Research On Nitrogen And Phosphorus Removal And Microbial Community Structure Of Marine Integrative Membrane Bioreactor

Nowadays,all countries around the world paid more attention to protect ocean and inland river environment,and stricter discharge requirements about ship wastewater was made by the International Maritime Organization?IMO?.Besides the original text items,COD,and BOD₅,IMO had put forward specific emission requirements of total nitrogen?TN?and total phosphorus?TP?.Membrane bioreactor?MBR?was fully applied to ship sewage treatment because of its strong anti shock and swing.Although the applied MBR have obtained certain achievements at present,they still have defects in the instability of nitrogen and phosphorus removal or the large footprint.In this study,a fully aerobic integrative MBR was investigated to remove COD,nitrogen and phosphorus of typical ship sewage,and added an adsorption column to MBR in order to improve the efficiency of phosphorus removal.The adsorbent selected according to conditions of the MBR effluent and research the improved reactor.The bacterial community structures in different periods and different conditions were traced by fluorescence in situ hybridization?FISH?,and dynamic association between the main functional bacterium was evaluated.The research studied the performance of COD removal when the HRT changed from 8h to 3h and the range of PH is 5 to 9.This results find out that in order to satisfy the standard of IMO,HRT shoud kept of more than 6 h and pH of 8 is the best condition,and the highest COD volume loading was 16 kgCOD/m3·d.Based on the research of the performance of nitrogen removal,it states that control the DO concentration at the range of 2.5³.0 mg/L to meet the standared of TN and when the influent TN concertrations was higher than 80 mg/L,dilution should proceed to the influent.The TP remove was depend on microbe assimilation and the reactor presented the high phosphorus removal rate of 6mg/L.Hence an adsorption column should be add at a high TP concertration.Adsorption of phosphate by limonite,goethite,iron oxide and iron oxide coated sand?IOCS?were studied on batch experiments.The dosing quantity of goethite was 0.5 g,the TP removal efficiency was 64.8%.When regeneration by using NaOH solution of 0.05 mol/L,the regeneration rate of goethite was 93.4%.The adsorption of P on goethite was spontaneous and exothermic.Hence,a goethite column was researched of its phosphorus removal property.The results indicates that the adsorption column significantly decreased the phosphorus concentration to near zero when the influent TP concentration at the range of 8¹6 mg/L.The adding of column can enhance the TP load of the system from 6 mg/L to 16 mg/L.The results of FISH showed that Betaproteobacteria and Gammaproteobacteria occupied11.2%and 8.1%of the bacteria total amount respectively when the COD removal efficiency was higher than 93%.Monitoring these two types of bacteria can infer the capabilities of COD removal.The species richness of AOB was not below 11.2%and the species richness of NOB was not higher than 6.4%.Hence the AOB was take an more important position on TN removal.At a C/N of 20:1,the MBR was strong to remove the COD and when the influent COD was too low or the influent TN concentration was too high we should adjust the C/N by adding the carbon source.When salinity was higher than 6 g/L,dilution should proceed to the influent.