| With rising of city population and people’s living standard, the content of nitrogen andphosphorus in sewage increased. The water eutrophication is more and more serious, thedevelopment of a kind of high efficient cheap process becomes a problem urgently to besolved. Non-woven fabric-CASS process (Non-woven Fabric-Cyclic Activated SludgeSystem, referred to F-CASS) integrated not only the advantages of traditional CASS andmembrane biological reactor, but also solve the high cost problem and high energyconsumption of the membrane biological reactor, and the study has higher practical value andimportant research significance. The best operation condition of CASS, the denitrification anddephosphorization effect of F-CASS process were studied. The decontamination mechanism,pollution mechanism and cleaning methods of non-woven fabrics were analyzed.Different influent time and aeration time, sludge return ratio and water discharge ratio inCASS process were investigated in the present study. The obtained result showed that theinfluent time of4h, aeration time of3h, sludge return ratio of25%, water discharge ratio of1:3were the optimal operation parameters. On this basis, the10μm non-woven fabric and30μm non-woven fabrics of contamination removal effect in F-CASS reactor were tested. Theresults showed that CODcr average effluent concentration of the two non-wovens were26.16mg/L and25.68mg/L respectively, its removal rates were over90%. The averageremoval rate of NH4+-N were95.19%and94.91%respectively, the concentration of NH4+-Nin effluent were both under5mg/L. The average total nitrogen removal rate were86.62%and86.70%, the concentration of TN in effluent were both under15mg/L. Total phosphorusaverage effluent concentration were about0.32mg/L, The average effluent turbidity were0.59NTU and0.60NTU, suspended solids are not detected, it proved its good solid-liquidseparation ability.The filtration mechanism of non-woven in F-CASS process was analysed, the resultsshowed that, non-woven filter effect was mainly composed of mechanical screening andbridging flocculation, superficial adsorption and secondary interception and the four kind ofseparate mechanisms played different roles in filtration process. The research of non-wovenpollution mechanism and filtration resistance showed that, the pollution of non-woven fabrics was mainly composed of the filter cake that adhering to the surface and the gel layer thatadhesion in non-woven internal structural. The main source of non-woven filter resistancecomes from the two. The total resistance was1.286×109m-1in30μm non-woven experiment.And the two polutions were about81%and18%of the total resistance, respectively, and therest of the resistance was from non-woven itself.By comparison the non-woven cleaning methods we found that physical cleaning ofsingle artificial wash and hydraulic flushing can only recover about71%of flux, but artificialwash and ultrasonic combined effect significant, it can recover85.78%of flux atmostly. InChemical cleaning, cleaning effect of alkaline cleaner was better than the acid cleaner andoxidant cleaner, acid cleaner and oxidant cleaner can recover80%of flux, and alkalinecleaner can achieve90%above, according to the cleaning effect, the safety of the cleaningmethod and the practical requirement, the appropriate chemical cleaning method was NaOHsolution of0.001mol/L by soaking6h. |
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