Transcript Arsenic Poster

Microbial Uptake of Arsenic
Mixed Bacteria Culture
• Obtained bacteria from a local wastewater treatment plant
• Exposed bacteria to varying concentrations of arsenate (Na2HAsO4)
•
•
and arsenite (NaAsO2) (0.05 mg/L – 1.5 mg/L)
Second experiment had concentrations varying from 50 mg/L to
1600 mg/L.
Glucose (C6H12O6) used as the carbon source
Drinking Water
Regulations
80
10
0
50
Impact of Arsenate Concentration on
Chlorophyll Production
60
40
20
0
1
glucose
2
0.05 mg/L
Time (days) 3
0.5 mg/L
1.5 mg/L
4
50 mg/L
5
400 mg/L
1600 mg/L
Arsenic Removal
0.8
0.6
0.4
0.2
0
Arsenate Concentration (mg/L)
Percent Removal of Arsenic from a Contaminated Sample
Chlorella Vulgaris
120%
100%
80%
60%
40%
20%
0%
Scenedesmus Abundans
Conclusions
0.5
1.5
50
400
• MIXED CULTURE
 At low concentrations, significant amounts of both forms of
arsenic were removed (60% average)
 It is apparent that low concentrations of arsenic may be removed
by aerobic bacteria
 At high concentrations, varying removal was noted for both forms
• Arsenite removal 48%
• Arsenate removal 77%
 Probable cause for low arsenite removal is toxicity
 Probable mechanism for removal is biosorption
 Higher concentrations significantly impacted growth
 Inhibition is approximately 50% at 1600 mg/L contradicting
available literature
1600
Original Concentration (mg/L)
Arsenite Arsenate
• Two methods by which algae can uptake heavy
metals
– Biosorption
– Bioaccumulation
• Scenedesmus abundans and Chlorella vulgaris
are both common green freshwater algae
capable of metal uptake
• Batch experiments with algae and varying
concentrations of arsenic were conducted.
• Arsenic concentrations were measured with time.
• Algae morphology was checked at end of
experiments.
Scenedesmus Abundans
100
Algae
Bangladesh
C
on
tro
l
1
m
g/
L
5
m
g/
L
10
m
g/
L
20
m
g/
L
Chlorella Vulgaris
120
0.05
• > 0.05 mg/L (50 ppb) As concentrations found throughout
country
• Large populations exposed to As because of groundwater
contamination worldwide
• As contaminated countries include Bangladesh, Australia,
Chile, and New Zealand
Algae Biomass
(mg/L)
140
0
uptake in mg/L vs. time
Conducted at room temperature
(22 + 0.5°C)
Arsenic concentrations measured at
conclusion of experiment using
HACH Arsenic Test Kits
• USEPA Standard: 0.01 mg/L
• WHO Standard: 0.01 mg/L
Arsenite Concentration With Time
(Chlorella Vulgaris Studies)
6000
I mg/L
5000
5 mg/L
4000
3000
2000
1000
0
0
1
2
Oxygen Uptake Results
3
4
5
6
Tim e (Hours)
• ALGAE
 Removal of arsenic was time dependent with major removals
occurring within the first hour of experimentation.
 Desorption of arsenic was evident after the first hour.
 Algae morphology was impacted by the presence of arsenic.
However the impact was not arsenic concentration dependent.
Algal morphology changed to clumping at higher concentrations
of arsenic.
Significant differences were not noticed for arsenic uptake with
the two types of algae.
Arsenite Concentrations With Time
(Chlorella Vulgaris Studies)
Average Oxygen Uptake of a Mixed Culture Exposed to Arsenite
Oxygen Uptake (mg/L)
• People used the rivers as their source
of water
– Began to get sick and even die
because of the bacterial
contamination
• The solution: Change to groundwater
– Did not realize the arsenic problem
at the time
• Groundwater arsenic contamination
was first discovered in 1993
– Thousands of wells were already in
place
– 5 times higher than the world
standard
Arsenate Concentration (mg/L)
• HACH BODTrak measured oxygen
•
0
160
Experimental Setup
•
50
10
0
• Oxidation and reduction
reactions occur in sediment
• Anthropogenic and natural
emissions
• Methylation processes by
algae in surface waters
• As is consumed by certain
organisms in the water
on growth
100
50
Arsenic Cycling in the Environment
• Determine if a mixed bacteria culture is a viable treatment option
• Study the adsorption of arsenic by iron
• Identify algae species that will uptake arsenic and study the impact
150
Co
nt
ro
l
1
m
g/
L
5
m
g/
L
10
m
g/
L
20
m
g/
L
– Long term exposure: cancer, gangrene, loss of feeling
in limbs, hearing impairment, diabetes, heart and
circulatory problems, and affects the gastrointestinal
system and liver
Average Oxygen Uptake of a Mixed Culture Exposed to Arsenate
Oxygen Uptake (mg/L)
– Immediate symptoms: vomiting, esophageal &
abdominal pain and bloody diarrhea
Impact of Arsenate Concentration on Algal
Growth
Oxygen Uptake Results
Project Objectives
Concentration Remaining
(ppb)
• Health Effects
Lara Derchak - Civil Engineering
Erin Frey - Chemical Engineering
Crystal L. Mattson – Civil Engineering
120
100
80
60
40
20
0
0
1
2
3
4
5
Time (days)
glucose
0.05 mg/L
0.5 mg/L
1.5 mg/L
50 mg/L
400 mg/L
1600 mg/L
Concentration Remaining
(mg/L)
• Toxicity
– Arsenic is extremely toxic causing severe health
problems
– LD50 of arsenic is between 15 and 30 mg/kg of body
weight
– In comparison, NaCl is 3,000 mg/kg body weight and
nicotine is 60 mg/kg body weight
• Exposure
– Dermal Contact
– Ingestion
– Inhalation
Chlorophyll
(mg/L)
Background
60000
Use of microorganisms for arsenic removal from water may be a
viable mechanism of arsenic removal.
10 mg/L
50000
20 mg/L
40000
50 mg/L
30000
Acknowledgements
20000
10000
Dr. Kauser Jahan
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0
1
2
3
Time (Hours)
4
5
6
Dr. Patricia Mosto
Costantinos Tsoukalis