Wastewater treatment requirements for effluents used for agricultural irrigation are considerably different from those of effluents discharged to aquatic environments. For example, nitrogen and phosphorus are essential elements for plant cultivation and therefore exhaustive processes for reducing nutrients (i.e. denitrification and phosphate removal) are not imperative in wastewater reuse for irrigation. Conversely, the capacity of human pathogens and antibiotic resistance genes to persist on and potentially colonize plant tissues, as well as evidence of the uptake of various contaminants of emerging concern (CECs) by crops makes treated wastewater irrigation a potential public health hazard because these elements can be transferred to humans and animals through the food chain. In addition, the detrimental long-term effects of effluent-derived salinity and CECs on soil structure and crop yield in treated wastewater irrigated fields (especially in clay-rich soils) suggest that salt removal may be crucial when irrigating with wastewater effluents. Also, classical wastewater treatment practices need to be revisited in the context of wastewater reuse so as to consider different effluent quality obligations.
This project adopts a circular economy approach, aiming for safe and sustainable valorization of wastewater for irrigation, with minimized ecological and agronomic impacts. The overall concept is to develop cost-effective modular, de-centralized wastewater treatment/irrigation systems coupled to decision support tools that enables coupling/decoupling of treatment modules for the removal of pathogens, CECs and salinity as a function of the wastewater source and measured quality parameters, to ensure optimal reused water quality for irrigation and long-term sustainability of irrigated soils. Individual modules within these networks (compiled based on specific requirements) will be coupled to alternative energy sources to reduce costs and greenhouse gas emissions.
The above concept will focus on seven wastewater treatment modules. Two novel decentralized secondary treatment modules, three energy-efficient advanced treatment modules specifically designed to remove microbial and chemical contaminants and two units designed to remove salinity. A key component of this project are the decision support tools for the application of post treatment desalination and pathogen intervention, which requires efficient data transfer, processing and harmonization from online and offline monitoring sources. The monitoring will rely on a comprehensive diagnostic toolbox, which will not only evaluate the quality of the effluents from individual and integrated modules, but also their impact on soil quality, ecosystem functioning and agronomic performance.