Study On The Nitrogen Removal Performance Of MBBR With New Biocarriers And Its Influencing Factors

With the increasing discharge of domestic sewage and industrial wastewater,a large number of nitrogen-containing wastewater enters the natural environment,causing adverse consequences such as eutrophication,aquatic organism poisoning and reduction of the value of water resources,therefore,nitrogen removal of wastewater is imminent.Moving bed biofilm reactor?MBBR?has become an effective method for nitrogen removal due to its flexible operation and long sludge age.Based on the denitrification of MBBR process,the influencing factors of simultaneous nitrification and denitrification?SND?performance of MBBR were studied by adjusting the operation conditions,so as to improve the denitrification performance of MBBR.Firstly,mobile bed biofilm reactors with different filling rates?10%,20%and30%?were used to treat domestic sewage.Cubic polyurethane sponges with a side length of 15 mm were used as biofilm carriers.The results showed that the removal rates of total organic carbon?TOC?and ammonia nitrogen?NH₄⁺-N?in three reactors with different filling rates were not significantly different.However,the removal rates of total nitrogen?TN?and the performance of SND increased with the increase of filling rate.The removal rates of TN by MBBR reactor with filling rate of 10%,20%and 30%were 77.2±7.4%,85.5±9.3%and 86.7±9.9%,respectively.Accordingly,the performance of SND was 85.5±8.7%,91.3±9.4%and 93.3±10.2%.In addition,in the reactor with 20%filling rate,the attached biomass on the polyurethane sponge carriers was the largest,followed by the reactor with 10%and 30%filling fraction.Subsequently,novel biofilm carriers were prepared from zeolite powder and polyurethane sponge to improve the denitrification efficiency of MBBR process.The results showed that there was no significant difference between the reactor with polyurethane sponges as fillers and the reactor with new carriers as fillers in the removal of TOC and NH₄⁺-N under the same conditions,but the removal rate of TN and SND performance of the new carriers were about 10%higher than those of polyurethane sponge carriers.The removal rates of TN by the new carriers were 84.2±4.8%and 75.1±6.8%respectively,and the corresponding SND performance were90.7±4.1%and 81.7±6.5%respectively.In addition,the biomass attached to the new carriers?0.470±0.131 g/g carrier?was 1.3 times that of the polyurethane sponge carriers?0.355±0.099 g/g carrier?.Through microelectrode measurements and microbial community analysis,it was found that there were more denitrifying bacteria on the new carriers,which could improve the SND performance of the system.Finally,three typical PPCPs?sulfadiazine,ibuprofen and carbamazepine?were selected to study the inhibition of MBBR system on nitrogen removal performance and the removal performance of MBBR process on pharmaceutical pollutants.The results showed that the MBBR reactors had the highest removal rate of ibuprofen?74.9±8.8%?,followed by carbamazepine?61.1±8.8%?and sulfadiazine?42.3±10.2%?.Compared with the reactor without any PPCPs,the removal rates of TN decreased by 21%,30%and 42%in the reactor with sulfadiazine,ibuprofen and carbamazepine,and the performance of SND decreased by 17%,24%and 31%respectively.It can be seen that the most inhibitory drug to the denitrification performance of MBBR was carbamazepine,followed by ibuprofen and sulfadiazine.