Study On Treating Wastewater With High-load Phenolic In Aerated Biological Fluidizing Tank

Phenolic wastewater is an important category from industrial sectors. Biological methods have been used for the treatment of medium-low strength phenolic wastewater since the cost is low compared with other technologies. However, present biological methods usually have low load or instable removal efficiency because of the toxicity of phenol against microbial cells. In this study, aerated biological fluidized tank (ABFT) was used to treat a synthetic phenolic wastewater and a stable removal is achieved at a high phenolic load. The microbial community structure in the ABFT system and the mass transfer characteristics inside the ABFT packing media was analyzed with molecular biotechnology and microelectrode technique. And the results provide a better understanding on the phenol removal in ABFT process and facilitate the process improvement.It is found that phenol can be removed by more than 90% in 2 hours with ABFT at a phenolic load of 1.7kgBOD/kgMLSS·d , when the phenolic concentration of inflow is 400mg/L. On the other hand, ABFT System could be restored in a short time when removal efficiency of phenol came down because of machine errors, which proved a great stability of ABFT for phenolic wastewater treatment.With a stable COD of inflow at 800mg/L during acclimation period, microorganism in porous packing media proliferated and the microbial community structure changed greatly when the phenolic concentration increased from 0 to 400mg/L in wastewater. Based on SEM microphotographs, it was found that the predominant microorganism in porous packing media changed from coccus or brevibacterium to bacillus and filamentous when phenol was added. The microbial communities in suspended sludge flocs and biofilms attached on packing media were analyzed with PCR-DGGE technique respectively. It is found that besides bacterial species such as Flavobacterium and Zoogloea, there are also mycelial fungus such as Geotrichum sp. in large quantity, which are specially abounded in the 1^st reaction tank and play an important role in the treatment of high strength phenolic wastewater by ABFT.The characteristics of microbial species group and internal DO distribution in the porous packing media of the 1^st reaction tank were analyzed with scanning electron microscope and dissolved oxygen microelectrode. When DO in matrix solution is 7～8mg/L and DO is nearly 0.4 mg/L in the centre of packing media. Less than 2mm below the surface of packing media is an aerobic zone, dominated by mycelial fungi, while more than 2mm below the surface of packing media is an anaerobic/anoxic zone, dominated by bacteria. Diffusion coefficient of DO inside the packing media is calculated as 0.0446m²/d according to porous model, which infers that the oxygen transfer inside the packing media mainly rely on turbulent fluctuation.