Study On High Concentration Activated Carbon-Ultrafiltration Process For Slightly Polluted Water

The membrane filtration technology in water treatment shows a lot of advantages. The membrane filtration methods can be divided into high pressure and low voltage membrane method based on the pressure in the process of using it. The low voltage membrane has a high attention by people because of its'low price, low energy consumption, high efficiency, and easy to operate. The Low voltage membrane has microfiltration and ultrafiltration membrane, but microfiltration membrane is difficult to solve completely pathogenic bacteria problem in drinking water, so the ultrafiltration membrane is used more in current drinking water treatment.This paper firstly studies a continuous effluent not washing submerged type UF membrane tank and a periodic reverse-wash of ultrafiltration membrane tank in different oxygen for slightly polluted water treatment effect. The result shows that the best UV₂₅₄ and TOC removal efficiencies of two tanks in 180L/h for oxygen are respectively achieved 80% and 68% about. In 200L/h for oxygen UV₃₅₀ has the best removal efficiency which can achieve 65%; periodic operation couple with aeration can mostly alleviate membrane pollution and the growth of transmembrane pressure. But the ammonia nitrogen removal efficiencies of the two tanks are below 5%, therefore immersion type ultrafiltration membrane tanks alone are not suitable for the treatment of high ammonia nitrogen slightly polluted water.In one ultrafiltration membrane tank which is backwashing and maintaining the water temperature of about 20 oC doses 30 g/L of PAC in the tank. The result shows that the tank needs 58 days of the start-up time for the process of removing ammonia nitrogen, and the removal efficiency of the system can finally achieve 98% above. The system can reach maximum of 4.66 mg/L in the 38th days. The removal rate of total nitrogen in the tank increases as time runs. The average removal efficiencies of UV₂₅₄,UV₃₅₀ and TOC are respectively above 95%,97% and 70.41%.In the tank the speed of running water suction pump is changed in first 35 days, and the water in the fluxes of 3L/h, 4.5 L/h and 6.0 L/h each operates 6 hours. The results show that: the turbidity removal efficiency in the three fluxes does not have difference; In the lowest flux of 3L/h ,it has the best efficiencies for UV₂₅₄,UV₃₅₀ and TOC.And in flux 4.5L/h it has the best removal efficiency. Under the flux of 4.5L/h the water nitrite content can reach 3.9521 mg/L. In flux of 3.0 L/h it has the best removal rates for nitrate and total nitrogen.In the tank of PAC concentration 30g/L for UF the effluent flux is controlled for 6.0 L/h in the first 41 days, and it each operates a day under three different reverse-wash water which is 2.5 times, 5 times and 10 times of the effluent .The results show that when reverse-wash water is 5 times ,the reactor has the best removal efficiency which is 83.28%,and right now, ammonia nitrogen turns into the highest content of nitrogen, too. When reverse-wash water is 7.5 times, the nitrate has the best remove effect. The total nitrogen removal rates under three reverse-wash are all below 26%, and the reverse-wash is larger, the nitrogen removal efficiency is poorer.When the tank dosed into 30g/L PAC, the start-up time of ammonia nitrogen removal process is slower, so PAC concentration in the tank is changed to 50 g/L and maintains the system to operate in low temperature. It shows that it needs only 46 days of the start-up time for the process of removing ammonia nitrogen. The system can reach maximum of 4.767 mg/L in the 28th days. The removal rate of total nitrogen can reach 32.15% in the 46th days. In the 34 days after system start-up, it has a good removal efficiency for turbidity, and has a decrease for the removal rate of UV₂₅₄ and UV₃₅₀ but the reduction is not much. The removal rate of TOC is to be stable. The average removal rate for NH₃-N is 97.498%, and NH₃-N can transform NH₃-N to NO₂^--N, which can completely change into NO₃^--N. The effluent of NO₃^--N has a certain down trend. The system on the total nitrogen removal effect has a trend of increase.