Abstract

In the Nile Delta, a complex network of canals collects drainage water from surface-irrigated fields, but also municipal wastewater. The goal of this work was to assess the technical, environmental and financial feasibility of the upgrade of a drainage canal (DC) into either an in-stream constructed wetland (ICW) or a canalized facultative lagoon (CFL), in order to produce a water re-usable in agriculture according to the Egyptian law. The model-based design of the proposed technologies was derived from field experimental data for the ICW and laboratory data for the CFL. Both technologies, integrated by a sedimentation pond and a disinfection canal, led to the attainment of the water quality standards imposed by Egyptian Law 92/2013 for the reuse of drainage water. The life cycle assessment indicated that the proposed upgrade of an existing DC resulted in a decrease of environmental burden for the ICW, or in an environmental impact equal to 0.3% of that of a traditional activated sludge process for the CFL. The cost/benefit analysis (CBA) was based on the assumptions that (i) farmers currently irrigate a non-food crop (cotton) with the low quality drainage water present in the DC, and (ii) thanks to the upgrade to a ICW or CFL, farmers will irrigate a food crop characterized by a higher market price (rice). The CBA indicated that the DC upgrade to an ICW represents an attractive investment, as it leads to a financial rate of return > 10% over a wide range of cotton market prices. Conversely, the upgrade to a CFL is less attractive due to high investment costs. In conclusion, the upgrade of DCs to ICWs appears a promising option for the treatment of drainage canal water in the Nile Delta, thanks to the high pollutant removal performances, low cost and negligible environmental burden.