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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
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.
February 24, 2004 3
Local Limits Development Requirements
• Management support
• Stakeholder involvement
• Adequate resources
• Work Plan
• RWQCB involvement
• Continuous process
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
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
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)
February 24, 2004 7
Data CollectionStandard Approach
• Sampling – Flow proportional composite– Time composite– Grab
• Sample Analyses and Quality Assurance
• Flow Information
February 24, 2004 8
Sample Locations
• Domestic• Commercial• Industrial Users• Plant Process and
Removal • Waste Haulers• Source Water
February 24, 2004 9
Sample LocationsPractical Considerations
• Domestic– Representative– Sufficient flow– Over a weekend
• Commercial– Same considerations as above
February 24, 2004 10
Sample LocationsPractical Considerations (continued)
Industrial Users• Research before you
sample• Categorical Industrial
Users
• Significant Industrial Users
February 24, 2004 11
Sample LocationsPractical Considerations (continued)
Treatment Plant(s)• More than one • Hydraulic detention
time • Proper sample
locations • Sludge sample
collection
February 24, 2004 12
Sample LocationsPractical Considerations (continued)
Waste Haulers– Significant
loading?– Sample collection
technique– Different set of
local limits?
February 24, 2004 13
Sample LocationsPractical Considerations (continued)
Source Water– Different sources – Changes over time
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
February 24, 2004 15
Sample AnalysesPractical Considerations
• New/modified test techniques
• Minimum number of samples
• Electronic data
• Duplicate samples analyzed by two laboratories
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
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?
February 24, 2004 18
MAHL and MAIHL Calculations
• Mass Balances– Collection System = Headworks– Headworks = Plant Effluent and Sludge
• Safety factor
• Growth factor
February 24, 2004 19
Mass BalancesPractical Considerations
Headworks data are the fulcrum point for mass balances
Industrial Waste Residential Commercial
EffluentSludge
Headworks
February 24, 2004 20
Headworks Mass Balance
IW + RES + COM = Headworks
• Effect of collection system operations
• No commercial samples
• Headworks data versus plant removal
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
February 24, 2004 22
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
February 24, 2004 23
Safety and Growth Factors
• Safety factor– Data variability– Slug loads– Plant performance
• Growth factor– Pollutant specific– Domestic/commercial – Industrial
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
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
February 24, 2004 26
Allocation Practical Considerations
• Are limits technically achievable?
• Can compliance be determined?
• Do limits reflect actual conditions?
February 24, 2004 27
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
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
February 24, 2004 29
Continually Improving LL
Existing Load
New POC
Sample Calculate
CompareMAHL
February 24, 2004 30
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)
February 24, 2004 31
Local Limits Calculations – Methodologies for Development
QUESTIONS?
California Water Environment Association
P3S Annual Conference