Secondary wastewater treatment by microalgae isolated from Gaborone oxidation ponds

Abstract

Microalgae play a fundamental role in primary and secondary wastewater treatment. In this work the growth, photosynthetic activity and removal of phosphorus from wastewater effluents by indigenous blue-green algal species, Spirulina and Oscillatoria, isolated from Gaborone oxidation ponds was studied. Oscillatoria and Spirulina cultured in wastewater effluents grew as much as the algae cultured in specific medium. The photosynthetic activity for Oscillatoria and Spirulina cultured in wastewater effluents was 91 and 122 mole of O2 evolved mg —1 chlorophyll a h —1 respectively compared to 52 and 92 mole of O2 evolved mg —1 chlorophyll a h —1 respectively when cultured in defined medium, BG110. Oscillatoria removed 100% orthophosphate within six days of culturing while Spirulina removed 86% after eleven days of culturing. The results indicate that these blue-green algal species can grow in wastewater effluents for biomass production and for further reduction of excess nutrients from wastewater effluents before discharge into the receiving streams.


(Botswana Journal of Technology: 2002 11(1): 39-43)