Dialysis Water Treatment

Dialysis Water Pre-Treatment Plant
By: Dr. Eng. Walid Tarawneh
Introduction
Appropriate water quality is one of the most important aspects of ensuring safe and effective delivery of
haemodialysis. Haemodialysis may expose the patient to more than 300 lt of water per week across the
semipermeable membrane of the haemodialyser. Healthyindividuals seldom have a weekly oral intake of water
above 12 lt. The near30 timesincrease inwaterexposure todialysis patients requires control and monitoring of
water quality to avoid excesses of known or suspected harmful elements being carried in the water and
transmitted to the patient.
Water Treatment
The water to be used for the preparation of haemodialysis fluids needs treatment to achieve the appropriate
quality. The watertreatmentisprovidedbyawaterpre-treatmentsystemwhichmayinclude variouscomponents
such as sedimentfilters,watersofteners,carbontanks,micro-filters,ultravioletdisinfectionunits,reverse osmosis
units, ultrafilters and storage tanks. The components of the system will be determined by the quality of feed
water and the ability of the overall system to produce and maintain appropriate water quality.
Dialysis Water Pre-Treatment System Classification
The Food andDrug Administration(FDA) regulatesdialysiswaterpurificationsystemsandclassifieswatersystems,
along with dialysis machines, as Class II medical devices (FDA, 2011). Class II devices require diligent tracking of
critical componentsand a complaintinvestigationsysteminplace.ClassIdevicesinclude loosely regulated items,
such as tongue depressorsandBand-Aids,whileClassIIIdevices,suchashigh-fluxhemodialyzers and implantable
pace makers, are stringently regulated devices and require tracking of all parts (even nuts and bolts)
(FDA,2009).
Risks Associated with Water Contamination
Failure to ensure adequate water quality may have dire consequences to patient safety and welfare. Patients
undergoing haemodialysis may show signs and symptoms caused by water contamination, which can lead to
patient injury or death. Some of the important possible signs and symptoms due to water contamination are
listed below in Table 1[2]
Table 1

Essential Operational requirements
1. Dialysis staff should have a fundamental understanding of water pre-treatment for haemodialysis, and
participate in the rational design and safe running of haemodialysis water pre-treatment plants
2. Written policies, practices and procedures shall be in place for the safe operation of the dialysis water pre-
treatment system.
3. Dialysis staff shall be trained and deemed to be competent in the safe operation of the dialysis water pre -
treatment system.
4. Dialysis related practices shall be regularly audited.
5. The Association for the Advancement of Medical Instrumentation (AAMI) standards [1] are the accepted
minimum standards for water pre-treatment for haemodialysis.
6. Haemodialysis should never take place without, at a minimum: a multimedia filter, carbon filtration, a 1
micron filter and reverse osmosis. Further filtration may be used at the discretion of individual units, to
further extend the life of the equipment.
7. Dialysis water quality shall be regularly tested.
8. To ensure safe chlorine andchloraminelevelsin pre-treated water, water for haemodialysis shall be tested.
All chlorine and/or chloramine testing results shall be recorded after the start of each dialysis shift.
9. The writtenpolicies,practicesandproceduresshall cover the protocol and methodology for chlorine and/or
chloramine testingandthe appropriate responsestoresultsshowing a high concentration of chlorine and/or
chloramine.
10. Dialysis staff shall be trained, periodically educated and deemed to be competent in water quality risk
management.
11. All activities, services, maintenance, interventions and changes to the water pre-treatment plant shall be
recorded in water pre-treatment Logbook, available in a convenient location.
12. Water quality and plant function shall be reviewed by a multidisciplinary committee made up at least of
senior nursing, medical and technical staff and other appropriate stakeholders on a monthly basis, and
minutes kept.
13. Minutesshouldbe circulatedtoappropriate healthservice authorities,toindicate saferunningof the dialysis
room and the dialysis water pre-treatment plant.
Planning Requirements
Nephrologists shall have a fundamental understanding of the water pre-treatment required for haemodialysis.
Nephrologists should participate in the rational planning, design, operation and maintenance of water pre -
treatmentsystems. Planningthe design,operationandmaintenance of waterpre-treatmentsystemshall be done
very early in the setting up of a Renal Dialysis Unit.
Responsibilityforthe safe andeffective designandrunningof waterpre-treatmentsystemsissharedbetweenALL
dialysis staff, including dialysis water consultants.
The Planning consideration for the design and installation of the water pre-treatment system shall include [3];
1. The quality of the feed water.
2. The maximum temperature of the feed water
3. The pressure of the feed water.
4. The maximum water flow, including expected future growth in the number of patients to be treated.
5. Average water flow per day also including expected future growth.
6. Space required for safely installing and operating the water pre-treatment plant.
7. Drainage required.
8. The weight of the water pre-treatment plant and the ability of the floor to safely support that weight.
9. Water quality monitoring systems.
10. The capacity of the power supply for the water pre-treatment plant.
11. Facilities to safely service and maintain the water pre-treatment plant.
12. Water distribution loop.

Withthe above informationthe contractororproviderwill be able todetermine the type,size,volume,weight
and location for the safe operation of the water pre-treatment plant.
Main System Components
 General Block Diagram (fig.1)
Fig.1
 Typical Pre-TreatmentSystem(fig.2)
Fig.2

 SystemComponents and main considerations
1. Feed water temperature control.
In some areas where they experience high feed water temperatures it may be necessary to use a heat
exchangerto cool the feed water. Where the feed water is cold it can be heated by mixing hot and cold
water with a thermostatic mixing valve.
2. Back flow preventer
All waterpre-treatmentsystemsrequire a form of backflow prevention device. This device prevents the
waterin the waterpre-treatmentsystemfromflowingbackintothe source watersupplysystem.It is very
important to each patient from backflow contamination, not just the source. If a backflow condition
occurs all the patients are at risk without protection at each device. Therefore backflow should be
considered also in the last stage of the system, where every in/out point should have a back-flow
preventer.
3. Multimedia depth filter
Large particulates of 10 microns or greater that cause the feed water to be turbid, such as dirt, silt,
colloidal matterare removed by a multimedia filter. Large particulates can clog the carbon and softener
tanks, destroy the RO pump, and foul the RO membrane.
The size of the multimediafilter shall be determined by a competent dialysis water pre-treatment plant
contractor or provider.
4. Water softener
Softenersworkonan ionexchange basis where calcium and magnesium are replaced with sodium. The
resin beads within the tank have a high affinity for the cations calcium and magnesium (both divalent)
present in the feed water and release two sodium ions (monovalent) for one calcium or magnesium
captured.
The High levels of calcium and magnesium in the feed water cause the water to be ‘hard’. Hardness is
measured in grains per gallon or mg/L and is generally expressed as CaCO 3 (calcium carbonate) for
uniformity purposes.
The Water hardness of both feed and product water should be less than 35 mg/L [2 grains per gallon
(gpg)]
5. Brine tank
The brine tank containssaltpelletsandwatertocreate the supersaturatedsaltsolutionusedfor softener
regeneration
6. Carbon tanks
Carbontanks are requiredtoremove chlorineadditivesfromthe feedwater.Chlorine and chloramine are
added to the city water supply for disinfection purposes.
7. Pre-filter
Pre-filters are particulate filters positioned after all the pre-treatment and immediately before the RO
pumpand RO membrane. Carbonfines,resin beads, and other debris exiting the pre-treatment destroy
the pump and foul the RO membrane. Typically, pre-filters range in pore size from 1 to 5 microns. Two
gauges monitor the inlet versus the outlet pressures across the filter. If the delta pressure increases by
eightovernewfilterpressuredifferential,the filter is clogged and needs replacement. Pre-filters [3] are
inexpensive insurance against damaging more expensive items downstream in the system. Therefore,
pre-filtersshall be changedonamonthlybasisbefore the pressuredifferential indicatesorearlierif a high
pressure differential indicates. Inspect the used filter’s center tube for soiling. If foreign material is
present,the filter was overburdened and shall be replaced sooner next time. All filter changes shall be
recorded in the Log Book.
8. Reverse osmosis(RO) pumpand motor
The RO pump increaseswaterpressure acrossthe ROmembrane toincrease bothproduct water flow and
rejection characteristics of the RO membrane. RO systems typically operate between 200-250 PSI. It is
important that RO pumps are made of high-grade stainless steel, inert plastics, and carbon graphite-
wetted parts. Brass, aluminum, and mixed metal pumps will leach contaminants into the water and are
not compatible with peracetic acid type disinfectants.
9. RO membranes
The reverse osmosis(RO) membraneisthe heartof the system. It produces the purified water through a
process of reverse osmosis, which is the opposite of osmosis. Osmosis is a naturally occurring
phenomenoninvolvingthe flow of water from a less concentrated compartment (e.g., non-salty side) to

the more concentratedcompartment(e.g.,saltyside) acrossasemi-permeable membrane to equilibrate
the two solutions. Inreverse osmosis, concentrated water is forced to flow in the opposite or unnatural
direction across a semipermeable membrane by means of high pressure. Natural osmotic flow is
overcome andpure waterpassesthroughthe membrane leaving the dissolved solids (salts, metals, etc.)
and other constituents behind on the concentrated side. Depending on the amount of product water
needed, the RO system will have one or more RO membranes.
RO membranes reject dissolved inorganic elements such as ions of metals, salts, and chemicals and
organicsincludingbacteria,endotoxins and viruses. Rejection of charged ionic particles ranges from 95-
99°/o, whereas contaminants such as organics that have no charge are rejected at a greater than 200
molecularweightcut-off. Ioniccontaminantsare highlyrejectedcomparedtoneutrally-chargedparticles,
and polyvalent ions are more readily rejected than monovalent ions.
RO membrane performance is measured by percent rejection, and final product water quality can be
measuredbyeitherconductivityinmicro-siemens/cmortotal dissolved solids (TDS) displayed as mg/L or
parts permillion(PPM). AAMI recommends both percent rejection and water quality monitors be used.
Theyshouldbe continuouslydisplayedwithaudible andvisual alarmswith set points that can be heard in
the patient care area.
10. RO systems
RO systemsmaybe a single central ROor individual ROsattachedtoeachdialysis machine. Many dialysis
unitswill require aCentral ROunitas well asseveral individual ROsformobile dialysismachinestoprovide
dialysise.g.inICU/CCU/privateroom etc. Central RO’s are useful for dialysis units with 6 chairs or more,
to reduce costs associated with maintenance and repair of individual ROs. Individual (single) ROs give
more flexibility and mobility, but require more maintenance and repair.
The Planningconsiderationforthe designand installation of a reverse osmosis (RO) water plant/reverse
osmosis (RO) system shall include;
 Choice of equipment for power and water efficiency/conservation.
 Consideration of installation designs that utilize water conservation, e.g. dual-pass reverse
osmosis RO) systems or the use of reject water in sterilizing departments or storage tanks for
irrigation or sanitation -flushing.
 The maximum water flow, including expected future growth in the number of patients to be
treated. Consider the maximum disinfection water flow.
 Average water flow per day also including expected future growth.
 Space required to safely install maintain and operate the RO water plant.
 Drainage required.
 The weight of the operational RO water plant and the ability of the -floor to safely support that
weight.
 Water quality monitoring systems.
 The capacity of the power supply for the RO water plant. Consider the disinfection mode
requirement.
 Facilities to safely service and maintain the central water plant (CWP).
 RO water distribution loop path, material, length and insulation requirements.
 RO water distribution loop outlet types, number of, consideration of spare and testing outlets.
11. DistributionSystem
As per [2], RO distribution systems can be grouped into two categories, direct feed and indirect feed.
- A direct feed system “directly”deliversthe productwaterfromthe RO unitto the loopfor distribution.
Unused product water can be recirculated back to the input of the RO unit for conservation reasons.
- An indirect feed system involves a storage tank that accumulates the product water and delivers it to
the distribution loop. Unused portions of the product water are recirculated back into the storage
tank.
Accordingto AAMI,storage tanksshouldbe made of inertmaterials that do not contaminate the purified
water,and the bottomsshouldbe conical shaped for complete emptying. The size of the tank should be
in proportion to meet the facilities peak demands, no larger.
12. Ultravioletirradiator (UV)
UV isa lowpressure mercuryvapourlampenclosedinaquartzsleeve thatisrequiredtoemitagermicidal
254 nmwavelengthandprovide adose of radiantenergyof 30 mW/cm2 inorder to kill bacteria. The UV

is able to penetrate the cell wall of the bacteria and alter the DNA to either kill it or render it unable to
replicate. It is possible for some species of bacteria to become resistant to UV irradiation.
Also,UV doesnot destroyendotoxin,anditmay evenincrease the level asaresultof the destructionif the
bacteria cell wall where endotoxins harbour. Therefore, UV should be followed, at some point, by
ultrafiltration. Biofilm,aprotective slime coatingthatbacteria secrete, will also reduce the effectiveness
of UV.
13. Submicron and ultrafiltration.
A submicronfilterreducesthe level of bacteriainthe final product water, whereas an ultrafilter removes
bothbacteriaand endotoxin.Sinceultrafiltershave tighterpores,theyinherentlyhave low flows and high
delta pressures across the membrane. They will decrease flow velocity in the loop if not designed and
staged properly. Alternatively, ultrafiltration gives added benefit and extra protection when placed at
points of use. Submicron and ultrafilters, even though they remove microbes, are targets for bacterial
infestation if not routinely disinfected or replaced. All submicron and ultrafilters shall be changed on a
monthly basis
14. Distributionpipingsystems.
 A continuous loop design is always recommended to eliminate the non-returning lines that go to
drain.
 Dead-ends or multiple branches shall not exist in the distribution system, as these are places for
bacteria biofilm to grow.
 Highlypurifiedwaterisveryaggressive and will leach metals and chemicals it comes in contact with.
Polyvinylchloride(PVC) isthe mostcommonpipingmaterial touse asitis low cost andhas a relatively
inert nature.
 No copper, brass, aluminum, or other toxic substances shall be used in the piping.
 The inner surface of the joint connections should be as smooth as possible to avoid microbiological
adhesion
 Flowvelocityshouldbe evaluatedquarterlyandthe loopvisuallyinspectedforincompatible materials
that may have been inadvertently added.
 Disinfection should always follow any invasive repair to the system.
Fig.3

Fig.4
Disinfection of the Distribution Piping Systems
Disinfection of the distribution piping system shall happen on a regular basis. The type of distribution piping
systemandthe disinfectionmethodtobe usedwill influence how oftendisinfection is carried out. There are two
types of disinfection methods;
1. Chemical disinfection.
When the manufacturer recommends chemical disinfectants, means shall be provided to restore the
equipmentandthe systeminwhichitisinstalledtoa safe conditionrelative to residual disinfectant prior
to the product water being used for dialysis applications. When recommending chemical disinfectants,
the chemical manufacturer shall also recommend methods for testing for residual levels of the
disinfectants.
2. Hot water disinfection
When used to control bacterial proliferation in water treatment, storage, and distribution systems, the
water heater of a hot water disinfection system shall be capable of delivering hot water at the
temperature andforthe exposure time specified by the manufacturer (minimum distribution loop temp
60’ C).
PVCpiping shall not be used with heat disinfection. However, PVDF, SS, PEX and PP piping can be used
with heat disinfection.
Heat disinfectionwill notremoveestablishedbiofilms,butisconvenient,requireslittle rinse time and can
thus be used more often to prevent biofilm formation
Moving to heat disinfection of storage and distribution pipework (rather than chemical) should be
considered in all new installations
Deionisers
Deionisersshouldnot now be used as part of a haemodialysis water pre-treatment system. Deionisers produce
waterof highionicquality,butdonotremove bacteriaandendotoxins. Infactbacteria and endotoxin levels may
increase requirement for ultrafilters, UV systems, etc. to ensure bacteria/endotoxins are removed. The risk of
operatingdeioniserstoexhaustionmaycause ionspreviouslyremovedto be re-released back into the water. An
accurate sensitive conductivity monitor is required to ensure appropriate warning of this. Deionisers may also
cause wide pH shifts to occur.
Water Quality standards in Dialysis Water Pre-Treatment System
Tables.2 show the maximumcontaminantconcentrationlevelsinthe dialysiswaterpre-treatmentsystemasper
ISO13959:2014 [5]

Table 2
Table 3 showsthe Contaminantremovedbyeachcomponentof the dialysiswaterpre-treatmentsystem
Table 3

Dialysis Water Pre-Treatment Plant Room
 Room Data sheet (RDS)
 General consideration [4]
 The Water Treatment Plant Room is a lockable room for water treatment systems used in
dialysis.
 The Water Treatment Plant Room should be located in close proximity to the Renal Dialysis
Unit to permit short tubing runs to each Treatment Bay, and permit staff to monitor and
service the water treatment systems.
 Special DesignRequirements:Ventilation, exhaust and/or air-conditioning must be designed
to accommodate the heat loads of the specified equipment.
 High level sound isolation is required to ensure noise generated from this room does not
invade Treatment spaces.
 Structural Engineer'sassessment must be sought for floor load bearing capacity with respect
to water treatment and pre-treatment plant equipment.
 Service access will be required around the perimeter of all plant equipment.
 Pipework and components installed after the water inlet within this room shall not contain
brass or copper.
 Space required
 The Space depends on the number of dialysis machine, which need to be fed / served with
treated water.
 As per [6], the first 10 Dialysis Station shall need a space of 18.6 m2
. A 0,465 m2
to be added
per each Dialysis Station greater than ten. This room accommodates the equipment and
supplies, including consumable products, for all dialysis-required forms of water treatment

 As per[7] a dialysisunitwith6DialysisStations/chairs/machinesshall need a space of 12 m2
,
12 DialysisStations/chairs/machines -15 m2
and with Dialysis Stations/chairs/ machines shall
need a space of 30 m2
 Hours of Operation and occupancy :
 24 Hours - YES
 1 – 2 persons
 ARCH:
 CEILING: plasterboard, water resistant, flush set, suspended, paint, washableFloor finish:
Material; Concrete, Finish.
 Min Height 2400mm; Water resistant drop in tile ceiling also acceptable.
 FLOOR FINISH: concrete, sealed, trowel
 SKIRTING:concrete,covedto150 AFFL,sealed
 WALL FINISH:paint,acrylic,washable
 DOOR: 1600mm c/o, 1 1/2 leaf,solidcore,paint – lockable
 Air : as recommendedbythe systemmanufacturer
 AIRCONDITIONING=Yes
 HEPA filtered=No
 Neutral pressure = yes
 EXHAUST: room exhaust=Yes
 VENTILATION =No
 Lighting: fluorescent,general=Yes
 Nurse Call : No
 ELECTRICAL: as recommendedbythe systemmanufacturer
 Emergency power,double,wall mounted outletsQTY=4, for use of handtoolsinthe room,
on a separate circuit
 Single ,Special Electrical power forequipmentpumps,asrequired
 Three phase power- 3 phase,accordingto Manufacturer'sspecifications
 Mechanical
 Hot & cold water= yes
 DRAIN:floorwaste - floorwaste mustbe capable of highflow ratesandhightemperature
water(upto 95 degreesC) fromthe ROWater Plant
 Room Plan (RP) – Fig.5

References
1. ANSI.AAMI/ISO13959:2009,AAMI, Arlington,Virginia2011
2. Layman-Amato,R.L.,Curtis,J.,& Payne,G.M.(2013). Water treatmentforhemodialysis:Anupdate.
NephrologyNursingJournal, September-October2013,Vol.40, No.5
3. ACIRenal Network,Waterfordialysis,A guide forin-centre,satellite andhome haemodialysisinNSW,
Version:V1.42016
4. Water TreatmentPlantRoom,roomdata sheet, Revision3,AustralasianHealthFacilityGuidelines2017
5. AustralianDrinkingWaterGuidelinesISO13959:2014
6. Space PlanningCriteria,PG-18-9,CHAPTER316: DIALYSIS CENTER, RevisedCriteria,Departmentof
Veterans Affairs,October03,2016.
7. 42. 0 Renal DialysisUnitwww.shcc.Ae PartB – Version1,2014 Page 378 42.2.2 Modelsof Care

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