Fat, oil and grease - Sewer contamination prevention strategies and double-dosage concept for fat traps and pressure mains

Disposal of fat, oil and grease (FOG) in sewer systems cause blockages, fatal errors of pumping stations, increased maintenance, odours, hydrogen sulphide (H2S) emissions and corrosion. Hence, solutions to prevent FOG disposals are desirable. Challenges are prevention of FOG contamination of sewer systems and removal of FOG disposals. A survey and lab as well as full scale tests were performed. In the first place fat traps and grease inceptors should be installed to prevent FOG contamination what is documented as being very effective. A case study shows that the operation of fat traps may indeed produce further problems, especially H2S emissions, what demands an additional treatment. Removal of FOG disposals can be handled by applying enzymes to the affected sewer network. It was found that enzymes are preferable towards surfactants to remove FOG disposals. It appears to be a solution to have one dosing site that is equipped with separately controlled dosing pumps for conditioners for H2S removal as well as FOG removal.