Besi

Iron (Fe)

1. Basic Information

2. Physical and Chemical Properties

Iron is a silvery-gray metal that is chemically reactive. It forms two main series of chemical compounds: iron (II) or ferrous compounds that are two-valent, and iron (III) or ferric compounds that are three-valent. Iron oxidizes easily in moist air, forming rust, but is stable in dry air. It dissolves easily in dilute acids. Iron has a melting point of 1536°C and a boiling point of 2861°C. Its density is 7.8 g/cm³ at 20°C.

3. Presence in Water and Health Effects

Iron is often found in ground and surface water as a result of dissolution of iron-containing minerals. The concentration of iron in natural water usually ranges from 0.5 to 50 mg/L. Although iron is essential for the human body, excess iron in drinking water can cause aesthetic problems such as metallic taste, reddish color, and staining of clothing or sanitary supplies. Excess iron can also favor the growth of iron bacteria that can form slime in the water distribution system.

Iron is an essential nutrient for almost all living things, from microorganisms to humans. It is an essential part of hemoglobin, the red coloring agent of blood that transports oxygen through our bodies. However, iron deficiency or excess can cause health problems. Iron deficiency can lead to anemia, while excessive exposure to iron oxide dust or fumes can cause siderosis, a benign form of pneumoconiosis.

4. Water Treatment Applications and Removal Methods

Iron removal from water is a common practice in drinking and industrial water treatment. Some of the methods used include:

• Oxidation and Filtration: Dissolved iron is oxidized to insoluble form using oxidizers such as chlorine, potassium permanganate, or aeration, then removed through filtration.

• Ion Exchange: Cation exchange resins can remove dissolved iron, especially effective for low concentrations.

• Water Softening: The process of softening water with sodium can also remove dissolved iron.

• Reverse Osmosis: RO systems can remove most dissolved iron.

• Biological Treatment: Iron bacteria can be used to oxidize and precipitate iron in biofilter systems.

For water with high iron levels, a combination of methods is often used, such as oxidation followed by filtration and ion exchange.

5. Industrial Uses in Water Treatment

Although iron is generally considered a contaminant that needs to be removed, it also has several uses in the water treatment industry:

• Coagulants: Iron salts such as ferric chloride (FeCl₃) and ferric sulfate (Fe₂(SO₄)₃) are used as coagulants in water and wastewater treatment to remove suspended and colloidal particles.

• Phosphate Removal: Iron salts are used to precipitate phosphate in wastewater treatment, helping to prevent eutrophication of water bodies.

• Arsenic Removal: Iron hydroxide can adsorb arsenic, making it an effective method for removing arsenic from drinking water.

• Catalysts: Iron oxide is used as a catalyst in advanced oxidation processes for wastewater treatment.

6. Case Studies and Real World Application Examples

• Iron Removal in a Small Town in Indonesia

  A small town in Central Java faced a drinking water problem with high iron levels (5-7 mg/L) that caused the water to have a reddish color and metallic odor. The local government implemented a treatment system consisting of cascade aeration to oxidize the iron, followed by rapid sand filtration and chlorine disinfection. The system successfully reduced iron levels to below 0.3 mg/L, meeting national drinking water standards and improving the quality of life for residents.

• Use of Iron for Arsenic Removal in Bangladesh

  Bangladesh is facing an arsenic crisis in their groundwater. An innovative project used iron nails inserted into a sand filter to remove arsenic. The oxidized iron forms iron oxide which adsorbs arsenic effectively. This simple and inexpensive method has been implemented in thousands of households, lowering arsenic levels from over 200 ppb to below 50 ppb, the standard set by WHO.

7. Regulatory Guidelines and Standards

In Indonesia, according to the Minister of Health Regulation No. 492/MENKES/PER/IV/2010 on Drinking Water Quality Requirements, the maximum limit of iron content in drinking water is 0.3 mg/L. This standard is in line with the recommendations of the World Health Organization (WHO) which also sets a limit of 0.3 mg/L for iron in drinking water.

Meanwhile, the United States Environmental Protection Agency (US EPA) sets a secondary standard for iron at 0.3 mg/L. Secondary standards are non-mandatory guidelines that deal with aesthetic issues such as taste, odor, and color.

For industrial wastewater, iron discharge limits vary depending on the type of industry and receiving water body. In Indonesia, these limits are usually stipulated in the wastewater discharge permit (IPLC) issued by the local government.

8. Environmental Impacts and Sustainability Considerations

Although iron is a natural element and essential for life, excessive concentrations in aquatic ecosystems can cause problems. High levels of iron can:

• Lower oxygen solubility in water, affecting aquatic life.

• Cause precipitation that can damage habitats for fish and benthic organisms.

• Support the overgrowth of iron bacteria, which can disrupt the aquatic food chain.

From a sustainability perspective, iron removal from water can generate solid waste that needs to be properly managed. However, there is potential to recover and reuse iron from water treatment processes, for example as a raw material for industry or as a coagulant in wastewater treatment.

9. Future Trends and Research in Water Treatment Involving Iron

Some promising research areas and trends involving iron in water treatment include:

• Zero Valence Iron Nanoparticles (nZVI): The use of nZVI for remediation of groundwater contaminated by organic contaminants and heavy metals is being intensively researched.

• Iron-Based Membranes: Development of filtration membranes modified with iron oxide for enhanced removal of contaminants such as arsenic and phosphate.

• Iron-Based Photocatalysts: Research on the use of iron oxide as a photocatalyst for the degradation of organic pollutants in water using solar energy.

• Bioremediation with Iron Bacteria: Utilization of iron-oxidizing bacteria for wastewater treatment and environmental remediation.

• Hybrid Systems: Development of treatment systems that combine iron-based processes with other technologies such as activated carbon adsorption or advanced oxidation.

10. Interesting Facts Related to Water Treatment

• Tap water that is red or brown in color is often caused by dissolved iron, not harmful impurities or contaminants.

• Some microorganisms, known as "iron bacteria", can oxidize iron as their energy source, aiding in the natural iron removal process in nature.

• Iron is one of the most common elements that cause "hard water" along with calcium and magnesium.

• Although iron can cause aesthetic problems in drinking water, there is no strong evidence that iron in drinking water causes adverse health effects in humans.

• Traditional methods of removing iron from water involved the use of charcoal and sand, techniques that are still used in some modern household filters.