Removing Soluble Phosphorus from Tertiary Municipal Wastewater Using Phosphorus- Deprived, Filamentous Microalgae

Harmful algal blooms (HABs) can be detrimental to ecosystems, human health, and economies. The low levels of phosphorus remaining in the effluent of municipal wastewater treatment plants can contribute to HAB formation. To achieve more complete phosphorus removal, an effluent treatment method has been proposed that uses phosphorus-deprived, filamentous microalgae to quickly assimilate soluble phosphorus to low concentrations. This study investigated two parameters that influence the feasibility of such a system: (1) the biomass growth productivity of algal cultures during the phosphorus deprivation period and (2) the correlation between the duration of this period and the phosphorus uptake rate by the biomass when contacted with the water to be treated. A single strain of filamentous algae, Tribonema minus, was used. Two experiments lasting 8-9 days compared the biomass productivity of cultures of T. minus grown in phosphorus-replete and -deplete media. While no significant difference in productivity was observed between treatments, further studies should be done to confirm this finding. In addition, 39 uptake contact experiments were conducted. The soluble phosphorus uptake rate was measured for algae deprived of phosphorus for 0 to 12 days of growth. The highest observed uptake rate was 3.83 mg P/g VSS-h, during the first three hours of contact, by biomass that had been phosphorus-deprived for 12 days. The correlation between phosphorus deprivation duration and 3-h uptake rate was 0.34 mg P/g VSS-h per day of deprivation (R2 = 0.81). Additional development efforts seem justified based on these results