Enhancement of biodiesel production by cultivating Dipodascaceae moderated-filamentous granular sludge with sugar-containing wastewater

• Cultivating Dipodascaceae moderated-filamentous biogranules enhanced biodiesel production.
• High sludge loading increased the proportion of Dipodascaceae and lipid yield in biogranules.
• The fungi/bacteria ratio and bacterial population of biogranules affected biodiesel constituents.
• Overgrowth of filamentous fungi deteriorated the settlement and compression of biogranules.

Utilizing excess sludge from a wastewater treatment plant to produce biodiesel has become an increasingly popular topic. However, the low lipid content in activated sludge has hindered the application of biodiesel production from excess sludge. This study was designed to enhance biodiesel production from granular sludge fed with synthetic sugar-containing wastewater. Granules cultivated at different initial sludge loading rates had different morphologies and microbial structure. Low seed biomass and high initial sludge loading resulted in the dominance of the white filamentous fungi Dipodascaceae in granular sludge, thereby enhancing the lipid accumulation of granular sludge and changing the biodiesel constituent produced from the sludge. However, overgrowth of filamentous fungi deteriorated the settling and compression ability of granular sludge. Thus, controlling the filamentous fungi at a moderate level through an effective operating strategy is of great importance to biodiesel production from a granular sludge system fed with sugar-containing wastewater.

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