Study On Biologically Enhanced Primary Treatment Plus Biofiltration Technology Of Municipal Wastewater

The expansion of urbanization in china has aggravated the urban environment burden, whereas the relatively weak economic level has been a limit for the great amount of construction input against water pollution. So it is a definite trend to develop high-efficient municipal wastewater treatment technology with economic feasibility and sustainability. Experiment on the biologically enhanced primary treatment plus biofiltration technology (A-BF process) of municipal wastewater was studied with the designed integration device. After the cultivation and domestication of active sludge and biofllm, and the startup of experiment device in earlier stage, experiment was carried out emphatically to study the influence on pollutant removal of dissolved oxygen and flow in the low oxygen condition, and the dynamic models of the organic matter removal. The result of dissolved oxygen (DO) single factor experiment showed: under DO=0. 1 .5 mg/i, little oxygen conditions in aeration zone, organic matter of wastewater could be removed very well. While DO rose, pollutant removal efficiency increased, but the increasing degree was not apparent. Comparatively speaking, the removal rate increased most greatly at DO=0.2mg/1, which was the preferable DO value among the little oxygen conditions. The result of flow single factor experiment showed: while the flow increased, the pollutant removal reduced obviously under the little oxygen condition. The removal rate of SS was rather high. greater than 70%, and effluent SS all met the first class standard (GB8978-1996). Under the conditions of more than 40 minutes of hydraulic retention time (HRT) in aeration zone and less than 2 meter per hour of average filtration velocity, the average BOD5, COD removal of the effluent was more than 76.5%, 72.9% respectively, and effluent BOD5, COD all met the first class standard. Under the conditions of 130 minutes HRT in aeration zone, simultaneous nitrification and denitrification (SND) occurred, and effluent BOD5, COD and NH3-N all met the first class standard. which brought about quite good nitrogen removal with average NH3-N removal to be 87.5%. While the filtration velocity increased, the work period of biofilter zone shortened. The consumed water volume to backwash the biofilter was relatively less. to be 3.3%.7% proportion of the treated wastewater in the whole period.Also, the dynamic models of the organic matter removal were deduced and examined according to the experiment data. Based on these models. effluent organic matter quality could be well forecasted according to the operation conditions and parameters. Furthermore, several processes were compared concerning treatment efficiency and investment cost. For the recommended process conditions (O.2m/l DO value, 2.5 hours RRT in aeration zone, and 1.5 meter per hour of average filtration velocity), the process had many advantages such as high organic matter removal, high nitrogen removal, and cheap cost for construction and running.