[PPT] - Colorado Mining Association Pre-filtration: Study Results and PowerPoint Presentation

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Colorado Mining Association

Pre-filtration: Study Results and Proposal for 303(d) Listing Methodology

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Presented by: Bob Gensemer September 25th, 2012

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Background

Water quality criteria typically based on

dissolved or total recoverable fraction

Dissolved measures the ecologically relevant form

that is bioavailable and potentially toxic to aquatic life

Total recoverable also measures small colloidal or

hydroxide phase metals (removed by the 0.45 µm filtration used for dissolved), which for Fe and Al can be toxic

− But also measures metals associated with non-toxic particulates (i.e., “chunks”) − Problematic at sites with lots of suspended particles − Likely overestimates the concentration of metal that would actually be toxic to aquatic life

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Background

GEI, ARCADIS, and New Mexico

Environment Department studies

Pre-filtration before total recoverable analysis
Do toxic colloidal forms of metals get through?
Provide a better representation of the metals

that are toxic to aquatic life

Is coarse pre-filtration appropriate and

protective?

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Study Goals

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1. Determine if total recoverable iron and

aluminum are reduced in proportion to the total suspended solids (TSS) in the sample.

2. Determine if particle size distribution

analysis confirms removal of only non-toxic forms.

3. Confirm removal of non-toxic metal forms

via toxicity testing on the species most sensitive to iron and aluminum.

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Goal #1: TSS vs. Fe and Al

TSS (mg/L)

500 1000 1500 2000 2500 3000 3500

Iron (mg/L)

5 10 15 20 25 30 35

Correlation between iron and TSS concentrations in raw

water samples (i.e., unfiltered).

R2 = 0.392

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TSS (mg/L)

500 1000 1500 2000 2500 3000 3500

Aluminum (mg/L)

5 10 15 20 25 30 R2 = 0.934

Stronger correlation between aluminum and TSS

concentrations in raw water samples (i.e., unfiltered).

Goal #1: TSS vs. Fe and Al

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Sites

GEI-1 GEI-2 GEI-3 GEI-4 GEI-5 ARCADIS-1 ARCADIS-2 ARCADIS-3 ARCADIS-4 ARCADIS-5 NMED-1 NMED-2

Iron (mg/L)

0.001 0.01 0.1 1 10 100 Raw 20.0 µm 10.0 µm 5.0 µm 1.0 µm 0.45 µm * * * * * * * *

Confirmed decrease in iron using 5.0 µm filtration,

without complete removal.

Goal #1: Filter Effectiveness

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Sites

GEI-1 GEI-2 GEI-3 GEI-4 GEI-5 ARCADIS-1 ARCADIS-2 ARCADIS-3 ARCADIS-4 ARCADIS-5 NMED-1 NMED-2

Aluminum (mg/L)

0.001 0.01 0.1 1 10 100 * * Raw 20.0 µm 10.0 µm 5.0 µm 1.0 µm 0.45 µm

Confirmed decrease in aluminum using 5.0 µm filtration,

without complete removal.

Goal #1: Filter Effectiveness

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Goal #1: Filter Effectiveness

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Sample Standard TSS Raw Filter Size (µm) and Measured Iron (mg/L) Acute Chronic Raw 20 µm 10 µm 5.0 µm 1.0 µm 0.45 µm GEI 1 NA 1.0 166 6.69

0.05

<0.02 <0.02 GEI 2 NA 1.0 42.4 2.97

0.04

<0.02 <0.02 GEI 3 NA 1.0 1102 30.6

0.02
<0.02

GEI 4 NA 1.0 1110 13.6

0.09
<0.02

GEI 5 NA 1.0 81.6 3.55

1.35

<0.02 <0.02 ARCADIS 1 NA 1.0 NA 0.36

0.07

0.012 0.018 ARCADIS 2 NA 1.0 2 0.22

0.032

0.013 0.025 ARCADIS 3 NA 1.0 5 0.13

0.056

0.023 <0.010 ARCADIS 4 NA 1.0 330 13.0

0.62

0.075 0.059 ARCADIS 5 NA 1.0 510 43.0

0.5

0.49 0.61 NMED 1 NA 1.0 600 5.50 0.08 <0.05 <0.05 <0.05

NMED 2

NA 1.0 3020 17.5 0.12 0.055 0.055 0.065

Confirmed decrease in iron to levels below criteria

using 5.0 µm filtration.

Table 1. Iron data and chronic criteria from the relevant state (mg/L). Bold red font indicates values exceeding the chronic standard. New Mexico does not have an iron standard, so the standard of 1.0 mg/L is only used for comparative purposes.

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Goal #1: Filter Effectiveness

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Similar decrease in aluminum to levels below criteria

using 5.0 µm filtration.

Table 2. Aluminum data and acute and chronic criteria from the relevant state (mg/L). Bold red font indicates values that exceed the acute and chronic criteria. Bold blue font indicates values that only exceed the chronic standard.

Sample Standard TSS Raw Filter Size (µm) and Measured Aluminum (mg/L) Acute Chronic Raw 20 µm 10 µm 5.0 µm 1.0 µm 0.45 µm GEI 1 11.1 1.58 166 3.02

0.047

0.014 0.018 GEI 2 0.75 0.087 42.4 0.50

0.006

0.004 0.011 GEI 3 22.8 3.26 1102 14.0

0.007
0.004

GEI 4 22.8 3.26 1110 6.71

0.044
0.006

GEI 5 7.54 1.08 81.6 4.00

1.53

0.014 0.077 ARCADIS 1 4.39 1.76 NA 0.64

0.31

0.19 0.20 ARCADIS 2 4.90 1.96 2 0.64

0.32

0.17 0.18 ARCADIS 3 5.00 2.00 5 0.61

0.30

0.16 0.18 ARACDIS 4 4.19 1.68 330 3.10

0.22

0.10 0.094 ARCADIS 5 6.74 2.70 510 45.0

0.074

0.034 0.04 NMED 1 4.09 1.64 600 8.55 0.055 <0.05 <0.05 <0.05

NMED 2

3.95 1.58 3020 26.5 0.095 <0.05 <0.05 <0.05

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Goal #1: Filter Effectiveness

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Sample 20 µm 10 µm 5.0 µm 1.0 µm 0.45 µm TSS Al Fe TSS Al Fe TSS Al Fe TSS Al Fe TSS Al Fe GEI 1

97.6*

98.4 99.3 97.6* 99.5 99.7 97.6* 99.4 99.7 GEI 2

90.6*

98.8 98.7 90.6* 99.2 99.3 90.6* 97.8 99.3 GEI 3

99.1

99.9 99.9

99.5

99.9 99.9 GEI 4

99.6*

99.3 99.3

99.6*

99.9 99.9 GEI 5

68.0

61.8 62.0 95.1* 99.7 99.4 95.1* 98.1 99.4 ARCADIS 1

51.6

80.6

70.3

96.7

68.8

95.0 ARCADIS 2

50.0

85.5

73.4

94.1

71.9

88.6 ARCADIS 3

50.8

56.9

73.8

82.3 70.5 92.3 ARACDIS 4

92.9

95.2

96.8

99.4

97.0

99.5 ARCADIS 5

99.8

98.8

99.9

98.9

99.9

98.6 NMED 1

99.4

98.5

99.4

99.1

99.4

99.1

99.4

99.1

NMED 2
99.6

99.3

99.8

99.7

99.8

99.7

99.8

99.6

Confirmed decrease in iron and aluminum concentration

proportional to TSS consistent with all filter sizes.

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Goal #2: Particle Size

12 Sample % Sample of Particle Size 5 µm or greater % TSS Reduction % Al Reduction % Fe Reduction GEI 2 84.3 89.6 98.8 98.7 GEI 3 81.6 99.1 99.9 99.9 GEI 4 91.6 99.6 99.3 99.3 GEI 5 45.2 68.0 61.8 62.0 ARCADIS 4 52.3

92.9

95.2 ARCADIS 5 100

99.8

98.8

Particle size distribution (PSD) analysis was not possible

for most of the filtered samples due to insufficient suspended solids remaining after filtration.

However, the particle size withheld by the 5.0 µm pre-

filtration step is expected to be similar to the size of the particles withheld by the standard TSS filtration step, considering the retention size of the glass fiber filters used for TSS are typically around 1 to 1.5 µm.

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Goal #3: Toxicity

Only 2 of the 10 raw water samples

demonstrated minor sublethal toxicity

Iron and aluminum concentrations in raw

water were up to 43x higher than water quality criteria

Supports premise that total recoverable

can include measurement of non-toxic forms

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Conclusions

Pre-filtration would adequately remove the

majority of the non-toxic, particulate phase metals, which is supported by PSD analysis

Toxicity attributable to metals was not observed

at iron and aluminum concentrations up to 43 times higher than the water quality standard

Total recoverable analysis after coarse pre-

filtration provides the most environmentally relevant measurement that is still protective of aquatic life

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Recommendations

Recommend use of a 5 or 10 µm pre-filter
New Mexico is proposing 10 µm
“For aluminum, the criteria are based on analysis of total

recoverable aluminum in a sample that is filtered to minimize mineral phases as specified by the department.”

In 303(d) Listing Methodology, similar language

could be added to Section III.C.1. Chemical Data – General (pages 15-16 of March 10, 2011 version). For example:

g. Attainment of Aluminum and Iron Standards

Aluminum and iron standards are based on analysis of total recoverable aluminum and iron in a sample that is pre-filtered through a 5 µm filter to minimize mineral phases.

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