DESIGN HWA ALTERNATIVES From Meeting Between DWQ and NC Pretreatment Consortium Presented at NC-PC Meeting

DWQ Folks at the 6-21 Meeting  Matt Matthews-New Head of NPDES Section [Poupart’s new boss]  Mike Templeton-NPDES Unit  Jeff Poupart – PERCS  Jon Risgaard – PERCS (leaving PERCS but staying on workgroup)  Iswar Devkota-Construction Grants Plan Review

NC Pretreatment Consortium Folks at the 6-21 Meeting  Sherry Bagwell – Winston Salem  Leon Holt - Cary  Martie Groome - Greensboro

“Old Business” What is rule/regulation that is being violated?  (per Jeff) Context of Rule is not clear Jeff will check with DWQ General Counsel (Mary Payne Thompson) to get legal ruling How does this rule apply with 80/90 rule?

“Old Business”  DWQ Pretreatment folks have not yet reviewed City of Charlotte design criteria study for Charlotte POTWs Dawn Submitted to DWQ at meeting Reports were prepared by engineering firm at cost of $10,000 each (done for 3 POTWs) Study “re-rated” POTWs design capacity

“Old Business” How many POTWs have potential to be impacted by this?  148 POTWs in North Carolina who are part of a PT Program 11 POTWs don’t have industries at all 7 Have no industries but want to keep program Leaves us with 130 POTWs potentially affected by this

6-21 Meeting Agreements  Will limit discussion to BOD/TSS at this point Nutrients [ammonia, TN and TP will be addressed eventually, but will be more complex  Some BOD/TSS alternate options may also work for nutrients  Consortium members will review alternate options/”practice” with them and comment  Would like to have resolution on BOD and TSS by conference in September  NEXT MEETING WED:

1.Maximum or Ceiling Removal Rate  Description: Develop a maximum removal rate usable in the headworks analysis (HWA), thus limiting the calculated pass through MAHL. For example, no POTW could use anything higher than 98% removal on TSS even if their site specific data resulted in a value of 99.1% You would use 98% or your specific value whichever was LOWER

1. Maximum/Ceiling Removal Rate  Advantages: Simple, and easy to implement Decreases the likelihood of the resulting Pass through MAHL being extremely high May better lend itself to TSS  Disadvantages: Does not work well for WWTF with low limits that already require a high removal rate to meet limits Appropriate maximum or ceiling removal rate will be specific to different WWTF and may be highly variable. Does not necessarily result in an MAHL that is a good representation of the WWTF

2. Design Criteria Multiplier  Description: Develop a multiplier that Towns can multiply by the design criteria to establish new MAHL For example:  Multiply Design lbs by 1.25  Multiply Design lbs by 1.5  Multiply Design lbs by 2.0

2. Design Criteria Multiplier  Advantages: Simple, and easy to implement. Results in a MAHL greater then the design criteria.  Disadvantages: Multiplier is difficult to calculate Appropriate multiplier will be specific to different WWTF and may be highly variable Risk using up built in design safety factor needed for providing treatment under variable conditions.

3. Maximum Average Monthly load (in pounds)  Description: Use historical WWTF data to find the maximum average monthly load (lbs) treated without any effluent violations and use that month to determine the MAHL

3. Maximum Average Monthly load (in pounds)  Advantages: Simple, and easy to implement. Relies on proven plant performance to calculate the pass through MAHL  Disadvantages: Historic data may not show values greater than the design MAHL Will not work for POTWs that are currently underloaded

4. Re-rating of WWTF  Description: WWTF is re-rated by a certified engineer to determine design capacity. This would result in a different “design” capacity than currently published in a POTW’s O and M manual

4. Re-rating of WWTF  Advantages: Results are stamped and certified by a professional engineer. Site-specific determination  Disadvantages: May be cost prohibitive (~$60,000/POTW) Criteria on the required depth of study has not been determined.

5. Require use of Detection Level instead of ½ DL  In calculating the WWTF removal rate, the Town would use the detection level instead of ½ of the detection level when the sampling results are reported as less than detect

5.Require use of Detection Level instead of ½ DL  Advantages: Simple, and easy to implement. Will decrease the calculated removal rate and resulting pass though MAHL  Disadvantages: Does not necessarily result in an MAHL that is a good representation of the WWTF ability. Will only affect WWTF that produce effluent less than the detection level. May not be over limiting for WWTF with low limits and low influent concentrations

6. Use Biowin Program (SASPRO, or other products)  Description: Allow for Towns to use the Biowin modeling program (or other approved modeling program) to essentially re-rate the WWTF Some NC-PC Consortium members suggested buying this and having some members train on this software but there may be liabilities to this

6.Use Biowin Program (SASPRO, or other products)  Advantages: Approved model that is used by professional engineers for the design of WWTF and therefore has the potential to produce technically based results.  Disadvantages: May be cost prohibitive. High probability for error if used by inadequately trained individuals. Training to properly use the program may be resource prohibitive.

7. WRRI Research Institute Study (UNC-Charlotte research projects)  Description: request that NC State or other research group investigate the issue for us. Charlotte is using UNC-C students currently and would be willing to give this issue to some of those students

7. WRRI Research Institute Study (UNC-Charlotte research projects)  Advantages: Does not require upfront resources from the State or Towns. Can be assumed that results will be unbiased  Disadvantages: Will require an unknown amount of time No guarantee that results will be broadly usable.

8. Develop RR based on Influent and NPDES Limit  Description: When calculating the removal rates, use the discharge limit instead of effluent sampling results to limit the removal rate, and thus limit the calculated pass through MAHL

8. Develop RR based on Influent and NPDES Limit  Advantages: Simple, and easy to implement.  Disadvantages: May not result in MAHL greater then when using the design criteria. Does not necessarily result in an MAHL that is a good representation of the WWTF ability.

9. 80% rule (or 70% rule, or 90% rule)  Description: Set criteria for when the design criteria can be re-evaluated similar to the flow moratorium requirements. When a WWTF receives less then the cut- off percentage of the design MAHL, the POTW must use the design MAHL. When a WWTF receives more then the cut-off percentage of design MAHL, and they POTW consistently meets their effluent limits, additional MAHL can be granted. (would need to review HWA on a more frequent basis)

9.80% rule (or 70% rule, or 90% rule)  Advantages: Allows of case by case analysis of the WWTFs As the WWTF approaches capacity existing data is a better representation of how the WWTF will operate into at or above design criteria.  Disadvantages: Criteria for allowing more MAHL not yet established Appropriate cut off percentage criteria will be difficult to establish. POTWs approaching but not meeting the cut-off criteria may be constrained.

10. Ammonia Trading  Description: Allow WWTF with low ammonia design criteria to trade some of their BOD loading for ammonia loading based on known oxygen requirements for removing the different parameters. Thus increasing the ammonia MAHL

10. Ammonia Trading  Advantages: Fairly simple, and easy to implement. Results in a greater MAHL for ammonia.  Disadvantages: Oversimplified approach, as biodegradation and nitrification are more complicated then just accounting for the available oxygen Criteria are not established for how much trading is appropriate. Only addresses ammonia issue

11. Flag Level adjustment to allocation table  Description: Develop method for being able to show more actual flow/concentration table in allocation table instead of limits developed with safety factor. Maybe allow for limits in permit as normal but include “flag level” set at expected loading at which permit will be

12. Design Criteria  Use Design Criteria Calculations  This may be appropriate for some POTW situations

13. “Local Pollutant Allocations”  Description: Issue “Local Pollutant Allocations” and Limits to SIUs Local Pollutant Allocation goes into Allocation Table but enforcement is not taken until SIU exceeds limit (which would be higher) Local Pollutant Allocation does not have as large of a “buffer”. Have one allocation table used by POTW another table for Dept of Commerce  Similar concept to #11

13. “Local Pollutant Allocations”  Advantages Eliminates “unused capacity” at POTW Gives truer picture to Dept of Commerce  Disadvantages Complicated Time Consuming Only solves “overallocation” situation- does not truly solve design criteria issue

14. Hybrid of Several Options  No action required until you get to 80% of MAHL for a pollutant Recalculate BOD and TSS %RR and ACTUAL INFLUENT loadings every calendar year and include in PAR  At the 80% point, POTW must choose an option(s) to reduce “on-paper” loading for that pollutant  Options can be different for different pollutants

Where Do We Go From Here??  Review/Discuss options  Develop other options Present to DWQ  Contact other states to determine how the MAHL for TSS and BOD are determined  Narrow the list of options to a workable number for further investigation and “testing”

Where Do We Go From Here?  Take the viable options and use with site- specific data from as many POTWs as possible Various loadings, treatment processes, NPDES limits, etc.)  Present DWQ with the Consortium options “Wish List”  Continue negotiations with DWQ  Along with DWQ, write new guidance on HWA Calculations for BOD and TSS  Implement Guidance