Bioremediation of Metals and Cyanide from Industrial Wastes

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Bioremediation of Metals and Cyanide from
Industrial Wastes

• K.M. PAKNIKAR
• AND
• P.K.DHAKEPHALKAR

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INDUSTRIAL SOURCES OF CYANIDE POLLUTION

• Electroplating - as complexing agents and
  cyanidic electrolytes
• Mining industry- for gold and silver extraction
  from ores
• Coal gasification
• Steel manufacture - as hardening agents
• Automobile manufacture
• Printed circuit board manufacturing
• Petroleum and organic chemical industries

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PERMISSIBLE LIMITS PRESCRIBED BY ISI
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CONVENTIONAL TREATMENT FOR CYANIDE CONTAINING
WASTE

• Alkaline chlorination - oxidation process
• Hypochlorite
• Ozonation
• Permanganate
• Hydrogen peroxide
• Acidification
• Electrolytic decomposition
• Heating/ thermal oxidation
• Ion exchange

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DISADVANTAGES

• Ineffective against metal - cyanide complexes
• Produces large quantities of sludge (requires
  licensed disposal)
• Require strict process control
• Inability to treat high strength wastes
• Expensive
• Require frequent maintainance
• May not treat cyanide completely

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ARI PROCESS FOR CYANIDE REMOVAL
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SALIENT FEATURES OF ARI PROCESS

• Microbiological process (consortium of four
  cultures)
• High cyanide/ metal cyanide degradation
  efficiency (gt99.9)
• Tolerates cyanide up to 40 mM
• Most efficient at pH 7.5 and temperature 35?C
• Unaffected by the presence of anions such as
  sulfates and chlorides and ammonia

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SALIENT FEATURES OF ARI PROCESS

• Low nutrient requirement (lt600 p.p.m. in terms of
  COD)
• User friendly operation (RBC)
• No expensive chemical additives or external
  aeration required
• Low retention time (15 hours)
• Low volume of sludge formed
• Effluent coming out satisfies CPCB norms

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SALIENT FEATURES OF ARI PROCESS

• Metal cyanide complexes could be recovered using
  metal biosorbent columns (at 65 efficiency
  within 20 minutes). Remaining metal cyanide can
  be treated by RBC in less than 2 hours at an
  efficiency of gt99.9

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ARI PROCESS FOR BIOSORPTION OF METALS FROM
SOLUTIONS

• Cheap process for granulation of fungal biomass
• Easy to operate packed - bed columns
• High process efficiency
• Selective absorption of precious metals such as
  gold and silver from solutions
• Economically feasible
• Eco-friendly
• Applicable to a variety of effluents

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ARI PROCESS FOR REMOVAL OF CHROMIUM FROM EFFLUENTS

• No chemical additives required
• No pH adjustment required for effluents generated
  from cooling towers
• Easy to operate and maintain
• Rugged and highly efficient (gt99.9)
• Unaffected by commonly used biocides and metal
  ions
• Low capital and operating costs