Local Limits Calculations – Methodologies for Development
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Local Limits Calculations – Methodologies for Development
February 24, 2002
Presented by
Rich von Langen and John W. Hart
California Water Environment AssociationP3S Annual Conference
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February 24, 2004 2
Presentation Overview
Summarizes local limits development highlighting the standard approach and including practical considerations based on EPA guidance documents and experience.
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February 24, 2004 3
Local Limits Development Requirements
• Management support
• Stakeholder involvement
• Adequate resources
• Work Plan
• RWQCB involvement
• Continuous process
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February 24, 2004 4
Local Limits DevelopmentStandard Approach
• Determine POC
• Collect data
• Analyze data
• MAHL and MAIHL calculations
• Allocation IU local limits
• Local Limits adoption and approval
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February 24, 2004 5
Pollutants of ConcernStandard Approach
• 15 Pollutants
• Pollutants in discharge permits
• Sludge disposal regulations
• Review of IU discharge data
• Identified pass-through or interference pollutants
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February 24, 2004 6
Pollutants of ConcernPractical Considerations
• EPA specific evaluation criteria• Does IU discharge the POC? • Pretreatment Program versus
Source Control Program• Keep It Simple Sam (KISS)
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February 24, 2004 7
Data CollectionStandard Approach
• Sampling – Flow proportional composite– Time composite– Grab
• Sample Analyses and Quality Assurance
• Flow Information
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February 24, 2004 8
Sample Locations
• Domestic• Commercial• Industrial Users• Plant Process and
Removal • Waste Haulers• Source Water
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February 24, 2004 9
Sample LocationsPractical Considerations
• Domestic– Representative– Sufficient flow– Over a weekend
• Commercial– Same considerations as above
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February 24, 2004 10
Sample LocationsPractical Considerations (continued)
Industrial Users• Research before you
sample• Categorical Industrial
Users
• Significant Industrial Users
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February 24, 2004 11
Sample LocationsPractical Considerations (continued)
Treatment Plant(s)• More than one • Hydraulic detention
time • Proper sample
locations • Sludge sample
collection
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February 24, 2004 12
Sample LocationsPractical Considerations (continued)
Waste Haulers– Significant
loading?– Sample collection
technique– Different set of
local limits?
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February 24, 2004 13
Sample LocationsPractical Considerations (continued)
Source Water– Different sources – Changes over time
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February 24, 2004 14
Sample Analyses and Quality Assurance
• Standard or Approved Methods
• Minimum Detection Limits–What is needed?–What can be done?– Pre-qualify the laboratories
• Quality Assurance
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February 24, 2004 15
Sample AnalysesPractical Considerations
• New/modified test techniques
• Minimum number of samples
• Electronic data
• Duplicate samples analyzed by two laboratories
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February 24, 2004 16
Flow Information
• Flow proportional sampling
• Minimum flow and monitoring equipment capabilities
• Equalization
• Inflow and infiltration impacts
• Use actual, not design flows
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February 24, 2004 17
Data AnalysesPractical Considerations
• Enough data points?
• The “< MDL” Dilemma—MDL, 50%, or 0?
• Variability-- SD > 20%, NDs
• Organic Total Dissolved Solids
• Any pass-through or interference during sampling events?
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February 24, 2004 18
MAHL and MAIHL Calculations
• Mass Balances– Collection System = Headworks– Headworks = Plant Effluent and Sludge
• Safety factor
• Growth factor
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February 24, 2004 19
Mass BalancesPractical Considerations
Headworks data are the fulcrum point for mass balances
Industrial Waste Residential Commercial
EffluentSludge
Headworks
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February 24, 2004 20
Headworks Mass Balance
IW + RES + COM = Headworks
• Effect of collection system operations
• No commercial samples
• Headworks data versus plant removal
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February 24, 2004 21
MAHL and MAIHL Practical Considerations
• If the mass balance does not balance– Eliminate data > 2SD – Use median versus mean – Balance with ND’s = MDL, X%, and 0
• Note variability for safety factor
• Compare to other data
• Influent concentration vs % removal
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Influent Concentration Impacts on Plant Removal
0%
10%
20%
30%
40%
50%
60%
70%
80%
0 0.05 0.1 0.15 0.2 0.25
Influent Concentration--mg/L
Per
cen
t R
emo
val
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Safety and Growth Factors
• Safety factor– Data variability– Slug loads– Plant performance
• Growth factor– Pollutant specific– Domestic/commercial – Industrial
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February 24, 2004 24
Sensitivity Analysis
• NDs Calculate LL at different ND values; adjust headworks concentration to match mass balance
• Variable Data Eliminate outliers; use median or geometric mean to calculate LL
• Growth Factor Vary; compare to domestic, commercial, and IU contributions
• Allocation Method Total IU flow, pollutant contributory IU flows
• TDS Vary concentrations of source water, and uncontrolled sources
Take a Global Perspective
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February 24, 2004 25
Allocation
• Meet stakeholders objectives• Mass-based • Uniform concentration– All industrial users– Only IU discharging that POC– If LL > CIU limit, allocate excess to
others
• Consistency
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Allocation Practical Considerations
• Are limits technically achievable?
• Can compliance be determined?
• Do limits reflect actual conditions?
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Adoption and Approval
• Local limits draft report
• Stakeholders review
• POTW adoption
• Submit to RWQCB for approval
• Issue when new permit or all at once
• RWQCB may/may not accept LL
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February 24, 2004 28
Annual Review and Re-Evaluationa
• Assess current conditions – Compare MAHLs to current headworks
loadings– Review compliance history
• Collect and analyze data• Recalculate or determine LL• Implement LL
a) Unpublished presentation by Jeff Lape, US EPA
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Continually Improving LL
Existing Load
New POC
Sample Calculate
CompareMAHL
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EPA Resources
• Draft Guidance Manual(www.epa.gov/reg3wapd/pretreatment/pdfs_txt/draftguidance912.pdf)
• Region 8 Draft LL Development Strategy(www.epa.gov/Region8/water/wastewater/prethome/Pret_download/
LLStrategy041103.pdf)
• Region 5 LL Guidance (1995)(www.epa.gov/R5water/npdestek/npdprtg2.htm)
• Region 3 LL Guidance Domestic> MAHL (www.epa.gov/R5water/npdestek/npdprtg3.htm)
• Procuring Analytical Services (www.epa.gov/reg3wapd/pretreatment/pdfs_txt/procur.pdf)
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Local Limits Calculations – Methodologies for Development
QUESTIONS?
California Water Environment Association
P3S Annual Conference