Water treatment for hydrogen production

Ultrapure water - Stable electrolyzer

The core concept of Power-to-X is to convert renewable energy via electrolysis into hydrogen. Ultrapure water is a key component for producing high quality hydrogen and maintain the function of the electrolyzer. Inadequate water treatment can jeopardize the operation and damage the electrolyzer. The choice of electrolyzer technology and water source determines the required water treatment. We secure your solution with know-how, standard products and international service - from water source to the heart of the electrolyzer.   

Asset management

Choosing the right water treatment protects the electrolyzer by preventing clogging and deactivation of membranes.



Extensive process knowledge within water treatment for electrolysis technologies since 2016.


Standard units

In-house process knowledge and production of standard units providing solutions from drinking water to ultrapure water. 



International service organization with on-call service in more than 15 countries in Europe.


Download more information

All you need to know about water for green hydrogen production - and regardless if you want a deep dive into the subject or just an appetizer, we have you covered. 

White paper exploring what happens with the water inside the electrolyzer and the implications for water treatment.


White paper by EUROWATER on water treatment for refinement loop in hydrogen production

White paper on what you need to know about water treatment for green hydrogen.


White paper by EUROWATER on water treatment for hydrogen production

Basics on water treatment for green hydrogen including useful rules of thumb.


Mini leaflet from EUROWATER on water treatment for hydrogen production

We cover all electrolyzer technologies

We can assist you with correct water treatment regardless of electrolyzer technology you use:

  • Alkaline water electrolysis (AWE)
  • Polymer electrolyte membrane electrolysis (PEM)
  • ​Internal polishing in connection to PEM
  • Solid Oxide Electrolyzers (SOEC) 
  • Anion exchange membrane electrolysis (AEM)

Our standard units cover all water treatment steps from raw water to ultrapure water. 

Reference projects

Demineralisation system for hydrogen production

PEM Electrolysis | 5 MW


Water source: City water without chlorine
Plant capacity: 1200 L/h
Conductivity: < 0.2 μS/cm
Commissioning: 2022

System components: 

  • Softening unit type SM62 
  • Reverse osmosis type RO B1-3
  • Membrane degassing unit type MDU
  • 2 x Mixed-bed type EUREX 61

Alkaline Electrolysis | 20 MW

HySynergy // Everfuel

Water source: City water without chlorine
Plant capacity: 4,500 L/h
Conductivity: < 5 μS/cm
Commissioning: 2022

System components: 

  • Softening unit type SMH 602-F
  • Brine tank 
  • Double-pass reverse osmosis type DPRO C3-6/3
  • Dosing tank with mixer
  • Dosing pump
  • Feed water tank 2 x 5000L
  • Booster pump

PEM Electrolysis | 50 MW

European Energy // Siemens Energy

Water source: Groundwater
Plant capacity: 10000 L/h
Conductivity: < 0.1 μS/cm.
Commissioning: 2023

System components: 

  • Antiscalant dosing
  • Double-pass reverse osmosis type DPRO C3-9
  • Membrane degassing unit
  • Mechanical filtration unit type EF5
  • EDI unit
  • Polisher mixed-bed type Eurex-H-901

Water source for green hydrogen production

Depending on your location and size of project you may have different water sources available and each will come with different requirements for your water treatment system. We help you choose the right water treatment solution based on your raw water and electrolyzer technology.


Stable water source, but contains iron, manganese and ammonium.


City water

Easy access for smaller projects, but contains chlorine and chloramine. 


Treated waste water

Variation in quality and potentially high load of organics.


Sea water

High salinity and content of metal ions.


How much water do you need?

Ultrapure water is the central feedstock for production of green hydrogen. Furthermore cooling water may be required in the process and system. 

But how much water does it take to produce green hydrogen? In the table we give you a rule of thumb.



9 L ultrapure water per kg H2


1 Nm3/h H2 = 1 L/h ultrapure water


1 MW electrolyser = 200 L/h ultrapure water


1 MW electrolyser = 400 L/h cooling water*


*Cooled using standard evaporative cooling tower


Water treatment units

We offer a broad selection of standard units - from groundwater treatment to polishing of ultrapure water. All units are supplied with documentation and instructions. 

FAQ - water treatment and hydrogen production

The amount varies depending on the efficiency of your electrolyser, but a good rule of thumb is around 200 L/h per MW electrolysis capacity. This does not include water for cooling.

Water contains two atoms of hydrogen and one oxygen atom. Because oxygen is 16 times heavier than hydrogen, it takes up most of the mass in a water molecule. 89% of the mass is oxygen and 11% is hydrogen. This means that to produce 1 kg of hydrogen, 9 kg of water are required. In reality, 10-13 kg of water are required due to losses and inefficiencies.

The quality depends on the type of electrolysis equipment you use, alkaline or PEM, and from which manufacturer the equipment is supplied. From a conductivity perspective, values can vary from 0.056-5 µS/cm, but many constituents affect the electrolysis process depending on the specific technology used.

ASTM Type I, II, II and IV are a set of international standards for water quality often used to describe water quality requirements for electrolysers. They cover conductivity/resistivity, sodium, chloride, TOC and silica, but in reality, they are often insufficient to properly describe the water quality needs for electrolysers.  

Both PEM and alkaline electrolysis requires make-up water treatment. PEM also requires continuous polishing of the water once it has entered the electrolysis cell. 

Whether to use EDI or mixed bed depends on whether you need it for make-up water polishing or internal polishing. Also, EDI tends to have higher CAPEX, but allows you to avoid regeneration of spent resins.

The choice of resin is very important to ensure a stable electrolysis process. Use of the wrong type of resin can lead to irreversible damage to your electrolysis stack.

Yes. Each source of water requires special attention to specific constituents in the water and you need to take variations in the inlet water quality into account. In general, we can say that wastewater requires special attention to nutrients and microorganisms that can cause biofouling, as well as the load of organics, while seawater requires focus on high retention of ions. 

The lifetime stated by electrolyser manufacturers is completely dependent on compliance with water quality requirements. Even small amounts of unwanted ions and molecules in the water can cause irreversible damage to the electrolysers. 

Typically, we need first to bring the raw water to a state similar to drinking water quality. From here the water most be conditioned to avoid scaling, after which a RO process is used to remove the bulk of the ions, organics, and colloids. A targeted process is also required to remove dissolved gasses. Finally, a polishing step can be implemented depending on the specific needs of the electrolyser.

Our equipment covers the range from small 1-10 MW installations to large scale GW installations.

Can we help you?

Our team of specialists are ready to answer your questions about pure water treatment for hydrogen production.
Contact your local sales team today.