Physical and Chemical Characterization of Fat and Oil Deposits in Mashhad City Sewer Lines and the Solutions Developed

Formation of oil, fat, and grease deposits in sewer pipelines is a major concern as they result in sewage overflow and pose health problems. Analysis of two sample deposits collected from the sewer lines of Imam Reza Street in the city of Mashhad suggested that the chemical reactions promoted by edible oils in the sewer lines lead to the formation of insoluble soap and deposits. Being sticky, the deposits accumulate over time to eventually block the lines. The analysis also showed that the moisture content of the samples ranged between 50‒62%, indicating that water does not play a main role in their formation. The samples were also found to contain 61.78% and 84.35% saturated fatty acids, with palmitic acid being the dominant one. Calcium was the main metal in the samples, which is due to both water hardness and corrosion of the sewer lines. Based on the results obtained, the origin of these deposits, and the relevant protocols for the management of oil and fat wastes, solutions were proposed to prevent deposit formation and sewer line clogging that suit the special cultural and environmental conditions of the city. These proposals are under consideration for implementation in the region.