Fat, Oil and Grease (FOG) in Sewer Systems : Survey and Countermeasure Suggestions

Fat oil and grease (FOG) from food preparation can cause severeproblems if it is discharged to the municipal sewer network. A surveyamong Swedish and Norwegian municipalities has shown that nearlyall respondents experience FOG-related problems. The most commonproblem is FOG accumulation connected to the sewer pipes whichdecreases the pipe pipe capacity and may lead to sewer overflows. FOGaccumulation occurs especially at lift stations and depressions. FOGdeposits are often made up of saponised FOG. The fatty acids promotefurthermore corrosion of concrete pipes. FOG can even impact wastewater treatment and might cause severer working conditions.The aim for the water suppliers has thus to be an effective FOGsource control before FOG is discharged to the sewer network. Sourcesare both commercial establishments and residential sewer customers.In this report different source control measures are discussed. Greaseinterceptors are commonly used for commercial FOG sources. However,a number of them lack a grease interceptor and quite often operationand maintenance is deficient. An insufficient frequency ofemptying and a lack of supervision have been identified as a commonproblem. FOG collection systems for commercial FOG producers existin both Sweden and Norway. Collection systems for private householdsare currently in a test phase and experiences from among others Austriaare promising. Even the collected amount of FOG could presumablybe increased. Collected FOG and FOG slurry from interceptors is avaluable resource which can be used as raw material in the chemicalindustry or as an energy source (combustion, biodiesel, fermentation).Threshold values for FOG discharges are set up commonly by municipalities.However, even here supervision is often insufficient. Often, thethreshold values are inadequately low and a value of at least 150 mg/lis recommended. All those measures have to be supported by informationcampaigns which aim on both commercial and private customers.Matfett orsakar ökande driftproblem i norska och svenska avloppsledningsnät (t.ex. påbyggnad, stopp i ledningen eller korrosion av betongrör). I rapporten inventeras källorna och diskuteras olika åtgärder för att förebygga fettutsläpp som t.ex. installation och drift av fettavskiljare, matfettinsamling eller informationskampanjerGodkänd; 2010; 20100330 (godble)Fett i avloppsnät - Kartläggning och åtgärdsförsla