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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
4
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
6
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
7
What is a local limit? Technically-based effluent limit for industrial (or
other regulated) users Concentration- or mass-based Applied at end-of-pipe
8
Pollutant Pie
Background (non-regulated)Regulated
Growth
Hauled Waste
Safety Factor
9
Categorical vs. local limits
Discharge to
collection system
Regulated process
wastewater
Non-regulated process
wastewater
10
Categorical limits
Local limits
Categorical vs. local limits
Discharge to
collection system
Regulated process
wastewater #1
Regulated process
wastewater #2 Non-
regulated process
wastewater
11
Categorical limits
Local limits
Categorical vs. local limits
Discharge to
collection system
Regulated process
wastewater
12
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)
13
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
14
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 *
15
* Local limits may apply
Life cycle of local limits Update/Develop
Local Limits
Implement Local Limits
Evaluate Local Limits
16
Update/Develop Local Limits
Implement Local Limits
Evaluate Local Limits
17
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
18
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
20
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
21
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
22
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?
23
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?
24
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
25
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
Update/Develop Local Limits
Implement Local Limits
Evaluate Local Limits
27
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
28
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
29
What is the secret to local limits update/development?
HIGH QUALITY SITE-SPECIFIC DATA!!!
30
POTW
EFFNPDESNPDES R
QCAHL ××=
34.8
PE
PEASAS R
QCAHL ××=
34.8
POTW
sldgsldgsldgsldg R
GQPSCAHL
××××=
34.8
Is it really that important?
31
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
33
What goes into a SAP? Sampling locations Pollutants of concern Sampling frequency Types of samples Analytical requirements Quality assurance/quality control (QA/QC)
procedures
34
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
37
Conduct Site Visit Identify sampling locations Gain appropriate access/
permission Identify potential safety
hazards Determine equipment needs
38
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
39
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
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
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
42
How are samples collected? Composite samples Flow-weighted (preferred) Time
Grab samples Consider hydraulic
residence time
43
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
44
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
46
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
47
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
48
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])
49
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
51
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
55
What’s the difference?
56
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)
58
Example MAHL Calculation
59
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
60
( ) )(1 GAHWLSFMAHLMAIL B ++−−×=
All values in lb/day
MAIL portion of pollutant pie
Background (non-regulated)Regulated
Growth
Hauled Waste
Safety Factor
61
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
63
Update/Develop Local Limits
Implement Local Limits
Evaluate Local Limits
64
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
69
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
71
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
75
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)
76
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)
78
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
80
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
81
Local limits are an ongoing process
Implement Local Limits
Evaluate Local Limits
Update/Develop Local Limits
82
Questions?
Presentation available after conference: www.cwea.org/p3s
Gorman Lau, P.E.
Larry Walker Associates, Inc. GormanL@LWA.com
(530) 753-6400
83
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