| The kinds of carrier in bioreactor influence the biomass increase and the performance of enhanced biological nutrient removal to a great extent. Suspended carriers, based on the specific surface area (SSA), can be classified into micro-SSA carrier and apparent-SSA carrier. The micro-SSA carriers which have a large SSA due to the inner holes construction have the enhanced treatment effect just in the early stage of biofilm formation. And the enhanced effect is invisible when the holes are blocked. Although the SSA of the apparent-SSA carrier is small, the real activity of the biofilm is vigorous because of the easy peeling and restoration. The present study, based on the previous research, continued to study the enhanced effect of nutrient removal using large aperture apparent-SSA carrier.The present study still used two parallel SBR reactors just like before. The previous carrier of Mutag Biochip from Germany in one reactor (SBBR) was replaced by carrier of Anoxkaldnes from Sweden. The other reactor (SBR) was run on the condition of suspended sludge with no carrier.The result of biomass growth experiment suggested that the new carrier could increase the biomass effectively. In the artificial sewage study (last for12months) and real sewage study (last for3months), the biomass in SBBR was2.8and2.0times larger than SBR respectively. Although the biomass in the new carrier was less compared with the previous carrier, the effective biomass was larger. Not only the VSS/SS of the new carrier was up to78%, but also the active bacteria proportion was as high as98%while the values in previous carrier were33%and82%respectively.The result of purifying function experiment showed that the utilization rate of oxygen of large aperture apparent-SSA carrier was high under low oxygen concentration. The nutrient removal efficiency of two reactors showed no difference under low NH4+load. But with the increasing load of NH4+, the SBBR reactor showed better and better N-conversion ability of which the ability of nitrification and denitrification increased to27%and15%respectively. In addition, the P removal efficiency of two reactors showed obvious difference under the NH4+load of60mg/L. The P release/uptake performance and the P removal efficiency of the SBBR (88%) were better than the SBR reactor (76%).During the experiment stage, granular sludge was observed in SBR reactor and lasted from the eighth week of beginning to the end of artificial sewage stage. But the granular sludge disappeared after two weeks of the real sewage stage.The condition of strong hydrodynamic shear force,shorter settling times and substrate type has played an active role during the formation of granular in the SBR systems. The sludge floc forms granular sludge with filamentous kernel under the combined effects of these external conditions. Because of weaker mass transfer effect in granular sludge and the water composition change granular sludge gradually disappeared.But the specific reason for their disappearance required more detailed study. In the later stage, the inflow of reactors was changed to real sewage. However, the effluent quality of all reactors deteriorated, especially the NO3-concentration was as high as30mg N/1due to the insufficient carbon source. The effluent quality was immediately becoming better when sodium acetate was added into the reactor during the anoxic stage. The TN and TP removal rates were up to83%and87%respectively which met the "A standard level" while the values in SBR were just74%and75%. When the carbon source in anoxic was changed to real sewage, through inflow adjustment the effluent quality approached the previous level when used sodium acetate. Then the experiment of using the real sewage completely began.The result of the experiment suggests that large aperture apparent-SSA carrier has the enhanced effect of nutrition removal and could be the development direction of carrier. |
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