The Study On The Characteristics Of The Domestic Wastewater Treatment By Moving Bed Biofilm Reactor

MBBR is a new way of biofilm water treatments, which is got more and more attention for its advantages and characteristics. In this paper, MBBR is choosen for domestic wastewater treatment. Through changes in reaction parameters such as HRT, COD concentration, NH3-N concentration, DO, pH and so on, the removal of carbon and nitrogen is studied under different conditions. The best reactor operating condition which is based on the experimental results of the analysis, is good for the practical application of MBBR reference.In this paper the organics removal capacity of MBBR is studied at the fist. The research and testing results are: (1) There is a good organic removal in MBBR. When COD≤500mg/L, DO=2～4mg/L, HRT =4h, the organic removal can reach 90%. (2) With the increased organic volumetric loading, the removal of COD first increase and then decrease. When organic volumetric loading is 4 kgCOD/m3·d, it is the critical point that the removal rate is got changed. (3)The removal of organic is not only by the capacity of the reactor biological total, but also relates to the thickness of the biofilm. Thin biofilm have higher microbial activity, although the overall biomass is not high, there is still very good removal efficiency.Secondly, the denitrification capacity of MBBR is studied, the results showed that: (1) There is a good denitrification capacity in MBBR. When HRT=8h , DO=2.5mg/L, COD and NH3-N are 500mg/L and 25mg/L ,The removal of TN in MBBR is up to 81%. (2)Increasing the organic loading can inhibit the nitrification reaction. But when the organic loading is reduced, the substrate concentration has reduced too within the reactor, which limits the denitrification reaction; Increasing the NH3-N loading improves the nitrification in MBBR, and the inner NOx-N concentration is increased, but there is the same substrate concentration circumstances in the reactor, so the denitrification capacity is decreased, the ratio of carbon to nitrogen is a reasonable reaction for denitrification of the key. Through the experiments, when C/N=20, the denitrification capacity is highest. (3) The best pH is 6.5～8 in MBBR. As the nitrification processing consumes alkalinity, therefore, in order to maintain the pH response, 3～4g (CaCO₃) alkalinity is needed.