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.