Wastewater treatment and energy valorisation in small wastewater treatment plants

This dissertation aims to find ways to improve environmental and energy performances of three small wastewater treatment plants (WWTP). These WWTP, placed in Sintra municipality, were case studies for the identification of corrective measures and solutions in order to improve their environmental and energy performance. The settings of these three WWTP was obtained by an audit exercise, performed under a specific methodology for small WWTP. After this assessment were proposed corrections and solutions for all identified improvement opportunities. Were also discussed solutions for the treatment of sewage sludge, due to the actual problems resulted by its disposal and to take advantage of its energy valorisation potential. Was presented as case study, a sludge thermal treatment and its energy valorisation by gasification. This specific case study was occurred in a pilot gasification reactor in San Sebastian, Spain. Another theme discussed on this dissertation was the possibility to provide energy autonomy for small and isolated WWTP using renewable energies, in this specific case, wind energy. Was studied the wind availability and pattern, for the region of Magoito, where Magoito WWTP is placed. This study was supported by Wasp software, analysis of meteorological databases for the region and by the collection of data provided by an on-site a meteorological station, placed on Magoito WWTP. The state of the art on wastewater treatment technologies and sludge treatment and valorisation, for small WWTP, was also compiled, as well as an overview of the main Portuguese and European legislation and European policies on this subject