Using In-stream wet-land technique
to enhance agriculture drainage water quality
In response to the increasing population and economic growth, water consumption will also increase and that will increase the competition for water demand between different sectors depending on water such as municipal, industrial, agricultural, and recreational needs. If this trend continues with water withdrawal under the same practices and policies, by 2025 water stress will increase in more than 60%.
The overall annual supply of water from conventional water resources in Egypt is approximately 59.2 BCM. However, 29% of this water is reused to meet the annual demand which is approximately 76.21 BCM, (Barnes J., 2012).
There is a severe shortage in irrigation water supply in the Northern Delta region especially in the tail end of irrigation canals, and it is proposed to substitute shortage in fresh water supply by the available agriculture drainage water
Agricultural drainage reuse is one of the main areas where water is reused in Egypt. However, constant increase in pollution loads in drain waters forms a major constraint under the drainage water reuse policy, where domestic wastewater is discharged directly to drainage canals without any treatment and nowadays many of open drains are carrying a mixture of agricultural drainage water, domestic, industrial wastewater, and solid waste debris. Increasing pollution loads in some drains reduce the capabilities to reuse their water in irrigation. Therefore, the main objective of this research is to enhance water quality in drains to be reused in irrigation purpose using low cost treatment technologies.
Free-Water Surface Constructed Wetland is defined as an area submerged by water, and water slowly flows through the wetlands. The slowly moving water ensures settlement of solids, removal of pathogens and nutrients that are consumed by plants.
In Free-Water Surface Constructed Wetland water flows above ground, exposed to the oxygen and sunlight.
The in-stream wetland is considered a good treatment technology for communities that have a primary treatment facility (e.g. Septic Tanks), where land is very expensive and un-available in Delta region.
The in-stream wetland in brief consists of a sedimentation pond, a wooden gated weir and a steel plants screen that governs a series of floating and emergent aquatic plants reaches. The sedimentation pond is created in the drain inlet by deepening the drain cross section at the sewage water point source to make a settling basin with slow velocity and enough storage capacity to enhance primary retention treatment time in the form of sand and big solid particles and sludge as well.
The control weir is located at drain outlet. Its function is to control drain water depth and the treatment detention time according to pollutant loads. The vegetation system of the drain is located on a certain distance before drain outlet (based on design criteria) and consists of a steel screen for vegetation.
The treatment processes were sedimentation, filtration, biodegradation and nutrient plants uptake as well as pathogens eradication. Effluent water from In-stream systems moves in an open water zone until the drain outlet to enhance oxygen content and water disinfection with the sun light penetration.