Spelling suggestions: "subject:"low"" "subject:"flow""
141 |
Removal of MS2 Bacteriophage, Cryptosporidium, Giardia and Turbidity by Pilot-Scale Multistage Slow Sand FiltrationDeLoyde, Jeffrey Leo 11 May 2007 (has links)
This research aimed to address the knowledge gaps in the literature regarding the removal of waterborne pathogens (viruses and protozoa) by modified multistage slow sand filtration. In the current study, two pilot-scale multistage slow sand filtration systems were operated continuously for over two years. The pilot systems treated agricultural- and urban-impacted raw river water of variable quality with turbidity peaks over 300 NTU and seasonal cold temperatures <2??C.
The first system (Pilot 1) consisted of two independent trains that included pre-ozonation, shallow-bed upflow gravel roughing filtration, and shallow-bed slow sand filtration. Pilot 1 was a pilot-scale version of an innovative, commercially available full-scale system. The second system (Pilot 2) included a full-depth upflow gravel roughing filter, a full-depth slow sand filter, and a second shallow-depth slow sand filter in series. The SSFs of both pilots were operated at high hydraulic loading rates (typically 0.4 m/h) at the upper limit of the literature recommended range (0.05 to 0.4 m/h).
Both pilot systems provided excellent turbidity removal despite the high filtration rates. Effluent turbidity of all multistage SSF pilot systems were within the regulated effluent limits in Ontario for full-scale SSFs (below 1 NTU at least 95% of the time and never exceeded 3 NTU), despite raw water turbidity peaks over 100 NTU. The roughing filters contributed to approximately 60-80% of the full-train turbidity removal, compared to and 20-40% for the slow sand filters. On average, the second slow sand filter in pilot 2 provided almost no additional turbidity removal. The slow sand filter run lengths were short because of frequent high raw water turbidity, with about 50-80% of the runs in the range of 1-3 weeks. To prevent excessive SSF clogging and maintenance, filtration rates should be decreased during periods of high turbidity.
Seven Cryptosporidium and Giardia challenge tests were conducted on the slow sand filters of both pilot systems at varying filtration rates (0.4 or 0.8 m/h), temperatures (2 to 25??C), and biological maturities (4 to 20 months). Removal of oocysts and cysts were good regardless of sand depth, hydraulic loading rate, and water temperature in the ranges tested. Average removals in the SSFs ranged from 2.6 to >4.4 logs for Cryptosporidium oocysts and ranged from >3.8 to >4.5 logs for Giardia cysts. This was consistent with findings in the literature, where oocyst and cyst removals of >4 logs have been reported. Cryptosporidium oocyst removals improved with increased biological maturity of the slow sand filters. At a water temperature of 2??C, average removal of oocysts and cysts were 3.9 and >4.5 logs, respectively, in a biologically mature SSF. Doubling the filtration rate from 0.4 to 0.8 m/h led to a marginal decrease in oocyst removals. Sand depths in the range tested (37-100 cm) had no major impact on oocyst and cyst removals, likely because they are removed primarily in the upper section of slow sand filter beds by straining. In general, good oocyst and cyst removals can be achieved using shallower slow sand filter bed depths and higher filtration rates than recommended in the literature.
There are very few studies in the literature that quantify virus removal by slow sand filtration, especially at high filtration rates and shallow bed depths. There are no studies that report virus removal by slow sand filtration below 10??C. As such, 16 MS2 bacteriophage challenge tests were conducted at varying water temperatures (<2 to >20??C) and filtration rates (0.1 vs. 0.4 m/h) between February and June 2006 on biologically mature slow sand filters with varying bed depths (40 vs. 90 cm). Biologically mature roughing filters were also seeded with MS2.
Average MS2 removals ranged from 0.2 to 2.2 logs in the SSFs and 0.1 to 0.2 logs in the RFs under all conditions tested. Virus removal by slow sand filtration was strongly dependant on hydraulic loading rate, sand depth, and water temperature. Virus removal was greater at a sand depth of 90 cm vs. 40 cm, at an HLR of 0.1 m/h vs. 0.4 m/h, and at warm (20-24??C) vs. cold (<2-10??C) water temperatures when sufficient warm water acclimation time was provided. Increased sand depth likely increased MS2 removal because of greater detention time for predation and greater contact opportunities for attachment to sand grains and biofilms. A lower HLR would also increase MS2 removal by increasing detention time, in addition to decreasing shear and promoting attachment to filter media and biofilms. Greater MS2 removal at warmer water temperatures was attributed to improved biological activity in the filters. Schmutzdecke scraping was found to have only a minor and short-term effect on MS2 removals.
Virus removal can be optimized by providing deep SSF beds and operating at low filtration rates. Virus removal may be impaired in cold water, which could affect the viability of using SSF/MSF at northern climates if communities do not use disinfection or oxidation. As a stand-alone process, slow sand filtration (with or without roughing filtration) may not provide complete virus removal and should be combined with other treatment processes such as disinfection and oxidation to protect human health.
|
142 |
The Three Pillars of Sustainability : Juxtaposing two Swedish fashion companies and their corporate sustainability conceptsNyfeler, Judith Katharina January 2013 (has links)
The fashion system has increasingly been imbued by ecology and sustainability. While in the recent years a lot on approaches to more sustainable consumption behaviour from the con- sumers’ side have been suggested, this study focuses on the very practice of how sustainabil- ity - in an applied matter - is realised within a fashion company. In this dissertation, two Swe- dish fashion brands, Nudie Jeans co and Filippa K, are being investigated and analysed due to their brand philosophies and concepts dealing with sustainability. If Nudie Jeans co’s first all- organic denim collection launched in Autumn 2012 or Filippa K’s emphasis to the longevity of clothing by classic shapes and plain colours; both ideas foster a slow fashion movement. One of this thesis’ implications is the fact, that the term sustainability is much more far- reaching and expansive as commonly defined. Also timelessness and tradition could be sus- tainable, if still taking care of environment and society. Finally, concepts of sustainability which are commonly not highlighted shall be identified and fill the yet existing gap.
|
143 |
Slow learning children : a situational approach.Emery, Winston G. January 1967 (has links)
No description available.
|
144 |
Characterisation of the sleep-related slow oscillation in the neocortical - entorhinal - hippocampal bidirectional circuitWolansky, Trisha 11 1900 (has links)
Our ability to recall information and events is astounding and dependent on the medial temporal lobe (MTL) memory system. The synaptic interconnections between the neocortex (nCTX), entorhinal cortex (EC), and hippocampus (HPC) are the anatomical basis of this memory system. The electrophysiological basis of memory formation in this system is largely unknown, but the activity patterns that occur during slow wave sleep (SWS) are thought to play an important role. One prominent activity pattern that occurs during SWS is the slow oscillation (SO). It is a large-amplitude rhythm of ~1Hz that was first described in the nCTX and only occurs during SWS and deep anaesthesia. Using the urethane-anaesthetised rat, I provide the first description of the SO in the HPC in Chapter 2. I found that the SO in the HPC was dynamically coordinated with that in the nCTX. Because the EC is the anatomical interface between the nCTX and HPC, I hypothesised that it could be responsible for this coordination. Chapter 3 characterises the SO in the EC and its coordination with both the nCTX and HPC. My results suggested that the synaptic interconnections between the nCTX and HPC via the EC were not solely responsible for SO coordination across these structures. Another possibility is that SO coordination across the nCTX, EC, and HPC occurs via the nucleus reuniens thalami (NReu). In Chapter 4, I delivered trains of electrical stimulation to the frontal cortex (fCTX) to enhance the SO in the nCTX and assess any effect in the HPC. In addition, I delivered the same stimulation trains directly to the medial prefrontal cortex (mpfCTX) and NReu. I found that repeated stimulation in each structure entrained the hippocampal SO. I also found that repeated stimulation of the fCTX and mpfCTX enhanced SO coordination across the nCTX and HPC, but repeated stimulation of the NReu did not. My results suggested that SO coordination across the nCTX and HPC occurs via both the EC and NReu. Understanding the coordination of SO activity across these structures will provide insight to the electrophysiological basis of the MTL memory system and the role of SWS in its function.
|
145 |
"O.K., let's figure it out all together" parents' narratives about their children's literacy learning in the home and school /Semingson, Peggy L., January 1900 (has links)
Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.
|
146 |
Meeting the learning needs of individual children in the mainstream classroom : a dissertation submitted in partial fulfilment of the requirements for the degree of Master of Education in the University of Canterbury /Patterson, Melanie S. January 2008 (has links)
Thesis (M. Ed.)--University of Canterbury, 2008. / Typescript (photocopy). "February 2008." Includes bibliographical references (leaves 91-99). Also available via the World Wide Web.
|
147 |
Characterisation of the sleep-related slow oscillation in the neocortical - entorhinal - hippocampal bidirectional circuitWolansky, Trisha Denise. January 2009 (has links)
Thesis (Ph.D.)--University of Alberta, 2009. / A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosphy, Centre for Neuroscience. Title from pdf file main screen (viewed on November 6, 2009). Includes bibliographical references.
|
148 |
A perceived-risk curriculum for at-risk learners /Kash, Laurel Renee. January 1900 (has links)
Thesis (Ph. D.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 241-266). Also available on the World Wide Web.
|
149 |
Communitas and cohesion on a men's recreational slow pitch softball team in St. John's, Newfoundland and Labrador /Dykstra, Robert John Clarence, January 2004 (has links)
Thesis (M.A.)--Memorial University of Newfoundland, 2004. / Bibliography: leaves 235-248.
|
150 |
Effects of cognitive-based reading strategies in enhancing higher-order comprehension of academically low-achieving students /Ho, Chi-ming, January 2005 (has links)
Thesis (M. Ed.)--University of Hong Kong, 2005.
|
Page generated in 0.0561 seconds