Ferrous Sulfate for Use in Water Treatment

Ferrous sulfate, also known as iron(II) sulfate, is a compound with the formula FeSO₄(H₂O)ₓ where x can vary between 0 and 7. It’s worth noting that the heptahydrate form (FeSO₄·7H₂O) is the most common and commercially available form of ferrous sulfate. It is used in water treatment primarily as a reducing agent, helping to remove impurities such as manganese, hydrogen sulfide, and other oxidized contaminants from water sources. The ferrous sulfate (heptahydrate form) is bright green to bluish-green in color. Its crystals are usually orthorhombic in shape, but they can also form as scale or powdery material depending on how they are produced and handled.

The (heptahydrate) ferrous sulfate granular particles.

Function in Water Treatment

Here’s how ferrous sulfate works in water treatment:

• Oxidation of Contaminants: Ferrous sulfate is added to water containing oxidized contaminants, such as manganese or hydrogen sulfide. Unlike its counterpart – ferric sulfate, ferrous sulfate, which contains iron in its +2 oxidation state (Fe²⁺), acts as a reducing agent, helping to remove oxidized contaminants such as manganese and hydrogen sulfide by reacting with them to form insoluble solids that can be easily separated through filtration or settling processes.
• Sequestering Agent: It can also act as a sequestering agent, binding with metal ions that can cause water hardness, such as calcium and magnesium, and preventing them from precipitating out and causing scale buildup in pipes and equipment.

The industrial grade ferrous sulfates packaged by tonnage bags.

• Odor Control: Hydrogen sulfide, which has a characteristic rotten egg odor, can be particularly unpleasant in water supplies. Ferrous sulfate helps to oxidize and remove this gas, improving the taste and odor of the water.
• Corrosion Inhibition: By scavenging oxygen, ferrous sulfate can help prevent corrosion of metal pipes and storage tanks in water distribution systems.
• pH Adjustment: In some cases, ferrous sulfate can also help adjust the pH of water to a more neutral level, which can be beneficial for the overall water quality and the effectiveness of other treatment processes.
• Biological Treatment: In wastewater treatment, ferrous sulfate can provide an essential nutrient for microorganisms that break down organic matter, aiding in the biological treatment process.

Feed grade ferrous sulfate for animals.

It’s important to note that the use of ferrous sulfate in water treatment must be carefully controlled to avoid over-treatment, which could lead to iron fouling and the introduction of excess iron into the water supply. Water treatment facilities typically conduct thorough testing and monitoring to ensure that the correct dosage is applied to achieve the desired water quality outcomes without causing any negative impacts.

Production Process & International Standards

Ferrous sulfate is produced through various methods, including as a byproduct in the production of titanium dioxide, steel, and other metals, as well as by direct synthesis where metallic iron or iron ore reacts with sulfuric acid. It can also be recovered from pickling liquors used in metalworking and as a byproduct of coal tar processing. The production process involves concentrating ferrous sulfate solutions and crystallizing them to form hydrated salts, which can be dried for the anhydrous form. Environmental impact and product quality are important considerations in the production of ferrous sulfate.

Potable water & food grade ferrous sulfate.

Based on the applications, ferrous sulfate can be classified as industrial grade, feed grade, potable water and food grade. They can be produced in accordance with a series of international standards including GB/T 664, GB 29211, GB 34465, GB/T 10531, and AWWA B402.