Quantification of different fatty acids in raw dairy wastewater

This study focuses on the recovery of resources from Latvian dairy industrial wastewater. Specifically, lipids are important resources from the wastewater, so the study aim is to check the quality of the wastewater through COD, BOD-5, total nitrogen, total phosphorus; to separate and characterize fatty acids through various chemicals and characterization (like FTIR, NMR, and GC-MS) techniques. The COD was found to be 1680 ± 20 mg L⁻¹ and the BOD-5 was found to be 1196 ± 50 mg L⁻¹, indicating that the dairy wastewater contains a considerable amount of oxidizable carbon. Also, spectral studies were done to identify the fatty acids in the wastewater. The FT-IR spectrum clearly showed the presence of C–O stretching at 1092 cm⁻¹ and the ¹H NMR indicated the peaks in the range 4.72–5.08 ppm and 5.43–6.33 ppm, confirming the presence of fatty acids. Total lipid content was extracted with solvent extraction method by using hexane, and it was found to be 5.2 g L⁻¹. The acid value of the extracted lipids was found to be 56 mg KOH g⁻¹. Finally, GC-MS analysis confirmed the presence of palmitic acid, stearic acid, myristic acid, oleic acid, linolenic acid, lauric acid, and linoleic acids in the total lipid. Therefore, the extraction of lipids from dairy wastewater is paramount in the applications of biodiesel production.