For Chl-a measurement, 20 mL of the test solution was filtered through a 0.45-μm microporous membrane. The membrane was dissolved completely in 8 mL of 90 % acetone solution and centrifuged at a speed of 3,500 rpm for 10 min. The supernatant was collected to determine the absorbance at 750, 663, 645, and 630 nm.