Acidogenic Fermentation at a Thermophilic Temperature from Municipal Sewage Sludge for the Production of VFAs

Abstract

Population growth has increased the generation of solid waste, especially conventional plastics, which are the precursors of major environmental problems. On the other hand, given the complexity of converting large quantities of organic matter contained in the sludge from wastewater treatment plants (WWTP) into value-added products, it is necessary to evaluate alternatives that enhance the production of bioplastics from polymers of polymeric origin. Furthermore, it is necessary to evaluate alternatives that enhance the production of bioplastics from polymers of biological origin. One of these alternatives is the production of Polyhydroxyalkanoates (PHAs) which result from taking VFAs as a carbon source. Therefore, this project aims to evaluate the anaerobic fermentation conditions that maximize the yield of VFA production through laboratory-scale tests. The experimental design was constructed for a working volume of 200 ml, using organic loadings, 4 gVS/L, and 6 gVS/L for digested sludge and 10 gVS/L, and 14 g VS/L for primary sludge, and controlled pH values of 9.0 ± 0.5, 10 ± 0.5 and 11 ± 0.5 at a constant thermophilic temperature of 55ºC. Twelve combinations were used in triplicate with 48 h, 96 h, and 288 h of HRT, including 3 blanks for each combination, considering a total of 144 reactors. The present work reports the optimal conditions that favour the highest production of volatile fatty acids (VFA) in the anaerobic digestion process from primary and digested sludge. The sludges used came from the Salitre WWTP in Bogotá under thermophilic conditions were obtained, where the best production and accumulated yield of VFA were 31224 mg COD/L, and 2, 230 g COD/g VS respectively, produced with primary sludge at 14gSV/L; ph10± 0.5. Copyright © 2023, AIDIC Servizi S.r.l.