Experimental Study On Suspended Ceramisite Biological Fluidized Reactor Applying To Micro-polluted Water Treatment

Biological Aerated Filter(BAF) plays an important role in biological purification of micro-polluted water in southern region, especially in those polluted mainly by ammonia and organic, due to the high temperature, which greatly contributes to microbial growth in natural water. Currently, ceramisite that have a greater density than water is used as main filer media of BAF, which makes it difficult to rinse thoroughly. Based on current technology, BAF with suspended ceramsite(SCBFR), which combined with suspended contact oxidation process and the characteristics of BAF, was developed to tackle with this problem. Experimental study on the performance of SCBFR in water purification and operational stability, using the water from Liuxi river and Xiaokeng river as raw water. Experiment results were as follows:(1)Small-scale experiment results showed that the start-up cycle of SCBFR was 28 d under the average temperature of 18℃. With gas-water ratio increased, ammonia and nitrite removal rate increased synchronously, but little influence did have on the removal of organic. Gas-water ratio of 0.4~0.6:1 was used, as the average ammonia concentration of raw water was less than 3.5 mg/L. The nitrification efficiency and operational stability were influenced by filtration rate. Nitrification efficiency decreases by about 10%, when the filtration rate reached 16 mg/L. Use of small particle media can improve biochemical efficiency, but appropriately had to shorten the backwash cycle.(2)SCBFR combined with conventional process has a good effect on micro-polluted water treatment, and the process had a high efficiency and operated steady. In rainless season, with the conditions of 0.4~0.6:1 gas-water ratio and 8~12m/h filtration rate, the final effluent of the process met the "drinking water health standards"(GB5749-2006) standards, when the average concentrations of ammonia, CODMn and nitrite were3.06 mg/L、3.5 mg/L、0.289 mg/L respectively. However, for that the influent of rainless season was of low turbidity, it still needed dosing clay solution as aid coagulant to eliminate floating problems that happened in the settling tank. In wet season, with the conditions of 0.2~0.6:1 gas-water ratio and 8~16m/h filtration rate, the final effluent met the "drinking water health standards"(GB5749-2006) standards, when the average ammonia, CODMn, nitrite and turbidity were 1.89 mg/L, 2.03 mg/L, 0.277 mg/L, 41.5NTU respectively. Treatment test of raw water separately by the conventional process showed that most of ammonia and nitrite were removed by SCBFR, while CODMn and turbidity were mainly removed by the conventional process.(3)Switch raw water to test on micro-polluted water treatment efficiency of SCBFR and conventional process. Experimental results showed that due to sudden increase in the concentration of ammonia nitrogen, CODMn and other environmental factors, time was needed to restore to the original treatment efficiency of the whole process. 34 h was needed to have ammonia of the effluent met standards GB5749-2006, as water pollution is more serious in rainless season, at the same time, ammonia removal efficiency of SCBFR reached 88%.There was a synchronized condition for the removal of ammonia and nitrite. 26 h was needed to meet standards for nitrite, which accumulated up in the beginning. CODMn mutation had little effect for SCBFR, thus the effluent of the whole process had 100% compliance. Removal efficiency of CODMn showed slight increase since the available substrate concentration can be increased. For that the water pollution in wet period is relatively light, 17 h and 18 h were needed for ammonia and nitrite of the effluent to meet standards. It was showed that SCBFR as pretreatment has good resistance to sudden changes in water quality.