Gregory D. Boardman

Fate of azo dyes in sludges

Abstract Batch sludge digestion studies were conducted under aerobic and anaerobic conditions to study: (i) the role of vinyl sulfone and hydroxyl functional groups in the removal of Reactive Black 5 dye; and (ii) the effect of biomass concentration on the removal of Navy 106 (mixture of three azo dyes) from a textile mill wash water. Removals of color and organic content under aerobic and anaerobic conditions were compared. The potential of the dyes to leach from sludge in landfills was also investigated using the toxicity characteristic leaching procedure (TCLP). The vinyl sulfone group of the Reactive Black 5 dye enabled the dye to be removed better than the hydrolyzed form of the dye under aerobic conditions. Sorption and aerobic color degradation of Navy 106 wash water increased with increased biomass concentration in the reactors. An inhibition to color removal from dye wash water under aerobic conditions was detected at high color-to-biomass ratios. The inhibition was accompanied by a lower rate of nitrate and sulfate release. The total organic carbon (TOC) and chemical oxygen demand (COD) of hydrolyzed Reactive Black 5 dye and Navy 106 wash water decreased under aerobic conditions. Under anaerobic conditions, the color degraded within a day, but the TOC and COD of the pure dye and wash water did not decrease. TCLP extracts contained little, if any, of the dye added to the suspended growth reactors.

Factors influencing the nitrification efficiency of fluidized bed filter with a plastic bead medium

The performance of fluidized bed nitrification filters charged with 2×4 ABS plastic beads (specific gravity 1.06) was evaluated. Three unique bed-height to diameter ratios were established, in triplicate, using column diameters of 12.7, 15.2 and 17.8 cm. Filters received water spiked with recycled nutrients and ammonia (TAN), from one of the three 500 l feed tank system. With daily ammonia loading fixed at 8.6 g per system, TAN removal increased with column diameter at each of four tests hydraulic loading rates (6, 8, 10 and 12 Lpm). TAN in recirculated water (influent) rose from 0.5 to 1.0 mg/l as ammonia loading increased from 180 mg/m2-day to 360 mg/m2-day. When hydraulic loading was fixed at 12 Lpm, TAN removal (%) was maximized with ammonia loadings ranging from 225 to 270 mg/m2-day. Biofilm thickness increased with ammonia loading, but decreased with increased hydraulic loading rates. Fluidized beds of ABS plastic beads were effective in reducing energy costs (head loss) of water treatment.

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.

Identification of Bacterial Pathogens in Biofilms of Recirculating Aquaculture Systems

Abstract Biofilms are capable of forming on all aquaculture system components, incorporating the various microflora present in the water. Pathogenic bacteria released from the biofilms are potentially capable of causing recurring diseases. Seven recirculating freshwater and two recirculating saltwater facilities were sampled, with eight different types of materials tested. Pathogenic bacteria were identified using standard bacteriological methods and commercial kits. The most significant human pathogens were Bacillus cereus, Shigella spp. and Vibrio spp. The major piscine pathogens of concern were Photobacterium damsela, Vibrio spp., and Aeromonas hydrophila. The most significant variation in biofilm pathogen occurrence was observed between facilities and not between construction materials. This study implicates biofilms as another reservoir for pathogenic bacteria in recirculating aquaculture systems.

Effect of acid stress, antibiotic resistance, and heat shock on the resistance of Listeria monocytogenes to UV light when suspended in distilled water and fresh brine.

Exposure to sublethal processing treatments can stimulate bacterial stress responses. The purpose of this research was to determine whether adaptation to common food processing stresses encountered during the preparation of ready-to-eat foods affects the dose of UV light required to significantly reduce Listeria monocytogenes populations in sterile distilled water and a 9% NaCl solution, using uridine as a chemical actinometer. L. monocytogenes strains N1-227 (from hot dog batter), N3-031 (from turkey franks), and R2-499 (from ready-to-eat meat) were acid stressed for 3 h at 35 degrees C in Trypticase soy broth with yeast extract acidified to pH 5.0, heat shocked for 1 h at 48 degrees C in brain heart infusion broth (BHIB), and selected for sulfanilamide resistance (512 microg/ml). These strains were then mixed in equal proportions and suspended in water and 9% NaCl solution, each containing 10(-4) M uridine. Samples were exposed to UV light (253.7 nm) for 0, 5, 10, 15, 20, 25, or 30 min. Inactivation was evaluated by surface plating onto modified Oxford agar and Trypticase soy agar with yeast extract and by enrichment in BHIB followed by incubation at 37 degrees C for 24 h. The absorbance of each sample was measured before and after irradiation to calculate the dose of UV light. There were no significant differences between population estimates based on medium or suspension solution. There were no population differences between acid-stressed and antibiotic-resistant or unstressed and heat-shocked L. monocytogenes strains. However, acid-stressed and antibiotic-resistant strains were significantly more resistant to UV light than were unstressed and heat-shocked strains (P < or = 0.05).

Dose of UV light required to inactivate Listeria monocytogenes in distilled water, fresh brine, and spent brine.

The purpose of this research was to establish the dose of UV light (253.7 nm) needed to inactivate Listeria monocytogenes in distilled water, fresh brine (9% NaCl), spent brine, and diluted (5, 35, and 55%) spent brine, using uridine as a chemical actinometer. Strains N1-227 (isolated from hot dog batter), N3-031 (isolated from turkey franks), and R2-499 (isolated from meat) were mixed in equal proportions and suspended in each solution prepared so as to contain 10(-4) M uridine. Samples were irradiated in sterile quartz cells for 0, 5, 10, 15, 20, 25, or 30 min. Inactivation was evaluated by serially diluting samples in 0.1% peptone, by surface plating in duplicate onto modified Oxford agar and Trypticase soy agar with yeast extract, and by enrichment in brain heart infusion broth, followed by incubation at 37 degrees C for 24 to 48 h. For dose measurements, the absorbance (262 nm) was measured before and after irradiation. Differences were observed in population estimates depending on the solution (P < or = 0.05). Reductions were as follows from greatest to least: water > fresh brine > 5% spent brine > 35% spent brine > 55% spent brine > undiluted spent brine. UV light did not significantly reduce populations suspended in spent brine solutions. L. monocytogenes decreased to below the detection limit (1 log CFU/ml) at doses greater than 33.2 mJ/cm(2) in water and at doses greater than 10.3 mJ/cm(2) in fresh brine. Knowledge of UV dosing required to control L. monocytogenes in brines similar to those used for ready-to-eat meat processing will aid manufacturers in establishing appropriate food safety interventions for these products.

Response of Bacterial Biofilms in Recirculating Aquaculture Systems to Various Sanitizers

ABSTRACT Pathogenic microorganisms may be incorporated into biofilms found in aquaculture systems, causing recurring exposure to potential disease agents. Aerobic plate counts, the presence of Enterobacteriaceae, and the presence of Escherichia coli, modified to express a green fluorescent protein (GFP E. coli), was used to evaluate the effectiveness of various sanitizers in decreasing bacterial incorporation into newly generated biofilms in recirculating aquaculture systems. Disks of Buna-N rubber, polyvinyl chloride (PVC), chlorinated PVC, glass, fiberglass, and stainless steel were placed in aquariums stocked with Nile tilapia, Oreochromis niloticus. The effectiveness of water, an alkaline cleanser, sodium hypochlorite, a quaternary ammonium compound, or peracetic acid as a sanitizer was evaluated on each substrate by enumerating total plate counts, GFP E. coli, and Enterobacteriaceae. Sodium hypochlorite and peracetic acid were the most effective sanitizers, with an overall percentage reduction of GFP E. coli of approximately 2 logs10. The quaternary ammonium compound was moderately effective, 1 log10, against the target organisms. Water demonstrated a 2 log10 reduction of the total plate count, suggesting that some mechanical cleaning was achieved. The type of material used as substrate for the biofilm had no significant (P > 0.05) effect on the effectiveness of the sanitizers.

Onsite aerobic package treatment systems

Abstract Several studies were conducted to evaluate the performance of onsite aerobic package treatment systems (APTS), and to suggest operational and design modifications. In the first phase, five APTS in southwest Virginia were found to be operating poorly (average BOD 5 = 69.4 mg/l, TSS = 99 mg/l, TKN = 18.6 mg/l), often violating Virginia effluent standards. Mechanical failures, improper maintenance and design were identified as causing the poor performance. In the second phase, excessive hydraulic retention time (HRT) in field systems (over 3 days) was identified as a significant design problem. Laboratory systems operating with aeration basin HRTs of 0.5 to 2 days produced better effluent quality (average BOD 5 = 19 mg/l, TSS = 29 mg/l, TKN = 0.7 mg/l). In a separate experiment relatively high levels of laundry detergent did not significantly affect laboratory system performance. Finally, a field experiment was conducted to determine the effect of equalizing washing machine flow on the operation of an APTS. An improvement in system performance and stability was observed. Based on these studies, potential design and operational modifications are suggested, including improved maintenance, reduction of aeration basin HRT, and equalization of wastewater flow.

Pesticides (OCPs) and Polychlorinated Biphenyls (PCBs) Concentration in Various Fish Species Along the Chesapeake Bay Near Virginia Beach on the Atlantic Coastline

The accumulation of polychlorinated biphenyls (PCBs), � DDTs, � chlordanes, � BHCs, dieldrin, heptachlor ep- oxide and other organochlorinated pesticides (OCPs) was measured in the tissues of different edible fishes collected along the Virginia Coast by employing the methods: MSPD (Matrix Solid Phase Dispersion) and GC-ECD (Gas Chromatogra- phy with Electron Capture Detector). BHC4s were the most predominant contaminants, followed by PCBs, chlordanes, dieldrin and the other OCPs. This study revealed that over the last decade, the concentrations of OCPs have declined in these regions. Even with this decline, the measured concentrations of PCBs and OCPs in edible fish are still worth report- ing. It was observed, that concentrations of organochlorines were significantly in same range (low-high) with one another and were in the range of a few to several ngg � 1 on a wet weight basis. In the tissue samples, � OCPs ranged from 4.30-196 ngg � 1 w.w withBHC (266.101 ngg � 1 w.w) and Heptachlor epoxide (196 ngg � 1 w.w) collectively in all fish. SimilarlyPCBs had an overall range 7.17-276.16 ngg � 1 w.w where Aroclor 1221 and Aroclor 1242 were the dominant components. The redox conditions and the decay processes which affect the organic matter, control the concentrations of PCBs and OCPs in edible fish. These preliminary results suggest that the variations in PCBs and OCPs content in edible fish result largely from digenetic processes rather than changes in pesticide input resulting from local human activities.

Effect of high hydrostatic pressure processing on freely suspended and bivalve-associated T7 bacteriophage.

The effectiveness of hydrostatic pressure processing (HPP) for inactivating viruses has been evaluated in only a limited number of studies, and most of the work has been performed with viruses freely suspended in distilled water. In this work, HPP inactivation of freely suspended and shellfish-associated bacteriophage T7 was studied. T7 was selected in hopes that it could serve as a model for animal virus behavior. Clams (Mercenaria mercenaria) and oysters (Crassostrea virginica) were homogeneously blended separately and inoculated with bacteriophage T7. The inoculated bivalve meat and the freely suspended virus samples were subjected to HPP under the following conditions: 2, 4, and 6 min at 241.3, 275.8, and 344.7 MPa pressure and temperatures of 29.4 to 35, 37.8 to 43.3, and 46.1 to 51.7 degrees C. Reductions of 7.8 log PFU (100% inactivation) were achieved for freely suspended T7 at 344.7 MPa for 2 min at 37.8 to 43.3 degrees C. At 46.1 to 51.7 degrees C, T7 associated with either clams or oysters was inactivated at nearly 100% (>4 log PFU) at all pressure levels and durations tested. These results indicate that T7 is readily inactivated by HPP under the proper conditions, may be made more susceptible to HPP by mixing with shellfish meat, and may serve as a viable model for the response of several animal viruses to HPP.