Waste Water Treatment Plants as Regional Energy Cells – Evaluation of Economic and Ecologic Potentials in Austria

Abstract

Waste water treatment plants not only treat waste water, they can also act as a source of energy. The produced energy is either used to fulfil in-house energy requirements or fed into public energy distribution grids. Research in Austria and other countries has shown that waste water treatment has high energy potential which is yet unexploited. The project “Integration of Wastewater Infrastructure into Regional Energy Supply Concepts” is a national Austrian project which deals with the investigation of energy potentials from waste water treatment. An integration of energy production systems at waste water treatment plants into energy networks to meet energy demands of urban areas can foster economically feasible use of so far wasted energy. In this study the waste water energy system will be optimised using Process Network Synthesis (PNS), based on the p- graph method. PNS-Studio (2011) is utilised to perform this optimisation. Starting from a maximum structure of all possible technological options the programme calculates an optimum energy network as a solution. The ecological evaluation of the scenarios is executed with Sustainable Process Index (SPI) methodology. A free online tool SPIonWeb (2014) is used to calculate ecological footprint of energy production process. The paper discusses the economic and environmental aspect of the PNS-Studio calculations and the different fields of application for the produced resources (heat, electricity and biogas), using a real world case study. Furthermore the approach of integrated waste water treatment plants into regional energy supply infrastructure will be explained.