An Innovative Remote-Controlled Device for Reducing Energy Consumption and GHG Emissions From Water Resource Recovery Facilities

Cecilia Caretti¹, I. Ducci¹, F. Spennati², P. Aloisi³, M. Spizzirri⁴, S. Dugheri⁵, and R. Gori¹

1. Civil and Environmental Engineering Department, University of Florence, Italy

2. Consorzio Cuoiodepur SpA, Italy

3. West Systems Srl, Via Mazzolari 25, 56025 Pontedera (PI), Italy

4. Acea Spa, P.le Ostiense 2, 00154 Rome, Italy

5. Experimental and Clinical Medicine Department, University of Florence, Italy

Abstract: Water Resource Recovery Facilities (WRRFs) are sources of direct emissions of greenhouse gases (GHGs) and volatile organic compounds (VOCs) produced by biological processes and indirect GHG emissions from the energy necessary for operating the treatment processes. The direct emissions also contribute to odour issues of WRRFs. Biological tank aeration accounts for 50-60% of the total energy consumption of WRRFs. The development and implementation of innovative tools for reducing WRRF carbon footprint by optimizing the efficiency of aeration processes are therefore important goals for WRRF environmental sustainability. The innovative solution proposed in this study consists of an automated self-moving prototype (LESSDRONE) for real-time monitoring of the oxygen transfer efficiency (OTE) and GHG emissions of the aerated tanks under operating conditions, and a protocol for converting LESSDRONE measures and specific WRRF data into actions aimed at minimizing carbon footprint and energy demand. The prototype made it possible to independently carry out continuous tests to measure OTE, GHG concentrations, VOCs, odourants and off-gas flow rates throughout entire tanks under different operating conditions. It was therefore possible to assess the spatial and temporal variability of the measured parameters. Based on the results obtained for different airflow rates and dissolved oxygen (DO) concentrations in the tanks, optimal WRRF process conditions and the parameters most affecting GHG emissions and OTE were identified. The benefit of new air diffusive membranes and cleaning processes on aeration efficiency and effectiveness was assessed.

Key words: aeration efficiency, energy saving, GHGs, odour, VOCs, WRRFs