Fermentation batch test experiments using urban wastewater and sewage sludge

Volatile fatty acids (VFA) from sewage sludge are a promising feedstock for Polyhydroxyalkanoates (PHA) production. However, the cost-effective production of high-quality VFA streams (in terms of nutrients and non-VFA soluble chemical oxygen demand, sCOD, concentrations) still remains a challenge. With this regard, laboratory batch tests can allow to better understand how improve the VFA quality. In this paper, bench scale batch reactors were set-up to investigate the effect of volatile suspended solid (VSS) concentration and pH on the VFA rich stream formation; the final goal is to maximize the PHA production. The bacterial community structures have been analysed according to Next Generation Sequencing (NGS) of 16S rDNA amplicons. Results have 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 pH 8.