Water Services Training Group

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Water Services Training Group

• WRc FOG Project
• Biological Issues

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Biological Issues

• Andy Drinkwater
• FOG Programme Manager
• WRc

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WRc FOG Project

• Work Package 1 Legal
• Work Package 2 Sociological
• Work Package 3 Biological/chemical FOG
  compound, dosing methods etc
• Work Package 4a Engineering
• Work Package 4b Operations

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Biological Issues - Tasks

• To
• Develop a clear understanding of the composition
  of FOG found in the sewer system.
• Review of biological/chemical products designed
  to remove FOG

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FOG Work Package 3 Deliverables (1)

• FOG compound (report P6986)
• Products database
• Review of trial site investigations
• Case study, Midleton
• Case study, Chelmsford, England

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FOG Work Package 3 Deliverables (2)

• Review of use of Enzymes, Chemical and Micro
  Organisms in FOG Management
• Comparative Evaluation of Different methods of
  FOG Control
• FOG Strategy, including links to various FOG
  guidance leaflets

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FOG compound

• Large number of samples were collected from
  various parts of sewer systems.
• Analysed for
• content,
• melting point, etc

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FOG samples
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FOG samples
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FOG samples
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FOG compound (2)

• FOG compound collected from kitchens/ drains is
  different to that from the sewer system
• Kitchen derived samples
• Usually soft
• Generally low melting points - therefore would be
  liquid or soft in texture in the wastewater/
  sewage flows
• Mainly fat, oil and grease
• Little else present (apart from some washing
  powder fillers etc)

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FOG compound (3)

• Sewer system samples
• Generally high melting points - therefore would
  be solid/semi-solid in the wastewater/sewage
  flows
• Typically have a strong sewage odour
• Contain a higher proportion of inorganic compound
  grit, lime scale (hard water areas)
• FOG acts as a binder to trap other compounds

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FOG in small sewer
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FOG in small sewer
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FOG in manhole
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FOG in large brick sewer
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FOG deposition

• Tests have shown
• Will get FOG deposition on all materials at
  concentrations of 1 or over
• Animal fat/vegetable oil based FOG without
  detergent will solidify very quickly if
  discharged via the drain (i.e. at temperatures of
  or below 26 28ºC)
• Relatively low detergent concentrations will help
  to keep FOG in suspension and delay its
  solidification

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Biological products

• Wide range of biological dosing products over
  100, though many are the same/similar with
  different labels
• May be able to be used where grease separators
  are impractical
• No standard Not always clear how products work
• Often incorrectly used resulting in poor
  performance

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Biological products (2)

• Need to investigate
• Which products are appropriate for the location
  in question
• Cost-benefits of using a product
• Pros and cons of using these products, compared
  to grease separators
• Then, having selected a product, consider
• Effectiveness in FOG prevention/removal
• The best technique for applying a product
• Methods of application
• Costs

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Biological products (3)

• For adequate performance, need to know
• Flow rates
• FOG Loading
• Presence of other compounds
• Proposed dosing location
• Contact time

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Chemical products

• Not recommended
• Toxic/damage natural sewage treatment process
• Damage to pipes
• Health and safety considerations
• Use should be limited to unblocking domestic
  pipes (U-bends etc)

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FOG Work Package 3 Deliverables (1)

• FOG compound (report P6986)
• Products database
• Review of trial site investigations
• Case study, Midleton
• Case study, Chelmsford, England

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FOG Work Package 3 Deliverables (2)

• Review of use of Enzymes, Chemical and Micro
  Organisms in FOG Management
• Comparative Evaluation of Different methods of
  FOG Control
• FOG Strategy, including links to various FOG
  guidance leaflets