Bay Of Toulon Research Articles

Fatty acids and sterols in domestic wastewaters

Raw and treated sewage from physical-chemical and biological wastewater treatment plants were analysed for fatty acids and sterols by HPLC and GC. Raw sewage fatty acid and sterol concentrations varied widely during a diel cycle but their composition remained almost the same. Fatty acids were represented mainly by four components: 16:0, 18:0, 18:1( n-9) and 18:2( n-6). Three 5β-stanols: coprostanol, 24-methylcoprostanol and 24-ethylcoprostanol, accounted for 50–60% of the total sterols, and the coprostanol/cholesterol and the 24-ethylcoprostanol/β-sitosterol ratios were greater than 1. These characteristics were still recognizable in the treated sewage from physical-chemical and biological treatment plants. Removal was more efficient with the biological treatment than with the chemical one, especially for the dissolved compounds. It is estimated that 223 kg of fatty acids and 11 kg of sterols are released daily into the bay of Toulon by the Toulon-Est treatment plant while 74 kg of fatty acids and 5 kg of sterols are discharged into the Morlaix River estuary every day. In general, treated or raw sewages supply 0.1–8 g/day/cap of fatty acids and 0.01–0.6 g/day/cap of sterols to the surrounding environment.