Calculating Numerical Local Limits

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Calculating NumericalLocal Limits
Texas Commission on Environmental Quality Texas
Pollutant Discharge Elimination System
Pretreatment Program
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Overview of Methodology for Developing Local
Limits
Step 1 Develop a Sampling Plan Step
2 Collect Data for Technically Based Local
Limits (TBLLs) Development Step
3 Develop Maximum Allowable Headworks Loadings
(MAHLs) Step 4 Determine Maximum Allowable
Industrial Loading (MAIL) Step 5 Account
for Required Best Management Practices
(BMP) Reductions Step 6 Allocate
Allowable Industrial Loading
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Step 1 Sampling Plan

• The Sampling Plan contains
• The initial influent pollutant scan with Quality
  Assurance/Quality Control (QA/QC)
• Sample chain-of-custodies (COCs) with the
  description of the sampling location(s)
• Documentation of approved 40 CFR Part 136
  analytical methods
• A schematic showing the layout for each
  wastewater treatment plant (WWTP)
• Sampling for influent and effluent, will the POTW
  consider the lag time for treating wastewater
  (plant retention time
• The sampling locations for the seven (7) day
  sampling events for influent, effluent, and
  sludge clearly marked on the schematic
• A detailed explanation of the location(s),
  frequency, and number of samples of the
  Domestic/Commercial background sampling (with no
  significant industrial user contributions in that
  part of the WWTP service area)
• A definition for identifying a "pollutant of
  concern" (POC) as any pollutant found at or above
  0.1 milligrams per liter (mg/L) and any other
  pollutant the publicly owned treatment works
  (POTW) and/or State may designate to be of
  concern
• List the POCs for which seven (7) day sampling
  events will be conducted and local limits will be
  developed (including the 15 national POCs)

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Step 1 Sampling Plan

• The Sampling Plan contains
• List of pollutants to be sampled and flows to be
  measured for those pollutants to be reduced from
  IUs with the required BMPs
• Statement that if hauled waste is accepted, a
  discussion of the handling procedures and
  quantities and qualities of hauled waste will be
  provided with the TBLL submittal
• Identification of personnel or positions
  responsible for technical review, monitoring,
  laboratory analysis, and administration
• Description of sampling equipment or other
  provisions to conduct necessary sampling
• Description of adequate analytical capabilities
  to perform analyses
• A statement that the POTW has all
  chain-of-custody information on-file and that the
  records will be maintained on-site as long as the
  current local limits are in effect
• Authorized a representative, i.e. the POTW permit
  signatory or a consulting firm, to sign and
  certify the Sampling Plan

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Step 2 Collecting Data forLocal Limits
Development
Identify Pollutants of Concern
Detemine Applicable Environmental Criteria
Collect Site Specific Data from
- Publicly Owned Treatment Works (POTW)
- Industrial Users (IUs)
- Domestic/Background Sources
- Nonsignificant IU with required BMPs
Conduct Headworks Analysis
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Determining Pollutants of Concern

• Criteria

• U. S. Environmental Protection Agency (EPA) and
  State Requirements
• 15 National Pollutants of Concern Cd, Cr, Cu,
  Pb, Ni, Zn, As, CN, Ag, Hg, Selenium, Molybdenum,
  BOD5, TSS, Ammonia for plants with sources
• Texas Pollutant Discharge Elimination System
  (TPDES) Permit Limits
• Applicable Water Quality Standards
• Historical Problems (i.e. process inhibition)
• Sludge Disposal Considerations
• Worker Health and Safety Considerations
• Collection System Considerations
• Other (RCRA, Clean Air Act, CERCLA, Drinking
  Water Standards)

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Determining Pollutants of Concern

• Data Sources
• TPDES Permit
• Water Quality Standards/Criteria
• Sludge Standards
• Industrial Waste Survey Review
• Industrial User Compliance Monitoring
• Local Limits Monitoring Program
• IUs
• POTW
• Domestic/ Commercial Background
• Nonsignificant IUs or significant industrial
  users (SIUs) with required BMPs to reallocate the
  TBLLs
• Receiving stream (STORET, State, USGS)
• Literature/Default Data

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Domestic/Commercial Loading

• Monitor Domestic Pollutant Loadings
• Monitor Trunk Lines Receiving Only
  Domestic/Commercial Wastewaters
• If site-specific data cannot be obtained,
  literature values are available

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Removal Efficiencies Mean Influent/Effluent
Loadings
R.E. Removal Efficiency, as a decimal Mean
Influent Loading, lb/day Mean Effluent
Loading, lb/day
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Step 3 Develop Maximum Allowable Headworks
Loadings (MAHLs)
Conceptually, in order to protect water quality
standards, calculating MAHLs is an exercise in
back calculation to meet National Pollutant
Discharge Elimination System (NPDES) permit
requirements
My NPDES permit allows me to discharge x pounds
of copper into the stream.
I know from sampling that my treatment plant
removes, on average, 70 of the copper that
comes in.
How much copper can I allow to enter my plant
without violating my NPDES permit?
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Development of Maximum Allowable Headworks
Loadings
ltMAHLs are typically based on the most stringent
of NPDES Pollutant Discharge Limitations and
Permit Requirements Water Quality Standards or
Criteria Treatment Plant Process Inhibition
Levels/ Operational Problems Sludge Disposal
Standards
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Step 4 Determine Maximum Allowable Industrial
Loading

• Subtract Domestic/Commercial Background
  Contributions
• Subtract Safety/Growth Factors
• - 5 to 20

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Determine Maximum Allowable Industrial Loading
(MAIL)
MAIL Maximum allowable industrial
loading, lb/day MAHL Maximum allowable
headworks loading, lb/day SF Safety
Factor, as a decimal CDOM
Domestic/Commercial background concentration
(mg/L) QDOM
Domestic/Commercial flow (MGD) 8.34
Unit conversion factor Possible Outcomes
- positive MAIL (good) - negative MAIL
(bad)
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Step 5 Account for Required BMP Reductions

• At this point in the TBLLs calculations, the POTW
  will need to decide if they would like to account
  for BMP loading reductions, from either SIUs or
  non-significant IUs, according to the October 14,
  2005 Pretreatment Streamlining Rule.
• The BMPs should be designed to reduce
  concentrations to specified concentrations,
  domestic/commercial background levels, or below
  the MALs.

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BMP Reductions
LBMP Loading attributed to contributing
domestic/commercial and
nonsignificant IUs with required BMPs,
lb/day CBMP Estimated or measured average
pollutant concentrations of the pollutants
being reduced to Zero by the BMP from
contributing domestic/commercial and
nonsignificant IU discharges, mg/L QBMP
Flow from the contributing domestic/commercial
and nonsignificant IUs with required BMPs,
MGD 8.34 Conversion Factor
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BMP Reductions
LBMP The loading that may be added to the
MAIL due to the contributing commercial
and nonsignificant IUs incorporating required
BMPs, lb/day CBMP The reduction in the
average concentration from the contributing
commercial and nonsignificant IUs
incorporating required BMPs down to a
specific concentration QBMP Flow from
the commercial and nonsignificant IUs that will
implement the required BMPs, MGD 8.34
Conversion Factor
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Account for Required BMP Reductions

• If using the TBLL uniform allocation method,
  calculate the MAILBMP, accounting for BMP loading
  reduction, by subtracting the BMP reduction from
  the Domestic and Dommercial loading to determine
  the remaining Domestic and Commercial loading
  (LRDC).
• If the contributing commercial and nonsignificant
  IUs with required BMPs are reducing their
  concentrations to below the MAL or Zero, you
  may subtract the entire BMP loading reduction.

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BMP Reductions
LRDC The remaining domestic/commercial
loading, lb/day LDC Domestic/Commercia
l Loading, lb/day LBMP Loading
attributed to contributing commercial and
nonsignificant IUs with required BMPs
discharges, lb/day
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BMP Reductions
MAILBMP Maximum Allowable Industrial Loading
accounting for BMP loading
reduction, lb/day MAHL Maximum
Allowable Headworks Loading, lb/day LSF
Loading attributed to safety factor,
lb/day LRDC Remaining Loading attributed to
domestic/commercial Loading, lb/day
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BMP Reductions
CTBLLBMP Uniform Concentration TBLL,
accounting for domestic/commercial BMP
reductions, mg/L MAILBMP Maximum Allowable
Industrial Loading, accounting for
domestic/commercial BMP reductions, lb/day QSIU
Industrial Flow, MGD 8.34 Conversion
Factor
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SIU BMP Reductions
QSIU Flow from SIU facilities noncategorical
SIUs and categorical industrial users
(CIUs) that are subject to numeric TBLLs,
MGD QRSIU Flow from remaining SIU facilities
that will have adjusted numeric TBLLs
because of the SIU BMP reductions,
MGD QSIUBMP Flow from SIU facilities that will
implement required BMPs, MGD
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SIU BMP Reductions
LBMP (8.34)(QSIUBMP)( CBMP)
LBMP The loading that may be added to the
MAIL due to the contributing commercial
and nonsignificant IUs incorporating required
BMPs, lb/day CBMP The reduction in
concentration from the initial allowable TBLL
concentrations of X mg/L down to the
concentration of Y mg/L which is the BMP
numeric limit QSIUBMP Flow from the
SIUs that will implement the required BMPs, MGD
8.34 Conversion Factor
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SIU BMP Reductions
MAILRSIU Maximum Allowable Industrial Loading
for the remaining SIUs that will have
adjusted numeric TBLLs because of the SIU BMP
reductions CTBLL Initial allowable TBLL
concentration of X mg/L QRSIU Flow from
remaining SIU facilities that will have adjusted
numeric TBLLs because of the SIU BMP
reductions, MGD LBMP The lb/day loading that
may be added to the MAIL due to the SIUs
incorporating required BMPs
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SIU BMP Reductions
CRSIUTBLL Uniform Concentration TBLLs for the
remaining SIUs that are not incorporating
SIU BMPs and will be subject to the adjusted
TBLLs for each specific BMP pollutant,
mg/L MAILRSIU Maximum Allowable Industrial
Loading, accounting for SIU BMP reductions,
lb/day QRSIU Industrial Flow from the
remaining SIUs that are not incorporating
SIU BMPs and will be subject to the adjusted
TBLLs for each specific BMP pollutant,
MGD 8.34 Conversion Factor
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Required BMPsTBLL Reallocation vs Categorical
Pretreatment Standards

• The U.S. Environmental Protection Agency (EPA)
  has indicated that management plans required for
  categorical pretreatment standards are now
  classified as BMPs
• However, the BMPs described during the TBLL
  process are designed to reduce the loading to
  affect the TBLL allocation, not to fulfill
  categorical BMP requirements

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Step 6 Allocate Allowable Industrial Loading to
Industrial Users
ltFour Allocation Methods Uniform Concentration
Method Industrial Contributory Flow Method Mass
Proportion Method Selected Industrial Reduction
Method
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Industrial Contributory Flow Method

• Applies only to IUs discharging the pollutant
  above Domestic/Commercial background levels
• IUs discharging less than Domestic/Commercial
  background levels are considered
  Domestic/background sources and held to
  Domestic/Commercial background levels
• Industrial contributory flow uses the total flow
  from the IUs discharging pollutants above
  Domestic/Commercial background levels
• Single concentration limit for IUs contributing
  in excess of Domestic/Commercial background levels

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Mass Proportion Method
IU Specific Method

• Allocation in proportion to IU loading
• Different mass limit for each IU

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Selected Industrial Reduction Method

• Allocation method is usually remedial in nature
• Selected IUs are required to reduce loading on a
  Case-by-Case basis
• Usually based on wastewater treatability potential

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Do the Local Limits Make Sense?

• After developing and allocating TBLLs, the POTW
  needs to determine whether they make sense
• Do they pass a common sense test?

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Local Limits Should...

• Be reasonable
• Be at or above sampling detection levels
• If below detection levels, the POTW must adopt
  calculated value, but measure compliance at the
  MAL
• Not be so lenient as to provide IUs the
  opportunity to discharged excessive
  pollutant loadings or encourage hazardous waste
  to be discharged

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BMPs - Timelines

• A timeline must be established for the
  implementation of the BMPs
• Initial estimates of loading reductions are
  verified through
• Sampling of selected Users that have implemented
  BMPs or
• Evaluating influent loadings for pollutants being
  addressed by BMPs

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BMPs and Loading Adjustments

• Loading adjustments may be needed for
• Allowable headworks loadings,
• The numeric limits, or
• The BMPs for any affected sectors