Phosphorus Removal in a Membrane Reactor System— A Demonstration Study Wayne Lorenz, P.E. and Matthew J. Gavin Wright Water Engineers, Inc. and Newell Wright, P.E. Arapahoe County Water and Wastewater Authority

PROCESS SCHEMATIC LONE TREE CREEK WASTEWATER TREATMENT FACILITY SAMPLE POINT 1 INFLUENT SAMPLE POINT 2 MBR INFLUENT FERRIC CHLORIDE INFLUENT PUMP STATION MECHANICALLY CLEANED BAR SCREEN SOLIDS RECYCLE ANOXIC BASIN AEROBIC BASIN MEMBRANES MEMBRANE BIOREACTOR (MBR) SAMPLE POINT 3 PERMEATE MEMBRANE VACUUM/PERMEATE PUMPS UV DISINFECT DISCHARGE

SOLIDS RECYCLE ANOXIC BASIN AEROBIC BASIN MEMBRANES MEMBRANE BIOREACTOR (MBR)

Membrane ZeeWeed ® Membrane Inner reinforcing structure covered with a composite polymer outer layer Pore Size micron (nominal) 0.1 micron (absolute) Immersible, Ultra Low Pressure, Oxidant Resistant, High Strength Operates at -2 psi to -6 psi when filtering and 3 psi on backpulse Filtered Water Process Tank (Influent) X-Section Membrane Layer Inner Reinforcing Structure DiameterOuter = 1.9 mm Inner = 0.9 mm

FePO 4 (S) Fe(OH) 3 (S) Al(OH) 3 (S) AlPO 4 (S) Fe(PO 4 ) (X-3)/3 (OH) X (S) Al(PO 4 ) (X-3)/3 (OH) X (S) pH Value — 7 — 6 — 5 — 4 — 3 — 7 —6 — 5 — 4 — Log Molar Soluble Phosphorus

FERRIC CHLORIDE Fe +3 + H n PO 4 n-3  FePO 4 + nH + FeCl 3 + 3H 2 O  Fe(OH) 3 + 3H + + 3Cl -

SODIUM ALUMINATE Al +3 + H n PO 4 n-3  AlPO 4 + nH + Na 2 Al 2 O H 2 O  2 Na + + Al 2 (OH) (OH - )

Note: Samples filtered through a 0.45-micron filter.

Notes:1. Samples filtered through 0.45 micron filter. 2. pH adjusted to 6.5 using sulfuric acid.

Phase 1 Conditions Conducted over 15 weeks—December through March Average Daily Inflow = 0.98 mgd Membrane Filtration Area - 96,000 ft 2 Average Filtration Rate = 10.2 gpd/ft 2 Ferric Chloride Dosage 80 to 100 mg/L No pH Adjustment

Note: Phosphorus analyses performed by Chadwick Ecological Consultants.

MBR Average Effluent Quality Total Phosphorus0.035 mg/L BOD mg/L Ammonia1.3 mg/L Nitrate5.8 mg/L pH7.0

CONCLUSIONS Phosphorus Goal of 0.05 mg/L was met using ferric chloride at a dosage of 80 to 100 mg/L Average Phosphorus Concentration was mg/L Phosphorus removed to 0.05 mg/L regardless of temperature

CONCLUSIONS Addition of chemical to precipitate Phosphorus impacts pH and alkalinity pH conditions are key in optimizing Phosphorus removal Activated sludge was not affected by dosages in study

Phase 2 Testing Demonstrate 0.02 mg/L P removal, or less Different chemicals Limit of biomass viability Membrane maintenance