| Biofilm process is one of biological nitrogen removal technology inwastewater treatment. The filler as a biological carrier, have significantinfluences on the growth, structure and activity of the biofilm. The suitable fillermay promote formation of biofilm and start-up of the system, improve the systemtreatment efficiency, reduce the operation cost. Therefore, the development ofnew filler has been a hot research in the field of wastewater treatment.Polyurethane (PU) filler has many advantages such as high porosity, anappropriate pore size, low density and so on. PU filler has been successf ully usedin a variety of organic wastewater treatment. But the nitrogen removal efficiencyof PU biofilm system and its biological mechanism is still a lack of research,which limits its popularization and application in nitrogen removal of wastewatertreatment. This experiment regarded self-developed modified PU filler (MPU),build a sequencing batch biofilm reactor (SBBR) biofilm wastewater nitrogenremoval system, and investigate the nitrogen removal efficiency, establish thenitrification and denitrification kinetic model, analysis distributioncharacteristics of the nitrifying functional bacteria, provides the material,technical and theoretical support for the construction of efficient biologicaleconomy biofilm system. Based on the nitrogen removal efficiency andbiological mechanism, Modification of PU was studied further to develop newPU load tourmaline and PU load starch to treat high ammonia wastewater andlow C/N ratio wastewater and investigate ammonia oxidation and nitrogenremoval efficiency.The contrast experimental study with the conventional polyethylene filler(PE) showed that, in the same operating conditions and after achieving stableoperation, the removal efficiency of ammonia nitrogen and the COD of SBBRsconstructed by MPU (MPU-SBBR) and constructed by normal PE (PE-SBBR)were92.0%and85.5%, respectively. But the MPU-SBBR system within15d toachieving stable operation ahead of21d by the PE-SBBR system, it significantlyshorten the start-up period of biofilm system.The study of influencing factors on the biofilm nitrogen removal systemshows that, MPU-SBBR has good nitrogen removal efficiency. At roomtemperature (20℃) conditions, the optimum biological nitrogen removalconditions is HRT6h, pH7.0~8.5, DO1.5~2.5mg/L, total nitrogen removalefficiency is about75.4%. The DO maintained at a relatively low level of0.5~1.0mg/L, total nitrogen removal efficiency of MPU-SBBR system can be maintained at70.6%. The pH8.2is the most beneficial to accumulate the nitrifying bacteria,the ammonia nitrogen removal efficiency can reach over90%. With watertemperature was12℃the nitrite-oxidizing bacteria (NOB) was more inhibitedthan ammonia-oxidizing bacteria (AOB), the system had the accumulation ofnitrite, and when the temperature up to15℃, the inhibitory effect on AOB andNOB by temperature have gradually eliminated, ammonia nitrogen removalefficiency of system increased. Nitrification and denitrification reaction kineticmodel analysis showed that, nitrate saturation constant of MPU biofilm system indenitrification process was bigger than conventional activated sludge system, anda high nitrate concentration was benefit to stable remove nitrogen in MPUbiofilm system.The microbial biofilm analysis indicates that, with condition of HRT6h, pH7.0~8.5, DO1.5~2.5mg/L, microbial diversity of MPU-SBBR biofilm wassignificantly higher than that in other conditions. The advantages of AOB andNOB were Nitrosomonas sp. and Nitrospira sp. respectively, the advantages ofdenitrifying bacteria were Thauera sp. and Pseudomonas sp..The influent C/Nratio (C and N represent COD and total nitrogen respectively) had a significanteffects on short-cut nitrification and denitrification. The higher C/N ratio, thehigher biofilm biodiversity. The best ammonia nitrogen removal efficiency was79%when C/N ratio was5and the best total nitrogen removal efficiency was92.9%when C/N ratio were1.8. The advantages of nitrifying bacterial wereuncultured ammonia-oxidizing bacterium, Nitrospira sp. and Nitrobacter sp.,denitrifying bacteria was Pseudomonas sp.. The nitrogen transformation and totalnitrogen removal can be controlled by adjusting the influent C/N ratio in theproject.For the treatment of high ammonia nitrogen wastewater, the tourmaline wasload on the PU to prepare new TPU materials. Research shows that, comparedwith the unmodified PU, TPU filler surface was rougher, water holding rate washigher, can adjust effectively to the pH microenvironment, and its goodpyroelectricity and piezoelectricity further improve the adsorption properties toenrich the nitrifying bacteria. Compared with PU biofilm, the number of AOBand NOB in the TPU biofilm increased by62.9%and46.4%, respectively, whichsignificantly enhanced nitrification. In treating COD concentration of600～650mg/L and ammonia nitrogen concentration of230～250mg/L wastewater,compared with PU biofilm system, ammonia nitrogen removal efficiencyincreased by12.3%in TPU biofilm system treating.For low C/N ratio sewage, the starch was load on the PU to develop a newSPU material. The SPU filler can take a good regulating effect to nitrogen removal of low C/N ratio wastewater. For COD and C/N ratio were150mg/L and2.5of sewage, the SPU-SBBR system showed better nitrogen removal efficiency(65.3%). Compared with polycaprolactone (PCL)-SBBR system (53.3%), thetotal nitrogen removal efficiency of SPU-SBBR system increased by12%. |
PDF Full Text Request