Study on Biofilm Formation, Start-up and Nitrogen and Phosphorous Removal Efficiency with Filtration Intermittent-aeration Biofilm Reactor
|School||Huazhong University of Science and Technology|
|Keywords||FIBR Nitrogen and phosphorus removal Integrated hybrid reactor Suspend media Biofilm|
In order to solve the conflict between nitrogen and phosphorus removal on Sludge Retention Time, based on the developed technology—continuous-flow integrated biological reactor (CIBR), combining it with suspend carrier and filtration process with uni-form media, this study developed innovative Filtration Intermittent-aeration Biofilm Reactor(FIBR). FIBR futher optimizes CIBR and solve the problem encountered in the treatment of in municipal wastewater in south China, especially in Guangdong province. FIBR occupies less space, consume less energy, and cost less money. In this laboratory trial, we research on influential factors, treatment efficiency during the start-up of FIBR and investigate different working conditions in order to achieve optimal removal efficiency and stability.The Biofilm-activated sludge reaction zone, settling zone three-phase separator and filtration ozone were integrated in FIBR. Using two different types of aeration system and carriers to cultivate biofilm and start up FIBR,it can be inferred that aeration means, traits of carriers and characteristic of suspended sludge are crucial factors. The rate of biofilm accumulation suggests that aeration system with bubbles ranging form 1mm to 4mm together with carrier with rough surface, attached biomass grow with higher speed. Accordingly the total biomass can be one time higher than traditional activated sludge system in30 days, amounting to 5817.99mg/L。Besides, the diameter of the bubbles is inpositive relation with the impactness of attached biofil’s structure. Transmission of oxygen and organism are both affected by thickness negatively. The rate of attached biomass formation is supposed to be in positive relation with SVI. Biofilm can refrain?’s growing effectively and the settling property of suspend pHase can also influence the biofim. FIBR’s second start-up was carried out under the operating condition 2h-aeration- 1h-settling, COD, NH3-N and TP of the effluent are12.93mg/L, 8.59mg/L and 0.71mg/L, the average removal rate are 56.70%, 22.85% and 20.07% respectively, much higher than the first time. During the period of start-up, removal efficiency is closely related to biomass accumulation, thickness of biofilm, aeration intensity and other factors.By comparison of for different operating conditions, 2-3h aeration, 1h stirring and 1h settling period is highly recommended for FIBR. In order to achieve high removal efficiency and stability, aeration rate should be kept above 0.50. Even SRT of FIBR is 10d, rate of phosphorus removal is promoted but nitrogen removal is not affected. Based on comparison on demand time for aeration, stirring and removal efficiency of COD, NH3-N, TN, TP between FIBR and CIBR, aeration is sugguested as the most crucial factor; Denitrifying bacteria, which probably survives in the inner layers, shorten the denitrogen time. In all, in oder to achieve both nitrogen and phosphorous removal, time for every step shoud be kept reasonable.