Assessing the potential of renewable energy sources (biogas and sludge) in a full-scale UASB-based treatment plant

This study aimed at evaluating the energy potential of the by-products (sludge and biogas) produced in full-scale UASB-based sewage treatment plant (STP). The work was developed at the Laboreaux STP (Population = 70,000 inhabitants), located in the city of Itabira, in the state of Minas Gerais - Brazil. To determine the biogas energy potential, the volumetric production and its composition were monitored. The dehydrated sludge from filter press was characterized according to immediate composition, elemental composition, lower calorific value (LCV) and higher calorific value (HCV). Overall, the gross energy potentials of the biogas and sludge produced in the STP were 7518 MJ d−1 and 10,962 MJ d−1, respectively. Considering the use of biogas to produce electricity (efficiency of 30%), it could be possible to supply 57.6% of energy demand of STP. With a thermal treatment of sludge from filter press, with or without energy recovery, it would have a reduction of mass disposal in the landfill in the order of 46.0% that represents a benefit in the sludge management.