High purity water is an essential component of many applications that make modern life possible. Its most obvious use is in the medical, food processing and biopharmaceutical industries. But it is critical to cosmetics, electronics manufacturing and metal plating, among dozens of other industries and processes. You can even find it on the grocery store shelves in jugs labeled “deionized water.” Yet despite this ubiquity, high purity water is largely overlooked – until something goes wrong with the system.
As the term “High Purity Water” suggests, this is water where all the other chemicals and minerals occurring in normal tap water have been removed. There are two primary methods to achieve this. One method uses a bed of resin beads that swap ions in the water for hydrogen (H) and hydroxyl (OH) ions. The other is reverse osmosis, where the water is forced through a semi-permeable membrane. Regardless of the process, any sodium, calcium, chlorides, sulfates, phosphates and any other ionic impurities within the water are removed. The result is water that is almost solely composed of a two-to-one ratio of hydrogen to oxygen molecules without anything else that could affect taste, scent, chemical reactions or otherwise negatively affect the final product. In fact, bottled drinking water that has been deionized has to have minerals added back into it both for health and flavoring reasons.
For water that will be used in medical or biopharmaceutical applications, such as water for injection (WFI), eye irrigation, or inhalation, reverse osmosis or distillation are the only two acceptable methods. In some cases, an extra ultra-filtration (UF) step is included as well.
Naturally, not all products require the same level of stringent purification. Regardless of the industry, the systems that generate the highly purified water will need to be cleaned regularly to ensure the continued quality of the water.
Different Systems, Different Cleaning Regimens
The range of systems and components involved in producing or using high purity water is quite varied. WFI (water for injection) stills, reverse osmosis systems and RO-DI (reverse osmosis-deionized water) systems create the high and ultra-pure water required for specific uses. The purified water is then transported through the system by the distribution piping loop to where it is needed. Depending on the system, the water will eventually be used in everything from bioreactors, process vessels to lyophilizers, sterilizers, and autoclaves. Or, it might get stored in the CIP (Clean In Place) tanks and then used to flush out the systems between product cycles. Essentially, any stainless steel surface that comes into contact with a product will need to be cleaned with high purity water. Additionally, some cleaning regimens can also include stainless steel surfaces and platforms on the system’s exterior.
Clean steam systems offer their own challenges and share similarities with liquid-water systems. They use high purity water produced by the various methods mentioned above. The steam is generated in a dedicated 316L stainless steel boiler and sent through stainless piping to where it is needed. An even more stringent level is Pure Steam, which uses the same ultra-pure water as generated for WFI applications.
As can be seen, the way high purity water is generated and distributed is as different as the industries using the water. Therefore, it is not a surprise that cleaning challenges and methods would differ greatly as well.
Broadly speaking, eight different processes are used to clean high purity water systems. Different combinations of two or more of these processes are used based on the system being cleaned.
Mechanical Polishing, Electropolishing and Electrolytic Cleaning –
Surface damage such as corrosion – better known as rouge – it can be removed with a combination of electricity and an electrolytic bath. Any remaining corrosion is removed with power tools, then the surface is smoothed using a combination of electricity and chemicals.
Derouge, Clean and Passivate (DCP)
– Removes rouge and/or staining using aqueous circulation or gel. This is followed by passivation to create the corrosion-resistant passive layer.
BioClean and Sanitization
– Removes biofilm and bioburden which is within the system and equipment.
External Derouge Clean & Passivate
– Gel applied and agitated on exterior surfaces.
Intensified Derouge Process
– Specifically designed to remove Type 3 magnetite rouge.
– Removes mineral deposits to restore efficiency.
Mechanical Chemical Cleaning
– Combination of power tools and gel to remove residue, rouge and/or staining.
DCP/Mechanical Polishing and Electropolishing/Electrolytic Cleaning –
Performed on accessories and specific components of a larger system.
Why Do It?
Performing these services aims to remove or mitigate corrosion and contamination within the system that can damage the equipment and ruin the product. In some cases, improving efficiency is an additional objective. In the case of a newly constructed system or after modification or repairs of an existing system, these services are performed because the stainless steel surfaces have been altered and are no longer resistant to corrosion until they have been treated. Some treatments also reduce surface roughness, making systems easier to clean.
Additionally, certain components are processed using different procedures to address their specific function, construction or other factors. But ultimately, these can be all viewed as essential preventative maintenance, which when performed regularly, can reduce the risk of expensive failures, product loss and unexpected downtime.