Effect Of BM On Nutrients Removal From Synthetic Wastewater And Sludge Reduction By Using A~2/O Process

With the improvement of people’s living standards and the rapid development of industry,the volume of urban domestic sewage was significantly increased.Which resulted the low removal efficiency and poor effluent quality.At the same time,a large amount of sewage sludge was produced.Therefore,it is urgently need a advanced technology to solve the above problems.Bioaugmentation technology is gradually being applied and it has been widely studied to construct complex microorganisms and directly add them to sewage treatment systems.This technology can improve the the effluent quality,eliminate the sludge expansion,enhance the sludge settling and reduce the producing of sludge.In this study,the beneficial microorganisms（BM）were added to the A²/O process to enhance the composition and biological activity of the microorganisms in the activated sludge and promote the decomposition of organic pollutants and the dead microbial cells.Which can improve the removal efficiency of nutrients and reduce the amount of excess sludge generated,controlling the producing of sludge from the source.The bioaugmentation process only changes the composition and function of the microorganisms in the activated sludge,but not the operating conditions of system.Bioaugmentation has a good adaptability and it is the future development direction for the sludge reduction.⑴Orthogonal experiment.Orthogonal experiment was used to optimize the operating conditions of BM for the treatment of artificial wastewater.The pH value,BM dosing amount,aeration time and reaction time were selected as the influencing factors.And COD,TN,NH₄⁺-N and TP were measured in the experiment to sure the value of each influence factors.We can determined that the best operating conditions of BM for synthetic is pH 8,the BM dosage of 1/200,the reaction time of 48h and aeration time of 48h.⑵Analyzing of nutrients remove.Comparing to the A²/O process without BM,the removal rates of COD,TN,NH₄⁺-N and TP were improved by 8.78%,6.80%,6.20%and24.38%,respectively,in the the A²/O process with BM.And the nitrate and nitrite concentration in effluent were also decreased.At the same time,Dissolved organic matter（DOM）was measured to further verify the advantages of BM for organic removal.The Specific Oxygen Consumption Rate（SOUR）is used to indirectly reflect the activity of microorganisms for nitrification.In the whole experiment,the SOUR value in the A²/O process with BM was always higher than that in the A²/O process without BM,and the maximum value was 17.41 mgO₂/gMLVSS·h.Compared to the A²/O process without BM which was increased by 21.09%.And Poly-β-hydroxy butyrate（PHB）is used to analyze phosphorus removal.In the A²/O process with BM,there are more PHB in anaerobic tank.On the contrary,it almost disappeared in the aerobic tank.High-throughput sequencing showed the similarities and differences in the bacterial community structures of two A²/O processes.More importantly,Illumina Miseq results demonstrated that both the microbial community structures in two A²/O processes have been changed.The main microbial communities at the phylum level of the two systems in the study were Proteobacteria（BM:56.14%-59.71%;Without BM:52.44%-54.42%）,Bacteroidetes（BM:16.02%-18.48%;Without BM:12.63%-15.95%）,Acidobacteria（BM:4.06%-5.01%;Without BM:3.02%-3.22%）and Chloroflexi（BM:3.53%-3.61%;Without BM:2.52%-3.08%）.The microbial content of each component in the A²/O group with BM was higher than that of the A²/O group without BM.Genera with nitrifying,denitrifying,hydrolyzing,and glycogen-accumulating activities were identified in all units,indicating that functional groups were highly enriched in the active sludges and thus enabled nitrogen removal.The key functional microorganisms responsible for nitrification-denitrification in the A²/O process with BM were species belonging to Dechloromonas（BM:11.28%-11.58%;Without BM:3.32%-4.45%）,Nitrospira（BM:1.68%-2.59%;Without BM:1.11%-1.22%）,Nitrosomonas（BM:0.71%-2.33%;Without BM:0.13%-0.32%）,Hydrogenophaga（BM:2.60%-2.70%;Without BM:1.23%-1.27%）and the content in A²/O with BM was higher than that of the A²/O without BM.Which indicated that BM can effectively increase the amount of dominant bacteria in activated sludge and the biological activity of sludge in A²/O process with BM,improving the removal efficiency of nutrients in the synthetic wastewater.⑶Sludge reduction.Comparing to the A²/O process without BM,the concentration of mixed liquid suspended solids（MLSS）continues to decrease and stabled at 2759 mg/L in the A²/O process with BM.The sludge reduction rate is 23.29%.The variation of mixed liquor volatile suspended solids（MLVSS）is similar to the MLSS.The value of MLVSS/MLSS in the A²/O process with BM was slightly lower than that of A²/O process without BM and decreased to 0.48.In the whole experiment,the sludge volume index（SVI）in the reaction systems were between 70-110,which indicated that the sludge in the systems was agglomerated and its sedimentation performance was good.The content of EPS in the A²/O process with BM was significantly lower than that in the A²/O process without BM.And in the A²/O process with BM,the PN content decreased to 54.85 mg/L,while the PS content decreased to 10.57 mg/L.The dehydrogenase in microbial group was higher than that in control group.The content of extracellular polymeric substances（EPS）in the A²/O process with BM was lower than that of A²/O process without BM.On the contrast,the dehydrogenase in the A²/O process with BM was higher than that of A²/O process without BM.And the maximum value of DHA was 62.74μg/mL·h.Therefore,The BM strengthened the activity of microorganisms in the A²/O process,increased the degrading of EPS,promoted decay of cells and inhibit the growth of certain kinds of microorganisms and could hydrolyze the sludge flocs for sludge reduction.