A Study On The Treatment Of Domestic Wastewater By Biological Pellet Fluidized Bed

Biological pellet fluidized bed is a new and efficient wastewater process which combinestraditional biological fluidized bed technique with pellet coagulation technique perfectly.Thisprocess removes organic substances, phosphorus and nitrogen at the same time in amicroenvironment of nitrification simultaneous with denitrification by controlling some trialparameters. The experimental results show that the reactor can remove COD, SS, BOD,turbidity, color, NH3-N, TN and TP effectively.When the [PAC]=40mg/L, [PAM]=5mg/L,stirred paddle rotation speed=18r/min, water intake=150L/h, the average removal efficiency is89%, 98.6%, 87.5%, 93.0%, 95.6%, 67.6%, 58.1% and 95% respectively. The waterquality of the effluent reaches the secondary effluent standard or better than that. Theconcentration of COD, BOD, NH3-N, TN and TP decrease while NO3-N and NO2-Nincrease along the height of the reaction column. The study on the distribution of organicsubstances shows that the molecular weight distribution of organic substances in the effluentmainly distributes in the range of 500-1000Da. It shows that it affected by chemical , physicaland microbial facts together. The mechanism of denitrification and dephosphorylation may beexplained by the theory of microenvironment and certain chemical reactions. The kinetic studyon the removal of organic substances by the reactor shows that the course accords with thefirst order reaction. From the fluidity of mixed flow, it can be regarded as a complete mixingflow in series with a plug flow and the former's retention period is 9.5mins and the latter's is74.5 mins.