Calculating NumericalLocal Limits

Texas Commission on Environmental

Quality

Texas Pollutant Discharge

Elimination System Pretreatment

Program

Step 1: Develop a Sampling Plan Step 2: Collect Data for Technically Based Local Limits

(TBLLs) DevelopmentStep 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

Overview of Methodology for Developing Local Limits

• 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)

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

Step 1: Sampling Plan

Step 2: Collecting Data forLocal Limits Development

Identify Pollutants of Concern

Detemine Applicable Environmental Criteria

Collect Site Specific Data from:

Conduct Headworks Analysis

- Publicly Owned Treatment Works (POTW)- Industrial Users (IUs)- Domestic/Background Sources- Nonsignificant IU with required BMPs

Determining Pollutants of Concern

• 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)

Criteria

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

• Monitor Domestic Pollutant Loadings

• Monitor Trunk Lines Receiving Only Domestic/Commercial Wastewaters

• If site-specific data cannot be obtained, literature values are available

Domestic/Commercial Loading

Removal Efficiencies: Mean Influent/Effluent Loadings

R.E.= Removal Efficiency, as a decimal= Mean Influent Loading, lb/day= Mean Effluent Loading, lb/day

R EI E

I. .

My NPDES permit

allows me to

dischargex pounds of copper

into the stream.

How much copper can

I allow to enter my

plant without violating

my NPDES permit?

I know from

sampling that my

treatment plant

removes, on average, 70% of the copper that comes in.

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

Development of Maximum Allowable Headworks Loadings

MAHLs 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

Step 4: Determine Maximum Allowable Industrial Loading

• Subtract Domestic/Commercial Background Contributions

• Subtract Safety/Growth Factors

- 5 to 20%

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 decimalCDOM = Domestic/Commercial background concentration

(mg/L)QDOM = Domestic/Commercial flow (MGD)

8.34 = Unit conversion factorPossible Outcomes:

- positive MAIL (good) - negative MAIL (bad)

M A IL M A H L SF C QD O M D O M (lb / d ay ) 1 8 3 4.

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.

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

L Q CB M P B M P B M P 8 3 4.

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

LBMP = (8.34)(QBMP)( CBMP)LBMP = (8.34)(QBMP)( CBMP)

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.

BMP Reductions

LRDC = The remaining domestic/commercial loading, lb/dayLDC = Domestic/Commercial Loading, lb/day

LBMP = Loading attributed to contributing commercial and nonsignificant IUs with required BMPs discharges, lb/day

L L LR D C D C B M P

BMP Reductions

MAILBMP = Maximum Allowable Industrial Loading accounting for BMP loading reduction, lb/day

MAHL = Maximum Allowable Headworks Loading, lb/dayLSF = Loading attributed to safety factor, lb/day

LRDC = Remaining Loading attributed to domestic/commercial Loading, lb/day

M A IL M A H L L LB M P SF R D C

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/dayQSIU = Industrial Flow, MGD

8.34 = Conversion Factor

CM A IL

QT B L L B M P

B M P

SIU

8 3 4.

SIU BMP Reductions

QSIU = Flow from SIU facilities [noncategorical SIUs and categorical industrial users (CIUs)] that are subject to

numeric TBLLs, MGDQRSIU = 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

Q Q QSIU R SIU SIU B M P

SIU 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

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

LBMP = (8.34)(QSIUBMP)( CBMP)

SIU BMP Reductions

MAILRSIU = Maximum Allowable Industrial Loading for the remaining SIUs that will have adjusted numeric TBLLs because of the SIU

BMP reductionsCTBLL = 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

M A IL C Q LR SIU T B L L R SIU B M P ( . ) ( )( )8 3 4

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

CM A IL

QR SIU T B L L B M P

R SIU

R SIU

8 3 4.

Required BMPsTBLL Reallocation vs Categorical TBLL Reallocation vs Categorical

Pretreatment StandardsPretreatment 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, notnot to fulfill categorical BMP requirements

Step 6: Allocate Allowable Industrial Loading to Industrial Users

Four Allocation Methods:$Uniform Concentration Method$Industrial Contributory Flow Method$Mass Proportion Method$Selected Industrial Reduction Method

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

IU Specific Method

Mass Proportion Method

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

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

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”?

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

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 oror

Evaluating influent loadings for pollutants being addressed by BMPs

BMPs and Loading Adjustments

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