Jar tests
Coagulation performance was evaluated using a programmable TA6-1 jar test apparatus (Wuhan, China). MHC or conventional coagulants were added to raw water, mixed rapidly at 250 rpm for 1.5 min, mixed slowly at 50 rpm for 20 min, and settled for 30 min with applied magnetic field. For MSC, Fe3O4 and PFC were added before stirring, and PAM was added after rapid mixing. During the settling period, samples were collected from 2 cm below the water surface at regular intervals. Turbidity was analyzed, and then samples were filtered through 0.22 μm nylon membrane filters before analyzing TP, NO3--N, UV254, dissolved organic matter (DOM), and N-containing compounds in DOM. The secondary biological effluent was used to explore the coagulation performance, and the synthetic aqueous solution was used to evaluate factors affecting coagulation.
Analytical methods
The morphology and chemical structure of MHC were analyzed by transmission electron microscopy (TEM; Hitachi, H-9000NAR, Tokyo, Japan) and Fourier-transform infrared spectroscopy (FTIR; Nicolet iS50, Madison , USA), respectively. TP, NO3--N, and UV254 were determined by an ultraviolet-visible 1800 spectrophotometer (Shimadzu, Kyoto, Japan). Turbidity was measured by a turbidimeter (2100 N Turbidimeter, Hach, Loveland, USA). To measure DOM and DON concentration and type in the coagulated water by MHC, a Bruker Apex (Madison, USA) ultra Fourier-transform ion cyclotron resonance mass spectrometer (FT-ICR MS) equipped with a 9.4 T superconducting magnet was used. More details are in SI.