CONTINUOUS-BACKWASH UPFLOW FILTRATION FOR PRIMARY EFFLUENT

The objective of the research was to investigate the feasibility of continuous-backwash upflow filtration of primary effluent. Feasibility was assessed on the basis of removal of suspended solids, turbidity, biochemical oxygen demand. and the change in particle size distribution over varying filtration rates. Continuous-backwash filtration was effective over a wide range of wastewater filtration rates varying from 96 to 264 L/m2.min (2.4 to 6.6 gal/ft2.min). An average of 70% of the suspended solids (over an influent range from 8 to 56 mg/L), 46% of the turbidity (over an influent range from 20 to 72 NTU), and 27% of the total 5-day biochemical oxygen demand (over an influent range from 61 to 101 mg/L) was removed by primary effluent filtration with no subsequent buildup of headloss. Neither the filtration rate nor the influent concentration influenced the removal efficiency for suspended solids, turbidity, biochemical oxygen demand, or affected the particle size distribution of the filtered effluent within the range evaluated.