Innovation in water regeneration by solar chloro-photo-Fenton on a demonstration scale (INACUA)

The effects of urban development and climate change have led to a scenario of generally increasing water scarcity. The extreme situation in which Andalusia finds itself has led to the implementation of extraordinary measures to seek innovative solutions to deal with the consequences of the drought. One effective and sustainable solution is the reuse of effluent from municipal wastewater treatment plants (WWTPs). To promote the safe reuse of reclaimed wastewater, the new European Regulation on minimum requirements for water reuse establishes a classification of different qualities of reclaimed water according to 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 pollutants of emerging concern, which have not yet been regulated. Therefore, there is an urgent need to develop new sustainable alternatives to conventional treatments, avoiding the formation of disinfection by-products (DBPs) and removing micropollutants, which is not possible with chlorination. To address this challenge, a new strategy based on the operation of the solar photo-Fenton process at neutral pH with the simultaneous addition of hydrogen peroxide (H₂O₂) and sodium hypochlorite (NaClO) is proposed. 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, thus reducing the treatment time compared to other solar processes. However, with a view to commercial application, the operational feasibility of the continuous flow process needs to be investigated, along with the monitoring of disinfection by-products. Furthermore, empirical modelling of the process is a feasible and robust alternative for the control and optimization of the operation of demonstration photoreactors. In this context, the INACUA project focuses on the application of the chloro-photo-Fenton process in continuous solar reactors equipped with novel operation and control tools to regenerate wastewater for reuse in agricultural irrigation according to Regulation (EU) 2020/741, without harmful DBPs. To this end, the following specific objectives will be addressed:

• Phenomenological study of the solar chloro-photo-Fenton process at pilot scale.
• Assessment of the operational feasibility of the process at demonstration scale.
• Empirical modelling of the process.
• Design of a control strategy to optimize the continuous flow operation.
• Implementation of the control strategy on a demonstration scale.
• Evaluation of the economic viability of the process from the perspective of environmental sustainability.