Effects Of Mo⁶⁺ On Aerobic Granular Sludge Culture And Its Nitrogen And Phosphorus Removal

erobic granules have a wide range of applications in nitrogen and phosphorus removal,degradation of toxic substances and high concentration organic wastewater treatment,for its remarkable settle ability,high metabolic activity and biomass retention,and tolerance of high organic load.In recent years,metal cations was widely applied to wastewater treatment for its critical importance for self-flocculating and self-immobilization of microbial aggregates,and extracellular polymeric substances.The metal cations also can prompt aerobic sludge to achieve rapid granulation.There is no study about Mo⁶⁺ on the rapid aerobic granulation.Therefore,this paper studied the effects of discusses the effects of different concentrations of Mo⁶⁺ on the formation of aerobic granular sludge and its ability of pollution control,and discussed the mechanism of Mo⁶⁺ in the process of its formation.The main results were concluded as follows:1.The augmentation of Mo⁶⁺ can promote the aerobic granulation.We succeeded to cultivate aerobic granules under our experimental conditions.Adding 1¹0 mg/L Mo⁶⁺promoted the granulation,and the effect was more obvious while adding 2.5 mg/L Mo⁶⁺.Whereas,the granules cultivated with addition of 25 mg/L Mo⁶⁺ were not very stable.2.The average size of granules with addition of Mo⁶⁺ were larger than that of control,and had good settle ability.After the formation of granular sludge,SVI value of aerobic granules augmented with 1¹0 mg/L Mo⁶⁺ were stable in the vicinity of 30 m L/g.3.The augmentation of Mo⁶⁺ can promote the secretion of EPS,especially the content of extracellular proteins,and the ratio of PN/PS increased significantly in the process of granulation.It indicated that extracellular proteins would play a more important role than polysaccharides.The augmentation of Mo⁶⁺ promoted the dehydrogense activity of aerobic granules,improving the use of organic matter.4.The fourier transform infrared spectroscopy was used to determine the functional groups on the aerobic granules,results showed that the granules contain proteins,polysaccharides,organic acids and so on.The augmentation of Mo⁶⁺ acts on the granules,the infrared spectrogram can produce some subtle changes,the vibration of the-O-H and-N-H area shifted from 3423 cm^-1 to 3416 cm^-1,and the vibration of the-COOH area shifted from 1401 cm^-1 to 1384 cm^-1,which indicated that Mo⁶⁺ complexed with the branched chain of protein and-COOH.Wavelength 1734 cm^-1?-COOR?disappeared while Mo⁶⁺ was added,it indicated that the addition of Mo⁶⁺ may cause the destruction of themembrane lipids and cell walls of microorganisms in aerobic granular sludge.5.High-throughput sequencing technologies was employed to sequence the 16 Sr DNA of microorganisms in aerobic granules induced by Mo⁶⁺ deeply.The results showed that the absolute dominant group in the granules cultivated without Mo⁶⁺ was Bacteridetes25.56%,the most dominant taxa of 2.5 and 10 mg/L Mo⁶⁺ was Chloflexi?19.28% ?23.55%?,and 25 mg/L Mo⁶⁺ was Proteobacteria 49.81%.A17? Nitrospira?Dok 59 and Zoogloea were sensitive to Mo⁶⁺.The augmentation of Mo⁶⁺ had a certain influence to the microbial community structure in aerobic granules.The microbial population abundance and biodiversity was improved while adding 2.5¹0 mg/L Mo⁶⁺,however it decreased while adding 25 mg/L Mo⁶⁺.6.?NH₄?⁺-N and ?PO₄?^3--P removal rate of aerobic granules augmented with Mo⁶⁺ was ramained at a steady state in the late stage of culture.While adding 1²5 mg/L Mo⁶⁺,the removal rate maintained at about 90% and 75%,respectively.The granules without addition of Mo⁶⁺ maintained at about 80% and 65%,respectively.It can be concluded that the augmentation of Mo⁶⁺ improved the ability of denitrification and dephosphorization,and ?NH₄?⁺-N removal efficiency was better than ?PO₄?^3--P at the same concentration of Mo⁶⁺.