local limits calculations – methodologies for development

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



Treatment Plant(s)• More than one • Hydraulic detention

time • Proper sample

locations • Sludge sample

collection



Waste Haulers– Significant

loading?– Sample collection

technique– Different set of

local limits?



Source Water– Different sources – Changes over time


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


Sample AnalysesPractical Considerations

• New/modified test techniques

• Minimum number of samples

• Electronic data

• Duplicate samples analyzed by two laboratories


Flow Information

• Flow proportional sampling

• Minimum flow and monitoring equipment capabilities

• Equalization

• Inflow and infiltration impacts

• Use actual, not design flows


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?


MAHL and MAIHL Calculations

• Mass Balances– Collection System = Headworks– Headworks = Plant Effluent and Sludge

• Safety factor

• Growth factor


Mass BalancesPractical Considerations

Headworks data are the fulcrum point for mass balances

Industrial Waste Residential Commercial

EffluentSludge

Headworks


Headworks Mass Balance

IW + RES + COM = Headworks

• Effect of collection system operations

• No commercial samples

• Headworks data versus plant removal


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


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


Safety and Growth Factors

• Safety factor– Data variability– Slug loads– Plant performance

• Growth factor– Pollutant specific– Domestic/commercial – Industrial


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


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


Allocation Practical Considerations

• Are limits technically achievable?

• Can compliance be determined?

• Do limits reflect actual conditions?


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


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


Continually Improving LL

Existing Load

New POC

Sample Calculate

CompareMAHL


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)


Local Limits Calculations – Methodologies for Development

QUESTIONS?

California Water Environment Association

P3S Annual Conference

local limits calculations – methodologies for development

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