Preparation Of Nitrifying Enhanced Suspended Carriers And Their Wastewater Treatment Performance

In recent years,the integrated floating fixed-film activated sludge?IFFAS?process has attracted widespread attention on biological nitrogen removal,of which the properties of suspended biofilm carriers are crucial during nitrogen removal.Nowadays,the conventional suspended biofilm carriers?made of polyethylene?PE?or polypropylene?PP??usually have the drawbacks of poor biocompatibility,weak biofilm formation,low biomass and biological activity,and lacking of functional design.In this study,nitrifying enhanced suspended biofilm carriers were prepared through surface hydrophilic modification,electrophilic modification and nitrification-enhancing functional design,and demonstrated good biocompatibility and ammonia adsorption capacity.Then,the nitrification,total nitrogen removal performance and microbial mechanism of IFFAS process with this novel carriers were studied.To further improve the nitrogen removal efficiency of IFFAS process,the relevant operation conditions were explored and optimized.The main conclusions were shown as follows:?1?The nitrifying enhanced suspended biofilm carriers were made of PP,polyquaternium-10,Fe₂O₃,clinoptilolite and talc by blending and screw extrusion technology.The experimental results showed that the zeta potential on the surface of novel carriers was increased from-38.6mV to 11.7±1.1 mV,and their surface contact angles decreased from 95.1°to 76.7°after modification,which showed that both the electrophilicity and hydrophilicity were significantly enhanced,and hydrophilicity remarkably improved with increasing clinoptilolite content of carriers.In addition,the novel carriers obtained a certain degree of ammonia nitrogen adsorption capacity by the addition of clinoptilolite.?2?The study of enhancing nitrification in sewage using nitrifying enhanced carriers showed that compared with activated sludge reactor?R1?and IFFAS reactor with conventional carriers?R2?,the IFFAS reactors with this novel carriers performed higher nitrification efficiency under different influent NH₄⁺-N concentrations,dissolved oxygen?DO?and hydraulic retention times?HRT?levels.When the DO concentration and HRT were controlled at 2.5±0.5 mg/L and 4 h,respectively,the nitrification efficiency of IFFAS reactors with novel carriers increased by 18%and 15%compared to R1 and R2.Besides,the high throughput sequencing results showed that the biofilm of novel carriers had higher microbial diversity,and its abundance of functional nitrifiers increased by nearly 4.39%and 4.51%at the phylum?Nitrospirae?and order?Nitrospirales?taxonomic level,respectively,which enhanced the nitrification performance and shock resistance in this system.?3?The nitrogen removal performance by simultaneous nitrification and denitrification?SND?in IFFAS process with nitrifying enhanced carriers showed that comparing with activated sludge reactor?R1?and IFFAS reactor with conventional carriers?R2?,the IFFAS reactors with this novel carriers demonstrated better nitrogen removal performance,and it was also found that the lower DO concentration and higher C/N were more conducive to the realization of SND.When the DO concentration was about 1 mg/L and C/N ratio was not less than 5 in the system,the total nitrogen removal efficiency of IFFAS reactors with novel carriers increased by 9%and 6%compared to R1 and R2,respectively.