A microcosm test for potential mineralization of chlorinated compounds under coupled aerobic/anaerobic conditions.

In this study, the feasibility of using a mineralization test under coupled aerobic/anaerobic conditions was demonstrated. The coupling of anaerobic methanogenic and aerobic methanotrophic conditions in a microcosm required the presence of both a carbon source for anaerobic metabolism and oxygen for aerobic metabolism. These requirements were fulfilled by using a slow hydrolyzing organic matter along with intermittent addition of oxygen to the bottle headspace. Perchloroethylene (PCE) mineralization tests confirmed the effectiveness of the proposed methodology as well as PCE mineralization under coupled conditions.

An epizootiological survey of necropsy cases (1993-1997) at University of the Philippines.

An epizootiological survey of necropsied cases (1993-1997) at University of the Philippines was performed. A total of 368 cases included 238 avian and 111 porcine cases. Amongst avian cases, the major cause of death was infectious diseases in 212 (89%) cases including 97 (41%) bacterial, 36 (15%) viral, and 21(9%) parasitic diseases. The majority of the avian bacterial diseases presented as septicemia (73 cases) and the viral diseases as Newcastle disease (17 cases). In porcine cases, the major cause of death was also infectious diseases, in 100 (90%) cases including 52 bacterial and 29 viral diseases. Porcine bacterial diseases were classified into 36 septicemia, 4 hemophillosis and 4 colibacillosis. Amongst the porcine viral diseases, most cases were diagnosed as Hog cholera (22 cases).

Strategies for augmenting the pentachlorophenol degradation potential of UASB anaerobic granules.

Anaerobic degradation of pentachlorophenol (PCP) is an example of a process that may benefit from enrichment or bioaugmentation. In one approach, enrichment acceleration was attempted by applying an on-line control-based selective stress strategy to a native anaerobic upflow sludge bed (UASB) system; this strategy linked PCP loading rate to methane production. As a result, the reactor biomass potential for PCP complete dechlorination reached a rate of 4 mg g(-1) volatile suspended solid (VSS) day(-1) within a period of 120 days. In another approach, a pure culture, Desulfitobacterium frappieri PCP-1, a strictly anaerobic Gram-positive bacterium, was used to augment the granular biomass of the UASB reactor. This also resulted in a specific degradation rate of 4 mg PCPg(-1) VSS day(-1); however, this potential was attained within 56 days. Fluorescent in situ hybridization (FISH) showed that the PCP-1 strain was able to rapidly attach to the granule and densely colonize the outer biofilm layer.

A two-population bio-electrochemical model of a microbial fuel cell.

This work presents a two-population model describing the competition of anodophilic and methanogenic microbial populations for a common substrate in a microbial fuel cell (MFC). Fast numerical solution of the model is provided by using ordinary differential equations to describe biomass growth and retention in the anodic compartment. The model parameters are estimated and validated using experimental results obtained in four continuous-flow air-cathode MFCs operated at various external resistances and organic loads. Model analysis demonstrates the influence of operating conditions on MFC performance and suggests ways to maximize MFC power output. The model is suitable both for process optimization and on-line control applications.

Biodegradation of gasoline and BTEX in a microaerophilic biobarrier.

Continuous bioremediation of gasoline-contaminated water in a packed-bed biobarrier system under oxygen-limited conditions is discussed. This study was part of an extensive effort to develop an alternative technology for the in situ bioremediation of hydrocarbons where there is a limited supply of oxygen. Protruded stainless steel pieces and granulated peat moss were used as packing material to support microbial growth in two biobarriers. The inoculum was an enrichment culture of an indigenous microbial population from a soil sample. The biobarriers' inlet gasoline concentrations and the linear liquid velocities were similar to those commonly found at in situ conditions. Gasoline removal efficiencies ranged from 94% to 99.9% in the stainless steel-packed biobarrier, and from 86.6% to 99.6% in the peat moss-packed biobarrier. Effluent gasoline concentrations below 0.03 mg/l were obtained at gasoline loading rates less than 27.5 mg/l.d in the stainless steel-packed biobarrier. The remaining fraction of gasoline in the effluent consisted mainly of three aliphatic compounds and not the aromatic compounds. Both biobarrier packings supported near complete removal of the most soluble aromatic hydrocarbons of gasoline (BTEX) under all the conditions examined. The consumption of sulfate and the presence of sulfate-reducing microorganisms suggested the presence of anaerobic metabolism during the degradation of gasoline. Up to 92% gasoline was removed during the first 3 cm of the biobarriers' length.

Trichloroethylene degradation in a coupled anaerobic/aerobic reactor oxygenated using hydrogen peroxide.

In this work, trichloroethylene (TCE) degradation under combined anaerobic-aerobic conditions was studied in an ethanol-fed biofilm reactor oxygenated using hydrogen peroxide. The reactor was inoculated with a biomass originating from an anaerobic digestor. Granulated peat was added to the reactor as a substratum for biofilm development. Extensive characterization of reactor populations using activity tests and PCR analysis revealed the development of a mutualistic consortium, particularly methanotrophic and methanogenic microorganisms. This consortium was shown to degrade TCE by a combination of reductive and oxidative pathways. A near complete degradation of TCE at a load of 18 mg L(R)(-1) day(-1) was evidenced by a stoichiometric release of inorganic chloride.

Enhanced selection of an anaerobic pentachlorophenol-degrading consortium.

A rapid enrichment approach based on a pentachlorophenol (PCP) feeding strategy which linked the PCP loading rate to methane production was applied to an upflow anaerobic sludge bed reactor inoculated with anaerobic sludge. Due to this strategy, over a 140-day experimental period the PCP volumetric load increased from 2 to 65 mg L(R)(-1) day(-1) with a near zero effluent concentration of PCP. Dechlorination dynamics featured sequential appearance of 3,4,5-chlorophenol, 3,5-chloro- phenol, and 3-chlorophenol in the reactor effluent. Profiling of the reactor population by denaturing gradient gel electrophoresis (DGGE) revealed a correlation between the appearance of dechlorination intermediates and bands on the DGGE profile. Nucleotide sequencing of newly detected 16S rDNA fragments suggested the proliferation of Clostridium and Syntrophobacter/Syntrophomonas spp. in the reactor during PCP degradation. Published by John Wiley & Sons, Inc.