(757c) Microbial Oil Accumulation Capability of Activated Sludge Microorganisms Feeding on Short Chain Fatty Acids

The microbial oil accumulation capability of activated sludge feeding on short chain fatty acids such as acetic acid, propionic acid, and butyric acid as carbon sources has been studied to establish a proof of concept for an envisioned integrated anaerobic-aerobic microbial system for the production of microbial oil for fuels from organic waste streams. Preliminary experimental results show that activated sludge microorganisms can use the short chain fatty acids resulting to oil accumulation. Feeding the activated sludge with 1.25 g/L total acids at 1:1:1 mass ratio of acetic, propionic, and butyric acids resulted to an increase of oil content from 7 % (w/w) to 11 % (w/w) while all the acids added were consumed for an incubation period of 1 day. The microbial oil yields, however, are not yet comparable to that of the yields from glucose-fed oil accumulation of activated sludge conducted by other researchers in recent years. This paper examines the pertinent technical aspects of the system to reduce short chain fatty acids inhibition and to further enhance the microbial oil accumulation capability of activated sludge feeding on short chain fatty acids that can be generated from organic wastes. The various aspects examined are the feeding mode of the acids – fed-batch and batch, the molar C/N ratio, and the mass ratio of the three acids in the mix.