Master of Science in Engineering Science (MSES)
Engineering Science (Interdepartmental Program)
A highly sensitive miniaturized biomass transducer is necessary for continuous and reliable monitoring of the microalgal biomass in a computer controlled, automated microalgal bioreactor. Previous known methods to determine microalgal biomass applicable in these bioreactors are based on single wavelength turbidimetric or fluorescence. The objectives of this research were to (1) determine the light absorption characteristics of some commercially applicable microalgae in the electromagnetic wavelength range of 200-800 nm (2) design and construct a new miniaturized biomass transducer (3) process the transducer output to correlate with the biomass. Wavelength sensitivity analysis was conducted on the commercially important microalgal species - Nannochloropsis oculata, Isochrysis galbana and Thalassiosira weissflogii, for a growth range of 0-500 mg dry wt L-1. Maximum absorptions were found at UVC, followed by blue and red regions of the electromagnetic spectrum. A new biomass transducer based on UVC measurement was designed and constructed. The measurements were processed for signal conditioning and higher sensitivity. It was followed by further processing in a central control computer to filter the noise present in UVC measurement. A statistical relationship was developed for signal processing between the individual variables and a new model for the calibration curve was proposed. The new biomass transducer was tested using the developed signal processing algorithm and the calibration with individual microalgal samples as well as the mixed samples independent of calibration curve. The tested results gave an average error < 10% relative to the mean of actual readings.
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Hegde, Amar Shivaram, "Development of a biomass transducer for automated microalgal bioreactors" (2007). LSU Master's Theses. 2771.