Presented to: Southern California Alliance of POTWs LOCAL LIMITS METHODOLOGY,, ISSUES,, AND ALTERNATIVES Barbara Sharatz September 25, 2012
Overview of Presentation Background Pollutants of Concern (POCS) Maximum Allowable Headworks Loading (MAHL) Available Industrial Loading (AIL) Allocation Strategies Implementation New Local Limits
Point Loma POTW 301 (h) WAIVER 240 MGD CAPACITY / 165 MGD ACTUAL ADVANCED PRIMARY 4.5 MILES OFFSHORE, 310 ft DEEP 204 Dilution Factor
Team Building Meeting TEAM MEMBERS Consultants EPA Region IX Wastewater Dept Management Laboratory Manager and Supervisors Pretreatment Program Manager and Supervisors PERSONAL WORK STYLES PROJECT GOALS CHARTER / GROUND RULES COMPLAINT RESOLUTION
Project Success Depends Upon Meeting Specific Objectives Protect the POTW Be Technically Based / Defensible Minimize Impact on Industrial Users Be Easy to Administer
Overview of Presentation Background > Pollutants of Concern (POCS) Maximum Allowable Headworks Loading (MAHL) Available Industrial Loading (AIL) Allocation Strategies Implementation New Local Limits
Local Limits are POTW SPECIFIC Meet NPDES permit limits Meet quality requirements for effluent and sludge Protect treatment plant processes Ensure worker health and safety: prevent fume toxicity and explosions
Potential Pollutants of Concern (POCs): PRIMARY REGULATORY NPP: As, Cd, Cr, Cu, CN, Pb, Hg, Ni, Ag, Zn, Mo, Se, BOD 5, TSS, and ammonia (where the POTW accepts ammonia from non domestic sources) Existing Local Limits: As, An, Be, Cd, Cr, Cu, Pb, Hg, Ni, Ag, Zn, CN, ph, G&O, Sulfides, Phenol, Pesticides and PCBs
Potential Pollutants of Concern (POCs): PRIMARY ENVIRONMENTAL Water Quality: NPDES Permit and Ocean Plan Sludge Quality: 40 CFR 503 and California Title 22 Inhibition: PRELIM 5 Benchmarks: Goals in 301 (h) permit = 95% plant performance, 1990 1994 Expressed in metric tons/yr: Convert to [mg/l] ~1/100 NPDES permit limits
Screening to ID POCs MAXIMUM POTW INFLUENT AND EFFLUENT VALUES: Influent > Effluent Criteria? Effluent > 1/2 Effluent Criteria? Sludge > 1/2 Sludge Criteria? Influent > 1/4 Inhibition Criteria RESULTS: 31 Pollutants of Concern Controlling Criteria = Benchmarks
SECONDARY POCs ND, and; Detection limit > screening criteria, and; Found in IU discharge samples or chemical inventory lists
Pollutant Sources SIU Industrial users Commercial users Residential / domestic users Trucked Industrial and Domestic Waste Upstream WRPs and WTPs discharging gsludge Metro Biosolids Center centrate return stream Water Supply & Distribution System Inflow /Infiltration Navy shipboard wastes
Data handling Issues: Background Data Goal: Characterize variability and reduce effect of outliers and non detects 1. Selection of statistical methods considers measure of variability 2. Conventions for outliers 3. Conventions for non detects
Select Representative Background Concentrations
46.9 Example: Arsenic 75 samples 49 below MDL Concentration Range: < 45 ug/l to 2200 ug/l Benchmark = 3.0 30 ug/l Concent tration (ug g/l) 2500 2000 1500 1000 500 0 Sample Number
Variability Strongly Affects Statistical Measures 2nd Decile Median Average 0 100 200 300 Concentration (ug/l) Example Arsenic: NDs are assumed as ½ MDL Which value is representative of background?
Example: Molybdenum 75 Samples 71below MDL Concentration Range: <15 ug/l to 150 ug/l Cit Criteria i = 2.7 27 ug/l Con ncentratio on (ug/l) 200 150 100 50 0 Sample Number
NDs increase uncertainty, especially where DLs are higher than criteria NDs = DL MDL NDs = 0.5 DL NDs = 0 0 5 10 15 20 Average Concentration (ug/l) Example Molybdenum: which value is representative of background?
For Background Loadings Use Average Values For NDs: If Zero Detects, ND = 0 If > 1 Detect, ND = 0.5 MDL If 1 Detect, Is value > 2X MDL? Yes = slug, ND = 0 No = value, ND = 0.5 MDL
Source Characterization Sampling Results from Sources Projected Flow Rates Controllable Loading Ship s Waste Uncontrollable Loading I / I SLUDGE CENTRATE
Safety Factor High Safety Factor => Expensive Pretreatment Low Safety Factor => NPDES Fines and Process Upsets
Safety Factor Approach Strives to Minimize Number of Unknowns Safety Allowance Allowable Headworks Loading
Growth Safety Allowance Allowable Headworks Loading Safety Allowance Influent Loading Time
Safety Factor Approach Addresses Analytical Uncertainty for Special Cases Allowable Headworks Loading Safety Allowance Influent Loading Time Date Concentration 1/2/96 <DL 1/4/96 0.003 1/6/96 0.002 Detection Level 0.002 Concentrations at or Concentrations at or Near Detection Level
Safety Factor Predicts Capacity Needs for Future Growth Waste water Flow Industrial Industrial Time Mature Service Area Time Growing Service Area Experience Shows Safety Factor for Growth Varies from 0-5%
Safety Factor Approach Develops Fair and Protective Safety Allowance Safety Allowance Allowable Headworks Loading
3 Groups of POCs Highbackground, high influent Variable influent, variable background Low influent, low background
Overview of Presentation Background Pollutants of Concern (POCS) >Maximum Allowable Headworks Loading (MAHL) Available Industrial Loading (AIL) Allocation Strategies Implementation Results
Maximum Headworks Loading Calculations PLANT REMOVAL EFFICIENCIES Outliers: 99% confidence interval IF NDs: Used Paired Data Sets Literature Values USEDPRELIM5 5.0 FOR MAHL CALCS
Maximum Allowable Headworks Loading Protects Most Sensitive Criteria Allowable Headworks Loading = Criteria x Projected Plant Flow (1- Removal Efficiency) NICKEL NPDES CA Title 22-Sludge U.S. 503 - Sludge Anaerobic Inhibition Threshold Benchmark 50 100 150 500 3000 AHL (lb/d) MAHL
Overview of Presentation Background Pollutants of Concern (POCS) Maximum Allowable Headworks Loading (MAHL) > Available Industrial Loading (AIL) Allocation Strategies Implementation Results
AIL Remains after Uncontrollable Loading and Safety Allowance are Removed Nickel Example Domestic/Commercial Loading 7.5 lb/d Other Uncontrollable Loading 4.8 lb/d Total Pie = 68.2 lb/d MAHL Available Industrial Loading (AIL) 56 lb/d (MAHL based on Benchmark)
Overview of Presentation Background Pollutants of Concern (POCS) Maximum Allowable Headworks Loading (MAHL) Available Industrial Loading (AIL) > Allocation Strategies Implementation Results
Conventional Allocation Strategies are Simple But Can be Restrictive Uniform Concentration Method AIL UCL = Flow UCL = 1.4 mg/l Flow Industries
Conventional Allocation Strategies are Simple But Can be Restrictive Uniform Concentration Method Contributory Flow Method All Industries Contributing Industries AIL UCL = Flow Industries UCL = 1.4 mg/l AIL Loading Non-Contributing CFL = Flow Contributers CFL = 5.2 mg/l
Characterization of SIUs Provides Opportunities for Modified Allocation Conventional CFL 5.2 mg/l -------------- -------------- 2.38 mg/l Monthly Average Nickel 2.82 mg/l Unused 802 8.02 5.2 mg/l Categorical Metal Finishers Non-Categorical Industrial Laundries Trucked Industrial
Modified CFL Allocates Remaining Loading Among Contributing, Non CIU Industries Sum Flow Rates Of Contributing Non CIU Industries Calculate Modified CFL
Overview of Presentation Background Pollutants of Concern (POCS) Maximum Allowable Headworks Loading (MAHL) Available Industrial Loading (AIL) Allocation Strategies > Implementation Results
Nickel Example CFL Modified = AIL Loading CIU Loading Non Contributing Non CIUs Flow Contributing Non CIUs CFL Modified = ( 56.0 ) lb/d ( mgd) (8.34)
Federal Discharge Limit Determines CIU Loadings Determine representative flow rate per sewer connection Assign Federal Discharge Limit for Pollutant Nickel Example: Loading CIU = (Flow) CIU * (Limit) = 20.5 lb/d (Limit) Federal
Nickel Example CFL Modified = AIL Loading CIU Loading Non Contributing Non CIUs Flow Contributing Non CIUs CFL Modified = ( 56.0 20.5 ) lb/d ( mgd) (8.34)
Average Domestic Concentration Determines Non Contributing, Non CIU Loading Sum Flows of Non Contributing Non CIUs Apply Average Domestic Concentration Nickel Example: Loading = (Flow) X (Concentration) Non Contributing Non Contributing Domestic = 0.14 lb/d
Nickel Example CFL Modified = AIL Loading CIU Loading Non Contributing Flow Contributing Non CIUs CFL Modified = ( 56.0 20.5 0.14 ) lb/d ( mgd) (8.34)
Nickel Example CFL Modified = AIL Loading CIU Loading Non Contributing Non CIUs Flow Contributing Non CIUs CFL Modified = ( 56.0 20.5 0.14 ) lb/d = 13 mg/l ( 0.32 mgd) (8.34)
Overview of Presentation Background Pollutants of Concern (POCS) Maximum Allowable Headworks Loading (MAHL) Available Industrial Loading (AIL) Allocation Strategies > Implementation Results
Modified CFL Significantly Increased Allowable Concentration to Contributing Non CIUs NICKEL tration (m mg/l) Concen 14 12 10 8 6 4 2 0 14 1.4 UCL 5.2 Conventional CFL 13 San Diego Modified CFL
Modified CFL Provided Greater Flexibility for All Metals 80 Conce entration (mg/l) 70 60 50 40 30 20 10 0 Modified CFL Conventional CFL Cadmium Chromium Copper Lead Nickel Zinc
LOCAL LIMIT EVALUATION RESULTS Eliminate Antimony Arsenic Beryllium Mercury Selenium Thallium Silver Phenols Pesticides / PCBs
Convention OLD New Limits POLLUTANT OLD LIMIT (mg/l) NEW LIMIT Screening Level Control Criteria Cadmium 1.2 3.8 0.009 B Chromium 7 59 0.016 B Copper 4.5 11 0.16 B Cyanide 1.9 1.9 1.9 B Lead 0.6 73 0.036 B Nickel 4.1 13 0.015 B Zinc 4.2 24 0.3 B Flash Point >140 >140 >140 H&S Oil & Grease 500 500 500 NPDES Sulfides 1 1 1 H&S ph 5.0-11.0 5.0-12.5 TITLE 22
San Diego Modified CFLs are Less Restrictive, Easy to Administer Allows full federal discharge limit for CIUs Provides greater allocation to contributing, non CIUs Permits with Federal Limits unchanged
REFERENCES 1. City of San Diego Urban Area Pretreatment Program Final Report prepared by Malcolm Pirnie, Inc., 1996 2. WEF Presentation prepared by Malcolm Pirnie, Inc. and the City of San Diego, 1996 3. EPA Guidance Manual on the Development and Implementation of Local Discharge Limitations Under the Pretreatment Program, December 2004 4. Residential and Commercial Toxic Pollutant Loadings and POTW Removal lefficiency i Estimation, i May 1991