Anaerobic degradation of linoleic (C¦1¦8:¦2), oleic (C¦1¦8:¦1) and stearic (C¦1¦8:¦0) acids and their inhibitory effects on acidogens, acetogens and methanogens

grantor: University of TorontoEffluents from many food processing industries contain fats and oils in addition to carbohydrates and proteins. Long chain fatty acids (LCFAs), a hydrolysis byproduct of fats and oils, are difficult to degrade and are inhibitory to anaerobic organisms. These acids are degraded via ß-oxidation but the compound initiating the mechanism has not been clearly identified. Although LCFAs inhibit aceticlastic methanogenesis their effects on acidogenesis, acetogenesis and hydrogenotrophic methanogenesis have not been well studied. This study assessed the degradability of linoleic (C18:2), oleic (C18:1) and stearic (C18:0) acids and determined their inhibitory effects on anaerobic organisms in 160 mL serum bottles. Degradation and inhibition studies were conducted using 10, 30, 50 and 100 mg·L-1 LCFA. Inhibition studies using glucose, butyrate and acetate (each at 100 mg·L-1) and hydrogen (10.1 kPa) investigated the effects of the three LCFAs on acidogens, acetogens, aceticlastic methanogens and hydrogenotrophic methanogens. Unsaturated C18 LCFAs were degraded to shorter chain LCFAs however, no LCFA byproducts were detected as intermediates during the degradation of stearic (C18:0) acid. Palmitic (C16:0) and myristic (C 14:0) acids were produced from linoleic (C18:2) acid at all concentrations examined and in cultures receiving more than 10 mg·L -1 oleic (C18:1) acid. In cultures receiving 100 mg·L-1 linoleic (C18:2) acid, both oleic (C18:1) and palmitoleic (C16:1) acids were detected. Acidogenesis was affected by the presence of LCFAs and synergistic inhibitory effects of all three acids on acetogenesis were observed. Hydrogenotrophic methanogenic inhibition was observed and aceticlastic methanogens were inhibited at all LCFA concentrations examined. In cultures fed with linoleic (C 18:2) and oleic (C18:1) acids, inhibition of acetate methanogenesis was concentration dependent but for cultures receiving stearic (C18:0 ) acid, the effect was independent of concentration. In comparison to stearic (C18:0) acid, linoleic (C18:2 ) and oleic (C18:1) acids were degraded faster. Therefore, the design of a full-scale system will depend on the SRT for the more slowly degrading LCFA. LCFAs affected glucose and butyrate degradation. Hence, in effluents containing carbohydrate and LCFAs mixtures, the degradation of carbohydrate monomers will be affected. In comparison to oleic (C18:1) acid, greater aceticlastic inhibition was observed for cultures receiving linoleic (C18:2) acid. Thus, it is recommended a two-stage process, acetogenic followed by methanogenic, be used to minimize the inhibition.Ph.D

One‐step deposition of nano‐Ag‐TiO 2 coatings by atmospheric pressure plasma jet for water treatment: Application to trace pharmaceutical removal using solar photocatalysis

International audienceIn this study, micrometer thick Ag‐TiO2 coatings were deposited in a single and facile step by spraying the precursor in an atmospheric pressure plasma jet with different concentrations of Ag nanoparticles. The homogenous distribution of Ag decreased the TiO 2 crystal size and increased the surface area. The coatings were characterized to be porous with an anatase phase with improved charge separation and visible light absorption. The photocatalytic activity of the materials was investigated for degrading rhodamine B using a white lamp as a screening method to optimize Ag‐TiO 2 coatings. Then the photodegradation of trace pharmaceutical compounds (TrPCs) was investigated by using a solar light simulator at the optimal condition of a TiO 2 coating with 0.4wt% A