Development of biodiesel production from bacterial consortium in activated sludge using various enhancement methods

Abstract

The disposal of organic waste is one of the big problems all over the world. As one of the most problematic organic wastes, Sewage sludge (SS), was used as a feed-stock for biodiesel production. First, Sewage sludge (SS) was mixed with Food wastewater (FWW) in ratios of 0:5 (F5 culture), 1:4 (F4), and 2:3 (F3) to control the C:N ratio in cultures as a method to increase lipid production by microorganisms. Total lipid contents at increased by 163%, 42% and 11% increase in F5, F4 and F3 respectively, as a result of increase in triglycerides (TAGs) during the lipid enhancement. The fatty acid methyl esters obtained from TAGs were increased by 25.3%, 20.2% and 13.25% (wt.% of extract) for lipid enhanced F5, F4 and F3 cultures, which were very significant improvements in biodiesel production using sewage sludge. C16:0 fatty acid was mostly converted to C18:1, which is an important determinant of the quality of biodiesel. Second, fenpropimorph induced much more TAGs in activated sludge. Lipid content increased from 21.64 to 40.14 % (wt/wt on the basis of dry sludge) which derived from increase of saponifiable lipids (mostly TAGs) when 100 ㎍/L of fenpropimoph treated. The composition of fatty acids revealed that synthesis of TAGs was caused by inhibition of WEs and SEs synthesis which means redirection of fatty acids toward the storage triglyceride pathway. Third, seawater and activated sludge were mixed with the ratio of 1:9, 2:8, 3:7, 4:6 (volumetric ratio) to maximize the synthesis of poly-unsaturated fatty acid (PUFA). The results showed no increase on both of lipid content and concentration. However, dramatic change on the composition of fatty acids was observed. Especially, palmitic acid (C16:0), palmitoleic acid acid (C16:1) were transferred to oleic acid (C18:1) and linoleic acid (C18:2) in high salinity condition (9:1). This study demonstrates a feasible methods to produce biodiesel using food wastewater instead of a synthetic medium as a carbon source. And also this study will provide practical information about biodiesel production processes when organic waste, activated sludge, used as a feed-stock.