SYSTEMATIC APPROACH TO WATER TREATMENT PLANT PROCESS OPTIMIZATION AND WHY SHOULD SURFACE WATER TREATMENT PLANTS MONITOR UV254 IN SOURCE WATER? Alex Yavich, Ph.D., P.E. Optimization Solutions Environmental, LLC What Will Be Discussed?  Chemical feed rate optimization  Coagulant choice  Rapid and flocculation mixing  UV254 monitoring Chemical Feed Rate Optimization  Ensuring adequate chemical feed rates under all plant conditions is the first step in water plant process optimization  Optimization of chemical feed rates not only improves effluent quality and reduce chemical usage, but also helps identify other potential areas for improvement Coagulation Feed Optimization Optimization goal Computer models can be developed to provide real time advisement to the operators of the optimal chemical feed rates under various plant conditions Case 1 Three Rivers Filtration Plant, Fort Wayne, IN • • Total capacity: 72 MGD Source water: St. Joseph River Case 1: Raw Water Quality Case 1: Treatment train Fe2(SO4)3 Lime Fe2(SO4)3 PAC CO2 Primary Coagulation / Lime Softening Stage Influent Second Coagulation Stage Filtration Effluent Chemical Feed Control at Fort Wayne Plant Case 1: Chemical feed optimization 1 All costs in 2011 chemical prices Optimal Coagulant  Optimal coagulant is the coagulant that best meets plant’s operational goals  By choosing the right coagulant, a water treatment plant can significantly improve its process performance and the quality of finished water What are the Choices?  Metal salts    Turbidity removal through charge neutralization and sweep coagulation of colloidal particles Commonly used coagulants: alum, ferric sulfate, ferric chloride, polyaluminum chloride Cationic polymers   Charge neutralization is major coagulation mechanism Wide range of products available Optimal Coagulant: Major Considerations  Raw water quality: turbidity, pH, alkalinity, NOM etc.  Operational objectives: effluent quality, chemical cost, sludge production, filter run etc.  Plant size  Treatment train: lime softening, UV disinfection etc.  Hardware: flocculators (variable/constant speed), clarifiers (conventional basins, upflow clarifiers, plate settlers etc.), filter configuration (media type, size, support etc.) Case 2 Holland Water Treatment Plant Holland, MI Capacity: 38.5 MGD Source water: Lake Michigan Case 2: Raw Water Quality Raw Water Parameters Temperature, oF Alkalinity, mg/L as CaCO3 Turbidity, NTU Total organic carbon, mg/L UV254, cm-1 Typical Range 32 – 77 100 – 145 0.3 – 40 1.6 – 2.5 0.01 – 0.2 Case 2: Holland WTP Schematic Cl Coagulant Raw water Low lift pump MIxing Chamber Flocculation Basins Settling basins Filters Cl Treated water Clearwell High lift pumps Operational Goal • Alum was historically employed for coagulation • Sludge production was problematic • Goal – reduce sludge production Alternative Coagulants Tested • PACl • Alumer (a premanufactured blend of alum and cationic polymer) • “Seasonal” coagulation practice – Alum: December thru April – Alumer: May thru November Coagulation Computer Models at HWTP Results of Full-Scale Testing and Computer Simulation Analysis • PACl – Sludge could be reduced by up to 45 percent – Cost would increase by appr. 20% – Potential turbidity problems on four Integral Media Support (IMS) cap filters • Alumer – Sludge could be reduced by up to 35 percent – Cost would increase by 5-15% – Not cost effective at increased UV254 • “Seasonal” coagulation practice – Sludge could be reduced by up to 25 percent – No cost increase (compared to alum) – More complex operation Plant’s Best Choice (current practice) Alum and Cationic Polymer (fed separately) • Sludge reduced by up to 35 percent • Expected cost reduction by 25 - 30 percent (compared to alumer) • Consistent filtered turbidity • Improved operational control • Can be optimized to meet plant’s future goals What Affected the Choice of Coagulant at HWTP? • Raw water quality: turbidity and NOM • Operational goals: sludge production, effluent quality, chemical costs • Treatment train: sedimentation basins, filter configuration, feeding equipment Rapid and Flocculation Mixing Coagulant Raw water Low lift pump Mixing Chamber Flocculation Basin Settling basin Mixing Intensity (G-value) G = (P/μV) 1/2 G – velocity gradient, s-1 P – power input, ft·lb/s µ – dynamic viscosity, ft·s/ft2 V – volume, ft3 Rapid and Flocculation Mixing Coagulant Raw water Low lift pump Mixing Chamber Flocculation Basin Settling basin Mixing Time G value, s-1 Rapid mixing 1 – 60 sec 600 - 1500 Flocculation 20 – 30 min 40 - 70 Operation Case 3 St. Joseph Water Filtration Plant St. Joseph, MI Capacity: 12 MGD Source water: Lake Michigan Raw turbidity: 1 – 60 NTU Treatment: Alum coagulation No rapid mixer Case 3: Plant Schematic Cl NaOH Alum Raw water Sludge Low lift pump Drain Accelator Clarifiers (3) Filters Cl Treated water Clearwell High lift pumps Case 3: Rapid Mixing Analysis MIxing time, s G value, s-1 St. Joseph plant (hydraulic mixing in the pipe) 10 - 60 100 - 400 Mechanical mixers (for comparison) 10 - 60 600 - 1000 In-line blenders (for comparison) 0.5 - 1 1000 - 1500 Type Case 3: Computer simulation analysis Case 3: Effect of coagulant mixing Case 4 Holland Water Treatment Plant Holland, MI Capacity: 38.5 MGD Source water: Lake Michigan Case 4: Effect of Flocculation Mixing on Filtered Turbidity Water Quality Monitoring: UV254  UV254 is a measure of ultraviolet absorption at a wavelength of 254 nm  UV254 is a surrogate measure of natural organic matter (NOM) in water Why Should Surface Water Treatment Plants Monitor UV254 in Raw Water? Coagulation Filtration UV254 Clarification Taste and Odor Control DBP control Disinfection Case 5: Effect of UV254 on coagulant demand Lake Michigan Filtration Plant, Grand Rapids, MI Capacity – 130 MGD Source – Lake Michigan Case 6: Effect of UV254 on effluent turbidity South Haven Water Treatment Plant, South Haven, MI Capacity – 4 MGD Source – Lake Michigan UV254 Analysis is Fast and Simple Benefits of UV254 Monitoring  Improved chemical feed control  Consistent effluent turbidity  Reduced chemical costs  Important factor in identifying the “optimal” coagulant  Improved DBP control  Helps optimize UV disinfection Summary  Ensure that chemical feed rates are satisfactory under all plant conditions  Does the plant use the right coagulant?  Verify that rapid mixing operation is adequate  Adjust, if possible, flocculation speed at least seasonally  Implement raw water UV254 monitoring (surface WTPs) Q&A Alex Yavich Ph. (616) 975-0847 E-mail: [email protected] Web: www.osenv.com