Pure and Ultrapure Water Treatment: Water Qualities

Which Ultrapure Water Qualities are there?

Germany and Europe - Drinking Water Ordinance and European Pharmacopoeia

In Germany, the classification into different ultrapure water qualities is based on the German Drinking Water Ordinance (TrinkwV). In Europe there is the European Pharmacopoeia, according to which the ultrapure water quality levels are divided. Various parameters are included in the classification.

The European Pharmacopoeia describes the following terms:

  • AP: Aqua Purificata
    also referred to as deionized water (fully desalinated water) or PW (purified water)
  • HPW: Highly Purified Water
    Pharmaceutical water in WFI quality, but made with membrane technology
  • WFI: Water for Injection
    Defined water quality for sterilized final containers; mostly made by distillation
Parameters TrinkwV Feed Water DIN 285/58950 AP HPW WFI
Conductivity 2.790 µS/cm at 25°C <1,1 µS at 20°C <4,3µS at 20°C <1,1 µS at 20°C <1,1 µS at 20°C
Bacteria   0 <100 KBE/ml < 10 KBE/100ml < 10 KBE/100ml
Endotoxins   < 0,25 EU per ml   < 0,25 EU per ml < 0,25 EU per ml
TOC without abnormal change <500 ppb <500 ppb <500 ppb <500 ppb
Nitrate 50 mg/l   <0,2 ppm    
Heavy metals (especially Pb) 0,010 mg/l <0,1 ppm <0,1 ppm    
pH 6,5 - 9,5 5,0 – 7,0      
Silicon (SIO2) < 1 mg/l        

International - ASTM

Internationally, it is divided into different ultrapure water qualities according to the American Society for Testing on Materials (ASTM). Here, too, various parameters are included in the classification.

Parameters Typ I Typ II Typ III Typ IV
Conductivity 0,056 µS/cm 1,0 µS/cm 4,0 µS/cm 5,0 µS/cm
Electrical Resistance 18 MΩ-cm 1.0 MΩ-cm 0,25 MΩ-cm 0,2 MΩ-cm
TOC 10 ppb 50 ppb 200 ppb -
Sodium 1 ppb 5 ppb 10 ppb 50 ppb
Chloride 1 ppb 5 ppb 10 ppb 50 ppb
Silicate (Silicon) 3 ppb 3 ppb 500 ppb -
Bacterial Count (KBE) 1/100 ml 10/100 ml 1000/100 ml  
Endotoxine (EU/ml) < 0,03 < 0,25 N.A.  
Technologies Ultra Pure Water System Pure Water System Reverse-Osmosis EDI  

Pharmacopeia-Norms: EP and USP

Pharmacopeia-Norms are separate standards from the authorities in Europe, USA and Japan for different materials, e.g. water for medical use.

Parameters EP USP
Spec. Conductivity <4,3 µS/cm at 20 ºC <1,3 µS/cm at 25 ºC
TOC <500 µg/l C <500 µg/l C
Nitrates <0,2 ppm -
Germ count (guideline CFU/ml) <100 KBE/ml <100 KBE/ml
Particle Content 0,2 µm Filter -
Heavy Metals <0,1 ppm -

ISO 3696:1987

Water for analytical laboratory use, requirements and testing

Parameters Grade 1 Grade 2 Grade 3
Conductivity (µS/cm at 25 °C, max.) 0,1 1 5
pH-Value at 25 °C - - 5,0 - 7,0
Oxidizable matter, oxygen content (mg/l, max.) - 0,08 0,4
Absorbance at 254 nm and a length of 1 cm (Absorbance Units, max.) 0,001 0,01 -
Residual after evaporation when heated to 110°C (mg/kg, max) - 1 2
Silicon content (mg/l, max.) 0,01 0,02 -

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