Innovative wireless tool for reducing energy consumption and GHGs emission of water resource recovery facilities.

Newsletter #5.


Procedure development for off-gas monitoring with LESSDRONE

With the sixth measurement campaign carried out at the Cuoiodepur WRRF in June 2020, action B3 has ended. This action is aimed at developing the monitoring procedure of a WRRF through using the LESSDRONE prototype. The following aspects were studied during this action:

  • The off-gas monitoring with LESSDRONE;
  • Process conditions contributing to higher efficiency of the aeration system and reducing the greenhouse gas emissions.
During this action, the monitoring procedure as well as the LESSDRONE itself (both in its software and hardware parts) have been optimized. The experimentation has led to some important results:
  • The LESSDRONE is efficient and versatile thanks to its agility of maneuver and the high degree of automation that reduces the need for presence of personnel during the measurements. It also allows to monitor the entire surface of the oxidation tanks, offering an overall view of the spatial distribution of the monitored parameters.
  • The reliability of the LESSDRONE was verified using the online sensor data and grab sample measurements carried out in the lab. The results showed consistent data quality and helps to deepen the understanding of process operating conditions.
  • The LESSDRONE data allow to introduce mitigation strategies for GHG emissions and energy expenditure of the WRRF through optimizing process operating conditions such as air flow rate, dissolved oxygen concentration, sludge retention time, etc.).
  • The LESSDRONE allows to optimize the aeration system by increasing the oxygen transfer efficiency. In addition, monitoring αSOTE helps optimizing the methods and frequency of the diffusers cleaning and/or replacing.
  • The LESSDRONE guarantees transferability to other WRRFs that work in different operational conditions thanks to its functionality and versatility.
Tests with the LESSDRONE: top left, Eindhoven WRRF; top right and bottom left, Tilburg WRRF; lower right, San Colombano WRRF

Protocol development for reducing energy consumption and GHGs emission

The action B4 includes the development of a protocol for optimization of WRRFs focusing on carbon footprint reduction through minimizing energy expenditure and greenhouse gas emissions.
In addition to the experimental data collected with the LESSDRONE, the protocol takes advantage of using advanced modeling paradigms including:
  • Flow sheet biokinetic modeling.
  • Computational Fluid Dynamics (CFD) modeling integrated with biokinetic model.
  • N2O risk assessment modeling.
The proposed protocol has been applied to the Cuoiodepur WRRF as the first case study. The biokinetic and hydrodynamic models, were properly calibrated and validated, with the aim of simulating plant’s operation and performing scenario analysis based on different operational scenarios. For this purpose, the information and data collected in the previous actions were used (A1, A2 and B3).

The flow sheet biokinetic model, developed by UNIFI, uses a modified version of the ASM1 model, which is the main reference in the field of biological processes modeling. The influent data of the WRRF and the experimental data collected by LESSDRONE have been used as input to the model. The model was calibrated and validated using different historical datasets from the plant and showed an acceptable prediction power.
Biokinetic model: on the left, the layout of the Cuoiodepur plant; on the right, an example of model output and comparison with experimental data.
The hydrodynamics of the oxidation tank has been modeled (by UGENT) using Computational Fluid Dynamics (CFD) integrated with biokinetic model. The model uses the geometric data of the bioreactor, the air flow rate inside the bioreactor and the influent characteristics as input data. The results helped us to describe, with a very high level of detail, the spatial dynamics of the flow, the mixing patterns, and the concentration profile of the different components within the aeration zone.
The CFD-biokinetic integrated model is used to simulate different operational scenarios by varying different parameters like air and influent flow rates. This allows to understand the effect of:
  • Different control strategies (based on dissolved oxygen, ammonium or sludge retention time).
  • Dry or wet weather conditions.
  • Replacement of the air diffusers.
Four scenarios have been selected from which three had different influent flow rate to the bioreactor with constant air flow rate, while for the fourth scenario a reduction in aeration has been simulated as a mitigation strategy to minimize the carbon footprint (CF).
The results of the selected scenarios were compared in terms of changes in the hydrodynamics of the biological tank as well as the performance of the treatment process regarding COD and nitrogen removal. The scenario based on the aeration control strategy was able to demonstrate the potential for CF reduction without compromising the performance of the treatment process.
Integrated CFD-biokinetic model: on the left, the geometry of the Cuoiodepur bioreactor; on the right, an example of the model output for the dissolved oxygen concentration profile in different operational scenarios.
N2O risk assessment modeling allowed to assess the N2O production dynamics in the oxidation tanks of the WRRF.

The emissions of N2O in a WRRF are generally lower than those of CO2 and CH4, but its global warming potential is far greater (298 times) than that of CO2. Consequently, it is essential not only to quantify N2O emissions from WRRFs, but also to investigate the main pathways and parameters that have significant impact on the risk of emissions. The N2O risk assessment modeling framework has been used to predict a risk score for direct N2O emission under operating conditions of the plant. The model uses the historical data of the plant, the output of the flow sheet biokinetic model and the data collected by the LESSDRONE. The results of this step showed high risk of N2O emissions when having too high dissolved oxygen concentration in the aeration zone. This is validated by the actual emissions data collected by LESSDRONE and suggested that the reduction of aeration is indeed a great potential strategy for carbon footprint reduction as was also suggested in the previous steps.
Flow sheet biokinetic modeling, CFD-biokinetic integrated modeling, and N2O risk assessment modeling framework, are also being applied to the San Colombano (Italy)and Eindhoven (The Netherlands) WRRFs as the next case studies that will be studied in action B5.

With the continuation of the measurement campaigns in selected WRRFs, further data and information will be collected that facilitate the path to development of the final protocol.

Application of the protocol in selected WRRFs

The LESSDRONE, after it has been tested on the Cuoiodepur WRRF, has also been applied to other types of WRRFs:
  • The first measurement campaign at the San Colombano WRRF (Florence, Italy) was carried out in July 2020;
  • The measurement campaigns at Eindhoven and Tilburg WRRFs (Netherlands) were carried out in September and October 2020;
  • The first measurement campaign at Roma Est WRRF (Italy) was launched in January 2021;
  • Further measurement campaigns are planned at the Roma Est WRRF, the Genova Sestri Ponente WRRF (Italy) and the San Colombano WRRF by summer 2021.
The dissemination and networking actions continue regularly.
Article published in the technical-scientific journal Ingegneria dell’Ambiente

An article on the experimentation of the Lesswatt project was published in the technical-scientific journal Ingegneria per l'Ambiente (n.2 / 2020). The article can be downloaded for free from both the magazine website and the Lesswatt project website.

The LESSWATT project was presented at the Industrial Union of Pisa

As part of the conference "Dove saremo tra dieci anni? Le sfide del clima e le risposte del tessuto economico locale" held on 8 October 2020 at the Industrial Union of Pisa, CUOIODEPUR, partner of the Lesswatt project, illustrated the project, the progress of the research and the results achieved to date.

Second workshop of the Lesswatt project at ECOMONDO 2020

The LESSWATT project took part in the ECOMONDO 2020 international fair in Rimini with the workshop entitled “Il controllo della carbon footprint degli impianti di depurazione: il progetto Lesswatt”. The slides of the conference can be downloaded for free from the Lesswatt project website. 

The LESSWATT project at the FAST 2020 webinar

The LESSWATT project was presented at the free webinar entitled "Automazione di processo per gli impianti di trattamento delle acque di rifiuto" organized by FAST (Federation of Scientific and Technical Associations) and held on 3 December 2020. The slides of the conference can be downloaded for free from Lesswatt project website.

To follow the progress of the project and the initiatives promoted, we invite you to consult the website ( For detailed information on the technical activities, send an e-mail to the following address: 
Contact: Cecilia Caretti
Civil and Environmental Engineering Department (DICEA)
University of Florence - Via S.Marta, 3 – 50139 Florence, Italy
Tel. +39 055 2758850
Copyright © 2021 Lessawatt Project, All rights reserved.

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