[ water treatment ] used in the process within strict limits guarantees efficient , economical production and operational safety .
Figure 1 clearly shows that water treatment is needed at three points ( dashed rectangles ): 1 . Demi water make-up technology 2 . Demi water polishing technology ( UPW ) 3 . Circulated water polishing technology
Presentation of the water treatment technologies used
The demi water make-up technology is designed to produce desalinated water from raw water , which can be surface water , groundwater , or pre-treated wastewater . This water is suitable as feedstock water for most energy applications , e . g ., power plants and alkaline electrolysis , but further polishing is required for PEM electrolysis technology . This is the purpose of the demi water polishing technology , which ensures compliance with strict limits through further treatment of the desalinated water .
Although the two technologies can in principle be combined into one system , it is not recommended due to the risk of secondary pollution . From this point onwards , we are dealing with ultrapure water , which consists almost entirely of pure H 2
O molecules . The presence of contaminants can only be measured in ppb / ppt concentrations . Thus , the selection of component materials of the system plays a key role in maintaining water quality . Released substances from water contacting parts can cause a continuous deterioration of water quality . Metal ions and TOC content are the main concerns . For these reasons , contact between water and metal surfaces should be avoided , and TOC leaching from other materials should be minimised . The electrolysis process itself also contaminates the circulated water with ions and organic matter released from the electrode material .
The circulated water polishing technology is designed to maintain the water quality of the internal circulation circuit . This system is
Fig . 2 . A 586 m 3 / day desalinated water + ultrapure water production system manufactured and installed by Hidrofilt Water Treatment Ltd . in an electronics factory in Hungary , 2019 .
Hydrogen Tech World | Issue 15 | April 2024 41