MOLYBDENUM

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MOLYBDENUM

• Nathan Turner

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Moly B Denum
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My History

• Wixom 2002
• Wixom 2003
• South Huron Valley (SHVUA) 2005
• South Huron Valley (SHVUA) 2006

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SHVUA RMP History

• 1987-1999 Biosolids incinerated land filled
• 1998 SHVUA formed and purchased treatment plant
  collection system
• 1999 Earth Tech awarded O M contract
• 1999-2000 Biosolids storage increased from 1.5MG
  to 4.0MG
• 2000 Began land application of biosolids

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Wixom Molybdenum History

• Molybdenum appeared in October 2002 in one of two
  storage tanks
• Began sampling plant influent and each SIU for
  molybdenum
• Molybdenum high in one of two storage tanks

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Wixom Molybdenum History

• 2003 Determined that three of four SIUs
  contributed various amounts of molybdenum
• Determined the MAHL for molybdenum
• SIUs were able to greatly reduce molybdenum in
  discharge by changing process chemicals

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SHVUA Molybdenum History

• Molybdenum first appeared in November 2005 in one
  of four biosolids storage tanks _at_ 95 mg/kg
• 2006 sampling for molybdenum in plant influent
  and effluent. Also sampled each SIU and required
  self monitoring for molybdenum
• Molybdenum in two of the four storage tanks in
  November 2006 _at_ 83 mg/kg

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SHVUA Molybdenum History

• 2007 Determined that six of the then 12 SIUs
  contributed various amounts of molybdenum loading
• 2007 Determined MAHL for molybdenum
• 2007 Worked with SIUs to reduce or element
  molybdenum in discharge to SHVUA WWTP
• 2008 Molybdenum reduced to 29 mg/kg

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Response to Molybdenum Discovery

• DenialDenialDenial
• Sampled each storage tank individually
• Isolated contaminated storage tanks
• Developed dewatering proposal
• Locate landfill for dewatered biosolids

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Whats Next?

• Evaluate Local Limits
• Update SIU discharge permits with molybdenum
  limit
• Continue monitoring program

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Molybdenum Sources
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What we Learned

• Ferric Chloride addition promotes molybdenum
  settling in biosolids
• Concentration and loading must be considered in
  determining SIU discharge limits
• Include domestic sampling for molybdenum (more on
  weekend sampling)