Effect of Processing Parameters on Flocculation of Picochlorum oklahomensis

Abstract

AbstractThe flocculation process is commonly used to separate suspended solids from water. The microalgae strain, Picochlorum oklahomensis (PO), was investigated for its flocculation characteristics. Efficiencies of biopolymer addition, pH adjustment and electroflocculation for biomass recovery from the culture medium were examined. Flocculation efficiency of PO increased sharply above pH 11 and reached 97 % at pH 13. Chitosan was more effective in flocculating PO cells than sodium alginate and cationic starch. A generalized linear mixed model using a beta distribution for response was utilized for optimization of the chitosan flocculation process variables. Biomass: chitosan ratio, pH and settling time (ST) were the independent variables. There were significant 3‐way interactions among the variables. The highest PO flocculation efficiency, 98.4 %, was obtained at biomass: chitosan ratio of 2.78, pH 9 and ST of 12 h. The electroflocculation efficiency improved with increasing current, operation time (OT) and ST. The highest electroflocculation efficiency, 99.74 %, was obtained under the following conditions; 0.8 A (ampere) and 15 min and 12 h, OT and ST, respectively. This study demonstrated that pH adjustment, chitosan addition and electroflocculation were all technically viable methods to flocculate PO cells. However, selection of the most suitable technique and the optimum treatment conditions needs to be based not only on the application of algal biomass, but also on an economic feasibility study.