Transcript Cooling Tower Maintenance Legionella Awarness

Cooling Tower Maintenance
Legionella Awareness
3rd Installment
®
CTM/Ashland Presentations





Legionella Awareness – 2003
Filtration of Cooling Waters – 2005
Legionella Risk Management – 2006
Legionella Proactive Protocol – 2008
Literature References
®
Legionella Proactive Protocol

Introduction/Refresher

ASRAE System that may Harbour Legionella and
What to Do

Risk Category

Legionella Testing Requirements

Frequency of Cleaning/Disinfection

Action Levels and Associated Response and
Cleaning Steps

Cooling Tower Design Best Practice

Maintenance Considerations
®
Legionella Proactive Protocol


Implement Risk Management Criteria
Maintenance and Record Keeping
– Begin now as Legislation will be forth coming
– Allows for a Basis of Estimation
- Man
- Methods
- Materials
– Estimates can be Reported to Management.
While Focus has been Reduction of Costs they
will need Estimates as the Cost of Ownership is
Going Up.
®
Refresher Information
®
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
Factors Determining the Risk of
Contracting the Disease

A source of Legionella

Favorable growth conditions

Aqueous aerosol

Sufficient organisms to cause
infection

Susceptible individual
®
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
®
Effects of Cooling System Dynamics –
cfu/ml Same Day Comparative Samples
(Example System Treated with Continuous Oxidant and
Slug Feed of Glutaraldehyde Once Per Week)
Flowing Bulk Water
Basin Chip Scale
Basin Sludge
Dead Head (off)
Plate/Frame XER
Slip Stream
By-pass (10%)
Plate/Frame
®
Aerobic
Bacteria
Fungi
Anaerobic
Bacteria
Higher
Life Forms
<10
1600
<10
10
<10
1,000,000
No
Yes
3,500,000
20
1,000,000
Yes
400
<10
10,000
Yes
<10
<10
<10
No
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
®
Oxidant Feedrate
Oxidant Feedrate
5
4.5
4
3.5
3
2.5
2
1.5
Ff 1
0.5
0
Fi
system biofilm demand
0.5 ppm oxidant residual
raw water demand
1
2
3
4
5
6
7
8 9
Time
Time to satisfy System Demand
®
10 11 12 13 14 15
tBreakthrough
Systems That May
Harbour Legionella
®
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
®
Potable Water Supply (AWWA)



New Piping and Additions
High Velocity Flush (HVF) initially at 8-15
ft./sec. if possible
Continuous Flush at 2.5 ft/sec.
– ≥ 10 ppm FAC for 24 Hours
– ≥ 50 ppm FAC for 3 Hours

Slug and Hold at ≥ 100 ppm FAC for 3
Hours is an alternative
®
Potable Water Systems

Emergency Water Systems
– Stagnant/Idle
– Ideal Temperatures – Reach Room Temp

Eye Wash/Showers (Low to no Atomization)

Fire Systems

Periodically Flush
®
Potable Water Systems
Cold Water – Store at ≤ 20ºC (68ºF)
 Hot Water
- Store at 50 - 60ºC (124-148ºF)
- Operate Return Water ≥ 50ºC (124ºF)
 Eradication

- Thermal - 66ºC to 70ºC (150ºF) for 8 hours and Flush
outlets for 30 minutes
- Chemical - ≥ 2 ppm (10 ppm) FAC for 2-24 hours at pH 7-8;
Flush for 5 minutes
- Copper/Silver Ionization,
- 0.2 – 0.8 ppm Copper
- 0.02 – 0.08 ppm Silver
®
Legionnella and
Water Temperature
®
SPAS







Hydrotherapy Pools, Whirl Pools, Hot Tubs
pH 7.2 - 7.8; 7.4 - 7.6 Ideal
FAC 3 - 10 ppm; 4 - 5 ppm Ideal
FABr 4 - 10 ppm; 4 - 6 ppm Ideal
Ultra Violet Plus Peroxide
Ozone
Maintenance Once per day for 1 to 4 hours at
10 ppm FAC or 10X FAC in use
®
Other Water Systems


Treat and Maintain Similar to Cooling Tower Protocols
Fountains and Waterfalls
– Filtration
– Drain Regularly

Misters/Atomizers, Humidifiers, Air Washers
–
–
–
–
–
–
®
Coils, Spray Bars, Sumps, Mist Eliminators
Pre/Post Air Filtration
Bleed/Drain
Clean/Disinfect
Sludge Removal
UV – Air Space
RISK CATEGORY
®
Influence Risk Associated With Legionella
®
Dutch Frequency of Legionella Testing Minimum
Risk Category
Highest
1.
Frequency
Monthly
2.
Quarterly
3.
Quarterly to Yearly
4. Lowest
Yearly
Tests to be performed when
seasonal/environmental amplification is
highest, equipment change over or start ups
Dutch Risk Category
1.
Highest Risk – Cooling Towers < 200 meters from
Hospital, Nursing Home or Health Care Facility where
Occupants maybe immunologically compromised
2.
Cooling Tower < 200 meters of Retirement Home,
Hotel or Building Accommodating a Large Number of
People
3.
Cooling Tower in Residential and Industrial
Neighbourhoods
4.
Lowest Risk – Cooling Tower in Industrial Area > 600
metres Away from a Residential Area.
®
Survey of Process Risk
HIGH
Humidifier/Fogger
Aerosol Producing Process
Misters, Atomizers
Air Washers
Decorative Fountains and
Waterfalls
Whirl Pools
Hot Tubs
Shower Heads
Sludge/Settled Solids
>⅛″ - ¼″
LOW
Potable Water Hot/cold
Shower Heads
Cooling Towers/ Evaporative
Condensers Risking
increases with Location (i.e.
Grounds Levels, Near Air
Intakes/Windows), Local
Ground Cover, Air
Contamination/Approximately
to Exhaust See C.T.I. Design
and Maintenance
Consideration
Non-Visible
Temperature
35ºC (95ºF)
To 46ºC (115ºF)
<20ºC (68ºF)
>50ºC (124ºF)
Biological Activity
>104 CFU/ml
>105 CFU/cm2
Presence of Higher Forms
(OMEBA, PROTOZOA, ALGAE,
MOLD, FUNGUS).
≤103 CFU/ml
≤104 CFU/cm2
No Higher Life Forms
Factors Contributing to Legionella
Health Risks in Cooling Systems
Biofilm
Algae and
Protozoa
High Levels
Of
Heterotrophy
(i.e. CFU/ml)
Presence of
Legionella
®
Organic
Temperature
and pH
Contamination
Aerosols
Scale and
Corrosion
Stagnant
Water
Condition
of Drift
Eliminators
Exposure to
Sunlight
Intermittent
Operation
Tower
Repair
Water
Quality
Bio-Control
Program
Proximity
To
Populations
TABLE 2 – COOLING SYSTEM SUSCEPTIBILITY TO LEGIONELLA RISKS
ISSUE
COOLING TOWER (C.T.) LOCATION
CONDITION
GROUND
CORRECTIVE MEASURE
LEVEL AND/OR DIRECT
EXPOSURE TO POPULATION
C.T. AIR DISCHARGE NEAR BUILDING
FRESH AIR INTAKE
C.T. AIR DISCHARGE NEAR WINDOWS
IN BUILDINGTHAT OPEN
NONE
A DESIGN CONSTRAINS
A DESIGN CONSTRAINT, USE
THERMOGRAPHY TO DETECT DISTANCE OF AIR
TRAVEL WRT INTAKE LOCATION
NONE, A DESIGN CONSTRAINT, OR FIX
WINDOWS CLOSED, USE THERMOGRAPHY TO
DETECT DISTANCE OF AIR TRAVEL WRT
WINDOW LOCATION.
MAKE-UP
UNCLARIFIED, UNFILTERED, NO
DISINFECTION
PRETREATMENT EFFECTIVELY OR GO TO
POTABLE WATER SOURCE
HIGH AIRBORNE DIRT LOAD
NEAR
BY CONSTRUCTION AND OR
EXCAVATION
LACK OF GROUND COVER
TEMPORARY,
WATER FLOW
INTERMITTENT LEADING TO
STAGNATION, BIOFILMS, BIOSEDIMENTS, ANAEROBIC CONDITIONS
DRAIN
NONE,
STEP-UP BIO TREATMENT
APPLICATIONS, USE SIDE STREAM FILTRATION
COVER EXPOSED EARTH WITH AGGREGATE
MATERIALS OR VEGETATION, USE SIDE STREAM
FILTRATION (SEE ATTACHMENT I)
IF STAGNATION > 1 MONTH
ROTATE EQUIPMENT WEEKLY WITH MILD
STERILIZATION (5 PPM FAH, 6 HOURS) UPON
RESTARTS
INSTALL 5-10% SLIP STREAM FLOW PROVIDED
COOLING WATER IS LOW IN SUSPENDED SOLIDS
(I.E., ≤ 5NTU) OR SIDE STREAM FILTERING IS
PRESENT (I.E. ≤ 25 NTU THEORETICAL).
TABLE 2 – COOLING SYSTEM SUSCEPTIBILITY TO LEGIONELLA RISKS
ISSUE
DEAD LEGS, SUPPLY/RETURN
HEADER DEAD HEADS, SEASONAL
CROSSOVER LINES
CONDITION
BIOFILMS, BIO-SEDIMENTS,
ANAEROBIC CONDITIONS
REMOVE
PROCESS
INLEAKAGE
AIR/GASES FROM
CHEMICAL OR FOOD PROCESSING
(VOC’S) AND VEHICLES NEAR
COOLING TOWER INTAKES
EMPLOY
BASIN
NONE,
EXHAUSTING
HIGH NUTRIENT LOAD POTENTIAL
DIRECT SUNLIGHT ABSORPTION BY
COOLING TOWER
®
CORRECTIVE MEASURE
UPPER
DISTRIBUTION DECK
DEAD LEGS OR BLOWDOWN
(HIGH VELOCITY FLUSH) EVERY 5 TO 7
DAYS
LOOP SUPPLY/RETURN HEADERS WITH 510% SLIP STREAM FLOW PROVIDED
COOLING WATER LOW IN SUSPENDED
SOLIDS OR BLOWDOWN EVERY 5 -7 DAYS.
SEASONAL CROSSOVER LINES AND
EQUIPMENT. PROVIDE 5-10% SLIP STREAM
FLOW PROVIDED COOLING WATER IS LOW
IN SUSPENDED SOLIDS OR INSTALL
ISOLATION VALVE AT THE FLOWING LINE
TAKE OFF WITH A BLOCK AND BLEED
VALUE ARRANGEMENT AND DRAIN THE
SEASONAL LINE AND EQUIPMENT
DETECTION AND CONTINGENCY
MITIGATION METHODS AS DONE FOR
TRADITIONAL CHEMICAL TREATMENT
PROGRAMS
REDIRECT EXHAUSTING AIR/GASES
A DESIGN CONSTRAINT
ENCLOSE WETTED EXPOSED AREAS WITH
HINGED COVERS THAT ALLOW FOR
ACCESS AND INSPECTION
TABLE 2 – COOLING SYSTEM SUSCEPTIBILITY TO LEGIONELLA RISKS
ISSUE
HIGH DRIFT AND AEROSOLS IN
COOLING TOWER AIR EXHAUST
CONDITION
DRIFT
ELIMINATORS MISSING OR
IMPROPERLY INSTALLED
OLD, LOW EFFICIENCY DRIFT
ELIMINATORS PRESENT

VISIBLE
COOLING TOWER INSPECTION OF
FILL, ELIMINATORS, BASIN,
DISTRIBUTION DECK
BIOFILMS, ALGAE,
SLUDGE, DEBRIS
ANAEROBIC/SEPTIC SMELLING
MUDS, H2S RELEASE UPON HC
ADDITION
CORRECTIVE MEASURE
CHECK
DRIFT ELIMINATORS FOR
PRESENCE AND CORRECT INSTALLATION.
REFIT REPLACE BROKEN ELIMINATORS
UPGRADE TO HIGHER EFFICIENCY DRIFT
ELIMINATORS
APPLY
AGGRESSIVE CLEAN
STERILIZATION PRECONDITIONING/FLUSH
OF RECIRCULATION SYSTEM
PAST/PRESENT BIOLOGICAL
CONTROL
BIOFILMS
PRESENT ON DRYING
COUPONS (I.E. SHEEN TO
TANNISH/BROWN COLOR
DEVELOPMENT)
>105 CFU/ML H.B.C.
> 106 CFU/CM2 H.B.C.
APPLY
HALOGEN IN USE WITHOUT
BIODISPERSANT
NOT
EFFECTIVE IN MINIMIZING
BIOFILMS
SEE
NON-OXIDIZERS IN USE NOT BASED
ON GLUTARALDEHYDE,
ISOTHIAZOLINE,
BROMONITROPROPANEDIOL, OR
DIBROMONITRILOPROPIONAMIDE
CHEMISTRY
LITTLE
SEE
®
TO NO EFFICACY
TOWARD LEGIONELLA CONTROL
ONLINE MODERATE
PRECONDITIONING STERILIZATION
TABLE 4 FOUR OXIDANT LEVEL
CONTROL AND TABLE 5 FOR ACCEPTABLE
BIODISPERSANT DOSAGES
TABLE 6 FOR CORRECT NONOXIDIZER, DOSAGE AND CONTACT TIME
REQUIRED FOR LEGIONELLA CONTROL
Site Survey Pretreatment/Precleaning Need Assessment
Question/Observations/Analytical Results
CFU/ml > 105 - 106, SRB’s, IRB’s, Mold Fungi: Present
> 1 inch of sludge in Cooling Tower Distribution Decks, spray
nozzle header dead ends blow off points and/or basin.
Visible biofilms in Cooling Tower, fill, basins, coupons, heat
exchangers (tubing, head box)
Deposits Greater than 10% LOI, 40% Moisture, 10 6 CFU/gm
aerobic, 104 anaerobic, or SRB’s, IRB’s, mold/fungi present
Surface films contain tanish brown coloration upon drying or
begin to curl up, like potatoe chips upon dehydration, > 10 6
CFU/cm2aerobic, > 102 CFU/cm2 anaerobic, or SRB’s, IRB’s,
Mold/Fungi present
CFU/ml, SRB’s, IRB’s or Mold, /fungi increase 4-6 hours after
biodispersant added.
Periodic spike increase in CFU/ml when no biocide is added.
System has experienced process inleakage presently or in the
past.
Addition of HCI to deposits release H2S
Addition of HCI to surfaces release fluffy coagulated cellulytic
materials
Legionella control has been poor or sporadic
Yes
No
Precleaning Determination
DEPOSIT ANALYSIS
<10% LOI
<40% MOISTURE
<104 CFU/CM2
<105 CFU/GM

NO SRB’S, IRB’S, MOLD

COUPONS TUBERCLATED WITH
HARD SINTERED CORROSION
PRODUCT AND SHINY SILVER
TUBERCLE BASE

HIGH % IRON
OFF LINE CLEANING OF
AFFECTED
EXCHANGERS FOR
TUBERCLE REMOVAL
AND REPASSIVATION,
IMPROVEMENT IN
CORROSION CONTROL
PROGRAM REQUIRED.
>10% LOI
>40% MOISTURE
>105 CFU/CM2
>106 CFU/GM

POSITIVE SRB’S,
IRB’S, MOLD
COUPONS/SURFACES
HIGHLY
TUBERCULATED AND
SHINY SILVER BASE
>10% LOI
>40% MOISTURE
>105 CFU/CM2
>106 CFU/GM

POSITIVE SRB’S, IRB’S MOLD

COUPONS AND SURFACES NOT
SEVERELY TUBERCULATED,
BASE NOT SHINY SILVER
ON LINE BIOFILM CLEAN-UP AND
STIFLING OF TUBERCLES – PLUG
APPARENT POROSITY, MIXED
BIO/CORROSION FOULING
LOW % IRON
ON LINE BIOFILM CLEANUP, BIOFOULING ONLY
Legionella Testing
Requirements
®
Survey Summary Requirements For Legionella Testing
Country
Testing Required
Frequency
Offline Cleaning And
Disinfection
Aust./NZ
Yes
Monthly
2 Consecutive
≥ 1000 CFU/ml
EU
Yes
Quarterly
≥ 100,000 CFU/L
France
Yes
Monthly
≥ 100,000 CFU/L
Spain
Yes
Monthly
≥ 100,000 CFU/L
Italy
Yes
Not Specified
≥ 10,000 CFU/L
Netherlands
Yes
Quarterly
(Monthly to
Yearly Risk
Based)
≥ 100,000 CFU/L
Switzerland
No
Quarterly
≥ 10,000,000 CFU/ml HPC
Singapore
Yes
Quarterly
≥ 1,000,000 CFU/L
Japan
Yes
Not Specified
≥ 1,000,000 CFU/L
UK
Yes
Quarterly
> 1,000 CFU/ml
USA
No
Not Specified
Not Specified
Canada
No
Not Specified
Not Specified
Direct Testing of Legionella

Frequency Consideration
• Prior to peak summer sterilization (i.e.
beginning/mid August) for seasonally operated
HVAC or after a sterilization.
• After cleaning of a confirmed cooling tower
sourced outbreak
• If a confirmed outbreak has occurred in the
area (≤3 km minimum)
• Three times per year of 24/7 Industrial process
cooling systems of higher risk noted earlier
®
Frequency of
Cleaning/Disinfection
®
Frequency of
Cleaning/Disinfection

Immediately prior to new system being
commissioned

If the system has been out of use for one month or
longer

If the system has been modified, entered or disturbed
in such a way to lead to contamination

If the cleanliness of the system is any doubt

If microbiological monitoring indicates there is a
problem

At least twice a year
®
Frequency of
Cleaning/Disinfection

Preconditioning/Disinfection
– End of Operating Season
– 2 per Year Minimum for 24/7 Systems

Disinfection Only
– At Peak Seasonal Demand
– Occurrence of Outbreaks in the Area
– Upon System Restarts of ≤ 4 weeks Idleness (≥ 3
Days?)’

Idle System of 1 Month or More to be Drained
®
Sterilization Only

Frequency
– During restart of idle/stagnant towers,
condensers, heat exchangers
– Seasonal restart of HVAC system, which was
preconditioned and sterilized the end of the
previous season
– Peak of summer cooling demand
(i.e. beginning of August).
– Known outbreaks in the area
– Biological dip slide counts exceed 105 – 106
CFU/ml. Visible slime (i.e. biofilm) present.
®
Actions Levels/Associated
Cleaning Disinfection
®
OSHA Technical Manual
(Section III: Chapter 7)
Legionella Counts
Action Level
Cooling Tower
CFU/ml
Domestic Water
CFU/ml
Humidifier
CFU/ml
1
100
10
1
2
1000
100
10
Where - AL1 – Online Cleaning and/or Biocide Treatment Improvement Required
- AL2 – Immediate Online Cleaning and/or Biocide Improvement
(Note: If Online Approach Does not Eradicate, then Off Line is Required)
Suggested Legionella Remedial Action Criteria
Legionalla
(CFU/ml)
Cooling/Tower
Evaporative
Condenser
Potable Water
Humidifier/Fogger
Detectable;<1
1
2
3
1-9
2
3
4
10-99
3
4
5
100-999
4
5
5
>1000
5
5
5
Actions –
1.
Review Maintenance
2.
Follow-up Analysis and Implement Action 1
3.
Implement Action 2, Conduct review of Direct and Indirect Bioaerosol Contact of
Occupants and Health Risk Status of Occupants May Lead to Increased Biocide
Applications or Online Clean
4.
Implement Action 3, Cleaning/Biocide Improvement is Indicated
5.
Immediate Biocide Improvement and Cleaning is Indicated Levels have a Potential for
Outbreak
© 1998, Pantheon Laboratories, Pathogen Control Associates Inc.
Implications of the Need for
Biocide Improvements

Action 3 - 14 Days After Action 2 Completed
– Nonoxidizers Review Dosing Schedule and
Amount Used vs. Contact Time (Feed/Bleed
Issues)
– Oxidizer – Semi-Continuous; Frequency and
Duration for 1 to 2 ppm FAC Applied. Minimum
0.5 – 1.0 ppm 4hours/24hours
– Oxidizer – Continuous; 0.2 to 0.5 ppm FAC go
to 0.5 – 1.0 ppm FAC
– Retest within 3-5 Days
Implications of the Need for
Biocide Improvements

Action Level 4 - 14 Days After Action Level 3 Completed
– Non-oxidizer Program May Require Oxidant Use At 1/Week in
Summer and 1 per 2 Weeks Winter at 1-2 ppm FAC for 1 Hour
CT (i.e. 2 Hour Run Time)
– Semi-Continuous Oxidizer may require either or both nonoxidizer or Biodispersant Once per Week
– Continuous Oxidizer at 1-2 ppm FAC may Require Either or
Both Non-Oxidizer or Biodispersant once per Week
– Non-Oxidizer or Biodispersant Addition Maybe Required Every
System Retention Time (Vol/BD Loss)
– May Require On-line Clean Within 30 Days
– Retest Within 3-5 Days
®
Implications of the Need for Biocide
Improvement

Action Level 5 – 14 Days After Action Level 4
Completed

On-line Clean within 7 Days of This State
-
Biodispersant Plus ≥ 5 ppm FAC for 6 Hours
OR
-
Biodispersant Plus ≥ 25 ppm FAC for 2 Hours
OR
®
-
Biosdispersant Plus ≥ 50 ppm for 1 Hour
-
Test 3-7 Days Latter – Poor Results Repeat or Go to Offline Approach
Implications of the Need for Biocide
Improvement
Off-line Cleaning

–
-
Pre Conditioning with
1.
Blowdown to ½ COC
2.
Biodispersant and Non Oxidizer for 24 Hours
Hyper Chlorination
1.
pH 7.5 – 8.0
2.
Biodispersant
3.
≥ 10 ppm FAC for 24 hours
4.
Drain and Flush
-
Post Conditioning of ≥ 10 ppm FAC for 1 Hour
-
Test 3-7 Days Latter – Poor Results Repeat or Go to Wisconsin
Protocol
®
Implications of the Need for Biocide
Improvement
Special Notes

1. Action Levels Are a Forward Progression
2. Upon Attaining Steady State Correction Move
Backwards on the Action Levels Assuring No
Return to Control State Loss
3. It is not Unusual to have to Repeat Online or
Off-line Cleans as Previous Suppressed
Bioflims, Sludge and Muds have now been
Conditioned/ Loosened for Release to the
Bulk Water
®
OSHA/Wisconsin Protocol
Confirmed Cooling Tower Source of Outbreak

1.
2.
3.
4.
5.
6.
®
Turn off tower fans
Shock dose chlorine donor to 50 ppm FAC
Add Biodispersant
Hold 10 ppm FAC for 24 hours
Drain cooling system and repeat steps 2 - 4
Inspect for biofilms. If present, drain and
mechanically clean.
OSHA/Wisconsin Protocol
Refill system and operate for 1 hour at 10 ppm FAC
Flush system
Recharge system with water treatment additives for
deposit, corrosion and biological control and return
to service
7.
8.
9.
Note test monthly:


®
Legionella ≤10 CFU/ml
HPC ≤10^5 CFU/ml
Action Levels of One JCAHO Facility Cooling
Tower Upwind from Building Air Intakes
Legionella
(CFU/ml)
Action Level
< 10
1
10 - 30
2
>30 - 100
3
>100 - 200
4
>200
5
Cooling Tower Design
Best Practices
®
Sand Filtration 5 Micron Media
Particle
Size
Microns
Percent
Of
Total
Before
Filtration
After
Filtration
Percent
Reduction
1–5
86.3
44,879,400
346,760
99.2
5 – 10
10.7
5,588,600
36,920
99.3
10 – 25
2.7
1,410,600
24,060
98.3
25+
0.3
126,800
8,760
93.1
Totals
99.0
52,005,400
416,500
99.2
•Finer
the Size, more Surface Area and Nutrient Value
•Typical Size of
Bacteria – 0.2 – 0.45 Micron
Spores – 0.1
Micron
Protozoa - >50
Micron
Diatoms - >20
Micron
Algae - >100
Micron
•1
Micron = 0.00004 (4 x 10 ^ -5) Inches
Considerations for Filtration

Total Suspended Solids Leading to
– UDC
– Loss of Biofilm Control or High Biocide Demands
for Bulk Water Biocontrol
– Mass Balance Verification of Scale and/or
Corrosion Inhibitor Adsorption Losses
– Settled Solids Harboring Bioactivity, Higher Life
Forms
– Periodic Biocount Spikes for No Apparent Reason
– Presence of Visual Biofilms and Agglomerates
®
Suspended Solids Control Target
(First Case Approximation)

As per Tower Fill Manufacturers
Recommendations

Tower Sump Sludge < 1"

Tower Distribution Deck/Lateral Sludge <⅛" - ¼"

Tower Fill Deposit Loadings ≤ 0.00187 lbs./ft3/day

Filtration or Chemical Dispersants for TSS Values
Greater than 10 ppm in the Cooling Tower Water

Ensure Cost Effective Biocontrol is Practiced
– Planktonic - ≤ 103 CFU/ml
– Sessile - ≤ 105 CFU/cm2
®
Maintenance
Considerations
®
C.T.I. Maintenance Considerations

Filtration Equipment
– Periodic Media Cleaning and Disinfection
-
Once per Year
-
CFU/ml Counts Outlet > Inlet After Backwash
- Alkaline Detergent Air Lance/Bubble Mixing for
2 to 4 Hours – Backwash
- Chlorination at 100 ppm FAC Air Lance/Bubble
Mixing for 2 to 3 Hours - Backwash
®