This process could involve extracting water from rivers, lakes, wells, boreholes, or seawater.
If the water is being extracted from a river, for example, the pre-treatment required will depend on the time of year that extraction takes place. Solids and sedimentation occur after heavy rainfall causing chocolate coloured water from turbulence.
This would then require a lot of pretreatment to make this water usable.
Normally when using river water, a coagulating chemical is added.
This facilitates a flocculating effect before going onto the next stages using lime and chlorine.
To continue the pre-treatment, a sand or multi-media filter would be used, followed by the dosing of a scale inhibitor.
Following on with pre-treatment processes in this example would, therefore, include a heat exchanger, de-chlorination, filtration, reverse osmosis, storage tank, degas, mixed bed ion exchange, and condensate storage to feed the boiler for a power station.
Additional stages of water filtration may be added to the above system depending on the desired end result for purity levels.
The higher the purity level required, the more stages of pre-treatment necessary.
In today’s advancements in water treatment technology, water treatment companies around the world are using ultrafiltration, nanofiltration, and reverse osmosis tech-niches to improve water quality.
Ultrafiltration systems are used on many seawater desalination plants around the world as a pre-treatment process. Ultrafiltration can remove contaminants such as silt and algae
without the need for dosing chemicals such as chlorine and flocculants. Ultrafiltration will provide absolute barrier protection against water-borne diseases.
This is a very important pre-treatment requirement when using a reverse osmosis water treatment system.
It is necessary to remove all contaminants that can cause fouling of membranes, as downtime costs time and money to the operators of desalination plants. When the pre-treatment systems fail, it can cause front end or back end problems with the membranes. We can always use the mass balance equation to calculate the health of a desalination plant, provided all data was documented from new. we can carry out profiling of the membranes to make sure that all of the membranes in the pressure vessel are producing the correct levels of purity.