Passive treatment of mining wastewater with a biochemical reactor ...
Transcript of Passive treatment of mining wastewater with a biochemical reactor ...
Presented by
Tom Rutkowski
Golder Associates, Inc.
Passive Treatment of Mining Influenced Wastewater at the Standard Mine Superfund Site, Crested Butte, Colorado, USA
US Environmental Protection Agency (EPA) Standard Mine Superfund Site • Approximately three miles west of Crested Butte, Colorado • Elevation of 3,350 meters (11,000 feet) • Annual snowfall 10.2 – 17.8 meters (400 – 700 inches)
Inactive Hard Rock Mine • Lead, zinc, silver, gold mined from 1874 – 1966
Adit Level 1 Discharges to Elk Creek • Influences Coal Creek, Crested Butte water supply • COC’s cadmium, copper, iron, lead, and zinc
Project Overview
Passive Treatment Pilot Study : • Pilot Biochemical Reactor (BCR) constructed in 2007 (1 gallon per minute, 30 hour HRT) • Aerobic polishing cell (APC) constructed in 2008 • System decommissioned in 2012
Project Goals: Achieve stringent effluent standards • Test passive treatment performance at high alpine remote site • Monitor the system year-round with remote monitoring equipment
Project Overview
Passive Treatment Chemistry 101 SO4
-2 + 2 CH2O HS- + 2HCO3- + H+
(Sulfate reduction by bacteria) Zn+2 + HS- ZnS (s) + H+
(Sulfide precipitation)
Fe+3 + 3 H2O Fe(OH)3 (s) + 3 H+ (Hydroxide precipitation)
H+ + CaCO3 Ca+2
+ HCO3-
(Limestone dissolution)
REDUCING/ ANAEROBIC CONDITIONS
OXIDIZING CONDITIONS
ALL CONDITIONS
Remote Monitoring • Autosamplers • Sondes (pH, temperature, ORP) • Daily Satellite data transmission • Site power provided by photovoltaic array system
Sampling Events • Weekly to monthly analytical grab samples (BCR influent, effluent) • Metals/dissolved metals, calcium, sulfate/sulfide, nitrate-nitrite and ammonia
Test Methods
Data Presented Taken August 2008 – October 2011
Results
Autosampler and pump control panels
Autosamplers
Satellite transmission equipment
pH
Results
pH (su) All Data April - June
BCR Influent 6.2 3.9
BCR Effluent 6.7 -
2009 Freshet 2010 Freshet 2011 Freshet
Temperature • Average winter air temperature -9°C
Results
Temperature °C (°F) All Data Summer Winter
BCR Influent 3.4 (38.1) 4.0 (39.2) 2.9 (37.2)
BCR Effluent 3.2 (37.8) 4.0 (39.2) 2.6 (36.7)
ORP and DO
Results
BCR Influent BCR Effluent APC Effluent
Average ORP (mV) 117 -252 17.7
Average DO (mg/L) 9.2 2.0 6.1
Metals • COC results compared to estimated Colorado in-stream hardness based aquatic
standards for Elk Creek
Results
Parameter Acute Standard Chronic Standard Adit Discharge
Cd, dissolved (µg/L) 1.2 0.31 0.13
Cu, dissolved (µg/L) 9.0 6.2 0.21
Fe, total (µg/L) (water supply) NL 300 9,100 Fe, total (µg/L)
NL 1,000 (TREC) 9,100 Pb, dissolved (µg/L)
40 1.6 310 Zn, dissolved (µg/L)
99 86 24,700
LMPs
50
500
2,000
2,000
200
1,500
Sulfate and Sulfide
Results
BCR
Influent 1/
BCR
Effluent 1/
Percent Removal
BCR Influent to
BCR Effluent
APC
Effluent 2/
Sulfate (mg/L) 281 119 57.2% 122
Sulfide (mg/L as S) 3/ 0.12 12.5 - 0.16
Cadmium, Dissolved • BCR influent average: 130 µg/L • BCR effluent average: 0.19 µg/L • BCR average removal: 99.8%
Results
Copper, Dissolved • BCR influent average: 240 µg/L • BCR effluent average: 1.4 µg/L • BCR average removal: 98.6%
Results
Iron, Total • BCR influent average: 7,100 µg/L • BCR effluent average: 560 µg/L • BCR average removal: 95.0%
Results
Lead, Dissolved • BCR influent average: 280 µg/L • BCR effluent average: 2.2 µg/L • BCR average removal: 98.4%
Results
Zinc, Dissolved • BCR influent average: 24,400 µg/L • BCR effluent average: 73 µg/L • BCR average removal: 99.6%
Results
BCR Performance • Consistently meeting acute stream standards: • Cadmium, copper, iron, lead, zinc
• Consistently meeting chronic stream standards: • Copper, lead, zinc
• Effluent concentrations well below LMPs
APC Performance • Necessary for polishing of BOD and sulfide in BCR effluent
Conclusions
Applicability to meet Peruvian LMP standards: • Passive treatment is occurring in Peru • Passive treatment methods can achieve LMPs • Method is suitable for mountain climate of Peru • Passive treatment ideally suited for: Lower flow sites Sites with significant land availability Sites without electricity
• Types of sites Active mines Mine closures Legacy sites
Conclusions
Co-authors: • Tom Rutkowski • Eric Blumenstein • Neal Gallagher • John DeAngelis (PWT) • David Reisman (EPA) • Christina Progress (EPA)
Tom Rutkowski
Thank You!