Conventional WWTP are big energy consumers. This is an issue in terms of operation costs and a concern as global climate change constitutes a serious problem. Simultaneously, water scarcity constitutes a growing worldwide issue.
This thesis accesses the possibility of reaching energy neutrality and reducing operation costs in Espinho WWTP, by means of optimization of the treatment line, in a cost-effective manner. Moreover, the economic feasibility of providing tertiary treatment to the secondary effluent, in order to reclaim water for irrigation, is also investigated here.
It is presented an evaluation of possible processes, that could be implemented, that reduce the energy demand, such as CEPT, as well as methods for increasing the energy production in a treatment plant, like anaerobic digestion, co-digestion or the installation of photovoltaic (PV) solar panel modules. The latter is nowadays starting to be a requirement in the design/construction of new sizeable WWTP.
Adjacent to the WWTP, there is a golf course, which demands 200,000 m3/y of water for irrigation. The water reclamation is seen as a possible to strategy to supply the needs.
The design of each treatment phase of Espinho WWTP is verified, both when operating with conventional primary treatment and chemically enhanced primary treatment (CEPT). Jar-tests with Espinho affluent wastewater were conducted, and the optimum PAX18 coagulant dosage determined was 15 mg/L, to perform CEPT.
The methods studied contribute to improving the energy efficiency of a WWTP and are presented as possible approaches to progress in the direction of energy self-sufficiency. The operation costs, as in reagents and energy, were calculated prior to the WWTP optimization and following each possible upgrade.
CEPT demonstrates to reduce the energy consumption of the aeration process by approximately 40%. On the other hand, co-digestion proves to boost the energy production in the anaerobic digestion considerably, by 84% to 154%. Additionally, PV solar panel modules have shown to supply 10% of Espinho WWTP energy demands. The implementation of the studied methods allows the WWTP to produce 68% of its total energy needs
