Research On Operating Characteristics Of Flexible Suspension Carrier Composite Multi-stage A/O-MBBR System

The multi-stage A/O-MBBR integrated process combines the biofilm method and activated sludge method,it is widely used in sewage treatment plants because of its advantages of high processing efficiency and stable operation performance,low energy consumption and low cost.In view of the low utilization rate of recycled water in Northwest China and the characteristics of ammonia nitrogen wastewater with many types and great harm,this issues combines the flexible suspension carriers PBG with the multi-stage A/O-MBBR combined process,and launches a series of operational explorations.The MBBR processes with different side lengths of cube-shaped PBG carriers was operated stably,and then,the change in carrier holdings and the phenomenon of microbial communities was monitored for comparing the treatment efficiency on glucose simulated wastewater,by changing the A/O volume ratio and segmented water flow ratio as a single variable to compare its influence on the treatement effect,and adding humic acid to optimize the experiment,the results are followed:（1）The parallel experiment of different sizes of PBG carriers with MBBR process showed that when the volumetric load increases to 1.8 kg COD/（m³·d）,the average removal rate of COD and NH₄⁺-N in the three MBBR reactors with PBG carrier side length of 10 mm,20 mm,and30 mm all is about 89%;according to the water quality of the reactor,the change of carrier biological holding capacity,microscopic examination and SEM,it is determined that PBG₂₀is the better size carrier;The surface of PBG carrier was inspected by microscopy and its internal was observed by SEM,the results showed that protozoan and metazoan on the carrier to form long biological chain,and it adheres to the inside of the carrier to form a biofilm,and the biofilm breaks,replaces,and changes.The specific surface area of up to 4000m²·m^-3provides environmental conditions for the survival of anoxic/anaerobic microorganisms in an aerobic environment;（2）The experimental results of PBG-two-stage A/O-MBBR combined process with different A/O volume ratios show that the average effluent concentration of COD,NH₄⁺-N,TN,and TP in the 1:2 system are 51.4 mg/L and 0.636 mg/L,9.147 mg/L,3.01 mg/L,the average effluent concentrations of COD,NH₄⁺-N,TN,and TP in the 1:3 system are 38.66 mg/L,1.256 mg/L,10.09 mg/L,3.79 mg/L.The average concentration of NH₄⁺-N and TN effluent of the two systems reached the standard A of the"Shaanxi Province Yellow River Comprehensive Wastewater Discharge Standard"（DB61/224-2018）.Among them,the 1:2 system has a better effluent effect than 1:3 system;（3）The experimental results of the PBG-two-stage A/O-MBBR combined process with different sub-inlet distribution ratios show that under the premise that the COD and NH₄⁺-N effluent gap is not obvious,the TN removal effect is better when the feed water ratio is 1:1,the average removal rate is 89.75%,and the result of adding humic acid to the aerobic zone I showed that the removal rates of COD and NH₄⁺-N were increased by about 16%and 13%.