Microbial Uptake of Arsenic

1
Microbial Uptake of Arsenic
Background
Lara Derchak - Civil Engineering Erin Frey -
Chemical Engineering Crystal L. Mattson Civil
Engineering

• 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
• Health Effects
• Immediate symptoms vomiting, esophageal
  abdominal pain and bloody diarrhea
• Long term exposure cancer, gangrene, loss of
  feeling in limbs, hearing impairment, diabetes,
  heart and circulatory problems, and affects the
  gastrointestinal system and liver

Project Objectives
Oxygen Uptake Results

• 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 on growth

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

Arsenic Removal
Experimental Setup

• HACH BODTrak measured oxygen uptake in mg/L vs.
  time
• Conducted at room temperature (22 0.5C)
• Arsenic concentrations measured at conclusion of
  experiment using HACH Arsenic Test Kits

Conclusions
Drinking Water Regulations
Algae

• USEPA Standard 0.01 mg/L
• WHO Standard 0.01 mg/L
• gt 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

• 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
• 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.
• Use of microorganisms for arsenic removal from
  water may be a viable mechanism of arsenic
  removal.

• 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.

Bangladesh

• 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

Oxygen Uptake Results
Acknowledgements
Dr. Kauser Jahan Dr. Patricia Mosto Costantinos
Tsoukalis