Sustainable Bio-Treatment of Mine Waters Challenges and Opportunities

Dr Sanaz OrandiThe University of Adelaide

AusIMM Technical TalkAugust 2017

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Outline

Background Field studies:

• AMD resources at Sarcheshmeh copper mine and indigenousalgal-microbial biofilm

Laboratory studies: • Microbial studies• Synthesis of a complex multi-ion AMD• Biofilm development in a PRBC• Biological treatment of AMD

Results and conclusion

Sarcheshmeh Copper Mine, Iran1,200 million tonnes ore with an average of1.2 % Cu, 0.03 % Mo, 3.9 g/t Ag, 0.11 g/t Au

World Map of Giant Porphyry Mines

Sarcheshmeh Copper Mine

Background

Mine Open Pit

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Index:

Water Run off

Waste Rock Dump

AMD Resource

Open Pit Drainge Outlet

Chemical Treatment Pond

Scale: 1:50,000

Waste Rock Dumps & Resources of AMD at Sarcheshmeh

Seridun River

Background

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Up stream and AMD from waste rock drainages at Sarcheshmeh

Up stream, pH ~ 6.5-8.5

Field studies

AMD characteristics at Sarcheshmeh copper mine:- Low pH (~ 3)- Contaminated with high concentration of metals/ metalloids: Cu, Zn, Mn, Mg, Pb, Mo, As, Co, Cr, Al, Fe, Cu, Pb, As, Cd, Co, Cr, Ni (<1 - >50 mg/L) - High Sulphate (>1000mg/L)-TDS 980-2000 mg/L

Waste rock drainage, pH ~ 3

Green algae bloom in AMD resources

In-vivo studies

What is a Biofilm?- Initial attachment of free microbial cells to a rough surface - Secretion of Extra-cellular Polymeric Substances (EPS) = mainly composed of

polysaccharides, proteins, nucleic acids and phospholipids.- Developing a multi-layer cell structure and a mature biofilm.- Cell detachment step releases some cells that proceed to a new formation cycle (Singh

et al., 2006; Qureshi et al., 2005).

Biofilm RobustnessEPS Provide a diffusive barrier to any toxic compounds EPS Provide a barrier to contain nutrients for cell growth (Qureshi et al., 2005).

Biofilm formation process

Biosorption - Cleansing role of microbes & biofilm in metal contaminated water

M Metals

Functional groups in microbial cell walls (hydroxyl (-OH), phosphoryl (-PO3O2), amino (-NH2), carboxyl (-COOH), sulphydryl (-SH),) with negative charges adsorb metal ions

Biosorption takes place in:

1. Extracellular accumulation/ precipitation 2. Cell surface sorption and precipitation 3. Intracellular accumulation (Gadd, 2010; Ahalya et al., 2003)

Biofilm Reactors in Wastewater Treatment Technologies-Rotating Biological Contactors (RBC)

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Advantages of RBCs:

-Biofilm formation and attachment on support media

-Provide high interfacial areas-Simple and practical design and operation-Low land occupancy

Research Question

Is it possible to develop a biofilm from the indigenous algal-microbial assembly in a RBC and be exploited for AMD treatment?

???

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Microbial Studies: Biodiversity of Microbes in AMD Biofilm• Morphological Studies• Bimolecular Studies - PCR

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Laboratory Studies

Light Microscopy & SEM Images, filamentous micro-algae

Light Microscopy & SEM Images, uni-cellular green micro-algae

The indigenous biofilm from Sarcheshmeh AMD is dominated with filamentous and uni-cellular green micro-algae (Klebsormidium sp. & Chlamydomonas sp.)

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Microbial Studies: Biodiversity of Microbes in AMD Biofilm

- Bacteria (Pseudomonas sp. & Tiobacillus sp.: Thiobacillus thiooxidans,

Acidithiobacillus ferrooxidanse) - Fungi (Penicillium sp. & Aspergillus sp.)- Yeasts(Orandi et al., 2007)

Laboratory Studies

Growth & Maintenance of Algal-Microbial Assembly Bold Basal Medium

Synthesis of a complex multi-ion AMD (Syn-AMD) containing:

- More than 20 elements such as Cu, Mn, Zn at high concentrations (20-100

mg/L) and Sb, Ni, Cr, Co, Al at low concentrations (0.005-2.5 mg/L)

- Anions SO4 (>2000mg/L), Nutrients (PO4~1mg/L, NO3 ~20mg/L)

- Low pH (~ 3)

(Orandi and Lewis, 2012)

Laboratory Studies

Comparable results of AMD and Syn-AMD analysis:

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0 20 40 60 80 100 120 140

K

Na

Ca

Mg

Mn

Cu

Ni

Zn

Si

Concentration (mg/L)

Syn-AMD

AMD

0 0.1 0.2 0.3 0.4 0.5 0.6

Al

Fe

Ag

Se

Sb

Co

Mo

Pb

Cr

Concentration (mg/L)

Syn-AMD

AMD

0 5 10 15 20 25

Cl

NO3+NO2

HCO3+CO3

PO4

C

NH4

Concentration (mg/L)

AMD

Syn-AMD

Preliminary test on biofilm development on fixed media

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Laboratory Studies

- Single stage laboratory scale PRBC, consist of 16 PVC discs (0.25 m diameter), roughened with 5-grit grade sandpaper

-15 L Synthetic AMD, 40% submerged discs

-Rotational speed (2 & 5 rpm)

- Light (tubular cool white fluorescent lamps ~ 756 µmol m-2 s-1 , set to 12:12 h light-dark

(Orandi et al, 2012)

Biofilm development in a Photo-Rotating Biological Contactor (PRBC)

Laboratory Studies

Immobilisation of algal-microbial biofilm on PRBC’s discs

Laboratory Studies

PRBC operation & AMD treatment

Batch Mode

Rotational speed = 5rpm

Treated AMD with pH 3 & 5

Continuous mode

• 24 h Hydraulic Residence Time (HRT) • Supplied AMD to reactor = 10 mL/min• Duration of experiment = Ten-week period,

(Orandi and Lewis, 2013)

Laboratory Studies

Water & Microbial analysis• Water analysis:

– Cations: Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) – Anions (Nutrients) : Thermo Scientific Nutrient Analyser

• Qualitative & quantitative biofilm analysis: Scanning Electron Microscopy (SEM) – Energy Dispersive X-ray Spectroscopy (EDS) in conjunction with SEM-

semi quantitative data from accumulated heavy metals on biofilm– Back Scattered Electron Imaging (BSE)

• Microbial Identification: Polymerase Chain Reaction-Denaturing Gradient Gel Electophoresis (PCR-DGGE)

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Laboratory Studies

Water analysis results of batch mode for major elements:

Aaverage removal of 20–40 % at pH 3 in the order of

Na>Cu>Ca>Mg>Mn>Ni>Zn,

whereas a higher removal (35–50 %) was observed at pH 5 in the order of

Cu>Mn>Mg>Ca>Ni>Zn>Na

Results

Water analysis results of batch mode for trace elements:

The removal efficiency of the system for trace elements varied extensively between5 to 80% at both pH 3 & 5

Results

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0

10

20

30

40

50

60

% M

ajor e

lemen

t rem

oved

Time (Min)

Na

Mg

Ca

Mn

Ni

Cu

Zn

Results

Continuous mode resultsRemoval percentages of Major elements over first 24h

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-20

0

20

40

60

80

100

0 5 10 30 60 120 180 360 720 1440

% T

race

elem

ent R

emov

ed

Time (Min)

Al

Cr

Fe

Co

Se

Mo

Ag

Pb

Sb

Continuous mode resultsRemoval percentages of trace elements over first 24h

Results

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0

10

20

30

40

50

60

Cu Mg Ni Na Mn Ca Zn

% M

ajor

ele

men

ts r

emov

ed

MaxMinAvg

-60

-40

-20

0

20

40

60

80

100

120

Ag Fe Mo Cr Pb Se Sb Co Al

% T

race

elem

ents

rem

oved

MaxMinAvg

Weekly averaged removal for major and trace elements

Cu>Mg>Ni>Na>Mn>Ca>Zn (30-50%)

Ag>Fe>Mo>Cr>Pb>Se>Co (10-80%)

Results

Continuous mode results

Scanning Electron Microscopy (SEM) and Back Scattered Electron Images (BSE)

Results

SEM image-before treatment SEM image-after treatment

SEM –BSE SEM –BSE

Energy Dispersive X-ray Spectroscopy (EDS) spectrums in conjunction with SEM

Elements Na Mg Mn Fe Co Cu Zn

Values % 1.13 1.06 0.34 6.84 0.25 3.66 0.52

Results

Indigenous mining micro-algae, potential biosorbent for removing heavy metals, robust & low-nutrient dependant

PRBC, a promising and sustainable approach for treating metal contaminated wastewaters.

Algal-Microbial biofilm can be adapted for target containments

The efficiency of system can be improved by sequenced bio-reactors

The work needs to be scaled up to the pilot scale in field – Looking for industry Partner to develop this promising technology .

Conclusion

Questions?