Treatment of river water by a hybrid coagulation and ceramic membrane process

Effects of coagulant dosages and hydraulic retention times (HRTs) on the system performance were examined in a hybrid coagulation and ceramic membrane system. The system performance was evaluated by measuring dissolved organic carbon (DOC), ultraviolet absorbance at 254 nm (UV254), particle counts, and membrane permeate flux. The hybrid system could remove DOC more efficiently than by using coagulation or membrane filtration alone, and the removal percentage by the hybrid system was in the range of 34–54%. UV254 was mainly removed through the coagulation process rather than through the ceramic membrane process. The membrane permeate mainly contained particles with sizes of 2–5 μm. The membrane permeate particle counts decreased with increasing coagulant dosages, while was less affected by HRTs. The membrane permeate flux improved greatly with the inclusion of coagulation pretreatment compared with direct membrane filtration. At the HRT of 10 min, there was no significant difference in the system performance with the PAC (polyaluminium chloride) dosage in the range of 15–25 mg/l. At the PAC dosage of 15 mg/l, the best DOC removal and permeate flux was obtained at the HRT of 5 min.

► Hybrid system removed DOC efficiently and UV254 mainly removed by coagulation.
► Particle counts decreased with increasing PAC dosages and less affected by HRTs.
► The membrane permeate flux improved greatly with the addition of coagulant.