An experimental investigation of microalgal dewatering efficiency of a belt filter system
Issue Date
2014-05-31Author
Sandip, Anjali
Publisher
University of Kansas
Format
153 pages
Type
Dissertation
Degree Level
Ph.D.
Discipline
Mechanical Engineering
Rights
This item is protected by copyright and unless otherwise specified the copyright of this thesis/dissertation is held by the author.
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Show full item recordAbstract
Profitable large-scale production of biofuel from microalgae has not yet been demonstrated. A major bottleneck is high operational cost of microalgal harvesting. This is due to small cell size and dilute microalgal suspension. A belt filter system is preferred over other dewatering technologies as it has lower energy consumption. However, a microalgal feed concentration of 10 - 40 g dry wt. /L is required prior to dewatering on a belt filter system. The objective of this study was to investigate the microalgal dewatering efficiency of a belt filter system. A prototype belt filtration system designed for feed concentration of 50 g dry wt. /L was used for this investigation. A mixed laboratory culture of freshwater species dominated by three eukaryotic green microalgae (Chlorella vulgaris, Scenedesmus sp., and Kirchneriella sp.) was cultivated in wastewater effluent. Bench-scale gravity filtration tests were conducted to determine the filtration belt mesh needed for the prototype system. Based on the test results a 70 micron mesh size resulted in the highest microalgal recovery rate and was subsequently used for all dewatering tests conducted in this study. Belt dewatering tests conducted on untreated microalgal suspensions - pond water at the KU Field Station and stationary growth phase samples from the microalgal lab culture - resulted in negligible recovery. The highest concentration of microalgal suspension available for testing on the prototype belt filtration system was 6 g dry wt. /L obtained from biomass settling tanks at the Lawrence, Kansas domestic wastewater treatment plant that resulted in 84% biomass recovery. To further investigate this, 54 Liters of 4 g dry wt. /L were produced from bench-scale flocculation using an alum dosage of 200 mg/L at pre-test pH value of 6.5. Results of belt dewatering tests indicated that the percent of microalgae recovered for 4 g dry wt. /L suspension, 46%, was significantly lower than 6 g dry wt. /L suspension. Sealed filter section would likely improve the microalgal recovery (subsequently reducing the number of filtration passes required for maximum microalgal recovery).
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- Engineering Dissertations and Theses [1055]
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