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Local Limits Crash Course

Gorman Lau, P.E.

CWEA 2016 P3S Conference February 29, 2016

Presentation Outline Background Local limit evaluations Local limits update/development Local limits implementation Local limits troubleshooting Summary and Q/A

2

Why have a Pretreatment Program? Protect POTW from interference or upset of

treatment operations Prevent pass-through of pollutants Prevent harm to POTW infrastructure Protect biosolids quality Protect public health and safety

3

Who must have a Pretreatment Program?

Defined in 40 CFR Part 403

POTWs with design flow > 5 mgd

POTWs with design flow ≤ 5 mgd Directed by

regulatory agency

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What is required for Pretreatment Program? Pretreatment Program Documents Administrative procedures Sewer Use Ordinance (SUO)/Legal Authority

General and specific prohibitions Categorical limits Local limits

Enforcement Response Plan (ERP) Wastewater discharge permits/control mechanism

Program approved by Regional Water Board

5

What are general and specific prohibitions? Narrative discharge limits General prohibitions – no discharge of pollutants

causing pass-through or interference Specific prohibitions – characteristics of wastewater

that cannot be discharged into collection system (e.g., pH, temperature, fire/explosive hazards)

Required by 40 CFR Part 403.5 Example language in USEPA Model Sewer Use

Ordinance

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What is a categorical limit? Effluent limits for industrial processes Regulates specific discharges from 35 industries Concentration- or mass-based Applied at end-of-process typically at end of

pretreatment system Required by 40 CFR Parts 405-471

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What is a local limit? Technically-based effluent limit for industrial (or

other regulated) users Concentration- or mass-based Applied at end-of-pipe

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Pollutant Pie

Background (non-regulated)Regulated

Growth

Hauled Waste

Safety Factor

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Categorical vs. local limits

Discharge to

collection system

Regulated process

wastewater

Non-regulated process

wastewater

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Categorical limits

Local limits


Discharge to

collection system

Regulated process

wastewater #1

Regulated process

wastewater #2 Non-

regulated process

wastewater

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Categorical limits

Local limits


Discharge to

collection system

Regulated process

wastewater

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Categorical & Local limits

What is a local limit? Technically-based effluent limit for industrial (or

other regulated) users Concentration- or mass-based Applied at end-of-pipe

Required by 40 CFR Part 403.5 Guidance documents Local Limits Development Guidance (July 2004) Local Limits Guidance (December 1987)

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Why do you need local limits? Protect POTW Infrastructure Treatment process integrity Final effluent quality (meet

discharge requirements) Biosolids quality

Protect human health and safety

Protect the environment

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Applicability of restrictions Restriction Categorical

Industrial User Significant

Industrial User Other Industrial

Users General and specific prohibitions X X X

Categorical limits X Local limits X X *

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* Local limits may apply

Life cycle of local limits Update/Develop

Local Limits

Implement Local Limits

Evaluate Local Limits

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Update/Develop 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 things change? Treatment plant upgrades Treatment process modifications Wastewater/biosolids quality Wastewater discharge effluent limits Biosolids handling/disposal Regulated user base Water supply

19

What do you want to get out of a local limits evaluation? Verify existing pollutants of concern Identify new pollutants of concern Assess existing data quantity and quality Gain an understanding of the pollutant loadings

to the treatment plant Magnitude Temporal variations/trends

Determine next steps, if necessary

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How do you conduct a local limits evaluation? Identify pollutants of concern (POCs) Compare recent influent pollutant loads with the

Maximum Allowable Headworks Loading (MAHL) for each pollutant

Conduct compliance analysis Document the evaluation

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Where do you find 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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How do you compare influent loads to MAHLs? Local Limits Guidance thresholds Average influent load > 60 percent of MAHL Maximum influent load > 80 percent of MAHL Monthly average influent load > 80 percent of design

capacity for BOD, TSS, or ammonia Other thresholds If any threshold exceeded, re-evaluate local limit If threshold not exceeded, is a local limit

necessary?

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What is a 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


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




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How do you update/develop local limits? Identify applicable operational/environmental

restrictions Review and collect relevant data Conduct screening Conduct headworks loading analysis Calculate removal efficiencies Calculate MAHLs

Calculate maximum allowable industrial loadings (MAILs) local limits

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What operational/environmental restrictions to consider? Treatment plant design capacities Treatment process inhibition

levels Activated sludge Nitrification Trickling filters Anaerobic digestion

Effluent limits Biosolids limits Air quality standards

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What is the secret to local limits update/development?

HIGH QUALITY SITE-SPECIFIC DATA!!!

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POTW

EFFNPDESNPDES R

QCAHL ××=

34.8

PE

PEASAS R

QCAHL ××=

34.8

POTW

sldgsldgsldgsldg R

GQPSCAHL

××××=

34.8

Is it really that important?

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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

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 = Data locations 32

X

Why do you need a Sampling and Analysis Plan (SAP)? Goal: Produce high quality scientifically-

defensible data that adequately characterizes the site-specific conditions Uncontrollable loads Treatment plant removal efficiencies Biosolids quality

Outline all information related to sampling and analysis activities

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What goes into a SAP? Sampling locations Pollutants of concern Sampling frequency Types of samples Analytical requirements Quality assurance/quality control (QA/QC)

procedures

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Where to potentially sample? Collection system POTW influent Between treatment processes Final effluent Anaerobic digester Biosolids to disposal

35

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 = Potential sampling locations 36

How do you select a collection system sampling site? Presence of regulated dischargers Types of commercial businesses present Will commercial businesses be regulated?

Size of the service area Variability of flows, pollutant concentrations and

loadings Multiple drinking water sources Presence of inflow/infiltration Separate or combined sewer system

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Conduct Site Visit Identify sampling locations Gain appropriate access/

permission Identify potential safety

hazards Determine equipment needs

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What do you sample for? 15 National POCs 11 metals (As, Cd, Cr, Cu, Pb, Hg, Mo, Ni, Se, Ag,

Zn) Cyanide BOD, TSS, ammonia

Other POCs identified in local limits evaluation Effluent/biosolids limits Treatment process inhibition

Tailor POC sampling/analysis efforts to sampling location-specific needs

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Minimum Recommended Sampling Frequency (Initial)

Parameter POTW Influent

POTW Effluent

POTW Biosolids

Collection System

Organic Priority Pollutants 1-2 1-2 1 1-2

National POCs 7-14 7-14 2 7 POTW-specific POCs 7-14 7-14 2 7

Percent solids (biosolids) – –

2 –

TCLP pollutants – – 1 – Source: 2004 Local Limits Guidance

Minimum Recommended Sampling Frequency (Ongoing)

Parameter Location < 5 MGD 5-10 MGD 10-50 MGD >50 MGD

Pollutants with local limit


Quarterly Quarterly Quarterly Every other month

Pollutants with MAHLs, but no local limit


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

When do you sample and how much is needed? Key considerations for when Collect samples during typical operational periods Do not sample during/after precipitation events when

inflow/infiltration flows are high Avoid holidays, but capture weekend days as well

Key considerations on how much Depends on local limits evaluation and identification

of data gaps Availability of high-quality historic data Ideally supplement historic data

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How are samples collected? Composite samples Flow-weighted (preferred) Time

Grab samples Consider hydraulic

residence time

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What analytical information to include in SAP? Sample bottle requirements Bottle size and material Preservatives Ice/refrigerate samples to <6°C

Hold times Analytical methods 40 CFR Part 136

Detection limits

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How important are detection limits? Excessive non-detect

data can be difficult to use when calculating local limits

Recommend lowest detection limits possible

DNQ data provides more information than non-detect 45

Reporting Limit (RL)

Method Detection Limit (MDL)

Detected

Detected but not

quantifiable (DNQ)

Non-detect

What QA/QC should be implemented? Clean sampling Field controls Laboratory controls Sample chain-of-custody Field logs

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What needs to be on sample chain-of-custody form? Contact information Date and time Double-check sample bottle counts and types Identify analytical methods Request low detection limits at MDLs Request DNQ data

Request QA/QC analyses Comments Signatures

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What do you do with all these new data? Check QA/QC data for precision, accuracy,

adequacy, and hold times Look for aberrant data (outliers) Check measurement units Request re-analysis Conduct re-sampling

Conduct mass balance checks

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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

nProbability

How to handle non-detect data? Non-detect data must be carefully assessed How much of data set is non-detect? Were detection limits appropriate?

Use a surrogate value Detection limit One-half detection limit Zero

Use statistical methods (e.g., regression on order [ROS])

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Do you need a headworks loading analysis? 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

50 Source: 1987 Local Limits Guidance

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 a minimum 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? Analysis to determine the need for local limits for

each POC evaluated Some POCs should have local limits regardless of

outcome of headworks loading analysis Consider if removal of any local limit may encourage

increased discharge of pollutants

52

How do you calculate removal efficiencies? Concentration-based Local Limits Guidance (2004) 3 methods presented Does not account for flow

53

What are the removal efficiency calculation methods?

Method Definition Advantages Disadvantages ADRE* Paired influent and

effluent data lagged by hydraulic residence time

• More accurate by following plug of water through entire treatment

• Needs at least ten data pairs to be accurate • Does not identify frequency

MRE* Difference of averages of influent and effluent data

• Does not required paired data – more flexible

• Sample collection time bias

Decile Paired influent and effluent data lagged by hydraulic residence time to determine frequency

• Shows how frequently removal efficiency occurs

• Needs at least nine data pairs • Selection of applicable decile

54 * Can be calculated using wastewater or biosolids data for conservative POCs

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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What’s the difference?

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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

How are MAHLs calculated? Use equations to calculate allowable headworks

loading (AHL) using each operational/ environmental restriction Removal efficiencies Operational/environmental restriction Flow

Select lowest AHL MAHL 57

POTW

EFFNPDESNPDES R

QCAHL ××=

34.8

Is there a need for a local limit? 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 Recommend local limits for national POCs (min)

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Example MAHL Calculation

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Instantaneous Max. Discharge Loading Limit lbs/day 164 0.00834*AM5*AM27/(1-AM17)Daily Maximum Discharge Loading Limit lbs/day 66 0.00834*AM5*AM28/(1-AM17)6-Month Median Discharge Loading Limit lbs/day 16 0.00834*AM5*AM29/(1-AM17)Activated Sludge Inhibition Loading Limit lbs/day 54 0.00834*AM4*AM30/(1-AM18)Anaerobic Digestion Inhibition Loading Limit lbs/day 23 0.00834*AM20*AM31/AM17Biosolids 40 CFR Part 503 Loading Limit lbs/day 19 0.000001*AM21*AM32/AM17Biosolids CCR Title 22 Loading Limit lbs/day 484 0.000001*AM21*AM33/AM22/AM17

Allowable Headworks Loading Limits

How do you calculate MAILs?

MAHL = maximum allowable headworks loading SF = safety factor LB = background (non-regulated) pollutant load HW = hauled waste load GA = growth allowance

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( ) )(1 GAHWLSFMAHLMAIL B ++−−×=

All values in lb/day

MAIL portion of pollutant pie

Background (non-regulated)Regulated

Growth

Hauled Waste

Safety Factor

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How to document local limits update/development effort? Selection process for POCs Assumptions and data used Calculations Removal efficiencies MAHLs MAILs

Next steps Public participation Submittal to Regional Water Board for review (and

approval) 62

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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How are local limits implemented? Update Sewer Use Ordinance Implement in wastewater discharge permits Concentration or mass limits allocated from MAIL Four MAIL allocation methods discussed in Local

Limits Guidance Best Management Practices (BMPs)

65

How are MAILs allocated? Uniform limits Discharger contribution-based limits Flow proportion Mass proportion

As-needed loading Creative allocations

66

Whichever method(s) selected, MAIL cannot be exceeded.

What are uniform limits? MAIL is allocated such that all dischargers have

the same concentration limit Advantages Easily administered

Disadvantages Allocates capacity to

dischargers that may not need it

May be overly stringent

67

What are contribution-based limits? Dischargers not contributing pollutant load

assumed to be background and MAIL distributed proportionally to dischargers contributing pollutant load

Advantages Provides MAIL to dischargers that need it

Disadvantages May discourage improvement of effluent quality from

discharger More difficult to administer since limits would be

different from discharger to discharger 68

What are as-needed loading limits and creative allocations? Various flexible options for allocating MAIL to

dischargers to provide capacity to dischargers that need it

May discourage improvement of effluent quality from discharger

More difficult to administer since limits would be different from discharger to discharger

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Use Common Sense Compare regulated

discharger data with proposed local limits

Can discharger meet proposed local limits? If not, determine technical

feasibility of achieving local limit, review discharger data, and/or consider alternative allocation methods

70

Local limits next steps Conduct periodic compliance monitoring Consider developing on-going sampling program

for local limits purposes Collection system Between treatment processes

Re-evaluate local limits periodically

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Local Limits Troubleshooting

72

How to deal with blank contamination? Importance of sample blanks Verify clean sampling techniques or equipment Verify clean analytical techniques

Are sample results > 10x blank result? Yes – data are OK to use without qualification No

Qualify data as non-detect at result level Modify sample result to account for blank contamination

result

73

How to deal with blank contamination? How much of the data are affected? Some – data likely OK to use Lots – consider resampling

Remember that high quality data are needed to accurately characterize wastewater and calculate local limits

74

What if there are negative removal efficiencies? Don’t dismiss them as errant Is this chemical used in the treatment process? Is it a byproduct of treatment? Could be a consequence of sampling

methodology (e.g., hydraulic residence time) Provides another layer of safety in designing

local limits

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What flow to use? Generally use average daily flow over full

calendar years Removal efficiency calculations Pair influent/effluent flows with corresponding

concentrations on sampling date Between processes flow data may not be available

AHL calculations Use corresponding flow data for the operational/

environmental restriction (e.g., influent or primary effluent flow for activated sludge)

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What flow to use? Design flow rate vs. actual flow rate Use actual flow rate to prevent overallocation of

available capacity for POC If actual flow rate used, can ignore growth allowance

factor in MAIL calculation Design flow rate can be used to determine overall

capacity for a POC

77 Photo credit: Environmental Science & Engineering Magazine

What if there’s insufficient available MAIL? How does it happen? Large non-regulated discharger load Low removal efficiencies Safety factor selection

Where do you commonly see it? Cu/Zn nitrification inhibition levels Conventional pollutants (e.g., BOD, TSS, ammonia) Salts (e.g., TDS)

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What if there’s insufficient available MAIL? Cu/Zn Consider using primary treatment effluent data if it is

higher at concentrations that don’t cause upset Conventional pollutants Is treatment plant able to handle current load? Uses capacity which can limit future growth

Might tax equipment designed for higher flows Consider regulating with sewer rate surcharges

79

What if there’s insufficient available MAIL? Salts Impacts ability to recycle water Drought impacts

Groundwater supply

Source identification and reduction Water supply sources Water softeners Laundries

Pollution prevention and public education

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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




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Questions?

Presentation available after conference: www.cwea.org/p3s

Gorman Lau, P.E.

Larry Walker Associates, Inc. [email protected]

(530) 753-6400

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