Potential appraisal of drainage water reclamation and indirect reuse for irrigation in the Nile Delta, Egypt.

Sustaining freshwater supplies has become a global challenge, especially for arid and semi-arid countries. Egypt is now categorized as a water-scarce country facing an exacerbated water deficit. Thus, it has recently adopted a strategy for recycling agricultural drainage water (ADW) to fulfil the irrigation water requirements. This study aims to appraise the feasibility of reusing ADW in the Nile Delta. Accordingly, water samples were gathered from six irrigation streams in a district where mixing stations are intensively installed. The hydro-chemical analysis of 23 water quality parameters sufficiently aligned with the local tolerance limits for the ADW indirect reuse. Nine indicators, including ratios of adsorption, soluble and exchangeable sodium, permeability index (PI), Kelly's ratio (KR), and magnesium hazard (MH), along with the irrigation water quality index (IWQI), were estimated to measure the water suitability for cultivation purposes. The ADW was unfavorable for irrigation due to excess salts, sodium, and chloride, which can cause soil salinization and yield reduction. The blending approach of the ADW with canal waters was critical to retrieving highly suitable irrigation water, saving a significant proportion of the water requirements, and increasing irrigation efficiency. The potential to reclaim and reuse the ADW through membrane-based desalination was promising. However, reverse osmosis (RO) membranes were superior in recovering more suitable water than nanofiltration (NF) membranes. The findings offer insights to water managers on feasible solutions to meet increasing water demand. Conjunctive adoption of recycled water with groundwater for ongoing reclamation projects in Egypt is advocated.