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.