Impact of PAC Type and Water pH on Removal of Microcystin-LR and Saxitoxin

The projection focused on the removal of microcystin-LR (MC-LR) and saxitoxin (STX) with different powdered activated carbon (PAC) sources in distilled and raw source water. Wood-lignite-based (WL) PAC adsorbed more MC-LR and STX than the bituminous coal-based (BC). For 0.3 µg/LSTX in distilled water, WL adsorbed more STX than with BC. Across all pH and concentration combinations, WL adsorbed more MC-LR in distilled water and raw surface water than BC. For instance, when 0.3 µg/L STX was present with 1.6 µg/L MC-LR at pH 6, removal was 31% and 62%, and increased to 49% and 65%, respectively at pH 8. The increased removal was attributed to competition with natural organic matter, which was depicted as a 19% removal at pH 6 versus 4% removal at pH 8. When both toxins were present at 1.6 mg/m3, removal when water pH of 8 was 61% for STX and 72% for MC-LR.