Initiation and Molecule Ecology Analysis of Low Dissolved Oxygen Limited Filamentous Bulking at Low Temperature

Actual domestic sewage was treated by SBR process.Limited filamentous bulking was induced by low dissolved oxygen at low temperature,and the SVI were maintained 150-200 mL/g.The occurrence of limited filamentous bulking at low temperature and the growth of microorganism were researched;the technique of FISH was adopted to identify the species of the dominant filamentous bacteria in the state of limited filamentous bulking,and the result showed that the filamentous bacteria that led to limited filamentous bulking was microthrix parvicella (MPA223).Compared to the status at normal dissolved oxygen,the removal rate of COD and PO₄^3--P increased to 80% and 90%,while the removal rate of NH₄⁺-N and TN decreased to 52% and 28% respectively during limited filamentous bulking.And the data also showed that low dissolved oxygen led to the phenomenon of simultaneous nitration-denitration (SND),about 15% of the nitrogen was removed by SND.