Study On Moving-bed Biofilm Reactor(MBBR)and Its Denitrification

With the progress of the society and the improvement of living standards, the requirements of people for life and the environment is higher and higher, but water pollution influences environment seriously, which influences utilization of fresh water resource, therefore, it is an urgent problem to research how to reduce the pollution level of water. The main problem of water pollution is eutrophication, which results from excessive discharge of nitrogen and phosphorus. Many sewage treatment plants which were built in last century could not meet the requirements of nitrogen and phosphorus in the new discharge standards. A good way of increasing the handling ability is to add suspending padding in old treatment plant to form Moving-bed Biofilm (MBBR). Treatment effect of MBBR with BioMTM in each mode of operation was researched and influencing factors were analysed. The best operational condition was acquired so as to offer reference to engineering practice.The influencing factor of oxygen transmission efficiency in water was researched.The appropriate rate of filler was40%and the aeration quantity was about0.2m3/h.Inoculation method and natural biofilm formation method were used in two equipments in biofilm formation experience and the results proved the existence of critical mass, that was, the seed sludge is not necessary to add in the start-up of bioflim formation and add seed sludge could not accelerate biofilm reactor start-up.Sludge in the domestic sewage could satisfy the demand of biofilm start-up.The impact of dissolved oxygen (DO), hydraulic retention time (HRT), pH and other factors on the MBBR removal of organic matter and ammonia nitrogen were researched. According to these, four operation conditions of continuous flow single stage MBBR were determined and the removal efficiency of organic matter, total phosphorus and the variation of different forms nitrogen in the four conditions were compared and analysed. Test result showed that continuous flow single stage MBBR had good removal efficiency to organic matter and ammonia nitrogen and had certain removal efficiency of TN in appropriate condition. Simultaneous nitrification-denitrification (SND) occurred in the reactor. And TN could be removed. The best operation condition of continuous flow single stage MBBR was determined.Aimed at the removal efficiency of total nitrogen in the continuous flow single stage MBBR was low, an improved method that running the single-stage MBBR in sequencing batch in the same DO and HRT was proposed. From the result, sequencing batch could increased the removal efficiency of total nitrogen, and the removal efficiency of organic matter, ammonia nitrogen and total phosphorus were similar to continuous flow condition. In order to increase denitrification efficiency of MBBR, design the single-stage MBBR in to two stages, and tested the treatment effect in three operation conditions. The dominant species in the two reactors were different by control the different conditions of the first stage reactor and the second stage reactor. Organic matter was removed mainly in the first stage reactor and Simultaneous nitrification-denitrification almost did not occur. Ammonia nitrogen and total nitrogen occurred in the second stage reactor and simultaneous nitrification-denitrification was obvious. The removal efficiency of total nitrogen in the best operation condition was better than that in continuous flow and sequence batch single stage MBBR. Using the reactor to treat actual domestic sewage in the best operation condition good treatment effect was acquired.