混凝预处理对膜蒸馏深度处理焦化废水生化出水的影响

In this study, a laboratory-scale membrane distillation (MD) system was developed for advanced treatment of biologically treated coking wastewater (BTCW), while the effect of pre-coagulation on the system performance was also investigated. Results showed that pre-coagulation of BTCW with poly-aluminum chloride (PACl) significantly reduced the solids and organic loadings of BTCW prior to membrane distillation. These in turn significantly reduce the propensity of membrane fouling. It was confirmed by ultraviolet-visible (UV-vis) scan and excitation emission matrix (EEM) fluorescence spectra that the low molecular weight aromatic substances were dominant in the organic residuals. It was also found that addition of polyacrylamide (PAM) as a coagulant aid could further improve the removal of COD and color, but it lead to a severer membrane fouling. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and energy-dispersive spectrometer (EDS) analyses further revealed that pre-coagulation could prevent the formation of calcium carbonate on the membrane surface, whereas the addition of PAM facilitated the accumulation of aggregates on membrane surface, leading to serious membrane fouling.