Removal of humic acids by the process of flocculation ultrafiltration

Abstract

For the removal of humic acid (HA) from water, flocculation using polyaluminum chloride (PAC) and a polyelectrolyte (PE) aid was investigated. TOC removal corresponding to the HA removal was 88.5-90.4* by coagulation with PAC and 90.3-91.1* by flocculation with PAC and PE at a controlled pH of 6.8-7.2. Three flat sheet membranes of 10 4 , 10 5 , and 10 6 molecular weight cut off (MWCO) were used for the investigation of the effect of ultrafiltration (UF) on HA removal. The solution of HA and the mixed solution containing floes were applied to the UF module under the conditions of input pressure 0.2 MPa and the circulation flow rate of 250 ml/min.. TOC removals for a sample solution of 50 mg/1 of HA increased from 78.3% to 93.8% with decreasing the MWCO from 10 6 to 10 4 . For the mixed HA solution containing PAC floes, TOC removal by the 10 6 MWCO membrane was 90.5%. For the mixed solution of HA. PAC and PE, TOC removal by 10 6 , 10 5 , 10 4 MWCO membranes was 90.5%. 92.5%. 95%.4. respectively. Continuous HA removal was investigated in a laboratory scale plant using the processes of flocculation-sedimentation and flocculation-UF. The HA removals were evaluated by the indicators of TOC removal and E26O (absorbance at 260 nm) removal. The flocculation-sedimentation process gave 89.5% removal in E 260 and 88.9% removal in TOC. The flocculation-UF process gave 91.9% removal in E 260 and 89.6% removal in TOC, at a permeation flux of 249.2 l/h.m 2 using the 10 6 MWCO membrane.