© ISO 2016 Washer disinfectors — Part 7 Requirements and tests for washer disinfectors employing chemical disinfection for non invasive, non critical thermolabile medical devices and healthcare equipm[.]
General
4.1.1 The WD shall conform to ISO 15883-1:2006+A1:2014 except for the following subclauses:
— 4.3.1 (which refers to thermal disinfection);
— 5.9 [process temperature control limits, excluding 5.9 d) and e)];
4.1.2 The WD shall be designed to clean and chemically disinfect the range of reusable items specified.
4.1.3 When necessary, the WD shall be provided with means to facilitate the correct alignment of the load in the washing chamber.
The volume of process chemicals admitted must be adjustable through a key, code, or tool, in accordance with ISO 15883-1:2006+A1:2014, sections 5.7.4 and 5.7.5 Additionally, the dosing system's accuracy should be within ±10% or as specified and verified for compliance, as outlined in section 6.6.
4.1.5 The automatic controller shall ensure that the final concentration of disinfectants are within the limits specified.
To confirm the concentration of disinfectant, it is essential to measure the volumes of both disinfectant and water used, along with obtaining a certificate of conformity from the supplier This certificate should verify the disinfectant's concentration and include supporting data regarding its shelf life and expiry date.
Cleaning
Cleaning must be evaluated according to ISO 15883-1 standards, utilizing the test soils and methods outlined in ISO/TS 15883-5 that correspond to the specific loads being processed.
During the washing stage, the process commences when the temperature at the control sensor of the washing device (WD) reaches the specified washing temperature The washing temperature range is defined with a lower limit set at the specified washing temperature and an upper limit not exceeding the specified washing temperature plus 10 °C, in accordance with ISO 15883-1:2006+A1:2014, section 4.2.3.
4.2.3 Cleaning efficacy shall be determined in accordance with 6.7.
When designing a washing device (WD) for the reuse of cleaning solutions across multiple operating cycles, it is crucial to maintain the efficacy and safety of the solution This involves implementing specified methods to ensure the cleaning solution retains its required effectiveness, based on validation studies typically conducted by the manufacturer Key parameters to monitor may include the concentration of active ingredients and other factors, such as pH, that can influence performance.
Minor adjustments in the formulation of a cleaning solution can greatly impact its stability and cleaning effectiveness Users should be provided with recommendations regarding the maximum duration or number of operating cycles for which the cleaning solution is effective, based on validated experimental data If these validated usage conditions are surpassed, the automatic controller must take appropriate action.
— operate an audible and visible alarm and prevent the use of the operating cycle until the cleaning solution is changed, or
— effect an automatic change of the cleaning solution in the WD.
Disinfection
4.3.1 The cycle shall include a chemical disinfection stage, which may be combined with the cleaning and shall be deemed to have been achieved when testing requirements in 6.8 are met.
The requirements and tests outlined in section 4.3.2 of ISO 15883 focus on the use of aqueous disinfectant solutions, while also allowing for systems utilizing gaseous disinfectants, which must undergo equivalent testing It is essential that the disinfectants employed have demonstrated in vitro efficacy in accordance with relevant published standards.
For efficacy testing, a validated neutralization method provided by the disinfectant manufacturer must be utilized When evaluated on surfaces, the disinfectant must show effectiveness at the minimum exposure time, minimum concentration, and minimum temperature specified for use in the WD.
1) at least a 5 log10 inactivation of vegetative bacteria;
2) at least a 4 log10 inactivation of yeast-like fungi;
3) at least a 4 log10 inactivation of enveloped viruses.
NOTE 2 National Regulatory Authorities can require higher inactivation values and/or efficacy against a wider range of microorganisms.
Efficacy tests for disinfectants against vegetative bacteria may not account for mycobacteria It is essential to indicate the compatibility of cleaning and disinfection solutions, particularly regarding how the carryover of cleaning agents may affect disinfection efficacy Additionally, the experimental conditions for in vitro tests demonstrating the microbicidal efficacy of disinfectants must mirror actual usage conditions Therefore, when cleaning and disinfection are performed together, the disinfectant should be evaluated in the presence of relevant interfering substances, including typical soiling found in the materials being processed.
During the disinfection stage, it is essential to monitor the temperature of the disinfectant solution to ensure it stays within the specified limits This temperature must also be compatible with the device(s) being processed.
To ensure effective disinfection, it is essential to either regulate the temperature of the disinfectant solution or prevent the operation of the washing device (WD) when the temperature is outside the specified disinfectant range.
When designing a washer-disinfector (WD) for the reuse of disinfectant solution across multiple operating cycles, it is crucial to maintain the efficacy and safety of the solution This involves implementing measures to ensure that the disinfectant retains its required antimicrobial disinfection efficacy, which should be supported by validation studies typically conducted by the disinfectant manufacturer These studies help identify suitable parameters or indicators, such as the concentration of active ingredients and factors like pH and stability, that can be monitored to assess the antimicrobial effectiveness of the disinfectant solution.
Minor adjustments in the formulation of disinfectants can significantly impact their storage life and antimicrobial effectiveness Users should be informed of the maximum usage period or number of operating cycles for the disinfectant, based on validated experimental data If these validated conditions are exceeded, the automatic controller must alert users with audible or visible signals and prevent further use until the disinfectant solution is replaced Additionally, a method should be provided for users to monitor the disinfectant's concentration, such as a chemical indicator, to ensure it meets or exceeds the minimum recommended levels.
NOTE 2 The minimum recommended concentration is the lowest concentration of active and other ingredients to meet the label claim of a reusable disinfectant.
Final rinsing
The water quality used for rinsing after the disinfection stage shall not impair the result of cleaning/disinfection when tested in accordance with 6.3.
NOTE WHO definition for potable water or National Regulatory Authorities can be considered.
Self-disinfection
A self-disinfection cycle must be implemented to prevent the washer-disinfector (WD) from becoming a source of contamination for the load This cycle also serves to disinfect the WD following maintenance, repairs, or testing, in accordance with ISO 15883-1:2006+A1:2014, section 5.3.1.2.
The self-disinfection process addresses contamination issues in water delivery systems, particularly where biofilm can form in rinse water pipes This biofilm harbors microorganisms that exhibit high resistance to disinfection methods.
Thermal disinfection shall attain a minimum A 0 of 60 and shall be capable to be set to give an
If the use of thermal disinfection is not possible, a chemical disinfectant different from that used for disinfecting the loads shall be used.
NOTE 2 The use of a disinfectant based on the same active ingredients can carry the risk of allowing organisms resistant to a particular disinfectant to proliferate.
4.5.2 Details of the parts of the WD subjected to the self-disinfection cycle shall be provided and whether this cycle includes other components such as the water treatment equipment.
The WD self-disinfection cycle must be controlled by an automatic controller and be user-selectable It should effectively disinfect the chamber and all liquid transport systems Additionally, the system must alert users to operate the WD without any load in the chamber and, where feasible, verify that no devices are present before initiating the cycle In cases of thermal self-disinfection, it is essential that all components of the heating system and associated pipework reach the required temperature to ensure effective disinfection.
4.5.4 The self-disinfection cycle shall ensure that contamination through failure of the water treatment equipment can be effectively disinfected Compliance shall be verified by testing in accordance with 6.8.3.
Thermal disinfection systems must undergo evaluation through thermometric monitoring, utilizing sensors positioned at key areas that reflect the lowest temperatures within the system It is essential that the entire system reaches the necessary disinfection temperature to ensure effective thermal disinfection.
For chemical self-disinfection cycles, a microbiological test is necessary The effectiveness of the WD in achieving self-disinfection is confirmed through testing as outlined in Annex B.
Drying
4.6.1 The WD shall, unless otherwise specified, be provided with equipment to allow drying of the load.
4.6.2 Drying of the load in the WD shall be deemed to have been achieved when plain surfaces of the items are visibly dry (see 6.4).
Water treatment equipment
General
To ensure optimal performance, it is essential that all water treatment equipment, including softeners, de-ionizers, and filters, operates within the specified limits for flow rates and supply pressures.
Disinfection of water treatment equipment
4.7.2.1 When the water treatment equipment is a part of the WD, the former shall be designed and constructed to allow for periodic disinfection Guidance on the minimum frequency that the equipment is disinfected shall be provided in accordance with the information supplied by the purchaser for the quality of the water supply and the water treatment equipment [see 8 c) and h)].
NOTE The disinfection of the water treatment equipment can be carried out during a self-disinfection cycle.
The user should determine the appropriate frequency based on recognized seasonal variations in water quality and the operational history of the water treatment equipment.
The disinfection method shall not cause any damage to, nor impair the efficacy of, the treatment equipment.
The effectiveness of the water equipment disinfection process is confirmed if testing, as outlined in section 6.3, shows fewer than 10 CFU in each of two 100 ml samples, while also meeting other control parameters such as temperature and holding time.
4.7.2.2 If the water treatment equipment is not part of the WD, the requirements for water supplied to the WD shall be specified This shall include specification of the permissible microbial contamination of the water supply [see 8 i)].
NOTE 1 To meet the specification of the permissible microbial contamination of the water supply, it can be necessary for the user to make provision for disinfection of the external water treatment equipment.
Final rinse water shall have less than 10 CFU/100 ml sample (see 6.3) If required, means shall be provided to disinfect water used for the final rinse.
NOTE 2 The following methods can be suitable for control of the microbial contamination of rinse water:
— maintained in a dedicated reservoir at a temperature not less than 65 °C for the time demonstrated to achieve disinfection of the incoming supply;
— disinfected immediately prior to use;
— filtered to remove suspended particles of a size greater than 0,2 μm;
— sterile, in a closed container, with a connection to the WD designed and constructed to provide aseptic transfer.
4.7.2.3 The connection between the water supply, which has been treated to remove microbial contamination and the circulation system for rinsing, shall be designed and constructed to provide aseptic transfer.
Provision shall be made for disinfection of this connection to be made periodically The frequency and method of carrying out this disinfection shall be specified.
4.7.2.4 When the water treatment equipment is a part of the WD, from the time before the rinsing stage until the end of the processing cycle, as appropriate, the final water treatment used to fulfil the requirements of 4.4 shall be monitored by the WD automatic controller to verify that the parameters affecting the efficacy of the water treatment equipment remain within specification.
Maintenance of piping
The planned preventive maintenance required for the piping that is part of the WD and is used to convey final rinse water to the load shall be specified.
Materials — Design, manufacture, and assembly
5.1.1 The WD should be constructed so that loading and unloading of medical equipment are possible without the need to enter the chamber.
5.1.2 The WD design should consider the ease of access for maintenance (IEC 61010-2-040:2005, 5.4.3 and 7.5).
Process verification
The WDs shall be equipped with a level b process verification system (see ISO 15883-1:2006+A1:2014, 5.11.4.
General
The tests outlined in this section are supplementary to those in ISO 15883-1 and are specifically designed for washer-disinfectors (WDs) that process non-invasive, non-critical thermolabile medical devices and healthcare equipment These reference tests serve to demonstrate compliance with the requirements of this part of ISO 15883 and can be utilized in type tests, works tests, validation, re-qualification tests, or routine tests conducted by or on behalf of the user Alternative tests and methods that provide equivalent assurance may also be used to claim compliance In the event of a dispute, the reference tests specified in this part of ISO 15883 will take precedence.
The summary of additional tests beyond those specified in ISO 15883-1 is detailed in Annex A It is important to note that several of these tests can be conducted concurrently with each other and/or alongside the tests mandated by relevant safety standards, such as IEC 61010-2-040.
Test load
Loading with standard goods
Test load shall be defined to represent typical loading of goods to be processed such as bedsteads and bedside tables.
Loading with special goods
If non-critical, non-invasive medical devices that were not included in the type test are to be processed, then a performance qualification shall be carried out with representative loads.
Water used for rinsing following disinfection
Water used for final rinsing shall be collected from within the WD chamber and tested for microbial quality in accordance with Annex C.
Where the final rinse water is collected after contact with the load, a neutralisation method shall be used to eliminate any antimicrobial activity.
Testing will be conducted after installation and will continue weekly until the final rinse water consistently meets specifications for a minimum of one month Following this period, testing will be performed annually.
NOTE Tests for other microorganisms that can be of clinical significance (e.g Acinetobacter) can be performed.
Load dryness
General
When the WD is intended to dry the load, testing shall be carried out as described below.
Procedure
The washing machine will be operated according to the manufacturer's guidelines, ensuring it undergoes a full cycle that includes the drying phase Once the cycle is finished, the door will be opened and left ajar for 5 minutes before the load is taken out A visual inspection will be conducted to assess the dryness of the load.
Results
Report whether or not plain surfaces of the load are free visible water.
Thermometric tests
General
The tests shall be performed in accordance with ISO 15883-1:2006+A1:2014, 6.8.
Load temperature test
The load temperature test must utilize reference loads consisting of the full range of items that the WD is designed to handle It is essential to select items that possess the greatest mass, highest specific heat, and lowest thermal conductivity for accurate testing.
Chemical dosing tests
General
The tests shall be performed in accordance with ISO 15883-1:2006+A1:2014, 6.9.
Reused process chemicals
For a washer-disinfector (WD) intended to reuse a detergent or disinfectant solution, it is essential that the solution meets the minimum effective concentration before the final permitted cycle The concentration of the chemicals must be determined using the specified method for the process chemicals, and it is important to document whether these requirements are met.
Tests of cleaning efficacy
General
The conditions of use of cleaning solutions within the WD shall be within the conditions validated and specified as acceptable.
Cleaning solution tests must be performed at the end of their shelf life or under simulated end conditions, following the worst-case recommended storage guidelines.
The testing procedure and loads are structured to ensure adherence to the cleaning efficacy standards outlined in ISO 15883-1:2006+A1:2014, section 6.10 This approach also considers the specific characteristics of the loads and, when relevant, the integration of cleaning and disinfection processes in a single stage.
The assessment of cleaning effectiveness should focus solely on the specified cleaning stage To assert that certain loads can be processed in the washing device (WD), it is essential to provide data demonstrating that these loads can be thoroughly cleaned within the WD.
Materials
The load carrier chosen for the test load shall be of the type recommended for the devices to be processed (see 6.2).
The type test shall be carried out using the loads described in 6.2.
Devices to constitute a test load shall be contaminated with one or more test soils by the method given in ISO/TS 15883-5 that are pertinent to the load being processed.
NOTE 1 Local requirements can specify the use of particular test soils and methods.
NOTE 2 The attention of manufacturers is drawn to the user’s choice of test soils(s) and method(s) for operational testing; this can indicate a need to carry out similar testing before the WD is supplied.
The test soils utilized for the load, chamber wall, and load carriers can either be identical or varied If different test soils are employed, it is essential to document the reasoning behind the selection of each test soil.
Testing of the cleaning solution must be conducted using water at the maximum permitted hardness if its effectiveness may be compromised by dilution with harder water.
Procedure
To evaluate the cleaning efficacy, place the test load contaminated with test soil in the chamber and initiate a normal cleaning cycle for the specified load type Interrupt the cycle after the cleaning stage, or just before the disinfection stage if applicable A rinse with water may be included post-cleaning if specified in the cycle For cycles that combine cleaning and disinfection, halt the process after this stage and any rinse Visually inspect the test load and utilize methods outlined in ISO/TS 15883-5 to check for residual soil Additionally, confirm the presence of residual soil using qualitative or semi-quantitative methods from ISO 15883-1:2006+A1:2014, Annex C.
Results
Ensure the cleaning process is adequately documented by following the criteria outlined for the specific test soil in ISO/TS 15883-5, along with the detection results obtained from the method specified in ISO 15883-1:2006/Amd 1:2014, Annex C.
Test of disinfection efficacy
General
The conditions of use of disinfectant(s) in the WD shall be within the validated and specified conditions.
Disinfectant testing must occur at the end of its shelf life or under simulated end conditions, ensuring that the product has been stored in the most adverse storage scenarios.
National regulations may mandate specific approval processes for disinfectants used in washing devices (WDs) for medical devices Adhering to these national requirements is essential within the applicable jurisdiction.
Preliminary tests on chemical disinfectants
A series of initial tests will be conducted to confirm the in vitro microbicidal efficacy of the disinfectant solution, following the conditions outlined in section 4.3 These tests will replicate the conditions used during the disinfection phase of the cycle, unless sufficient data for shorter contact times under relevant conditions is available.
For this, the microbicidal efficacy of the disinfectant solution shall be verified.
During these tests, experimental conditions intended to simulate the conditions within the WD shall be used.
The disinfectant shall be tested at the minimum concentration available during the disinfection phase of the cycle, based on the minimum recommended concentration (MRC).
Each disinfectant recommended for use in the WD shall be tested.
In the case where it is intended that a disinfectant solution be reused, the efficacy of the solution shall be determined as a function of its minimum effective concentration (MEC) (see 4.3.4).
In the disinfection process, two scenarios must be addressed: (a) when disinfection occurs under uncontrolled temperature conditions, the testing temperature should reflect both the minimum and maximum temperatures allowed during the disinfection cycle; (b) when disinfection is conducted under controlled temperature conditions, the testing temperature must align with the specified lower and upper limits of the disinfection temperature.
The contact time observed during the tests shall be the minimum duration of the disinfection stage.
When the effectiveness of a disinfectant may be compromised by dilution with water that exceeds a specific hardness level, it is essential to conduct tests using the disinfectant diluted with water at the maximum allowable hardness.
Before evaluating the effectiveness of a disinfectant, it is essential to demonstrate and document a method for neutralizing the disinfectant at the end of the exposure period This includes ensuring that neither the neutralizing agent nor any byproducts formed with the disinfectant are microbicidal or inhibit the growth of the test organism Additionally, when using a secondary host, such as a cell culture, to detect the survival of test organisms, it must be shown that there are no carryover effects on the cell culture system and that low numbers of test organisms can be accurately detected when introduced as a challenge to the test system.
Test organisms shall be selected on the basis of antimicrobial claims made with the WD, with consideration of 4.3.
NOTE Guidance on choice of organisms can be obtained from relevant published method standards or generally accepted national guidelines on surface disinfectant efficacy testing, e.g EN 13624, EN 13727,
EN 14348, EN 14476, AOAC International (2012), RKI/DVV guideline (2008).
Initial potency tests can utilize a suspension of test organisms; however, it is essential to demonstrate efficacy on contaminated surfaces The surfaces of the test pieces inoculated with test organisms must accurately represent those found in the WD chamber and the devices being processed.
The validation of the culture method is essential for accurately counting the surviving microorganisms after disinfectant exposure This method must effectively recover a low quantity, approximately 10, of the specific organisms it is designed to detect.
Self-disinfection tests
The testing method must estimate the bacterial levels in the final rinse water after a standard operating cycle, which includes a self-disinfection phase (refer to Annex C).
In addition, thermometric verification of A0 attainment shall be performed for thermal self-disinfection cycles in accordance with ISO 15883-1:2006+A1:2014, 6.8.
The test method used shall estimate the bacterial levels in the final rinse water at the end of a normal operating cycle following the self-disinfection cycle (see Annex C).
The final rinse water test is adequate for confirming the self-disinfection cycle, and samples should be collected from a suitable location that guarantees the water has circulated through the disinfected components.
Chemical disinfection of the load
The test shall be carried out in accordance with Annex D.
The test method shall use a load in accordance with 6.2, with specific load examples given in Annex E.
A range of other microorganisms can be used in combination with a soil relevant to the load from ISO/TS 15883-5.
NOTE A particular test organism is suggested but others can be used at the request of the user.
Mechanical removal alone (i.e wash-off) shall be evaluated in the absence of the disinfectant.
6.8.4.2 Operational and performance qualification tests
Operational and performance tests shall establish the levels of all controlling variables that affect the disinfection of the load are within the limits established during type testing.
When national regulations necessitate, specified test loads may be employed to replicate various load items To assess the effectiveness of the disinfection process, methods such as direct inoculation of test organisms, biological indicators, or bioburden testing (ISO 11737-1) can be utilized Additionally, microorganisms mixed into test soils can serve as alternatives or supplements to inoculated test objects, as outlined in ISO/TS 15883-5.
Routine tests shall establish the levels of all controlling variables that affect the disinfection of the load are within the limits established during type testing.
Documentation shall be in accordance with ISO 15883-1:2006/Amd 1:2014, Clause 7.
8 Information to be provided by the manufacturer
In accordance with ISO 15883-1:2006/Amd 1:2014, Clause 8, additional information must be provided, including the available range of load supports, details on which parts of the washer-disinfector (WD) undergo disinfection, and guidance on the disinfection frequency for water treatment equipment It is essential to specify the locations of temperature sensors that represent the system's lowest temperature, as well as the detergents and disinfectants used in type testing Users should receive recommendations on the maximum usage period for reusable detergents and disinfectants, along with the range of antimicrobial activity they possess A method for monitoring disinfectant levels, such as a chemical indicator, should be included to ensure effectiveness Additionally, the maximum time required for the WD to be operational at minimum utilities must be stated, along with requirements for water supplied if the water treatment equipment is not integrated into the WD.
WD including the requirement to control the microbial contamination of the water supply (see 4.7).
The WD shall be marked externally in accordance with the requirements of IEC 61010-2-040:2005, Clause 5.
10 Information to be requested from the purchaser by the manufacturer
The requirements of ISO 15883-1:2006+A1:2014, Clause 10 apply.
Annex A (normative) Summary of test programmes
Table A.1 — Summary of tests in addition to ISO 15883-1:2006/Amd 1:2014
Brief description of test Requirement
Clause Test Clause Type test Work s test OQ PQ Routine test
Accuracy of the dosing system 4.1.4 6.6 X X X B X (Q)
Accuracy and repeatability in accordance with ISO 15883-1:2006 +A1:2014, 5.7.5 in accordance with
Low level indicator in accordance with ISO 15883-1:2006 +A1:2014, 5.7.6 in accordance with
Legibility in accordance with ISO 15883-1:2006 +A1:2014, 5.12.3 in accordance with
Calibration in accordance with ISO 15883-1:2006 +A1:2014, 5.11, 5.12.4, 5.13, 5.14 and 5.15 in accordance with
O optional test which can be requested by the purchaser or user
V verification of calibration at the value(s) of interest for the particular instrument, e.g the disinfection temperature
Q quarterly test interval, Y yearly test interval, D daily test interval
Brief description of test Requirement
Clause Test Clause Type test Work s test OQ PQ Routine test
Fault indication in accordance with ISO 15883-1:2006 +A1:2014, 5.22.1 and 5.4.1.5 in accordance with
O optional test which can be requested by the purchaser or user
V verification of calibration at the value(s) of interest for the particular instrument, e.g the disinfection temperature
Q quarterly test interval, Y yearly test interval, D daily test interval
The tests included in Table A.1 assume that all necessary installation qualification checks and tests have been completed satisfactorily.
Optional tests may be carried out at the discretion of the purchaser/user or can be required by local regulation.
Suggested test intervals are for guidance only Routine testing programs should be established based on a risk analysis that considers the conditions and reliability of the WD, the level of independent monitoring for each cycle, and the intended use of the WD.
Methods for microbiological evaluation of disinfection of liquid transport system
This article outlines two methods designed to simulate potential incidents that may occur during the normal use of the WD, which could lead to contamination (refer to sections 4.7.2 and 6.3).
Method 1, outlined in section B.5.2.1, evaluates the self-disinfection cycle following a simulated failure of the internal water treatment system Despite prompt repairs within 24 hours, this malfunction leads to contamination of the water distribution (WD) system by microorganisms from the supply water.
Method 2 (B.5.2.2) simulates WD contamination by microorganisms from supply water due to a malfunction in internal water treatment equipment In this scenario, the self-disinfection cycle is initiated one week post-malfunction, during which the WD is used daily for one load of washing/disinfection This approach enables the assessment of the self-disinfection cycle's effectiveness on a potentially contaminated WD after a week of continued use.
Monitoring the internal contamination levels of the water distribution (WD) system during the period between equipment failure and the self-disinfection cycle is crucial This evaluation helps determine the effectiveness of the WD's design in preventing microorganism growth within the pipes.
B.2.2 Pseudomonas aeruginosa (for example, ATCC 15442 1) or equivalent) as microorganism.
B.2.3 Bacterial suspension, with 1 CFU/ml × 10 9 CFU/ml to 1 CFU/ml × 10 10 CFU/ml in sterile distilled water.
B.2.4 Tryptone soya agar (TSA), as maintenance and counting medium (see EN 13727).
The following cycles shall be available:
1) ATTC American Type Culture Collection, 10801 University Boulevard, Manassas, VA 20110-2209, USA, www. attc.org The ATCC number is the collection numbers of strains supplied by these culture collections This information is given for the convenience of users of this International Standard and does not constitute an endorsement by ISO of the product named.
The sampling cycle should align with the regular cleaning and disinfection process, pausing before disinfection to replace the detergent with sterile distilled water After this interruption, a sample must be collected from the bottom of the tank, which contains water that has circulated through the WD's piping system.
NOTE This sampling programme only includes the cleaning and rinsing phase and circulates water throughout the WD’s pipe work, without there being any addition of disinfectant or detergent product.
In cases where the cycle cannot be halted just before the disinfection stage, it is essential to conduct a complete cycle using sterile purified water, such as reverse osmosis, in place of all process chemical solutions to prevent contamination.
This special programme corresponds to a routine cleaning and disinfection cycle for which
— the disinfectant solution heating system (if fitted) is deactivated, and
— the detergent and disinfectant are replaced by sterile distilled water.
During the contamination cycle, the WD is linked to an external tank that holds the contamination solution, ensuring that throughout each phase, the WD exclusively receives the solution from this external source.
B.4 Connection of the WD to the external tank
The connection of the WD to the external tank shall be as shown in Figure B.1.
NOTE As a function of manufacturer’s recommendations, external peripherals can be inserted between the water supply network and the WD (water softener, etc.).
Figure B.1 — Connection of the WD to the external tank — Test configuration
Before each test, subject the external tank in which the contamination solution is prepared to a thermal disinfection cycle with an A0 of not less than 600.
B.5.1.2 Verification of absence of microbiocidal residue in the external tank after disinfection
During the last rinsing stage of the external tank, collect 9 ml of the water circulating in the external tank and associated pipework.
Incorporate 1 ml of a bacterial suspension of Pseudomonas aeruginosa at 10 3 bacteria/ml in the previously sampled 9 ml of water.
After mixing thoroughly and 10 min of contact time, establish the number of viable bacteria present in the reaction mixture, TN, by serial dilution and counting on a TSA agar plate.
The rinsing is only considered to be valid if [see Formula (B.1)]
TN is the number of viable bacteria present in the reaction mixture;
T t is the exact concentration of bacteria in the bacterial suspension (control).
B.5.1.3 Preparation of the contamination solution
Fill the external tank with 30 l of tap water and 30 ml of a Pseudomonas aeruginosa suspension containing
10 9 CFU/ml After thorough mixing, take a sample in order to establish, by serial dilution and counting on a TSA agar plate, the exact concentration of microorganisms in the contamination solution.
B.5.1.4 Contamination of the WD via the water supply network
To initiate the contamination testing, first prepare the contamination solution and deactivate the WD water treatment unit Next, connect the WD being tested to the external tank (refer to Figure B.1) and commence the WD contamination cycle to ensure that the contamination solution circulates through all internal piping of the WD.
B.5.1.5 Determination of the WD contamination level
To assess the contamination level of the water distribution (WD) system, conduct a sampling cycle to measure the concentration of microorganisms in the water that has circulated through the piping During this cycle, collect 2 liters of water from the WD tank and filter 10 ml, 100 ml, and 1,000 ml of this water using 0.2 μm membranes After filtration, rinse the membranes with 3 ml to 50 ml of sterile distilled water, place them on a counting medium, and incubate to analyze the results.
After incubation, count and identify the number of colony forming units and express the results as a number of colony forming units per 100 ml.
B.5.2 Establishment of the efficacy of the disinfection of the liquid transport system
To ensure effective water disinfection, begin by installing the water disinfection (WD) system and running a self-disinfection cycle followed by a sampling cycle to assess contamination levels Next, deactivate the water treatment system by removing the filter and deactivating the heating system, then disinfect the external tank Prepare a contamination solution and introduce it into the WD through the water supply network Allow the WD to incubate at room temperature (minimum 20 °C) for 24 hours before reconnecting it and reactivating the water treatment system After reactivation, conduct another self-disinfection cycle and a sampling cycle to evaluate contamination levels according to B.5.1.5 If the results indicate more than 10 CFU/100 ml, repeat the self-disinfection and sampling steps until contamination is reduced to 10 CFU/100 ml or less, and document the number of cycles required for this reduction.
It is not essential to assess the contamination level prior to the disinfection cycle, as the degree of contamination is specific to the design of the WD liquid transport system Additionally, sampling may inadvertently eliminate considerable microbial contamination from the system.