|
Biological treatment of municipal sewage in cold regions have been facing due to the impact of the low-temperature environment, the treatment effect is low, the water is difficult to standard distress. Membrane bioreactor treatment has potential advantages to the low temperature of urban sewage, hydraulic retention time (HRT) directly determines the size of the bioreactor volume, the impact of project investment, therefore, investigated membrane bioreactor short HRT conditions under low temperature wastewater treatment effect and study its strengthening measures has important significance. OF SUBMERGED MEMBRANE BIOREACTORS FOR trials using their own design effective volume of 22L, test water artificially mixed water temperature control for 7 to 8 ℃. The separate run SMBR without ultrasonic strengthen the results show that, SMBR processing low temperature start-up period is longer, the urban sewage 22d, in the case of start-up period not mud, low temperature operation reactor sludge concentration growth is relatively slow. Little impact on the stable operation of SMBR total COD removal efficiency at low temperature, the different HRT conditions under, COD removal rate than the temperature about 2% to 3% lower. Low temperature removal of NH3-N, HRT 5.3h 3.6 hours when 2.6h, NH3-N removal rate were 80%, 74%, 71%, about 10% lower than the temperature to 13%. HRT of 5.3h and 3.6h time, SMBR can remove COD and NH3-N in the low temperature in the urban sewage; When HRT reduced to 2.6h cryogenic urban sewage COD and NH3-N effluent concentrations were higher than 50mg / L, 8mg / L. The above test also showed that more serious membrane fouling OF SUBMERGED MEMBRANE BIOREACTORS FOR handle cryogenic urban sewage, 14d, approximately temperature 1/2 of the membrane operating cycle. Continue running after the physical and chemical cleaning of the membrane by low temperature operation, the membrane filtration pressure in the early running rises at a rapid rate, almost linear change in temperature when the membrane filtration pressure curve appears delay period disappeared. SMBR filamentous sludge bulking occurs in the low-temperature operation, 1851-type bacteria and 0041 bacteria staining. Filamentous sludge bulking has little effect on the COD removal efficiency, but have a serious impact on membrane fouling and membrane cleaning cycles to 7d. Experimental results show that the sludge extracellular polymeric floc relatively hydrophobic, Zeta potential and floc shape and size, and the mixture viscosity by blooms of filamentous bacteria, these factors led to the film when the sludge bulking pollution exacerbate the reason. After the introduction of low-intensity ultrasound enhanced SMBR run, in the short HRT conditions improve cryogenic urban sewage treatment efficiency and microbial activity. Experimental determination of the ultrasonic best role parameters: frequency of 28kHz, the power density of 0.27W / L, irradiation time 15min irradiation interval 24h. Results, HRT 2.6h when COD and NH3-N effluent concentrations were reduced to 10 ~~ 20 mg / L, and 5.8 to 7.9mg / L, total removal rates were increased by 7% to 13%, 13% to 16%. Low-intensity ultrasound on sludge settling, membrane cleaning cycle extension 2d, to some extent alleviate the low temperature membrane fouling. Finally, the test of ultrasonic strengthen the cryogenic urban sewage biological treatment mechanism were discussed. The experimental results show that the fluorescent staining 0.27W / L ultrasonic membrane permeability increased by 8%, and 26.75% reduction in membrane potential, membrane potential and the permeability of mutual influence, improve membrane permeability can strengthen the role of the intracellular and extracellular mass transfer. Ultrasonic mainly by changing the conformation of the enzyme molecule to change the enzyme activity and 0.27W / L, 20min / d of the ultrasonic irradiation dehydrogenase activity increased by 59.30%, activity improving promotion of biochemical reactions carried out in low temperature within the microbial cells. The ultrasonic action also affects the low-temperature microbial community structure, allows the advantages of population increase, a small amount of warm microbial recovery activity.
|