Phosphorus Removal from Wastewater by Phosphorus-Starved Algea

Abstract

Two species of green algae, Selenastrum capricornutum and Scenedesmus sp. were evaluated for phosphorus removal from wastewater. Phosphorus-starved algae were used. The cells were exposed to varied levels of phosphorus in K2HP04 solution, clarified effluent and mixed liquor. Affect of variables such as cell concentration, contact time, light and temperature on P removal were also evaluated. Scenedesmus was capable of removing larger amounts of phosphorus per cell compared to Selenastrum. The rate of phosphorus removal was directly related to the concentration of orthophosphate in the substrate. Scenedesmus removed 99% of the phosphorus from a domestic wastewater {approximately 2.0 mg P/1) in less than 2 hours. Increased cell numbers and increased contact time resulted in greater phosphorus removal. There was no significant affect of light on the rate of phosphorus removal over a 24 hour period. Uptake efficiency decreased with a decrease in temperature. In a settling test, after phosphorus removal, 99% of Scenedesmus cells settled out by gravity compared to only 50% of Selenastrum cells.