Determination of fats, oils and greases in food service establishment wastewater using a modification of the Gerber method

C. Gurd,R. Villa,C. De Castro Rodriguez,B. Jefferson

doi:10.1111/wej.12431

Abstract

AbstractDischarges from food service establishments (FSEs) are a major source of fat, oil and grease (FOG) which cause blockages in sewer networks. Previous research has identified that current methods are unsuitable for quantifying FOG in FSE wastewater owing to interference from surfactants in detergents, and protein from food residuals which emulsify FOG. A novel quantification method, based on the dairy industry Gerber method, has been developed which negates the impact of surfactants. Moreover, the method allows free and emulsified oil to be quantified separately providing greater insight into FOG management strategies. Trials in synthetic and real FSE wastewaters indicate the novel method is more reliable than standard liquid–liquid and solid phase extraction in FOG‐rich systems.

Highlights

The term FOG encompasses a number of different materials and describes a heterogeneous group of chemicals including tri, di- and mono-glycerides, sterols, non-volatile hydrocarbons, waxes and other complex lipids which exist in a combination of free and emulsified forms
Discharges from food service establishments (FSEs) are known to represent a major source of FOG deposits in sewers and area focus for managing their discharges
The current solvents exacerbate an issue with incomplete phase separation, requiring remedial actions if an emulsion persists such as increased agitation (Ducoste et al, 2008) or solid phase extraction (SPE) (Barton, 2012)

Summary

Introduction

The term FOG (fat, oil and grease) encompasses a number of different materials (liquid and solid) and describes a heterogeneous group of chemicals including tri-, di- and mono-glycerides, sterols, non-volatile hydrocarbons, waxes and other complex lipids which exist in a combination of free and emulsified forms. Current management practices of FSE wastewater include treatment in the form of biological additives to process the FOG material into benign end products; or passive separators to collect it. The current solvents exacerbate an issue with incomplete phase separation, requiring remedial actions if an emulsion persists such as increased agitation (Ducoste et al, 2008) or solid phase extraction (SPE) (Barton, 2012). The latter involves use of a hydrophobic matrix that retains all non-aqueous components as the sample passes through the material. A benefit of such approaches is the ability to pre-concentrate enabling more accurate measurement of low concentrations of FOG

Method

Materials and methods

Results and discussion

Conclusions