Kinetic modelling-based control strategies to optimise the solar chloro-photo-Fenton process to meet new challenges in wastewater reclamation (CAFIRA)

Increasing urban development and climate change have generated a growing concern among the scientific community for feasible and effective solutions to address global water scarcity. The reuse of effluent from municipal wastewater treatment plants is one of the most effective and sustainable options. To facilitate the safe reuse of reclaimed wastewater, the new European Regulation on minimum requirements for water reuse, applicable from June 2023, establishes a classification of different qualities of reclaimed water depending on the use and method of irrigation in terms of disinfection limits. In addition, it includes a risk management plan to promote the identification and assessment of potentially hazardous agents, such as potentially hazardous pollutants of emerging concern. Therefore, there is an urgent need to develop new sustainable alternatives to conventional treatments, as it is required to avoid the formation of hazardous disinfection by-products and to remove micropollutants, which is not possible with the usual chlorination treatment. To address this challenge, a new strategy based on the new solar chloro-photo-Fenton solar (CFFS) process is proposed. This process consists of the operation of the solar photo-Fenton process at neutral pH with the simultaneous addition of hydrogen peroxide (H₂O₂) and sodium hypochlorite (NaClO). The combination of the bactericidal power of NaClO with the ability of the photo-Fenton process to remove micropollutants allows both objectives to be achieved by reducing the treatment time compared to other solar processes. For the future implementation of the process on a commercial scale, a holistic vision integrating chemical and economic-environmental phenomenology is essential. The CAFIRA project is based on the hypothesis that it is possible to optimise the performance of the CFFS process using control strategies based on kinetic modelling of the inactivation of microorganisms and removal of micropollutants. In this context, the overall objective of the CAFIRA project is the development of a mechanistic model of the CFFS process to control and optimise the continuous operation of raceway reactors for wastewater reclamation in compliance with Regulation (EU) 2020/741, from an economic-environmental sustainability approach. To this end, the following specific objectives will be addressed:

• Investigate the effect of combining the oxidizing power of H₂O₂ and NaClO on the inactivation kinetics of pathogenic microorganisms and micropollutant removal by the CFFS process with different iron complexes.
• Develop a mechanistic model of the CFFS process to predict the removal of micropollutants and inactivation of microorganisms covered by Regulation (EU) 2020/741.
• Design and evaluate the performance of a control approach for continuous flow operation of the CFFS process.
• Economic valuation of the environmental benefits of the CFFS process.