), M. de los Santos-Cordova (a), O. Soto-Cruz (a), E. Delgado (a), H. Perez-Andrade (b), L.A. Hauad-Marroquin (c), H. Medrano-Roldan (a) Keywords: Biodegradation; Heap leaching; Diesel; Microbial consortium Abstract: Heap leaching is an effective and widely used method of recovering metals from low-grade ores. However, the heap leaching technique has not yet been used in other biotechnological processes such as bioremediation. This work describes biostimulation of the native microbial consortium as a novel application of the heap leaching technique to bioremediate mining soils contaminated with hydrocarbons. Microorganisms present in the polluted soil were isolated in a liquid mineral solution using diesel fuel as the sole energy and carbon source. Biodegradation activity was evaluated and two genera, Flavobacterium and Aspergillus, were identified as the primary microorganisms that degraded hydrocarbons in the polluted soil. In order to simulate the heap leaching process on a laboratory scale, using both columns and piles, the contaminated soil was mixed with different sand concentrations and was agglomerated before it was used. Three flow rates, of the mineral solution, were evaluated. Of the rates tested, biodegradation was most efficient at a flow rate of 200mlh.sup.-1. The heap leaching technique demonstrated good efficiency in the column and pile, with a 2% soil-sand mixture lowering the TPH concentration from 61,000 to 1800mgkg.sup.-1 (98.5%) in 15d. Author Affiliation: (a) Instituto Tecnologico de Durango, Unidad de Alimentos y Biotecnologia Industrial, Blvd. Felipe Pescador 1830 Ote, C.P. 34080 Durango, Dgo., Mexico (b) Luismin S.A. de C.V. Gerencia de Control Ambiental, Pino Suarez No. 308 Ote, C.P. 34000 Durango, Dgo., Mexico (c) Universidad Autonoma de Nuevo Leon, Facultad de Ciencias Biologicas, Cd. Universitaria, San Nicolas de los Garza N.L. 66450, Mexico Article History: Received 28 September 2005; Revised 18 December 2006; Accepted 29 January 2007

The purpose of this research is to consider a novel concept for measuring and monitoring (M&M) the presence and levels of contaminants in soil. Current M&M techniques include direct sensing for the target contaminant and the surrogate indicators of respired [O.sub.2] and C[O.sub.2]. The method suggested here is based on nitric oxide (NO). It is an alternative M&M method that could become quicker, easier, more reliable, and less expensive than the other M&M methods being used currently. NO emission from toluene contaminated soil and soil microbial activity were investigated to understand the NO-toluene-soil microbial relationships using fluorescent in situ hybridization molecular technique combined by enzymatic method. The relationships have been analyzed by the comparison of experimental measurements coming from analysis of variance statistical analysis, referring to toluene concentrations. Relationships between NO emissions and the microbial activity were significantly correlated (P CE Database subject headings: Environmental engineering; Monitoring; Biodegradation; Laboratory tests; Soil pollution.

A continuous flow flat sheet hybrid membrane aerated biofilm reactor (MABR) was used to treat a synthetic wastewater containing perchloroethylene (PCE); 1.25-2.5 g chemical oxygen demand (COD)/L of glucose was also added to the synthetic wastewater as a source of COD representative of a real wastewater. The reactor was able to biodegrade 70 mg [L.sup.-1] of PCE in 9 h without the accumulation of any intermediate compounds, resulting in a removal rate of 247 mmol of PCE [h.sup-1] [m.sup.-3] in a reactor with a specific membrane area of 4.048 [m.sup.2] [m.sup.-3]. MABRs have never been used before for PCE degradation, and this rate is one of the highest volumetric PCE degradation rates reported in the literature. COD removal was also good and varied from 85 to 92%. Since very few volatile fatty acids accumulated in the system, most of the residual COD was attributed to soluble microbial products as reported by previous researchers. A mass balance on chloride during this study showed that only 72-81% of it could be accounted for. It is probable that some of the chlorinated ethenes were adsorbed onto the biofilm or that aerobic intermediates of low-chlorinated compounds such as trichloroethanol, dichloroacetyl, and chloroacetaldehyde were produced in the system. Nevertheless the chloride mass balance in this work compares well with the literature. Due to their high PCE and COD removal rates, hybrid MABRs have the potential to be used for a number of refractory organics which require combined anaerobic/aerobic biological treatment for degradation. DOI: 10.1061/(ASCE)0733-9372(2007)133:1(20) CE Database subject headings: Biodegradation; Biofilm; Membranes; Reactors; Hybrid methods.

Ammonium and nitrate were used as nitrogen sources to support microbial biodegradation of crude oil in continuous-flow beach microcosms to determine whether either nutrient was more effective in open systems, such as intertidal shorelines. No differences in the rate or extent of oil biodegradation were observed, regardless of whether these nutrients were provided continuously or intermittently. Nutrients were provided once every two weeks to intermittent-input microcosms and washed out within four to five days. In continuous-input microcosms, ammonium and nitrate were assimilated as quickly as they were provided during the first week, but both accumulated to greater than 10 mg N/L thereafter. The sensitivity of the oil mineralization rate to nutrient input decreased rapidly as the extent of oil degradation increased, and after about two weeks the rate of oil-mineralization appeared to be independent of nutrient input. Therefore, there may be little value in maintaining a long-term supply of nutrients in contact with oil-contaminated sediments. The rates of microbial assimilation of ammonium and nitrate followed similar trends. Both compounds were assimilated more slowly as the extent of oil biodegradation increased, and the nitrate uptake rates approached zero after about two weeks. Ammonium assimilation continued at a low rate throughout the six-week experiment, but this did not appear to affect the rate of oil mineralization. Assimilation of ammonium resulted in a sharp decrease in the pH of the synthetic seawater that was pumped continuously through the microcosms, but nitrate had a much smaller effect on pH. The magnitude of the ammonium-associated pH change was never as large as was observed in previous studies involving oil biodegradation in batch reactors, however, and did not affect the oil-biodegradation rate. CE Database subject headings: Crude oil; Biodegradation; Oil spills; Nutrients; Kinetics; Shore protection.

An isolate from the enrichment culture is obtained and its physiology is characterized during anoxic and aerobic growth on chloromethane (CM), including the yield, stoichiometry of nitrate and oxygen consumption, chloride and nitrogen gas release and kinetics. It was seen that the Pseudomonas aeruginosa strain NB1 also grew on methanol, ethanol and acetate under denitrifying and aerobic conditions.

The soil microcosms studies, using contaminated soil from a timber treatment site clearly showed that the New Zealand T. versicolor isolates mineralized pentachlorophenol (PCP). This demonstrated that viable white-rot fungus is necessary for significant PCP degradation and that T. versicolor isolates showed PCP remediation potential.

The photodegradation of hydrophobic dye in surfactant solution by ultraviolet in the presence of humic materials was investigated through the examination of decay quantum yields and a proposed reaction mechanism. Two different humic materials were used in this study for comparison, a well-defined Aldrich humic substance (Ha) and a soil extracted material (SEM) prepared using a surfactant-aided soil-washing process. Experimental results indicated that the low dose of humic substances mainly acted as a supplementary hydrogen source to improve the photodegradation rate, while at a high dose of humic substances, the characteristics of humic materials being a hydrogen source will be embedded by its amphoteric quenching property, thus retarding the reaction. The possible photodegradation mechanisms of the dye were proposed, and two models based on the dye's decay quantum yields were derived and found to successfully describe the reaction at both low- and high-humic concentrations, which verified and quantified the amphoteric characteristics of humic substances and made the process performance predictable. The results could be useful in quantifying the variation of photolytic rates and facilitating the reactor design for field applications. DOI: 10.1061/(ASCE)0733-9372(2003) 129:6(500) CE Database subject headings: Dyes; Humic substances; Solutions.

An investigation on the effect of sludge solids concentration on bioleaching of Cr(III) and other metals from tannery sludge by indigenous sulphur-oxidizing bacteria was carried out. The sludge solids concentrations ranged from 13 to 60 g/L. The concentration of elemental sulphur was fixed at 30 g/L. The results showed that the lowest pH reached after 25 days of bioleaching at all studied sludge solids concentration was about 1.3. The optimum sludge solids concentration for maximum metal leaching from tannery sludge was 40 g/L and about 87% of Cr(III), 73% of Al, 72% of Fe, 62% of Mg, and 73% of Zn could be leached in this case. During bioleaching, the concentrations of total and volatile suspended solids of the tannery sludge significantly decreased. The sulphur-oxidizing bacteria could tolerate a Cr(III) concentration as high as 5,930 mg/L at pH 1.3. The leaching efficiencies of Cr(III), Al, and Fe for both chemical leaching and bioleaching of tannery sludge were similar at pH 1.3. The leaching efficiency of Ca, Mg, and Zn in both leaching processes were identical for pH values in the range of 1.3 to 3.0. DOI: 10.1061/(ASCE)0733-9372(2003) 129:6(513) CE Database subject headings: Sludge treatment; Chromium; Leaching; Metals; Bacteria.

This paper examines the influence of bed segregation on the performance of an anaerobic fluidized bed bioreactor (AFBR) using both an integrated mathematical model previously described in Part I of this study, and experimental data obtained from a laboratory-scale AFBR continuous flow system and batch serum vial tests. Local hydrodynamics within the bed are shown to determine mixing intensities and patterns of bioparticles thereby controlling biofilm thickness and composition along the bed height. Results of the model simulations and the experimental data indicate that shallow biofilms that allow full substrate penetration are dominantly populated with faster growing micro-organisms. The internal mass transfer resistance in thicker biofilm significantly influences population distribution resulting in the increase of population of slower growing micro-organisms in a deeper layer of the biofilm. The serum bottle tests also confirm that microbial distribution inside a multispecies biofilm is determined by the hydrodynamic condition of the reactor. This study illustrates the importance of hydrodynamic regimes in the AFBR, and demonstrates the impact of bed segregation on bioparticle properties and total system performance. CE Database keywords: Mathematical models; Cisterns; Fluidized beds; Waste treatment; Simulation.

An integrated mathematical model for propylene glycol (PG) degradation in an anaerobic fluidized bed bioreactor is described. Special attention is put on biomass distribution, bed expansion, and bed segregation, associated with the biofilm accumulation process. In order to interpret the segregation of the bed during the initial development of the biofilm, the model postulates various mixing intensities along the bed height and thereby different exchange rates of microbial cells between the biofilm and the bulk liquid. The model incorporates stoichiometry of PG methanization, hydrodynamics, and reaction kinetics for elucidating microscopic interaction among microbial trophic groups inside the biofilm as well as the macroscopic behavior of the reactor such as bed expansion. A biofilm diffusion mechanism is also taken into account focusing on the spatial distribution of multiple species of micro-organisms. Employing moving boundaries makes the model flexible in computation, which permits simplifying the implementation of the biofilm accumulation and the bed expansion phenomena. CE Database keywords: Mathematical models; Cisterns; Fluidized beds; Waste treatment.

A combination of sonolysis and ozonolysis has been found to be effective in degrading aromatic compounds in water at both 20 khz and 500 khz. Sonolysis and Ozonolysis alone have been proven to be selective catalysts in degrading the nitrobenzene, 4-nitrophenol and 4-chlorophenol in water. A hybrid process combining the two was able to enhance the total organic carbon reduction rates for all three compounds with observable intermediate product formation.

Iron(III) photoinduced degradation of alkylphenol ethoxylates (APE) in water is found to be feasible with enormous possibilities in environmental management. Iron(III) degradation of a major fraction of ethoxymers has been found to occur efficiently under sunlight and at 365nm. The system basically involves hydrogen abstraction of one carbon of the ethoxy chain and the products include aldehyde ethoxylates, formate ethoxylates and octylphenol.

A Bacillus sphaericus monooxygenase capable of catalyzing the first two steps in the degradation of p-nitrophenol (PNP) via 4-nitrocatechol and 1,2,4-trihydroxybenzene (THB) was identified and characterized. Nitrite was produced stoichiometrically by PNP-grown cells. Results of the THB stimulation of oxygen consumption reveal that THB acts as a substrate for a ring cleavage dioxygenase. It was also observed that a single monooxygenase system was capable of catalyzing the initial hydroxylation of PNP and the oxidative release of the nitro group from the 4-nitrocatechol.

Pseudomonas strains with the ability to degrade isopropylbenzene (IPB) and tricholoroethane (TCE) are developed using an ipb DNA module. Results from the localization of transcriptional start points of the ipbA genes indicate that ipb gene expressions are regulated in response to IPB at the transcriptional level. The mutant Pseudomonas sp. strain JR1 exhibited the ability to efficiently degrade TCE after the induction of TCE-oxidizing oxygenase.

Biofiltration of a gaseous stream contaminated with benzene, toluene, ethylbenzene, and the three xylene (BTEX) compounds was evaluated in this study. Experimental investigations were conducted on a pilot-scale biofilter containing randomly packed 6-mm R-635 Celite pellets as biological attachment media. The main focus of the study was to expand biofiltration technology to treat high volatile organic compounds (VOC) concentrations while maintaining consistently high removal efficiencies. Operational parameters investigated were BTEX loading, empty bed residence time (EBRT), backwashing frequency and duration, recovery of biofilter removal efficiency after backwashing, development of removal rate constants, and nutrient-phosphorous (nutrient-P) limitation as a biomass control. Periodic backwashing of the biofilter with medium fluidization was necessary for removing excess biomass and attaining stable long-term high removal efficiencies. Removal efficiencies above 99% were achieved for all the BTEX components for loadings up to 1.8 kg chemical oxygen demand (COD)/[m.sup.3]/d. Stable overall removal efficiencies of 88% were achieved for a BTEX loading of 6.2 kg COD/[m.sup.3]/d and an EBRT of 0.67 min. Evaluations of pseudo-steady-state performance data, one day following backwashing, yielded first-order removal rate constants for all the BTEX components. Removal efficiencies above 99% at BTEX loading of 2.1 kg COD/[m.sup.3]/d were attained for a period of 14 d without biofilter back-washing in the absence of nutrient-P.

It is believed that the use of stable oxygen and carbon isotope analyses will help in the accurate identification of the occurrence, pathways, and rates of intrinsic or enhanced in situ biodegradation. A recent laboratory test utilized diesel fuel and a mixed microbial culture to demonstrate the monitoring capability of a combined stable carbon and oxygen isotope analyses of carbon dioxide and molecular oxygen, respectively.

A study aimed at investigating the rates of selenium volatilization, particularly in wetland systems, is presented. Water samples from Benton Lake, MT are examined to determine their natural selenium volatilization. It was found out that selenium volatilization happened in water, sediment, and wetland plants. It was noted that algae and high-selenium sediment register a higher rate of selenium volatilization than watermilfoil and low-selenium sediment. It is believed that efforts in removing selenium in wetland systems can benefit from natural selenium volatilization process.

Halogenated ethylenes undergo reductive beta-elimination to alkynes under environmental conditions. To test this hypothesis, zero-valent metals such as iron and zinc were used to degrade contaminants such as dichloroethylenes and chlorinated ethylenes, respectively, under controlled conditions. The results confirmed previous findings that reductive beta-elimination pathways are involved in the reaction of chloroethylenes with zero-valent metals.

The electrohydraulic discharge (EHD) process offers an alternative technology for the treatment of hazardous chemical liquid wastes. It occurs inside an EHD reactor which has a pulsed-power electrical discharge circuit for storing electrical energy. Energy is injected into an aqueous solution through a plasma channel which is created by the reactor's electrodes. The application of the EHD process to degrade 4-chlorophenol, 3,4-dichloroaniline, and 2,4,6-trinitrotoluene is presented.

Polychlorinated dibenzo-p-dioxins (PCDD), dibenzofurans (PCDF) and biphenyls (PCB) are environmental pollutants that have been the subject of several biological degradation studies. One approach to understanding the reactivity and toxicity of PCDD, PCDF and PCB is to investigate the thermal behavior of their parent compounds through the amount of activated carbon in air, with total organic carbon as a parameter. Experiments using this approach are presented.

Polychlorinated biphenyls (PCBs) are ubiquitous compounds that have been the target of a variety of degradation methods. A method that is showing potential is PCB radiolytic degradation in a nonpolar solvent. Studies investigating this technology in air-equilibrated isooctane and transformer oil reveal a significant degradation of PCBs in both solvents. Scavenging studies show that the electron is the primary reactive species responsible for PCB degradation thru this method.

Vermiculture has become successful commercially that most breeders have expanded their operations to include vermicomposting. While vermiculture focuses on the large-scale breeding and growing of worms and the production of castings, vermicomposting involves the recycling of organic materials. Some of the more successful vermicomposting operations include Chattanooga, TN-based Goodwill Industries, Banks of Eden Farm in Eden, MD, and Alpine, CA-based Environmental Recycling Systems. For vermicomposting, the most commonly used works are red wigglers.

Sonochemical reactors were used to examine the degradation of p-nitrophenol in a near-field acoustical processor (NAP). A mathematical model was used to compute for the pseudo-first-order rate constant from kinetic data. The results suggested that NAP is a more effective approach in industrial processes than conventional probe-type reactors.

Higher amounts of trichloroethylene (TCE) were removed from the lumen of methanotrophic bacteria, Methylosinus trichosporium OB3b, inside a hollow fiber membrane bioreactor at hydraulic residence times of 5-9 min in the lumen than at hydraulic residence times of 3-15 min in the lumen and shell. Rapid biodegradation was observed when TCE was transferred to the shell, with 75% of the transferred TCE achieving complete biodegradation. These results suggest that a hollow fiber membrane reactor system coupled with a mutant strain of the methanotrophic bacteria could be an effective method for biodegradation.

A leachate-recycle system (LRS) consisting of four infiltration ponds was operated and monitored over a 28-month period at an active lined landfill in Florida. Ponds were constructed by excavating into the landfilled waste and by compacting lifts of solid waste to form the pond walls. A total of 36,470 [m.sup.3] of leachate were recirculated, representing 63% of the total volume of leachate generated. The entire leachate stream was not recycled because of the large volume of leachate and the low leachate infiltration rates into the landfill. Water budgets conducted on individual ponds over the first 16 months of operation revealed that the infiltration rates ranged from 6 x [10.sup.-6] to 9 x [10.sup.-6] cm/sec. The vertical saturated hydraulic conductivity of the compacted waste was estimated in the range of 3 x [10.sup.-6]-4 x [10.sup.-6]cm/sec, lower than values reported in the literature.

Methanotrophic degradation of vinyl chloride (VC) is investigated using a laboratory-scale methanotrophic attached-film expanded-bed (MAFEB) bioreactor. This study provides a basis for applying a microbial cometabolizing reaction to practical treatment of toxic chlorinated compounds. The MAFEB reactor was operated at 20[degrees]C with influent VC concentrations ranging from 1,800 to 9,600 [mu]g/L and bed hydraulic retention times ranging from 3.7 to 7.6 h. VC effluent concentrations during steady continuous operation ranged from 3 to 140 [mu]g/l, with most values less than 26 [mu]g/l, resulting in removal efficiencies of 96.3% to 99.8%. The maximum continuous-flow VC degradation rate observed at 20[degrees]C was 2.5 mg VC per gram volatile solids (VS) per day [2.5 mg VC/(g VS d)] or 30 mg VC per liter expanded bed per day 30 mg VC/[L.sub.eb] d), under substrate-limited conditions. During semibatch runs at 35[degrees]C, vinyl chloride degradation rates up to 60 mg VC/ (g VS d) or 1 g/([L.sub.eb] d) were observed. Degradation rates increased with temperature between 20[degrees]C and 35[degrees]C, approximately doubling every 10[degrees]C. Dissolved methane concentrations above 0.5 mg/L inhibited VC degradation, with no VC degradation observed with 8 mg/L dissolved methane. The methane consumed during VC degradation was about 40 g [CH.sub.4]/g VC. Toxic effects were observed after prolonged exposure of the methanotrophic culture to high concentrations of VC.

The development of a degradation pathway from the microbial growthon 2-chloroallyalcohol is discussed. Cells were harvested from anaerobically grown bacterial strains. A biological oxygen monitor determined alcohol and aldehyde dehydrogenase activities. Capillary gas chromatography quantitatively determined chlorinated allyalcohol and were analyzed by high-pressure liquid chromatography. The suitability of 2-chloroallyalcohol as a substrate for bacterial growth was demonstrated.

The practicality of developing highly-dechlorinating anaerobic methanogenic granules and their performance in treating wastewaters with high pentachlorophenol (PCP) concntrations were evaluated. A mixture of acetate, propionate, butyrate and methanol were used as the carbon source for the development of the granules in a laboratory-scale anaerobic upflow sludge blanket reactor. Higher PCP sensitivity was demonstrated by syntrophic propionate degraders and acetate-utilizing methanogens compared to syntrophc butyrate degraders.