In service, water flows from the feed to the concentrate end of the element, passing through the feed spacer. A portion of the feed flow passes through the membrane surface to the permeate side. This permeate flows through the permeate collector tube. Collected permeate flows through the central tube, and possibly through the permeate tubes of connected elements, to exit the permeate connection of the pressure tube.
Degasifiers (3) are used primarily to remove hydrogen sulfide (rotten egg odor) and carbon dioxide gases which are not removed in the membrane process. If the hydrogen sulfide and carbon dioxide gases are not removed from the product, the odor and taste of the finished water will be undesirable to the customers.
Sodium hydroxide 50% (caustic soda) is used to raise the product water pH. By increasing the pH, the chemically unbalanced water becomes more stabilized which greatly increases the life of the distribution system.
Fluoride (hydrofluorsilic acid 23%) is added to the product water for dental health consideration.
Corrosion inhibitor is added to the product water for corrosion control. Currently we are using a zinc ortho-phosphate product.
Chlorine is added to the product water to protect against
micro-organisms that may be present in the water.