Enhanced treatment of high-COD MDF wastewater using hybrid coagulation-membrane distillation process: Coagulation efficiency and membrane performance

Abstract

The treatment of medium density fiberboard (MDF) wastewater presents a significant challenge due to its complex composition and elevated temperature, which limit the effectiveness of conventional treatment methods. This study investigates the applicability of a hybrid coagulation-membrane distillation (MD) process for the treatment of high-strength MDF wastewater. Poly-aluminum chloride hydroxide (PACS) was employed as a pretreatment to reduce fouling potential, followed by MD using a hydrophobic polytetrafluoroethylene (PTFE) membrane operated at different feed temperatures (50-80 degrees C). The optimal operating condition was obtained at a feed temperature of 50 degrees C, where the PTFE membrane exhibited a stable flux of 9.45 L/m(2).h and achieved a COD removal efficiency of 95.02%, together with over 95% reduction of conductivity, turbidity, color, and total suspended solids. Increasing feed temperature enhanced membrane flux but led to membrane wetting and deterioration of permeate quality. Membrane wetting was mainly attributed to elevated operating temperature, organic fouling, and inorganic scaling, as confirmed by contact angle measurements, scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) analyses. The results demonstrate that MD, when combined with effective pretreatment, is a promising and energy-efficient approach for MDF wastewater treatment, provided that operating conditions are carefully optimized to minimize membrane wetting.