Municipal Authority of the City of McKeesport, PA 

Headworks Loading Analysis for Natural Gas 

Drilling Wastewater Pollutants 

March 2011

i

Municipal Authority of the City of McKeesport, PA 

NPDES Permit No. PA0026913

Headworks Loading Analysis for Natural Gas 

Drilling Wastewater Pollutants 

March 2011

TABLE OF CONTENTS

 PAGE

1.0 Introduction ...................................................................................................................... 1

1.1 Natural Gas Drilling Wastewater Acceptance Policy and Protocol.................... 1

2.0 MAHL Calculation: Methods Input and Considerations........................................... 2

2.1 Sampling Phase .......................................................................................................... 2

2.2 Calculation Phase....................................................................................................... 2

3.0 MAHL and MAIL Calculation....................................................................................... 6

4.0 MAHL and MAIL Calculation Results ......................................................................... 6

4.1 MAHL Calculation Results................................................................................... 6

4.2 MAIL Calculation Results..................................................................................... 7

4.3 MAHL Comparison to Current Industrial Loads ............................................. 7

5.0 Summary and Conclusion .............................................................................................. 9

TABLES

Table I: POTW Removal Rates .................................................................................................... 4

Table II: Chronic Water Quality Criteria ................................................................................... 5

Table III: Maximum Allowable Headworks Loading (MAHL) Results................................ 6

Table IV: Calculation of the Maximum Allowable Industrial Loading................................. 7

Table V: MAHL Comparison to Current Industrial Loads..................................................... 8

Table VI: Proposed Maximum Headworks Industrial Allowance ........................................ 9

APPENDICES

Appendix A: Data Summary and Raw Data 

Appendix B: MAHL Calculation
Municipal Authority of the City of McKeesport - 1 -

Headworks Loading Analysis for Natural Gas

Drilling Wastewater Pollutants 

March 2011 

Municipal Authority of the City of McKeesport, PA

NPDES Permit No. PA0026913

Headworks Loading Analysis for Natural Gas 

Drilling Wastewater Pollutants 

March 2011

1.0 INTRODUCTION

The Municipal Authority of the City of McKeesport (MACM) owns and operates a 

Wastewater Treatment Plant (WWTP) under the terms of NPDES Permit No. PA0026913

and within the framework of a USEPA approved Pretreatment Program. The Publically 

Owned Treatment Works (POTW) provides a preliminary, primary and secondary 

treatment as well as disinfection of wastewater from the 11 communities that comprise the 

collection system service area. The POTW discharges a treated effluent to the Monongahela 

River. 

Although there are currently no categorical or significant industrial users within the 

collection system service area, the MACM accepts wastewater from companies engaged in 

the drilling of the Marcellus Shale layer to tap natural gas wells. As regulatory agencies 

consider this waste industrial in nature, the MACM has developed permits for acceptance of 

the waste with contracted sources and haulers. 

Pursuant to the findings of a September 2009 USEPA audit of the MACM pretreatment 

program, the MACM has been required to conduct a headworks loading analysis (HLA) for 

pollutants found in natural gas drilling wastewaters and, if necessary, develop local limits 

The purpose of this report is to provide explanation and details of the headworks loading 

analysis to fulfill the EPA requirement. 

1.1 NATURAL GAS DRILLING WASTEWATER ACCEPTANCE POLICY AND PROTOCOL 

Natural gas drilling wastewater is accepted at the MACM WWTP after an onsite MACM

employee screens the wastewater for pH and once a sample from the hauling vehicle has 

been taken. If the pH is beyond the acceptable range of 5.0 to 12 pH units the hauler is 

turned away. Provided that the wastewater is within an acceptable pH range, the 

wastewater is discharged from the hauler into an excess capacity aerated basin. The 

Authority policy is to limit the amount of wastewater accepted from one source (well site) to 

less than 25,000 gallons per day and cumulatively 1% of the average day forward flow from 

all sources per a PADEP administrative order issued October 23, 2009. The “co-mingled” 

gas well wastewater is diluted with WWTP primary effluent, aerated, and continuously 

introduced to the headworks of the facility at a slow rate through the WWTP internal 

recycle drain line, which also transmits belt filter press filtrate, Vactor receiving station
Municipal Authority of the City of McKeesport - 2 -

Headworks Loading Analysis for Natural Gas

Drilling Wastewater Pollutants 

March 2011 

drain and other WWTP drains to the wet well. Wastewater entering the wet well is then 

pumped through the treatment train of the WWTP. 

2.0 HLA CALCULATION: METHODS INPUT AND CONSIDERATIONS

The Headworks Loading Analysis consisted of the sampling phase, and the calculation of

potential local limits. 

2.1 SAMPLING PHASE:

The sampling phase was comprised of an EPA approved sampling plan, sampling and 

analysis. A copy of the approved sampling plan and analytical reports for the samples used 

are appended to this report in Appendix A. 

As identified in the sampling plan:

a. An evaluation of the sampling data of the wastewater accepted by the MACM has 

identified eight (8) pollutants selected pursuant to pending regulations and 

historical higher source concentrations than other pollutants scanned for samples 

analyzed.

b. For analyses yielding consistent non-detectable results for various pollutants, it was 

determined that the background does not contain the pollutant and further analysis 

for that pollutant may be ceased and replaced with another pollutant.

c. Timed composites samples were obtained once a month for 12 months at designated 

locations to avoid contamination of samples from other sources that could dilute the 

strength of gas wastewater pollutants.

d. Samples were analyzed by a contracted third party laboratory using EPA approved 

methods.

Pursuant to item b. above, lithium was included in the original eight (8) pollutants and 

replaced in the third month of the sampling phase by iron.

2.2 CALCULATION PHASE

EPA Region III has developed a Microsoft Excel spreadsheet for evaluating data associated 

with pretreatment programs for the purpose of determining maximum allowable loadings 

and potential local limits. A digital copy of this spreadsheet was supplied to KLH 

Engineers, Inc. for the purpose of utilizing the calculations incorporated therein to perform 

the headworks loading analysis. The base spreadsheet utilizes two linked worksheets. The 

raw data is input in the Monitoring Data worksheet which automatically calculates the percent 

removals. The Limits Calculation Worksheet identifies where POTW and receiving stream 

data is required and directs the user to select the removal rate basis for the pollutants being 

calculated. The Limits Calculation Worksheet then automatically calculates the headworks 

loadings using logical progressions based on the most stringent parameters through a series 

of 19 Tables.
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Headworks Loading Analysis for Natural Gas

Drilling Wastewater Pollutants 

March 2011 

The calculation included the following considerations used as information input into the 

various Tables in the EPA Spreadsheet:

1. Table 1 – Unit Operations in the Limits Calculation Worksheet requests the user to input 

which of the listed unit operations are present at the POTW. Since the MACM WWTP 

does not have a trickling filter or anaerobic digester and is not designed for the removal 

of ammonia nitrogen, only the activated sludge choice was selected.

2. Table 2 - Flow and Receiving Stream Data in the Limits Calculation Worksheet request the 

user to input data about the POTW and receiving stream.

a. The average annual flow for the sampling period of 9.4 MGD was input where 

requested.

b. A value of 0.036645 MGD was entered as input to account for the wastewater 

accepted from haulers associated with the drilling of gas wells.

c. The average annual flow of sludge wasted to the sludge stabilization process for 

the 2008 Operating Year was calculated as 0.03572 MGD and input where 

requested.1

d. The average annual flow of dry sludge disposed of from the WWTP for the 2008 

Operating Year was calculated as 2.87 dry metric tons and input where 

requested.1

e. The average annual flow of hauled municipal waste accepted at the WWTP for 

the 2008 Operating Year was calculated as 0.03582 MGD and input where 

requested.1

f. The 7Q10, and hardness utilized in determining the NPDES Permit limits were 

furnished by the PADEP. The 1Q10 and Harmonic Mean Flow determined using 

a mixing factor procedure advised by USEPA. The input values are as follows:

NPDES Permit 7Q101

(Chronic Stream Flow)

650 cfs = 420 MGD

NPDES Permit 1Q101

(Acute Stream Flow)

84 MGD

NPDES Permit Harmonic Mean Flow1 420 MGD

Hardness 193 mg/L as CaCO3

It should be noted that although the water quality standards that would apply to 

the pollutants of concern are actually applicable at drinking water intakes; and 

understanding that the nearest drinking water intake is approximately 11 miles 

downstream, the various stream flows would be larger values as there are 

 1 This value is consistent with the most recent HLA performed for the evaluation of the MACM local limits

required by the NPDES Permit.
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Headworks Loading Analysis for Natural Gas

Drilling Wastewater Pollutants 

March 2011 

several tributaries to the Monongahela River between the MACM outfall and the 

next drinking water intake. As such, it was decided that the conservative 

approach would be to utilize the aforementioned flows at the MACM outfall. 

3. The data collected for influent with recycle to include the target wastes, and POTW 

effluent samples were input into the Monitoring Data worksheet. Pollutant mean values 

were calculated and outlying data points (data more than twice the standard deviation 

of the data population) were removed from the calculation. 

The worksheet then calculates the percent removal comparing influent to effluent and 

influent to sludge. Table I demonstrates the calculated removal rates through the POTW 

and identifies the removal selected in Table 3 of the limits calculation.

Table I: POTW Removal Rates

Parameter POTW Influent/Effluent 

Removal Percentage Selected Removal Rate

Barium 71.64 % Influent/Effluent

Bromide 26.99 % Influent/Effluent

Chloride 4.44 % Influent/Effluent

Iron 89.32 % Influent/Effluent

Magnesium 6.62 % Influent/Effluent

Strontium 18.47 % Influent/Effluent

Sulfate 3.94 % Influent/Effluent

Total Dissolved Solids 6.43 % Influent/Effluent

Sampling analysis results from the influent (without recycle) were input the Monitoring 

Worksheet as the background level of pollutants in this analysis as they are 

commensurate with the POTW influent sampling results. The data was evaluated for 

outliers and the calculated mean values for application to the calculation. 

4. Available receiving stream concentrations for pollutants of concern were obtained from

data published by the West Virginia Water Research Institute in their “Monongahela 

River Water Quality Study”. The data is from a monitoring station at River Mile 23 

approximately 7 miles upstream. Because the Youghiogheny River confluences with the 

Monongahela River downstream of the POTW discharge, the Monongahela River 

background pollutant concentrations obtained from the upstream monitoring station 

have been used, since these more nearly represents the mixing of the effluent with the 

stream flow. The data available for the study period was averaged and input as 

designated in Table 4 of the Limits Calculation Worksheet.

5. Table 4 of the Limits Calculation Worksheet requires input for chronic water quality 

standards. As not all pollutants had existing statewide water quality standards, 

potential state, and national water quality standards were applied as chronic standards. 
Municipal Authority of the City of McKeesport - 5 -

Headworks Loading Analysis for Natural Gas

Drilling Wastewater Pollutants 

March 2011 

Given the conservative approach of utilizing stream flows upstream of the drinking 

water intake, applying these criteria against the 7Q10 Stream flow would account for 

mixing within the river between the MACM outfall and next drinking water intake. 

Table II identifies the chronic water quality standard applied for the various pollutants:

Table II: Chronic Water Quality Criteria1

Parameter Concentration

(in mg/L)

Governing Source

Barium 10 Proposed PA WQS2

Bromide Not Available

Chloride 250 PA Statewide WQS3

Iron 1 National WQS4

Magnesium Not Available

Strontium 10 Proposed PA WQS2

Sulfate 250 PA Statewide WQS3

Total Dissolved Solids 500 PA Statewide WQS3

Notes:

1. Water quality standards applied as chronic standards.

2. As published in the Keystone Water Quality Manager, “Marcellus Shale Gas Well Operations Impact 

on Pretreatment Programs” - Judy Musselman, Jul-Sep 2009; p. 20.

3. As published in Pennsylvania Code Title 25, Chapter 93 Water Quality Standards.

4. As published by EPA in National Recommended Water Quality Criteria, 2006

6. Table 5 of the Limits Calculation Worksheet requires input for acute water quality 

standards. No acute water quality criteria were available and thus not applied to the 

calculations for this report.

7. Table 6 of the Limits Calculation Worksheet requires input for human health water quality 

standards. Applicable human health national water quality standards were applied to 

the calculations for this report.

8. The activated sludge inhibition default threshold values in Table 8 of the Limits 

Calculation Worksheet for all applicable pollutants were input. The only pollutant 

evaluated herein with a potential for inhibition was iron, with a USEPA published2

threshold level concentration range of 5-500 mg/L published. The inhibition threshold 

applied was the most stringent value 5 mg/L as a matter of conservatism.

9. Table 10 of the Limits Calculation Worksheet evaluates the loading with respect to 

nitrification inhibition. Although the MACM does not have regulatory limits nor is the 

POTW designed to intentionally remove nutrients, an inhibition threshold for 

Magnesium2 was applied, because no other water quality criteria was available to 

compare the data obtained against. Also given the lack of regulatory requirements, it is 

again considered conservative to apply such a standard. 

 2 Guidance Manual for Preventing Interference at POTWs, USEPA, September 1987
Municipal Authority of the City of McKeesport - 6 -

Headworks Loading Analysis for Natural Gas

Drilling Wastewater Pollutants 

March 2011 

10. Data entry for Tables 9, 11, 12, and 14 was not performed as evaluations with respect to 

trickling filter inhibition, anaerobic digestion inhibition, and sludge disposal were not 

applicable to this study.

11. A safety factor of 10% of the calculated allowable load was applied to Table 16 of the 

Limits Calculation Worksheet. The entry of this safety factor is consistent with the 

conservative approach throughout this calculation and in accordance with EPA 

recommendations for the application of safety factors.

3.0 MAHL AND MAIL CALCULATION 

The pages contained in Appendix B are a printout Tables 1-19 of the Limits Calculation 

Worksheet that calculates the Maximum Allowable Headworks Loading (MAHL) and the 

Maximum Allowable Industrial Loading (MAIL) for the POTW. 

4.0 MAHL AND MAIL CALCULATION RESULTS

4.1 MAHL CALCULATION RESULTS

The results of the calculation using the Excel spreadsheet and based on the foregoing input 

considerations are presented in Table III. The table presents the result of the MAHL, and 

the criteria governing the calculation of the MAHL. 

Table III: Maximum Allowable Headworks Loading (MAHL) Results1

Parameter MAHL in pounds per day Governing Criteria

Barium 12,627.37 Proposed PA WQS

Bromide Surveillance and Monitor2 Not Applicable

Chloride 853,141.27 PA Statewide WQS

Iron 391.98 Activated Sludge Inhibition

Magnesium 3,919.80 Nitrification Inhibition

Strontium 43,926.59 Proposed PA WQS

Sulfate 463,215.07 PA Statewide WQS

Total Dissolved Solids 808,963.31 PA Statewide WQS

Notes:

1.Information presented as calculated in Table 15 of the Limits Calculation Worksheet in Appendix B.

2. No numeric MAHL value could be calculated. 

It should be recognized that as no MAHL value could be calculated for Bromide due to the 

lack of water quality criteria and inhibition values, it has been determined that the MAHL 

will continued to be evaluated and monitored until such time that standards for 

comparison are available. 
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Headworks Loading Analysis for Natural Gas

Drilling Wastewater Pollutants 

March 2011 

4.2 MAIL CALCULATION RESULTS

From Table 16 of the spreadsheet calculations, the MAHL has been converted into a 

Maximum Allowable Industrial Loading (MAIL) by applying aforementioned safety factors 

and subtracting the background concentrations from the collections system. Table IV 

presents this conversion. 

Table IV: Calculation of the Maximum Allowable Industrial Loading

Parameter MAHL1

in lb/day

MAHL2

in lb/day

Background3

Loading in 

lb/day

MAIL4

in lb/day

Barium 12,627.37 6,313.68 27.12 11,337.51

Bromide S &M5 282.15 S &M5

Chloride 853,141.27 426,570.64 18,755.10 749,072.05

Iron 391.98 195.99 104.36 248.42

Magnesium 3,919.80 1,959.90 1,178.73 2,349.09

Strontium 43,926.59 21,963.29 28.62 39,505.31

Sulfate 463,215.07 23,1607.53 6,231.83 410,661.73

Total Dissolved 

Solids 808,963.31 404,481.65 4,6126.66 681,940.31

Notes:

1. MAHL – Maximum Allowable Headworks Loading

2. MAHL – Maximum Allowable Headworks Loading with a Safety Factor of 2 applied.

3. Background Loads: Influent (without recycle load) Samples Average concentrations converted from 

mg/L to lbs/day

4. MAIL – Maximum Allowable Industrial Loading (with 10% Safety Factor) = MAHL less Background 

Loads

5. S &M - Surveillance and Monitor

4.3 MAHL COMPARISON TO CURRENT INDUSTRIAL LOADS

Typically, the MAHL is compared to the current industrial maximum and average pollutant 

loadings, and the allocation on current IU permits. Currently there are no values on the 

existing permits with waste originators and haulers and no other industries within the 

collection system regulated by the Pretreatment Program. Therefore, a comparison can only 

be made to the current industrial maximum and average pollutant loadings to determine 

the need for local limits. Table V represents the results of Table 17 of the spreadsheet 

calculations which makes this comparison.
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Headworks Loading Analysis for Natural Gas

Drilling Wastewater Pollutants 

March 2011 

Table V: MAHL Comparison to Current Industrial Loads

Parameter MAHL

in lb/day

Current 

Industrial 

Average 

Load1

in lb/day

Average 

Percent 

Loaded vs. 

MAHL2

Current 

Industrial 

Maximum 

Load3

in lb/day

Maximum 

Percent 

Loaded vs. 

MAHL4

Barium 12,627.37 191.71 1.52 % 1,200.63 9.51 %

Bromide S &M5 393.69 - 1,262.18 -

Chloride 853,141.27 29,513.96 3.46 % 65,311.71 7.66 %

Iron 391.98 135.91 34.67 % 265.45 67.72 %

Magnesium 3,919.80 1,339.69 34.18 % 1795.82 45.81 %

Strontium 43,926.59 194.68 0.44 % 473.12 1.08 %

Sulfate 463,215.07 5,971.16 1.29 % 8,153.18 1.76 %

Total 

Dissolved 

Solids

808,963.31 67,135.48 8.30 % 122,376.16 15.13 %

Notes:

1. Current Industrial Average Load – Average influent concentration from the monitoring data converted 

from mg/L to lbs/day

2. The Current Industrial Average Load as a percentage of the MAHL.

3. Current Industrial Maximum Load – The single maximum influent concentration from the monitoring 

data converted from mg/L to lbs/day.

4. The Current Industrial Maximum Load as a percentage of the MAHL.

5. S &M - Surveillance and Monitor

As demonstrated in Table V, a comparison of the maximum and average industrial 

pollutant loadings received at the MACM headworks, in most cases, represents single digit 

percentages for the pollutants evaluated. Pursuant to the Local Limit Development 

Guidance document published by the USEPA, a POTW is recommended to adopt a local 

limit for a pollutant if the average percent loading exceeds 60% of the MAHL and the 

average percent loading is more than 80% of the MAHL.3 In no case, as demonstrated in 

Table V do these conditions occur. Therefore, the MACM does not intend to adopt local 

limits for these parameters based on this evaluation. 

Consistent with the diligence exerted by the MACM with respect to this waste, samples and 

analyses for these pollutants will continue to be obtained and the results compared to the 

MAHL calculated herein. Should the influent loadings approach the threshold percentages 

for required local limits, or as required by regulatory agencies, the HLA will be reevaluated. 

 3 As published by the USEPA in Chapter 6.1.1 of Local Limit Development Guidance.
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Headworks Loading Analysis for Natural Gas

Drilling Wastewater Pollutants 

March 2011 

5.0 SUMMARY AND CONCLUSION

The MACM owns and operates a WWTP with an approved USEPA Pretreatment Program 

that accepts wastewater from companies engaged in the drilling of the Marcellus Shale layer 

to tap natural gas wells. A September 2009 USEPA audit of the MACM pretreatment 

program, yielded the requirement for headworks loading analysis for pollutants found in 

natural gas drilling wastewaters and, if necessary, develop local limits with respect to the 

results of the headworks loading analysis.

The headworks loading analysis was performed in two phases: the sampling phase, and the 

calculation of maximum allowable loadings and potential local limits. The proposed 

Maximum Allowable Headworks Loading and Maximum Allowable Industrial Loading

were calculated utilizing USPA recommendations and conservative input values. The 

results were compared to current industrial maximum and average pollutant loadings. In 

no case, did the influent loadings exceed the threshold percentages for required local limit 

adoption. To this end, no local limits will be adopted for the pollutants evaluated for this 

report. Finally, MACM will continue to compare monthly sample analysis results to the 

MAHL and MAIL calculated herein and presented in Table VI, as a means of evaluation of 

the wastes accepted and to determine if local limits are necessary. 

Table VI: Proposed Headworks Industrial Allowance 

Parameter MAHL in lb/day MAIL in lb/day

Barium 12,627.37 11,337.51

Bromide Surveillance and Monitor Surveillance and Monitor

Chloride 853,141.27 749,072.05

Iron 391.98 248.42

Magnesium 3,919.80 2,349.09

Strontium 43,926.59 39,505.31

Sulfate 463,215.07 41,0661.73

Total Dissolved Solids 808,963.31 68,1940.31
Municipal Authority of the City of McKeesport

Headworks Loading Analysis

March 2009 

APPENDIX A:

SAMPLING PLAN, DATA SUMMARY

AND RAW DATA
Municipal Authority of the City of McKeesport

Headworks Loading Analysis

March 2009 

APPENDIX B:

MAHL CALCULATION