The Application Of Immersion Combined Membrane Process For Drinking Water Treatment

The treatment effect and influence factors to micro polluted raw water were researched by combining coagulation-biological activated carbon (BAC)-ultra filter craft. The movement conditions of combined craft, treatment effect, the pollution and control of ultra filter, and the action of biology in this system were inspected through experiments.Through analyzing combined craft removal effect to UV₂₅₄ and ammonia nitrogen, the quantity of cycle exchanging BAC 0.6g in this system was determined.Under both situations of with and without biology, the treatment effect to raw water was compared. The experiments indicated: the water outflow turbidity was lower with biological action; there was little removal effect to UV254 with biological action; there was obvious improvement to ammonia nitrogen removal effect with biological action, and after growing well of biological membrane, the removal rate was above 60%, the ammonia nitrogen in water outflow was less than 0.5mg/L. The existing necessity of biological action was shown in the conclusions.Through series experiments, the treatment effect to micro polluted raw water in cycle period was inspected by combined craft. The experiments indicated: when the quality of raw water was turbidity 7.2～68 NTU, UV₂₅₄ 0.108～0.209 cm^-1, ammonia nitrogen 0.41～4.45 mg/L, the quality of water outflow in system was turbidity less than 0.2NTU, UV₂₅₄ less than 0.1 cm^-1, ammonia nitrogen less than 0.5mg/L after successfully cultivating BAC, removal rate 85%. The system to water inflow had certain anti-impact load ability.Through investigating three nitrogen conversion processes in combined craft, the changing growth situation of biological group was being analyzed in this system. The experiments indicated: the removal rate of ammonia nitrogen experienced fast rising stage and steady rising stage, the removal rate of nitrite first dropped to negative value and then rise again, the removal rate of nitrate dropped slowly.Through changing movement parameters in combined craft, their influences to system treatment effect were inspected and the filtration characteristics of ultra filter were analyzed. The final conclusions: there was big influence of changing temperature to removal effect of ammonia nitrogen, 29℃～31.1℃was more proper to hanging membrane in early period; with increasing aeration volume, the removal rate of turbidity and the removal rate of COD_Mn decreased a little, UV₂₅₄ increased a little, the removal rate of ammonia nitrogen experienced decreasing in short period, restoring, and then rising slowly; the changing quantity of coagulation had little effect on removing turbidity and ammonia nitrogen, however, when the quantity of coagulation was zero, there was a little increase of outflow UV₂₅₄, much increase of COD_Mn, and then caused membrane surface pollution which cannot be cleaned. After hanging membrane successfully, the polluting rate of membrane can be slowed down by increasing aeration volume; the application of water-gas counter-wash obviously restored filtration function and had stable effect.The ultra membrane changing function and pollution situation were inspected. The experiments indicated: the membrane pollution was lighter in preliminary stage, the resistance caused by biological action did not increase along with membrane growth on PAC; in later period, the resistance caused by biological action was the main reason for intensifying membrane pollution.The membrane cleaning effect and superficial pollutant nature were determined by SEM and power spectrum analysis to membrane surface. The results indicated that the water-gas counter-wash can remove most loose pollutants on membrane surface; the compact level which can not be washed mainly consisted of coagulation floc. The biological action in combined craft was so obvious.