Abstract Research was conducted to determine the effect of chemical oxidation on subsurface microbiology and cometabolic biodegradation capacity in a trichloroethene (TCE)/perchloroethene (PCE)-contaminated aquifer previously treated with Fenton's reagent. Groundwater pH declined from 5 to 2.4 immediately after the treatment, and subsequently rose to a range of 3.4 to 4.0 after 17 months. Limited microbial growth and TCE degradation were detected in the treated zone (pH 3.37 and TCE 5 to 21 mg/L) with carbon addition (i.e., methane and phenol). Methane addition resulted in the enrichment of yeast and fungi in microcosms at low pH. In contrast, methane addition to groundwater from the control well (pH 4.9 and TCE ca. 0.7 mg/L) stimulated methanotrophic growth, indicated by methane consumption, fluorescent antibody analysis, phospholipid-based markers, and rDNA probes. TCE degradation was measured in the control microcosms, but only when phenol was added. Although higher TCE concentrations in the treated zone might have inhibited TCE cometabolism, these results also indicate that low groundwater pH resulting from the chemical oxidation process (pH 3.37 versus 4.9) inhibited TCE degradation. Methanotrophic growth and TCE biodegradation may be possible as pH increases both in the treated zone and at the leading edge of plume, as long as the local soil is able to buffer the groundwater pH. Moreover, the Fenton's reagent process could be designed to operate at a higher pH (e.g., ≥ 4.5) and/or lower hydrogen peroxide concentration to minimize detrimental effects, providing an optimal environment to couple advanced oxidation processes with bioremediation technologies.
Coliphages can indicate contamination of recreational waters and previous studies show that sunlight is important in altering densities of coliphages, other indicator microorganisms, and pathogens in aquatic environments. Here, we report on laboratory studies of light-induced inactivation of two coliphage groups—male-specific (F+) and somatic coliphage—under various conditions in phosphate-buffered water (PBW). Strains isolated from wastewater treatment facilities and laboratory strains (MS2 and phiX174 coliphages) were evaluated. Inactivation rates were determined in a series of irradiations using simulated solar radiation passed through light filters that blocked different parts of the ultraviolet spectral region. Inactivation rates and spectral irradiance from these experiments were then analyzed to develop biological weighting functions (BWFs) for the light-induced inactivation. BWFs were used to model the inactivation of coliphages over a range of conditions in aquatic environments that included two beach sites in Lake Michigan and one in Lake Erie. For example, modeled effects of sunlight attenuation, using UV absorption data from the three Great Lakes beach sites, inferred that direct photoinactivation rate constants, averaged over a one-meter water column in swimmable areas, were reduced 2- to 5-fold, compared to near-surface rate constants.
Many watershed models simulate overland and instream microbial fate and transport, but few actually provide loading rates on land surfaces and point sources to the water body network. This paper describes the underlying general equations for microbial loading rates associated with 1) landapplied manure on undeveloped areas from domestic animals; 2) direct shedding on undeveloped lands by domestic animals and wildlife; 3) urban or engineered areas; and 4) point sources that directly discharge to streams from septic systems and shedding by domestic animals. A microbial source module, which houses these formulations, is linked within a workflow containing eight models and a set of databases that form a loosely configured modeling infrastructure which supports watershed-scale microbial source-to-receptor modeling by focusing on animal-impacted catchments. A hypothetical example application – accessing, retrieving, and using real-world data – demonstrates the ability of the infrastructure to automate many of the manual steps associated with a standard watershed assessment, culminating with calibrated flow and microbial densities at the pour point of a watershed.
Sixteen sites in the watershed of the South Fork of the Broad River (SFBR) in Northeastern Georgia, USA, were sampled in two seasons to detect Campylobacter. Sites were classified as mostly influenced by forest, pasture, wastewater pollution control plants (WPC) or mixed use. Sampling was repeated in the late spring and late fall for 2 years for a total of 126 samples. Free-catch water and sediment grab samples were taken at each site; Moore's swabs were placed for up to 3 days at most sites. A total of 56 isolates of thermophilic Campylobacter were recovered. Thirteen samplings were positive by two or three methods, and 26 samplings were positive by only one method; once by Moore's swab only and 25 times by free-catch water only. Campylobacter was detected at 58% of cattle pasture sites, 30% of forested sites and 81% of WPC sites. Twenty-one of the isolates carried antimicrobial resistance genes, mostly blaOXA-61. Free-catch water samples were more efficient than Moore's swabs or sediment samples for recovery of Campylobacter, which was more likely to be detected in streams near cattle pastures and human communities than in forested land. Significance and Impact of the Study The role of environmental water in transmitting Campylobacter was investigated, and methods for recovery of the organism were compared. The sequence types of recovered Campylobacter correlated with adjacent land use without regard to the method used to isolate the organisms. Sequence types and antimicrobial resistance genes associated with cattle were most prevalent near pastures. Even though types were recurrent at a given site, types appeared to be lost or replaced as the water flowed downstream.
The objective of this work was to evaluate the effects of fire regimes and vegetation cover on the structure and dynamics of soil microbial communities, through phospholipid fatty acid (PLFA) analysis. Comparisons were made between native areas with different woody covers ("cerrado stricto sensu" and "campo sujo"), under different fire regimes, and a 20-year-old active palisadegrass pasture in the Central Plateau of Brazil. Microbial biomass was higher in the native plots than in the pasture, and the highest monthly values were observed during the rainy season in the native plots. No significant differences were observed between fire regimes or between communities from the two native vegetation types. However, the principal component (PC) analysis separated the microbial communities by vegetation cover (native x pasture) and season (wet x dry), accounting for 45.8% (PC1 and PC3) and 25.6% (PC2 and PC3), respectively, of the total PLFA variability. Changes in land cover and seasonal rainfall in Cerrado ecosystems have significant effects on the total density of soil microorganisms and on the abundance of microbial groups, especially Gram-negative and Gram-positive bacteria.
In this study, we investigated the influence of inorganic ions on the aggregation and deposition (adsorption) behavior of human adenovirus (HAdV). Experiments were conducted to determine the surface charge and size of HAdV and viral adsorption capacity of sand in different salt conditions. The interfacial potential energy was calculated using extended Derjaguin and Landau, Verwey and Overbeek (XDLVO) and steric hindrance theories to interpret the experimental results. Results showed that different compositions of inorganic ions have minimal effect on varying the iso-electric point pH (pHiep) of HAdV (ranging from 3.5 to 4.0). Divalent cations neutralized/shielded virus surface charge much more effectively than monovalent cations at pH above pHiep. Consequently, at neutral pH the presence of divalent cations enhanced the aggregation of HAdV as well as its adsorption to sand. Aggregation and adsorption behaviors generally agreed with XDLVO theory; however, in the case of minimal electrostatic repulsion, steric force by virus' fibers can increase the energy barrier and distance of secondary minimum, resulting in limited aggregation and deposition. Overall, our results indicated that subsurface water with low hardness residing in sandy soils may have a higher potential of being contaminated by HAdV.
