The reverse osmosis process is used to remove inorganic salts, known as total dissolved salts, from brackish, sea and treated waste water. It is a high pressure driven membrane filter process that filters contaminants as small as 0.0005 micron.
There are two common membrane module configuration types for reverse osmosis applications; hollow fiber and spiral wound. Two other configurations, tubular and plate and frame, can also be used but are best suited for special applications such as the food and dairy industries.
ABCO reverse osmosis water treatment plants are typically equipped with spiral wound membranes. These membranes are suitable for most qualities of bore water treatment, however can require some pre-filtration to remove particulates greater than 10 micron.
ABCO reverse osmosis plants are fully automated to maintain a constant body of quality potable water. They are typically equipped with a pre-treatment (or raw) and post-treatment (or treated) water tanks.
The PLC-driven automated control detects when the treated water tank is running low and, providing there is a sufficient quantity of water in the raw water tank, begins the filtration process. The by-product (or reject) water is piped away from the plant, typically to a holding pond. From the holding pond, ABCO encourages the re-use of this water. In a mine setting this re-use could come in the form of irrigation or dust suppression.
The reverse osmosis water treatment requires a number of chemicals to assist the water treatment process; an anti-scalant, chlorination and a pH adjusting solution. Depending on the source and composition of the supply water, a pH adjusting solution such as hydrochloric acid (basic supply) or sodium hydroxide (acidic supply) should be used to regulate the water's pH to around 7.2.
Chlorination is usually achieved by dosing standard pool chlorine (a 12% Sodium Hypochlorite solution). Anti-scalant solutions are specially made by certain chemical manufacturers and are typically a liquid solution of complex polymers. Reverse osmosis water treatments plants require a chemical cleaning of membranes every 6 to 12 months. This figure can be reduced to as high as every two weeks based on the quality of the water supplied, as well as the effectiveness of the anti-scalant dosing system.
The chemicals used for cleaning are a combination of highly acidic (~pH 1) and highly basic (~pH 14) solutions. Typically these chemicals are concentrated hydrochloric acid (32%) and sodium hydroxide. The volumes of liquid required vary based on the size of the system and the extent of membrane fouling. ABCO provides a consultation service which can assist in finding the right solution for your plant.
While most systems are fully automated there is a requirement for monitoring of influent and effluent flows and quality to ensure the correct operation of the membranes. These investigations may reveal the need for; adjustment of chemical dosing rates, adjustment of the chemicals themselves, further filtration of raw water, as well as indicating the need for a chemical clean of the system. As with all plant, ABCO suggests a quarterly service to ensure the continuous success of any reverse osmosis treatment plant.
For more information on reverse osmosis water treatment plants please click here.
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