Evaluating the efficiency and temporal variation of pilot-scale constructed wetlands and steel slag phosphorus removing filters for treating dairy wastewater.

The performance and temporal variation of three hybrid and three integrated, saturated flow, pilot-scale constructed wetlands (CWs) were tested for treating dairy farm effluent. The three hybrid systems each consisted of two CWs in-series, with horizontal and vertical flow. Integrated systems consisted of a CW (horizontal and vertical flow) followed by a steel slag filter for removing phosphorus. Time series temporal semivariogram analyses of measured water parameters illustrated different treatment efficiencies existed over the course of one season. As a result, data were then divided into separate time period groups and CW systems were compared using ANOVA for parameter measurements within each distinct time period group. Both hybrid and integrated CWs were efficient in removing organics; however, hybrid systems had significantly higher performance (p<0.05) during peak vegetation growth. Compared to hybrid CWs, integrated CWs achieved significantly higher DRP reduction (p<0.05) throughout the period of investigation and higher ammonia reduction (p<0.05) in integrated CWs was observed in late summer. Geochemical modeling demonstrates hydroxyapatite and vivianite minerals forming on steel slag likely control the fate of phosphate ions given the reducing conditions prevalent in the system. The model also demonstrates how the wastewater:slag ratio can be adjusted to maximize phosphorus removal while staying at a near-neutral pH.

Cloning and in situ expression studies of the Hydrogenobaculum arsenite oxidase genes.

Novel arsenite [As(III)] oxidase structural genes (aoxAB) were cloned from Hydrogenobaculum bacteria isolated from an acidic geothermal spring. Reverse transcriptase PCR demonstrated expression throughout the outflow channel, and the aoxB cDNA clones exhibited distribution patterns relative to the physicochemical gradients in the spring. Microelectrode analyses provided evidence of quantitative As(III) transformation within the microbial mat.

New evidence for rejuvenation of phosphorus retention capacity in EAF steel slag.

The purpose of this research was to investigate phosphorus (P) retention capacity and rejuvenation potential of electric arc furnace (EAF) steel slag from Quebec and New Zealand (NZ) iron melter slag (IMS). Columns filled with slag materials were fed with dairy effluent and subjected to two feeding and one resting cycle(s). P retention capacities and rejuvenation potentials were determined after each feeding cycle. Elemental composition and mineralogical analysis were performed on IMS samples. Finally, chemical fractionation analysis was conducted on both NZ IMS and Quebec EAF steel slags. The results revealed that initiating a resting period in EAF steel slag filters prior to reaching their P saturation point increased the overall filter P retention capacity by 49.5 and 42.4% compared to 28% in a filter which had its resting period initiated after reaching P saturation. The rejuvenation property could play a significant role in full-scale applications by prolonging life expectancy and increasing cost efficiency. P retention and rejuvenation by NZ slag materials was negligible relative to EAF steel slag material from Quebec. Chemical fractionation analysis revealed differences between materials, indicating that the highest quantities of P were bound to Ca and Fe in EAF steel slag and to Ca and Al fractions in iron melter slag. This study also demonstrates that slag's performance is dependent on the source of the material and the steel making practices. Therefore, testing of the P adsorptive capability and, if relevant, the rejuvenation potential of individual steel mill slags, should be a prerequisite prior to their use in field applications.

Relative importance of H2 and H2S as energy sources for primary production in geothermal springs.

Geothermal waters contain numerous potential electron donors capable of supporting chemolithotrophy-based primary production. Thermodynamic predictions of energy yields for specific electron donor and acceptor pairs in such systems are available, although direct assessments of these predictions are rare. This study assessed the relative importance of dissolved H(2) and H(2)S as energy sources for the support of chemolithotrophic metabolism in an acidic geothermal spring in Yellowstone National Park. H(2)S and H(2) concentration gradients were observed in the outflow channel, and vertical H(2)S and O(2) gradients were evident within the microbial mat. H(2)S levels and microbial consumption rates were approximately three orders of magnitude greater than those of H(2). Hydrogenobaculum-like organisms dominated the bacterial component of the microbial community, and isolates representing three distinct 16S rRNA gene phylotypes (phylotype = 100% identity) were isolated and characterized. Within a phylotype, O(2) requirements varied, as did energy source utilization: some isolates could grow only with H(2)S, some only with H(2), while others could utilize either as an energy source. These metabolic phenotypes were consistent with in situ geochemical conditions measured using aqueous chemical analysis and in-field measurements made by using gas chromatography and microelectrodes. Pure-culture experiments with an isolate that could utilize H(2)S and H(2) and that represented the dominant phylotype (70% of the PCR clones) showed that H(2)S and H(2) were used simultaneously, without evidence of induction or catabolite repression, and at relative rate differences comparable to those measured in ex situ field assays. Under in situ-relevant concentrations, growth of this isolate with H(2)S was better than that with H(2). The major conclusions drawn from this study are that phylogeny may not necessarily be reliable for predicting physiology and that H(2)S can dominate over H(2) as an energy source in terms of availability, apparent in situ consumption rates, and growth-supporting energy.

Niche differentiation among sulfur-oxidizing bacterial populations in cave waters.

The sulfidic Frasassi cave system affords a unique opportunity to investigate niche relationships among sulfur-oxidizing bacteria, including epsilonproteobacterial clades with no cultivated representatives. Oxygen and sulfide concentrations in the cave waters range over more than two orders of magnitude as a result of seasonally and spatially variable dilution of the sulfidic groundwater. A full-cycle rRNA approach was used to quantify dominant populations in biofilms collected in both diluted and undiluted zones. Sulfide concentration profiles within biofilms were obtained in situ using microelectrode voltammetry. Populations in rock-attached streamers depended on the sulfide/oxygen supply ratio of bulk water (r=0.97; P<0.0001). Filamentous epsilonproteobacteria dominated at high sulfide to oxygen ratios (>150), whereas Thiothrix dominated at low ratios (<75). In contrast, Beggiatoa was the dominant group in biofilms at the sediment-water interface regardless of sulfide and oxygen concentrations or supply ratio. Our results highlight the versatility and ecological success of Beggiatoa in diffusion-controlled niches, and demonstrate that high sulfide/oxygen ratios in turbulent water are important for the growth of filamentous epsilonproteobacteria.

Sulfur geochemistry of hydrothermal waters in Yellowstone National Park, Wyoming, USA. III. An anion-exchange resin technique for sampling and preservation of sulfoxyanions in natural waters.

A sampling protocol for the retention, extraction, and analysis of sulfoxyanions in hydrothermal waters has been developed in the laboratory and tested at Yellowstone National Park and Green Lake, NY. Initial laboratory testing of the anion-exchange resin Bio-Rad™ AG1-X8 indicated that the resin was well suited for the sampling, preservation, and extraction of sulfate and thiosulfate. Synthetic solutions containing sulfate and thiosulfate were passed through AG1-X8 resin columns and eluted with 1 and 3 M KCl, respectively. Recovery ranged from 89 to 100%. Comparison of results for water samples collected from five pools in Yellowstone National Park between on-site 1C analysis (U.S. Geological Survey mobile lab) and IC analysis of resin-stored sample at SUNY-Stony Brook indicates 96 to 100% agreement for three pools (Cinder, Cistern, and an unnamed pool near Cistern) and 76 and 63% agreement for two pools (Sulfur Dust and Frying Pan). Attempts to extract polythionates from the AG1-X8 resin were made using HCl solutions, but were unsuccessful. Bio-Rad™ AG2-X8, an anion-exchange resin with weaker binding sites than the AG1-X8 resin, is better suited for polythionate extraction. Sulfate and thiosulfate extraction with this resin has been accomplished with KCl solutions of 0.1 and 0.5 M, respectively. Trithionate and tetrathionate can be extracted with 4 M KCl. Higher polythionates can be extracted with 9 M hydrochloric acid. Polythionate concentrations can then be determined directly using ion chromatographic methods, and laboratory results indicate recovery of up to 90% for synthetic polythionate solutions using AG2-X8 resin columns.