water treatment for hemodialysis: an update

Nephrology Nursing Journal September-October 2013 Vol. 40, No. 5 383

Water Treatment for Hemodialysis: An Update

In hemodialysis (HD), more than90% of the dialysate delivered to thedialyzer is water. The more pure thewater, the more accurate the dialy -

sate prescription that is delivered, aslong as the water is properly mixedwith the correct concentrates and inthe correct proportions. Water con-tamination can lead to anemia, alter-ations in blood pressure and acid-basebalance, neurological issues, bone dis-ease, and more, and patients may suf-fer acute or chronic problems fromexposure to substandard dialysate.The potential clinical symptoms ofusing inadequately purified water orcontaminated dialysate are shown inTable 1. It is estimated that many re -actions to inadequately purified waterof go unreported because the chronicsymptoms of kidney disease mineralbone disorder or chronic inflamma-tion, can be insidious and attributed toproblems secondary to end stage renaldisease (ESRD) unless a patientexhibits an acute or sub-acute reaction.

The Food and Drug Admini -stration (FDA) regulates dialysis waterpurification systems and classifieswater systems, along with dialysismachines, as Class II medical devices(FDA, 2011). Class II devices requirediligent tracking of critical compo-nents and a complaint investigationsystem in place. Class I devicesinclude loosely regulated items, suchas tongue depressors and Band-Aids®,

Rebecca Layman-AmatoJim CurtisGlenda M. Payne

Continuing NursingEducation

Note: Authors’ biographical information can befound on the following page.

Statement of Disclosure: Jim Curtis disclosedthat his place of employment, Home Dialysis Plus,Ltd., manufactures a home dialysis system thatincludes a water treatment module.

All other authors reported no actual or potentialconflict of interest in relation to this continuingnursing education activity.

Note: Additional statements of disclosure andinstructions for CNE evaluation can be found onpage 405.

This offering for 1.7 contact hours is provided by the American Nephrology Nurses’Association (ANNA).

American Nephrology Nurses’ Association is accredited as a provider of continuing nursingeducation by the American Nurses Credentialing Center Commission on Accreditation.

ANNA is a provider approved by the California Board of Registered Nursing, provider numberCEP 00910.

This CNE article meets the Nephrology Nursing Certification Commission’s (NNCC’s) continu-ing nursing education requirements for certification and recertification.

Copyright 2013 American Nephrology Nurses’ Association

Layman-Amato, R.L., Curtis, J., & Payne, G.M. (2013). Water treatment for hemodialy-sis: An update. Nephrology Nursing Journal, 40(5), 383-404, 465.

While nurses may not routinely service the water treatment system or mix the dialysate,they are responsible for understanding all of the clinical ramifications of water treat-ment and dialysate preparation for hemodialysis as a part of the entire dialysis treat-ment picture. Although the water treatment system has historically been in the techni-cians’ domain, knowing the technical aspects is important for the entire team to worktogether to ensure patient safety and well-being. This article describes the composition ofwater treatment systems for hemodialysis, as well as the monitoring and testing neces-sary to assure that both water and dialysate are safe for patient use.

Key Words: Hemodialysis, water treatment system, dialysate preparation, patientsafety.

GoalDiscuss the technical components of the water treatment system used for dialysis.

Objectives1. List the components of the water system at your dialysis clinic.2. Describe the required monitoring of the water treatment system.3. Discuss clinical manifestations patients may experience due to exposure to improper-

ly treated water.

while Class III devices, such as high-flux hemodialyzers and implantablepace makers, are stringently regulateddevices and require tracking of allparts (even nuts and bolts) (FDA,2009).

Water SupplyThe first step to understanding

water treatment is to understand watersources. There are two sources ofwater that municipal water suppliers

use: ground water and surface water.Ground water comes from under-ground chambers, such as wells andsprings, and is generally lower inorganic materials but higher in inor-ganic ions, such as iron, calcium, mag-nesium, and sulfate. Surface watercomes from lakes, ponds, rivers, andother surface type reservoirs. Surfacewater is generally more contaminatedwith organisms and microbes, indus-trial wastes, fertilizers, pesticides, andsewage. Some municipalities rely pri-

Nephrology Nursing Journal September-October 2013 Vol. 40, No. 5384


marily on surface water most of theyear, and then blend in well waterwhen the supply of surface water falls.Dialysis facilities must be constantlyvigilant and cognizant of their watersource if the source varies over time.

Municipalities or public watersuppliers process both types of water,and depending on the quality of thesupply water, they may add chemi-cals. The Environmental ProtectionAgency (EPA) regulates all public

water systems that serve 500 or morehouseholds, and those laws requirestrict adherence to the Safe DrinkingWater Act (EPA, 2012). This law setsthe maximum allowable level of con-taminants in drinking water (potablewater).

Municipal water suppliers mayprocess waste water from sewage andindustry for drinking water. Forexample, waste from the manufactur-ing process may be metered into thewaste water drain in compliance withEPA and other regulations. The wastewater is distributed to a waste waterplant where it runs into large settlingponds and is treated with chemicalsand flocculants (agents that cause sed-iment to “clump” and settle to thebottom of the pond) to remove thecontaminants. The top layer of wateris then fed into a river or reservoirthat feeds the municipal potablewater facility. At that facility, thewater is further treated with floccu-lants, such as aluminum sulfate(alum), to remove non-filterable sus-pended particles (colloidal matter);depth filtration to remove filterablesolids; chlorination/chloraminationfor disinfection; and fluoridation(which is elective) to prevent dentalcavities. Ironically, most chemicaladditives have unenforceable con-taminant level goals; in other words,no citations are given when a desiredlevel is violated. Some, like alu-minum, are even considered nuisancechemicals and have only a secondarystandard. The maximum allowablelevels of contaminants in water as setby the Association for the Advance -ment of Medical Instrumentation(AAMI) (for dialysis water) and theEPA (for drinking water) are shown inTable 2.

The EPA requires municipalwater supply companies to monitorand test the water on a periodic basis.The quality of the water can changefrom season to season and even dayto day. Though our drinking water isgenerally safe, it has been reportedthat between 2004 and 2009, 252 mil-lion Americans were exposed to tapwater contaminants that are abovehealth guidelines (Environmental

Rebecca Layman-Amato, BSN, RN, was Corporate Marketing and Education Director, and Co-Ownerof ZyzaTech Water Systems, Inc. She was a corporate member of the Association for the Advancement ofMedical Instrumentation (AAMI) Renal Disease and Detoxification Committee and was on the Task Forcefor Water Treatment. Rebecca is a Past President of ANNA’s Greater Puget Sound Chapter and a Past Chairfor the ANNA Corporate SIG. She may be contacted directly at [email protected]

Jim Curtis, CHT, is the Director of Technical Services and Co-Founder of Home Dialysis Plus, Ltd.,Sunnyvale, CA. Jim is a Past President of the National Association of Nephrology Technicians (NANT). Heis a voting member of both the AAMI Renal Disease and Detoxification and the AAMI Medical Devices inHome Applications Committees.

Glenda M. Payne, MS, RN, CNN, is the Director of Clinical Services for Nephrology Clinical Solutions.She previously worked as a State and Federal Surveyor for 30 years, served as a primary author of the TexasESRD Licensing Rules and the Federal ESRD Interpretive Guidance, and was a member of the Core Facultyfor Surveyor Training and Tool Development from 1989-2011. Glenda has served on the Renal Disease andDetoxification (RDD) Committee of the Association for the Advancement of Medical Instrumentation(AAMI) since 2003 and is currently ANNA’s AAMI representative. Glenda is a charter member of ANNA’sDallas Chapter, and has served as Southeast Vice President, National Secretary, and President of ANNA.

Note: This article is an update of Ms. Amato’s article, “Water Treatment for Hemodialysis, Updated toInclude the Latest AAMI Standards for Dialysate (RD52:2004),” which was first published in the March-April 2005 issue of the Nephrology Nursing Journal (Volume 32, Number 6, 151-167).

Note: The reader may notice that many of the references for this article are older than normally would be used.These are classic articles that reported the results of discovery, rather than research.

Acknowledgment: We want to acknowledge the contributions of David Daniel, who contributed to the orig-inal article. David was an Applications Engineer with ZyzaTech Water Systems, Inc.; Osmonics, Inc.; GE;and Mar Cor Purification, Inc. He passed away on August 22, 2012.

Table 1Signs and Symptoms and Possible Water

Contaminant-Related Causes

Symptom Possible Water Contaminants

Anemia Aluminum, chloramine, copper, zinc

Bone disease Aluminum, fluoride

Hemolysis Copper, nitrates, chloramine

Hypertension Calcium, sodium

Hypotension Bacteria, endotoxin, nitrates

Metabolic acidosis low pH, sulfates

Neurological deterioration Aluminum

Nausea and vomiting Bacteria, calcium, copper, endotoxin, low pH,magnesium, nitrates, sulfates, zinc, Microcystins (from blue-green algae)

Death Aluminum, fluoride, endotoxin, bacteria, chloramine,microcyctins

Visual disturbances Microcystins

Liver failure Microcystins

Note: Revised from FDA (1989).


Working Group, 2009). This placesan extra burden on nephrology pro-fessionals working to deliver thepurest water feasible to persons onHD.

Acute dialysis programs shouldascertain whether the medical centerwhere dialysis occurs adds furtherchemicals to the water for hospitaluse. Some hospitals have mini watertreatment plants and may add disin-fectants, such as chlorine dioxide ordescalers, to the water. The hospitalshould give advance warning of any

chemical process affecting the watersupply to the dialysis professionals.

Why Water Purity Is ImportantDuring Hemodialysis

By the time water arrives at ourfaucets, it is deemed acceptable todrink by the municipality and EPA;however, drinking water is notacceptable for use in HD treatments.The average person consumes ap -proximately two liters of water a dayin different forms (juice, coffee, etc.),

whereas a patient on HD is exposedto 90 to 192 liters of water per treat-ment. In healthy individuals, the con-taminants in water are mainly excret-ed through the kidneys and gastroin-testinal (GI) system. Patients on HDdo not have functioning kidneys toexcrete the waste products. They relyon HD to remove the wastes and nor-malize the electrolytes, and to notpotentially add a life-threatening con-taminant from the massive water (asdialysate) exposure. While peopletypically filter everything throughtheir kidneys and liver, those on HDhave dialysate exposure filtered viathe dialyzer’s semi-permeable mem-brane. That membrane is only selec-tive with respect to molecular size andis not contaminant-specific. Contami -nants in the water can diffuse fromthe dialysate into the blood, depend-ent upon the level within the bloodand the thresholds for that contami-nant.

This article reviews technicalinformation on feed water compo-nents, pretreatment components, re -verse osmosis (RO) systems, post-treatment components, distributionsystems, alternative disinfection meth-ods, bacteria and endotoxins, andbacteriology of dialysate. Typically,not all components mentioned arepart of a water treatment system forHD. Components will vary fromfacility to facility depending upon theincoming water quality and philoso-phy of the staff or organization.

Organizing the System The AAMI standards provide

recommendations that the FDA andCenters for Medicare & MedicaidServices (CMS) have embraced. Theyrequire that the labels for all watertreatment devices must include:(AAMI, 2009a; CMS, 2008b). • The type of device, how it func-

tions, and what to monitor.• The manufacturer name and

address with phone number.• Model and serial number.• Appropriate warnings for use.• Identification of methods to pre-

vent improper connections.

Table 2 AAMI and EPA Maximum Allowable Levels of Contaminants in Water

Contaminant

EPA Maximum for DrinkingWater (mg/L)

(Condensed List)July 2002

AAMI MaximumConcentration

for HemodialysisWater

(mg/L UnlessOtherwise Noted)

ConcentrationAssociated

withHemodialysis

Toxicity (mg/L)

Calcium Not regulated 2 (0.1 mEq/L) 88.00

Magnesium Not regulated 4 (0.3 mEq/L)

Potassium Not regulated 8 (0.2 mEq/L)

Sodium Not regulated 70 (3.0 mEq/L) 300.00

Antimony 0.006 0.0060

Arsenic 0.005 0.0500

Barium 2.000 0.1000

Beryllium 0.004 0.0004

Cadmium 0.005 0.0010

Chromium 0.100 0.0140

Lead 0.015** 0.0050

Mercury 0.002 0.0002

Selenium 0.050 0.0900

Silver 0.100 0.0050

Aluminum 0.05 to 0.2* 0.0100 0.06

Chloramines 4.000* 0.1000 0.25

Free Chlorine 4.000* 0.5000

Copper 1.300** 0.1000 0.49

Fluoride 2.0* to 4.0 0.2000 1.00

Nitrate (as Nitrogen) 10.000 2.0000 21.00

Sulfate 250.000* 100.0000 200.00

Thallium 0.002 0.0020

Zinc 5.000* 0.1000 0.20

*Unenforceable maximum contaminant level goal (secondary standard).**Action level at 90th percentile.



• Prominent warnings if the com-ponent contains germicides.Flow schematics and diagrams

should be displayed in the water treat-ment room and updated as necessary.Having directional arrows on the pip-ing and clearly labeling valves willhelp keep things organized. CMSrequires the operator to know theparameters of the different compo-nents. Listing these on the water treat-ment log sheet will facilitate thisprocess and serve as a ready refer-ence. Some parameters vary fromfacility to facility, and should be setbased on the facility’s unique situationand upon manufacturers’ recommen-dations. Parameters that may vary indifferent systems include items suchas pressure readings, flow readings,and conductivity measurements invarious locations of the system.

Contingency PlanA dialysis facility must develop a

contingency plan as to what to do if theelectrical or water supply to the facilityis lost or if there is a failure of a criticalcomponent of the system (e.g., carbon

tank, RO system, or circulationpump). The plan should also addresssudden changes in incoming waterquality (AAMI, 2011; CMS, 2008b).

Water Treatment SystemThe components of a water treat-

ment system are discussed in theorder that they are most likely to beplaced in a dialysis water treatmentsystem (see Figure 1). (Note: Whenthe word “shall” appears, it is takenfrom the AAMI standards in which“shall” means “must.”

Feed Water ComponentsBack-flow preventer. All water

treatment systems, including watersystems for acute dialysis, require aform of back-flow prevention. Aback-flow preventer prevents thewater in the water treatment compo-nents from flowing back into themunicipality’s potable water lines.This protects drinking water fromcontamination with disinfectants andcleaners that are used in dialysis watertreatment systems. Many otherdevices connected to the drinking

water supply, such as large air condi-tioning units, require back-flow pre-vention to inhibit back-siphoning ofpotential contaminates, such asantifreeze and other toxins, into thepotable water system.

Local codes dictate the type ofback-flow preventer that can be used,and these vary from area to area.Some areas may require a break tankfor water treatment systems used foracute dialysis. These use an air gap toseparate the water supply from thesystem. Back-flow prevention devicesshould never be placed on the puri-fied water loop piping because theycan potentially contaminate the prod-uct water with bacteria, disinfectants,and metals. Back-flow prevention isonly necessary at the very beginningof the system to prevent contamina-tion of the city water by breaking theconnection to the dialysis water sys-tem.

Discharge of spent water anddialysate in the acute care settingshould be into an appropriate floordrain or standpipe connection. Ifthese are not available, a sink may beused as long as there is an air gap to

Figure 1Typical Pretreatment System

Source: Courtesy of Mar Cor Purification, Inc. Used with permission.

COLDIN

HOTIN

BLENDINGVALVE

BACKFLOWPREVENTER

BOOST PUMP

MULTIMEDIAFILTER

WATERSOFTENER

PRIMARYCARBON

SECONDARYCARBON

CARTRIDGEFILTER

TO R.O.

BRINE


prevent contaminated effluent fromback-flowing into the dialysis ma -chine, and the sink is not used for anyother purpose during the treatment.

Monitoring of back flow preven-ters is accomplished by inspectionafter installation, and an annualinspection thereafter. Backflow pre-venters must be installed by alicensed plumber and inspected by aqualified inspector.

Temperature blending valve(Tempering Valve). The tempera-ture blending valve mixes hot andcold water to achieve an RO mem-brane industry-standard temperatureof around 77° F (25° C). These valvesare widely used on large central ROsystems in geographical areas thattend to have cold incoming water.The colder the source water, thelower volume of purified water theRO membranes will produce. Foreach 1° F temperature drop, the ROmembrane produces 1.5% less puri-fied water (each 1° C drop equals a3% decrease in product water vol-ume). For instance, an incoming tem-perature of 50° F would result in anapproximate loss of 40% productwater flow rate compared to the flowrate achieved with 77º F water.

An alternative plan when tem-perature blending is not practical, asin single patient portable ROmachines, is to use larger or more ROmembranes. The larger membranesurface area produces more permeate(product water). If blending hot andcold water together from a sink faucetfor an acute dialysis treatment, a tem-perature gauge must be in place withan audible alarm because high tem-peratures can damage the RO mem-branes (though heat-tolerant ROmembranes exist, most are sensitiveto over-heating) and possibly harmthe patient if the dialysis machinetemperature alarm fails to place thedialysate flow in bypass.

Temperature blending valvesshall be sized to accommodate theanticipated range of flow and shall befitted with a means to prevent back-flow into the hot or cold water lines.A temperature gauge is normally inplace after the temperature blending

valve and the reading is recorded daily. Monitoring of tempering valves

is accomplished by observing theblended water temperature. This tem-perature should be documented onthe daily RO log sheet, and trendsshould be monitored. A temperaturethat fluctuates from day to day couldindicate an eminent failure of the tem-perature blending valve, which couldbe replaced proactively.

Booster pump. The entire ROsystem requires a constant supply ofwater flow and pressure to operatesuccessfully. Dialysis facilities experi-ence fluctuating or decreased incom-ing water pressure and flow, especial-ly since back-flow preventers andtemperature blending valves substan-tially lower the pressure of the feedwater. In order to compensate, abooster pump may be placed afterthese devices. Booster pumps shouldbe preceded and followed by pres-sure gauges that are read daily andthe readings recorded.

Monitoring the booster pump isaccomplished by observing the waterpressure. In many systems, the (low)pressure should be recorded whenthe pump turns on, and the (higher)pressure when the pump turns off.

Pretreatment ComponentsChemical injection systems. In

order for the RO to operate properlyand for the carbon tanks to removechlorine/chloramine effectively, theideal incoming water pH should be5.0 to 8.5. In many areas of the coun-try, the pH is higher than 8.5, so achemical injection system to lowerthe pH may be incorporated into thedesign of the pretreatment system,especially in the presence of chlo-ramine. A pH higher than 8.5 withchloramines present will cause thecarbon to be less adsorptive (a chemi-cal process) and the RO membraneperformance to degrade, resulting inpoor water quality (Leuhmann,Keshaviah, Ward, Klein, & Thomas,1989). To reduce the pH, chemicalinjection systems meter a smallamount of a strong mineral acid, suchas muriatic acid, also known ashydrochloric acid (HCl), or sulfuric

acid into the feed water system. Theuse of organic acids, such as aceticacid, is not recommended becausethey are nutrient rich and can encour-age the growth of bacteria in the pre-treatment and RO system.

Chemical injection systems mayalso be used to reduce chloramines inthe incoming water when the usuallysufficient carbon tanks alone are notadequate to do the job. Sodium bisul-fite and ascorbic acid are two chemi-cals that may be injected into thewater treatment system to aid in thereduction of chloramines (AAMI,2009a).

All chemicals shall be shown tobe compatible with all components ofthe water treatment system and in alloperation modes. For instance, if thesystem were to go into emergencyback-up and use deionization for itsprimary filtration, the additivesshould not create a toxic chemicalwhen combined with the deionizationresin. A means to verify that thereduction of the chemical additiveand its byproducts are decreased to asafe level before the product water isused for patients shall also beemployed, or there should be evi-dence that the chemicals in use do notcross into the bloodstream duringdialysis (i.e., they are not dialyzable).

Chemical injection systems dis-pensing acid should be placed beforethe sediment filter because the lowerpH will cause dissolved metals, suchas aluminum, and some salts in thefeed water to precipitate. The sedi-ment filter can then filter out most ofthe solidified particles.

Chemical injection devices con-sist of a reservoir that contains thechemical to be injected, a meteringpump, and a mixing chamber. Thesedevices are located in the incomingwater line. The device should be ableto tightly control the addition ofchemicals and have a control systemthat allows chemical to be injected inproportion to the water flow throughthe pretreatment tanks, or a pH mon-itor that automatically adjusts the in -jection of chemicals.

Monitoring of the chemical injec-tion pump is accomplished by moni-



toring the pH of the water. If an auto-mated injection system is used, thepH should be continuously moni-tored (AAMI, 2011). All material safe-ty data sheets (MSDS) and Occu -pational Safety and Health Admini -stration (OSHA) requirements mustbe followed for the safe handling ofchemicals used.

Sediment filters. Large particu-lates of 10 microns or greater that causethe supply water to be turbid – such asdirt, silt, and colloidal matter (suspend-ed particles) – may be removed by sed-iment filtration. Such foulants can clogthe carbon and softener tanks, destroythe RO pump, and foul the RO mem-branes. Unfortunately, not all suspend-ed materials are removed by sedimentfilters, and these materials can coat thesurfaces of the softener and carbonmedia, rendering these componentsuseless.

Many source waters, in spite oftheir apparent clarity, contain a largeamount of suspended particulate mat-ter that can adversely affect the ROsystem. A silt density index (SDI) testmeasures and evaluates how rapidly aspecial-sized screen becomes cloggedfrom a particular water source. MostRO membrane manufacturers recom-mend that feed water SDI not exceeda value of 5.0.

Sediment filters are typicallyplaced at the beginning of the pre-treatment cascade (series of compo-nents) and can be cartridge type fil-ters, single media filters, or multime-dia filters. Multimedia filters containlayers of various-sized media rangingfrom gravel to sand that physicallytrap the large particles as the water isfiltered downward through the tank.Each tier is composed of a different-sized media so that not all the partic-ulates are collected at the top, butrather, distributed through the mediabed. By using a stratified bed, increas-ingly smaller particles are captured,the entire bed is used, and the filter isnot rapidly clogged.

An automatic multimedia filter isbackwashed on a preset time sched-ule (when the system is not in use) sothat the media is cleansed and redis-tributed regularly. By redirecting the

water flow from the bottom of thetank upward (backwashing), the tight-ly packed bed is lifted so that thelighter material floats to the top andout to drain. The media, chosen for itssize and density, then resettles in itsordered layers when the process iscomplete. Multimedia filters shouldbe backwashed routinely – how oftendepends on the amount of particu-lates in the supply water and the pres-sure drop through the tank.

Monitoring of the sediment filtersis accomplished by measuring thewater pressure. Pressure gauges onthe inlet and outlet of the tank moni-tor pressure changes (delta pressure)and are read and recorded at leastdaily to monitor clogging of the filterbed. When the readings of the gaugesbefore the filter display a difference ofa predetermined value (e.g., 10 PSI orgreater) from the reading of the gauge

after the filter, it is time to backwash(multimedia type) or replace the filter(cartridge type). Multimedia filterstend to work better when they are alittle dirty. Further, the timer on thehead of the multi-media tank shouldbe visible and the time of day readingrecorded daily. When comparing thetime on the display with the actualtime, they should be the same unlessthere is a posted notice that the timeis off-set to allow sequential back-washing of multiple components.Situations such as power failures canresult in backwashing occurring dur-ing patient treatment. No patientharm would occur, but the patients’treatments would be delayed becausebackwashing would prevent waterflow to the RO.

Water softener. Hard watercontaining calcium and magnesiumforms scale or mineral deposits on the

Figure 2Water Softener



RO membranes and eventually foulsthe membranes. Once mineral de -posits form on the RO membranesurface, the membrane performanceand product water quality will de -cline. Mineral scale can become per-manent and decrease the life ex -pectancy of the RO membranes if notcleaned. Some source waters can foulRO membranes within hours if a sof-tener is not used, turning the mem-branes literally to stone. A softener isplaced before the RO unit to protectthe RO membrane life and beforedeionization (DI) in order to extendthe life of the DI (see Figure 2).

Softeners turn hard water into“soft” water by removing the hard-ness and exchanging it for sodium(see Figure 3). The resin beads withinthe tank have a high affinity for thecations calcium and magnesium (bothdivalent bonds) that are present in thesource water. The resin beads releasetwo sodium ions (monovalent bond)for every one calcium or magnesiumcaptured. Sodium chloride does notdeposit scale on the RO membranesand is rejected by the RO quite read-ily to the drain.

Hardness is measured in grains pergallon (grain literally meaning that thewhite precipitate left from evaporatedwater is the size of a grain of wheat) or

mg/L. To a lesser degree, softeners willalso remove other polyvalent cations,such as iron and manganese.

Softeners are sized in grains ofcapacity; 1 cubic foot (cu. ft.) of resinequals the exchange capability of30,000 grains of hardness as calciumcarbonate (CaCO3). A source wateranalysis that states the level of thehardness as CaCO3 is important indetermining the size of the softener. Aformula can be used to calculate howlong the softener will last before need-ing regeneration.

The softener can be placed beforeor after the carbon tanks. If the soften-er is placed before the carbon tanks,decreased softener resin life may occurif the resin is exposed to detrimentallevels of chlorine or chloramines in theincoming water. If the softener isplaced after the carbon tanks, the waterprocessed by the softener will not con-tain chlorine/chloramines, which canallow microbial growth within the sof-tener, increasing the bacterial biobur-den within the softener and down-stream to the RO membrane. Even inthe harsh environment of a softener,halophyllic (salt-loving) bacteria canthrive.

The softener needs regeneratingon a routine basis with concentratedsodium chloride solution (brine)

before the resin capacity is exhausted.Further, similar to multimedia filtersduring normal operation, the waterflows downward through the resinand can tightly pack the resin. Beforethe regeneration process, the resin isbackwashed to loosen the media andrinse away any particulates. After thebackwashing step, the brine solutionis drawn into the tank to regeneratethe resin. The calcium and magne-sium are forced off the resin beadsites, even though they possess astronger bond than sodium, becausethey are overwhelmed by the amountof sodium ions. Next, the excess saltsolution is rinsed out of the tank.

Regeneration is usually per-formed every day or every other daythat the softener is used at a timewhen the water treatment system isnot in use. Since high water flow andpressure are required for backwash-ing, generally one pretreatment tankis backwashed at a time. Most dialysisfacilities use a permanent softenerthat incorporates a brine tank andcontrol head to execute the automaticregeneration cycle. Automaticallyregenerated softeners shall be fittedwith a regeneration lock-out device toprevent the regeneration processfrom occurring during patient treat-ments, averting the possibility ofhighly concentrated sodium levels be -ing transported to the patients(AAMI, 2011).

Portable exchange softeners (soft-eners that are regenerated off-site) aresometimes used in areas that regulatethe amount of sodium chloride dis-charged to drain. In this case, the sof-tener tank will be replaced on a rou-tine basis and will not have a controlhead or brine tank. This type mayalso be used on single-patientportable RO systems in acute dialysissettings for quick turn-around andease. If portable exchange softenersare used, the water treatment vendoris expected to ensure that the tankshall be disinfected and rinsed beforeit is filled with the regenerated resin,and care shall be taken to keep non-potable water resins and potable ormedical resins separated during pro-cessing (AAMI, 2009a).

Figure 3Softener Ion Exchange


SoftenerResin



Monitoring of water softeners isaccomplished by testing water hard-ness post-softener. A hardness testusing an ethylenediaminetetraceticacid (EDTA) titration test, or dip andread test strips on the effluent soft-ened water, should be done at leastonce at the end of the day and record-ed (AAMI, 2011). Testing at the endof the day demonstrates that the sof-tener performed adequately all day inremoving hardness. While doing anadditional test at the beginning of theday is optional, this test would deter-mine whether the softener was regen-erated adequately during the night.Hardness test results should be lessthan 1 grain per gallon (gpg) hardness(less than 17.5 mg/L) and performedon water just processed, not waterthat has been in the tank all night.Start the water treatment systemapproximately 15 minutes prior todrawing the sample. A shorter inter-val is acceptable for the smallerportable systems. If the hardness testreads above 1 gpg, the softener mayneed regenerating before use. Checkthe timer in the control head to seethat it displays the correct time, andread and record the pressure from thegauges pre- and post-softener daily toassure the softener is not clogged. It isrequired that the face of the timer bevisible to the user (CMS, 2008b).

Brine tank. The brine tank con-tains the salt pellets and water to cre-ate the super-saturated salt solution(brine) used for softener regeneration.Fifteen pounds of salt are required toregenerate 1 cubic foot of resin(30,000 grain capacity). Only refinedpellet-shaped salt should be used. Saltdesignated as rock salt may containtoo many impurities, such as dirt, thatmay damage or clog the brine tank andsoftener control head (AAMI, 2011).

Monitoring of the brine tank isaccomplished by visual inspection.The salt level in the brine tank shouldbe inspected daily, and the tankshould be at least half-full with salt.Ascertain that a “salt bridge” has notformed by tapping on the top of thesalt in the tank. If a salt bridge hasformed, the salt will not dissolve intosolution, and when tapped, it will

break and fall into the tank. When asalt bridge forms, the softener will notregenerate to full capacity and wouldnot function for the expected durationof time. Record the level of salt in thetank daily.

Anion exchange resin tanks ororganic scavenger tanks removeorganic material from the sourcewater that would mask the adsorptionsites of the carbon media. Organicscavenger tanks can increase the lifeof the carbon tank when placedbefore the carbon tanks. A test on thesupply water for high levels of tannins(a plant chemical from decomposingleaves), lignines (a complex polymerin plant cell walls and wood), andtotal organic or oxidizable carbon(TOC) will determine whether anorganic scavenger is necessary in asystem. Seasonal changes will affectlevels of TOC, lignines, and tannin inthe source water.

Anion exchange tanks work on asimilar basis as softeners, but instead ofexchanging sodium, a cation, theyswap chloride, an anion, for organicmatter. Once an anion exchange tankis exhausted, it needs to be regenerat-ed. An inline TOC monitor can detectwhen organic chemicals are breakingthrough, or a water sample can be sentto a laboratory for analysis. The mostcost-effective plan is to regenerate thetank routinely according to the manu-facturer’s recommended schedule andbased on your source water becauseAAMI does not have a standard forthese organic compounds. Be mindfulthat if the tank does exhaust, thetrapped organics will be released andcould mask the carbon resin, causing itnot to work. If the tank is equippedwith a backwashing mechanism, itshould be equipped with a visibletimer and in and out pressure gaugesthat should be read and recordeddaily. The back-flushing cycle willremove sediment, but it will not regen-erate the anion exchange media.

If portable anion exchange tanksare used, the same requirementsapply as were mentioned for ex -change tanks for softeners: the tanksshall be disinfected and rinsed beforerefilling, and a separate process for

resins used for bio-medical purposesmust be demonstrated at the facility(AAMI, 2009a).

Carbon adsorption. Chlorineand chloramines are added to the citywater supply to disinfect the potablewater and reduce the risk of bacterialcontamination in the city water distri-bution system. A third chemical, chlo-rine dioxide, is gaining popularity as apre-disinfectant for raw water and isremoved before the post-disinfectionprocess at the municipality. Somemunicipal water treatment plants alsouse ozonation systems for disinfectionpurposes. Chlorine dioxide andozonation do not eliminate the use ofdisinfectants in the water distributedto customers, but they aid in reducingthe amount of disinfectant needed.You should be aware of what addi-tives and techniques your water sup-plier employs.

These additives allow us to drinkwater with minimal risk of becomingill from a parasite or pathogenic bac-teria. However, there are some draw-backs to the disinfectants themselves.For instance, chlorine can combinewith other organic chemicals to formtrihalomethanes, a known carcino-gen. For this reason, chloramines, acombined chlorine that cannot com-bine with other chemicals, hasbecome a major disinfectant of drink-ing water. But as compared to chlo-rine, a longer contact time is requiredfor chloramine to be adsorbed. Sincethe initiation of chloramine use, therehave been more reported incidents ofhemolysis and related symptoms inpatients on HD due to chloramineexposure when compared to similarreported instances with chlorine,though chlorine is also harmful topatients on HD (Ackerman, 1988;FDA, 1988; Leuhmann et al., 1989).

In addition to the serious risksexposure to chlorine or chloraminespresent to patients, neither chlorinenor chloramines are effectively re -moved by RO and actually damagethe thin film-type RO membranes.Therefore, chlorine and chloraminesmust be removed from the waterbefore the water enters the RO sys-tem. Further, chloramines must be


removed before DI because there is apossibility that carcinogenic nitro -samines may develop if non-carbonfiltered water enters the DI bed(Kirkwood, Dunn, Thomasson, &Simenhoff, 1981).

Carbon filtration will remove chlo-rine and chloramines that are almostalways present in the source water bymeans of adsorption. As the inputwater flows down through the granularactivated carbon (GAC), solutes diffusefrom the water into the pores of the car-bon and become attached to the struc-ture (see Figure 4). In addition, a widevariety of naturally occurring and syn-thetic organic compounds, such as her-bicides, pesticides, and industrial sol-vents, will be adsorbed as well(Leuhmann et al., 1989).

GAC is a type of carbon that isappropriate for HD and can be made

of many different organic materials,such as bituminous coal, coconutshells, peach pits, wood, bone, andlignite, that have been exposed toexcessive temperatures without oxy-gen to keep it from burning. GAC isthen acid washed to remove the ashand etch the carbon to increase theporosity and thereby the adsorbencyof the GAC. GAC used for dialysisshould be acid washed, especially car-bon derived from bone, wood, or coalbecause these types tend to leach met-als, such as aluminum, when they arenot acid washed and are thenexposed to water. Non-acid washedcarbon may be used but should berinsed thoroughly (AAMI, 2011).

GAC is rated in terms of an“iodine number,” which measures theability of the GAC to adsorb lowmolecular weight, small organic sub-

stances, such as iodine and subse-quently, chlorine and chloramines.The higher the iodine number, themore chlorine and chloramines willbe adsorbed. It would be ideal tohave a total chlorine number ratingfor carbon, but it is not the practice.An iodine number of 900 or greater isconsidered optimal for chlorine andchloramines removal (AAMI, 2009a).

Though not a regulation, anotherrating to consider with GAC is theabrasion number. The higher theabrasion number is, the more durablethe carbon is. This is importantbecause frequent backwashing associ-ated with carbon tanks can be wear-ing on the carbon.

Regenerated carbon that isreburnt and reused by the manufac-turer shall not be used for dialysis;only virgin carbon may be used(AAMI, 2009a). Carbon adsorption isused in many more toxic applicationsthan dialysis, and when regenerated,the carbon can retain impurities thatmay be toxic to patients. It is recom-mended that GAC has a mesh size of12 x 40 or smaller to provide a largesurface area, but not too small, or thesmaller particles will compact andflow will be impeded through the bed(Leuhmann et al., 1989). New carbonmust be rinsed by flushing water thor-oughly through the tank to removethe ash and carbon fines (small piecesof carbon), or these will damage theRO pump and membrane.

At least two carbon beds shall beused in a series configuration (wherethe effluent of the first tank feeds thenext tank) and shall have a sampleport after the first tank, and prefer-ably, one after the second tank.Sometimes tanks are arranged as aseries-connected pair (the waterstream is split and feeds into two ormore parallel sets of carbon tanks) sothat the tanks are not so large (seeFigure 5). In either set-up, each tankor group of tanks shall provide 5 min-utes empty bed contact time (EBCT)for a total of 10 minutes EBCT at themaximum anticipated flow rate, andthe water flow through the tanksshould be equal. A 5-minute expo-sure time of the water through each

Figure 4Carbon Filters

Source: Courtesy of Mar Cor Purification, Inc. Used with permis-sion.

CARBON ADSORPTION FILTER(BY-PASS OPTIONAL)

PSIGAUGE

VALVE

CONTROLVALVE TEST

PORTDRAIN

PIPE

TANK

CARBON

DISTRIBUTOR

GRAVEL



tank or set of the carbon tanks isrequired for the total chlorine in thewater leaving the tank to be reducedto less than 0.1 mg/L (AAMI, 2009b),with the second tank (or set of tanks)providing an equal level of redundan-cy. The contact time can be calculat-ed using the input flow rate (Q) in gal-lons per minute (gpm) and the vol-ume of carbon media in cu. ft. (V).Use the following formula to calculateEBCT (AAMI, 2011):

EBCT = (V/Q) x 7.48 where V = volume of carbon and

Q = flow rate in gallons per minute

Portable single-patient systems inthe acute or home care setting canmeet the requirement to reduce thechlorine level to below 0.1 mg/L withless than a 10-minute EBCT. This ismost often accomplished by incorpo-rating the use of carbon block technol-ogy. Solid block activated carbon(SBAC) is a densely compacted blockof GAC powder that has a large surfacearea in a compact size. A system mayincorporate a GAC tank and a carbonblock as the polisher, or may use twoSBACs in a series. The manufacturer isrequired to show the block carbon

technology is capable of achieving therequired chlorine re duction.

GAC has a finite capacity, andthere is a point at which its adsorptioncapacity is exhausted. The ability forthe carbon to remove chlorine andchloramines may be reduced whenother substances mask the reactivesites or when the pH of the waterincreases or the temperature decreas-es. Due to all these variables, it isimpossible to predict when the car-bon may exhaust, so frequent testingis mandatory. The chlorine/chlo-ramines level should be checkedbefore every patient shift. If there isnot a definite patient shift, the chlo-rine/chloramines test should be doneevery 4 hours (CMS, 2008b).

Carbon tank monitoring isaccomplished by testing the chlorinelevel as it leaves the first or “worker”tank. The N, N-diethyl-p-phenylene-diamine (DPD)-based test kits (e.g.,Hach™ digital tester) or equivalent(dip and read test strips) are recom-mended. Alternatively, an on-linemonitor may be used for automatedtesting. Proper quality control proce-dures, such as testing meters or stripsagainst known standards, is importantwith any method chosen.

In the 2001 AAMI RD62 stan-dard, the maximum allowable con-tamination levels for chlorine were0.5 mg/L for free chlorine and 0.1mg/L for chloramines (AAMI, 2001).In the new standard, the maximumlevel is simply 0.1 mg/L for total chlo-rine. Use of this lower level assuresthat the chloramines level is withinthe limit (AAMI, 2011). This level isreadily achievable with most dialysisfacility water systems, and many facil-ities have already implemented theuse of a single test because it is sim-pler and was an acceptable alternativein AAMI RD62.

If the total chlorine level after thefirst tank (or group of tanks) rises to0.1 mg/L or above (a positive testresult), total chlorine must be checkedafter the second tank (or tanks). Aslong as the test is negative after thesecond tank, dialysis treatments mayresume as long as arrangements havebeen made to change out the firsttank(s) within a 72-hour period, andmore frequent total chlorine testing isinitiated (e.g., test every half hour to 1hour) (CMS, 2008b). If the test resultafter the second carbon tank or set oftanks becomes positive, all treatmentsmust promptly cease to protectpatients from harm.

When replacing the carbon,whenever practical, the used secondcarbon tank may be placed in the firstposition, and the new tank put in thesecond spot. If it is not possible toswitch the position of the tanks, bothtanks should be replaced. Bypassvalves placed on the piping to the car-bon tanks that allow the feed water tocompletely bypass all the carbon tanksare unsafe and not recommended. Ifthere are any bypass valves present,they should be labeled with warningsand locked in the open position (e.g.,via zip or cinch plastic tie) so they can-not be accidentally repositioned.

Inherent problems with carbontanks are channeling (when water fol-lows the same path through the tankbecause water tends to flow in the pathof least resistance), compaction form-ing smaller carbon fines, and biologi-cal fouling because carbon is an organ-ic medium. These phenomena cause

Figure 5Paired Carbon Filters

Source: Courtesy of DaVita, Inc. Used with permission.

Inlet Outlet

Primary Secondary

Pri

mar

y S

amp

le

Sec

on

dar

y S

amp

le

GAC #1 GAC #2


the carbon surface area to be underuti-lized. Therefore, carbon tanks arebackwashed on a routine basis to“fluff” the bed, clean the debris out,and expose unused binding sites of thecarbon. Backwashing does not regen-erate the carbon. When the carbonadsorption sites are exhausted, the car-bon must be replaced. Cartridge orexchange carbon tanks may be used.These are not back-washable and needto be replaced on a more frequentbasis. In all cases, the emptied tankshall be disinfected and rinsed beforerepacking with new GAC.

Monitoring the carbon tanks alsoincludes documenting pre- and post-tank pressures, and checking the clockon the backwash timer for the correcttime so the timer does not begin abackwash cycle while treatments areoccurring. Document when the carbontanks have been exchanged or re-bed-ded, and include the grade of carbonused and the length of time the newcarbon is rinsed before use (if notrinsed thoroughly, the residue willharm the RO membranes).

Reverse Osmosis Systems Cartridge prefilter. Prefilters

are positioned after all the pre-treat-ment components and immediatelybefore the RO pump and membranesto capture particulates. Carbon fines,resin beads, and other debris exitingthe pretreatment components candestroy the pump and foul the ROmembranes. Typically, prefilters rangein pore size from 1 to 5 microns.Gauges monitor the filter inlet andoutlet pressures. If the delta pressureincreases by approximately 8 orgreater over the new filter pressuredifferential, the filter is clogged andneeds replacement. Prefilters areinexpensive insurance against damag-ing more expensive items down-stream in the system. Therefore,changing them on a routine basisbefore the delta pressure indicates theneed for such change is a good prac-tice. When removing the old filter,inspect the filter’s center tube for soil-ing. If dirt is present, the filter wasoverburdened and should have beenreplaced sooner. The housing of the

prefilter shall be opaque to deteralgae growth (AAMI, 2009a). Readand record pre- and post-filter pres-sures and the delta pressure daily.

RO pump and motor assem-bly. The RO pump (the noisy thingyou hear in the RO room) increaseswater pressure across the RO mem-branes to make pure water. RO sys-tems typically operate between 200 to250 PSI (pounds per square inch).

It is imperative that RO pumpsare made of high-grade stainless steel,inert plastics, or carbon graphite-wet-

ted parts. Brass, aluminum, copper,and other metals will leach contami-nants into the water and are not com-patible with peracetic acid-type disin-fectants. Operating RO pumps drywill cause irreparable damage. Moni -tor the inlet and discharge pressurescontinuously and record daily.

RO membranes. The RO mem-brane is the heart of the system.These membranes produce the puri-fied water through RO (see Figures 6and 7). RO is just that, the opposite ofosmosis. Osmosis is a naturally occur-

Figure 7Reverse Osmosis Membrane


Figure 6Basic Reverse Osmosis Element




ring phenomenon involving the flowof water from a less-concentratedcompartment (e.g., non-salty side) tothe more concentrated compartment(e.g., salty side) through a semi-per-meable membrane until solute equi-librium is obtained. In reverse osmo-sis, water (feed or supply water) isforced to flow in the opposite orunnatural direction across a semi-per-meable membrane to the compart-ment with less concentration ofsolutes by means of high hydraulicpressure (see Figure 8). Naturalosmotic flow is reversed, and purewater passes through the membrane,leaving the dissolved solids (salts,metals, etc.) and other solutes behindon the concentrated (or waste) side. Inan RO system, hydraulic pressureoverpowers the osmotic pressure.Dependent upon how much productwater is needed, the RO system willhave one or more membranes.

RO membranes are the tightestmembrane used in dialysis – theyhave pores that are much smallerthan those in a dialyzer membrane.RO membranes reject dissolved inor-ganic elements to the drain, such asions of metals, salts, chemicals, and

organics, including bacteria, endotox-in, and viruses. Rejection of chargedionic particles ranges from approxi-mately 95% to 99%, whereas contam-inants, such as organics that have nocharge, are sieved out if they are larg-er than 200 molecular weight. Ioniccontaminants are highly rejectedcompared to neutrally charged parti-cles, and polyvalent ions are morereadily rejected than monovalentions. pH of the incoming water anddamage to the membranes will changethe function of the RO and its rejec-tion characteristics.

Thin film (TF) RO membranesmade of polyamide (PA) are the mostcommon type used in HD. Thesemembranes are made with a thin,dense, semi-permeable membraneover a thick porous substructure forstrength and are spiral-wound arounda permeate collecting tube. The spiraldesign allows a large surface area tobe created in a small space. Theincoming water stream will split intotwo streams – one of purified waterthat crosses the membrane and theother a waste stream used to carryrejected solutes to the drain. This isknown as cross flow filtration.

TF RO membranes will degradewhen exposed to oxidants such aschlorine/chloramines, and therefore,must be preceded by carbon adsorp-tion. Bleach cannot be used to sanitizeTF RO membranes. Care must betaken with the use of peracetic acidproducts for disinfection because theywill oxidize the RO membrane if usedabove a 1% dilution, if left in contactwith the membrane longer than 11hours, or if iron deposits and othermetals are present on (or within) theRO membrane. Other factors that caninfluence RO membrane perform-ance and water quality in clude incom-ing water temperature and pH, ade-quate pretreatment, and cleanliness ofthe RO membrane surface.

TF membranes have a wide pHtolerance of 2 to 11; however, theoptimum pH range for membranefunctioning is 5.0 to 8.5. High alkalin-ity also enhances scaling of the ROmembrane surface (deposition of sub-stances on the membrane), whichreduces the available surface area.

RO membrane performance ismeasured by percent rejection. Finalproduct water quality is measured byconductivity and displayed as eithermicro-Siemens/cm or total dissolvedsolids (TDS). TDS is sometimes dis-played as mg/L and sometimes asparts per million (PPM), which areequivalent terms because there are 1million milligrams in a liter. TDSmonitors are actually just conductivi-ty monitors with a conversion factorbuilt-in – most often TDS is equal tomicro-Siemens/cm multiplied by~0.65 (different meters use differentconversion factors). Either percentrejection or permeate water qualitymonitors shall be used and continu-ously displayed, and should haveaudible and visual alarms when qual-ity set points are exceeded. When anRO is the final treatment component,the audible alarm shall be heard inthe patient care area. To preventpotential patient harm, if a predeter-mined set point is violated, the waterfor use should divert to drain. Smallportable RO systems are exemptfrom the divert-to-drain standardbecause one-to-one monitoring usual-

Figure 8Reverse Osmosis


Pressure Gauge

Water Intake Waste Water

Treated Water

Membrane


ly exists. If the quality of water pro-duced by a portable system fallsbelow the set quality limit, the treat-ment should be discontinued and thephysician notified (AAMI, 2011).

Percent rejection alone onlymeasures membrane performance.For example, if the source water is rel-atively pure, containing 100 PPM dis-solved solids (metals, salts, etc.), andthe percent of those dissolved solidsthat are rejected to waste equals 95%,the final water quality would display 5TDS mg/L or PPM. However, if thesource water had as much as 1000PPM, and the percent rejection con-tinued to be 95%, the final water qual-ity would then be 50 PPM. In eachscenario, the percent rejection is thesame 95%, but the final water qualityis significantly different. An AAMIchemical analysis is the only directway to measure the quality of thewater because the rejection rate andTDS do not specify which contami-nants are left. If the water quality fallsbelow the preset quality limits, themedical director shall be notified todetermine whether to continue treat-ments (CMS 2008a). However, “theuse of water outside of AAMI stan-dards should be extremely rare, con-sidered only when no other option isavailable to provide desperatelyneeded dialysis, and limited to onetreatment per patient” (CMS, 2008b).

AAMI has determined the maxi-mum allowable levels of contami-nants that can safely be in the waterfor HD without causing harm (seeTable 2). Usually, RO systems canproduce water that meets the AAMIstandards if the source water is drink-ing water that meets EPA guidelines.A double-pass or two-stage RO, inwhich product water from one RO isfed into a second RO, is sometimesused for extra purification. Deioni -zation may also be used to polish ROwater when the product water from theRO does not meet the quality standard.

RO systems, pumps, dialysismachines, and other equipment eachrequire a minimum flow rate andpressure to operate properly withoutdamage. RO system pressure gaugestypically measure the inlet water sup-

ply, pump, reject water (or waste),and product water pressures, whichare displayed as pounds per squareinch (PSI) or in actual gallons perminute (GPM) using flow monitors.Percent recovery (not to be confusedwith percent rejection) of a large ROsystem is generally set between 50%to 75%, meaning that if the RO has aGPM flow of 8 and a 50% recovery,half (or 4 gallons) of the incomingwater will be made into productwater, and the other half (or 4 gallons)will go to drain or be recycled backinto the feed water line. With 75%recovery, 75% of the water enteringthe RO would be made into productwater, and 25% would go to drain orrecycle. Many RO systems will recy-cle some of the reject stream toincrease the flow into the RO and toconserve water (waste recycle). MostRO distribution systems will return theunused purified product water back tothe system to decrease water wastage.

Scale deposits, such as calciumand magnesium salts, silt, metals,organics, and dirt, will accumulate onand eventually foul the exterior surfaceof the RO membrane. Routine clean-ing, usually quarterly, will strip off thescale and silt build-up. High pH clean-ers will remove the silt and dirt slimelayer, and low pH cleaners strip themineral scale and metal build-up.

Disinfection regimens vary wide-ly, but at least once a month isrequired for the system (AAMI,2011). It is also important to disinfectthe often-forgotten incoming waterline to the dialysis machine (Amato,1995; Bland & Favero, 1989). Weeklydisinfection of the storage tank anddistribution loop is a good idea withstorage tank systems. For portableRO systems, weekly disinfectionshould be performed, or wheneverthere is more than 48 hours of down-time (Amato, 1995). A method to pre-vent disinfectant from being deliv-ered to the patients (e.g., disinfectionlock-out) shall be provided by themanufacturer (AAMI, 2009a).

All gauges and flow metersshould be maintained within manu-facturer’s specifications, and readingsshould be recorded daily. Water qual-

ity (conductivity or TDS) should bewithin the limits defined for the facili-ty, checked against an independentdevice routinely, and recorded atleast daily. Percent rejection shouldbe above 90% and documented daily.While it is true for all measurementson a water treatment system, it isespecially important to include theexpected parameters for water qualityon the log sheet. Trend analysis isvital for monitoring water treatmentsystems. Monitoring trends allows theuser to be more proactive and to seea problem arising, rather than “put -ting out fires.”

Post-Treatment Components Deionization. DI is sometimes

required to polish the water when ROalone cannot reduce the contaminantsto levels within AAMI standards.Facilities may use DI as an emergencyback-up to the RO and have the tanksoff-line or in a “dry” stage ready fordeployment as needed. As an alterna-tive, there may be a contingency planwith a DI vendor to deliver the tanksquickly in case of an emergency.There is also an individual home HDtreatment system with a disposablewater treatment system that uses DI asthe primary water treatment compo-nent (NxStage Medical, Inc., 2006).

DI tanks contain resin beads thatremove both cations and anions fromthe water in exchange for hydroxyl(OH-) and hydrogen (H+) ions. Theions released combine to form purewater (H2O) (see Figure 9). Particleswithout an electrical charge are notremoved by DI as they are with RO,so non-ionized substances, such asbacteria and endotoxin, will not beremoved. In fact, the DI resin pro-vides a conducive environment formicrobial growth. Because of thepotential for bacterial contamination,DI shall be followed by an ultrafilter(UF) so that the downstream compo-nents are not contaminated andpatient safety is not compromised(AAMI, 2009a).

DI resins retain all the ions accu-mulated until the resins reach anexhaustion point. Before this occurs,the DI tank must be exchanged for a



new one. If a DI is used past its pointof exhaustion (measured by less than1 meg-ohm/cm resistivity, equal to aconductivity less than 1 microsi emen),the resins will release mass quantitiesof the more weakly attracted ions toaccommodate ions with higher attrac-tion. Weakly attracted ions, such asaluminum and fluoride, would beamong the first “dumped.” Patientinjuries and deaths have been report-ed when DI is used past the point ofexhaustion (Leuhmann et al., 1989).

DI tanks can be either dual-bedor mixed-bed varieties. The dual-bedtypes are tanks that contain either allcation- or all anion-attracting resinbeads and require at least two tanks,one cation and one anion, in series toremove the unwanted ions from thewater. Mixed-bed deionizers containboth cation- and anion-attractingresin beads in one tank, and producea higher quality of water than dualbeds. Dual beds may be used as longas they are followed by at least onemixed-bed DI tank. It is recommend-ed that when DI is in place, twomixed beds are used in a series con-figuration so if the first tank exhausts,it can be taken off-line and the secondone used for a short time, with con-stant monitoring, until the first DI isreplaced (AAMI, 2009a).

DI has a finite capacity: 1 cu.ft. ofDI resin equals 8,000 grains ofexchange capability. When the bed isexhausted, the resin must be replacedwith medical (or potable water) desig-nated resins (AAMI, 2001; FDA,1996; Leuhmann et al., 1989). DI isused for many industrial applications,such as in chrome plating factories,which can leave the resin full of tox-ins and heavy metals. These industri-al resins could harm patients andshould be regenerated separatelyfrom resins used for dialysis. Further,the emptied tanks should be disinfec-ted at the time of regenerating to pre-vent pyrogenic episodes in patients.

Carbon filtration shall precedeDI; otherwise, carcinogenic nitrosa -mines can develop when water that isnot carbon filtered contacts the resinbeads (AAMI, 2009a; Kirkwood etal., 1981; Leuhmann et al., 1989).

Figure 9

Figure 9aDeionization (DI) Ion Exchange Process


Figure 9bDeionization (DI) Ion Exchange – DI Exhausted


Sodium Chloride

Anion ResinCation Resin

Water

Sodium Chloride

Anion ResinCation Resin

Hydrofluoric Acid


DI shall be monitored continu-ously with a temperature compensat-ed audible and visual resistivity alarmthat is able to be heard and seen inthe patient care area. DI shall alsohave an automated divert-to-drainmechanism to prevent patient expo-sure to unsafe water (AAMI, 2009a).Since DI can exhaust and dump itsretained ions, DI is not recommend-ed for primary filtration (without RO)for the treatment of water for use withmultiple patients. DI coupled withUF is unable to remove low molecu-lar weight bacterial by-products, suchas microcystins (toxins from blue-green algae), that can be deadly topatients. Whenever DI is used, twotanks need to be set up in a series con-figuration, one as the worker, one asthe back-up.

Resistivity, which is the inverse ofconductivity, must be monitored con-tinuously and should read above 1meg-ohm/cm and be recorded twicedaily (AAMI, 2009a). Pre- and post-DI tank pressure readings should beread and recorded daily. DI tanksshould be exchanged on a regularbasis even if the resin is not exhaust-ed due to the microbiological foulingpotential. Bacteria and endotoxin lev-els post-DI and ultrafilter should beroutinely monitored.

Ultraviolet (UV) irradiator.UV is a low-pressure mercury vaporlamp enclosed in a transparent quartzsleeve that emits a germicidal 254 nmwavelength, delivering a dose of radi-ant energy to control bacteria prolif-eration. The UV is able to penetratethe cell wall of the bacterium andalter the DNA to either kill it or ren-der it unable to replicate.

It is possible for some species ofbacteria to become resistant to theUV irradiation, which is more of anissue if bacteria are exposed to sub-lethal doses. Therefore, the irradiatorshall be equipped with a calibratedultraviolet intensity meter that deliv-ers a minimum dose of radiant ener-gy at 16 milliwatt-sec/cm2 and acti-vates a visual alarm that indicates thelamp needs to be replaced. If the UVis not equipped with an intensitymeter, the dose of radiant energy

delivered shall be at least 30 milli-watt-sec/cm2. As the UV kills the bac-teria, it may increase the level ofendotoxin in the water as a result ofthe destruction of the gram-negativebacteria (endotoxin producing) cellwall where endotoxins harbor. To trapthe endotoxin, UV should be followedby ultrafiltration (AAMI, 2009a).

UV irradiation may also beplaced on the feed side of the watertreatment system, after all of the pre-treatment components (e.g., post-car-bon tank) and before the RO. Thiswill diminish the bacteria exiting fromthe tanks and reduce the bioburden tothe RO membranes. An appropriatelysized UV for the expected water flowand an easy-to-clean quartz sleevewould increase the effectiveness of theUV in this position.

Regular maintenance of the UVdevice includes replacing the lampwhen the radiant output indicates, orat least annually (or every 8000 hours

operation). Biofilm, a protective slimecoating that bacteria secrete whenthey attach themselves to a surface,will decrease the effectiveness of UV.Routine cleaning of the quartz sleevewill remove the biofilm. Record theoutput of the radiant monitor daily, aswell as the readings of any pressuregauges associated with the UV.

Endotoxin retentive, submi-cron, and ultrafilters (UF). A sub-micron filter reduces the level of bac-teria in the final product water,whereas an ultrafilter or endotoxinretentive filter removes both bacteriaand endotoxin (see Figure 10). Each isa membrane filter that can be a crossflow type with a feed stream, productstream, and reject stream (like ROmembranes), or a dead-ended designwith one stream.

It is recommended that any sub-micron, endotoxin retentive filters,and ultrafilters used in water treat-ment systems be validated for med-

Figure 10Endotoxin Filter




ical use. There are “nominal” and“absolute” ratings for UF and submi-cron filters in the industry. “Nominal”generally means “as stated on thelabel.” Absolute ratings are moreappropriate for dialysis applicationsbecause they are derived from a vali-dation process. Filters that are not formedical use may contain preserva-tives that require 500 to 1000 gallonsof water to thoroughly rinse. Oneincident occurred in New York in

1989 that was caused by the use of acommercially available, non-medicalfilter. Sodium azide, a desiccant andpreservative, was inadequately rinsedfrom the filter, and this exposurecaused nine patients to experiencelife-threatening hypotension, blurredvision, abdominal pain, headache,and loss of consciousness shortly aftertreatments began (FDA, 1989).

Though there are some ultrafil-ters and endotoxin retentive filters on

the market that have better flowdesigns, these filters in general havetighter pores, and thus, lower flowsand higher delta pressures across themembrane. These filters will decreaseflow velocity in the product waterloop if not designed and staged prop-erly. Whenever DI or UV is used, UFshall follow these devices. UF givesadded benefit when placed at pointsof use, such as at the source for reusewater, bicarbonate fill station, and in

Figure 11Indirect Feed Design


Figure 12Direct Feed Design



the dialysate flow path of each dialy-sis machine (Cappelli, 1991).

Submicron, endotoxin retentivefilters and ultrafilters, even thoughthey eliminate microbes, are targets forbacteria infestation if not routinelycleaned and disinfected or replaced.Membranes can become fouled withbacteria, which actually grow throughthe membrane, contaminating theproduct water. Routine bacteria andendotoxin testing is recommended.The pressure differentials pre- andpost-filter should be monitored contin-uously and documented at least daily.There should be some differencebetween the inlet and outlet pressures.If these pressures are the same, it ispossible that the water is flowingaround the filter and not through themembrane at all. On the other hand,too great a difference between the inletand outlet pressures (“delta”) indicatesthat the membrane is clogged. Filtersoperated in the cross flow designshould be fitted with a flow meter tomonitor the waste stream.

Distribution System Water storage. RO distribution

systems can be grouped into two cate-gories, direct feed and indirect feed. Adirect feed system “directly” deliversthe product water from the RO unit tothe product water loop for distribution(see Figure 11). Unused product wateris usually re-circulated back into theRO unit for conservation reasons.

An indirect feed system involvesa storage tank that accumulates theproduct water and delivers it to thedistribution loop (see Figure 12).Unused portions of the product waterare typically sent back into the stor-age tank. The RO unit will stop andstart filling the tank by receiving sig-nals from the high and low levelswitches on the storage tank.

Water storage and distributionsystems contain large amounts ofwater that no longer include chlo-rine/chloramine to prevent microbialgrowth. The larger volume and sur-face area increases the potential forbiofilm formation. The tank shouldbe designed to minimize the growthof bacteria by having a conical or

bowl-shaped bottom to allow forcomplete emptying, and have a tight-fitting lid that is vented to air througha hydrophobic 0.45 m air filter to pre-vent microbes from entering the tank.The tank should be designed for easy,frequent disinfection and rinsed withan internal spray mechanism. Storagetanks shall be made of inert materialsthat do not leach contaminants intothe purified water, and the size of thetank should be in proportion to meetthe facility’s peak demands, no larger(AAMI, 2009a; FDA, 1996; Leuhmannet al., 1989).

In the 2001 version of the AAMIstandards (AAMI, 2001), there was arecommendation that the flow veloci-ty in the distribution system be main-tained at 1.5 ft/sec for direct feed sys-tems, and 3.0 ft/sec in indirect feedsystems. The 2009 AAMI standard(AAMI, 2009a) does not specify a rec-ommended flow velocity because therewas no evidence that a certain velocitywould prevent biofilm formation.

Storage tanks require a recircula-tion pump made of inert, non-leachingmaterials that can meet the challengeof the higher velocities of flow neededto supply water to a group of dialysismachines. An aggressive and frequentdisinfection program should beemployed. Many facilities disinfect thedistribution system on a weekly basis.Monitoring bacteria and endotoxin isrecommended after the storage tank;the air vent filter should be replacedroutinely. Pre- and post-pump pres-sures should be recorded daily.

Water distribution piping sys-tems. A continuous loop designwhere the water returns to the storagetank or to the RO unit will conservewater and is the recommendeddesign. No dead-ends or multiplebranches should exist in the distribu-tion system (e.g., a branch sendingpurified water to the hospital labora-tory) because these are places watercan stagnate and allow bacteria andbiofilm to grow.

Highly purified water is veryaggressive and will leach metals andchemicals from materials with which itcomes in contact. Polyvinyl chloride(PVC) is the most common piping

material used in the United States fordialysis because of its low cost and rel-atively inert nature. Other substancesthat may be used include, but are notlimited to, chlorinated PVC (CPVC),polyvinylidene fluoride (PVDF), poly-ethylene (PE), cross-linked polyethyl-ene (PEX) polypropylene (PP), andstainless steel (SS). Though thesematerials may be more inert thanPVC, they tend to be more expen-sive. Extreme attention to detail ininstalling the distribution system isimperative: if the system is plumbedimproperly, many problems canresult, wasting time and money andpotentially placing patients at risk ofharm. No copper, brass, aluminum,lead, zinc, or other toxic substancesshall be used in the piping; nor shallthe piping contribute bacterial con-tamination. The inner surfaces of thejoint connections should be assmooth as possible to avoid microbio-logical adhesion; smooth bevelededges should be used in connections(rather than hacksawn edges), andsimple wall outlets with the shortestpossible fluid path and minimumpipe fittings are recommended(Leuhmann et al., 1989).

The distribution system should beevaluated routinely (e.g. quarterly) andthe loop visually inspected (when pos-sible) for incompatible materials thatmay have been inadvertently added.Loop repairs should be performed bytrained personnel or reputable plumb -ers, and all materials used should beinspected for compatibility. Disinfec -tion should always follow any invasiverepair to the system. Bacteria andendotoxin testing should be done rou-tinely on the loop (AAMI, 2011; FDA,1996; Leuhmann et al., 1989).

Alternative Disinfection Of Water Systems

Biofilms are communities of micro -organisms attached to surfaces. Oncebacteria and other microorganismsattach to a surface, they excrete anextracellular polymer or glycocalyxthat will both protect them from chem-icals and supply nutrients to maintainlife (Meltzer, 1997). Any where non-sterile water flows, biofilm will form.



Biofilms offer bacteria and othermicrobes an endless supply of foodand protection against most disinfec-tants. Even with routine chemical dis-infection, biofilm can form. Biofilmsform faster in slow-moving water andhave a more difficult time attachingthemselves in fast-moving water, buteventually they will take hold.

Bleach and ozone are the mosteffective means for reducing or re -moving biofilms (AAMI, 2011). Oncea biofilm has firmly established itself,it is nearly impossible to eradicate.Many times entire water treatmentsystems and distribution piping havehad to be replaced to eliminate abiofilm problem.

Ozone disinfection. Ozone is avery powerful oxidizing agent that isin the form of a gas, O3, that is formedfrom oxygen being put through anelectrical generator placed onsite.The ozone generated is then injectedinto the water. With sufficient expo-sure time, ozone can sometimes erad-icate existing biofilms.

Ozone has a very short half-life ofabout 25 minutes at 20º C in highlypurified water. In the presence of organ-ic and inorganic impurities, ozone willdegrade more rapidly. Exposure toUV irradiation will quickly removeozone. Ozone must always be rinsedout of the system, and its absence ver-ified prior to the water being used forpatient treatment.

The by-products of ozone in thepresence of impurities (e.g., biofilm)are safe and include carbon dioxide,carboxylic acids, filterable solids, andneutralized organics (such as inacti-vated endotoxin). Ozone has beenclassified by the FDA as generallyrecognized as safe (GRAS). TheOSHA maximum exposure level forambient ozone is 0.1 ppm over a timeweighted average of eight hours in afive-day period (shorter exposuretime to higher levels [e.g., 0.3 for 15minutes] is acceptable). To preventozone from getting into the air, it isrecommended that the storage tanksystem and piping remain closedwhen ozone is in use.

Ozone is not recommended forRO disinfection because the powerful

oxidant will destroy the membranes.The facility must continue to usechemical disinfection for the RO unit.Because ozone is easy to make (usingair and an ozone generator) and doesnot require a lengthy rinse time, it isconvenient to use on the storage tanksystem and distribution piping.

Because all distribution piping sys-tems are different, each system wouldhave to be evaluated for compatibilitywith ozone. Ozone, for example, is list-ed as being incompatible with PVC,the material used in most distributionpipes. However, at the low levels usedfor disinfection purposes, between 0.3to 0.7 ppm, the PVC is hardly affected.Bleach is also not compatible withmany materials, but at low concentra-tions, is considered acceptable. Ozonecan be aggressive with UF filters madeof polysulfone, so ultrafilter and endo-toxin retentive filter materials wouldhave to be considered when decidingto use ozone (Amato & Curtis, 2002;Meltzer, 1997; Murphy, 1998).

A test based on indigo trisulfonateor an equivalent (e.g., DPD with a con-version factor) will indicate the absenceof ozone in the water. An ambient airozone test should be performed rou-tinely to comply with the OSHA-per-missible exposure limits (AAMI, 2011).

Hot water disinfection sys-tems. The use of hot water disinfec-tion is well known in the HD industrybecause many dialysis machines usethis method for routine disinfection.However, hot water disinfection hasnot commonly been used in the U.S.for water treatment system disinfec-tion because heat is not compatiblewith PVC piping. Some manufactur-ers supply an RO system that is com-patible with heat disinfection thatincludes RO membranes, which canwithstand high temperatures, butmost existing RO systems are notheat-tolerant. If the RO is not heat-tolerant, hot water could still be usedto sanitize the storage tank and distri-bution system. Piping materials, suchas PVDF, SS, PEX, and PP, are com-patible with hot water disinfection.

Hot water disinfection will notremove established biofilms. It is,however, a convenient disinfection

process that requires little to no rinsetime, so it could be used more often,thus preventing the formation ofbiofilm. An occasional chemical dis-infection may be necessary.

Generally, a minimum of 80º Cfor a 10-minute exposure time willperform a more than adequate disin-fection of an RO system and distribu-tion loop. The temperature and con-tact time need to be established andvalidated by the manufacturer of thesystem. It is recommended that thetemperature be monitored and re -corded at a point most distal from thewater heater. Demonstration of reach-ing the correct temperature for theright amount of time is considered asuccessful disinfection (AAMI, 2011).

Bacteria and EndotoxinsThe major change in the 2011

update of the AAMI standards wasthe adoption of a set of fiveInternational Standard Organization(ISO) documents, listed in Table 6,that include recommendations oflower bacterial and endotoxin levelsand different culturing methods (seeTable 3) as replacement documentsfor the 2004 AAMI RD52 document.(Note: Four of these documents wereapproved by AAMI in 2009 and arereferenced here with their 2009dates). It must be noted that CMSadopted the 2004 AAMI RD52 doc-ument as regulation and has not yetproposed adopting the updated docu-ments. While the 2004 AAMI RD52standard and CMS allow higher lev-els of bacteria and endotoxins, userswould be in compliance with CMSregulations should the user choose tofollow the newer recommendationsfor lower bacterial and endotoxin lev-els because these would be consid-ered more stringent than the mini-mum CMS requirements.

Bacteria testing of productwater. The 2009 AAMI standardsrequire that the bacteria levels inwater used for HD shall not exceed100 colony forming units/ml (CFU/mL) with an action level set based onknowledge of the microbial dynamicsof the system. Typically, the actionlevel will be 50% of the maximum


allowable level (AAMI, 2009b). If theaction level is violated, the facilitymust show it is taking some action(e.g., disinfection, re-assaying) toaddress the potential problem. At aminimum, bacterial levels should betested monthly. Weekly bacteriaassays are recommended for new sys-tems until a pattern of compliancewith the allowable level is established(e.g., 1 to 2 months) (AAMI, 2011).

At a minimum, water samplesshould be collected from the first andlast outlets of the water distributionloop, water entering the reprocessingequipment, water used to prepareconcentrates, and water exiting theDI, UF, UV, and storage tank sys-tems. The outlet should be allowed toflow for 60 seconds before obtainingthe sample. Sample ports should notbe disinfected with bleach or betadinebecause the residual disinfectant willkill any potential bacteria in the sam-ple. Alcohol may be used on the out-side of the ports if allowed to drycompletely before samples are taken(AAMI, 2011).

Bacteria assaying technique.Samples that cannot be assayed with-in four hours can be refrigerated forup to 24 hours after collection. Totalviable counts shall be obtained usingthe membrane filter technique (wherea known volume of water is filteredthrough a membrane, and the mem-brane is then aseptically transferred toan agar plate) or the spread plate tech-nique (an inoculum of at least 0.1 to0.3 mL of sample is spread over theagar). Use of a calibrated loop toapply the sample is prohibited; thismethod is not sensitive enough forHD bacteria testing because the sam-ple used is too minuscule. Culturemedia should be tryptone glucoseextract agar (TGEA), Reasoners 2A(R2A), or other media that can bedemonstrated to provide equivalentresults. Blood and chocolate agar aretoo nutrient rich and will kill the bac-teria being tested and should not beused. Samples shall be incubated at17° to 23° C for 168 hours (sevendays) (see Table 4). Colonies shouldbe counted using a magnifying device

(AAMI, 2011). Note that the cultureparameters described by this newstandard are different than the shorterincubation time and higher tempera-tures required by the 2004 AAMIRD52 standards adopted by CMS asregulation. These more current stan-dards may be adopted by facility pol-icy; following these more stringentstandards in both culture parametersand action and maximum levelswould be in compliance with the min-imum CMS requirements.

Endotoxin testing of productwater. Note that the newer standardsrequire a lower endotoxin level thanthe 2004 ANSI/AAMI RD52 stan-dards. As referenced by the 2011ANSI/AAMI/ISO 23500 standards,endotoxins in the water used for HDpurposes shall not exceed 0.25EU/mL (endotoxin units/mL), andaction must be taken when the levelexceeds 0.125 EU/mL. Endotoxintesting is done with the LimulusAmebocyte Lysate (LAL) assay usingeither a kinetic assay or a gel-clotassay. The kinetic assay is more reli-able and sensitive than the gel-clotmethod because it uses computer-driven spectrophotometry that calcu-lates the amount of endotoxin. Thegel-clot assay only renders a negativeor positive result at a given concen-tration. At a minimum, two tubesshould be run each time the gel-clotmethod is used, one for control andone for testing the sample. Whendrawing the water samples for endo-toxin, the same techniques apply asfor bacteria sampling, as long as thesefollow the recommendations of thetest manufacturer or the laboratory,and endotoxin-free sample collectiontubes are used (AAMI, 2011).

Bacteriology of DialysateThe aforementioned assaying

techniques will work for dialysatesamples. Routine sampling of bicar-bonate concentrate for bacteria isunnecessary unless it is believed to bethe source of a problem. If testing ofbicarbonate is needed, the concen-trated sample will need to be dilutedto be tested (AAMI, 2004). AAMI

Table 3Comparison of Maximum Allowable Levels of Bacteria

and Endotoxin in HD Water According to ANSI/AAMI RD52:2004 and ANSI/AAMI/ISO 13959:2009

Bacteria Limit/ActionLevel (CFU/mL)

Endotoxin Limit/ActionLevel (EU/mL)

ANSI/AAMI RD52:2004 < 200/50 < 2/1

ANSI/AAMI/ISO 13959:2009 < 100/50 < 0.25/0.125

Source: Ward, 2011. Reprinted with permission.

Table 4Comparison of Bacterial Culture Conditions According to AAMI/ANSI

RD52:2004 and ANSI/AAMI/ISO 11663:2009

ANSI/AAMI RD52:2004

ANSI/AAMI/ISO11663:2009

Medium Trypticase soy agar Tryptone glucose extractagar or Reasoner’s 2A agar

Incubation Temperature (C) 35 17 to 23

Incubation Time (h) 48 168

Source: Ward, 2011. Reprinted with permission.



Dialysate samples shall be drawnwhere the fluid enters the dialyzerfrom the Hansen connector or a portin the dialysate line for this purpose(AAMI, 2011).

Assays should be repeated if thebacteria or endotoxin levels in thedialysate violate the action level. Fornew systems, weekly testing shouldbe performed until the bacteria andendotoxin in the dialysate demon-strate a pattern of compliance withthe limits. If a patient exhibits anendotoxin reaction or septicemia,dialysate and water sampling shouldbe done as close in time to the eventas possible, along with blood culturesand other tests that the medical direc-tor may dictate. If the endotoxin reac-tion arose due to endotoxin build-upin the reprocessed dialyzer, it may bedifficult to confirm because LAL test-ing may be negative in this instance (aprotein carrier, like blood, is neces-sary to draw-out the endotoxin fromthe dialyzer). In facilities that practicereuse of hemodialyzers, close atten-tion must be paid to water used forreprocessing, and these practicesshould be evaluated with any patientreactions potentially related to expo-sure to endotoxin.

Ultrapure DialysateThough fluid and solutes mainly

flow from the blood side of the dia-lyzer into the dialysate and down the

drain, dialyzers with highly perme-able membranes, such as high-fluxdialyzers, can have back-filtration andback-diffusion occurring due to theirlarge pore size. This allows water andsolutes to flow from the dialysate intothe blood side of the dialyzer(Leypoldt, Schmidt, & Gurland,1991). This results in a concern thatendotoxins and endotoxin fragments,which are small enough to cross thehigh-flux porous membrane, maycause acute and/or long-term symp-toms in patients.

Quite a number of researchpapers conclude that the long-termeffects of exposure of patients on dial-ysis to endotoxin and other cell frag-ments from gram-negative bacteriaresults in a chronic inflammatoryresponse. AAMI has therefore takena step toward more strict standards indialysate. Chronic endotoxin expo-sure from dialysate, at a level lowerthan that which causes an acute pyro-genic reaction (e.g., temperaturespike, chills, rigors, hypotension) canstimulate pro- and anti-inflammatoryactivities, resulting in decreased trans-ferrin, increased beta-2 microglobu-lin, and amyloidosis, leading to carpaltunnel syndrome and accelerated ath-erosclerosis (Canaud, Bosc, Leray,Morena, & Stec, 2000). Elevated C-reactive protein (CRP) levels from theacute phase inflammatory res ponsecan predict mortality and morbidityin patients on HD and have beenlinked to malnutrition, resistance toerythropoietin, and when combinedwith cholesterol and triglyceride lev-els, increased cardiovascular risk(Panichi et al., 2000).

Ultrapure dialysate should have aviable microbial count less than 0.1CFU/mL and an endotoxin levellower than 0.03 EU/mL. If the levelsare violated, action must be taken tocorrect the situation. The user isresponsible for developing a monitor-ing plan, including testing frequency,that would keep the microbial andendotoxin levels within the standard.Dry powder bicarbonate cartridgesare frequently used to achieve the lowmicrobial standard because bulkbicarbonate is more easily contami-

has broken up the dialysate purityinto three different categories – con-ventional dialysate, ultra-pure dialy -sate, and dialysate for infusion (seeTable 5).

Conventional DialysateConventional dialysate should

contain a viable microbial level lessthan 100 CFU/mL, with an actionlevel of 50 CFU/ml. The endotoxinlevel should be less than 0.5 EU/mL,with an action level of 0.25 EU/mL.While the bacterial standard is thesame for product water, the allowablelevel of endotoxins in conventionaldialysate is higher than the allowablelevel in dialysis water in recognitionthat the components used to consti-tute concentrates may contributeendotoxins (AAMI, 2009b). If theaction levels are violated, steps shouldbe taken to address the issue, such asdisinfection of the dialysis machineand/or resampling.

AAMI and CMS regulationsrequire that dialysate samples shouldbe collected from at least twomachines per month, making sure allmachines are tested within a year(CMS 2008a). Some states mayrequire all machines to be sampledwithin a quarterly period. Themachines tested are to be viewed as asample of all machines; a pattern ofpositive test results should result inaction taken to address all machines.

Table 5Comparison of Maximum Allowable Levels of Bacteria

and Endotoxin in Dialysate According to AAMI/ANSI RD52:2004 and ANSI/AAMI/ISO 11663:2009

BacteriaLimit/Action Level

(CFU/mL)

EndotoxinLimit/Action Level

(EU/mL)

ANSI/AAMI RD52:2004

Standard < 200/50 < 2/1

ANSI/AAMI/ISO11663:2009

Standard < 100/50 < 0.5/0.25

Ultrapure < 0.1 < 0.03

Substitution Fluid Sterile Non-pyrogenic

Sources: AAMI, 2009d; Ward, 2011. Reprinted with permission.


nated with microbes and endotoxin(AAMI, 2004). The use of in-lineultrafiltration on the dialysate mayalso be necessary to achieve the lowmicrobial/endotoxin standard.

Dialysate for InfusionIn the United States, convective

therapies, where a large volume of anelectrolyte solution (20 to 70 L) isinfused into the patient’s blood forreplacement, is not commonplace.Hemodiafiltration and hemofiltrationtherapies require sterile replacementfluids. In Europe, machines are com-mercially available that will producethe sterile solution online from con-ventional dialysate by sequentialultrafiltration through the use of UFmembranes. Dialysate for infusionshould be sterile and non-pyrogenic(AAMI, 2009b). The manufacturer ofthe equipment must validate the abil-ity of the equipment to consistentlyproduce water that meets theserequirements. The user should followthe manufacturer’s guidelines for use,monitoring, and maintenance so theequipment used will continue to meetthe specifications through an estab-lished process (AAMI, 2009b).

Table 6Relationship Between Previous AAMI Standards for Hemodialysis Fluids and

Newly Adopted ISO Standards

New Standard Content Previous Standard

ANSI/AAMI/ISO 13958:2009,Concentrates for Hemodialysis andRelated Therapies

Production of dialysate concentrates ANSI/AAMI RD61, Concentrates forHemodialysis

ANSI/AAMI/ISO 13959:2009, Water forHemodialysis and Related Therapies

Water quality standard ANSI/AAMI RD62, Water TreatmentEquipment for Hemodialysis Applications(part)

ANSI/AAMI/ISO 11663:2009, Quality ofDialysis Fluid for Hemodialysis andRelated therapies

Dialysate quality standard ANSI/AAMI RD52, Dialysate forHemodialysis (part)

ANSI/AAMI/ISO 26722:2009, WaterTreatment Equipment for Hemodialysisand Related Therapies

Water treatment equipment ANSI/AAMI RD62, Water TreatmentEquipment for Hemodialysis Applications(part)

ANSI/AAMI/ISO 23500:2011, Guidancefor the Preparation and QualityManagement of Fluids for Hemodialysisand Related Therapies

User guidance on achieving compliancewith fluid quality standards

ANSI/AAMI RD52, Dialysate forHemodialysis (part)

Sources: AAMI, 2009c; Ward, 2011. Reprinted with permission.

The Philadelphia IncidentEven though there have been many more recent incidences with chloramine

poisoning of patients, the most noted example remains the “Philadelphia Incident”of 1987 be cause it was multifaceted. Initially, a nurse in the facility noticed anunusually large number of hematocrit values that were lower than normal. Patientsalso complained of head aches and malaise, and were hypotensive. After two tothree days of symptoms, it became apparent that chloramine was the culprit caus-ing hemolysis. Forty-four patients out of 107 required transfusions, and 10 weresent to the emergency department for additional treatment. Fortunately, thanks tocareful clinical monitoring, no patients died during this event (Ackerman, 1988;FDA, 1988).

Upon further investigation, it was discovered that the water requirements forthe facility had increased, and a water vendor added more RO membranes withoutincreasing the size of the pretreatment carbon beds to accommodate the higherflow rate. The staff person monitoring the system recorded the chloramine levelsaccurately as they climbed to toxic levels (AAMI maximum level is 0.1 mg/L), butthe staff member was not aware that this was a dangerous situation and did notreport it to a supervisor. Further, no written policy was in place regarding the test-ing of total chlorine levels, and double checks with signatures were not standardprocedure. Finally, the staff erroneously believed that backwashing the carbonwould regenerate the tank (Ackerman, 1988; FDA, 1988).

This incident illustrates the need for staff education, choosing reputable watervendors, having proper policies and procedures in place, and re-evaluating theentire water treatment system if any component is changed.



New Hemodialysis Fluid Standards During the years 2009 to 2011,

AAMI participated in the develop-ment of international standards forthe purity of water and dialysate usedin dialysis. These International Stand -ards Organization (ISO) standardshave been adopted by AAMI as theUnited States standards. A compari-son between these five new standardsand the previous AAMI standardsthat they replaced is shown in Table6. While the level of chemical con-taminates remains the same (exceptfor the change to the use of a lowerlevel for total chlorine to allow a sin-gle test to be used), there are signifi-cant differences in microbiologicalcontamination and culture methods.

It is important to remember thatwhile AAMI has adopted new stan-dards, the 2008 revision of the CMSConditions for Coverage incorporat-ed the entire 2004 AAMI RD52 doc-ument and the sections of the 2001AAMI RD62 document referencedby RD 52 into the regulations for dial-ysis facilities. Until CMS revises theConditions for Coverage, surveyorswill use the older standards as theminimum requirement that facilitiesmust meet. This time should be usedby facilities to develop methods toassure that the new standards can bemet to improve the quality of care forpatients and to be prepared whenCMS adopts the new standards.Because the newer standards aremore stringent than the older stan-dards, a facility that choses to adoptthe newer standards and follows thoserequirements would be considered incompliance with CMS requirements.

It is important to understand thatmonitoring of microbiological con-tamination in dialysis water systemsshould focus on establishing a routinethat prevents the development ofgrowth in the system. A protocol thatuses monitoring to retroactively de -cide when to disinfect a system willinevitably result in exceeding the bac-terial purity standards.

SummaryBy understanding water treat-

ment system operation, dialysatepurity issues, and the nuances ofpatient reactions, and by workingclosely with technicians, nephrologynurses can protect patients fromunsafe water and dialysate and con-tribute immensely to long-term posi-tive outcomes for patients.

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water treatment for hemodialysis: an update

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