Magnetic coagulants were added under stirring. After stirring for 1 min, the speed was adjusted to 60 rpm for 3 min. A permanent magnet (0.5 T) was then used
to separate magnetic flocs to be examined with SEM. Samples 5 cm below the liquid level were collected and used to determine the contents of chlorophyll-a (Chl-a), turbidity, chemical oxygen demand (COD), total N, and total P