Influence of volatile solids and pH for the production of volatile fatty acids: batch fermentation tests using sewage sludge

TL;DR

This study investigates how volatile solids and pH influence volatile fatty acids production during sewage sludge fermentation, aiming to optimize conditions for higher VFA yield and better stream quality.

Contribution

It introduces the use of high sludge retention time WAS and identifies optimal VSS and pH conditions for maximizing VFA production.

Findings

Optimal VFA production at 5.9 g/L VSS and pH 10

Bacterial community structure changes with fermentation conditions

Reduced nutrients and non-VFA sCOD under optimal conditions

Abstract

The aim of this work was to study the effect of volatile suspended solid (VSS) and pH on volatile fatty acids (VFA) production from waste activated sludge (WAS) fermentation by means of batch tests. The final goal was to gain insights to enhance VFA stream quality, with the novelty of using WAS with high sludge retention time. Results revealed that the optimum conditions to maximize VFAs and minimize nutrients and non-VFA sCOD are a VSS concentration of 5.9 g/L and initial pH adjustment to pH 10. The WAS bacterial community structures were analysed according to Next Generation Sequencing (NGS) of 16S rDNA amplicons. The results revealed changes of bacterial phyla abundance in comparison with the batch test starting condition.