A Pilot Study Of Operation Control Conditions Of Fluidized-pellet-bed Bioreactor In Municipal Wastewater Treatment

Fluidized-pellet-bed (FPB) bioreactor, based on fluidized-pellet-bed which is a high efficient solid-liquid separation technique, is a new wastewater treatment technique, which combines the high efficient solid-liquid separation technique of fluidized-pellet-bed and biodegradation ability of activated sludge, achieving high efficient treatment on municipal wastewater in a single unit. Previous research results have indicated superiorities of this technique on treatment efficiency. For this new technique is different from conventional biological treatment, thus it has special requirement on operation conditions. Based on previous study, the experiment studied effects of operation conditions and control mode on treatment efficiency and preliminarily analyzed the characteristics of microorganism population in FPB, which laid foundation for future study and application. The following main conclusions can be drawn from the study:(1) The operation conditions, which mainly are coagulant dosages, stirring speed, sludge blanket height and up-flow velocity, have considerable impacts on operation status of FPB bioreactor, and the best operation conditions based on our experiments are:Coagulant dosages: PAC 48mg/L (raw wastewater), PAM 4mg/L (raw wastewater);Stirring speed: 8-12r/min;Sludge blanket height: 1600mm, (based on our experiments, treatment results arebetter when sludge blanket height is higher);Up-flow velocity: 5-6m/h, 1.4-1.7mm/s;oxygen supply level : the depose oxygen remains 10mg/l when recycle and raw water is mixed, and remains 3mg/l at the 100mm of the reactor (R=1/1) ;(2) Granule size distribution of granular sludge along height of FPB bioreactor is more even compared with that of fluidized-pellet-bed; Granule size is bigger, but effective density decreases;(3) The TP removal rate of FPB bioreactor is almost the same compared with that of fluidized-pellet-bed without supplying oxygen, which illustrates that the phosphorus removal of FPB bioreactor mainly relies on chemical process.(4) At the best operation conditions ,compared with fluidized-pellet-bed without supplying oxygen, removal rate of turbidity by FPB bioreactor is 20% higher, COD 10% higher, NH₃-N 5% higher, TN 15% higher, all of which are the results of biological process.