Efficiency of Membrane Ultrafiltration in Water Treatment Plant Jasná

Abstract

Ultrafiltration (UF) is a membrane separation process by which the particles of mechanical nature are removed from the water. Thanks to the pore diameter that are the order of tenths nm and the material, constructional and chemical properties of UF membranes, this technology represents the final solution for a secured protection against the turbidity that is caused by content of non-soluble and colloid particles of organic and inorganic origin, bacteria and the majority of viruses. Ultrafiltration was investigated within the pilot-plant tests at the WTP Jasná during the treatment of surface water originating from the water source Zadná voda. Water treatment is in this locality focused on turbidity that is caused by storm rainfalls and snow thawing. Fully automated ultrafiltration equipment with the membrane modul UA-640 (Microdyn-Nadir) was used. On the base of filtration cycles, the effectiveness of membraned technology was evaluated. Water was supplied to the UF-device by the pump, so the UF-flow rate was invariably maintained at the 600 L/h Period of filtration cycle was 30 minutes. Following the end of the cycle, washing of membrane by using the back-flushing by water and air was applied. Filtered water accumulated in the tank was used for back-flushing while the air was supplied by the air-pump connected to the device. Any way of washing of the membrane did last for 30 seconds. On the base of filtration cycles, the effectiveness of membraned technology was evaluated. Turbidity removal is the major issue at the WTP Jasná. Limit for turbidity 5 NTU is set by Decree No. 247/2007 Col. Measuring data provided that the turbidity level of water treated by using the ultrafiltration device are compliant with the legal limit for drinking water. By using the ultrafiltration, the decrease by 76,1% has been reached in the first experiment (average turbidity in raw water 1,55 NTU). The efficiency of turbidity removal was 95,2% that was reached by ultrafiltration of water with a higher level of turbidity (average turbidity in raw water 8 NTU). High effectiveness of ultrafiltration was reached also with the water with the turbidity 37 NTU. In all of the three experiments, the turbidity of treated water ranged between 0,37 - 0,38 NTU.