Presentation on theme: "Engineers scientists architects constructors Case Study UV Disinfection Interference From Industry MWEA Industrial Pretreatment Seminar October 24, 2007."— Presentation transcript:
engineers scientists architects constructors Case Study UV Disinfection Interference From Industry MWEA Industrial Pretreatment Seminar October 24, 2007 Jack D. Fraser City of Big Rapids Jerald O. Thaler, P.E. Fishbeck, Thompson, Carr & Huber, Inc.
engineers scientists architects constructors AGENDA The UV Interference Mystery Transmittance Local Limit Development Summary Questions
engineers scientists architects constructors The UV Interference Mystery
In 2002, Nestle Waters North America opened a major pumping and bottling facility in Stanwood, Michigan. Facility has 145 employees, 80% live within 30 miles. Produces Ice Mountain ® bottled water and Pure Life ® (“Splash”) fruit-flavored water. Wastes originally trucked to Grand Rapids area. Background
WWTP operational problems with aging UV disinfection system. –Periodic fecal coliform violations. –Preliminary engineering began for a new system. City received inquiries about accepting “clean” process wastes from Stanwood facility. –Previous policy - not to accept hauled waste. –Expected monthly revenue to City - up to $25,
City performed characterization of process wastes from Stanwood facility. In June, City granted approval and trucking of wastes to WWTP began. Construction of replacement UV system started in July Periodic fecal coliform violations continued.
Fecal coliform violations continued, even after start- up of new UV system. MDEQ initiated formal enforcement action. Aggressive investigations into cause: –Transmittance testing of effluent and each truckload. –Operators noted color/odor changes in trucked waste and at WWTP headworks. –Evaluation of Stanwood facility raw materials by Mr. Michael Goergen of Merit Laboratories, Inc. 2006
Investigations indicated cause of interference was potassium sorbate: –Natural preservative, commonly used in foods. –Additive in Splash fruit-flavored water product. –Absorbs UV at approximately same wavelength as is optimum for microorganism deactivation. Question - How to control… Mystery Solved
engineers scientists architects constructors Development of Local Limit for Transmittance
Option 1 – Chemical-Specific Local Limit –Not directly correlated to observed interference. –Testing issues Turnaround time Cost Control Mechanism for Potassium Sorbate
Control Mechanism for Potassium Sorbate (cont’d) Option 2 – Transmittance Local Limit –Direct correlation to observed interference. –Straightforward testing. –But… No experience or EPA/MDEQ guidance on developing transmittance local limit.
General Methodology for Local Limit Development 1.Calculate maximum allowable headworks loading (MAHL): –Pass-through –Sludge Quality –Inhibition 2.Calculate domestic/background loading (L BKGD ). 3.Calculate maximum allowable industrial loading (MAIL): MAIL = MAHL*(1-SF) - L BKGD 4.Allocate MAIL among significant industrial users (SIUs).
Transmittance Definition of transmittance (T): where:I = intensity of UV light leaving sample I o = intensity of UV light entering sample Not concentration-proportional; not additive. Not adaptable to mathematical manipulation.
Absorbance Related parameter, absorbance (A), is related to T by Beer’s Law: or Both concentration-proportional and additive Adaptable to mathematical manipulation
Proposed Calculation Procedure 1.Assume effluent absorbance (A EFF ) is additive from: –Residual effluent total suspended solids (TSS): –Pass-through of background sources: –Pass-through of trucked waste source:
Proposed Calculation Procedure 2.Assume A EFF maintained at or below maximum value (AMAX EFF ) less safety factor (X SF ): 3.Calibrate parameters using site-specific data, then solve above equations for A SIU. 4.Transpose A SIU to T SIU :
Site–Specific Calibration Δ TSS
Site–Specific Calibration (cont’d) A BKGD *(1-R BKGD /100)
Site–Specific Calibration (cont’d) AMAX EFF
Site-Specific Parameters R SIU Data showed lower A at higher trucked waste volume, but effluent remained relatively constant.
Site-Specific Parameters (cont’d) R SIU decreased at higher trucked waste volume:
Results Solving for A SIU and transposing to T SIU produced family of curves for local limit:
Results (cont’d) Permit negotiations between City and Nestle Waters led to following permit conditions: –No acceptance if TSS EFF exceeds 15 mg/L. –Maximum Q SIU of 120,000 gal/day. –Minimum transmittance of 70%.
Summary “Clean” waste caused interference in this case. For T limit, use general methodology based on A. Must specify both TSS EFF and Q SIU to set limit. Lessons learned: –You never know what you will get with trucked waste. –Use all your resources to maximize knowledge. –Get it in writing before it happens. –Permit the discharger, not the transporter.