Study On The Operational Efficiency Of The Symbiosis System Of Bacteria And Algae In Membrane Bioreactor

Membrane bioreactor（MBR）is a new process which combines membrane separation technology with traditional activated sludge process.It has many advantages and has great competitive in the field of wastewater treatment and reuse.However,membrane fouling and the problems of energy-extensive consumption still limit the development of the process.The removal effect of total phosphorus is also difficult to achieve satisfactory.In recent years,the bacterial-algal symbiosis system has attracted much attention due to its high organic matter removal rate.The introduction of algae in MBR,combined with the advantages of the two,can achieve high-quality effluent and solve the problem of microalgae loss and difficult recovery.Therefore,the combination of MBR process and bacteria algae symbiosis system shows great potential of productivity in the field of wastewater treatment and reuse.This study closely focused on the bacterial and algal symbiosis system in the MBR,investigated the changes in the operation efficiency of the MBR after the addition of algae,combined with the change of EPS in sludge mixture and membrane fouling,clarified the biological aggregation mechanism of the bacterial and algal symbiosis system,and explored a new method for the pollution control of the MBR microfiltration membrane.The main results are shown as follows:（1）The effect of algae addition on pollutant removal of bacteria algae symbiosis system in MBR was investigated.The results showed that bacteria algae symbiosis system had a certain improvement on pollutant removal,especially the total phosphorus（TP）removal rate,which reached 42.0%,chemical oxygen demand（COD）and ammonia nitrogen（NH₄⁺-N）,which removal rate both increased slightly.It was found that the bound extracellular polymeric substances（B-EPS）of algae membrane bioreactor（AMBR）were the main components of EPS,Compared with the control group,PS and PN in B-EPS showed a downward trend,PN/PS value decreased by 17.1%,which had a greater mitigation effect on membrane pollution;through the investigation of mixed liquid characteristics,the results showed that the fluctuation of conventional indexes in sludge characteristics was normal,the distribution of PSD clearly showed the peak change trend of particle size distribution,and the filterability of AMBR was greatly improved,up to 63.7%.（2）The results showed that the addition of microalgae changed the hydrophilicity and hydrophobicity of sludge flocs,increased the hydrophilicity of sludge flocs,and significantly reduced the membrane fouling potential of sludge flocs.By comparing the interaction energy between sludge flocs and membrane,the results showed that the energy barriers of flocs aggregation and adhesion to membrane in AMBR were larger than those in control membrane bioreactor（CMBR）,and the membrane fouling tendency was reduced.（3）The results showed that the membrane fouling rate of CMBR was concentrated in the range of 0-4 k Pa/d,while that of AMBR was concentrated in the range of 0-2 k Pa/d,which was lower than that of CMBR.The membrane fouling of MBR with algae was improved.The filtration resistance distribution experiment shows that the internal resistance R_fof CMBR is 1.48 times of that of AMBR,the amount of colloid and soluble organic matter in sludge mixture is larger,and the permanent damage to membrane is more serious.