In-Canal Phosphorus Treatment Study for Barr Lake Project Kick-off Meeting Barr Lake/Milton Reservoir Watershed Association January 28, 2014 Harvey H. Harper, Ph.D., P.E. Environmental Research & Design, Inc.
Uses for Alum in Lake Management 1. Treatment of external inflows - Alum treatment of stormwater and surface water other flows to remove nutrients, particularly phosphorus 2. Inactivation of internal phosphorus recycling - Alum addition to sediments to bind available phosphorus
Characteristics of Alum -Clear, light green to yellow solution, depending on Fe content -Liquid is 48.5% solid aluminum sulfate by wt. -Specific gravity = 1.34 -11.1 lbs/gallon -Freezing point = 5 ° F -Delivered in tanker loads of 4500 gallons Alum is made by dissolving aluminum ore each (bauxite) in sulfuric acid
History of Alum Usage Drinking water – Roman Times Wastewater – 1800s Lake surface – 1970 Stormwater – 1986 Alum is used to make many common items, such as: - pickles - baseballs - antacids - deodorants - vaccines
Initial Experiments (1980) Initial testing evaluated salts of: - Aluminum - Iron - Calcium Colloidal Runoff Alum was most effective Sample Immediately Following Alum Addition Alum Reacts Quickly to After 12 Hours Remove Both Particulate and Dissolved Pollutants
Treatment Effectiveness vs. Aluminum Dose Treatment efficiency improves with increasing alum dose up to the “optimum” dose at which no significant improvement in effectiveness occurs
Significant Alum Removal Processes 1. Removal of suspended solids, algae, phosphorus, heavy metals and bacteria: +3 + Al + 6H O Al(OH) + 3H O 2 3 3(ppt) 2. Removal of dissolved phosphorus: +3 n-3 + Al + H PO AlPO + nH 4(ppt) n 4
Aluminum Coagulants Aluminum Sulfate (alum) Aluminum Chloride Poly-Aluminum Chloride Alum/Polymer Blends (floc logs)
Alum Coagulation Advantages - Rapid, efficient removal of solids, phosphorus, and bacteria - Inexpensive – approximately $0.60/gallon - Low contaminant levels - Relatively easy to handle and feed - Does not deteriorate under long-term storage - Floc is inert and is immune to normal fluctuations in pH and redox - Floc binds heavy metals in sediments, reducing sediment toxicity Disadvantage - May result in lowered pH and elevated levels of Al +3 if improperly applied
1. Treatment of External Inflows
History of Chemical Stormwater Treatment Initial research on chemical coagulation conducted in the late 1970s – Evaluated salts of Al, Fe, and Ca Chemical coagulation evaluated for several stormwater retrofit projects in the early 1980s First system constructed at Lake Ella in Tallahassee in 1986 Currently, 60 systems have been designed and constructed in Florida with 4-5 in other states Systems have been designed to treat a wide variety of inflow types
Procedures For Evaluation Of Alum Treatment Feasibility 1. Collect representative samples of inflow to be treated - Include stormwater as well as dry weather baseflow, if present - Samples should reflect anticipated range of water quality characteristics 2. Perform jar testing to evaluate: - pH response to alum addition - floc formation rates and settling characteristics - removal efficiencies for constituents of interest 3. Perform hydrologic modeling to: - evaluate range of flows to be treated - estimate annual volume to be treated - establish design parameters for process equipment 4. Evaluate floc collection and disposal options - floc collection may or not be required depending on the receiving water - floc may be collected in a dedicated settling pond - collection and disposal to sanitary sewer - direct inflow into receiving water
Typical Percent Removal Efficiencies for Alum Treated Stormwater Runoff Alum Dose (mg Al/liter) Settled Without Parameter Alum (24 hrs) 5 7.5 10 Ammonia ~ 0 ~ 0 ~ 0 ~ 0 NOx ~ 0 ~ 0 ~ 0 ~ 0 Diss. Organic N 20 51 62 65 Particulate N 57 88 94 96 Total N 15 ~ 20 ~ 30 ~ 40 Diss. Ortho-P 17 96 98 98 Particulate P 61 82 94 95 Total P 45 86 94 96 Turbidity 82 98 99 99 TSS 70 95 97 98 BOD 20 61 63 64 Fecal Coliform 61 96 99 99 - Removal efficiencies for waters with elevated color will be lower
Lake Lucerne – Orlando Southern Gateway - Surface area = 29 acres (11.7 ha) - Lake divided into eastern and western lobes by 6 lane road - 267 acre watershed - Six primary inflows contribute 95% of annual runoff Lake - Mean depth = 10 Lucerne (21.0 ac.) ft (3 m) - Pre-modification TP conc. > 100 µg/l
Mechanical components for the Lake Lucerne alum treatment system are housed in an underground vault beneath an elevated expressway Pump control panels Chemical metering pumps Flow meter control panels
Lake Lucerne following start-up of the alum stormwater treatment system
Lake Lucerne Total Phosphorus 180 Testing / Startup 160 System Offline Before Alum Total Phosphorus (µg/l) 140 During During 120 System System Operation Operation 100 80 60 40 20 0 1990 1991 1992 1993 1994 1995 1996 Date
Lake Dot – Orlando 5 ac. Lake Receiving Runoff from 305 ac. Urban Watershed Pre-treatment Water Quality 108 inch Stormsewer Post Treatment Water Quality Newspaper Cartoon
Lake Howard Equipment Building Underground Alum Storage Tank Floc Discharge to Lake Alum Injection Equipment
Gore Street – Clear Lake Equipment Building Floc Disposal System Floc Pumping Equipment In-line Floc Trap In-line Floc Trap Permeable Fabric
Merritt Ridge Equipment Building In-line Floc Settling Pond Regional Flood Control Pond used for Floc Collection Alum Injection Equipment pH Control Equipment
Largo Regional Alum Treatment System Treated Watershed Area = 1500 acres Drivable Drainage Diversion Weir Alum Injection Building Canal Flow Diverted Into Box Culvert Flow
Largo Regional Alum Treatment System Components 15 Acre Hardwood Wetland Floating Dock Elevated Enhancement Wooden Boardwalk Outflow Floc Settling Pond Wetland Paved Enhancement Inflow Walking Path
Phophorus Concentration (µg/l) 100 150 200 250 50 0 Diss. Ortho-P Outflow Inflow Largo Alum Stormwater Facility Diss. Organic P Nutrient Removal in the Particulate P Total P Nitrogen Concentration (µg/l) 1000 1500 2000 2500 500 0 NH3-N NOx Diss. Organic N Outflow Inflow Particulate N Total N
LCWA Nutrient Reduction Facility (NuRF) Lake Dora Lake Beauclair NuRF Site Lock & Dam Apopka-Beauclair Canal Lake Apopka (12,000 ha)
Overview of NuRF Project Outflow Canal Lock and Dam Structure Pond 2 Pond 1 Area = 8.2 ac. Area = 8.2 ac. Depth = 20 ft . Depth = 20 ft . Alum/Air Addition Pump and Control Apopka- Building Beauclair Canal Inflow 6 – 12,000 gal Canal Storage Specifications Tanks Storage/Mixing -Treat flows to 300 cfs Tank -Cost = 7.2 million -Alum Use = 1.5 – 2.9 million gal/year -35,078 gal/day at peak flow Dewatering Building -Treats 89% of annual canal flow Dried Floc Storage Area -TP Removal = 10,000 kg/yr -10-20,000 ft 3 dried floc/yr -Floc used as soil amendment -P removal cost = $200/kg
Estimated Annual Discharges Through the Apopka-Beauclair Canal Estimated Annual Mass Load (kg/yr) Annual Canal Condition Discharge Total N Total P TSS BOD (ac-ft/yr) Existing 54,092 193,972 13,328 2,465,472 339,836 1959-2000 137,002 3,838 591,713 209,781 Post 54,092 Treatment 1 (-29%) (-71%) (-76%) (-38%) 1. Assumes that the system will treat 89% of water on an annual basis
Lake Seminole Bypass Canal and Basin 1 Alum Treatment Systems Bypass Canal Pump and Control Building Pumped Inflow ~ 10 cfs Alum Added Basin 1 Floc Pumped Canal to Sanitary Alum/Air In-Lake Floc Pump Station Addition Settling Area Treated Water Discharges to Floc Settling Trough Treated Water Lake Seminole Discharge
Lake Seminole Bypass Canal Treatment System Seminole Bypass Canal Alum pumping Treated Inflow and control bldg. Treatment System Discharge 10 cfs Lake Seminole 25 ft. First system which is totally Floc collection automated system – discharge to sanitary sewer Cross-section of Treatment System
Bypass Canal Floc Collection Trough Pump/Control Building Water Pumped Level Inflow Control Weir Floc Collection Piping Inflow Portion of Floc Collection Trough Floc Collection System Floc Pumped to Sanitary Sewer PLC Pump and System Controller Floc collection Control Valve
Aluminum Solubility After addition of alum, the concentration of dissolved aluminum is regulated by the pH of the treated water – Minimum solubility of dissolved aluminum occurs in the pH range of 5.5 – 7.0 Solid – If the pH of the treated phase water is in this range, Area of dissolved aluminum solubility < 100 ppb will be minimal – Diss. Al concentrations generally decrease after treatment 7.2 5.7
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