Engineering techniques

Groundwater abstraction optimization: A straightforward step to control salinization is technically optimizing of the groundwater abstraction. In coastal aquifers prone to lateral seawater intrusion and up-coning, inland movement of the groundwater wells and the use of shallower wells decrease the salinization rate. Special fractional or skimming wells only abstract from possibly thin layers of fresh groundwater overlying resources that are more saline.
Tidal Barriers: Another group of measures is aimed at physically blocking the movement of salts. In various areas in the world tidal creeks, river estuaries and other sea inlets enormously enlarge the length of the coastline and thus the contact area between the coastal aquifers and seawater. Blocking these sea inlets with dams or barriers obstructs seawater flowing into the inlet and reduces the seawater intrusion potential in that area.
Subsurface barriers or impermeable screens are developed that block the landward underground movement of seawater. Materials used to construct such barriers are slurry walls, bio-walls, grout cut-offs, and steel sheet piles. Subsurface barriers can also be developed with hydraulic screens. In these screens, artificially increased groundwater pressures in the freshwater aquifer and /or decreased pressures in the saltwater part of the aquifer prevent the salt water flowing in.
Aquifer Storage and Recovery (ASR): A different approach the artificial recharging of aquifers with fresh groundwater. The recharge increases the groundwater pressure often reversing the pressure gradient caused by coastal groundwater abstraction. This acts as a hydraulic barrier preventing the movement of the saline groundwater. The fresh water that is recharged may have various sources like harvested rainwater, river runoff, treated (desalinized) waste water, irrigation return flow and even seawater. Obviously, it only makes sense to recharge the freshwater when there are no alternative more urgent needs for that water. ASR can first of all be approached as a storage technique where the aquifer is used as an underground reservoir. surface water reservoirs. Secondly, ASR can also be approached as a recovery technique. Aquifers that are already salinized and rendered unsuitable for groundwater development can be (partially) recovered by flushing the dissolved salts from the groundwater system.
Reduce water-logging induced salinization: Water-logging induced salinization occurs in areas with shallow groundwater tables and high evaporation rates. The evaporation acts as a fractionation process. When the saline water evaporates, basically only water molecules and volatile constituents change into the gaseous phase. The dissolved solutes remain behind in the non-evaporated water increasing the TDS content. Reducing this type of salinization is done by either increasing the groundwater table depth or decreasing the evaporation rate or a combination of both.
Saline effluent treatment: Drainage effluent from intensive cropping irrigation areas, industrial effluent and domestic wastewater may contain very high salt contents. Uncontrolled disposal or release of these waters may lead to introducing salts into the groundwater system. In order to prevent this type of salinization the following steps are undertaken in many locations around the globe. First of all the volume of effluent produced and the level of salinity in the effluent should be kept as low as possible. Secondly, the collection and transport system of the saline effluent should be constructed and maintained such there is no non-intended seepage from it. Prior to the effluent entering the groundwater system (e.g. since it is re-used as irrigation water) it should ideally be purified and the salts removed by desalinisation techniques.
Desalinisation of saline (ground)water: Desalination processes separate dissolved solutes from brackish and saline feedwater by means of phase-change processes (distillation, freezing) or membrane processes (reversed osmosis, electro-dialysis, nano- and ultra-filtration). This process needs relatively advanced technologies and is energy-intensive.