Daniel L. Gallagher

Nickel stimulation of anaerobic digestion

Abstract An acetate-enriched methanogenic culture was assayed for nutritional stimulation by nickel in combination with other inorganic and organic nutrients, i.e. iron, cobalt, yeast extract, riboflavin and vitamin B12. Acetate was automatically maintained at 2–3 g l−1 by a pH Stat system so that substrate was not limiting. In the absence of nickel, the specific acetate utilization rates were in the range of 2–4.6 g acetate g−1 VSS day−1. In the presence of nickel, this rate was as high as 10 and when both nickel and yeast extract were supplemented this rate temporarily increased to 12–15 g acetate g−1 VSS day−1 . The maximum acetate utilization rate was observed to be 51 g l−1 day−1 as compared to 3.3 g l−1 day−1 for conventional high-rate digestion. Daily phosphate additions were required to sustain these high acetate utilization rates. An acetate utilization rate of 20–30 g l−1 day−1 was maintained for over 25 days. Microscopic examination of the culture revealed a predominance of a sarcina whenever stimulation was noted.

A comparative risk assessment for Listeria monocytogenes in prepackaged versus retail-sliced deli meat.

Deli meat was ranked as the highest-risk ready-to-eat food vehicle of Listeria monocytogenes within the 2003 U.S. Food and Drug Administration and U.S. Department of Agriculture, Food Safety and Inspection Service risk assessment. The comparative risk of L. monocytogenes in retail-sliced versus prepackaged deli meats was evaluated with a modified version of this model. Other research has found that retail-sliced deli meats have both higher prevalence and levels of L. monocytogenes than have product sliced and packaged at the manufacturer level. The updated risk assessment model considered slicing location as well as the use of growth inhibitors. The per annum comparative risk ratio for the number of deaths from retail-sliced versus prepackaged deli meats was found to be 4.89, and the per-serving comparative risk ratio was 4.27. There was a significant interaction between the use of growth inhibitors and slicing location. Almost 70% of the estimated deaths occurred from retail-sliced product that did not possess a growth inhibitor. A sensitivity analysis, assessing the effect of the models consumer storage time and shelf life assumptions, found that even if retail-sliced deli meats were stored for a quarter of the time prepackaged deli meats were stored, retail-sliced product is 1.7 times more likely to result in death from listeriosis. Sensitivity analysis also showed that the shelf life assumption had little effect on the comparative risk ratio.

Treatment of clam processing wastewaters by means of upflow anaerobic sludge blanket technology

Abstract The ability of upflow anaerobic sludge blanket (UASB) technology to treat wastewaters from a mechanical shucking, clam processing facility was evaluated. Both batch and continuous flow studies were performed at approx. 32°C to evaluate the effects of varying organic loading rate (OLR), hydraulic residence time (HRT), NaCl level, and nutrient additions. Among the parameters measured were biochemical oxygen demand (BOD 5 ), chemical oxygen demand (COD), total suspended solids (TSS), various nutrients and gas production. The UASB system proved to be effective, accomplishing soluble BOD 5 , soluble COD, and TSS removals of 87, 83 and 83%, respectively, under the best conditions considered (average OLR = 13.8 g COD/l/d and average HRT = 3 h). The average conversion of wastewater organics to methane was in the area of 80‰. Sodium levels at and about 5250 mg/l significantly impacted on the performance of the UASB.

Listeria monocytogenes in Retail Delicatessens: an Interagency Risk Assessment-model and baseline results.

The Interagency Risk Assessment-Listeria monocytogenes (Lm) in Retail Delicatessens provides a scientific assessment of the risk of listeriosis associated with the consumption of ready-to-eat (RTE) foods commonly prepared and sold in the delicatessen (deli) of a retail food store. The quantitative risk assessment (QRA) model simulates the behavior of retail employees in a deli department and tracks the Lm potentially present in this environment and in the food. Bacterial growth, bacterial inactivation (following washing and sanitizing actions), and cross-contamination (from object to object, from food to object, or from object to food) are evaluated through a discrete event modeling approach. The QRA evaluates the risk per serving of deli-prepared RTE food for the susceptible and general population, using a dose-response model from the literature. This QRA considers six separate retail baseline conditions and provides information on the predicted risk of listeriosis for each. Among the baseline conditions considered, the model predicts that (i) retail delis without an environmental source of Lm (such as niches), retail delis without niches that do apply temperature control, and retail delis with niches that do apply temperature control lead to lower predicted risk of listeriosis relative to retail delis with niches and (ii) retail delis with incoming RTE foods that are contaminated with Lm lead to higher predicted risk of listeriosis, directly or through cross-contamination, whether the contaminated incoming product supports growth or not. The risk assessment predicts that listeriosis cases associated with retail delicatessens result from a sequence of key events: (i) the contaminated RTE food supports Lm growth; (ii) improper retail and/or consumer storage temperature or handling results in the growth of Lm on the RTE food; and (iii) the consumer of this RTE food is susceptible to listeriosis. The risk assessment model, therefore, predicts that cross-contamination with Lm at retail predominantly results in sporadic cases.

Contaminant diffusion, solubility, and material property differences between HDPE and PEX potable water pipes.

The objectives of this work were to identify differences between the composition, bulk properties, contaminant diffusivity and solubility for new high-density polyethylene (HDPE) pipe and crosslinked polyethylene (PEX) pipe, as well as determine which contaminant and polymer properties are useful for predicting contaminant fate in water pipe. Variations in PE pipe density ( 0.9371–0.9547 g/ cm3 ) , crystallinity (69–72%), crosslinking (60 and 76%), and oxidative induction time (33 to >295 min .) were detected. While numerically these differences seem minor, results show that slight material differences have a notable effect on contaminant diffusivity and solubility. Nonpolar contaminant diffusivity and solubility were best predicted by bulk density. Polar contaminants were more soluble and diffused faster through PEX than HDPE pipes because PEX pipes contained a greater amount of oxygen. For all materials, dipole moment and Log Kow were good predictors of contaminant fate and molecular volume was only use...

Impact of Chlorinated Water Exposure on Contaminant Transport and Surface and Bulk Properties of High-Density Polyethylene and Cross-Linked Polyethylene Potable Water Pipes

The aim of this work was to determine if the aging of polyethylene (HDPE, PEX-A and PEX-B) water pipes by exposure to chlorinated water altered polar and nonpolar contaminant diffusivity and solubility by analyzing new, laboratory-aged, and exhumed water- distribution system polyethylene (PE) pipes. After 141 days of aging in pH 6.5 water with 45 mg=L free chlorine, the surface chemistry and bulk properties of PEX-A pipe were unaffected. Carbonyl bonds (σ ¼ 1;713 cm � 1 ) were detected on the surfaces of HDPE and PEX-B pipe, and these oxygenated surfaces became more hydrophilic, resulting in statistically significant increases in diffusion rates. All 10 contaminant and four pipe material combinations had diffusivity increases on average of 50% for polar contaminants and 5% for nonpolar contaminants. Contaminant solubility was slightly increased for aged PEX-A and slightly decreased for PEX-B pipes. Toluene and trichloromethane diffusivity and solubility values for 7- to 25-year-old buried water utility pipes were similar to values for new and laboratory-aged HDPE-based materials. Because chlorinated water exposure alters how polar contaminants interact with aged PE pipes, results of this work should be considered in future health risk assessments, water quality modeling, pipe performance, and service-life considerations. DOI: 10.1061/(ASCE)EE.1943-7870.0000366.

Survey for Listeria monocytogenes in and on Ready-to-Eat Foods from Retail Establishments in the United States (2010 through 2013): Assessing Potential Changes of Pathogen Prevalence and Levels in a Decade

A multiyear interagency Listeria monocytogenes Market Basket Survey was undertaken for selected refrigerated ready-to-eat foods purchased at retail in four FoodNet sites in the United States. Food samples from 16 food categories in six broad groups (seafood, produce, dairy, meat, eggs, and combination foods) were collected weekly at large national chain supermarkets and independent grocery stores in California, Maryland, Connecticut, and Georgia for 100 weeks between December 2010 and March 2013. Of the 27,389 total samples, 116 samples tested positive by the BAX PCR system for L. monocytogenes , and the pathogen was isolated and confirmed for 102 samples. Among the 16 food categories, the proportion of positive samples (i.e., without considering clustering effects) based on recovery of a viable isolate of L. monocytogenes ranged from 0.00% (95% confidence interval: 0.00, 0.18) for the category of soft-ripened and semisoft cheese to 1.07% (0.63, 1.68) for raw cut vegetables. Among the 571 samples that tested positive for Listeria-like organisms, the proportion of positive samples ranged from 0.79% (0.45, 1.28) for soft-ripened and semisoft cheese to 4.76% (2.80, 7.51) for fresh crab meat or sushi. Across all 16 categories, L. monocytogenes contamination was significantly associated with the four states (P < 0.05) but not with the packaging location (prepackaged by the manufacturer versus made and/or packaged in the store), the type of store (national chain versus independent), or the season. Among the 102 samples positive for L. monocytogenes , levels ranged from <0.036 most probable number per g to 6.1 log CFU/g. For delicatessen (deli) meats, smoked seafood, seafood salads, soft-ripened and semisoft cheeses, and deli-type salads without meat, the percentage of positive samples was significantly lower (P < 0.001) in this survey than that reported a decade ago based on comparable surveys in the United States. Use of mixed logistic regression models to address clustering effects with regard to the stores revealed that L. monocytogenes prevalence ranged from 0.11% (0.03, 0.34) for sprouts (prepackaged) to 1.01% (0.58, 1.74) for raw cut vegetables (prepackaged).

Listeria monocytogenes in Retail Delicatessens: An Interagency Risk Assessment-Risk Mitigations.

Cross-contamination, improper holding temperatures, and insufficient sanitary practices are known retail practices that may lead to product contamination and growth of Listeria monocytogenes. However, the relative importance of control options to mitigate the risk of invasive listeriosis from ready-to-eat (RTE) products sliced or prepared at retail is not well understood. This study illustrates the utility of a quantitative risk assessment model described in a first article of this series (Pouillot, R., D. Gallagher, J. Tang, K. Hoelzer, J. Kause, and S. B. Dennis, J. Food Prot. 78:134-145, 2015) to evaluate the public health impact associated with changes in retail deli practices and interventions. Twenty-two mitigation scenarios were modeled and evaluated under six different baseline conditions. These scenarios were related to sanitation, worker behavior, use of growth inhibitors, cross-contamination, storage temperature control, and reduction of the level of L. monocytogenes on incoming RTE food products. The mean risk per serving of RTE products obtained under these scenarios was then compared with the risk estimated in the baseline condition. Some risk mitigations had a consistent impact on the predicted listeriosis risk in all baseline conditions (e.g. presence or absence of growth inhibitor), whereas others were greatly dependent on the initial baseline conditions or practices in the deli (e.g. preslicing of products). Overall, the control of the bacterial growth and the control of contamination at its source were major factors of listeriosis risk in these settings. Although control of cross-contamination and continued sanitation were also important, the decrease in the predicted risk was not amenable to a simple solution. Findings from these predictive scenario analyses are intended to encourage improvements to retail food safety practices and mitigation strategies to control L. monocytogenes in RTE foods more effectively and to demonstrate the utility of quantitative risk assessment models to inform risk management decisions.

PILOT PERFORMANCE OF DEEP U-TUBES

U-Tube aeration has received considerable attention recently as part of a modification of the activated sludge process called “Deep Shaft” treatment. Presently there is only limited data on aeration characteristics of deep U-Tubes showing the effect of velocity, depth and gas/water injection ratios. This study determined the increase in dissolved oxygen, the oxygen absorption efficiency and the head loss across a 0.1 m diameter U-Tube for the following parameters: Velocity 0.9, 1.4, 1.8 m/s Depth 12, 30, 61, 103 m. Oxygen 4, 7 1/2, 25 percent O2/water ratio Air 5, 15, 25 percent air/water ratio Tap water was passed through the system for all of the above parametric conditions. In addition, 5 mg/1 of an anionic detergent was injected into the tap water to simulate domestic wastewater as recommended by the British. Also, in other tests, 100 mg/1 of Bentonite clay was injected into the tap water to simulate the colloids in domestic wastewater which provide nuclei for effervescence of supersaturated dissolved gases. Air injection at 25% air/water ratio indicated considerable improvement in Δ D. O. Using tap water a change from 30 to 61 m. depth caused the Δ D. O. to increase from 11 mg/1 to 17 mg/1. When pure oxygen was injected, however, at 25% oxygen/water ratio at 30 m. depth, the Δ D. O. was 68 mg/1 and increased to 95 mg/1 at 61 m. Negligible increases were noted in Δ D. O. at 103 m. depth. Over the velocity range investigated (0.9 to 1.8 m/s) there was no significant effect on Δ D.O. The maximum absorption efficiency for pure oxygen at 7.5% O2/water was observed to be 52% in the 103 meter deep U-Tube, demonstrating that the U-Tube requires capture and recycle of the off-gases if it is to be used in an efficient manner as the absorption system for an oxygen activated sludge system. The maximum oxygen transfer economy with air injection was 4 kg O2/kw-hr with 15% air/water injection ratio at 61 m. depth producing an effluent containing 21 mg/1 D.O. (Δ D. O. = 15 mg/1 220% saturation). The estimated total cost, amortization and operation, per ton of oxygen absorbed from air would be

Predicting Permeation of Organic Contaminants into Polyethylenes

23/ton of oxygen compared with