Influence Of The Surface Hydrophilicity Modified MBBR Carriers On Advanced Nitrogen Removal Of Wastewater Teatment Plant Effluent

When Wastewater Treatment Plant(WWTP) effluent is reused as second water source, its high TN concentration and more than 80% NO3--N ratio is the most serious limiting factor, and NO3--N removal is becoming the key element to be resolved for nitrogen removal. On the basis of long-term WWTP effluent quality investigation, the moving bed biofilm reactors(MBBRs) were used for the residual NO3--N removal, one of the key influencing factor the MBBRs is the type of carriers. The common carriers have polyethylene, polypropylene, polyurethane, but these polymer materials hydrophilic and biological affinity can influence biological biofilm packing, biomass and biological activity in MBBRs and affect treatmenting efficiency of wastewater in MBBRs. Recently, the carriers modified has become a focus.In this paper, study the modified carriers though selection common polyethylene carriers and common polyethylene carriers removal efficiency on the denitrification advanced nitrogen. Three ways of modification are surface liquid phase oxidation, liquid phase oxidation- water bath- acid, liquid phase oxidation- ultrasound- acid. The results show:The polyethylene carriers was modified by liquid phase oxidation, liquid phase oxidation-water bath- acid, liquid-phase oxidation- ultrasound- acid.their static contact angle were reduced by 26.6%, 79.3% and 77.2% than common polyethylene carriers, SEM show the modified polyethylene carriers surface appear long corrosion pits, uneven, surface irregularities and surfaces covered with different shapes of deposits; By XPS and FTIR analysis: the polyethylene carriers were modified by liquid phase oxidation which surface content increased C-O oxygen-containing polar group, the polyethylene carriers were modified by the liquid phase oxidation- water bath- acid, liquid phase oxidation- ultrasound- acid modified which surface was introduced oxygen-containing polar groups for C=O,-C-O-O and –O-C=O. By three modification ways the O/C increased about 11.5%, 15.1%, 30.1% than common carriers.Under the condition of HRT is 6 h, the carriers filling rate of 30%, C/N is 4.2~6.2, the stirring speed is 80 r/min, T=25±1℃. The modified polyethylene carriers though the liquid phase oxidation, liquid phase oxidation- water bath- acid, liquid phase oxidation- ultrasound- acid were added in MBBRs which start-up period and stabilize period are significantly shorter than common polyethylene carriers MBBR reactor, the start-up period(respectively 16 d, 10 d and 10d) was shorter 2d, 8d and 8d than the common polyethylene carriers MBBR reactor. In stabilization period, though compared three modified polyethylene carriers and unmodified polyethylene carriers removal efficiency for COD, NO3- N, TN,organics, the polyethylene carriers surface biomass show the modified polyethylene carriers by liquid phase oxidation – ultrasound – acid were better,which NO3-N, TN and COD removal rates were 98.1%, 77.4% and 68.3%, biomass 56.14 mg / g carrier; considering the liquid phase oxidation- ultrasound- acid modified polyethylene carriers most excellent.