Mohamed Bayoumi* describes the innovative use of wetland foliage in purifying polluted waters for reuse Egypt has succeeded in extending piped water to more than 95 per cent of the population; however, the sanitation extension programme is lagging far behind. According to official figures, while 60-70 per cent of the urban population has access to proper sanitation systems, only four per cent of the rural population does. In the absence of proper sanitation systems in rural Egypt, most of the wastewater is either leaked into the shallow groundwater from open and malfunctioning septic tanks or is directly discharged as raw sewage into agricultural drains, thus polluting both ground and surface waters. The pollution of ground water is localised but difficult to treat, while discharging sewage in agricultural drains widely spreads pollution to large areas across the country through surface water. This obviously increases health hazards and diminishes opportunities for reusing agricultural drainage water in irrigation. Furthermore, agricultural drains carry the pollution load to the Mediterranean Northern Lakes, such as Manzala and Burulus, that used to be the main source of fish production in Egypt. Eventually the polluted water ends up in the Mediterranean Sea that is an international water facility. It is economically infeasible and beyond the capacity of the state to imagine that traditional costly sewage networks and wastewater treatment technologies will solve the sanitation problem, especially for rural Egypt. Alternatively, the solution rests in the application of low cost and on-site wastewater treatment technologies. Before implementing these technologies, they need to be adapted to the local diversified geographic and demographic physical conditions that vary from one region to another within rural Egypt. In this context, "engineered wetlands" appear to be one of the cheap natural wastewater treatment technologies appropriate for treating large amounts of drainage water wherever sparse land is available. The Egyptian Environmental Affairs Agency (EEAA), UN Development Program (UNDP) and the Global Environment Facility (GEF), have collaborated on the introduction and demonstration of an engineered wetland for treating agricultural drainage water that is mixed with sewage and industrial waters. A facility was constructed on 60 acres at the end of Bahr El-Baqr drain, south of Port Said, before it discharges its load into . The engineered wetland is located in the middle of a poor fishermen's community that lacks basic services and whose main business is fish farming using drainage water in Bahr El-Baqr drain. This common practice is producing low quality fish species of high tolerance to pollution that are, in most cases, not suitable for human consumption. Engineered wetlands are an imitation of natural wetlands that are open areas of land occupied by natural vegetation and shallow waters most of the year. Natural wetlands are known for their ability to improve water quality and to alleviate the impact of large tidal waves, river floods and droughts. When water enters at one end of the natural wetland loaded with a high concentration of suspended matter, heavy substances and toxins, it leaves the other end with reduced loads of these contaminants and pollutants, most of which are taken up by reeds. An engineered wetland is constructed as a shallow basin planted with aquatic vegetation that can vary among submerged, floating and emergent plants such as water hyacinth, cattail, papyrus, and duckweeds. Wastewater is introduced at one end and flows over the surface, and is discharged at the other end through a structure that controls the depth of water and retention time in the basin. The selection of aquatic plants along with the slope of the substrate and dimensions of the basin determine the speed at which the water flows through the engineered wetland and consequently the treatment level through its passage. The demonstration facility is treating 25,000 cubic metres per day of the Bahr El-Baqr drain that extends for more than 180 kilometres starting from Cairo and collecting all kinds of wastewater from four governorates until it reaches . The facility design is composed of a large pumping station that lifts water from Bahr El-Baqr drain into huge ponds where sediments are allowed to settle, after which the water flows into a series of engineered wetlands where native plants filter the water, gradually removing at least 75 per cent of its toxins. Following its treatment, a portion of the water is diverted into 60 acres of fish farms, demonstrating that treated water can be safely used in producing clean and high quality fish species. The National Water Research Centre of the Ministry of Water Resources and Irrigation has investigated the use of treated water in the irrigation of field crops. Laboratory analysis and field tests indicated that the quality of the effluent is suitable for the cultivation of all crops. Accordingly, the engineered wetlands technology offers opportunity for expanding the reuse of drainage water in irrigation that will increase overall national water use efficiency. Engineered wetlands are also an appropriate decentralised technology for treating sewage water in summer resorts in the North West Coast and tourist resorts on the Red Sea and in Sinai at a cost of about 10 per cent of traditional wastewater treatment technologies. Additionally, an important application of engineered wetlands would be to clean the northern lakes, if constructed at outlets of agricultural drains inside the lakes, in order to improve the water quality of the lakes. Engineered wetlands, however, are just one of several low cost wastewater treatment technologies that ought to be developed to fit local conditions. * The writer is environment specialist, UNDP, Cairo.
