Established Treatment Technologies - Apex Engineering · 6/4/2015 2 Apex Engineering, PLLC Mark...

6/4/2015

Apex Engineering, PLLC

Mark Reinsel, Ph.D., P.E. 1

Short Course: Mine Water Treatment – Technologies, Case Studies and Costs

Established Treatment Technologies

May 3, 2015

6/4/2015 2


Mark Reinsel, Ph.D., P.E.

Presentation Outline

Contaminants of Concern

Potential Treatment Technologies Physical processes

Chemical processes

Biological processes

Metals Removal

Nitrate Removal

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Typical Contaminants of Concern in Mining Waters

Suspended metals

Dissolved metals

Nitrate

Sulfate

Cyanide

Selenium

Arsenic and antimony

Overview of Treatment Technologies

Physical

Chemical

Biological

4

Clarification

Filtration

Membranes

Precipitation (hydroxide, sulfide)

Oxidation/reduction

Ion exchange (IX) and natural zeolites

Attached growth

Suspended growth

Membrane bioreactor

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Clarification

Multiple processes to remove particles in

suspension:

Coagulation/flocculation

Settling

May use sludge recycle

Will not remove dissolved contaminants

Need a disposal site for sludge

Clarifier at Kensington Mine

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Rapid mix tank at Kensington Mine

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Clarifier centerwell at Central Treatment Plant (Kellogg, ID)

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Clarifier overflow at Central Treatment Plant (Kellogg, ID)

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Filtration

Bag filters

Cartridge filters

Sand filters

Multimedia filters

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Multimedia Filters

Coarse but light on top, fine but heavy on

the bottom

Typically anthracite, sand and garnet

Automated operation

Downflow operation, upflow backwash

Backwash via DP, timer or manually

Typical Multimedia Filter

No. 1 Anthracite Coal

Flint Sand

Fine Garnet

Support Gravel

1000-gpm multimedia system at Lucky Friday Mine (Mullan, ID)

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Membrane Processes

Microfiltration (MF)

Ultrafiltration (UF)

Nanofiltration (NF)

Reverse osmosis (RO)

Electrodialysis/electrodialysis reversal

(EDR)

500-gpm UF system at Montanore Mine (Libby, MT)

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RO Disadvantages

Produces high-volume, continuous waste stream

Can be energy-intensive

Removal of monovalent ions such as nitrate may

be limited

Will not remove dissolved gases (e.g., ammonia)

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Chemical Treatment:

Hydroxide Precipitation

Goal is to precipitate & remove dissolved metals

Typically use lime to increase pH

Can be hydrated lime or pebble lime (slaker)

Can also use caustic soda (liquid), soda ash or

magnesium hydroxide

pH target depends upon contaminants of

concern

Co-precipitation can increase removal

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Central Treatment Plant in Kellogg, Idaho

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Aeration Basin at Central Treatment Plant

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Sulfide Precipitation

Typically used as “polishing” step for low

effluent limits

May also be used as primary treatment step

Will achieve lower levels than hydroxide ppt.

Can use sodium sulfide or hydrosulfide (NaHS)

Need little reagent and low retention time

Perform at neutral-to-alkaline pH to avoid H2S

May need filtration to remove small flocs

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Oxidation/Reduction

May be required to transform contaminants into

less-soluble form

Arsenic: Add oxidizing agents such as chlorine,

hydrogen peroxide, ozone, permanganate

Chromium, selenium: Add reducing agents such

as sodium bisulfite or metabisulfite

Reaction is quite rapid

Will add TDS

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Ion Exchange (IX)

Specific resins available for dissolved metals,

arsenic, nitrate

Sodium and chloride are exchanged for

contaminants removed

Several resin manufacturers available

Resin is expensive but can be regenerated (on-

site or off-site)

Waste stream is typically much less than RO

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WATER SOFTENER

RESIN IN THE Ca+2 FORM

RESIN IN THE Mg+2 FORM

RESIN IN THE Na+ FORM

WATER W/ CaCl2, NaHCO3,

MgSO4

WATER W/ NaCl, NaHCO3,

Na2SO4

IX vessels at Buckhorn Mountain

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IX Regeneration

Regenerate with acid, base and/or salt,

depending on the resin

Frequency depends upon contaminants,

feed water quality and discharge limits

Use co-current or countercurrent

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Natural Zeolites

Can be used for ammonia removal

Also have a high selectivity for thallium

Much less expensive than IX resin

Throw away or regenerate with salt

Used at Kendall and Buckhorn Mines

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Biological Treatment

Can be used for the following contaminants:

Organics

Ammonia

Nitrate

Selenium

Sulfate

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Attached Growth Systems

Bacteria are attached to a surface or media

Biofilm provides a very robust process

Very resilient to changes in flow, pH,

concentrations, etc.

Best choice for high concentrations

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Suspended Growth Systems

Commonly used in municipal treatment

systems (activated sludge)

Often used for nutrient removal (N and P)

Nitrification and denitrification

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Membrane Bioreactors

Combine suspended growth biological

treatment with MF or UF

Membrane replaces clarifier and/or

multimedia filters

High biomass concentration/small footprint

Becoming more popular

Biological treatment system at Key Mine (Republic, WA)

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Biological nitrate removal system at Stillwater Mine (Nye, MT)

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Recommendations:

Suspended Metals

In order of preference/cost/ease of use:

Clarification

Multimedia filter

MF or UF

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Recommendations:

Dissolved Metals

Hydroxide precipitation

Sulfide precipitation

IX

NF or RO

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Recommendations:

Nitrate

Denitrification (attached growth biological)

IX

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Nitrate Treatment: Key Mine

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0

5

10

15

20

25

30

35

10/10/06 4/28/07 11/14/07 6/1/08 12/18/08

mg

/l

Nitrate-N Levels at the Key Biotreatment System

NO3- in

NO3- out

Anox Kaldnes system

Installed in 2006

100 gpm

Designed to remove 22

lb/day NH4 and 55

lbs/day NO3-N

Methanol feed

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Nitrate Treatment: Stillwater East Boulder

Design flow of 50

m3/hr (220 gpm)

Reduced [NO3-N]

from 35 to 10 mg/L

(45 kg/day)

Methanol feed

Effective but client

implemented RO

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Nitrate Treatment: Minera Yanacocha

In situ treatment for

NO3 and ClO4

Acetate injection

Removal of 56% and

82% of nitrate in two

source areas to date

[NO3-N] up to 1400

mg/L

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Nitrate Treatment: Alpha Explosives

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For More Information

At http://apexengineering.us

Technology reviews for nitrate, sulfate, arsenic

removal

Natural zeolites: thallium, ammonia

Floating islands

In situ treatment

Summary of Treatment Technologies for

Mining-Influenced Water (EPA, 2014):

focused on passive treatment

http://apexengineering.us/

Established Treatment Technologies - Apex Engineering · 6/4/2015 2 Apex Engineering, PLLC Mark...

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