Thesis (Ph. D.)--University of Canterbury, 2006. / Typescript (photocopy). Includes bibliographical references (leaves 128-138). Also available via the World Wide Web.

Algal bloom can significantly impact reverse osmosis desalination process and reduce the drinking water production. In 2008, a major bloom event forced several UAE reverse osmosis plants to stop their production, and in this context, a better understanding of UF membrane fouling caused by algal organic matter (AOM) is needed, in order to adjust the filtration conditions during algal bloom events. Polymeric MF/UF membranes are already widely used for RO pretreatment, but ceramic UF membranes can also be an alternative for the filtration of marine algal solutions. The fouling potential of the Red Sea and the Arabian Sea, sampled at different seasons, along with four algal monocultures grown in laboratory, and one mesocosm experiment in the Red Sea was investigated. Algal solutions induce a stronger and more irreversible fouling than terrestrial humic solution, toward ceramic membrane. During algal bloom events, this fouling is enhanced and becomes even more problematic at the decline phase of the bloom, for a similar initial DOC. Three main mechanisms are involved: the formation of a cake layer at the membrane surface; the penetration of the algal organic matter (AOM) in the pore network of the membrane; the strong adhesion of AOM with the membrane surface. The last mechanism is species-specific and metal-oxide specific. In order to understand the stronger ceramic UF fouling at the decline phase, AOM quality was analyzed every two days. During growth, AOM is getting enriched in High Molecular Weight (HMW) structures (> 200 kDa), which are mainly composed by proteins and polysaccharides, and these compounds seem to be responsible for the stronger fouling at decline phase. In order to prevent the fouling of ceramic membrane, coagulation-flocculation (CF) using ferric chloride was implemented prior to filtration. It permits a high removal of HMW compounds and greatly reduces the fouling potential of the algal solution. During brief algal bloom events, CF should be implemented prior to UF to protect the membranes. A comparison between polymeric and ceramic UF membranes showed that ceramic membrane suffers from a stronger fouling but permits a better removal of DOC and particularly HMW compounds.

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A study was made on morphological and cytological features of four Rivulariaceae strains from marine, partially saline and freshwater environments using three versions of saline and freshwater media (standard. - Fe. low P). A brackish Anabaena sp. was used for comparison. Subculture to - Fe medium led to marked changes in morphology and cytology. These were (base to apex): a series of new heterocysts apical to the original one. Intra-thylakoldal vacuolation. Lack of cyanophycin granules, presence of polyphosphate granules, pale colour, brown sheath, short hair and low hairiness. With low P medium, the changes were the opposite. Hairs did not form in Calpthrix D253 in saline medium, whether the cultures were in - Fe or low P medium. Downshift from saline to freshwater medium led to the synchronized development of hairs in most trichomes. Whereas the reciprocal upshift led to loss of hairs. The Fe content was studied in three Rivulariaceae and Anabaena in batch culture in high and low P media, which eventually led to Fe- and P- limitation. respectively. The content reached a maximum by 24 h in all strains, decreasing subsequently from 1.80 - 0.06 % dry weight. Siderophore production was tested in four Rivulariaceae and Anabaena in saline and freshwater media. Two Calothrlx strains and Anabaena produced a siderophore in freshwater medium. Influence of Fe status on nitrogenase activity was tested in two Rivulariaceae and Anabaena in saline and freshwater media during batch culture. Peaks of nitrogenase activity in the former came three to five days after the Fe peak, by which stage Fe content had dropped to within the range 0.6 - 0.3 % dry weight. In contrast, peak activity in Anabaena came within a day of the Fe peak. Addition of Fe to Fe-limited cultures led to rapid increase in activity. The significance of these data on morphology, cytology and physiology and possible interactions between Fe- and P-limitation are discussed.

Since many approaches to dealing with algal blooms are inefficient, expensive, or harmful, it was concluded that a biologically-synthesized chemical agent, specifically inhibitory to pre-bloom algal cells, might prove helpful in controlling algal blooms. Fungi were chosen as the biological entities to investigate for such a chemical.

Excessive phosphorus (P) is one of the major pollutants in natural water that are responsible for algal blooms and eutrophication. P removal by soil and slag is an attractive solution if the P sorption capacity of soil or slag is significant. To design an efficient land treatment facility, basic information on the behaviour of P in the media-water environment is required. In this study, detailed experiments were conducted to study P removal under static and dynamic conditions, and mathematical models were developed to describe these processes. The kinetic studies on P sorption onto a sandy loam soil from North Sydney, Australia, and dust and cake waste products from the BHP steel industry revealed that P sorption is a slow process. More than 90% of the P was adsorbed within 70, 12 and 60 hours in a mixing system for soil, dust and cake respectively while it was within 240, 24 and 120 hours respectively in a static (no stirring) system. Dust adsorbed P the most, compared to the other adsorbents (220-225 times and 4-5 times of the sorptivity of soil and cake respectively). P sorption in the batch experiments was described better by an equation using the Langmuir isotherm than one using the Freundlich isotherm. The kinetics of P sorption were satisfactorily explained by a static, physical, non-equilibrium sorption model (SPNSM). The pH of the P solution played a critical role in the extent of removal and the removal mechanisms of P. Removal was at a minimum at pH 2. The effect of pH on P removal varied depending on the type of adsorbents and the initial P concentration. The dominant removal mechanism of P at pH<8 was physical sorption, while it was chemical precipitation at pH>10. Batch flocculation experiments revealed that the P removal efficiency increased with an increase of adsorbent dose, flocculation (contact) time and mixing rate. P sorption is affected by the presence of NH4 which competes for available sites on the adsorbents. The amount of P adsorbed by dust and cake in the presence of NH4 was less than that in a single solute system. The reduction percentage of P for dust ranged from 33 to 57%. Detailed column experiments conducted with soil, dust and cake as media indicated that dust and cake have much higher sorption capacities than soil. The solid phase P concentrations on dust and cake calculated from batch experimental isotherm constants are substantially higher than those estimated.

Electrocoagulation was compared to centrifugation at pilot scale for harvesting Nannochloris oculata and Nannochloropsis salina for biodiesel production. The pilot scale testing is a proof of concept and no optimization was conducted. Testing used the KASELCO commercial electrocoagulation system. The KASELCO electrocoagulation system successfully coagulated microalgae in laboratory testing. Aluminum and stainless steel electrodes successfully recovered algae in laboratory testing. Electricity consumed was lowest using aluminum electrodes in laboratory testing, but inconsistently coagulated microalgae at the pilot scale. Stainless steel electrodes consistently recovered algae and were selected as the primary electrode to treat microalgae at the pilot scale. Scaling power settings to pilot testing using laboratory data was successful following KASELCO’s proprietary guidelines. The KASELCO electrocoagulation system showed an electrical reduction in pilot scale operational cost for harvesting. Economic analysis using the Algae Income Simulation Model concluded that the KASELCO electrocoagulation system increase net present value of a commercial algae farm by $56,139,609 using a discount factor of 0.04. The KASELCO electrocoagulation system was calculated to use 26 kWh/ton at a commercial algae farm. However, cultivation and extraction processes are energy intensive, resulting in minimal electrical savings for the algae farm. The increase in net present value reduced production costs at the algae farm by 1%. The probability of success for the microalgae farm was zero for all scenarios analyzed. While a reduction in capital and operational costs were observed, several improvements, including harvesting using electrocoagulation, in cultivation, extraction, and conversion are necessary for economic success for biodiesel production using algae farms.

No description available.

Excessive phosphorus (P) is one of the major pollutants in natural water that are responsible for algal blooms and eutrophication. P removal by soil and slag is an attractive solution if the P sorption capacity of soil or slag is significant. To design an efficient land treatment facility, basic information on the behaviour of P in the media-water environment is required. In this study, detailed experiments were conducted to study P removal under static and dynamic conditions, and mathematical models were developed to describe these processes. The kinetic studies on P sorption onto a sandy loam soil from North Sydney, Australia, and dust and cake waste products from the BHP steel industry revealed that P sorption is a slow process. More than 90% of the P was adsorbed within 70, 12 and 60 hours in a mixing system for soil, dust and cake respectively while it was within 240, 24 and 120 hours respectively in a static (no stirring) system. Dust adsorbed P the most, compared to the other adsorbents (220-225 times and 4-5 times of the sorptivity of soil and cake respectively). P sorption in the batch experiments was described better by an equation using the Langmuir isotherm than one using the Freundlich isotherm. The kinetics of P sorption were satisfactorily explained by a static, physical, non-equilibrium sorption model (SPNSM). The pH of the P solution played a critical role in the extent of removal and the removal mechanisms of P. Removal was at a minimum at pH 2. The effect of pH on P removal varied depending on the type of adsorbents and the initial P concentration. The dominant removal mechanism of P at pH<8 was physical sorption, while it was chemical precipitation at pH>10. Batch flocculation experiments revealed that the P removal efficiency increased with an increase of adsorbent dose, flocculation (contact) time and mixing rate. P sorption is affected by the presence of NH4 which competes for available sites on the adsorbents. The amount of P adsorbed by dust and cake in the presence of NH4 was less than that in a single solute system. The reduction percentage of P for dust ranged from 33 to 57%. Detailed column experiments conducted with soil, dust and cake as media indicated that dust and cake have much higher sorption capacities than soil. The solid phase P concentrations on dust and cake calculated from batch experimental isotherm constants are substantially higher than those estimated.