Flume Water Research Articles

Benthic buffers and boosters of ocean acidification on coral reefs

Abstract. Ocean acidification is a threat to marine ecosystems globally. In shallow-water systems, however, ocean acidification can be masked by benthic carbon fluxes, depending on community composition, seawater residence time, and the magnitude and balance of net community production (NCP) and calcification (NCC). Here, we examine how six benthic groups from a coral reef environment on Heron Reef (Great Barrier Reef, Australia) contribute to changes in the seawater aragonite saturation state (Ωa). Results of flume studies using intact reef habitats (1.2 m by 0.4 m), showed a hierarchy of responses across groups, depending on CO2 level, time of day and water flow. At low CO2 (350–450 μatm), macroalgae (Chnoospora implexa), turfs and sand elevated Ωa of the flume water by around 0.10 to 1.20 h−1 – normalised to contributions from 1 m2 of benthos to a 1 m deep water column. The rate of Ωa increase in these groups was doubled under acidification (560–700 μatm) and high flow (35 compared to 8 cm s−1). In contrast, branching corals (Acropora aspera) increased Ωa by 0.25 h−1 at ambient CO2 (350–450 μatm) during the day, but reduced Ωa under acidification and high flow. Nighttime changes in Ωa by corals were highly negative (0.6–0.8 h−1) and exacerbated by acidification. Calcifying macroalgae (Halimeda spp.) raised Ωa by day (by around 0.13 h−1), but lowered Ωa by a similar or higher amount at night. Analyses of carbon flux contributions from benthic communities with four different compositions to the reef water carbon chemistry across Heron Reef flat and lagoon indicated that the net lowering of Ωa by coral-dominated areas can to some extent be countered by long water-residence times in neighbouring areas dominated by turfs, macroalgae and carbonate sand.

Contamination of pear concentrate by Alicyclobacillus from recirculating flume water during fruit concentrate production

Alicyclobacillus and viable aerobic counts were monitored at nine different production stages of pear concentrate, with the functioning of either a recirculating or a one-pass flume water system. Significantly (P 0.05) in condensate water during the functioning of the two flume water systems, with 1.81 Log10 c.f.u. ml−1 vegetative cells and 1.01 Log10 c.f.u. ml−1 endospores (recirculating system) and 0.78 Log10 c.f.u. ml−1 vegetative cells and 0.42 Log10 c.f.u. ml−1 endospores (one-pass system) recovered, respectively. As a result, water treatment protocols should be established if untreated recirculating flume or condensate water is to be used in order to prevent Alicyclobacillus contamination and accumulation in the processing environment.

Six Years of Ozone Processing of Fresh Cut Salad Mixes

Strickland Produce Inc., Nashville, TN, packages fresh cut salads in bags for the ready-to-eat market. Produce is sorted, cut, washed, packed in plastic bags and distributed under refrigeration. Flume water washes and transports products through the plant, and is recycled in a closed loop. Ozone was installed full-scale in 2000 for flume water treatment (200 gpm) and has provided significant improvement in plant product qualities plus savings in water, labor, and plant effluent costs for the past six years. With chlorine treatment alone, the flume water quickly became discolored, laden with organic residues, and needed to be replaced every 2–3 hours. With the ozone treatment, flume water is replaced once daily, allowing for at least a 60% flume water savings. Of even more significance are the labor savings resulting from less frequent changing of spent flume water. Costs for ozonation equipment were recovered in less than two years.

Nitrogen Fate in Drainage Ditches of the Coastal Plain after Dredging

Drainage ditches are a key conduit of nitrogen (N) from agricultural fields to surface water. The effect of ditch dredging, a common practice to improve drainage, on the fate of N in ditch effluent is not well understood. This study evaluated the effect of dredging on N transport in drainage ditches of the Delmarva Peninsula. Sediments from two ditches draining a single field were collected (0-5 cm) to represent conditions before and after dredging. Sediments were packed in 10-m-long recirculating flumes and subjected to a three-phase experiment to assess the sediment's role as a sink or source of ammonium (NH4) and nitrate (NO3). Under conditions of low initial NH4-N and NO3-N concentrations in flume water, sediment from the undredged ditch released 113 times more NO3-N to water than did sediment from the dredged ditch. When flume water was spiked with NH4-N and NO3-N to simulate increases in N concentrations from drainage and runoff from adjacent fields, NO3-N in flume water increased during 48 h compared with the initial spiked concentration, while NH4-N decreased. These simultaneous changes were attributed to nitrification, with 23% more NO3-N observed in flume water with undredged ditch sediment compared with dredged ditch sediment. Replacing the N-spiked water with deionized water resulted in two times more NO3-N released from the undredged ditch sediment than the dredged ditch sediment. These results suggest that ditch sediments could represent significant stores of N and that dredging could greatly affect the ditch sediment's ability to temporarily assimilate N input from field drainage.

Flume Water Transport of Screenings Improves Headworks Operations

Flume Water Transport of Screenings Improves Headworks Operations

Impact of Dredging on Phosphorus Transport in Agricultural Drainage Ditches of the Atlantic Coastal Plain1

Abstract: Drainage ditches can be a key conduit of phosphorus (P) between agricultural soils of the Atlantic Coastal Plain and local surface waters, including the Chesapeake Bay. This study sought to quantify the effect of a common ditch management practice, sediment dredging, on fate of P in drainage ditches. Sediments from two drainage ditches that had been monitored for seven years and had similar characteristics (flow, P loadings, sediment properties) were sampled (0‐5 cm) after one of the ditches had been dredged, which removed fine textured sediments (clay = 41%) with high organic matter content (85 g/kg) and exposed coarse textured sediments (clay = 15%) with low organic matter content (2.2 g/kg). Sediments were subjected to a three‐phase experiment (equilibrium, uptake, and release) in recirculating 10‐m‐long, 0.2‐m‐wide, and 5‐cm‐deep flumes to evaluate their role as sources and sinks of P. Under conditions of low initial P concentrations in flume water, sediments from the dredged ditch released 13 times less P to the water than did sediments from the ditch that had not been dredged, equivalent to 24 mg dissolved P. However, the sediments from the dredged ditch removed 19% less P (76 mg) from the flume water when it was spiked with dissolved P to approximate long‐term runoff concentrations. Irradiation of sediments to destroy microorganisms revealed that biological processes accounted for up to 30% of P uptake in the coarse textured sediments of the dredged ditch and 18% in the fine textured sediments of the undredged ditch. Results indicate that dredging of coastal plain drainage ditches can potentially impact the P buffering capacity of ditches draining agricultural soils with a high potential for P runoff.

Efficacy of FIT Produce Wash and Chlorine Dioxide on Pathogen Control in Fresh Potatoes

A commercial fresh pack potato operation was used as a model to evaluate FIT fruit and vegetable wash effectiveness in reducing levels of microorganisms on potatoes and in flume water. Fresh potatoes were washed in flume water with or without FIT, or treated with a spray bar utilizing either FIT, 9 ppm chlorine dioxide (CIO2), or a water control. Both flume treatments were also evaluated for APC and Gram-negatives. There were no significant differences in reduction of these microorganisms on treated or control potatoes. However, levels of Gram-negative bacteria in FIT-amended flume water were reduced by 5.95 log CFU/g, and the APC was reduced by 1.43 log CFU/g. To validate plant trial findings, this test was repeated using solutions of sterile potato flume water from the fresh pack operation, containing a typical level of dissolved and suspended solids. Treatment solutions prepared with flume water or deionized water containing FIT, 9 ppm CIO2, or a water control were inoculated with E. coli O157:H7, Salmonella Typhimurium, or Pectobacterium carotovorumssp. carotovorum. FIT and ClO2 prepared with deionized water reduced levels of microorganisms by >6.1 to 6.6 log CFU/g to below the detection limit. FIT prepared with flume water reduced levels of all organisms by >6.0 to 6.4 log CFU/g to below the detection limit, whereas ClO2 prepared from flume water reduced bacterial levels of all organisms by only 0.7 to 1.4 log CFU/g. Neither FIT nor ClO2 was particularly efficacious against E. coli O157:H7, S. Typhimurium, APC, yeasts, or molds on potato surfaces.

Local scouring due to turbulent water jets downstream of a trapezoidal drop: Laboratory experiments and stability analysis

Three series of laboratory experiments were run, varying the flume water discharge and the downstream water depth, to investigate local scouring downstream of a trapezoidal drop followed by a rigid apron. Three different kinds of jets, developing downstream of the drop, were observed: a submerged jet, a surface wave jet, and an oscillating jet. The oscillating jet is defined as a jet which changes intermittently between a surface wave jet and a submerged jet. A different development of the scouring process due to the different kinds of jet was observed: a submerged jet produced a local scouring with a downstream dune, while a surface wave jet produced a local scouring with both an upstream and a downstream dune; the scouring process due to the oscillating jet was the result of the interaction of the scouring processes due to a submerged jet and a surface wave jet. A stability analysis of the surface wave jet was performed, with both a flat and a scoured bed, by means of the modified De Saint–Venant equations, that is, with correction terms accounting for the curvature of the streamlines. The stability of the surface wave jet is affected by the presence of the scoured bed, which weakens its stability properties.

Chlorine Disinfection of Tomato Surface Wounds Contaminated with Salmonella spp.

This study examined the efficacy of chlorine treatments of flume water for eliminating Salmonella spp. from inoculated wounds and intact surfaces of tomatoes (Lycopersicon esculentum). Water in a scale-model flume was chlorinated to 150 mg·L-1 of free chlorine at pH 6.5 and maintained at a temperature of 25 or 35 °C, depending on the test. Viable Salmonella were recovered from all of the inoculation sites (intact fruit surface, punctures, shaves, and stem scars) even after treatment with chlorinated water for up to 120 seconds at either 25 or 35 °C. Generally, the highest Salmonella recovery came from puncture wounds and the lowest from the intact surfaces. After 120 seconds at 25 °C, 4.9 to 5.8 log10 units were recovered from the wounds. Populations recovered after the 30-second treatment at 35 °C ranged from 4.1 log10 cfu/mL for intact surfaces to 6.0 log10 cfu/mL in the puncture wounds. At 60- and 120-second treatment times, all wounds had higher mean populations than tomatoes with intact surfaces. Although greater Salmonella survival was associated with shorter exposure to the chlorine, water chlorination cannot completely eliminate contamination of tomato fruit by Salmonella, even on intact surfaces. Stem scars, in this study, were not readily disinfected with sodium hypochlorite.

Grazer–collector facilitation hypothesis supported by laboratory but not field experiments

Grazing invertebrates in streams feed by harvesting algal cells from surfaces, and in doing so release fine particulate organic matter (FPOM). The "grazer–collector facilitation hypothesis" holds that FPOM production by grazers facilitates growth and (or) survival of FPOM-collecting invertebrates. We tested for grazer–collector facilitation in laboratory and field experiments. In recirculating flumes in the laboratory, we tested for facilitation of the collector Hydropsyche slossonae by the grazers Physa gyrina, Glossosoma intermedium, and Baetis tricaudatus. All three grazers increased FPOM levels in flume water, but only Physa facilitated Hydropsyche growth. In the field, we manipulated Physa and Glossosoma densities to test for facilitation (at a local scale) of natural collector assemblages in an eastern Iowa stream. We did not detect facilitation of any collector by either grazer in the field, despite high power to detect such interactions. We suspect that grazer–collector facilitation was not observed in the field because (unlike in our laboratory flumes) field FPOM levels are often high and extremely variable in time and space and because organic particles can arise from sources other than grazer activity (= grazer-independent processing). Therefore, at local scales, collectors may not be significantly limited by the supply of grazer-derived FPOM.

Sources of Salmonella on broiler carcasses during transportation and processing: modes of contamination and methods of control.

The prevalence and types of salmonella in broiler chickens during transportation and during slaughter and dressing were studied. This was part of a comprehensive investigation of salmonellas in two UK poultry companies, which aimed to find the origins and mechanisms of salmonella contamination. Salmonellas were isolated using cultural methods. Serovars of Salmonella detected during rearing were usually also found in a small proportion of birds on the day of slaughter and on the carcasses at various points during processing. There was little evidence of salmonellas spreading to large numbers of carcasses during processing. Many serovars found in the feedmills or hatcheries were also detected in the birds during rearing and/or slaughter. Transport crates were contaminated with salmonellas after washing and disinfection. Prevalence of salmonellas fell in the two companies during this survey. A small number of serovars predominated in the processing plants of each company. These serovars originated from the feed mills. Reasons for transport crate contamination were: (1) inadequate cleaning, resulting in residual faecal soiling; (2) disinfectant concentration and temperature of disinfectant too low; (3) contaminated recycled flume water used to soak the crates. Efforts to control salmonella infection in broilers need to concentrate on crate cleaning and disinfection and hygiene in the feed mills.

Ecology of Thioploca spp.: nitrate and sulfur storage in relation to chemical microgradients and influence of Thioploca spp. on the sedimentary nitrogen cycle.

Microsensors, including a recently developed NO3(-) biosensor, were applied to measure O(2) and NO3(-) profiles in marine sediments from the upwelling area off central Chile and to investigate the influence of Thioploca spp. on the sedimentary nitrogen metabolism. The studies were performed in undisturbed sediment cores incubated in a small laboratory flume to simulate the environmental conditions of low O(2), high NO3(-), and bottom water current. On addition of NO3(-) and NO2(-), Thioploca spp. exhibited positive chemotaxis and stretched out of the sediment into the flume water. In a core densely populated with Thioploca, the penetration depth of NO3(-) was only 0.5 mm and a sharp maximum of NO3(-) uptake was observed 0.5 mm above the sediment surface. In sediments with only few Thioploca spp., NO3(-) was detectable down to a depth of 2 mm and the maximum consumption rates were observed within the sediment. No chemotaxis toward nitrous oxide (N2O) was observed, which is consistent with the observation that Thioploca does not denitrify but reduces intracellular NO3(-) to NH(4)(+). Measurements of the intracellular NO3(-) and S(0) pools in Thioploca filaments from various depths in the sediment gave insights into possible differences in the migration behavior between the different species. Living filaments containing significant amounts of intracellular NO3(-) were found to a depth of at least 13 cm, providing final proof for the vertical shuttling of Thioploca spp. and nitrate transport into the sediment.

Aeration Performance of Low Drop Weirs

The aeration performance with respect to oxygen transfer of a smooth weir, a cobble-faced weir, and a cobble-faced chute was investigated in a large laboratory flume. The maximum difference between upstream and downstream water surfaces was 0.7 m. A review of existing relationships to predict aeration at weirs indicated that prototype–scale model studies and actual prototype data were limited in this range of drop heights. In addition, most laboratory testing has been conducted at greater drop heights and lower unit discharges. To reduce experimental uncertainty, a procedure was developed which uses an enhanced-oxygen atmosphere over the flume water surface. The uncertainty in values of the deficit ratio (r) developed from the testing procedure is ±0.040. Aeration was greatest with the cobble-faced weir and lowest with the chute. The superior performance of the cobble-faced weir relative to the smooth weir is attributed to weir surface roughness achieved by overlaying the weir crest with cobbles. A new re...

Use of Filtration for Removal of Conidia ofPenicillium expansumfrom Water in Pome Fruit Packinghouses

Removal of conidia of Penicillium expansum from aqueous suspensions with sieves of 2.0 mm to 10 μm and with a triple-stage cartridge filter unit with 5-, 1-, and 0.45-μm terminal filters was studied. The effectiveness of sand filters and cartridge filters for removal of conidia also was evaluated in commercial apple drenchers and packinghouse flumes. The sieves were effective for removal of conidia only when 5-20 mg/ml of soil was added to the suspension, indicating that conidia frequently were bound onto soil particles. In the packinghouse, sand filters did not reduce the concentration of P. expansum in the flume water

Sea Carousel—A benthic, annular flume

A benthic annular flume (Sea Carousel) has been developed and tested to measure in situ the erodibility of cohesive sediments. The flume is equipped with three optical backscatter sensors, a lid rotation switch, and an electromagnetic (EM) flow meter capable of detecting azimuthal and vertical components of flow. Data are logged at rates up to 10·66 Hz. Erodibility is inferred from the rate of change in suspended sediment concentration detected in the annulus. The energy-density/wave number spectrum of azimuthal flow showed peaks in the energy spectrum at paddle rotation wave numbers (k) of 14 and 7 m−1 (macroturbulent time scales) but were not significant. Friction velocity (U*), measured (1) at 1 Hz using a flush-mounted hot-film sensor, and (2) derived from measured velocity profiles in the inner part of the logarithmic layer gave comparable results for Ū* < 0·064 m s−1. At higher values of U*, method (2) underpredicted by up to 20%. Method (1) showed radial increases in Ū* in the annulus for Ūy > 0·32 m s−1. Radial velocity gradients were proportional to (Ūy − 0·32 m s−1). Maximum radial differences in U* were 10% for Ūy = 0·5 ms−1. Suspended sediment mass concentration (S) in the annulus resulted in a significant decrease (10·5%) in Ū* derived by method (1) over the range 0<S<208 mg l−1. These decreases were not evident in method (2). Method (1) may, therefore, be subject to changes in stress sensor calibration with changes in S. Subaerial deployments of Sea Carousel caused severe substrate disturbance, water losses, and aeration of the annulus. Submarine deployments produced stable results, though dispersion of turbid flume water took place. Results clearly demonstrated the existence of ‘Type I’ and ‘Type II’ erosion documented from laboratory studies.

Measurements of sediment transport on the sea bed southwest of England

Sand transport rates were measured via bedload traps that were inserted into the sediment surface on the continental shelf southwest of England. Analysis of the trapped mobile sediment shows this to be finer and better sorted than nearby Shipek grab samples. The transport rates are combined with simultaneous, near-bed flow measurements to assess a Bagnold type predictive equation,j = k1(u2100 -u2100cr)u100. The measured transport rates vary between 0.41 × 10−3 and 1.67 × 10−3 gm/cm s. The data yield a mean calibration coefficient (k1) of 0.4 × 10−6 which is slightly lower than values computed from flume and shallow water data.

Plate roughness and hydrodynamic drag

Previous work on plate roughness and hydrodynamic drag is critically reviewed. Much disagreement is suggested to be due to confusion between definitions and imperfect understanding of the nature of surface roughness. Some common problems of surface roughness measurement, ambiguities and inadequacies of description are discussed. Current experimental measurements of flow and roughness are described for a number of plates coated with ablative paint. Velocity profiles are determined by laser Doppler anemometry in an open flume water channel (20 m in length), while roughness is measured with a computerized stylus instrument. Drag characterization is based on the velocity similarity laws. Results are compared with an existing correlation; fair agreement is found, but some deficiencies of the correlation itself emerge.

The occurrence and survival of coliforms and salmonellas in apple juice and cider.

Apples and juices from large and small cidermakers were examined for the presence of coliform organisms and salmonellas. Coliforms were found both on the fruit and in the juice, and salmonellas were isolated on more than one occasion from the flume water. Experiments showed that salmonellas could survive in apple juice for 30 d at a pH of 3·6.

The Findlay flume and condenser water system

The Findlay flume and condenser water system

The Findlay flume and condenser water system

The Findlay flume and condenser water system