This presentation reports on the performance and optimization of the Broad Run membrane filtration reactor (MBR) system during the first two years of operation. During the first 18 months of operation, the membrane flux was, on average, between 25 to 35 L/m2/hour (approximately
15-20 gfd/ft2), and the average MLSS concentration in the membrane tanks ranged from 5,000 to 9,000 mg/l. Single-point addition of alum upstream of the membrane reactor for phosphorus removal, coupled with enhanced biological-P removal in the MBR, was able to maintain the average
concentration of TP below the detection limit of 0.05 mg/L. Alum doses significantly higher than 100 mg/L during the first six months of operation were associated with a reduction of membrane permeability. Alum doses of less than 60 mg/L (less than 2 molar alum/o-P ratios) were also associated
with a four fold increase in the time to filter (TTF), and a drop in permeability of about 25%. Use of the maximum flow capacity of internal recycle pumps, along with automatic dissolved oxygen control by a plant-wide control system, were key factors in the optimization of overall biological
performance of the MBR. Citric acid and sodium hypochlorite were used during maintenance and recovery cleans. Between recovery-cleaning cycles membrane permeability typically dropped from 10 to 2 L/ (hour. M2.bar), and the trans membrane pressure (TMP) was allowed to increase by
0.4 bar (approximately 5 psi). The membrane cassettes were successfully cleaned-in-place three times in the first 20 months of operation to recover membrane permeability.
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