Treatment of surface water using hybrid processes — adsorption on PAC and ultrafiltration

Studies were performed to determine the effect of the presence of powdered activated carbon (PAC) on ultrafiltration (UF) process performance. The influence of PAC addition to the feed on permeate flux in terms of flux decline and the possibilities of membrane cleaning during backwashing were investigated. The effectiveness of the removal of organic contaminants from the Miedwie Lake water during UF and hybrid processes of adsorption on PAC–ultrafiltration (PAC/UF) were determined. Fourier transform infrared (FTIR) spectroscopy was applied in order to examine the character of membrane foulants. Polyacrylonitrile (PAN) membranes formed by the phase inversion technique were used in the UF experiments. Commercial PAC CWZ 30 was applied as the adsorbent. PAC dosage was equal to 100 mg PAC l!1. The process was carried out in the cross-flow system. The experiments were performed at two different pH values (8.7 and 6.5) of the treated water. It was found that the combination of UF and adsorption on PAC was more effective in organics removal than UF alone. The treatment was more efficient at pH 8.7 than at pH 6.5. At both pH values, no significant effect of PAC addition to the feed on the permeate flux was observed. On the basis of the FTIR spectra, it was found that the foulants of the PAN membrane present in Miedwie Lake water were primarily silicates.

1. The obtained results show that the application of a PAC/UF system is very effective in the removal of organic substances from natural waters. 2. The role of PAC suspended in a feed in the PAC/UF system is the adsorption of low molecular organic compounds, which cannot be removed by UF alone. 3. At both pH values (6.5 and 8.7), no significant effect of the presence of PAC in the concentration of 100 mg l!1 on the permeate flux or backwash efficiency was observed. 4. The effectiveness of organics removal during UF alone was lower at pH 6.5 than at pH 8.7. The treatment effects obtained in PAC/UF hybrid processes were similar at both pH values. 5. On the basis of FTIR spectra, it was found that the foulants of the PAN membrane present in Miedwie Lake water were primarily silicates.