Post-treatment is critical to the entire water treatment process as its design specifications need to be carefully tailored to meet the specific compliance specifications of the client.
Post-treatment of the product water as it leaves the reverse osmosis process is usually designed to meet the compliance specifications for the end-use application.
The most common post-treatment to a reverse osmosis process is to incorporate a means of disinfection to render the water safe to drink. Disinfection through chlorination is the common method of post-treatment, although other options such as UV irradiation and ozone exist.
Designing the Right Post-Treatment System
Often, the product water is very low in minerals and alkalinity due to the high efficiency of the reverse osmosis system. This can result in a potentially corrosive product. A post-treatment control mechanism is to increase the alkalinity and the mineral content of the product, usually through the addition of dosed quantities of mineral carbonates or mineral hydroxides.
For certain industrial applications, the ionic concentrations may be required to be lowered further to produce ultra-low salinity water. Through the addition of an extra post-treatment step that incorporates technologies such as EDR (electro-dialysis reversal), the ionic content of the product water can be reduced significantly. Treatment of condensate, often referred to as condensate polishing, is an application where the production of ultra-low salinity water is required.
An additional post-treatment process is through a de-carbonation process that is employed to elute carbon dioxide from product waters rich in carbonic acid content. The carbonic acid is formed when acid is added in the pre-treatment process to feed water that is elevated in bicarbonate. A similar type of de-gassification process can be employed for sulphide removal.
Post-treatment to the reverse osmosis process can be as simple as pH correction to achieve the required acidity or alkalinity of the product water, to a series of sequential processes to achieve a nominated product quality, for specific industrial or commercial usage.
As is required in pre-treatment processes, an expert-designed post treatment process will deliver performance at an efficiency that is aligned to the reverse osmosis technology production rates.
Septech’s in-house specialists deliver expert designs to achieve a fully-integrated solution of pre-treatment, reverse osmosis and post treatment technologies to provide optimum total plant efficiency.