Wastewater Treatment Case Study: Emulsion Cracking

Wastewaters with very high emulsified Fats, Oils & Grease (FOG) and various other hydrocarbons content were generated in a wastewaters from equipment cleaning operations in a large industrial facility producing food products. 

  • Not having a stage of the wastewater treatment programme to address the emulsified hydrocarbons, compliance with the conditions stipulated in the discharge licence was not possible.

ECOS Environmental Consultants were commissioned to identify and review treatment options for the client.  Included in the brief was the need to address:

  • Treatment targets and compliance with Discharge Licence requirements
  • Capital and operational costs
  • Training requirements and staff involvement
  • Technical support available and/or required from suppliers and third parties
  • Recovery/Reuse/Disposal options for waste by-products

A wastewater treatment programme was developed which was tailored meet the clients requirements.

The stages of the treatment programme included:

Emulsion Cracking/pH Adjustment:

  • pH was lowered to 3.5 using acid and strong coagulant chemistry to break the emulsions.

pH Adjustment/Precipitation and Coagulation:

  • pH was adjusted to 8.5 using caustic and a coagulant was added to cause further de-emulsification and precipitation of the non-emulsified solids.
  • A “pin floc” was developed indicating the emulsion had been “cracked” and suspended solids had been formed which could be precipitated or floated.

Flash Mix:

  • The wastewater with pin floc was introduced to the flash mix zone where a polymer flocculent was added.

Flocculation:

  • The wastewater was then introduced to the slow mix zone to agglomerate the floc into larger particles suitable to be enmeshed with the air bubbles.

Clarifier, Dissolved Air Flotation (DAF):

  • The flocculated wastewater was introduced into the DAF inlet where the floc particles were comingled with a pressurized dissolved fine bubble recycle stream.
  • The floc particles attached to the bubbles and floated to the surface where they were mechanically removed.
  • The clarified treated water then exited the end of the DAF and flowed downstream to the monitoring station prior to discharge to sewer.

Results before & after Treatment:

Parameter

Before Treatment
mg/l

After Treatment
mg/l

COD

25,185

345

FOG

985

8

DAF Sludge Handling:

  • The resulting DAF waste sludge was removed from the DAF automatically and was pumped to the sludge holding tank where it was further thickened prior to processing in a filter press.

Sludge Dewatering:

  • A flocculant was added to the thickened DAF sludge to condition it prior to application to a filter press where with was dewatered.
  • A dewatered sludge cake of 20-25 % solids was generated and subsequently disposed off through a licenced commercial composting facility.
  • Product and waste recovery/reuse options are currently being evaluated.

For more information on wastewater treatment and sludge management please contact us at 061 633644 or info@ecos.ie.

ECOS Environmental Consultants Limited