Biocoagulant with Frother Properties for Harvesting Invasive Microalgae Colonies from the Eutrophicated System

Coagulation/flocculation is an auspicious procedure for microalgae biomass harvesting. However, the issues of coagulant cost, toxicity, and the large volume of contaminated, nonrecyclable culture medium that is usually generated negate the industrial applications. Therefore, a biocoagulant with frother properties [i.e., the fruit seed extract of Margaritaria discoidea (MDE)] was evaluated as a green biocoagulant to obviate these challenges. The harvesting efficiency (HE %) and the rate parameters were determined in samples collected from a eutrophicated fish pond. The MDE-harvested biomass characteristics were compared with that of the nonchemical approach. Apatococcus lobatus, Arthronema africanum, and Aphanocapsa sp. were the suite of microalgae in the eutrophication system, and the MDE induced the floatation of the microalgae floccule. HE of 98% was achieved and the process obeyed the first-order flotation kinetic. The galactomannans fraction of the MDE flocculated the microalgae cells via the adsorption and bridging mechanism, while the saponin fraction served as the frother that enabled the floatation of the microalgae floccule. The inorganic fraction of the MDE biomass was higher than that of the biomass obtained from the non-chemical method, but the proximate an elemental composition were comparable with the non-chemical method. As shown in the FTIR analysis, no extraneous functional group was introduced into the MDE-harvested biomass. The settleability and filterability of the harvested biomass were comparable with the biomass of other algae species harvested with other types of coagulants.