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Thesis (Ph. D.)--University of Queensland, 2002. / Includes bibliographical references.

Thesis (M.S.) in Civil Engineering--University of Maine, 2001. / Includes vita. Advisory Committee: Chet A. Rock, Prof. of Civil and Environmental Engineering, Advisor; Willem Brutsaert, Prof. of Civil and Environmental Engineering; Rose Mary Seymour, Asst. Prof. of Bio-Resource Engineering. Includes bibliographical references (leaves 100-104).

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Microalgae reactors, commonly known as photobioreactors, have become increasingly popular as an alternative for wastewater treatment. These systems reduce pollutants and remove nutrients such as nitrogen and phosphorous compounds from wastewater utilizing microalgae and bacteria. The biomass produced in the reactors can potentially be used to produce biofuels and decrease some of the energy demands of the process. Wastewater treating photobioreactors are a relatively new technology and many aspects of their microbiology need further study. This thesis presents a broad overview of the algal and bacterial communities present in these systems by looking at the most important species, metabolic pathways and growth dynamics of both algae and bacteria. The experiments presented in this thesis were conducted using municipal wastewater from the Västerås wastewater treatment plant. The wastewater was inoculated with algae from Lake Mälaren and compared to non-inoculated reactors. Overall, the inoculated reactors demonstrated better algal growth than those that were not inoculated. The tested systems also removed much of the ammonium and phosphorous present in the wastewater. The dominant algae in the tested systems belonged to the genera Scenedesmus, Desmodesmus and Chlorella. In addition to algae, the systems contained a large number of bacteria, mostly from the phyla Proteobacteria and Bacteroidetes. The algal photobioreactors contained a lower abundance of genes related to nitrogen metabolism, virulence and antibiotic resistance compared to the initial wastewater, showing that a shift in the bacterial community had occurred. The bacteria found in the systems were shown to be involved in synthesis of vitamins essential for algae growth such as vitamin B12, suggesting cooperation between the bacteria and algae. / I takt med att världens befolkning ökar, så produceras dagligen allt mer avfall. Detta kan orsaka stora problem för miljön. När det byggs nya system för vattenrening behöver vi även ta hänsyn till kravet att minska energiåtgången. Dagens vattenreningssystem har vissa tillkortakommanden när det gäller reningsnivåer och energianvändning. Ett alternativ till dagens system, kan vara fotobioreaktorer, dvs. vattenrening med hjälp av mikroalger. Dessa system använder mikroalger och bakterier för att rena vattnet från föroreningar, kväve och fosfor. Vattenrening med fotobioreaktorer är en relativt ny teknik. Flera aspekter gällande biologin i dessa system har ännu inte studerats i detalj. Den här avhandlingen presenterar en översikt av de alger och bakterier som är aktiva i fotobioreaktorer. Andra viktiga aspekter som tillväxt, arter samt vattenreningsförmåga har också studerats. Ett antal försök genomfördes där alger från Mälaren tillsattes i vatten från Västerås kommunala vattenreningsanläggning. Storleken på försöken varierade mellan 250 ml och 20 liter. Det visade sig att algerna hade en bra tillväxt samt att mängden ammonium och fosfor minskade i vattnet under försöksperioden. De alger som tillväxte mest i studien tillhörde Scenedesmus, Desmodesmus och Chlorella. Förutom alger tillväxte även ett stort antal bakterier från grupperna Proteobacteria and Bacteroidetes. Dessa bakterier visade sig syntetisera viktiga vitaminer, t.ex. vitamin B12, som algerna normalt inte kan syntetisera själva. Sammanfattningsvis, så presenterar denna avhandling viktig information gällande alger och bakterier i en fotobioreaktor. Informationen kan vara ett viktigt bidrag till framtida utveckling av storskaliga fotobioreaktorer för vattenrening.

Microconstituents (MCs) have become an emerging concern to scientists and researchers. Due to the development of analytical technology, it is now possible to study MCs at ηg/L to μg/L levels. Wastewater treatment plants (WWTPs) are the major point source for MCs entering the environment based on the literature. WWTPs are known to be unable to remove many MCs to a safe level. In order to fully understand the fate of MCs in WWTPs and to further improve the design of WWTPs in terms of MC removal, it is necessary to examine removal mechanisms such as sorption and biodegradation in WWTPs. Three MCs, bisphenol A (BPA), 17-α-ethinylestradiol (EE2) and triclosan (TCS), were chosen for this study. They are chemicals reported to be hydrophobic and have low vapor pressure, which makes sorption a highly potential removal mechanism. Primary sludge and activated sludge (AS) were used to perform sorption kinetics and isotherm experiments for BPA, EE2 and TCS. Primary sludge was collected from local WWTPs, and AS was generated from a lab-scale continuous flow bioreactor system maintained at solids retention times of 15, 10 and 5 d and hydraulic retention time (HRT) of 6 h. Alum was added to synthetic wastewater influent at concentrations typically used for phosphorus removal at some plants. Alum has the potential to change sludge structure and influence the sorption process. A comparison was made with AS as the adsorbent with and without alum addition to the AS to study the influence of alum on the sorption processes. The selected MCs were found to reach sorption equilibrium with primary sludge within 7 h. A pseudo second-order kinetic model was an excellent fit to describe the sorption processes of selected MCs. The solids-liquid partitioning coefficient (Kd) was determined for the three chosen MCs. The Kd values found for primary sludge and AS are very close. The Kd for MCs sorbed to AS in this study were compared with the Kd for AS without alum addition. Although alum addition showed no influence on effluent soluble chemical oxygen demand, it decreases the Kd for BPA and EE2 sorbed to AS. In contrast, a much higher Kd for TCS was observed for AS with alum addition. Judging from the R2 values, the linear sorption model is not suitable for some of the isotherms. Langmuir and Freundlich sorption isotherms were further used to fit the experimental data by applying linear regression and nonlinear regression approaches. The Freundlich isotherm was found to be the most suitable model to describe the experiment data.