MEMORANDUM 

TO: William Swietlik, EPA 

 

FROM: Jessica Wolford, ERG 

 Elizabeth Sabol, ERG 

 

DATE: 24 November 2010 

SUBJECT: Methodology for Analyzing Landfill Iron Concentrations in the 2008 DMR 

Loadings Tool 

1.0 INTRODUCTION

 As part of the 2010 annual review of the Landfills Category, ERG reviewed iron 

discharges in the 2008 DMR database, because they ranked high, in terms of TWPE. As directed 

by EPA, ERG analyzed data to answer the following questions: 

 Are the iron discharges in the database accurate; 

 If so, are the iron discharge concentrations above treatable levels; and finally 

 Could landfills with high iron discharges treat their wastewater and remove iron 

to lower concentrations? 

 EPA is requesting this information to support their determination of whether iron 

discharges from landfills are sufficiently regulated by existing effluent limitations guidelines. 

Part 445, the Landfills Pont Source Category does not currently set limits for iron. The 

Development Document for Final Effluent Limitations Guidelines and Standards for the 

Landfills Point Source Category (Landfills Development Document) (January 2000) indicates 

that “EPA excluded pollutants that are naturally occurring compounds in soil or ground water at 

landfill facilities or pollutants that are used as treatment chemicals in this industry...” This 

included iron, along with other pollutants (U.S. EPA, 2000). 

2.0 METHODOLOGY 

 ERG compared the 2008 iron concentrations from landfills discharges to EPA’s Method 

200.7 iron method detection limit (MDL) and treatable iron concentrations. ERG extracted the 

2008 iron concentrations in landfill discharges from EPA’s DMR Loadings Tool. ERG then 

compared these values to the iron MDL and treatable levels. 

 ERG compared the 2008 iron concentrations to treatability concentrations achievable by 

chemical precipitation and biological treatment because they were the best available technology 

(BAT) basis used to set limits for Subpart A: RCRA Subtitle C Hazardous Waste Landfills (40 

CFR Part 445 Subpart A)1

. No iron treatability data were available in the Landfills Development 

 

1

 The BAT basis used to set limits for Subpart B: RCRA Subtitle D Non-Hazardous Waste Landfills (40 CFR Part 

445 Subpart B) is reverse osmosis. ERG did not have metals removal data for reverse osmosis, but facilities with 
Memorandum 

November 24, 2010 

Page 2 

Document; therefore, ERG used treatability data for chemical precipitation and biological 

treatment already collected during previous annual reviews2

 (U.S. EPA, 2009). ERG used 

treatment data collected from four plants referenced in the Steam Electric Detailed Study (U.S. 

EPA, 2009) and reviewed data from two literature sources that included treatability 

concentrations from 64 sites. Because the data found in the literature sources were incomplete 

and provided conflicting ranges of iron concentrations, ERG only analyzed the concentrations 

reported in the Steam Electric Detailed Study Report. The pH of the wastewater from coal-fired 

power plants, typically ranging from 4.5 to 7.0 S.U., is similar, although more neutral, to landfill 

wastewater, typically 3.7 to 8.0 S.U. (U.S. EPA, 2009). 

 ERG used EPA’s Method 200.7 MDL for iron because of the conventional laboratory 

techniques and instrumentation used and its ability to measure trace concentrations. Table 1 

presents EPA’s Method 200.7 MDL for iron and the concentrations achievable by chemical 

precipitation and biological treatment. 

Table 1. MDL and Treatable Iron Concentrations 

EPA 200.7 MDL (mg/L) 

Chemical Precipitation Treatment 

Concentration Range (mg/L) 

Biological Treatment 

Concentration Range (mg/L) 

0.03 0.019 – 6 ND (0.0022) – 23 

Source: Method 200.7 Determination of Metals and Trace Elements in Water and Wastes by Inductively Coupled 

Plasma-Atomic Emission Spectrometry (U.S. EPA, 1994); and 2009 Steam Electric Power Generating Point Source 

Category: Final Detailed Study Report (U.S. EPA, 2009). 

MDL – Method detection limit. 

ND –Non-detect. Detection limit indicated in ( ). 

 The DMR Loadings Tool contains pollutant concentrations for each facility, outfall, and 

monitoring period. Facilities report up to three concentrations (minimum, average, and 

maximum) for each facility, outfall, and monitoring period combination.3 The DMR Loadings 

Tool also flags concentrations that are reported as below the detection limit (BDL). ERG 

developed the following procedure to accurately represent and review the iron concentrations for 

facilities in the Landfills Category: 

1. ERG extracted the iron concentrations for landfills from the 2008 DMR Loadings 

Tool. There were a total of 3,404 iron concentrations in the 2008 DMR Loadings 

Tool for landfills. 

2. ERG excluded iron concentrations reported as BDL for all monitoring periods for 

a given outfall by excluding outfalls with zero iron load. ERG excluded these 

concentrations from the analysis because, by definition, concentrations below 

 reverse osmosis treatment should be able to achieve pollutant removal at least as well as chemical precipitation and 

biological treatment. 

2

 As part of the Steam Electric Power Generating Point Source Category Detailed Study, EPA collected treatability 

data for chemical precipitation and biological treatment systems. Iron was included in the treatability data (U.S. 

EPA, 2009). 

3

 In the DMRLoads2008_v02 screening level database, EPA has estimated loads for facilities based on a single 

concentration, selected by prioritizing the average concentration first, then the maximum and finally the minimum, 

when computing pollutant loads for specific facility. 
Memorandum 

November 24, 2010 

Page 3 

detection are below treatable levels. This excluded 2,113 concentrations, leaving a 

total of 1,2914

 iron concentrations in the analysis. 

3. ERG removed 0 mg/L concentrations as EPA assumes these reported results infer 

concentrations below detectable levels. This excluded another 5 concentrations 

from the analysis leaving a total of 1,286 iron concentrations that were reported as 

detected above 0 mg/L. 

4. ERG removed concentrations that were reported BDL as these concentrations are 

below treatable levels. This excluded 21 concentrations, leaving 1,265 iron 

concentrations in the analysis. 

5. Because facilities can report multiple concentrations for each monitoring period 

(i.e., minimum, average, and maximum), ERG used the following hierarchy to 

select one concentration for each facility, outfall, and monitoring period, referred 

to as the “final” iron concentrations: 

a. Selected the average concentration (considered the most representative); 

and 

b. If the average concentration was not reported, selected the maximum 

concentration. 

 Note: The DMR Loadings Tool does not include any minimum iron 

concentrations for landfills, likely because landfills are not required to report 

minimum concentrations. 

6. ERG compared the final iron concentrations reported above the detection limit for 

one or more monitoring periods to the EPA Method 200.7 MDL for iron to 

determine if the iron concentrations were at detectable levels. ERG determined 

that 37 iron concentrations (approximately 3 percent), were below the MDL 

reported in EPA Method 200.7. ERG removed these 37 concentrations from the 

analysis, leaving a total of 1,228 iron concentrations. 

7. ERG calculated the median, average, and maximum of the remaining 1,228 iron 

concentrations above the detection limit and the EPA Method 200.7 MDL. 

8. ERG used the median concentration for the remaining analyses. ERG chose the 

median instead of the mean concentration for accuracy.5

 Table 2 shows the statistical values for the iron concentrations. 

Table 2. MDL and Treatable Iron Concentrations 

Range of Iron Concentrations 

Reported 

(Minimum-Maximum mg/L) Median Concentration (mg/L) Mean Concentration (mg/L) 

0.032-33,000 0.929 43.29 

 

4

 Note that some of 1,291 these iron concentrations could still have BDL indicators. In step 2, iron concentrations 

were only removed if all monitoring period concentrations for a given outfall were BDL. 5

 The DMR Loading Tool often contains data that were entered erroneously, such as with units of mg/L instead of 

ng/L. Erroneous data could skew the average iron concentration. Additionally, EPA excluded two facilities, BFI 

Backridge Sanitary Landfill, in La Grange, MO and High Plains Sanitary Landfill, in Floweree, MT, because the 

reported concentrations were unreasonably high (over 1,000 mg/L and 300 mg/L, respectively), and ERG suspects 

data entry errors. 
Memorandum 

November 24, 2010 

Page 4 

 ERG completed the analysis by comparing the median iron concentration to the treatable 

concentration ranges shown in Table 1. ERG determined that the median iron concentration for 

all outfalls is less than the biological treatment or chemical treatability concentrations. As shown 

in Figure 1, approximately 89 percent of the iron concentrations are below the chemical 

precipitation treatability (below 6 mg/L) and 98 percent are below biological treatment 

treatability (below 23 mg/L). The remaining iron concentrations above the chemical precipitation 

treatment range are reported by a total of 24 facilities, seven of which are also above the 

biological treatment range. ERG predicts that database entry errors contribute to the high iron 

concentrations (i.e., 85 mg/L) shown in Figure 1. For further information on the analysis, see 

Section 8.5 of the 2010 TSD (EPA, 2010). 
0

102030405060708090

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 

Percent of Concentrations Equal to or Less than the Treatability Value

Iron Concentration (mg/L)

Iron ConcentrationChem. Precp. Treatability ConcentrationBiological Treatability Concentration

Figure 1. Landfills Iron Concentration Probability Plot
3.0 REFERENCES

1. U.S. EPA. 2000. Development Document for Final Effluent Limitations Guidelines and 

Standards for the Landfills Point Source Category. EPA-821-R-99-019. Washington, 

DC. (January). Available online at: http://www.epa.gov/waterscience/guide/landfills/ 

final/index.html. 

2. U.S. EPA. 2009. Steam Electric Power Generating Point Source Category: Final 

Detailed Study Report. EPA-821-R-008. Washington, DC. (October). EPA-HQ-OW2008-0517-0413 

3. U.S. EPA. 2010. Technical Support Document for the 2010 Effluent Guidelines Program 

Plan. EPA-HQ-OW-2008-0517.Washington, DC (December). DCN 07320.