Efficiency of the hybrid coagulation–ultrafiltration water treatment process with the use of immersed hollow-fiber membranes

The changes of concentration of several chemical substances existing in the surface water from the Czarna Przemsza River were examined during the ultrafiltration process carried out with 0.03 m PVDF immersed hollowfiber membranes. The volumetric permeate flux was constant (5.7×10−6 m3/m2·s). The tests were carried out in three ways: ultrafiltration process only and hybrid processes connecting coagulation (with the use of FeCl3 or Fe2(SO4)3) with ultrafiltration. The value of pH in the raw water was about 8.3–8.4. The results of statistical tests show a significant difference between the concentrations of turbidity, total iron, oxygen consumption, COD and absorbance UV (254 nm) during the ultrafiltration process. After the use of both FeCl3 and Fe2(SO4)3 coagulants, the retention coefficients of turbidity, oxygen consumption and absorbance increased. A minor decline of the retention coefficient of total iron, probably connected with the use of iron coagulants, was observed.