Available at: https://digitalcommons.calpoly.edu/theses/2961
Date of Award
12-2024
Degree Name
MS in Civil and Environmental Engineering
Department/Program
Civil and Environmental Engineering
College
College of Engineering
Advisor
Tryg Lundquist
Advisor Department
Civil and Environmental Engineering
Advisor College
College of Engineering
Abstract
Phosphorus (P) is a nutrient that is essential for crops, but it is a non-renewable resource. P recovery from wastewater would lessen P pollution and extend the P supply for fertilizers. Filamentous microalgae can remove soluble inorganic P from water and assimilate it into recyclable biomass. To further develop this concept by using P-depleted filamentous microalgae, this research pursued three goals: to determine (1) the biomass-specific P uptake rates of Tribonema minus and Uronema sp., (2) how long Uronema sp. can be cultivated in P-depleted state (not P-starved) and continue substantial uptake, and (3) if the P dosing rates impact the uptake response and/or productivity of Uronema sp. Raceway tanks were given little or no soluble P to generate P-depleted biomass. The P-depleted biomass was then used for uptake contact experiments in which P uptake rates and biomass P content were measured. The long duration (0-10 h) uptake rates were not substantially different for T. minus and Uronema sp., but Uronema sp. tended to uptake more quickly in the short duration (0-2 and 0-3 h) of the contact period. Other experiments focused on prolonged deprivation, during which the raceways received P every day or every three days, although the mass of P dosed over the long term was equivalent in all raceways. Uronema sp. could be cultivated in a P-depleted state for an average of 10 days before the biomass was unable to have substantial P uptake. The uptake rates for these two dosing regimens were assumed to be the same because the 0-6 hour average rate was 0.33 mg P/g VSS-h (dosed every day) and 0.36 mg P/g VSS-h (dosed every three days). Future studies should confirm if Uronema sp. consistently assimilates more P at a faster rate in the winter compared to the spring, as observed in the present study.