Rapid Settling Rate Research Articles

Persistence of E. coli in Streambed Sediment Contaminated with Faeces from Dairy Cows, Geese, and Deer: Legacy Risks to Environment and Health.

Legacy stores of faecal pollution in streambed sediments can result in delayed impacts on environmental quality and human health if resuspended into the overlying water column. Different catchment sources of faecal pollution can contribute to a legacy store of microbial pollutants, with size of stores influenced by microbial die-off and faecal accrual rates in the streambed. The aim of this study was to use a mesocosm experiment to characterise the persistence of E. coli derived from faeces of dairy cows, deer, and geese once introduced to streambed sediment under different temperature regimes. The settling rate of solid constituents of faecal material into streambed sediment once delivered into an aquatic environment was also quantified. The persistence patterns of E. coli in streambed sediment were found to vary as a function of faecal source and temperature; die-off of E. coli in sediment contaminated with goose faeces was more rapid than in sediments contaminated with dairy cow or deer faeces. Goose faeces also recorded a more rapid settling rate of faecal particles through the water column relative to dairy cow and deer faeces, suggesting a more efficient delivery of E. coli to streambed sediments associated with this faecal source. Our findings provide new evidence to improve understanding of the potential longer-term risks to both the environment and public health posed by sediments when contaminated with livestock, wildlife, and wildfowl faeces.

The removal of Cu(II)–EDTA chelates using green rust adsorption combined with ferrite formation process

Classical adsorbents such as activated carbon are inefficient to remove Cu(II)-EDTA in solution. Moreover, the heavy metals in the generated sludge can easily be dissolved back into solution. In this research, a novel strategy developed by coupling green rust adsorption and ferrite formation technology was proposed for Cu(II)-EDTA chelate removal. At the adsorption stage, green rust sulfate (GRME(SO42−)) showed a high adsorption efficiency of chelated copper, with a capacity of 126.41 mg g−1, compared to other classical adsorbents. During the ferrite formation stage, GRME(SO42−)-based precipitate with high moisture content and slow settling rate could be transformed into ferrite-based precipitate with low moisture content and rapid settling rate. The volume and moisture content of ferrite were 2.20 and 1.45 times lower than those of GRME(SO42−) and the sedimentation velocity of ferrite was also 1.23 times higher than that of GRME(SO42−), which strongly demonstrated the necessity of the ferrite formation process. Toxicity characteristic leaching procedure (TCLP) test results showed that the metallic copper of GRME(SO42−) sludge could be more easily dissolved back into solution than that of ferrite precipitate under weak-acid conditions, indicating the stability of ferrite. In addition, after the ferrite process, the generated sludge exhibited soft magnetism and could be quickly separated within few seconds using an external magnetic field. All these results showed that the combined green rust adsorption with ferrite formation method was an efficient, recyclable and eco-friendly method for the treatment of wastewater containing Cu(II)-EDTA.

Freshwater diatoms as a source of lipids for biofuels

Until recently, biodiesel production has been derived from terrestrial plants such as soybean and canola, leading to competition between biodiesel production and agricultural production for source materials. Microalgae have the potential to synthesize 30 times more oil per hectare than terrestrial plants without competing for agricultural land. We examined four genera (Cyclotella, Aulacoseira, Fragilaria, Synedra) of common freshwater diatoms (Bacillariophyceae) for growth and lipid content in defined medium (sD11) that replicates hypereutrophic conditions in lakes and wastewater treatment plant effluents and optimized the medium for silicon content. Cyclotella and Aulacoseira produced the highest levels of total lipids, 60 and 43μg total lipids/ml, respectively. Both diatoms are rich in fatty acids C14, C16, C16:1, C16:2,7,10, and C22:5n3. Of the diatoms examined, Cyclotella reached the highest population density (>2.5×10(6) cells/ml) in stationary phase when many of the cells appeared to be filled entirely with oil. Silicon enrichment studies indicated that for optimal utilization of phosphorus and nitrogen by diatoms growing in wastewater effluent, the amount of silicon present or added to the effluent should be 17.5 times the mass of phosphorus in the effluent. With high growth rates, high lipid contents, and rapid settling rates, Cyclotella and Aulacoseira are candidates for biodiesel production.

Flocculation Kinetics of TiO2-enzyme Microfloccules

TiO2-enzyme microfloccules were prepared by using titanium dioxide nanoparticles as immobilizing carriers, three kinds of polyacrylamide (nonionic, cationic and anionic polyacrylamide) as flocculants and papain as a model of en- zyme. The effects of pH values, dosage and types of polyacrylamide (PAM) on the flocculation and sedimentation behaviour of TiO2-enzyme microfloccules were investigated. The SEM, EDS and particle size analyzer were used to characterize the morphology of TiO2-enzyme microfloccules. The results showed that an effective flocculation was formed among TiO2, pa- pain and different types of PAM flocculant by hydrogen bonding interactions, electrostatic attractions, adsorption bridging action, etc. It was noted that the settling rate of TiO2-enzyme microfloccules, turbidity of the supernatant, floc size and com- pactness of resulting floccules were highly dependent on the PAM dosage. For three kinds of PAM, similar trends of floccu- lation kinetics were observed, a general increase in settling rates were relevant to decrease in turbidity. Attributed to high settling rates, strong flocculation with big size and stable floc occurred with the function of optimum PAM concentrations. But the optimum dosages were different. When the concentration was in the range of 75 mgL -1 to 175 mgL -1 , nonionic PAM (nPAM) displayed the best flocculant performance in all kinds of PAM with a rapid settling rate and large floc size. Moreover, under excessive dosage condition, breakup of floc then occurred. Flocculation kinetics of TiO2-enzyme micro- floccules also could be effectively controlled by changing the pH value of reaction system. Compared nPAM with cationic PAM (cPAM), the microfloccules by using nPAM displayed a high stability and compactness in a wide range of pH values. The settling rate and floc size by using cPAM showed a strong dependence on pH values. It indicated that the immobilized enzyme size could be regulated by the PAM dosage and pH value according to the enzyme structure and properties. Such porous and flexible microstructure was expected to provide the free space as much as possible for the access of substrate molecules to enzyme. Keywords flocculation kinetics; settling rate; particle size distribution; nano TiO2; morphology

Sulphur dioxide as a volcanic ash proxy during the April–May 2010 eruption of Eyjafjallajökull Volcano, Iceland

Abstract. The volcanic ash cloud from the eruption of Eyjafjallajökull volcano in April and May 2010 resulted in unprecedented disruption to air traffic in Western Europe causing significant financial losses and highlighting the importance of efficient volcanic cloud monitoring. The feasibility of using SO2 as a tracer for the ash released during the eruption is investigated here through comparison of ash retrievals from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) with SO2 measurements from a number of infrared and ultraviolet satellite-based sensors. Results demonstrate that the eruption can be divided into an initial ash-rich phase, a lower intensity middle phase and a final phase where considerably greater quantities both ash and SO2 were released. Comparisons of ash-SO2 dispersion indicate that despite frequent collocation of the two species, there are a number of instances throughout the eruption where separation is observed. This separation occurs vertically due to the more rapid settling rate of ash compared to SO2, horizontally through wind shear and temporally through volcanological controls on eruption style. The potential for the two species to be dispersed independently has consequences in terms of aircraft hazard mitigation and highlights the importance of monitoring both species concurrently.

Environmental Controls on Coastal Coarse Aerosols: Implications for Microbial Content and Deposition in the Near-Shore Environment

Coarse aerosols (particle diameter (D(p)) > 2 μm) produced in coastal surf zones carry chemical and microbial content to shore, forming a connection between oceanic, atmospheric, and terrestrial systems that is potentially relevant to coastal ecology and human health. In this context, the effects of tidal height, wind speed, and fog on coastal coarse aerosols and microbial content were quantified on the southern coast of Maine, USA. Aerosols at this site displayed clear marine influence and had high concentrations of ecologically relevant nutrients. Coarse aerosol concentrations significantly increased with tidal height (i.e., decreasing distance from waterline), onshore wind speed, and fog presence. As onshore wind speeds rose above 3 m s(-1), the mean half-deposition distance of coarse aerosols increased to an observed maximum of 47.6 ± 10.9 m from the water's edge at wind speeds from 5.5-8 m s(-1). Tidal height and fog presence did not significantly influence total microbial aerosol concentrations but did have a significant effect on culturable microbial aerosol fallout. At low wind speeds, culturable microbial aerosols falling out near-shore decreased by half at a distance of only 1.7 ± 0.4 m from the water's edge, indicating that these microbes may be associated with large coarse aerosols with rapid settling rates.

Adsorption and flocculation behaviors of polydiallyldimethylammonium (PDADMA) salts: Influence of counterion

Two modified polymer flocculants of PDADMA salts, PDADMA nitrate (PDADMAN) and PDADMA sulfate (PDADMAS), were prepared from the most widely used commercial product of polydiallyldimethylammonium chloride (PDADMAC). Solution properties such as conductivity and viscosity were investigated, showing that the conductivity follows the order of PDADMAS > PDADMAC > PDADMAN, while the reduced viscosity increases in the order of PDADMAS < PDADMAC < PDADMAN. The results indicate that, compared with PDADMAC, PDADMAN has a more cationic density and a more extended polymer chain, whereas PDADMAS exhibits a smaller coiled polymer size because of the stronger charge affinity of sulfate ion to the polycation of PDADMA. Flocculation experiments were performed on kaolin suspensions. It was found that PDADMAN is the most efficient in turbidity removal, while PDADMAS has wider optimum dosages, larger floc size and more rapid settling rate. Atomic force microscopy (AFM) was employed for imaging the adsorption structures of the three polymers on the negatively charged mica surface. Remarkable differences in molecular conformation were observed. Compared with the pearl necklace-like aggregation of hemispheroids of PDADMAC polymer, PDADMAN takes a sponge-like thin layer structure and PDADMAS exhibits a uniform hemispherical structure. The above differences in both the solution property and the adsorption and flocculation behaviors are attributable to counterion effects. Different counterions may lead to different adsorption and flocculation mechanisms that PDADMAN adopts a flat and layer–layer adsorption without loops and tails extended from the surface, implying that a charge neutralization mechanism plays more roles, while adsorbed PDADMAS is in the form of coiled spheres with loops and tails so that a bridging mechanism is more involved. Namely, it is the adsorption structure and morphology of the polymer flocculants that is the main factor influencing the flocculation mechanism.

The Use of Inkjet to Create Direct Write Conductive Features

The process of inkjet dispensing metal particulate dispersions to obtain conductive features is an intriguing prospect and reflects an interesting dichotomy for inkjet technology. The ink must be reliable to the extreme, whilst at the same time, contain the maximum possible solids loading of metal particles to create high conductivity, typically less than 10 milliohms per square. It is not straightforward to jet metal dispersions as most conductive materials have densities of up to10g/cm, leading to rapid settling rates in low viscosity fluids for anything other than nano-sized particles. In addition, such high densities create problems in depositing sufficient active materials. For example, an ink with a 35% w/w solids loading ink can contain only 3.5% of active material by volume, significantly reducing the ability to deposit thick metallic layers. Finally, in order to achieve high inkjet reliability and conductivity, the metal particles require a highly effective dispersant which needs to be volatilised during a post heating treatment process.In contrast, this paper describes an alternative novel approach to allow the direct inkjet dispensing of a range of metals onto non porous materials. The technology uses UV cure based inks and relies on creating a cured &#x201C;honeycomb&#x201D; open structure and depositing metal in bulk around strands of a three dimensional UV polymeric network. The process is flexible and capable of being used in many different industrial configurations, including as an inline high speed digital web. This approach achieves high inkjet reliability, high conductivity and the flexibility of tuning a wide range of metal layer and line thicknesses without the need for any post treatment process. Examples of the use of inkjet to create a range of metal tracks using both piezo and thermal inkjet printheads will be presented. The electronic functional performance and properties will be illustrated using a range of different key features such as printing directly to chips or components, printing small features down to less than ten microns and creating highly conductive tracks.

EVALUATION OF SLUDGE PRODUCED BY LIMESTONE NEUTRALIZATION OF AMD AT THE FRIENDSHIP HILL NATIONAL HISTORIC SITE

A pulsed limestone bed (PLB) treatment plant for remediation of acid mine drainage (AMD) has been tested at the Friendship Hill National Historic site in southwestern Pennsylvania. The plant performed well, neutralizing over 50 metric tons of acidity over a 14-month period, but the cost of disposal of the 450 metric tons of sludge generated was high, because the sludge was hauled from the site and disposed of in a commercial landfill to minimize the impact on park property. Although the sludge was found to be non-hazardous based on the Toxicity Characteristics Leaching Protocol (TCLP), hauling and disposal costs were still elevated, at $40 per m 3 . Since sludge handling and disposal was a significant fraction of the operating cost of the facility, a study of the sludge characteristics and possible alternate handling methods was undertaken. Samples of AMD influent, treated water and settled sludge were used in a series of small- scale treatment studies. These tests showed that the sludge volume produced by limestone neutralization was less than half of that for lime, sodium hydroxide or ammonia. The settling rate was also greater for the limestone-based sludge. Vacuum filtration tests demonstrated that the limestone sludge was more readily filtered than sludges generated with sodium hydroxide or lime and that solids contents of up to 28% could be achieved. Because of lower maintenance costs, pressure filtration using a plate and frame filter is recommended for future plant operations. In this case, solids contents of as high as 31% were realized. As an alternative to the operating costs of mechanical filtration, a settling/percolation process was tested. Percolation tests showed that solids content of the settled sludge could be increased from 8% to 25%. These results show that sludge disposal costs for the treatment plant could be decreased through installation of a settling or filtration process. Moreover, the PLB process offers saving not only in reagent costs, but also in sludge disposal costs, through decreased sludge volume generated, rapid settling rates and ready filterability.

Particulate Organic Carbon Export Fluxes in The Canada Basin and Bering Sea as Derived from 234Th/238U Disequilibria

Seawater samples were collected in the water column of the Canada Basin and the Bering Sea from aboard the R/V Xue Long during August 1999. Activity concentrations of dissolved and particulate 234Th were measured using beta counting techniques to quantify the scavenging and residence time of 234Th and organic carbon export fluxes. Primary production (PP) and bacterial production were also determined in the study areas through in situ incubation experiments. Significant 234Th scavenging was observed in the upper 100 m of the water column in both study areas, with up to 40% of 234Th deficit found at Bering Sea stations and ~15% of 234Th deficit at the Canada Basin station. Measured PP decreased from ~12.5 µmol C/m³/h in surface water to near zero at ~100 m depth, with an integrated PP of 3.83 mmol C/m²/d in the Canada Basin. Bacterial production, on the other hand, was on the order of 2.0 mmol C/m²/d, which is up to 52% of the integrated PP. Particulate organic carbon (POC) export fluxes derived from 234Th/238U disequilibrium were ~1 mmol C/m²/d in the Canada Basin and ~10 mmol C/m²/d in the Bering Sea, with fluxes in the latter area being 5 to 10 times higher than those found in the Canada Basin. These export fluxes correspond to a ThE ratio (the ratio of 234Th-derived POC export to primary production) of 0.26 for the Canada Basin and 0.7 for the Bering Sea. The higher ThE ratios in the study areas suggest a decoupling of production and particulate export in the high-latitude ocean. Ratios of POC to particulate 234Th (µmol C/dpm) decreased consistently with increasing depth, suggesting that organic carbon is preferentially remineralized relative to 234Th. Interestingly, the profile of particulate 234Th in the Canada Basin showed a unique characteristic: particulate 234Th activities increased with increasing depth, suggesting a continuous scavenging of 234Th and a rapid settling rate of the particles.

Coccolithophorids on the continental slope of the Bay of Biscay – production, transport and contribution to mass fluxes

Coccoliths collected by sediment traps deployed on the slope of the Bay of Biscay (northeastern Atlantic), from June 1990 to August 1991, were examined to determine their contribution to the transport of carbonate on a mid-latitude continental margin. They also were used as tracers of particle transfer processes on this slope. Two traps located at 1900 m, respectively at 2300 (Mooring Site 1) and 3000 m (Mooring Site 2) water depths provided high-resolution (4–7 days) time-series samples covering a 14-month period at MS2 and a 3-month period at MS1. Coccoliths from 28 species were identified over the course of the experiment, among which Emiliania huxleyi was always dominant (relative abundance range: 59–93%). Total coccoliths number fluxes were high but variable, ranging from 390×10 6 to 1610×10 6 coccoliths m −2 day −1 at MS1, and from 58×10 6 to 1500×10 6 coccoliths m −2 day −1 at MS2. The time-weighted mean flux, calculated for the whole experiment at MS2, was 499×10 6 coccoliths m −2 day −1. Estimate of coccoliths minimal contribution to total carbonate flux at 1900 m depth averaged 12%, which represented a weighted mean flux of 7.3 mg m −2 day −1 (2.7 g m −2 yr −1). Lateral transport of coccoliths resuspended from shelf and/or upper slope sediments seems to be the dominant transfer process to depth on this northeastern Atlantic slope. Nevertheless, the clear seasonal succession observed in the species composition implies that the deposition/resuspension/transport sequence is rapid (presumably less than a few months). Several short and unsmoothed signals directly issued from coccoliths bloom events also were recorded in our traps, a result that indicates rapid settling rates. The overall coccolith sedimentation processes appear as being quite diversified, but quantitative and qualitative analyses of aggregates collected by the traps suggest that they are important carriers of coccoliths in this margin environment.

Diatom fluxes to the deep sea in the oligotrophic North Pacific gyre at Station ALOHA

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 182:55-67 (1999) - doi:10.3354/meps182055 Diatom fluxes to the deep sea in the oligotrophic North Pacific gyre at Station ALOHA Renate Scharek*, Luis M. Tupas, David M. Karl Department of Oceanography, School of Ocean and Earth Science and Technology, University of Hawaii, Honolulu, Hawaii 96822, USA *Present address: Institut de Ciències del Mar, Passeig Joan de Borbó s/n, E-08039 Barcelona, Spain. E-mail: rscharek@cucafera.icm.csic.es ABSTRACT: Planktonic diatoms are important agents of vertical transport of photosynthetically fixed organic carbon to the ocean's interior and seafloor. Diatom fluxes to the deep sea were studied for 2 yr using bottom-moored sequencing sediment traps located in the vicinity of the Hawaii Ocean Time-series (HOT) program station 'ALOHA' (22°45'N, 158°W). The average flux of empty diatom frustules was around 2.8 x 105 cells m-2 d-1 in both years, except in late summer when it increased approximately 30-fold. Flux of cytoplasm-containing diatom cells was much lower (about 8 x 103 cells m-2 d-1) but increased 500-fold in late July 1992 and 1250-fold in August 1994. Mastogloia woodiana Taylor, Hemiaulus hauckii Grunow and Rhizosolenia cf. clevei var. communis Sundström were the dominant diatom species observed during the July 1992 event, with the former 2 species again dominant in August 1994. The 1994 summer flux event occurred about 3 wk after a documented bloom of H. hauckii and M. woodiana in the mixed-layer and a simultaneous increase in vertical flux of these species. This surface flux signal was clearly detectable at 4000 m, suggesting rapid settling rates. A further indication of very high sinking speeds of the diatoms was the much larger proportion of cytoplasm-containing cells in the bottom-moored traps during the 2 summer events. Cells of H. hauckii and R. cf. clevei var. communis frequently contained endosymbiotic cyanobacteria with heterocysts (cf. Richelia), similar to the cells of these species in the mixed-layer. Our data show for the first time that diatoms containing nitrogen-fixing cyanobacteria contribute directly to the vertical flux of organic matter to the deep sea in the oligotrophic regions. The peak of diatom flux coincided with a significant flux increase of biogenic silica in both years. During periods of rapid sinking, the vertical flux of diatom assemblages out of the uppermost water column seems to be more important than the diatom flux out of the deep chlorophyll maximum layer (DCML). Aggregate formation may be responsible for the fast sinking of the diatoms. KEY WORDS: Biogenic silica · Bottom-moored sediment traps · Deep sea · Diatoms · Vertical particle flux Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 182. Publication date: June 11, 1999 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1999 Inter-Research.

Feast/famine growth environments and activated sludge population selection

The effect of feast/famine growth conditions on activated sludge cultures indicates that nonfilamentous cultures can be selected by providing proper substrate gradients and extended periods of endogenous metablism. Reactor operating strategies providing intermittently high substrate concentrations result in cultures characterized by high peak substrate and oxygen uptake activities, rapid settling rates, and high resistance to starvation. Sludge settleability can be manipulated using controlled variations in growth environment with corresponding changes noted in sludge activity. In combination with the low net growth rates associated with activated sludge systems, feast/famine environments would logically convey a selection advantage to microbes capable of readily assimilating substrate materials and maintaining viability during extended starvation periods.

Dispersion and Deposition of Corn Pollen from Experimental Sources1

AbstractThe atmospheric dispersion and subsequent deposition of corn (Zea mays L.) pollen emitted from plants in two 18‐m diameter plots were studied in 39 tests at Brookhaven National Laboratory to compare the spread of this large pollen to that of smaller pollens studied previously. Concentrations were measured by wind‐impaction samplers mounted at four heights (0.5 to 4.6 m) and at five distances from the source on 20‐degree radii. Deposition was measured by greased microscope slides on the ground.Data were analyzed in terms of current meteorological dispersion theory. Normalized centerline concentrations, crosswind integrated concentrations, plume widths and heights, and mass flux are presented as functions of distance and compared to similar data from ragweed (Ambrosia) and timothy (Phleum pratense) sources of comparable size. Normalized centerline and crosswind integrated deposition and velocity of deposition are also presented as functions of distance and are compared to ragweed and timothy pollen data. The study shows that corn pollen is not transported as far by the wind as smaller pollens, does not disperse as widely in either the horizontal or the vertical direction and settles to earth more quickly, much of it within the source itself.The dispersion of corn pollen is influenced by its large size and rapid settling rate. At 60 m from the source in the downwind direction, concentrations average about 1% of those at 1 m. Width of the pollen plume at 60 m is less than that of smaller pollens under similar conditions. The rate of settling opposes the rate of upward dispersion so that the height of the pollen plume does not increase continuously with downwind distance. At 60 m from the source concentrations integrated in the crosswind direction average from 3 to 6% of those at 1 m. The total amount of pollen remaining airborne at 60 m is 5% of that at 1 m.Total deposition within the source plot is greater than that outside. Deposition per unit area at 60 m downwind is only 0.2% of that near the source. Crosswind integrated deposition at 60 m varies from 0.5 to 0.8% of that at 1 m. The velocity of deposition at 32 m from the source averages about 33 cm/sec.