Bacteria and related endotoxins in high purity water can be serious issues to confront for those in the field of hemodialysis, laboratory, food and beverage, pharmaceuticals, water for injection (WFI) and other high purity water related applications. These impurities can directly interfere with patient health, microbiological and molecular biological applications, contamination of manufactured chemicals and medications, food and beverage consumable processing, testing integrity, and all sorts of critical applications where high purity water is required and essential.

After organic and inorganic chemical impurities are removed from some forms of pre-treatment, bacterial growth can readily occur. Remaining impurities in the form of destroyed or mutilated bacteria in the water can act as sources of nutrients for bacteria and biofilms.  The previous applications attempt to irradiate a system of a bacterial concern can reproduce more bacteria if proper water treatment methods are not properly integrated.  The bacteria themselves are not the only problem; they also produce endotoxins.  These endotoxins, also known as lipopolysaccharides (LPS), are part of the outer membrane of the cell wall of gram-negative bacteria which are released during cell metabolism, and when cells die.   Gram-negative bacteria containing these endotoxins include Escherichia coli, Salmonella, Shigella, Pseudomonas, Neisseria, Haemophilus influenza, Bordetella pertussis, and Vibrio cholera.  These endotoxins, also known as pyrogens, are powerful immune catalysts, raising body temperature if they are injected into the bloodstream.  Septic shock is possible or many other medical implications potentially up to death are possible with extreme exposure.  Such as in the case of hemodialysis an already greatly compromised system can be overcome by exposure therefore high regulations are formulated and enforced by AAMI and CMS.  They also cause serious interference in many laboratory techniques where water or prepared reagents will come into contact with DNA or RNA and can be affected by nucleases in the water therefore destroying testing results.

Water Purification technologies both alone and in series, remove or degrade bacteria and their by-products.

Ion Exchange / Service Deionization Tanks

Service Deionization Tanks also known as SDI or DI tanks containing ion exchange resins in general inactivate bacteria but should only be used when sized appropriately, monitored properly, and when regular use is expected.    Service deionization tanks should also be flushed prior to placing them in service on a compliant flush stand and never should be stored as a back-up system on site where properly flushing prior to installation is unlikely.  If used, the resins need to be replaced once they start to saturate, to avoid a point of re-releasing these contaminants into the water.   Exhausted tanks where capacity is reached can actually be a detriment to a system and negate any previous service they provided. Use in dialysis has dropped off over the years as a primary system component and is more likely to be used as an emergency back up system only due to the increasing requirements to lower endotoxin  and bacteria levels.  The SDI/DI tanks for this application must be strictly monitored and processing by the supplier must meet stringent handing processes. Tanks should be flushed prior to service and therefore not left on a customers site in standby mode.  See other trends in hemodialysis by clicking here.

Reverse Osmosis

Reverse Osmosis is very effective, again if operated and sized properly, in removing many harmful cysts and bacterial contamination.  An RO can be critical to a system’s overall success when properly maintained.   These must be used in conjunction with proper post filtration and other system components based on the system needs and final user requirements.


Micro-filters and ultra-micro-filters, with cut-offs of 0.2 and 0.05µm respectively, are excellent for removing micro-organisms, but less effective at removing endotoxins.  Only positively charged filters or ultra-filters are highly efficient at removing endotoxins.

UV Lights- Ultra-Violet Lights

Exposure to ultraviolet light is also very effective at destroying micro-organisms not killing them but making them ineffective and causing them to be unable to replicate and form colonies at 254 NM.   Because of the possibility of some bacteria leaching from deionization tanks, a 254 NM UV should be used after the tanks.  Proper sizing of the UV light for flow rates is important.  Oversizing can be as be of a problem as under-sizing.  When oversized, a UV light can heat the water and decrease contact with the bacteria and encourage growth in the bacteria not inactivated.

Relatively low doses of ultraviolet light with a wavelength of 185nm also oxidizes endotoxins and other large molecules such as Rnase and Dnase, which are particularly troublesome to remove from water for molecular biological applications. Autoclaving inactivates DNase but not RNase, and while chemical treatment with DePc will remove both, it is toxic, expensive and time-consuming, while generating ionic and organic contamination. However, the combination of photo-oxidation with 185nm UV light followed by an ultra-filter removes enzymes as well as endotoxins and bacteria.  If using deionization tanks an 185NM should be placed prior to deionization tanks to lower the conductivity of the water.  Use of an 185NM UV light increases the waters conductivity some and should be polished back up by a deionization system when ultrapure water is needed.

UV lights can be misapplied or improperly followed by poorly selected and sized final filtration.  Use of a UV light only can actually leach off pyrogens, promote further bacterial issues, and create an endotoxin rich environment.

Loop Recirculation and Storage

Static water and stored water degrades and is susceptible to bacterial growth. Recirculation of the water disrupts the establishment of colonies and biofilm and enables repeat exposure to UV light and/or passage through a filter to ensure that the background level of organisms is minimized.   The smaller the storage tank the better, and spray balls or bars should be used with proper flow through the system with limited dead legs.  See our blog on system design.


To maintain long-term bacterial integrity it is important to periodically sanitize the water purification system. The most common approach is to use an oxidant such as chlorine or peracetic acid. There are other methods that have a high kill rate when properly applied such as the use of ozone and heat sanitization.  For dialysis applications, Heat Sanitization and Ozone use are approved FDA 510 Methods. The sizing of your system will be a large part of what dictates which method is the most effective application to destroy bacteria and eliminate an endotoxin concern.

Absolute Water Technologies is here to service you and help eradicate any endotoxin or bacterial concerns.    Contact us at 1-866-986-6860 866-986-6860

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