The Study On Nitration Characteristic Of High Concentration Ammonia Nitrogen In A Submerged Membrane Bioreactor

The thesis takes the landfill leachate effluent from compound reactor, UASB and MF ,as the experimental object and uses the submerged membrane bioreactor (SMBR) to study the nitration characteristic of high concentration ammonia nitrogen, the sludge characteristic in the reactor, the decline regularity and the renewal measures of membrane flux. Experimental results show as follows.By the study on nitration characteristic of high concentration ammonia nitrogen in a submerged membrane bioreactor in different loading and different HRT, we can draw some conclusions. In the reactor which autotrophic bacteria was the dominant species, When the influent concentration of Ammonia-N was between 241.9 mg/L and 1987mg/L, the Ammonia-N removal rate of SMBR was between 44.7% and 99.7% and the corresponding effluent concentration was between 1.9 mg/L and 978.1mg/L. When Ammonia-N loading rate was less than 1.5kgNH3-N/(m³ ·d), Ammonia-N removal rate of SMBR was more than 80% on the whole. At the same time, the SMBR had good ability to resist the loading impact and it could keep higher Ammonia-N removal rate at the fixed time. The loading rate was more 3.75-15 times than that of the nitration segment of activated sludge and common biological fluidized bed, indicating that SMBR had better nitrifying capacity. Ammonia-N removal rate of SMBR hadn't evident difference in the same loading rate but different HRT such as 12h, 18h and 24h.During the running time, the nitration sludge concentration rose from 3.87g/L to 7.29g/L, VSS/SS gradually declined from 0.8 to about 0.75 and the sludge volume index also declined from 175mL/g to 50mL/g and become stabilization, which indicated that the sludge acclimatize itself to the surrounding of lacking of biodegradable organic substances but having high concentration ammonia nitrogen. Tiny colloids and high molecular-weight viscous substances of the sludge were the preponderant contaminations of membrane during filtrating. The membrane fouling resistance was mainlycompleted of polarization layer resistance and external fouling resistance with the distribution tests of resistance, and the sums of the two took over 90% of total fouling resistance. The specific cake resistance of sludge was 10¹⁴¹0¹⁶ m/kg and the cake compressibility of the sludge was more than 0.75 on the whole, indicating that the sludge of SMBR was filtrated difficultly but compressed easily. The membrane would be polluted on different level during the running process. HRT had more effect on the membrane flux decline velocity during the running time. Comparing HRT of 12h, 18h and 24h , the greatest membrane flux decline velocity happened in HRT of 12h. In the experiment, I used several methods to recover the membrane flux after the membrane polluted. The effect of chemic membrane washing was better than that of physic membrane washing. When cleaning out the membrane, the recovery of the membrane flux was limited and it was just about 35% in the experiment by hydraulic ways and 20% by empty aerating. The effect of oxidative way of NaClO was better than that of acid and alkali washing in the chemic methods. The contact time had influence on the effect of cleanout.