Study Of Operational Conditions And Modes On Water Treatment Process Of Ultrafiltration

The membrane technology is called 'the 21st century water treatment technology'. Concerning the insurance of the water quality, controlling membrane fouling is the key to stable effluent and lasting performance, which have become the core of the research. Only if the membrane fouling has been controlled effectively, can operation and management cost of the membrane separation technology be reduced, and a wide application can be achieved. In the view of operational conditions and modes, following factors which effect on water treatment process of ultrafiltration were considered in the paper such as recovery, backwashing intervals, backwashing pressure, cleaning method as well as operational modes of constant-flux and constant-current. At last influence of corresponding ultrafiltration process on the membrane mean pore size and pore density was evaluated by the model of membrane structure parameters. The main operating conditions were obtained affecting the membrane structure parameters, operational conditions of ultrafiltration process were optimized. Following conclusions can be made:(1) After filtered by polysulfone ultrafiltration membrane (molecular weight cut-off was 100kDa), 80% of organics were removed from raw water. Meanwhile membrane fouling was mainly surface fouling.(2) The best way of cleaning membrane online was '90s of backwashing following with 30s of surface washing.' Effect of alone cleaning by backwashing or surface washing was not better than effect of the hybrid washing. Surface washing before backwashing can not effectively recover the flux while surface washing after backwashing can achieve ideal effect. Under the best way of cleaning condition, cleaning intervals had important effects on alleviating the membrane fouling, especially in the latter part of membrane filtration. Increasing backwashing pressure and reducing cleaning intervals may play a significant role in decreasing transmembrane pressure and controlling membrane fouling.(3) The best way for renewing membrane flux was chemical cleaning incorporated with surface cleaning, and backwashing and surface washing. Membrane flux recovery can be achieved 98.8%.(4) Through membrane resistance test in different operational modes, it can be found that membrane resistance under constant-flux mode was smaller than membrane resistance under constant-pressure. In other words, in the membrane filtration process, constant-flux can reduce membrane fouling effectively, enhance membrane filtration capacity in the greatest degree.(5) The process of ultrafiltration for different operational modes and operational conditions by ultrafiltration membrane parameters model was simulated, and the model can well simulate process of ultrafiltration for constant-flux and constant-pressure. Coefficient of model further showed: the best way of cleaning membrane online was '90s of backwashing following with 30s of surface washing.' In the process of constant-flux, increasing backwashing pressure and reducing cleaning intervals may play an importance role in decreasing transmembrane pressure and controlling membrane fouling.