No description available.

No description available.

No description available.

No description available.

The efficiency of colloidal gas aphron (CGA) flotation for separation of algae from growth media was investigated. Anionic, cationic and non-ionic surfactants were used to generate CGAs. Preliminary batch studies showed that two CGA flotation procedures could be successfully used for algae flotation. CGA flotation without pretreatment of algae was only successful using cationic surfactants. All three types of surfactants yielded promising results while combining CGA flotation with alum flocculation as a pretreatment step. Observed removal efficiencies were above ninety percent for batch applications. “Pure CGA flotation” was studied in countercurrent continuous flow operations. Satisfactory removal of algae could be achieved even at substantially reduced volume ratios of CGAs to algae solution. However, TOC concentrations increased with higher volume ratios and higher flowrates due to carryover of CGA bubbles and diffusion of surfactant molecules into the bulk solution. The cationic surfactant Cetyl Pyrimidinium Chloride, present at very low concentrations in the raffinate and the froth algae mixture, exhibited biostatic and biocidal properties in the microbial activity test. / Master of Science / incomplete_metadata

The chemistry of copper sulfate dosing for effective algal kill was investigated in laboratory studies with Selenastrum capricornutum and Microcystis aeruginosa. The goal was to give practical information for water treatment plants operators who often must apply copper sulfate for algae control in impoundments. Research focused on the theoretical relationships involved in copper dosing, with emphasis on the applicability of these relationships to Virginia freshwater. Concentrations of alkalinity and humic acid were varied to study their effect on percentages of ionic copper available. Long-term (2 weeks) growth-rate studies were performed to study the effect of humic acid on the toxicity of ionic copper to algae. Some protection of algae from copper by humic acid was observed. As the humic acid concentration was increased, more ionic copper was complexed and, thus, was unavailable for algal kill. The only case in which humic acid was not demonstrably protective was at a low concentration (4 mg/L TOC). It is possible that in a long-term test, low humic acid levels may not protect algae, because the copper may be released from the humic acid complex. Alkalinity and the humic acid concentration (TOC) both complex ionic copper, however alkalinity appears to be more important in determining available ionic copper in freshwater. At alkalinities greater than 10 mg/L (as CaCO₃) and humic acid less than 8.0 mg/L, alkalinity predominated in determining available ionic copper. A short term (4-hour) procedure involving measurement of oxygen production by algae exposed to copper was also used to determine the effect of humic acid on ionic copper toxicity to algae. The data showed that short-term tests were best used to predict trends shown in the long-term tests. Both Selenastrum capricornutum (a green alga) and Microcystis aeruginosa (a blue-green alga) were protected from ionic copper by humic acid. Oxygen production was found to be best used to approximate toxic concentrations of a suspect compound, as opposed to being used to precisely determine toxic concentrations. / Master of Science

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

Thesis (M.S.)--University of Hawaii at Manoa, 2006. / Includes bibliographical references (leaves 28-33). / 50 leaves, bound ill. 29 cm

The aim of the present study was to determine the potential impact of intertidal grazers on the distribution of macro algae on the south coast of South Africa. Particular attention was paid to the large patellid limpet, Patella oculus, which is found thoughout the intertidal zone. Studies of gut contents revealed that Patella oculus was capable of ingesting not only the thallus of foliose (eg. Ulva spp.) and encrusting coralline macroalgae, but also spores and diatoms. The inclusion of these relatively small particles in the diet was surprising, as electron micrographs of the radula of P.oculus revealed that it is typically docoglossan in structure. Such radulae are thought to be poorly suited for collecting small food particles. Sand made up a significantly higher proportion of the gut contents than other particles at all shore heights, which suggests that P.oculus might be capable of excavating the rocky substratum, or of sweeping up sand, while searching for food. Analysis of the gut contents of other local herbivorous molluscs, was also carried out. These species included the winkles, Oxystele variegata and O.sinensis, and the small pulmonate limpets, Siphonaria concinna, S.capensis, and S.serrata. The guts of all species contained mainly spores and diatoms, although small fragments of Ulva sp. were found. The population structure of Patella oculus was investigated at two sites, Cannon Rocks and Old Woman's River. At Cannon Rocks, mean shell length of low-shore animals was significantly lower than that of both mid- and high-shore animals, while at Old Woman's River, no significant difference was found among shore heights. A regression equation for In (shell length) vs In (dry weight) was calculated, and based on length data, the biomass density (g dry mass.m⁻²) of P.oculus at Old Woman's River was estimated. Values ranged from 2.8 on the low- and midshore to 0.37 on the high-shore. A manipulative field experiment was used to determine the impact of mesograzers and macrograzers (such as Patella oculus) on the distribution of intertidal macro algae on the mid- and low-shore at Old Woman's River. Grazers were excluded using mesh cages (mesh size = 3mm), in two separate experiments, one in winter and the other in spring. Percentage cover of macroalgal species and sessile invertebrates was estimated at approximately 6 week intervals for up to 3 months. MANOV A showed that treatments did not significantly affect cover of macroalgae or barnacles during winter. However, towards the end of the spring experiment (midshore only) cover of barnacles and green foliose turfs did increase in those plots from which mesograzers and/or macro grazers were excluded. The failure of the statistical tests to detect significant differences at some time intervals may have been caused by high levels of variation among replicates. This suggests that factors other than grazing are of overriding importance in determining the distribution of local macroalgae. The existence of a possible symbiotic relationship between Patella oculus and the red foliose alga, Gelidium pristoides, was investigated. The availability of various substratum types, including rock, limpet shells, barnacles etc., and the proportion of the total cover of G.pristoides on each, was calculated. It was shown that a significantly higher proportion of the alga grew on limpet shells, although the availability of this substratum type was low. It is thought that the aggressive behaviour of P.oculus prevents all but juvenile Patella longicosta from grazing on its shell, thus providing a refuge from grazing for G.pristoides.

Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The study of climate change and its effect on the eutrophication of surface waters is a current and critically important study for the well-being of the entire planet. Within the same emission scenario various probable climate change models outcomes are possible that affect the water quality of a body of water. Voëlvlei is an off-channel dam that supplies water to the city of Cape Town in the Western Cape Province of South Africa. Historically, it is a eutrophic dam and with climate change, its water quality is expected to worsen. Four statistically downscaled climate models are used to produce meteorological outputs that drive the hydrodynamic and water quality model. The times simulated were the present day (1971-1990), the intermediate future (2046-2065) and the distant future (2081-2100). The operating procedure was not expected to change for the dam and inflows and withdrawals were kept the same for each of the simulation periods. The water quality model CE-QUAL-W2 version 3.6 was used. The bathymetry was validated with measured data. The model was calibrated for temperature, phosphorus loading, ammonium, nitrite-nitrates and chlorophyll-a concentration. The model was used to predict a present day situation in the dam, which was the basis from which future changes would be assessed. The main driver for algal growth other than nutrients and light was water temperature, which was linked to air temperature. With climate change, the air temperature will raise and enhance algal growth. The limiting nutrient was phosphorus during the winter and the rest of the year nitrogen limits algal growth. In the present day, the dominant algal group was the green algae. With climate change an increase in the surface water temperature will increase evaporation and cause a decrease in the yield of the dam and further concentrates the algal nutrients. The surface phosphates concentration show increases in all months but especially in autumn. The total algal growth was increased annually and especially during autumn, signalling a seasonal shift and lengthening of the bloom season. The dominant algae however are still the green algae. There will be an increase in the annual concentration of diatoms. The green algae are present in the highest concentrations when compared to diatoms and cyanobacteria. The increase in its nutrients throughout the year as well as the increased water temperature allowed for unabated growth the entire year with peaks earlier in the year during autumn. Cyanobacteria are present at the surface for the entire year at significant concentrations but with intermediate and future climate change their concentrations does not change significantly. The result for cyanobacteria was inconclusive as the inter-variability between the climate models has the greatest variability for cyanobacteria, with 2 models showing an increased concentration and 2 a decreased concentration for intermediate and future time-period. For climate change, the water quality worsens especially during winter. With climate change water quality will worsen earlier in the year confirming a seasonal shift. The modelling of dissolved oxygen proved daunting as the results indicated supersaturation. The concentration of dissolved oxygen does not vary much as would be expected due to the warmer waters. / AFRIKAANSE OPSOMMING: Die studie van klimaatsverandering en die uitwerking daarvan op die eutrofiseering van die oppervlaktewater is 'n huidige en krities belangrike studie vir die welsyn van die hele planeet. Binne dieselfde emissie scenario, is verskeie moontlike uitkomste van klimaat modelle moontlik en die invloed op die kwaliteit van die oppervlakwater. Voëlvlei is 'n buite-bedding dam wat water verskaf aan die stad van Kaapstad in die Westelike Provinsie van Suid-Afrika. Histories is dit is 'n eutrofiese dam en met die verandering van die klimaat sal die kwaliteit van die water na verwagting verswak. Vier statisties afgeskaal klimaat modelle word gebruik om meterologiese toesttande te skep en hiedie word dan gebruik as invoer vir die hidrologiese and water kwaliteits model vir die huidige situasie (1971-1990), die intermediêre toekoms (2046-2065) en die verre toekoms (2081-2100). Die bedruifs-proses vir die dam was nie verwag om te verander nie en die invloei en onttrekkings was dieselfde gehou vir elk van die simulasie periodes. Die watergehalte model CE-QUAL-W2 3.6 was gebruik. Die bathymetrie was bevestig met gemete data. Die model was gekalibreer vir temperatuur, fosfor, ammonium, nitriet-nitrate en chlorofil-a konsentrasie. Die model was gebruik om 'n huidige situasie in die dam te simuleer, wat die basis vir klimaatsveranderinge sou wees. Die vernaamste aandrywer vir die alge groei anders as voedingstowwe en lig, was water temperatuur, wat met lugtemperatuur gekoppel was. Met klimaatsverandering word die lugtemperatuur verhoog en alge groei. Die beperkende voedingstof was fosfor gedurende die winter en die res van die jaar was die dam stikstof beperk. Die dominante alge-groep in die huidige situasie was die groen alge. Met klimaatsverandering stuig die temperatuur van die oppervlakwater, verhoog verdamping, veroorsaak afname in die vlak van die dam en verhoog die konsentrasie van die alge voedingstowwe. Die oppervlak fosfate konsentrasie verhoog in al die maande veral in die herfs. Die totale alge groei jaarliks en veral gedurende die herfs, 'n teken van 'n seisoenale verskuiwing en verlenging van die blom seisoen. Die dominante alge was nog steeds groen alge. Daar sal 'n toename in die jaarlikse konsentrasie van diatome wees. Die groen alge is in die hoogste konsentrasies vergelyk met diatome en sianobakterieë. Die toename in die voedingstowwe deur die loop van die jaar, sowel as die verhoogde watertemperatuur kan vir 'n onverpoos groei vir die hele jaar, veral in die herfs. Sianobakterieë is teenwoordig vir die hele jaar op beduidende konsentrasies, maar met intermediêre en toekomstige klimaat verander die konsentrasies nie veel nie. Die resultaat vir sianobakterieë was onoortuigend as gevolg van die inter-veranderlikheid tussen die klimaats modelle, met 2 modelle wat 'n toename in konsentrasie voorspel en 2 'n afname in konsentrasie voorspel. Vir klimaatsverandering, die kwaliteit van die water vererger veral in die winter. Met klimaatsverandering skyf hierdie verswakking van water kwaliteit na vroeër in die jaar, wat bevestig 'n seisoenale skui vir verergering. Die modellering van opgeloste suurstof was uitdagende en die resultate was super-versadig. Die konsentrasie van opgeloste suurstof wissel nie veel as wat verwag sou word as gevolg van die warmer water.