Sodium silicates are economical, effective, and environmentally responsible chemicals that have been used in water treatment for more than 70 years. Silicates are used in water treatment for corrosion inhibition, iron/manganese control, and as a coagulant aid.

Corrision Inhibition
Sodium silicate can be used in potable as well as industrial water as a corrosion inhibitor. Sodium silicate inhibits corrosion by forming a protective film on metal surfaces to isolate the metal from any further corrosive attack. In addition, the soluble silicates are alkaline so they have an added benefit of increasing the pH of the water. Sodium silicate can be used to inhibit corrosion of cast iron pipes as well as service lines and fixtures to protect the infrastructure as well as to help water utilities meet the requirements of the lead/copper rule. Selection of silicate for this application depends on the pH and alkalinity of the untreated water. (Refer to PQ Bulletin 37-3 for additional information.)

Iron/Manganese Control
Sodium silicate can be used as a sequestrant to prevent colored water in the distribution system from iron and manganese in groundwater. NŽ Sodium silicate is typically used for this application although a more alkaline silicate could be used for a more acidic water source. Sodium hypochlorite is added at the well site to oxidize the iron followed immediately by the sodium silicate which holds the oxidized iron in a colloidal suspension. Manganese is suspended or is adsorbed onto the iron. The dosage level varies on a case-by-case basis depending on the level of iron and manganese in the water, the water hardness, and the detention time in the system and is best determined by a jar test on site. (Refer to jar test procedure)

Coagulant Aid
Activated silica can be used as a secondary coagulant along with a primary coagulant such as alum or ferric chloride to improve the performance of the system. Activated Silica is formed on site by partially neutralizing N Sodium silicate on site, then diluting to a feed solution concentration of about 1% SiO2. Activated silica creates a heavier denser floc which settles faster reducing the turbidity of the water entering the filters, and allowing longer filter runs.
PQ Technical Service Group can support this effort by running jar tests on-site and by coordinating and overseeing plant trials.

Applications
Corrosion inhibition
Iron/Manganese control
Coagulant aid

Recommended Products
Sodium Silicate, liquids
Magnesium Sulfate Heptahydrate

Recommended Literature
PQ Soluble Silicates: For Protection of Water Systems from Corrosion, Bulletin 37-3

Please contact Technical Service more information on this application.