Transcript Legionella Risk Management - Cooling Tower Maintenance Inc

Legionella Risk Management
Drew Industrial Division
Ashland Canada Corp
Legionnaires’ Disease
A potentially fatal form of
pneumonia caused by the
inhalation of airborne water
droplets contaminated by
Legionella pneumophila
and other bacteria of the
family Legionellaceae
®
Facts About
Legionnaires’ Disease
USA





First cases in 1976 at Bellevue Stratford
Hotel, PA; 221 people contracted LD, 34 died
Severe respiratory infection simulating
pneumonia
An estimated 10,000 to 50,000 cases per year
An estimated 1 percent of those exposed
contract Legionnaires’ disease
Estimated fatality rate is 15-20 percent
®
Legionella Regulations

Legionella legislation in Australia,
NZ and UK forces customers to treat
properly:
– Prosecution and fines for noncompliance
– Can shut down the system
®
Legionellosis Compared to
Pontiac Fever
Legionnaires Disease
Pontiac Fever
First Noted
1976
1968
Form
Bacteria
Virus
Attack Rate
1 – 5 Percent
95 Percent
Symptoms
Fever, Cough, Muscle Aches, Chills,
Headache, Chest Pain , Sputum,
Diarrhea, Confusion
Fever, Cough, Muscle
Aches, Chills, Headache,
Chest Pain, Confusion
Effects on Lung
Pneumonia, Pleural Effusion
Pleuritis, No Pneumonia
Other Affected Organ
Systems
Kidney, Liver, Gastrointestinal Tract,
Nervous System
NONE
Case-Fatality Ratio
15 – 20 Percent
No Fatalities
®
Susceptability to Legionnaires’
Disease








Age – The very young and 40 – 70 year olds
Gender – Males are twice as likely to contract the
disease than females
Heavy Smoker
Heavy Drinker
Individuals with weakend immune systems –
Cancer, AIDS, HIV positive
Chronic Medical Problems – respiratory, diabetes,
asthma, renal dialysis
Certain Drug Therapies – corticasteroids or other
immunosuppressive therapies
Organ Transplants
®
Legionella




Rod-shaped, aerobic
organisms
Found in natural and
man-made water systems
Up to 40 species
identified
Legionella pneumophila
– Virulent strain causing
Legionellosis
®
Factors Determining the Risk
of Contracting the Disease
®

A source of Legionella

Favorable growth conditions

Aqueous aerosol

Sufficient organisms to cause
infection

Susceptible individual
Legionella Bacteria

Source of Legionella
– Pervasive organism

Conditions for growth
– 68 - 122 F (20 - 50 C)
– pH 6-8
– Stagnant waters
– A nutrient source
®

Biofilms, organics

Sediments, deposits
Legionnella Bacteria




Soil Derived
Spore Former ,Facultative Anaerobe
(Maturing Biofilm)
Iron and Amino Acids are Food Sources
“CDC” Legionella Pnemophila
–
–
–
–
®
90% of All Outbreaks
82% are from Serogroup 1
Others from Serogroup 4 and 6
Outbreak Potential at ≥ 1000 CFU/ML
®
Systems Promoting Growth







Cooling towers
Evaporative condensers
Hot and cold water systems
Taps and showerheads
Humidifiers and air washers
Spa and whirlpool baths
Decorative fountains
®
Hot Water
Requirements for Superheating of potable
water systems; If the water is heated to at
least 149 degrees F.
Legionella die rapidly at 131 F and killed
immediately at temperatures over 140 F.
Water outlets are flushed for at least 30
minutes (Pittsburgh) or 5 min (CDC).
It is recommended that the Hot water stored
above 140 F circulation with the minimum
return of 124 F.




®
Cold Water
For cold water, the same as above can be
done with heater or shock hyperchlorination
( >10 ppm) of chlorine in water and flush for at
least 5 minutes.


Additional protocols available and may be
required on a local basis.
®
Legionella Testing



General consensus is that testing is not
effective
Money better spent on biofilm control
Many professional organizations
provide guidance such as CTI, ASHRAE,
etc.
®
The Role of Biofilms

The prime culprit
– Harbors Legionella and promotes growth

Promotes growth of higher life forms such as
Protozoa and Amoeba - act as a protective host
Reversible
adsorption
of bacteria
(sec.)
Irreversible Growth &
attachment division of
Water Flow
of bacteria bacteria
(sec.-min.) (hrs.-days)
trapped particles providing
nutrients
Exopolymer
production
& biofilm
formation
embedded bacterial(hrs.-days)
cells
Attachment
Planktonic
of
other
organisms to
biofilm
(days-months)
Sessile
Surface
®
We know that…
In order to minimize Legionella growth:



Chemical treatment alone is not effective
Minimization is dependent upon design,
maintenance, contaminants, awareness and
consistent implementation
Effective Legionella management requires a
“best practices” approach: A system that is
properly treated, serviced and supervised
®
Simplified Surface Growth
®
Field Study on Biofilm Growth
®
Phase
Time
Colonization
15 Minutes
Growth Detection
2 Days
Biofilm Formation
(Exopolymer/ Minimum Biofouling)
5 Days
Maximum Biofilm Growth
(8 – 10 Cells Thick)
14 Days
Fully Mature Biofilm Matrix
31 – 40 Days
Three Dimensional Biofilm
®
We know that…
Legionella risk minimization depends on
the ability to control:
Growth
®
Dissemination
Transmission
Areas Promoting Growth
Biofilm
Debris
®
CTI Protocol
Establishes Baseline Program

Legionella Guidelines
February, 2000 position paper
– Background summary and guide
– Platform for developing a more
comprehensive, definitive program

Guidelines were based on industry
consensus prior to ACOP 2001
(UK-Regulated Approved Code of Practice)
CTI position paper is an industry-developed consensus for
Legionella best practices protocol. However, program
implementation is subject to facility interpretation.
®
CTI Protocol

Halogen feed is required
– Continuous halogen with free residual is preferred

Use non-oxidizing biocide and/or biodispersant as needed
– Intermittent halogen with higher levels of free residual
is acceptable



Non-oxidizing biocide specifically recommended
Biodispersant may be required
Testing and monitoring
– Routinely monitor total bacteria using dip slides or agar

Maintain less than 10,000 CFU/mLspecifically recommended
– Routine Legionella testing is not recommended


Only after suspected case or following sterilization
Sterilization may be required
– Maintain 5 ppm FAH for 6 hours minimum
®

Specifically recommended based on various system indicators
Drew Industrial’s
Best Practices Legionella Risk
Management Program
®
Total System Approach:
Five Areas of Activity and
Performance
 Comprehensive system
assessment
 Intensive microbiological treatment
program
 Sterilization and cleaning
 Monitoring and control
 Documentation
®
Comprehensive
Water System
Management
®
 System Assessment

System survey
– In-depth survey of system mechanical design
and operating conditions
– Utilizes established protocol, ex BSRIABuilding Services Research Institute Assoc. (UK)

Identify, evaluate and rank specific factors
associated with potential for microbiological
growth and Legionella
– Mechanical and chemical

Determine risk minimization action plans
®
Survey Provides Plan to
Reduce Growth
1. Address non-chemical ways to improve
microbiological control
 Remove piping dead legs
 Revise operating procedures
 Rotate idle equipment
 Use side stream filtration
2. Identify operating procedures, mechanical
design and other factors that contribute
to growth of Legionella
®
Identify areas that
promote growth or
dissemmination
of Legionella
Critical Factors
Stagnant conditions
Nutrients and conditions for growth
Water and chemical treatment quality
Water system mechanical conditions
Location and exposure risk





®
“Ideal System”







Water flow is continuous
No dead legs or stagnant
conditions
Basin and deck protected
from sun
No evidence of sludge,
debris, algae
Drift eliminators installed,
functioning
No evidence of aerosols, drift
System not near health care,
aged, residential facility
®






Low number of people
potentially exposed
Halogen used
Biodispersant/biodispersing biocide used
Comprehensive water
treatment program
Automated biocide and
chemical dosing
Continuous automated
monitoring, control

Intensive Microbiological
Treatment Program
Drew Industrial’s Best Practices Legionella
risk management program requires an
effective system approach that
incorporates an intensive microbiological
control program along with additional risk
management actions
®
Intensive Microbiological
Treatment Program

Cooling Technology Institute (CTI) position
paper
– Basic program approach

Drew Industrial’s recommended intensive
microbiological treatment program
– Comprehensive treatment program incorporating
the CTI-recommended actions plus several
additional practices
®
Intensive Microbiological
Treatment Program


Drew Industrial’s program recommendations
for minimizing the potential for growth of
Legionella bacteria in cooling systems
A comprehensive microbiological control
program
 Includes
all recommended CTI actions
 Includes CTI optional recommendations
 Provides more definitive guidelines

Four protocols based on halogen feed
®
Continuous Oxidant Feed Protocol

Continuous feed for chlorine, bromine,
BCDMH or stabilized bromine
– Dosage:



Recommended 0.2 - 0.4 FAH and/or equivalent mV ORP
with a minimum requirement of a measurable residual FAH
For higher risk systems increase FAH residual as needed
to control CFU level and biofilm
Feed a supplemental organic biocide*
– Recommend biocide be glutaraldehyde or an
alternate biocide fed with biodispersant
– Feed once per week or as needed to control biofilm
*Alternative choices of non-oxidizing biocide should be based on toxicant
evaluations (RPD)
®
Total System Approach:
Five Areas of Activity and
Performance
 Comprehensive system
assessment
 Intensive microbiological treatment
program
 Sterilization and cleaning
 Monitoring and control
 Documentation
®
 Intermittent Oxidant Feed Protocol

Intermittent Oxidant Feed
– Chlorine, bromine, BCDMH or stabilized bromine
– Minimum dosage: Hold 0.5 - 1.0 FAH and/or
equivalent mV ORP for a minimum of 2 hours each
day

Feed alternating supplemental organic
biocides*
– Recommend one biocide be glutaraldehyde or an
alternate biocide fed with biodispersant
– Feed an additional compatible organic biocide*
– Alternate feed once per week
* Dosages and alternative choices of non-oxidizers should be based on RPD results
®
Chlorine Dioxide
- A Selective Oxidant 




®
Oxidation potential not affected by pH
Selective oxidant
No dissociation; does not react with water
Does not react with amines, nitrogen
compounds
Highly effective against biofilm
Continuous Chlorine Dioxide Feed Protocol

Continuous chlorine dioxide feed
– Minimum dosage: 0.1 ppm residual ClO2 or
equivalent mV ORP

Feed a supplemental organic biocide as
needed based on biofilm control
– Recommend biocide is glutaraldehyde or an
alternate biocide fed with biodispersant*

Feed once per week or as needed to
control biofilm
*Alternative choices of non-oxidizing biocide should be based on RPD results
®
Intermittent Chlorine Dioxide Feed Protocol
 Intermittent chlorine dioxide feed
– Minimum dosage: 0.5 ppm residual ClO2 and/or
equivalent mV ORP for a minimum of 2 hours per day

Feed alternating supplemental organic
biocides*
– Recommend one biocide be glutaraldehyde or an
alternate biocide fed with biodispersant
– Feed an additional compatible organic biocide*
– Alternate feed once per week
Chlorine dioxide is also an effective supplemental biocide
for process cooling systems where contaminants that
increase bacterial growth are present.
*Alternative choices of non-oxidizing biocide should be based on RPD results
®
 Sterilization


Drew Industrial’s Best Practices
program recommendation includes
annual sterilization regardless of
overall system indicators
Procedure is per the CTI protocol
– Annual on-line system hyperhalogenation

Maintain 5 ppm FAH for 6 hours minimum, per the
CTI process
– Annual full system cleaning highly recommended


®
Perform six months following hyperhalogenation
If an off-line cleaning can not be performed, clean as
possible on-line and follow with a second hyperhalogenation
 Monitoring & Control
Program monitoring




FAH and/or ORP
Maintain Total Bacteria Counts below 10,000 CFU/mL
– Frequency as required to maintain performance
Treatment levels, system parameters, corrosion,
fouling, etc.
Legionella testing



Random Legionella testing is not recommended
Testing is recommended only after sterilization
Control schemes



®
Automation improves performance and efficiencies
Wide range of controllers available
Total System Approach:
Five Areas of Activity and
Performance
 Comprehensive system
assessment
 Intensive microbiological treatment
program
 Sterilization and cleaning
 Monitoring and control
 Documentation
®
Use of Proper Monitoring &
Control Equipment is Critical!
Microbiological
Residuals,
Corrosion, Scale
& Biofouling
On-line
ORP Halogen Control




ORP measures chemical
oxidation potential
Well documented sensor
and control technology
Provides amount of actual
oxidation capacity of
halogen regardless of form
or dissociation vs. pH
Relationship to FAH is
dependent on individual
system, chemistry
conditions
Each system has a specific
ORP breakpoint and an
effective level of ORP
®
700
600
(example only
System specific)
ORP
500
Control
400
Range
mV ORP

300
200
Break point
100
0
1
2 3 4 5 6
PPM Halogen Fed
Total System Approach:
Five Areas of Activity and
Performance
 Comprehensive system
assessment
 Intensive microbiological treatment
program
 Sterilization and cleaning
 Monitoring and control
 Documentation
®
 Documentation

Maintain complete, accurate logs
–
–
–
–
–



Biocide usage
Halogen tests and/or ORP log
Bacteria counts
Start-up and shut-down log
Log of operating procedures
Monthly service inspection reports
System disinfection logs
Contingency plans
®
Problem Systems?
Despite good control, monitoring and response,
some systems remain problematic.
Why?

Cooling systems are dynamic

Biofilms DO exist within system

System contamination DOES exist

Some system designs present
obstacles to effective Legionella
control
®
Problematic Systems
For these systems…
– Maintain an environment hostile
to bacteria at all times
– Continuously halogenate
– Continuously feed biodispersant
– Utilize reliable automation
– Utilize ORP control
– Regularly clean and disinfect
– Rigorously inspect and maintain
®
Survey of Field Test Results




In general it has been reported that 40 –
60% of Cooling Towers tested positive for
Legionnella
794 evaluations performed
277 (35%) tested positive for Legionella
Ranged from 1 to >9,000 CFU/ml
®
Detected Legionella Levels
<1-1 CFU/ml
2-9 CFU/ml
10-99 CFU/ml
100-999
CFU/ml
>=1,000
CFU/ml
76 isolates
24 isolates
104 isolates
55 isolates
18 isolates
27.4%
8.7%
37.5%
19.9%
6.5%
Based on 277 positive results
36.1% confirmed as <10 CFU/ML
26.4% confirmed as >100 CFU/ML
®
Legionnella Species Identifed
Speciation of 354 Isolates Recovered from
277 Legionella Positive Samples
Legionella pneumophila
245
(69%)
Legionella Species
109
(31%)
Legionella pneumophila
Serogroup 1
Serogroup 2-15
other than 1-15
85 isolates
34.7 %
®
132 isolates
53.9 %
28 isolates
11.4 %
Response to a Positive
Legionella Test Result

Action Level 1 - (Detectable - <1 CFU/ML)
– Risk Level - (Extremely Low)
– Confirm current treatment program

Action Level 2 - (1 - 9 CFU/ML)
– Risk Level - (Low)
– Increase frequency of current treatment to one
additional dose of biocide for two weeks
®
Response to a Positive
Legionella Test Result

Action Level 3 - (10 - 99 CFU/ML)
– Risk Level - (Low to Moderate)
– Increase treatment concentration and frequency to two
additional doses of biocide weekly for two weeks

Action Level 4 - (100 - 499 CFU/ML)
– Risk Level - (Moderate)
– Increase treatment concentration and frequency to two
additional doses of biocide weekly for 3 to 4 weeks
– On-line halogen addition / additional organic dispersant
maybe required
®
Response to a Positive
Legionella Test Result

Action Level 5 - (500 - 999 CFU/ML)
– Risk Level - (Moderate to High)
– Hyperchlorination required possibly off-line
– Use Halogen at 0.2 – 0.4 ppm FAH continuous or daily shocks
of 0.5 – 1 ppm FAH for 2 to 4 hours

Action Level 6 - (>1,000 CFU/ML)
– Risk Level - (High)
– Use halogen continuously at 1 ppm FAH for 6 hours, then 0.2 –
0.4 ppm FAH plus feed non-oxidizer every apparent retention
time for 1 week will be required
– Off-line sterilization using halogens at 5-10 ppm FAH for 6 to 24
hours, organics, and biodispersants may be required
– Retest in 1 week
®
Action Levels

Immediate response to positive test results

On-line treatment requires a minimum of
14 days to produce results

Unrealistic a system could be totally
Legionella free
®
Thank You
®
Registered trademark and ™ trademark of Ashland Inc.
Ashland Inc.
© 2001
®