The Effects Of Zero-vale Iron On The Performance That Nitrification Granular Sludge And Recovery

Because of unique properties of physical and chemical,micro zero-valent iron and nano zero-valent iron are widely used in production and living.Now,The technology of micro-size zero-valent iron is more and more used in wastewater treatment,zero-valent iron is often used to remove toxic pollutants as halogenated hydrocarbons,inorganic salts and heavy metals that it has nontoxicity and strong reducible.But,there are some mZVI and nZVI leak in sewage biological treatment process cause potential effects on activated sludge.Partial nitrification granular sludge is a biodenitrification technology based on the biofilm technology of granular sludge with stable nitrification ability.PNG has rich microbial community,strong resistance to environmental changing.However,ammonia-oxidizing bacteria is the main bacteria in PNG,it is sensitive for environmental factors,long generation cycle and difficult to enrich.At present,it is hard to find research about effect of micro-sized zero-valent iron on nitrosated granular sludge,effect of ZVI on the performance of nitritated granular sludge has great research value.The main research contents and results are as follows:?1?Research of ZVI short-term effect on the nitration performance of PNG,batch test of nitrosation granular sludge with different doses of nZVI and mZVI,in short-term impact PNG function that nitrogen transforming ability,AOB bacteria activity and content of ZVI in granular sludge.The results showed that the concentration of ZVI in 0²5mg?L^-1,nitrogen transforming ability and EPS components and AOB activityof PNG are promoting,unit nitrogen transformation ability less than 10%.The concentration in 50⁷00mg?L^-1,high concentration of mZVI and nZVI have strong negative effect on the nitrogen conversion ability and functional bacteria of PNG.The reduction of ammonia conversion in unit time are3.45mg??g?h?^-1 and 8.89mg??g?h?^-1,the rate of ammonia oxidation decreasing amplitude9.18mg??g?h?^-1and 20.55mg??g?h?^-1,the polysaccharide content in EPS was reduce by45%and 64%respectively.PNG has good adsorption capacity for ZVI,the isothermal adsorption of granule sludge conforms to Freundlich isotherm.PNG adsorb ZVI is mainly based on multi-molecular layer adsorption.?2??2?Research of ZVI long-term effect on the nitration performance of PNG,adding certain dose(5mg?L^-1)of mZVI and nZVI in continuous flow of granule sludge reactor.The changes of nitrogen transformation,EPS composition,particle morphology and functional bacteria activity of PNG are observed in research.In mZVI and nZVI dosing process,13d and 26d nitrogen transforming ability are began to deterioration,in 60d,ammonia removal rate was reduced by 31.5%and 42.3%respectively in granular sludge reactor,protein content was reduced by 39%and 50%respectively,polysaccharide content was reduced by 30%and 52%respectively.The granular sludge In reactor is broken and disintegration under the ZVI dosing,MLSS rerduce by 1.96g?L^-1and 1.48g?L^-1,MLVSS rerduce by 1.79g?L^-1and 1.46g?L^-1,when mZVI and nZVI content in granule sludge are 7.37mg?g^-1 and 11.1mg?g^-1,SOUR-A reduce by 22.6mg??g?h?^-1 and 31.2mg??g?h?^-1.The activity of microbial enzyme in reactor is highly fluctuation by ZVI dosing,the LDH is greatly increase and the ATP is rapidly reduction.?3?Research of recover PNG nitration performance after ZVI dosing,analysis of the relationship between ZVI accumulation and functional bacteria activity in PNG,discussing the situation of PNG deterioration in ZVI rapid enrichment process.In recover PNG nitration performance process,,nitrosation granular sludge ammonia removal rate increased by 13.5%and 13.5%respectively by lengthen HRT,the sludge quantity increase by more than 20%.PN and PS in EPS increase by more than 25%in this process.The amount of iron in the sludge reduce by 45.5%and 36.7%respectively in PNG,and the ammonia removal recover to 70%and 59%respectively.The increase of PH in influent can effectively remove Fe content in granular sludge and improve the recovery speed of granular sludge performance.