Characterization of the fate of lipids in wastewater treatment using a comprehensive GCxGC/qMS and statistical approach

Lipids, characterized as oils, greases, fats or long-chain fatty acids are an important organic component of municipal wastewater, their removal being the main concern in wastewater treatment. This paper reports an application of the comprehensive GCxGC/qMS for the evaluation of the lipids removal mechanism in different wastewater treatment plants in order to assess the role of different physical and biological processes over the removal mechanism. For this purpose, the content and fats profile in wastewater were analyzed and calculated. For the separation of the fatty acid methyl esters (FAMEs) enclosed on the fats, two combinations of the capillary columns coated with non-polar/polar and polar/non-polar phases were applied. The validated proposed GCxGC/qMS method presented satisfactory results in terms of repeatability (coefficient of variation lower than 15%), linearity (ranging from 0.5 to 10 mg mL(-1)), limit of detection (LOD) and limit of quantification (LOQ). In order to increase the consistency of the results, statistical analysis regarding the composition of the fats in both influent and effluent were performed. The results of performed experiments showed that, in the wastewater plant which contains only a physical trap, the removal mechanism is based on the adsorption of fats onto particulate matter, while in the wastewater plants which include a biological trap, the removal mechanism combines the adsorption of fats on the particulate matter in the physical trap with the biodegradation of fats with bacterial activated sludge in the biological trap. As a result, the composition of fats during the biological treatment is modified due to the beta-oxidation and other microbial bioconversion processes which through an aerobic biodegradation process destroys the mono-and poly-unsaturated fatty acids and promotes the accumulation of saturated long chain fatty acids.