Reverse Osmosis Water Treatment: The Science Behind Pure Water

RO Reverse Osmosis Water Treatment: The Science Behind Pure Water

1. The Physics of Nanoscale Filtration

When pure water and saltwater are separated by a semi-permeable membrane, water naturally flows toward the saltwater side (osmosis). Reverse osmosis (RO) reverses this flow by applying pressure greater than osmotic pressure to the saltwater side, forcing pure water molecules through the membrane while blocking contaminants. The heart of RO systems—the RO membrane—has 0.0001-micron pores (1/1,000,000 of a human hair), filtering ions and particles larger than 0.3–0.6 nanometers.

2. Dual Applications: Medical & Household

Medical Ultra-Pure Water
For dialysis and lab use, RO alone is insufficient. Two-stage RO + EDI (Electrodeionization) achieves 18.2 MΩ·cm resistivity. EDI combines ion exchange and electric fields to remove ions without chemicals, enabling continuous ultra-pure water production.

Household RO Systems
Typical 5-stage filtration:

• PP Sediment Filter: Traps rust/sand.

• Carbon Filter: Adsorbs chlorine/organics (*critical: >0.1mg/L chlorine damages RO membranes*).

• RO Membrane: Removes heavy metals, viruses.

• Post-Carbon Filter: Improves taste.
  Optional: Scale inhibitor to prevent mineral buildup.

3. The Mineral Debate: Facts vs. Myths

Claims that RO water "lacks essential minerals" ignore science:

• Mineral Contribution: Water provides ≤5% of daily calcium/magnesium (primary sources: food).

• Maldives Case: 100% RO-desalinated water; WHO data shows 76.8-year avg. lifespan & zero malnutrition links.

• Tsinghua Univ. Study: 200ml milk = calcium in 2,760L RO water.

Solution: Add mineral cartridges or choose micro-filtered water (TDS 50–100 mg/L) for infants.

4. Key Purchase & Maintenance Metrics

• Flow Rate (GPD): 400–600 GPD suits families of 3–4. Low flow (<100 GPD) requires storage tanks (bacteria risk).

• Wastewater Ratio: New standards mandate ≥55% efficiency (≤1.8L wastewater per 1L pure water). Advanced models: 3:1.

• Cost Alert: Beware "lifetime filters." RO membranes last 2–3 years. Annual cost = (RO membrane price ÷ 2) + (pre-filter price × yearly replacements).
  
  Critical Maintenance:

  • Flush 30 mins at first use.

  • Drain system after long idle periods.

  • Add a booster pump if water pressure <0.1 MPa.

  
  

5. RO vs. Ultrafiltration: Technical Comparison