Characterization Of The Microbial Community Structure And Effectivenesses Of Phosphorus Removal In WWTPs

Regulation and control of biological treatment system was based on chemical andphysical characters of inflow and effluent water, temperature, dissolved oxygen,oxidation-reduction potential, sludge retention time, hydraulic retention time in mostmunicipal wastewater treatment plants. Those methods which effect or refleet status ofactive sludge indirectly may result in instability of biological treatment system.Fluorescence in situ hybridization (FISH) could test microorganismsand their structurein the community, which will provide an alternative to stable operation of biologicaltreatment system.The bio-P release and take up activity from three plants in Xi’an city wasdetermined by execution of anaerobic-anoxic-aerobic batch tests using fresh activatedsludge. Fractions of Accumulibacter as potential phosphorus accumulating organisms(PAO)，and Competibacter，potential glycogen accumulating organisms (GAO) werequantified using FISH.The proportions of PAOs and GAOs in activated sludge varied from0.43%to5.34%and0.16%to10.08%of EUBmix， respectively. Among those active sludgesimples, the frist-stage project of Xi’an No.4WWTP acquired the best enrichmenteffect, the proportions of PAOs and GAOs were5.34%and1.27%of EUBmixrespectively. Notably, PAOs proportion of the frist-stage project of Xi’an No.3WWTPwas3.50%of EUBmix, while GAOs proportion reached up to10.08%.Among all active sludge samples significant difference in shape was observedbetween PAOs and GAOs. Those PAOmix hybridized cells often clustered into denselypacked microcolonies， while GB hybridized cells appeared as singly loosely dispersed cells and scattered throughout the flocs.P-release rates varied from2.81~11.03mg P/g VSS/h， anaerobic P/HAc ratiowere found to be0.098mgPO43--P/mg HAc~0.345mgPO43--P/mg HAc.Anoxic/aerobic P-uptake rates ratios fluctuated from71.91%to lower values33.02%.The Anoxic/aerobic P-uptake rate ratios indicated denitrification capacity of PAOs.The Poly-P was stained by DAPI,and then the results was compaired with FISHresults. It can be observed that rarely PAOs contain poly-P while cells presented andmany Poly-P presented in cells did not marked by PAOmix. This finding suggested thatit is impractical to assess the EBPR activityin a WWTP by attempting to relate thenumerical dominance of PAOs to its polyP-accumulating capacity since a highproportion of PAO cells were not accumulating polyP or polyP contents of their cellswere not so high that theyare detectable as polyP granules. And indicated that thephosphorus accumulating ability was showed by some cells which PAOmix did notmarked.