Investigation of thecontrol of the fat, oil and grease in sewer lines and their removal by surfactant treatment

This study investigated different methodsof controlling the fat, oil and grease (FOG) in sewer systems. A comprehensive control program wasdevelopedfor the city of Mashhad (Iran) to maintain its sewer system and prevent blockages. The control program consisted of three parts: 1) fat, oil and grease source control, 2) sewer system modification and 3) preventive maintenance. This program includedguidelinesfor food service establishments, which are the majorsources of (FOG). Food service establishments must implementbetter management practices to reduce (FOG)from entering the facility drain and install grease removal devices.As a part of preventive cleaning, theperformance of several surfactants was evaluated as a cleaning agent. A 50:50 mixture (10 v. % in water) of two industrial surfactants, one containing monoethyl amine and sulfonated lauryl alcohol and one containing nonylphenolethoxylate and potassium hydroxide,had the best performance and removed 80 % of the fat. Response Surface Methodology was used to determine the optimum conditions for the surfactant.The optimum conditions were acontact time of 36 h, shaking rate of 30 rpm andsurfactant concentration of 12.5%.The second part of the program consisted ofremoving dead zones and increasing wastewater velocity in the sewer lines to enhance thehydraulic condition of thesewer system and decrease fat deposition.Finally, a detailed and well-defined control program couldsolve FOG problems in sewer systems.