The electrical energy consumption of Swiss Waste Water Treatment plants (WWTP) is substantial, approximately 450 GWh per year. Recent studies show an interesting optimization potential of 188 GWh per year. About 40% of the electricity is consumed by the aeration for the biological process. The proposed project offers a new approach to upgrade municipal and industrial WWTPs, using aerobic granular biomass for a more energetically efficient (energy reduction around 10-20%) and a biologically active wastewater treatment process.
The project was carried out in field conditions using on-site pilot plants in order to compare the Puratis aerobic granular process ARGUS with a conventional activated sludge process under continuous and batch conditions. The results obtained were used to prepare a mathematical model, which describes the process and evaluates the energy efficiency potential of the ARGUS process.
The crucial element in the ARGUS process is the quality of the microbial community, which directly affects the process and energy efficiency. A higher percentage of nitrifying community is the principal factor influencing the competitiveness and energyadvantage of the ARGUS process compared to the conventional activated sludge process.
Taking into the account that nitrification needs about 5% of the aeration energy the mean energy consumption for nitrification will then be 9 GWh per year when all WWTPs in Switzerland will be equipped with a nitrification process.
With the ARGUS process, it is possible to reduce the energy demand for nitrification in about 50% or 4.6 GWh per year in case that all WWTPs in Switzerland install ARGUS process. Additionally, a 10% of COD reduction might increase the saving potential to 40-50 GWh per year in case that all municipal plants apply ARGUS process.
Even though these numbers are hypothetical, they reflect the potential of the ARGUS process to contribute to the energy saving in the municipal domain and not only a more process-efficient but also an energy-efficient wastewater treatment process can be achieved.
This report provides the overview of all achieved results on the course of the project and evaluates the potential of the ARGUS process. The results also serve as the technical basis for a future project follow-up.
