What minerals remain in solar desalinated water?

Solar desalinated water contains trace amounts of essential minerals after the reverse osmosis process, typically retaining about 5-10% of the original mineral content from seawater. This includes small amounts of calcium, magnesium, sodium, and potassium that pass through the membrane, creating water that meets WHO drinking water standards while maintaining a pleasant taste. The exact mineral composition depends on factors like membrane type, operating pressure, and source water characteristics.

Understanding mineral content in solar desalinated water #

When seawater passes through a solar desalination system, the reverse osmosis process removes most dissolved salts and minerals, but not all of them. This partial retention is actually beneficial, as complete mineral removal would create water that tastes flat and could be corrosive to pipes. Modern solar desalination systems are designed to balance safety requirements with the need for minerals that contribute to taste and health benefits.

The goal isn’t to strip water completely bare of minerals. Instead, these systems aim to reduce mineral content to safe, drinkable levels while maintaining enough minerals to make the water palatable and stable. Think of it like filtering coffee – you want to remove the grounds but keep the flavour compounds that make it enjoyable.

Solar desalination systems typically produce water with a total dissolved solids (TDS) level between 50-500 mg/L, well within the WHO recommended range for drinking water. This means the water is neither too salty nor completely demineralised, striking a balance that works for both taste and health.

Which specific minerals remain after solar desalination? #

After solar desalination, several key minerals remain in the water at specific concentrations. Calcium typically remains at levels between 10-30 mg/L, contributing to water hardness and bone health. Magnesium follows at 5-10 mg/L, important for muscle function and energy production. Sodium levels usually range from 20-50 mg/L, significantly reduced from seawater’s 10,000+ mg/L but still present for taste and electrolyte balance.

Potassium appears in smaller quantities, typically 2-5 mg/L, while trace elements like chloride and sulphate may also be present in minimal amounts. These levels are well below WHO maximum guidelines, which allow up to 200 mg/L for sodium and have no upper limits for calcium and magnesium in drinking water.

The reason these specific minerals pass through the membrane relates to their ionic size and charge. Reverse osmosis membranes have pores small enough to block most dissolved salts, but some smaller ions and those with specific charges can slip through. This selective permeability is what gives desalinated water its characteristic mineral profile – much lower than seawater but not completely mineral-free.

How does the solar desalination process affect mineral levels? #

Reverse osmosis membranes in solar desalination systems work by forcing water through semi-permeable barriers with pores measuring just 0.0001 microns. This process removes 95-99% of dissolved salts, but the exact removal rate depends on several factors including membrane quality, operating pressure, and water temperature.

Solar power introduces an interesting variable to mineral removal rates. During peak sunlight hours, the system operates at optimal pressure, achieving maximum salt rejection. As sunlight varies throughout the day, the pressure may fluctuate slightly, potentially affecting mineral passage rates. However, modern systems include pressure regulators and energy storage to maintain consistent performance.

The membrane’s salt rejection rate also depends on the specific minerals involved. Larger, multivalent ions like calcium and magnesium are rejected more effectively than smaller, monovalent ions like sodium and potassium. Temperature plays a role too – warmer water allows slightly more mineral passage, which is why systems in tropical locations might produce water with marginally higher mineral content than those in cooler climates.

Do you need to add minerals back to desalinated water? #

Whether you need to remineralise desalinated water depends entirely on its intended use. For drinking water in resorts and villas, adding minerals back can improve taste and prevent pipe corrosion. The slightly acidic nature of demineralised water can corrode metal pipes over time, so adding calcium carbonate helps stabilise the pH and protect infrastructure.

Natural remineralisation methods include passing water through limestone beds or coral sand, which gradually dissolves calcium and magnesium into the water. This approach works well for smaller systems and avoids the need for chemical dosing. For larger operations, controlled addition of mineral salts provides more precise control over final water quality.

Different applications have varying mineral requirements:

• Drinking water: Benefits from 60-120 mg/L TDS for taste
• Irrigation: Can use lower mineral content, though some crops benefit from specific minerals
• Industrial processes: Often require very low mineral content to prevent scaling
• Swimming pools: Need balanced minerals to prevent equipment corrosion

What makes solar desalinated water safe and healthy to drink? #

Solar desalinated water meets WHO drinking water guidelines through a combination of effective filtration and natural processes. The reverse osmosis process removes not just excess minerals but also bacteria, viruses, and other contaminants, producing water with exceptional purity. The remaining mineral content falls well within safe ranges, typically showing TDS levels between 50-500 mg/L against WHO’s acceptable maximum of 1000 mg/L.

pH balance is another crucial factor in water safety. Solar desalinated water typically has a pH between 6.5-8.5, meeting WHO standards for drinking water. This slightly alkaline range prevents corrosion in distribution systems and maintains compatibility with human physiology. The absence of chemical treatment in modern solar desalination systems means no chlorine taste or potentially harmful byproducts.

What makes solar desalination particularly appealing for resorts and private properties is the chemical-free operation. Unlike traditional water treatment that relies on chlorine and other chemicals, solar desalination uses only physical filtration and solar energy. This approach eliminates concerns about chemical storage, handling, and potential health impacts while producing consistently safe water.

We’ve developed systems that maintain these quality standards without any chemical dosing, making them ideal for properties prioritising both safety and environmental responsibility. Our Elemental Water Source enables full energy independence by producing fresh water using only renewable energy in remote areas. For properties with existing power infrastructure, our Efficient Desalination system minimizes energy consumption while delivering reliable freshwater for sites with an existing power supply.