Advanced Processes of Cyanobacteria and Cyanotoxins Removal in Supply Water Treatment

Abstract

The efficiency of Moringa oleifera (MO) seeds as a natural coagulant in the coagulation/flocculation process, followed by nanofiltration (NF) for the removal of cyanobacterial cells and cyanotoxins is investigated. "Synthetic water" prepared for the tests comprised de-ionized water with an inoculum of microcystis protocystis cells to obtain turbidity within the 50-450 NTU range. Methodology followed two steps: 1) coagulation/flocculation/sedimentation (C/F/S) process using MO extracted in a saline solution of potassium chloride (KCl-1M) as coagulant to determine best dosage; 2) nanofiltration process using NF-90 and NF-270 membranes, with slightly different characteristics. A 5 bar working pressure was applied. Physical, chemical (color, turbidity and pH) and microbiological (cyanobacterial cells count and microcystin concentration) parameters were analyzed in all samples. Current study shows that, as a natural coagulant, MO seeds provided satisfactory results in M. protocystis, color and turbidity removal and did not cause cell lysis. NF completely removed cyanobacterial cells and microcystins (100%) from M. protocystis (within the quantification limits). Results show that C/F/S+NF sequence is a safe barrier against M.protocystis and microcystins in drinking water.