This website is intended for healthcare professionals only.

Hospital Healthcare Europe
Hospital Healthcare Europe

Obtaining high quality dialysis water: a step-by-step guide

Piergiorgio Bolasco, MD
24 July, 2015  

Standard haemodialysis treatment sessions last 4–6 hours. Individual patients are exposed to 15,000–20,000L of dialysis fluid per annum. In haemodiafiltration procedures, dialysis water is administered as dialysate, as opposed to infusate IV, directly to the patient. When using haemodiafiltration online with high volume exchanges, further dialysate infuses online up to 3400–6800L IV.1
The increasing tendency to use online haemodialysis procedures implies the potential presence in distribution piping of microbial, fungal and chemical substances, which should be carefully monitored, as detailed in specific guidelines.2,3
Moreover, water should be tested by certified laboratories using different analytical procedures to those applied to test human blood and secretions.4

Numerous undesirable substances originate from polluted water or infiltrations in the drinking water supply network. Humans are the major culprits, contaminating waterworks through the use of ineffective measures to reduce bacterial and/or chemical pollutant especially loads originating from surface water collected in artificial basins, or from the building of drinking water networks using obsolete or inappropriate materials. The majority of toxic contaminants derive from procedures applied in the treatment of municipal waters not always safe for direct use in haemodialysis applications.2,3

An inadequate dialysis water resulting from treatment facilities not being monitored, inefficient systems for the distribution of dialysis water to monitors and irregularity in disinfection constitute the most frequent causes of harmful or fatal substances being introduced.
Dialysis water is not an everyday medium; today it is considered drug-like because contact with blood or inadequate dialysate through a semipermeable membrane triggers many serious inflammatory and oxidative reactions, leading to an activation of harmful molecules such as interleukins and pro-oxidant toxins.4

Step-by-step procedures

Pre-treatment procedures5

At the beginning of the production cycle, a variety of filters may be utilised to remove coarse particulate matter prior to purification and to protect RO membranes from fine particles washed out of carbon beds.

Chlorination and dechlorination
The use of these techniques is not mandatory but is a further guarantee.  Good quality proportioned pumps should be applied to guarantee optimal chorine concentration (0.5–1ppm), although complete water dechlorination should be done to avoid the degradation of osmosis membranes. Fortunately, N-chloramines are relatively large molecules and are removed by RO; however, assays to detect the presence of chloramines are mandatory (Figure 1).

Softening is a commonly used auxiliary purification process, a form of deionisation that exchanges calcium and magnesium ions for sodium ions. Softeners are widely used in areas with a “hard” municipal water supply. Use of a water softeners before the reverse osmosis unit will protect RO membranes from fouling by calcium and magnesium salts.

The pollutant potential of this aspect is frequently underestimated. Tanks should be opaque, made of plastic for foodstuffs and not be located in a “stagnant” corner of the circuit, but should guarantee a constant flow of water. Reservoirs should be protected from extreme temperature excursions and be periodically emptied and disinfected.

Reverse osmosis
Today it is necessary to definitively move on from single reverse osmosis (SRO) and use twice-reverse osmosis (TRO) methodology. The osmosis membranes are made from a polyamide spiral wound around a permeate-collecting tube. This material is compatible with peracetic acid eventually plus hypochlorite disinfectant when it is preferred chemical disinfection.  But a new disinfection method adopted is provided with a fully automated system of thermal disinfection that no longer requires chemical disinfection and features an integrated system for the thermal disinfection of membranes and distribution ring. Thermal disinfection of TRO systems provides an automated daily thermal disinfection of dialysis room distribution circuits using water heated to 90–95°C, to prevent the formation of biofilms. The circulation of hot water in the dialysis room distribution circuit occurs at the end of the dialysis session and continues throughout the night until shortly before the start of the morning session when piping temperatures return to safer levels. Two-stage chemical disinfection of the distribution ring downstream of the dialysis monitors was carried out on a monthly basis: peracetic acid for two hours and a chloroxidant agent for an additional two hours followed by accurate rinsing.

Optimal water piping distribution and discharge
An optimal diameter distribution ring should be applied to avoid sluggish segments; where possible, valves should be constructed in high quality stainless steel, and pumps made from inert materials. Metals such as brass, aluminium, or galvanised metal should not be used. The distribution system must be designed as a closed ring to minimise microbiological contamination and to reduce bacterial and fungal biofilm adhesions. The use of PVC must be eliminated as well as materials such as INOX AISI 316L, PEX, PVDF, which are used to construct piping. Modern gooseneck systems should be envisaged to prevent the introduction of polluted water into monitors (Figure 1).

Figure 1: Haemodialysis water system configuration

Sampling should be carried out using a series of procedures aimed at obtaining a small aliquot of water for analysis. Bottles and vials used to collect samples should be protected against possible contamination. Water needs to be left to run long enough to eliminate disinfectants prior to sampling.

Sampling procedures
Taps of piping should be cleaned and disinfected from dust, mucilage, detergents, disinfectants and other substances capable of affecting the outcome of microbiological analysis prior to sampling. A solution of sodium hypochlorite or sodium hypochlorite or isopropyl alcohol is used. In addition to the mandatory cleansing and disinfection procedures, metal taps may also be flame gouged. On collection, the sterile bottle is opened, taking care to not touch the inside of the cap or bottle neck, which will come into direct contact with the sample and it should be closed immediately after sampling.

During transportation and storage of samples for microbiological testing, preventing regrowth of microorganisms should ensure the representative nature of samples. The sample should be stored away from the light (both ultraviolet and visible) and from high temperatures and appropriate conditions of hygiene applied during transportation.  From the time of sampling to arrival in the lab, all samples should be stored at a temperature of below 10°C, with the optimum range of 2–8°C being recommended. Samples must be inseminated within two hours.

Analytical Procedures
We opted to extend tests to a higher spectrum of microorganisms frequently detected in previous studies, particularly where the hydrogeographics are characterised by the presence of surface water collected in artificial basins according to the high temperatures registered during summer months in many countries of the world.  

Microbiological testing procedures should not only assess the presence of environmental mesophiles and mycetes, but should also address the issue of detecting specific pathogens.6,7 Samples should be obtained as far away as possible from the most recent point of disinfection by following a rotation schedule between at least three locations situated at the beginning, the centre and the end of the cycle.

Microbiological analysis
The microbiological cultures have poor nutrients to optimise study of microbiological growth at conventional environmental temperature (22°C). The main focus must be on total coliforms and enterococci also at 37°C, Pseudomonas aeruginosa, Clostridium perfringens, mycetes and their spores.

Analytical procedures undertaken to assess the number of microorganisms at 37°C and 22°C are identical for both parameters and they comprise of the agar inclusion technique for 64–72 hours. Counting at 22°C (for mesophiles) is done at 20–23°C for seven days.  

Endotoxin tests
Tests are carried out on osmotic water, as monitors are detached at random initial, intermediate and end points in the cycle. Spectrophotometric methods are used such as the Limulus amebocyte test. New tests that check bacterial DNA fragments are now available and this provides a complete evaluation panel.
Target results
Table 1. Dialysis water: optimal values3

Undesirable substances

This contaminant followed aggressive alum flocculation of water under conditions of extreme drought. Chloramines are used as a bactericidal agent in municipal water treatment. Exposure to chloramine is associated with haemolytic anaemia and methaemoglobinaemia in haemodialysis patients; other contaminants must be monitored such as fluoride, copper, zinc and lead.

These include chloroform, bromoform and dichlorobromomethane and are generally produced through the chlorination of drinking water and are potentially carcinogenic. Not least is acetate inside industry dialysate; it must be abolished as it is a pro-oxidant and pro-inflammatory agent and dangerous for cardiovascular organs.

To conclude, it is indisputable that poor quality water may be the cause of a higher number of diseases. This applies to the development of dialytic amyloidosis worsening of anaemia and in inducing an increase in cardiovascular morbidity and mortality. The concept whereby “dialysis fluid is a form of medication” should be underlined and all nephrologists involved in haemodialysis should be instructed in the maintenance and monitoring of water production systems used in their units.


  1. Locatelli F et al. Hemofiltration and hemodiafiltration reduce intradialytic hypotension in ESRD. J Am Soc Nephrol 2010;21:1798–807.
  2. Association for the Advancement of Medical Instrumentation. Guidance for the preparation and quality management of fluids for hemodialysis and related therapies. ANSI/AAMI/ISO 23500:2011 and specifically ISO 13959:2009 and ISO11663:2009.
  3. Alloatti S et al. Guidelines on water and solutions for dialysis. Italian Society of Nephrology. G Ital Nefrol 2005;22(3):246–73.
  4. Guo LL et al. Conventional, but not high-purity, dialysate-induced monocyte apoptosis is mediated by activation of PKC-delta and inflammatory factors release. Nephrol Dial Transplant 2011;26:1516–22.
  5. Bolasco P et al. The evolution of technological strategies in the prevention of dialysis water pollution: sixteen years’ experience. Blood Purif 2012;34(3–4):238–45.
  6. Guidelines for Environmental Infection Control in Health-Care Facilities. Recommendations of Practices Advisory Committee (HICPAC) CDC and the Healthcare Infection Control. U.S. Department of Health and Human Services Centers for Disease Control and Prevention (CDC) Atlanta, GA 30333; 2003.
  7. Arvanitidou M et al. Occurrence and antimicrobial resistance of Gram-negative bacteria isolated in haemodialysis water and dialysate of renal units: results of a Greek multicentre study. J Appl Microbiol 2003;95(1):180–5.
  8. Bolasco P et al. Microbiological surveillance and state of the art technological strategies for the prevention of dialysis water pollution. Int J Environ Res Public Health. 2012;9(8):2758–71.