What's the Difference Between Pure Water and Ultra Pure Water?

Both pure water and ultrapure water are frequently used in industrial production. Although they differ by only one character, they have distinct water quality requirements, preparation processes, and applications. Ultrapure water is typically used in industries with extremely high water quality demands, such as semiconductors, pharmaceuticals, and photovoltaics, whereas pure water has lower purity requirements and is commonly used in industrial production and laboratories. We have listed the detailed differences between ultrapure water and purified water in terms of water quality, treatment processes, and applications.

Water Quality Comparison
Water Quality	Ultrapure Water (UPW)	Purified Water
Conductivity	< 0.055 μS/cm	0.1–10 μS/cm
Resistivity	≥ 18.2 MΩ·cm	0.1 – 10 MΩ·cm
Total Organic Carbon (TOC)	< 5 ppb (some applications require < 1 ppb)	10 – 100 ppb
Microbial Content	Nearly zero	Small amounts of microbes allowed
Particles	Needs to remove submicron particles (nearly zero)	Some particles allowed, less strict requirements
Gas Content	Strictly controls gases such as CO₂, O₂	Less control over dissolved gases

Treatment Processes Comparison
Treatment Process	Ultrapure Water (UPW)	Purified Water
Pretreatment	Multimedia filtration, activated carbon, softening	Multimedia filtration, activated carbon
Core Treatment Steps	Reverse Osmosis (RO) + Electrodeionization (EDI) or mixed bed ion exchange	Reverse Osmosis (RO)
Polishing	Mixed bed ion exchange, UV oxidation, microfiltration, and ultrafiltration	Optional: simple ion exchange or UV treatment
Post-treatment/Storage	Terminal microfiltration (0.1 μm) + sterile storage	Regular water tanks and distribution systems
Online Monitoring	Real-time monitoring of conductivity, TOC, microbes	Typically no need for real-time monitoring

Applications Comparison
Application Area	Ultrapure Water (UPW)	Purified Water
Semiconductor Industry	Wafer and chip cleaning	Not applicable
Pharmaceutical Industry	Injection solutions, drug synthesis (GMP, USP compliance)	General medical use (disinfection, washing)
Photovoltaic Industry	Cleaning of photovoltaic cells	Not applicable
Nuclear Industry	Cooling water for nuclear reactors	Not applicable
Laboratories	High-precision research (e.g., molecular biology, chemistry)	General lab uses (reagent preparation, cleaning)
Industrial Production	High-precision manufacturing processes	Boiler feedwater, cooling water, food processing

Summary

Ultrapure water treatment is more complex, involving multiple filtration and polishing steps, and is used in industries with strict water purity requirements like semiconductors and pharmaceuticals.

Pure water treatment is simpler and is commonly used in less demanding applications like general industrial processes and basic laboratory use.