how to conduct a local limits evaluation · what is a local limit? technically-based water quality...
TRANSCRIPT
How to Conduct a Local Limits Evaluation
Gorman Lau, P.E.
CWEA Northern Regional Training Conference September 9, 2015
Presentation Outline Background Pollutants of Concern (POCs) Pollutant Screening Headworks Loading Analysis Compliance Analysis Summary
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What is a local limit? Technically-based water quality effluent limit for
industrial (or other regulated) users Concentration- or mass-based End-of-pipe limit Different from categorical effluent limit
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Pollutant Pie
Background (non-regulated) Regulated Safety Factor
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What is a local limit? Technically-based water quality effluent limit for
industrial (and other regulated) users Concentration- or mass-based limit End-of-pipe limit Different from categorical effluent limit
Required by 40 CFR Part 403 (Pretreatment Program) and/or discharge permit Local Limits Development Guidance (July 2004) Local Limits Guidance (December 1987)
Incorporated into Sewer Use Ordinance 5
Why do you need local limits? Protect wastewater collection/treatment system Infrastructure Treatment process integrity Final effluent quality (meet discharge requirements) Biosolids quality
Protect human health and safety Protect the environment
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Life cycle of local limits Implement Local
Limits
Evaluate Local Limits
Develop/Update Local Limits
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Why conduct a local limits evaluation? It may be required: Pretreatment compliance inspection (PCI) Pretreatment compliance audit (PCA) Discharge permit
Things change over time Local Limits Guidance recommends periodic
evaluations
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What do you want to get out of a local limits evaluation? Verify existing pollutants of concern (POCs) Identify new POCs Assess existing data quantity and quality Gain an understanding of the pollutant loadings
to the treatment plant Magnitude Temporal variations/trends
Identify compliance issues Determine next steps, if necessary
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How do you conduct a local limits evaluation? Identify potential POCs Compare recent influent loads of pollutants with
the Maximum Allowable Headworks Loadings (MAHLs) for each pollutant Local Limits Guidance thresholds Is a local limit necessary?
Conduct a compliance analysis Treatment plant discharge requirements Regulated dischargers’ compliance with local limits
Document the evaluation 10
Where do you find potential POCs? Existing local limits 2004 Local Limits Guidance 15 national POCs Appendix C: Pollutants Regulated by Categorical
Standards Appendix G: Literature Inhibition Values
Discharge permits Biosolids limits Treatment design capacities
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Non-regulated
dischargers
Regulated dischargers
Headworks Primary Treatment
Secondary Treatment
Tertiary Treatment
Disinfection
Effluent
Biosolids Processing Disposal
X X
X
X
X
X X
X = Critical data locations X = Ideal additional data locations
What data do you need?
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X
What do you do with these data? Goal: DEVELOP HIGH QUALITY DATA SET!!! Check QA/QC data for precision, accuracy,
adequacy, and hold times Look for aberrant data (outliers) Non-detect data Use surrogate values (detection limit, ½ detection
limit, 0) Use statistical methods
13 100
150
200
250
300
350
.01 .1 1 5 10 20 30 50 70 80 90 95 99 99.9 99.99
Con
cent
ratio
n
Probability
1987 Local Limits Guidance Screening Criterion 1: Max [Ceff] > ½ water quality
criterion/standard, or Max [Cbiosolids] > ½ applicable biosolids criterion; or
Criterion 2: Max grab [Cinf] > ½ inhibition level; or Criterion 3: Max composite [Cinf] > ¼ inhibition
level; or Criterion 4: Max [Cinf] > 1/500th of applicable
biosolids criterion
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What are the potential outcomes of the screening step? No criteria met analysis complete, headworks
loading analysis not needed Consider headworks loading analysis for national
POCs At least one criterion met conduct headworks
loading analysis Insufficient data may need to conduct
additional sampling to evaluate
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What is a headworks loading analysis? Comparison of influent POC loads to MAHL Average influent load > 60% of MAHL Maximum influent load > 80% of MAHL Monthly average influent load for BOD, TSS,
ammonia > 80% of design capacity (prior 12 months) Consider evaluating data on a 12-month basis to
identify influent load trends for POCs If at least one criterion is met, local limit for POC
needs to be updated/developed
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Where do you find an MAHL? Prior local limits studies Develop preliminary MAHL if data available Identify data gaps and collect additional high
quality site-specific data if needed
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POTW
EFFNPDESNPDES R
QCAHL ××=
34.8
PE
PEASAS R
QCAHL ××=
34.8
POTW
sldgsldgsldgsldg R
GQPSCAHL
××××=
34.8
How do you calculate removal efficiencies? Concentration-based Local Limits Guidance (2004) 3 methods presented Does not account for flow
Load-based Accounts for flow variation
Provides credit for recycled water
Use similar calculation methods for concentration-based
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How important is high quality site-specific data?
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Pollutant USEPA (2004)
Plant A (2012)
Plant B (2013)
Plant C (2014)
Plant D (2015)
Arsenic 11-78% 41% 7% 35% 47% Cadmium 25-99% 90% 78% 92% 94% Chromium 25-97% 86% 74% 89% 84% Copper 2-99% 85% 54% 91% 92% Lead 1-92% 95% 76% 95% 95% Mercury 1-95% 99% 74% 97% 99% Nickel 2-99% 19% 14% 61% 53% Silver 17-95% 95% 62% 96% 98% Zinc 23-99% 88% 31% 82% 95% Cyanide 3-99% -14% -170% -640% 58%
Activated sludge treatment plant average removal efficiencies
What’s the difference in removal efficiency calculations?
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Pollutant Plant E
(20% water recycling) Plant F
(50% water recycling) Conc. Load Conc. Load
Arsenic 25% 36% -4% 47% Cadmium 89% 90% 90% 94% Chromium 66% 71% 70% 84% Copper 93% 94% 85% 92% Lead 95% 96% 91% 95% Mercury 99% 100% 98% 99% Nickel 32% 42% 10% 54% Silver 96% 96% 96% 98% Zinc 70% 75% 89% 95%
Removal efficiencies based on Mean Removal Efficiency Method
Compliance Analysis Is treatment plant meeting
discharge limitations? Is treatment plant meeting
biosolids disposal limits? Have there been treatment plant
upsets? Are regulated dischargers
complying with local limits? Do they need more flexibility?
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What are the potential outcomes of a local limits evaluation? Confirm existing local limits are adequate Propose removal an unnecessary existing local limit
Focus next steps/future effort Identify data gaps and additional sampling that may
be needed to complete the evaluation or update/develop local limits
Consider implementing ongoing monitoring program Document results of evaluation
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Minimum Recommended Sampling Frequency (Ongoing)
Parameter Location < 5 MGD 5-10 MGD 10-50 MGD >50 MGD
Pollutants with local limit
Influent, Effluent, Biosolids
Quarterly Quarterly Quarterly Every other month
Pollutants with MAHLs, but no local limit
Influent, Effluent, Biosolids
Annually Semi-annually
Semi-annually Quarterly
Organic priority pollutants Influent Annually Annually Annually Semi-
annually TCLP pollutants Biosolids Annually Annually Annually Annually Biosolids % solids and specific gravity
Biosolids Semi-annually
Once every 4 months
Quarterly Every other month
Source: 2004 Local Limits Guidance
Are there substantial changes (40 CFR Part 403.18)? Substantial change Relaxation of local limits (including removing local
limits) Reallocation of existing MAIL is not substantial Must receive Regional Water Board approval before
implementation Non-substantial change Notify Regional Water Board at least 45 days before
implementation
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Summary Local limits are required for Pretreatment
Programs Local limits need to be periodically reviewed,
evaluated, and updated Site-specific high quality data are needed Site-specific high quality data are needed Develop an adaptive management approach to
make this process as self-sufficient as possible
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Local limits are an ongoing process
Implement Local Limits
Evaluate Local Limits
Develop/Update Local Limits
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