Study On Nitrogen Removal Performance And Membrane Fouling In An Anammox Membrane Bioreactor

Anaerobic ammonium oxidation(anammox)is a novel biotechnology process in which the anammox bacteria diectly transform ammonium and nitrite into nitrogen gas under anaerobic conditions.Anammox process escapes the dependences of carbon sources and aeration,is regarded as the most efficient and economical biotechnology.However,the partical application of anammox process is under restrictions because of the strict condition control and the low growth rate of anammox bacteria.Membrane bioreactor is another novel biotechnology process which combined membrane separation technique and bioreactor.The process has many advantages,such as:efficient solid-liquid separation and small aera,is regarded as the most promissing biotechnology.In this paper.the anammox process and bioreactor is combined to explore the effect of different effluent flux and influent loading on an anammox membrane bioreactor.The main contents and research results are as follows:(1)There is no significient differences on nitrogen removal performance under different effluent flux with the operation of the reactor.The removal rate of ammonia and nitrite is above 80%and 90%respectively,showed good nitrogen removal performance.The membrane fouling rate of the membrane module with higher flux is faster obviously,and the concentration of PN and PS iii membrane foulants are also higher than the module with lower flux in unit time.We can see the higer the effluent flux is,the severer the membrane fouling is.(2)The nitrogen removal performance of the reactor always in a high level with the concentration of inlfuent loading increased.indicting that there is no significient influence on nitrogen removal performance of the reactor with the increase of influent loading within a certain concentration range.However.the increase of influent loading will lead to the increase of the concentration of PN and PS in membrane foulants,thus the membrane fouling will aggravate to some extent.(3)High-throughput sequencing results revealed that the microbial community structure of sludge is in a stable state in the reactor,and annmmox is the dominant bacteria all the time during operating time.The microbial community structure of membrane foulant is similar to the microbial community structure of sludge in the reactor.There is no obvious change of the species abundance of membrane foulants in different stage of TMP.However,sprcies uniformity will enhance when the membrane fouling get severer,indicating that sprcies uniformity is positively correlated with membrane fouling.(4)The results of SMP release potential test showed that sludge in the reactor has higher SMP release potential than membrane foulants.According to the results of the test,we can surmise that SMP might be fendamental source of PS in membrane foulants,and EPS might be fendamental source of PN in membrane foulants in severe stage of membrane fouling.(5)The results of relative molecular weight distribution test revealed that biological molecule which molecular weight is more than 100 kDa has higher potential of membrane fouling.The colloidal state biological molecules(>0.45?m)are mainly from PN,and the polymeric state biological molecules(100 kDa-0.45 ?m)are mainly fiom PS.Results from this study demonstrated that anammox membrane bioreacto has good nitrogen removal performance and revealed the source and characteristic of membrane foulants,provided technical support for application of anammox process.