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7/17/2019 Guidance Notes on Code of Practice for Water-cooled Air Conditioning Systems
http://slidepdf.com/reader/full/guidance-notes-on-code-of-practice-for-water-cooled-air-conditioning-systems 1/22
EMSD
Guidance Notes on Code ofPractice for Water-cooled AirConditioning Systems
(November 2011)
7/17/2019 Guidance Notes on Code of Practice for Water-cooled Air Conditioning Systems
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7/17/2019 Guidance Notes on Code of Practice for Water-cooled Air Conditioning Systems
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Electrical & Mechanical Services Department Guidance Notes on Code of Practice forWater-cooled Air conditioning Systems
Contents
1 Guidance Notes 1
Part A
1.1 Minimum Horizontal Separation Distance for Cooling Towers 1
1.2 Cooling Tower Installation Location (Pedestrian Thoroughfare) 4
1.3 Cooling Tower Installation Location (Extended Ductwork) 6
1.4 Cooling Tower Installed on Roof and Affecting the Adjacent Buildings 8
1.5 Cooling Tower Installed on Podium Roof 10
1.6 Cooling Tower Installed at Indoor with Vertical Discharge through Roof or
Horizontal Discharge through Side Wall 14Part B
1.7 Control of Bacterial Growth 16
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Electrical & Mechanical Services Department Guidance Notes on Code of Practice forWater-cooled Air conditioning Systems
Figures
Figure 1: Enquiries on measuring point in determining the minimum separation distance 1
Figure 2: Measuring point shall not be from the center of the cooling tower 2
Figure 3: Measuring point shall be from the nearest edge of the cooling tower exhaust / intake 2
Figure 4: Separation distance shall not be the sum of horizontal and vertical distance 2
Figure 5: Horizontal distance shall be considered separately from the vertical distance 2
Figure 6: Measuring point shall not be the directional distance as the separation distance 3
Figure 7: Measuring point shall be from the nearest edge of the cooling tower exhaust to thefaçade horizontally 3
Figure 8: Separation distance shall not be the sum of horizontal and vertical distance 3
Figure 9: Horizontal distance shall be considered separately from the vertical distance 3
Figure 10: Measuring point shall not be from the centre of the louvre 3
Figure 11: Measuring point shall be from the nearest edge of the exhaust / intake louvre 3Figure 12: Separation between the cooling tower exhaust and pedestrian thoroughfare 4
Figure 13: Provide overhead cover above the walkway 5
Figure 14: Install discharge hood to re-direct the exhaust air away from the walkway 5
Figure 15: Cooling tower installed inside building with extended ductwork for discharge from
facade louvre 6
Figure 16: Locked window and blank-off louvre on the same facade surface within the restrictedzone 7
Figure 17: Cooling tower installed on roof surrounding by adjacent buildings 8
Figure 18: Horizontal separation requirement for cooling tower and the adjacent buildings 9
Figure 19: Cooling tower installed on podium roof 10
Figure 20: Horizontal separation requirement for cooling tower installation on podium roof 11
Figure 21: Vertical separation requirement between podium roof cooling tower and building’s airintake and operable window below podium roof 12
Figure 22: Vertical separation requirement between podium roof cooling tower and building’sexhaust air outlet below podium roof 12
Figure 23: Horizontal separation requirement between podium roof cooling tower intake and building’s exhaust air outlet on podium roof 13
Figure 24: Horizontal separation requirement between podium roof / roof cooling tower andlouvres on building façade 13
Figure 25: Cooling Tower installed in plant room with vertical discharge through roof andhorizontal intake through side wall 14
Figure 26: Separation requirement between intake lourve / exhaust outlet of indoor cooling towerand the adjacent building air opening 15
Figure 27: Flowchart for Control Strategies for the presence of Legionellae 17
Figure 28: Flow Chart for Control Strategies for the presence of heterotrophic microorganism 18
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1
Electrical & Mechanical Services Department Guidance Notes on Code of Practice forWater-cooled Air conditioning Systems
Guidance Notes
Part A1.1 Minimum Horizontal Separation Distance for Cooling Towers
Guidance notes are given below to clarify the following section of Code of Practice for Water –
cooled Air Conditioning Systems (“CoP(WACS)”):
Section 4.1.3, Part 1 (p.17)
Background:Enquiries on minimum separation distance for cooling tower installation are frequently received,
especially on the measuring points and measurement method. CoP (WACS) users sometimes
misinterpret the measuring points to be from the center of the cooling tower (for horizontaldistance measurement) and/or from the top or bottom of the cooling tower (for vertical distance
measurement). Furthermore, they sometimes mistakenly use the sum of horizontal and vertical
separation distance or directional distance as the separation distance to meet the CoP (WACS)
requirements.
INTAKE LOUVRE
COOLINGTOWER
EXHAUST
COOLINGTOWER
INTAKE
MIN. 7.5m COOLING
TOWERINTAKE
MIN. 7.5m
EXHAUST
AIR INTAKE/EXHAUSTS
ON BUILDING
FACADE
COOLINGTOWER
EXHAUST
MIN. 20m
MIN. 7.5m
AIR INTAKE
COOLING TOWER
EXHAUST
COOLING
TOWER
INTAKE
EXHAUST
LOUVRE
MIN. 7.5mCOOLING TOWER
EXHAUST
COOLINGTOWER
INTAKE
MIN. 7.5m
INTAKELOUVRE
COOLING
TOWER
EXHAUST
AIR INTAKE/EXHAUSTS ON
BUILDINGFACADE
MIN. 7.5m
COOLINGTOWER
EXHAUST
COOLINGTOWER
INTAKE
MIN. 7.5m
COOLINGTOWER
INTAKE
Figure 1: Enquiries on measuring point in determining the minimum separation distance
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Electrical & Mechanical Services Department Guidance Notes on Code of Practice forWater-cooled Air conditioning Systems
Guidance Notes:The minimum horizontal separation shall be measured from the nearest edge of the cooling
tower exhaust / intake to the nearest edge of the outdoor air intake, exhaust air outlet or operable
window. Also, horizontal distance shall be considered separately from the vertical distance and
they shall not be summed together or used directional distance to meet the minimum separationrequirement. The figures below illustrate some common misinterpretations with respect to the
CoP(WACS) requirement.
INTAKE LOUVRE INTAKE LOUVRECOOLING COOLINGTOWER
EXHAUSTMin. 7.5m for all
Min. 7.5m for alltypes of building
TOWER
EXHAUST
types of building
COOLING COOLINGTOWER TOWER
INTAKE INTAKE
× √
Figure 2: Measuring point shall not be fromthe center of the cooling tower
Figure 3: Measuring point shall be from thenearest edge of the cooling tower exhaust /intake
COOLING TOWER
EXHAUST
COOLING TOWER
EXHAUST Min. 7.5m for alltypes of building
COOLINGTOWER
INTAKE
Min. 7.5m for alltypes of building
COOLINGTOWER
INTAKE
EXHAUSTLOUVRE
EXHAUST
LOUVRE
× √
Figure 4: Separation distance shall not bethe sum of horizontal and vertical distance
Figure 5: Horizontal distance shall beconsidered separately from the verticaldistance
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Electrical & Mechanical Services Department Guidance Notes on Code of Practice forWater-cooled Air conditioning Systems
COOLINGTOWER
EXHAUST
COOLINGTOWER
INTAKE
AIR INTAKE/EXHAUSTS ONBUILDING
FACADE
× √
Min. 7.5m COOLINGTOWER
INTAKE
COOLINGTOWER
EXHAUST
AIR INTAKE/EXHAUSTS ON
BUILDINGFACADE
Figure 6: Measuring point shall not be thedirectional distance as the separation
distance
Figure 7: Measuring point shall be from thenearest edge of the cooling tower exhaust to
the façade horizontally
INTAKE LOUVRE INTAKE LOUVRE
COOLING TOWER
EXHAUSTMin. 7.5m for alltypes of building COOLING TOWER
EXHAUSTMin. 7.5m for alltypes of building
COOLING COOLING
TOWER TOWER
INTAKE INTAKE
× √
Figure 8: Separation distance shall not bethe sum of horizontal and vertical distance
Figure 9: Horizontal distance shall beconsidered separately from the verticaldistance
LOCKED LOCKED
WINDOW/BLANKOFF WINDOW/BLANKOFF
LOUVRE LOUVRE
Min. 20mMin. 20m
COOLING TOWERINTAKE LOUVRE INTAKE LOUVRE
EXHAUST
Min. 7.5m Min. 7.5m Min. 7.5m Min. 7.5m
INTAKE LOUVREEXHAUST LOUVRE INTAKE LOUVREEXHAUST LOUVRE
× √
Figure 10: Measuring point shall not befrom the centre of the louvre
Figure 11: Measuring point shall be from thenearest edge of the exhaust / intake louvre
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Electrical & Mechanical Services Department Guidance Notes on Code of Practice forWater-cooled Air conditioning Systems
1.2 Cooling Tower Installation Location (Pedestrian Thoroughfare)
Guidance notes are given below to clarify the following section in the CoP(WACS): Section 4.1.4, Part 1 (p.17)
Background:
It is common to propose locating cooling towers on low-rise podium roof of one, two or severalstoreys high building with an adjacent pedestrian thoroughfare or walkway below running alongthe building boundary or façade. The horizontal separation between the cooling tower exhaustand the pedestrian thoroughfare is less than 7.5 m. The designers often enquire the possible waysto meet the CoP (WACS) requirement and minimise nuisances to the public.
< 7.5m for all typesCOOLING TOWER
EXHAUST
COOLINGTOWER
INTAKE
of building
Figure 12: Separation between the cooling tower exhaust and pedestrian thoroughfare
Guidance Notes:It is required under CoP(WACS) that no pedestrian thoroughfare, area of public access, or place
where people gather together for activities shall be located within 7.5m from the nearest edge of
the cooling tower exhaust. If such minimum separation requirement cannot be met due to site
constraints (e.g. not enough space for setting back cooling towers from the parapet/building
boundary), some mitigation measures may be considered where appropriate to enable
compliance with the requirement, hence minimise nuisances to the public from the cooling tower.
Below are some examples showing mitigation measures proposed for reference.
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Electrical & Mechanical Services Department Guidance Notes on Code of Practice forWater-cooled Air conditioning Systems
COOLING TOWER
EXHAUST
COOLINGTOWER
INTAKE
< 7.5m
Min. 7.5m
OVERHEAD
COVER
Figure 13: Provide overhead cover above the walkway
< 7.5m
Min. 7.5m
COOLING TOWER
DISCHARGE HOOD
COOLING TOWER
INTAKE
Figure 14: Install discharge hood to re-direct the exhaust air away from the walkway
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Electrical & Mechanical Services Department Guidance Notes on Code of Practice forWater-cooled Air conditioning Systems
1.3 Cooling Tower Installation Location (Extended Ductwork)
Guidance notes are given below to clarify the following section in CoP(WACS):
Section 4.1.6, Part 1 (p.17)
Background:Some project designers found it is unclear in meeting the minimum separation requirements
when cooling towers are designed to be installed inside a mechanical floor with extended
ductwork to discharge through facade louvres. They find it difficult to arrange the air intake,
exhaust air outlet and operable window on its vertical building façade distant from the cooling
tower to meet the requirements.
COOLING TOWER PLANT ROOM
COOLING TOWER
EXHAUST
COOLING TOWER
INTAKE
FAÇADE WITHWINDOW AND/OR
LOUVRE
Figure 15: Cooling tower installed inside building with extended ductwork for discharge fromfacade louvre
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Electrical & Mechanical Services Department Guidance Notes on Code of Practice forWater-cooled Air conditioning Systems
Guidance Notes:If a cooling tower is installed indoor with an extended ductwork for exhaust air, the measurement
shall be from the nearest edge of the exhaust louvre on the building façade. Air intakes,
exhausts air outlet and operable windows of the vertical building facade shall be distant from the
nearest edge of the cooling tower exhaust by minimum distance of 7.5 m below and/or 20 mabove, as the case may be.
If the requirement cannot be adequately met, the designer may consider in consultation with their
building design counterpart and/or the facility management whether mechanical locking devices
can be provided to the operable windows and the louvres can be blanked off to comply with
CoP(WCAS) under normal conditions. Cautionary signage shall be provided near the locked
windows to alert occupants.
LOCKED
WINDOW/BLANKOFFLOUVRE
< 20m for all types ofbuildin
COOLING TOWER COOLING TOWERINTAKE EXHAUST
< 7.5m< 7.5m
IF EXHAUST LOUVRE, LOCKED NEED TO BE BLANK WINDOW/BLANKOFF
OFF (EXHAUST) LOUVRE (INTAKE)
Figure 16: Locked window and blank-off louvre on the same facade surface within the restrictedzone
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Electrical & Mechanical Services Department Guidance Notes on Code of Practice forWater-cooled Air conditioning Systems
1.4 Cooling Tower Installed on Roof and Affecting the Adjacent Buildings
Guidance notes are given below to clarify the following section in the CoP(WACS):
Section 4.2, Part 1
Background:Some project designers found themselves unclear on how to meet the minimum separation
requirement between the cooling tower and the air intake, exhaust air outlet and operable
window on the adjacent building façades. The measuring points are often incorrect and result in
the cross-contaminations between the cooling tower and the adjacent buildings.
EXHAUST LOUVRE
EXHAUST LOUVRE
COOLING TOWEREXHAUST
COOLINGTOWER
INTAKE
Figure 17: Cooling tower installed on roof surrounding by adjacent buildings
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Electrical & Mechanical Services Department Guidance Notes on Code of Practice forWater-cooled Air conditioning Systems
Guidance Notes:
In order to minimise nuisance caused by the cooling tower to the adjacent buildings and vice-versa the nuisance caused by the adjacent buildings to the cooling tower; the minimumhorizontal separation distance shall be imposed. The measurement point shall be from thenearest edge of the cooling tower intakes /exhausts to the nearest edge of air intake and operablewindows of the adjacent buildings.
EXHAUST LOUVRE
EXHAUST LOUVRE
Min. 7.5mMin. 7.5m
COOLINGTOWER
EXHAUST
COOLING TOWERINTAKE
Figure 18: Horizontal separation requirement for cooling tower and the adjacent buildings
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Electrical & Mechanical Services Department Guidance Notes on Code of Practice forWater-cooled Air conditioning Systems
1.5 Cooling Tower Installed on Podium Roof
Guidance notes are given below to clarify the following section in the CoP(WACS):
Section 4.3, Part 1
Background:
In a composite building, it is common to have building blocks located on the podium roof.
Project designers may wish to install cooling towers on the podium roof to provide air-
conditioning for the commercial floors. If the cooling towers are located too close to the
surrounding building blocks, contaminants from the cooling tower, as well as generated noise,
may affect the building users through the air openings (air intakes/exhausts/operable windows)
on the building blocks.
Whist the CoP(WACS) has generally specified a horizontal separation distance of minimum 7.5m from the cooling tower to the nearby air outlets/windows, some cases have raised issues insituations where the air outlets/windows are far above the cooling tower but with a horizontalseparation distance less than 7.5 m. How will the separation distance requirement apply to thesecases?
COOLING TOWEREXHAUST
COOLING TOWERINTAKE
AIRINTAKE/EXHAUSTS
ON BUILDING
FACADE
FAÇADE WITHWINDOW AND/OR
LOUVRE
Figure 19: Cooling tower installed on podium roof
Guidance Notes:
Scenario 1: Separation distance between the cooling tower exhaust and the building’s air
openings (air intake, exhaust air outlet and operable window) above podium roof.
Cooling towers on the podium roof shall generally be located away from the building façade to
meet the minimum horizontal separation distances specified in Table 1.1 of Part 1 of the
CoP(WACS). In particular, the cooling tower exhaust should be away from air intake, exhaust
air outlet and operable windows with a minimum horizontal distance of 7.5 m to avoid potentialrisk of nuisance or spread of Legionella bacteria (if any) arising from the cooling towers. For
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Electrical & Mechanical Services Department Guidance Notes on Code of Practice forWater-cooled Air conditioning Systems
cooling tower on the podium roof with adjacent tall building, all cases with horizontal separation
less than 7.5 m will not be considered acceptable.
Please note that clause 4.3.3 of Part 1 of the CoP(WACS) requires the cooling tower exhaust
shall be discharged away from the operable windows and outdoor air intakes. This can beachieved by a cooling tower discharge hood to direct the exhaust away from the building façade.
COOLING TOWER
DISCHARGE HOOD
COOLING TOWERINTAKE
AIRINTAKE/EXHAUSTSON BUILDING
FACADE
Min 7.5m
Figure 20: Horizontal separation requirement for cooling tower installation on podium roof
Scenario 2: Separation distance between the cooling tower intake/exhaust and the building’s air
openings (air intake, exhaust air outlet and operable window) below podium roof.
Cooling towers on the podium roof should generally be set back from the building parapet with a
minimum horizontal separation distance of 7.5 m to avoid potential risk of nuisance or spread of
Legionella bacteria (if any) arising from the cooling towers to air openings (air intake, exhaust
air outlet and operable window)
In cases where the cooling tower cannot meet the minimum horizontal separation requirement(i.e. separation is less than 7.5 m), designers may consider alternative location. That location
shall have adequate vertical separation distance for the building’s air openings in relation to the
cooling tower. Such distances are shown below (similar to the minimum separation distances in
Table 1.1 in Section 4.1 of CoP (WACS) Part 1):
(a) Between the nearest edge of cooling tower exhaust and the nearest edge of podium’s air
intake, exhaust air outlet and operable window: minimum vertical separation of 7.5 m ;
(b) Between the nearest edge of cooling tower intake and the nearest edge of podium’s air
exhaust outlet: minimum vertical separation of 7.5 m and
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Electrical & Mechanical Services Department Guidance Notes on Code of Practice forWater-cooled Air conditioning Systems
(c) Between the nearest edge of cooling tower intake and the nearest edge of podium’s air
intake and operable window: minimum vertical separation of 5 m.
COOLING TOWEREXHAUST
COOLINGTOWER
INTAKE
AIR INTAKE / OPERABLEWINDOW ON BUILDING
FACADE
Min. 7.5m
Min. 5m
< 7.5m
Figure 21: Vertical separation requirement between podium roof cooling tower andbuilding’s air intake and operable window below podium roof
COOLING TOWEREXHAUST
COOLING TOWERINTAKE
EXHAUST AIR OUTLETON BUILDING FACADE
< 7.5m
Min. 7.5m
Figure 22: Vertical separation requirement between podium roof cooling tower andbuilding’s exhaust air outlet below podium roof
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Electrical & Mechanical Services Department Guidance Notes on Code of Practice forWater-cooled Air conditioning Systems
COOLING TOWEREXHAUST
COOLING TOWERINTAKE
EXHAUST AIR OUTLET ONBUILDING FACADE
Min. 7.5m
Figure 23: Horizontal separation requirement between podium roof cooling tower intakeand building’s exhaust air outlet on podium roof
PODIUM ROOF/ ROOF
WINDOW OPENNINGS
Min. 7.5m Min. 7.5m
WINDOW OPENNINGS
LOCKEDWINDOW/BLANK-
OFF LOUVRE
< 7.5m
Min. 7.5m
WINDOW OPENNINGS
LOCKEDWINDOW/BLANK-OFFLOUVRE
Min. 7.5m
WINDOW OPENNINGS
Figure 24: Horizontal separation requirement between podium roof / roof cooling tower andlouvres on building façade
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Electrical & Mechanical Services Department Guidance Notes on Code of Practice forWater-cooled Air conditioning Systems
1.6 Cooling Tower Installed at Indoor with Vertical Discharge through Roof orHorizontal Discharge through Side Wall
Guidance notes are given below to clarify the following section in the CoP(WACS):
Section 4.4, Part 1
Background:For some high-rise buildings, cooling towers may be housed in a plant room with
discharge/intake through the roof/side walls of the plant room. The discharge and/or intake may
affect or be affected by adjacent buildings if they are not correctly located.
AIR INTAKELOUVRE/OPERABLE
WINDOW
FRESH AIRINTAKE FORCOOLING TOWER
EXHAUST AIRLOUVRE
COOLING TOWERPLANT ROOM
Figure 25: Cooling Tower installed in plant room with vertical discharge through roof andhorizontal intake through side wall
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Electrical & Mechanical Services Department Guidance Notes on Code of Practice forWater-cooled Air conditioning Systems
Guidance Notes:In cases where the plant room houses the cooling tower, the horizontal distance between the
plant room structure/edge and the nearby building’s air opening (air intake, exhaust air outlet and
operable window) is allowed to be less than 7.5 m. However, the exhaust air outlet of the cooling
tower shall have a horizontal separation distance of 7.5 m to the air opening of the adjacent building regardless the position of the plant room. Furthermore, the plant room air intake for the
cooling tower intake shall have a horizontal separation distance of 7.5 m to the exhausts outlet of
the adjacent buildings. The plant room air intake for the cooling tower shall have a horizontal
separation distance of 5 m from air intake and operable window of adjacent buildings.
The measurement point shall be from the nearest edge of the cooling tower exhaust to the
nearest edge of the air intake, exhaust air outlet and operable window of adjacent buildings.
AIR INTAKELOUVRE/OPERABLE
WINDOW
Min. 7.5m
FRESH AIRINTAKE FOR
COOLING
TOWER
Min. 5m Min. 7.5mEXHAUST AIR
LOUVRE
COOLING TOWER
PLANT ROOM
Figure 26: Separation requirement between intake lourve / exhaust outlet of indoorcooling tower and the adjacent building air opening
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Electrical & Mechanical Services Department Guidance Notes on Code of Practice forWater-cooled Air conditioning Systems
Part B
1.7 Control of Bacterial Growth
Guidance notes are given below to illustrate the following section in the CoP(WACS):
Section 2.6, Part 2 (p.7)
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Implement corrective action
Electrical & Mechanical Services Department Guidance Notes on Code of Practice forWater-cooled Air conditioning Systems
Guidance Notes:
Control Measures for Legionella
Regarding detection of Legionella in water samples collected from cooling towers, the control
strategies and procedures stated in Section 2.6.1 of Part 2, CoP (WACS). The flow chart below(Figure 27) illustrate the flow chart of Part 2, CoP(WACS) for easy reference.
Water samples collected from
cooling towers and test
Review programmeSystem under control
(a) Maintainquarterly monitoring
(b) Maintain water
treatment programme
(a) Investigate problem (b) Review water treatment programme
(c) Take necessary remedial action including
immediate on-line disinfection as described in section3.3 and undertake control strategy (3).
Legionella count
Collect and test a water sample within 3 to 7 days
after on-line disinfection
If not detected If detected at
≥10 and<
100 cfu/mL
If detected at
≥100 and<
1000 cfu/mL
Not detected(<10 cfu/mL)
Detected at≥10 and<1,000 cfu/mL
Detected at≥1,000 cfu/mL
If detected at
≥1000 cfu/mL
Strategy (1) Strategy (2)
Strategy (3)
(a) Investigate problem(b) Review water treatment programme
(c) Take necessary remedial action includingimmediate emergency decontamination as described
in section 3.6 and undertake control strategy (5).
Collect and test a water sample within 3 days after
emergency decontamination
Strategy (4)
Strategy (5)
If not detected If detected at
≥10 and<
100 cfu/mL
If detected at
≥100 and<
1000 cfu/mL
Repeat
controlstrategy (2)
Investigate problem andreview water
Collect and test
another watersample.
Collect and testanother water
sample.
If 2 consecutivesamples have no
Legionelladetected,
repeat controlstrategy (1)
Repeatcontrol
strategy (2)
Investigate
problem andreview water
treatment programme,immediately
carry out
cleaning anddisinfectionagain as
described insection 3.4 and
repeat control
strategy (3)
Immediatelycarry out
cleaning and
disinfection asdescribed in
section 3.4 andundertakecontrol
strategy (5)If 2 consecutivesamples have no
Legionelladetected,repeat control
strategy (1)
If detected at
≥1000 cfu/mL
Investigate
problem andreview water
treatment
programme,immediately
carry out system
emergencydecontaminationas described in
section 3.6 andrepeat control
strategy (5)
treatment programme,
immediately
carry outcleaning and
disinfectionagain asdescribed in
section 3.4 and
repeat controlstrategy (5)
Figure 27: Flowchart for Control Strategies for the presence of Legionellae
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Electrical & Mechanical Services Department Guidance Notes on Code of Practice forWater-cooled Air conditioning Systems
Control Measures for Heterotrophic Micro-organisms
Regarding the Heterotrophic Colony Count (HCC) test results of water samples collected fromcooling towers, the control strategies and procedures stated in Section 2.6.3 of the CoP (WACS),
Part 2 are illustrated in the flow chart below (Figure 28) for easy reference and observation.
Water samples collected fromcooling towers and test
Review Programme operationSystem under control
(a)Maintainmonthly
monitoring(b) Maintain watertreatment
programme
(a) Investigate problem(b) Review water treatment programme
(c) Take necessary remedial action includingimmediate on-line disinfection as described insection 3.3 and undertake control strategy (3).
Heterotrophic Colony Count (HCC)
Implement corrective action
(a) Investigate problem(b) Review water treatment programme(c) Take necessary remedial action including
immediate emergency decontamination asdescribed in section 3.6 and undertake control
strategy (5).
Collect and test a water sample within 3 to 7 days after
on-line disinfection
If test result is<100,000 cfu/mL
If test result is
≥100,000 and<
5,000,000 cfu/mL
If test result is≥5,000,000
cfu/mL
Detected at
<100,000 cuf/ml
Detected at
≥100,000 and<5,000,000 cfu/mLDetected at
≥5,000,000 cfu/mL
If test result is<100,000 cfu/mL
If test result is
≥100,000 and<
5,000,000 cfu/mL
If test result is≥5,000,000
cfu/mL
Collect and test a water sample within 3 to 7 daysafter emergency decontamination
Strategy (1) Strategy (2) Strategy (4)
Strategy (3) Strategy (5)
Repeat control Immediately Immediately Repeat control Immediately Investigatestrategy (1) carry out carry out strategy (1) carry out problem and
cleaning and cleaning and cleaning and review waterdisinfection disinfection as disinfection treatmentagain as described in again as programme,described in section 3.4 and described in immediatelysection 3.4 and undertake section 3.4 and carry outundertake control undertake emergencycontrol strategy (5) control decontaminationstrategy (2) strategy (4) again as
described in
section 3.6 andrepeat control
strategy (5)
Figure 28: Flow Chart for Control Strategies for the presence of heterotrophic microorganism
2011 Edition (November 2011) Page 18