Evaluation of fog and rain water collected at Delta Barrage, Egypt as a new resource for irrigated agriculture

Abstract

Alternative clean water resources are needed in Egypt to face the current water shortage and water quality deterioration. Therefore, this research investigates the suitability of harvesting fog and rain water for irrigation using a pilot fog collector for water quantity, water quality, and economic aspects. A pilot fog collector was installed at one location at Delta Barrage, Egypt. Freeze liquid nitrogen was fixed at the back of the fiberglass sheet to increase the condensation rate. The experiment was conducted during the period from November 2015 to February 2016. In general, all physicochemical variables are observed with higher values in the majority of fog than rain water. The fog is assumed to contain higher concentrations of anthropogenic emissions. TDS in both waters collected are less than 700 mg/l at sodium content less than 60%, classifying these waters as good for various plants under most conditions. In addition, SAR calculated values are less than 3.0 in each of fog and rain water, which proves the water suitability for all irrigated agriculture. Al and Fe concentrations were found common in all samples with values less than the permissible limits of the guidelines. These metals originate from soil material, ash and metal surfaces. The sensitive heavy metals (Cd and Pb) were within the permissible limits of the guideline in fog water, indicating this water is suitable for irrigation. On the contrary, rain water that has heavy metals is not permitted in irrigation water as per the Egyptian law. As per WQI, the rain water is classified as good quality while fog is classified as medium quality.Regarding the water quantity, a significant increase in the harvested fog quantity was observed after cooling the collector surface with freeze liquid nitrogen. The current fog collector produced the lowest water quantity among different fog collectors worldwide. However, these comparative results confirmed that quantity is different from one location to another worldwide even in the same country. The cost of the unit water volume of harvested water by the current pilot collector is relatively low among different collectors worldwide.This study proves that fog harvesting in Egypt is feasible using the current pilot collector in terms of water quantity, water quality, and economy. But it recommends collection of fog at various locations and times, since both water quantity and water quality are variable in time and space. It is more or less viable solution to meet the shortage of water in Egypt.