18 WATER TREATMENT 18.1 Introduction
18.4 Maintenance and Quality Control .1 Control of Microbial Quality
a. System Disinfection (refer 18.3.2.a, 18.3.2.b and 18.3.2.c)
• The water treatment system should be designed to allow routine disinfection of the entire system, including the distribution system and the connections to the dialysis machine. The entire system should be disinfected at least once a month.
• To disinfect the RO membrane a separate clean disinfectant tank is usually needed. The RO should be disinfected separately. Disinfection times should be according to the disinfectant instruction for use and the membrane manufacturer’s instructions for use.
• Germicides for disinfecting water systems include Formaldehyde (2-3 %), Sodium Hypochlorite (500ppm) ,Peracetic Acid (2-3%), Hydrogen Peroxide, Ozone, Chlorine dioxide and Hot water (> 80oC)
• To disinfect the RO water distribution Loop, a separate chemical tank with pump facility should be used. The disinfectant is introduced post RO membrane at the permeate side, through to all supply outlets and diverted back to the chemical tank via the RO return loop, before it enters the water system. The disinfectant should be distributed to all lines and tested positive for presence of disinfectant. After the required dwell time, ensure removal of disinfectant from the system before use and verify with a test strip.
b. Frequency of microbial testing (refer 18.4.2.c)
For a newly installed water treatment system and distribution system, the microbial testing should be done at least once a week as part of the validation procedure for the disinfection programme.
After completion of the validation, microbial testing ideally should be carried out at least once a month. Testing must also be frequent enough to pick up changes in the trend.
c. Sampling location, timing and technique i). Daily test for chlorine
• Sampling location
o Pre R.O sampling valve.
• Technique
Colorimetric (Using HANNA Free Chlorine Test Kit) o Run the R.O system at least 10 to 15 minutes.
o Open the Free Chlorine Test kit and check for damage.
o Add 5 drops of reagent 1 and 3 drops of reagent 2 to the colour comparator cube.
o Fill the colour comparator cube with water sample from POINT A (See diagram 1)
o Replace the cap and mix by carefully swirling the cube in tight circles and inverting it several time.
o Determine which colour band best matches the solution in the vessel and record the results in mg/L (ppm) free chlorine.
(Refer figure 18.4.1.c.i)
ii). Daily test for hardness (Total Dissolve Solids)
• Sampling location
o Pre R.O sampling valve
• Technique
Using HANNA Hardness Kit
o Collect water sample from sampling point into a 50 ml plastic container supplied (See diagram 2 below).
o Add 5 drops of solution A.
o Add 1 drop of solution B.
o Titrate water with reagent supplied from a 1 ml syringe.
o Observed colour change from purple to blue while adding reagent from syringe drop by drop.
o Note volume of reagent used after the colour change.
o Calculate total hardness :
o Volume of titre x 30 = _________mg CaCO3
(Refer figure 18.4.1.c.i) iii). Monthly water analyses
• Water for microbial analyses
Samples shall be collected at a point where water enters the equipment or any point where product water is dispensed.
• Sampling Site
o Point A - Feed water (raw water)
o Point B - Pre treated water o Point C - R.O water
o Point D - First distribution point o Point E - Middle distribution point o Point F - Last distribution point
• Sampling technique (refer figure 18.4.1.c.iii) o Flush sampling valve for a few second.
o Swab sampling valve nozzle with 70% alcohol or povidone iodine.
o Flush sampling valve for another few second.
o Repeat step 2 and 3.
o Collect mid stream water from sampling valve into a sterile container.
o Samples shall be assayed within 30 minutes of collection or shall be immediately stored at 4-6 C and assay within 24 hours of collection.
iv). Six monthly Water Analysis (refer figure 18.4.1.c.iii)
• Chemical contaminants analyses
Collect sample from point C and send to analytical laboratory d. Technique of culturing water-borne microorganisms
i). Many factors influencing the detection and quantification of micro-organism
Factor Recommendations
Sampling place
Sampling hygiene
Sample storage
Sample size
Choice of culture medium
Conditions of incubation
Direct access to the stream to be sampled, avoidance of stagnant flow, flushing of the port
Cleaning of the sample port with a bactericidal agent, sterile sample tube etc.
Immediate storage of the sample at 4 C and plating of the samples within 24 hours ( to avoid additional growth)
Sufficient sample volume
Appropriate culture medium ( e.g. nutrient for Reasoner’s 2A agar or standard methods agar for water bacteria )
Appropriate length and temperature of incubation ( e.g. 24-28 C up to 7 days for water bacteria)
Proper sampling procedures involving sampling process, sample storage and transportation are all of importance.
• Implement aseptic conditions during sampling
o disinfect hands and sampling ports with disinfectants (alcohol swab/spray)
o do not use ports which cannot be properly disinfected or rinsed
o rinse tap ports with an adequate volume of sample medium prior to sampling.
• Samples must be transported/stored in sterile and pyrogen-free containers.
• Take an adequate sample volume: this is at least 10 ml for the determination of microbial counts and 3 ml for determining the endotoxin concentration.
• As microorganisms can continue to grow in samples it is necessary to cool samples in the fridge and analyze microbial counts within 24 hours. Endotoxin samples can be frozen and stored for a longer period of time.
• Standardize and document all procedures including:
o sampling technique
o sampling time points, e.g. on Monday/Saturday after a long shut-down period
o personnel responsible for sampling o sample storage and transport o methods for laboratory analysis o data interpretation and action protocol
• Document the cleaning and disinfection procedure for the water treatment and delivery system, as well as any changes made.
ii). Determination of colony forming units (CFU)
Viable microorganisms are assayed by three different methods with subsequent culturing on plates.
• Spread plate technique
0.1 to 1 ml of the aseptically collected sample are distributed over the surface of 15 ml dried culture agar on 9-10 cm culture plate with a sterile glass spreading rod. The plates are then incubated at 24 C for 7 days and colonies are counted at 48, 72 and 168 hours.
• Pour plate technique
1 ml of undiluted sample and samples in different dilutions are added to 10 ml of the appropriate medium agar and mixed. The agar
should be held at 43 C in a water bath before use. The sample/agar mixed is poured onto 9-10 cm culture plates and incubated under the same conditions as described for the spread plate technique.
Disadvantages of the method are that the organisms are submerged in the agar and the colonies tend to be smaller and do not show colony morphology characteristics. Recoveries of bacteria compared to the counts obtained with the spread plate method may, therefore, be decreased.
• Membrane filter method
Sample volumes greater than 1 ml is filtered through a sterile membrane with a pore size not greater than 0.45 µm and effective in retaining microorganisms. This filter is transferred under sterile conditions onto the appropriate culture medium on plates, whereby it should be ensured that the filter is not inverted. Nutrients diffuse through the filter so that colonies can grow on the filter surface.
iii). Media for culturing water/ dialysate samples
• Nutrient-poor agar
o Reasoner’s 2- Agar ( R2A) o Standard Method Agar ( SMA) o Tryptone Glucose Extract ( TGE)
• Sample incubation
o At lower temperature (24-28 C ) o Duration: 7 days
e. Measuring endotoxin levels i). Why
Endotoxin, or lipopolysaccharides, is essential components of the cell wall of gram negative bacteria, which when enters the patient’s blood stream it can cause pyrogenic reactions. It can be more important to test water and dialysis fluid for endotoxin than for bacteria as bacteria do not pass through intact dialyzer membrane readily.
The possibilities of dialysis patients exposed to greater levels of these microbial products has increased with the increase in reuse, the use of bicarbonate dialysis fluid and high flux dialysis. The consequence of microbial contamination besides acute pyrogenic reaction, is a state of chronic inflammation that may contribute to progressive inflammatory diseases in chronic renal failure such as
β2-microglobulin amyloidosis, protein catabolism, and accelerated atherosclerosis.
ii). How
Bacterial endotoxin levels should be monitored using the Limulus Amoebocyte Lysate (LAL) assay. The simplest form of LAL assay is the gel-clot test which can be performed in the dialysis unit, provided staff has received the necessary training.
In the gel-clot method, when a fluid sample containing ET is mixes with lysate from the blood of the horseshoe crab (Limulus polyphemus), a complex enzymatic reaction occurs. If sufficient ET is present, and the pH of the sample is 6 to 7.5, and there are no inhibiting substances, the solution will turn into a gelatinous clot.
It is necessary to run appropriate assay control samples. Chemical germicides with low pH (<6.0) or dialysate concentrates with high salt content will inhibit formation of gel clot and give false negative results. The procedure described by the particular LAL manufacturer must be followed exactly. Hands on training of personnel are important.
Other LAL tests include the colorimetric and turbidimetric assays.
iii). When
Dialysis fluid should be tested routinely for endotoxin to monitor the efficacy of the dialysis machine disinfection procedure. If the endotoxin levels in the dialysis fluid are significantly higher than in the water feeding the machine, the disinfection schedule or the method used should be modified. Dialysis fluid samples should also be tested if a patient experiences a pyrogenic reaction during dialysis. However the LAL assay will not detect all pyrogenic substances derived from bacteria.
18.4.2 Control of chemical quality a. Filter and resin maintenance i). Water softener
In typical water treatment configurations, a water softener removes calcium and magnesium by ion exchange from the feed water before it reaches the RO system. The excess calcium and magnesium in
"hard" water must be removed to prevent patient injury. However,
the primary practical reason for removing these ions is to prevent them from "plating" on the RO membranes, resulting in deterioration of performance.
The following risks are associated with the water softener:
• failure of the softener, resulting in high calcium or magnesium content in the water
• improper sizing or improper regeneration scheduling of the softener, resulting in increased hardness late in the cycle before regeneration; and
• regeneration of the water softener without bypass during treatment time, resulting in a large sodium concentration in the softener effluent stream and potentially causing severe patient injury or death due to hypernatremia
These risks can be minimized by the following monitoring and maintenance activities:
• Cheek the clock on the regeneration timer daily to ensure the proper setting. Record this information on the daily water treatment log sheet.
• Check the hardness of the water softener effluent daily before beginning dialysis.
• Confirm daily that there is an adequate supply of salt in the brine tank.
• Validate the appropriate sizing of and regeneration schedule for the softener by periodically checking the hardness of the water softener effluent at the end of the treatment day. Use only salt designed for water softeners.
ii). Carbon filtration
Granular activated carbon (GAC) is used in water treatment systems to remove chlorine, chloramines, and some organic substances.
While little has been published regarding the risks associated with organic materials in dialysis water supplies, the results of excessive chlorine or chloramines are well known. There are several literature reports of patient injury or death due to hemolysis when facilities did not adequately remove chloramines before initiating dialysis (FDA 1988). The AAMI -recommended maximum contaminant level for chloramine is 0.1 milligrams per liter (mg/L). Two tanks filled with granular activated carbon should be used in series. Each
of these tanks should have a minimum empty-bed contact time (EBCT) of 3 to 5 minutes.
The effluent of the first tank should be monitored before every patient shift to ensure that the chloramine content is below the AAMI standard level. If the level of chloramine exiting the first tank exceeds 0.1 mg/L, a sample should immediately be drawn from the water exiting the second tank. If that water meets the AAMI standard, dialysis can proceed; however, arrangements should be made to replace the first tank. If the chloramine level in the effluent of the second tank also exceeds 1 mg/L, that water must not be used for dialysis.
iii). Sediment filters
The sediment filter is usually placed just before the RO system to prevent dirt, suspended materials, pieces of water softener resin, carbon fines, or other matter from damaging or plugging the RO membranes.
Risks associated with sediment filters include algae growth in the filter housing and clogging of the filter, resulting in excessive pressure build up and filter failure and thus the flushing downstream of dirt and other debris trapped by the filter.
The risks associated with sediment filters can be minimized by the following design, maintenance, and surveillance practices:
• To prevent algae growth, use only opaque housings on sediment filters.
• Incorporate pressure gauges before and after all sediment filters, and monitor pressures at least daily. Whenever the pressure drop between the two gauges exceeds 10 pounds per square inch (psi) or the value recommended by the manufacturer, the filter should be changed. To prevent excess bacterial growth and to prophylactically guard against other contaminant build up, many manufacturers recommend that the filter be changed monthly even if the pressure drop does not exceed 10 psi.
iv). Reverse osmosis systems
Reverse osmosis systems use pressurized filtration (pressures capable of overcoming the osmotic pressure of solutes) to remove chemical contaminants at a rate of 95% to 99% and microbiological contaminants (bacteria, bacterial endotoxins, viruses) at a rate of
approximately 99%. The following risks are associated with the use of RO systems:
• membrane failure, allowing large amounts of chemical or microbiological contaminants to pass downstream,
• progressive membrane failure, resulting in either reduced flow rates or some passage of chemical contaminants; and,
• bacterial colonization, resulting in possible pyrogenic reactions or septicaemia.
These risks can be minimized by the following design, maintenance, and monitoring practices:
• Employ appropriate pre-treatment components to protect the RO system and optimize its performance (e.g., a water softener to remove excess calcium and magnesium, which would "scale"
on the RO membrane; carbon filtration to remove excess chlorine, which would also damage the RO membrane;
particulate filtration for removal of silt, which could clog the RO system; a temperature-blending valve to assure a feed-water temperature for optimum RO system performance).
• Equip the RO system with a continuous monitor for conductivity, which can be set to activate visible and audible alarms if the percent salt passage exceeds two times that validated when the membranes were initially installed. Such alarms indicate to the facility that cleaning or other service of the RO system may be necessary to maintain proper operation and cost-effectiveness. Such alarms also alert the dialysis staff to any massive failure of the system, which could result in a percent rejection level lower than that needed to produce
"chemically safe" water for hemodialysis. Performing a reduction ratio analysis on "worst-case" tap water will allow the dialysis staff to estimate that minimum percent rejection level.
• Periodically perform a quantitative analysis of the chemical contaminants listed in the AAMI standard (table 1).
• Monitor other RO system parameters daily, and document the results. Data on such parameters as pressure and flow rate are important in evaluating the safe and effective operation of the system. Whenever any significant change occurs in pressure or flow rate, the cause of the change should be determined and addressed.
© 1998 Association for the Advancement of Medical Instrumentation AAMI WQD
b Frequency of maintenance and testing i). Daily
• 15 minutes after starting R.O.
• Document in R.O. Water daily log sheet o Raw Water pump pressure (30-90 psi) o Guard filter in / out (diff. pressure < 15 psi) o Product water pressure (20-40 psi)
o RO filter pre / post (max. diff. 15 psi) o Product water flow rate.
o Reject water flow rate o Product conductivity
o Test hardness of post-softened water
o Test the chlorine/chloramines of the product water ii). Weekly Maintenance
• Multimedia Sand Column
Manual / Auto regeneration (backwash) 3x/week (Monday, Wednesday & Friday)*
• Carbon Column
Manual /Auto regeneration (backwash) 3x/week (Tuesday, Thursday
& Saturday)*
• Softener resin
Manual /Auto regeneration once per week (Sunday)*
• Municipality water
Frequency depends on pre and post pressure difference of column, chlorine and hardness test.
iii) Monthly
• Change guard filter if the pressure difference is more than 15 psi
• Change bacteria filter at the R.O. storage tank if pressure difference is more than 15 psi. Check the UV light at the R.O.
storage tank.
• R.O. water for bacteria culture and endotoxin level.*
iv). 3 Monthly
• Chemical wash of the R.O. membranes with Citric Acid and NaOH. (40gm in 10 liters of water)
v). 6 Monthly
• Inspection of the Raw water tank
o physical examination of the raw water tank o ball float valve
o presence of impurities in the water o cleaning of the tank if necessary
• Pre and post R.O. water for analysis inclusive of TBC and Endotoxins
o AAMI standards
• Disinfection of R.O. water distribution piping o peroxide base disinfectant – 3%
o formaldehyde – 4%
vi). Multimedia Sand Column
o change as recommended in the service manual o depending on the usage but usually once in 2-4 years.
vii). Carbon Column
o change as recommended in the service manual which is usually once in 2-4 years.
o indication: chlorine/chloramine test positive or traces after a few regeneration of carbon column for a few days.
viii). Softener Resin change as recommended in the service manual which is usually once in 2-4 years.
o Indication: hardness test positive after a few regeneration of softener resin for a few days.
c. Sampling location, timing and technique (refer 18.4.1.c)
18.5 Checklist
FDA- Recommended Features of Water Purification Systems Component/System Feature
Reverse osmosis
• A Total Dissolve Solids (TDS) indicator should be provided for product quality as well as percent rejection
• The TDS alarm should be temperature-compensated
• Whenever the product quality alarm is activated, there should be an audible and visible alarm and permeate flow should divert to drain.
• All water-contact materials should be appropriate for this use and should pass a leachables test.
Deionization
• A temperature-compensated, audible and visible alarm should be provided to indicate bed exhaustion.
• Ultrafilters or submicron filters should be provided on the product water output line for removal of bacteria and endotoxin.
• If used for primary purification, flow should divert to drain in the event of bed exhaustion, or an alarm should sound.
• Deionization should only be used when carbon filters are installed for pretreatment (to prevent formation of nitrosamines).
• All water-contact materials should be appropriate for this use and should pass a leachables test
Carbon filters
• There should be a 6-minute empty-bed contact time (EBCT) for chlorine removal and a 10-minute EBCT for chloramines removal.
• Two tanks should be installed in series (i.e.
worker/polisher configuration), and chlorine/chloramines should be monitored after every shift.
Water softeners • Regeneration lockouts should be included
Complete system
• Product water must meet all applicable industry and government standards and should pass a leachables test.
• Failure analysis of the complete system must demonstrate safe operation in the event of a single component failure.
• Each component of the system must be labeled with the name and address of the supplier.
• The user must be supplied with clear and adequate instructions for startup, monitoring, maintenance, and troubleshooting of the system.
WATER TREATMENT SYSTEM LOG
Mon Tue Wed Thu Fri Sat
DATE
VALVES OPEN Water Supply
Raw water tank inlet
Raw water pump inlet/outlet
Sand/Carbon/Softener
Guard filter inlet
SERVICE MODE / TIMER CHECK Multimedia Sand column
Softener resin Carbon column 1 Carbon column 2
Brine tank (adequate salt)
GAUGE READINGS Pressure pre multimedia sand
Pressure pre softener
Pressure pre carbon 1 Pressure pre carbon 2
Pressure Guard filter in
Pressure Guard filter out
Pressure Guard filter out