Calcium

Calcium (Ca)

1. Basic Information

2. Physical and Chemical Properties

Calcium is a soft, silvery-white metal. It is highly reactive and quickly forms oxide and nitride layers when exposed to air. Calcium dissolves in water and produces calcium ions (Ca2+). In compound form, calcium is very abundant in nature as calcium carbonate (CaCO3) in limestone and marble.

3. Presence in Water and Health Effects

Calcium is a common mineral found in natural water. Its presence mainly comes from the dissolution of calcium-containing rocks and minerals such as limestone, dolomite, and gypsum. Water with high calcium content is referred to as hard water.

Calcium is important for human health, especially for the formation of bones and teeth. However, water that is too hard can cause problems such as:

• Scale buildup on appliances and pipes

• Reduced effectiveness of soaps and detergents

• Poor water taste

• Stains on clothes and appliances

Nonetheless, calcium in drinking water is generally not harmful to health and may even contribute to the daily calcium intake required by the body.

4. Water Treatment Applications and Removal Methods

Some commonly used methods to remove or reduce calcium in water include:

• Softening by Ion Exchange: Uses ion exchange resin to replace calcium ions with sodium ions.

• Reverse Osmosis (RO): RO membranes can remove most dissolved minerals including calcium.

• Nanofiltration: A more selective membrane than RO, effective for removing divalent ions such as calcium.

• Chemical Precipitation: Adding chemicals such as lime or soda ash to precipitate calcium.

• Distillation: A process of evaporation and condensation that removes almost all dissolved minerals.

• Magnet or Electronic Softening: Alternative methods that change the crystallization properties of calcium without removing it from the water.

5. Industrial Uses in Water Treatment

Although calcium is often removed in water treatment processes, calcium compounds also have some important applications in the water treatment industry:

• Calcium hydroxide (Ca(OH)2) or lime is used to adjust the pH and alkalinity of water.

• Calcium hypochlorite (Ca(ClO)2) is a commonly used disinfectant in drinking water and swimming pool treatment.

• Calcium carbonate (CaCO3) is used as a filter media in water treatment and to remineralize desalinated water.

6. Case Studies and Real World Application Examples

• Example 1: Water Treatment in Bandung City Bandung City is facing hard water problems from groundwater sources. PDAM Tirtawening implemented a water softening system using large-scale ion exchange. As a result, the quality of the distributed water improved significantly, reducing customer complaints related to scale and efficiency in soap usage.
• Example 2: Soft Drink Factory in Surabaya A soft drink factory in Surabaya uses reverse osmosis and nanofiltration systems to remove calcium and other minerals from their raw water. This is important to maintain product flavor consistency and prevent settling in bottles during storage.

7. Regulatory Guidelines and Standards

In Indonesia, based on Minister of Health Regulation No. 492/MENKES/PER/IV/2010 on Drinking Water Quality Requirements, there is no specific limit for calcium. However, there are related parameters:

• Total Dissolved Solids (TDS): maximum 500 mg/L

• Hardness (CaCO3): maximum 500 mg/L

The World Health Organization (WHO) does not set a guideline value for calcium in drinking water as there is no evidence of significant health hazards.

8. Environmental Impact and Sustainability Considerations

Calcium removal from water has several environmental implications:

• The use of salt in ion exchange softening can increase the salinity of wastewater.

• RO and nanofiltration processes require significant energy.

• Concentrate discharge from membrane processes can be an environmental issue if not handled properly.

To improve sustainability, several approaches can be taken:

• Use of energy-efficient technologies in the desalination process.

• Recycling of wastewater from the softening process.

• Development of more environmentally friendly softening methods.

9. Future Trends and Research

Some of the research and development areas related to calcium in water treatment include:

• Development of more efficient calcium-selective membranes.

• More effective chemical-free softening technologies.

• Utilization of calcium removed from water for other beneficial applications.

• Integration of smart water treatment systems that can adjust calcium removal rates based on real-time needs.

10. Interesting Facts Related to Water Treatment

• Natural rainwater is slightly acidic and contains almost no calcium, but can become hard after passing through soil and rocks.

• Some studies show that drinking water containing calcium can contribute significantly to daily calcium intake, especially in areas with very hard water.

• The presence of calcium in water can affect the taste of tea and coffee. Water that is too soft or too hard can result in beverages that are less than optimal in taste.

• The water distribution system in some old cities still uses lead pipes. Calcium in water can help form a protective layer inside the pipes, reducing the risk of lead contamination.