| Continued-flow Integrated Biological Reactor is the research result of "Ecological treatment technology and demonstration of bio / city sewage" project during Tenth-Five plan, It can achieve Simultaneous nitrogen and phosphorus removal, and nitrification and denitrification of activated sludge is the main way for nitrogen removal. however, as a floc structure material, activated sludge, in addition to nitrification and denitrification for nitrogen removal, also can remove the ammonia nitrogen in wastewater by Biosorption. and it can not be neglected for the mass balance of total nitrogen in CIBR. But research on the ammonia adsorption performance, and the mechanism, nitrogen balance analysis is very rare in sewage management system of activated sludge.In this paper, Adsorption performance of activated sludge(aerobic and anoxic) cultivated in CIBR was investigated through dynamic and static experiments. and the effects of various factors(p H, initial ammonia concentration, sludge concentration, temperature and salinity) on the adsorption, the mechanism of adsorption of activated sludge was fitted by kinetic and isotherm model, moreover, the desorption experiment was also carried on to determine the final adsorption rate on activated sludge, finally,the mass balance calculation of the CIBR reaction system was conducted so that we can understand the nitrogen loss rate in the water, to provide some data support for the optimization design and operation of reaction system. The main results are as follows:(1) The dynamic study results showed that ammonia nitrogen can be adsorbed on activated sludge for aerobic and anoxic, but the degree of adsorption was different for two kinds of sludge; however, for the effluent nitrate nitrogen(NOX-N), the adsorption is not obvious and can be ignored.(2) Static experimental results show that the initial ammonia concentration of aerobic and anoxic sludge is one of the important factors to influence biosorption, and the adsorption capacity of activated sludge increases with the concentration, respectively for 0.21-1.70mg/g 0.21-1.14mg/g; and when the initial ammonia concentration reached 70 mg /L, the adsorption capacity of aerobic sludge is significantly higher than anoxic sludge;besides, p H also affects the adsorption capacity of ammonia nitrogen, with p H from 3 to 8, the adsorption capacity increased gradually,and reach to maximum at 8, but the adsorption capacity start to decrease with p H increasing, and it has similar results with the increasing of sludge concentration from 3000 to 7000 mg/L. but biosorption was less affected within normal temperature range(20 to 30 ?),when the temperature is increased to 40 ?, the adsorption of aerobic and anoxic sludge is difficult to stable, and the capacity is less. In addition, content of salt(Na Cl) will make an influent on biosorption, and the capacity will decrease with the content increasing, when the content of salt(Na Cl) reached 30 g / L, aerobic and anoxic sludge has no adsorption.(3) kinetics and isothermal model fitting results showed that the ammonia nitrogen adsorption for activated sludge is a pseudo second order kinetic process, chemical process(ion exchange and electrostatic attraction) is the main influencing factors, and the isotherm fitting results are close, aerobic sludge can be well fitted with the model of Frendliuch, and the Langmuir model for anoxic sludge. And desorption experiments have shown that the anoxic sludge can be more easily desorbed, average desorption rate is about 90%, while aerobic sludge is relatively difficult, the average desorption rate is only 60%;(4) The mass balance analysis results of nitrogen in CIBR system showed that, biosorption removal rate of activated sludge accounted for the total nitrogen is about 9.56%, and it should not be neglected in the mass balance accounting, otherwise it will cause big error, and the main factors that affect total nitrogen removal rate is the denitrification rate in the system. |
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