Counts of Campylobacter spp. on U.S. broiler carcasses

Foodborne Campylobacter-associated gastroenteritis remains a public health concern, and the Centers for Disease Control and Prevention suggests that improperly handled poultry is the most important source of this human disease. In response to these concerns, 10 of the largest U.S. poultry integrators cooperatively determined the incidence and counts of Campylobacter on processed broiler carcasses. Prior to conducting the survey, laboratory personnel were trained in a direct Campy-Cefex plating procedure for enumeration of the organism. Before and after the survey enumeration, consistency in reporting was compared among the participating laboratories. Participating laboratories were able to consistently estimate inoculated concentrations of Campylobacter in carcass rinses. Within the central study, we determined the potential exposure of U.S. consumers to Campylobacter spp. associated with broiler carcasses during a 13-month period. Among each of the 13 participating poultry complexes, rinses from 25 randomly selected fully processed carcasses were sampled monthly from individual flocks. Among 4200 samples, approximately 74% of the carcasses yielded no countable Campylobacter cells. Campylobacter spp. were isolated from approximately 3.6% of all commercially processed broiler carcasses at more than 10(5) CFU per carcass. Acceptable counts of these organisms on raw poultry carcasses remain to be determined. Nevertheless, this survey indicates industry recognition of its responsibility to assess and reduce public exposure to Campylobacter through broiler chickens.     

Tobacco-specific nitrosamines in new tobacco products.

New tobacco products, designed to attract consumers who are concerned about the health effects of tobacco, have been appearing on the market. Objective evaluation of these products requires, as a first step, data on their potentially toxic constituents. Tobacco-specific nitrosamines (TSNAs) are an important class of carcinogens in tobacco products, but virtually no data were available on their levels in these products. In the present study, we analyzed several new products-Ariva, Stonewall, Exalt, Revel, Smokey Mountain, and Quest-for TSNAs and compared their TSNA levels with those in nicotine replacement products and conventional smokeless tobacco and cigarette brands. TSNAs were not detected in Smokey Mountain, which is a tobacco-free snuff product. The lowest levels among the new products containing tobacco were in Ariva and Stonewall (0.26-0.28 microg/g wet weight of product). The highest levels in the new products were found in Exalt (3.3 microg/g tobacco), whereas Revel and Quest had intermediate amounts. Only trace amounts were found in nicotine replacement products, and conventional brands had levels consistent with those reported in the literature. These results demonstrate that TSNA levels in new tobacco products range from relatively low to comparable with those found in some conventional brands.     

A simple conceptual model for predicting the dissolution of phosphate rock in soils

Laboratory experimental and literature data were integrated to develop a simple, conceptual model to describe and predict the dissolution of a reactive phosphate rock (Gafsa phosphate rock, GPR) in soils. The model showed that initial solution Ca concentration strongly influences the time required for a single application of GPR (at 30 kgP ha^?1) to dissolve. The model predicts that all of the GPR will dissolve within a year of application in an unlimed, acid (pH_w 4.5) loam. However, if the soil has previously been limed to (pH_w 5.8, and contains permanent charge only, the model predicts that only about 50% of the GPR would have dissolved by the end of the second year after application. On the other hand, if a previously limed soil ((pH_w 5.8) contains variable-charge components, the model predicts that virtually all of the GPR would have dissolved in this soil by the end of the second year after application. These results emphasise that, even in the presence of a high proton supply, solution Ca has an overriding influence on the dissolution of GPR. The faster rate of GPR dissolution in the limed soil with variable charge, compared to that in the limed soil with permanent charge only, demonstrates the ability of the variable-charge component of soil to act as a sink for some of the lime-derived Ca. According to the solubility product principle, this allows more GPR to dissolve. Because of the generally stronger buffering of soil for P than for Ca, a relatively large proportion of any P removed by leaching and plant uptake is buffered by the sorbed phase. Consequently, the influence of leaching and plant uptake on GPR dissolution is attributed primarily to the removal of the relatively less-strongly buffered Ca.     

Modeling precipitation and sorption of elements during mixing of river water and porewater in the Coeur d'Alene River basin

Reddish brown flocs form along the edge of the Coeur d'Alene River when porewater drains into river water during the annual lowering of water level in the basin. The precipitates are efficient scavengers of dissolved elements and have characteristics that may make metals associated with them bioavailable. This work characterizes the geochemistry of the porewater and models the formation and composition of the flocs. Porewater is slightly acidic, has suboxic to anoxic characteristics, tends to have higher alkalinity, and contains elevated concentrations of many constituents relative to river water. Laboratory mixing experiments involving porewater and river water were done to produce the precipitates. Thermodynamic predictions using PHREEQC indicate that predicted amounts of ferrihydrite and gibbsite agree with removal of Fe and Al. Predictions of element removal by adsorption onto ferrihydrite are consistent with observed removal using a combination of surface complexation constants for the generalized two-layer model (As and Se), alternative surface constants derived from experiments at high sorbate-to-sorbent ratios (Cd, Co, Cu, Ni, Pb, and Zn), and adjusted surface constants to fit experimental data (Cr, Mo, and Sb). This new set of surface complexation constants needs further testing in other contaminated systems.     

Spectroscopic studies of the biosorption of gold(III) by dealginated seaweed waste

Gold biosorption by dealginated seaweed waste has been studied to elucidate the mechanisms of metal uptake from solution. Dealginated seaweed was able to retain up to 1 mmol g(-1) of Au from solution at pH 3. FT-IR showed the presence of carboxylate groups on the surface of the biosorbent; however, the changes observed for the Au-bound samples suggested very little sorption to the carboxyl moieties. Colloidal Au formed on the surface of dealginated seaweed by reduction of Au(III) to Au(0) was observed using ESEM and four different types of particles were clearly identified. The Au distribution matched closely that obtained for S atoms indicating a possible link between these elements. EXAFS measurements showed that colloidal Au is present on the surface of the biosorbent. Evidence of gold reduction from Au(III) to Au(I) and Au(0) was also confirmed by the measured bond distances characteristic of the metal. The coordination number obtained by EXAFS indicated that approximately 75% of the Au on the sample was present in the colloidal form and the remaining Au was bound to S as nearest neighbor. The proposed mechanisms for Au removal from solution are reduction of Au species by components on the surface of the biosorbent to form colloidal metal followed by retention of the ionic Au(I) species at the sulfur containing sites. The results show that dealginated seaweed can be used for the cleanup of gold-containing effluents.     

Lead sorption onto ferrihydrite. 3. Multistage contacting

Few studies have demonstrated the practical application of surface complexation models, calibrated with fundamental macroscopic and spectroscopic metal sorption data, in helping to solve industrial trace metal emissions problems. In this work, multistage ferrihydrite sorption systems are evaluated for their effectiveness in reducing single-solute lead(II) [Pb(II)] concentrations in contaminated water streams to very low levels. Experimental data and modeling results indicate that a multistage sorption system can significantly reduce Pb(II) effluent concentrations for the same total amount of sorbent or, alternatively, dramatically lower total sorbent consumption for the same effluent Pb(II) concentration. Model predictions were generated using a steady-state, multistage, equilibrium adsorber model that was specifically developed for and integrated into 0LI Systems' Environmental Simulation Program. The modified triple-layer model was used to simulate Pb(II) surface-liquid equilibria within the adsorber model. Engineering screening evaluations indicate that a 2-3-stage sorption process can provide significant economic savings when compared to a 1-stage process operating with the same target effluent Pb(II) concentration. Additional equilibrium stages beyond 2 or 3 provide diminishing economic returns. The major economic driver for multiple contacting stages is reduced capital investment and operating costs for sludge handling, dewatering, and disposal.     

Monochloramine versus sodium hypochlorite as antimicrobial agents for reducing populations of bacteria on broiler chicken carcasses

Studies were conducted to compare the effect of sodium hypochlorite (SH) versus monochloramine (MON) on bacterial populations associated with broiler chicken carcasses. In study 1, nominal populations (6.5 to 7.5 log CFU) of Escherichia coli, Listeria monocytogenes, Pseudomonas fluorescens, Salmonella serovars, Shewanella putrefaciens, and Staphylococcus aureus were exposed to sterilized chiller water (controls) or sterilized chiller water containing 50 ppm SH or MON. SH at 50 ppm eliminated all (6.5 to 7.5 log CFU) viable E. coli, L. monocytogenes, and Salmonella serovars; 1.2 log CFU of P. fluorescens; and 5.5 log CFU of S. putrefaciens. MON eliminated all (6.5 to 7.5 log CFU) viable E. coli, L. monocytogenes, S. putrefaciens, and Salmonella serovars and 4.2 log CFU of P. fluorescens. In study 2, chicken carcasses were inoculated with P. fluorescens or nalidixic acid-resistant Salmonella serovars or were temperature abused at 25 degrees C for 2 h to increase the populations of naturally occurring E. coli. The groups of Salmonella serovar-inoculated or temperature-abused E. coli carcasses were immersed separately in pilot-scale poultry chillers and exposed to tap water (controls) or tap water containing 20 ppm SH or 20 ppm MON for 1 h. The P. fluorescens-inoculated group was immersed in pilot-scale poultry chillers and exposed to tap water (controls) or tap water containing 50 ppm SH or 50 ppm MON for 1 h. Carcasses exposed to the SH treatment had nominal increases (0.22 log CFU) in E. coli counts compared with controls, whereas exposure to MON resulted in a 0.89-log reduction. Similarly, average nalidixic acid-resistant Salmonella serovar counts increased nominally by 34% (41 to 55 CFU/ml) compared with controls on carcasses exposed to SH, whereas exposure to MON resulted in an average nominal decrease of 80% (41 to 8 CFU/ml). P. fluorescens decreased by 0.64 log CFU on carcasses exposed to SH and decreased by 0.87 log CFU on carcasses exposed to MON. In study 3, SH or MON was applied to the chiller in a commercial poultry processing facility. E. coli counts (for carcass halves emerging from both saddle and front-half chillers) and Salmonella prevalence were evaluated. Data from carcasses exposed to SH during an 84-day historical (Hist) and a 9-day prepilot (Pre) period were evaluated. Other carcasses were exposed to MON and tested during a 27-day period (Test). E. coli counts for samples collected from the saddle chiller were 25.7, 25.2, and 8.6 CFU/ml for Hist, Pre, and Test, respectively. E. coli counts for samples collected from the front-half chiller were 6.7, 6.9, and 2.5 CFU/ml for Hist, Pre, and Test, respectively. Salmonella prevalence was reduced from 8.7% (Hist + Pre) to 4% (Test). These studies indicate that MON is superior to SH in reducing microbial populations in poultry chiller water.     

Transport of chemical and microbial compounds from known wastewater discharges: potential for use as indicators of human fecal contamination

The quality of drinking and recreational water is currently (2005) determined using indicator bacteria. However, the culture tests used to analyze forthese bacteria require a long time to complete and do not discriminate between human and animal fecal material sources. One complementary approach is to use chemicals found in human wastewater, which would have the advantages of (1) potentially shorter analysis times than the bacterial culture tests and (2) being selected for human-source specificity. At 10 locations, water samples were collected upstream and at two successive points downstream from a wastewaster treatment plant (WWTP); a treated effluent sample was also collected at each WWTP. This sampling plan was used to determine the persistence of a chemically diverse suite of emerging contaminants in streams. Samples were also collected at two reference locations assumed to have minimal human impacts. Of the 110 chemical analytes investigated in this project, 78 were detected at least once. The number of compounds in a given sample ranged from 3 at a reference location to 50 in a WWTP effluent sample. The total analyte load at each location varied from 0.018 microg/L at the reference location to 97.7 microg/L in a separate WWTP effluent sample. Although most of the compound concentrations were in the range of 0.01-1.0 microg/L, in some samples, individual concentrations were in the range of 5-38 microg/L. The concentrations of the majority of the chemicals present in the samples generally followed the expected trend: they were either nonexistent or at trace levels in the upstream samples, had their maximum concentrations in the WWTP effluent samples, and then declined in the two downstream samples. This research suggests that selected chemicals are useful as tracers of human wastewater discharge.     

Start-up, microbial community analysis and formation of aerobic granules in a tert-butyl alcohol degrading sequencing batch reactor

We demonstrate that compact well-settling aerobic granules can be developed in a sequencing batch reactor (SBR) for the biological removal of tert-butyl alcohol (TBA) using a strategy involving step increases in TBA loading rate achieved through increasing TBA concentrations in the influent. A moderate selection pressure that included a cycle time of 24 h and a start-of-cycle TBA concentration of 100 mg/L was initially introduced to encourage the growth and retention of biomass and avoid biomass loss from hydraulic washout. Start-of-cycle TBA concentrations were increased to 150, 300, 450, and 600 mg/L on days 90, 100, 121, and 199, respectively. These increases were only introduced after complete TBA removal was accompanied by visible improvements in biomass concentration and biomass settling ability. This acclimation strategy produced incrementally higher biomass concentrations and better settling biomass with higher specific TBA biodegradation rates. Effluent TBA concentrations were consistently below the detection limit of 25 microg/L. Aerobic granules were first observed about 180 days after reactor start-up. The granules had a clearly defined shape and appearance, settled significantly faster than the suspended sludge in the reactor, and eventually became the dominant form of biomass in the reactor. The adapted granules were capable of complete TBA removal and contained a stable microbial population with a low diversity of sequences of community 16S rRNA gene fragments. This study indicates that it is possible to use aerobic granules for TBA remediation and will contribute to a better understanding of how microbial acclimation can be exploited in the SBR to biologically remove recalcitrant xenobiotics.     

Aluminum control of phosphorus sorption by lake sediments

Release of reactive (phosphate-like) phosphorus (P) from freshwater sediments represents a significant internal P source for many lakes. Hypolimnetic P release occurs under reducing conditions that cause reductive dissolution of ferric hydroxide [Fe(OH)3]. This hypolimnetic P release may be naturally low or artificially reduced by sediment with naturally high or artificially elevated concentrations of aluminum hydroxide [Al(OH)3]. We presentfield and laboratory data for a common extraction analysis of sediments from 43 lakes differing in trophic status, pH regime, climate, and P loading. The results indicate that a simple sequential extraction of sediment may be a useful predictor of sediment's ability to release P. Sequential extractions of sediment P, Al, and Fe by water (H2O), bicarbonate-dithionite (BD), and NaOH (at 25 degrees C) showed that negligible amounts of P would be released from lake sediments during hypolimnetic anoxia if either (1) the molar Al(NaOH-25):Fe(BD) ratio is > 3 or (2) the molar Al(NaOH-25):P(H2O+BD) ratio is > 25. These ratios can be used as operational targets for estimation of sediment P release potential and Al dosing of P-rich sediment to prevent hypolimnetic P release under anoxic conditions.