Cultivation of freshwater microalgae in wastewater from a Swedish pulp and paper mill

Examensarbete för masterexamen

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Type: Examensarbete för masterexamen
Master Thesis
Title: Cultivation of freshwater microalgae in wastewater from a Swedish pulp and paper mill
Authors: Appelberg, Ingrid
Abstract: Microalgae have potential to clean wastewater from inorganic nutrients while converting inorganic carbon dioxide in flue gas into valuable products. Wastewater from Nordic Paper Bäckhammar, a Swedish pulp and paper mill, was investigated for its ability to support growth of 15 freshwater microalgae species. Two promising species, Scenedesmus obliquus and Dictyosphaerium pulchellum, were further investigated in larger batch cultivations. Air with 1% carbon dioxide was bubbled through the cultures, and municipal wastewater was added in different amounts as additional nutrient source. Cell growth, nutrient reduction and cell content were evaluated. Specific growth rates of 0.013-0.082h-1 and 0.023-0.064h-1, with generation times of 8.5-52.9h and 10.8-30.5h were obtained for S. obliquus and D. pulchellum respectively. Final dry weights reached 0.57-1.29g/l and 0.62-1.55g/l respectively. The results indicated that nutrient availability was a limiting factor for cell growth, and in particular nitrogen availability. The addition of municipal wastewater led to higher cell densities. Cell composition varied over the course of cultivation where total protein and carbohydrate content decreased and total lipid content increased for all cultures. The final lipid content of S. obliquus was 19-23% of dry weight, which is consistent with previously reported data. Literature data for D. pulchellum was not found, and the lipid content amounted to 33-35% of dry weight in the present study, slightly higher than S. obliquus. Nutrient reduction was comparable to other reported values; after eight days, close to 100% NH4+ was eliminated for both species. D. pulchellum seemed to reduce PO43- faster than S. obliquus with 63-67% after eight days compared to 25-46%. After three weeks 79-98% PO43- was eliminated for both species. Both S. obliquus and D. pulchellum showed potential for production of biomass while cleaning wastewater and are interesting candidates for further research with addition of flue gas. Of the two, S. obliquus has previously proved good growth in flue gas experiments, whereas not much research has been done on D.pulchellum.
Keywords: Energi;Livsvetenskaper;Materialvetenskap;Annan teknik;Energy;Life Science;Materials Science;Other Engineering and Technologies
Issue Date: 2013
Publisher: Chalmers tekniska högskola / Institutionen för kemi- och bioteknik
Chalmers University of Technology / Department of Chemical and Biological Engineering
Collection:Examensarbeten för masterexamen // Master Theses

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