Water availability has become increasingly limited worldwide, to the point that aquifers and groundwater are being over-exploited. Aquifers are hydraulically connected porous formations that can interact with surface water, appearing as natural springs and wetlands. Aquifers recharge naturally from rainfall, from other aquifers with higher piezometric levels and from river losses.
There are two main problems associated with abstraction and the depletion of aquifers:
• Saline intrusion or salinisation, which affects groundwater quality. It does not reduce the quantity of water but changes its composition. For example, mixing just 5% seawater with the freshwater in an aquifer makes it unusable for municipal, industrial or agricultural use.
• Loss of wetlands and natural springs.
Using treated wastewater for aquifer recharge is one of the best ways to remedy the effects of aquifer depletion and salinisation.
Its importance will grow in the near future as climate change directly affects water availability.
The main aims of artificial aquifer recharge are to increase aquifer resources without altering water quality, to offset the loss of natural recharge caused by activities in the area and to create a hydraulic barrier against saline intrusion in coastal aquifers.
How can aquifers be recharged?
• Infiltration basins are one of the most common and simplest methods, requiring an excavation in a permeable area close to the water source, in this case the reclaimed water treatment plant. Construction and maintenance costs are low, the facilities have a long service life and infiltration rates are easy to monitor. The only drawback is that they need large areas of land.
• Trenches. Trenches significantly reduce erosion and retain run-off, increasing natural infiltration. The area must have a soft surface layer; they cannot be built on heavily eroded ground.
• Deep recharge wells. This type of artificial recharge is used when the ground has low permeability, which makes surface recharge impossible.
At KEIKEN ENGINEERING we promote water reclamation and reuse to reduce environmental impacts and increase water availability without exploiting conventional sources. Advanced water reclamation treatment must be tailored to the characteristics of each water and the intended end use. These are specialist treatments that must be carried out by experts with high-quality equipment.
There are already aquifer recharge schemes in Spain, such as the full-scale project in Port de la Selva, Girona. There, high-quality effluent is discharged into the local stream a few metres before it reaches the sea, preventing the saline intrusion caused by summer over-abstraction from the supply wells. The municipality also built a reclaimed water network to supply irrigation water to private gardens. Finally, thanks to the European DEMOWARE project, reclaimed water is used outside the summer months to recharge the aquifer that supplies the town (source: DEMOWARE).
Examples of advanced treatment for water reclamation include disinfection of pathogens in wastewater treatment works effluent, filtration (through filtration media such as activated carbon, anthracite and/or garnet) and screening, among others, depending on the effluent characteristics and the required final quality. KEIKEN can design and build these installations, including water reuse plants.
For our services or more information, email info@keiken.es or contact us.
