Application Of Modified Polyethylene Suspension Packing In Moving-bed Biofilm Reactor

The main suspension filler used in the widely used Moving bed biofilm reactor（MBBR）process is polyethylene（PE）,which suffers from poor hydrophilicity,poor microbial affinity and a smooth surface that is difficult to hang a film,which affects the effluent treatment effect.In order to solve the shortcomings of PE suspension fillers,two modified suspension fillers,PE-C and PE-Ge,were prepared using the liquid phase oxidation-silane coupling agent coupling-macromolecule method,and the operating conditions of the modified fillers were optimised through the film hanging experiments and simulated wastewater treatment experiments in a laboratory reactor,and finally applied to the treatment of municipal wastewater.The main findings of the study are as follows:（1）Translated with After liquid phase oxidation and surface grafting,the contact angle between PE-C and PE-Ge was significantly lower than that of the modified filler;It was reduced from 90.8°to 42.30°and 34.29°,and the hydrophilicity was greatly improved;The surface roughness of the filler increased significantly,and the RMS value increased from 14.80 mm to 115.75 mm and 150.05 mm,respectively.The porous structure appeared on the surface of the two modified fillers,which provided a large number of attachment sites for microorganisms.The oxygen-containing functional group on the surface of the filler increased,C=O/O-C-O finktional grup,fromskrach,tecantentebon C-C functional group decreased,and the content of oxygen-containing functional group increased.improved hydrophilicity;The surface potential of the filler increases from 2 m V of the unmodified filler to 227 and 200 m V after modification,and the change of potential increases the attraction between the filler and the microorganism.（2）Study on the hanging film of two modified fillers:all biofilms were formed on the surface within one week,among which PE-C provided more active sites for microbial attachment than PE-Ge,resulting in a denser biofilm on the surface of PE-C and PE-Ge.The COD removal rates of PE-C and PE-Ge were 91.5%and 86.4%respectively,which were higher than that of unmodified fillers（79.7%）;the ammonia and TN removal rates of the two modified fillers were 88.9%,58.23%and 66.3%,60.5%respectively.PE-C and PE-G had significantly higher extracellular polymer（polysaccharide and protein）content（19.37%and 16.67%respectively）and reached the stabilisation period faster than the unmodified fillers.PE-C was studied and selected as the modified filler for subsequent experiments.（3）Experiments were carried out in the PE-C reactor to investigate the effects of hydraulic retention time,dissolved oxygen concentration,p H and filler ratio on the removal of COD and NH₄⁺-N under a single operating condition and to determine the optimum operating condition;three-factor orthogonal experiments were carried out on the hydraulic retention time,dissolved oxygen concentration and filler ratio.The highest COD removal rate was achieved when the HRT was 10 h,the filling ratio was 40%,and the DO was 1 mg/L.The effect on the COD removal rate was as follows:HRT=filling ratio>DO;the highest removal rate of NH₄⁺-N was achieved when DO was 3 mg/L.The removal rate of NH₄⁺-N was highest when HRT=6 h,filling ratio of 40%,and DO of 3 mg/L were determined to be the best experimental conditions.The degree of influence on NH₄⁺-N removal rate is:fill ratio>DO>HRT（4）The PE-C modified filler was applied to the actual wastewater treatment process,and the treatment efficiency of PE-C reactor for COD,NH₄⁺-N and TP was 90%,99%and52.4%,respectively;Among them,the treatment effect of low concentration NH₄⁺-N was good.PE-C modified filler has low cost,green and pollution-free method,and has strong application prospects.Fig[24]Table[17]Cf.[113]...