Under Deposit Corrosion in Cooling Water

Under deposit corrosion in cooling systems have been one of the most prevalent problems in our industry.  It is also one of the least understood problems with field level engineers and clients alike.

Deposits occur in cooling systems due to colloidal sediment, environmental debris, scale, old corrosion deposits re-depositing on metal surfaces and of course biofilm.

When deposits form on metal surfaces, the corrosion inhibitors added to systems simply cannot do their job, since they cannot get to the metal surfaces they are supposed to protect.  Further, a dissimilar surface is set up on the metal providing the makings of a corrosion cell.

Scale formations provide a dissimilar surface and allow for the anode/cathode corrosion cell to start.  Further, scale insulated the metal surface from the corrosion inhibitors from protecting metal surfaces, most likely on the cathode surface.

Environmental debris such as garden variety dirt and organic material also presents a dissimilar metal surface allowing a corrosion cell to start, same as scale formations.  Environmental debris also provides a great start to both scale and biofilm formation.  Cooling system components most in danger from environmental debris are chillers with enhanced tubes.  Enhanced tubes are already prone to corrosion due to their rifled nature.  Cooling tower systems with enhanced tubes should all be filtered through a sand or multimedia filter to protect the rifling of these tubes.

Biofilm:  Causes the same dissimilar metal surfaces as noted above.  An added feature of microbiological corrosion is the acidic nature of the biofilm wastes.  pH’s of the underside of a biofilm has been measured as low as 2!

How to prevent under deposit corrosion?

 Make sure flow rates in all areas of your system are high enough to prevent sediment from settling on piping.

  1. Avoid intermittent flow conditions.
  2. Clean up all existing deposits.
    1. Descale fouled systems
    2. Remove old biofilm
    3. Physical remove old corrosion products where possible
  3. Consider an appropriate filter for your system.
  4. Keep your biocide program up and consider a bio dispersant, especially in chiller systems with enhanced tubes.

These deposits can be virtually eliminated from most systems.  Be sure to evaluate your systems to determine appropriate cures.

Keith Morgan/ CWT/ Upstate division

Legionella exposure sickens 2, causes closure of Waco YMCA

<i>Legionella</i> exposure sickens 2, causes closure of Waco YMCA

Health authorities in Waco, Texas, are investigating two cases of Legionnaires’ disease believed to be connected to the Waco Family YMCA.

Legionnaires’ disease is a severe type of pneumonia or lung infection caused by Legionella bacteria, which are contracted by inhaling microscopic water droplets in the form of mist or vapor.

“Exposure to the Legionella bacteria may have occurred at the Waco Family YMCA,” Rodney Martin, president and CEO of the YMCA of Central Texas, was quoted in a notice to visitors.

While the facility remains open to members and guests – after consultation with the Waco-McLennan County Public Health District (WMCPHD) – officials closed the whirlpool area, which is adjacent to an indoor pool.

“The Waco Family YMCA will remain open to members, guests and program participants as all other areas of the Y are accessible, including the pool, gym, fitness, group exercise spaces and more,” the organization said. “The restricted area will not affect the operations of the Y or its ability to serve its guests.”

The source of the bacteria has not been identified.

“We have been in contact with both the Waco-McLennan County Public Health District as well as the Center for Disease Control and are following their recommendations,” Martin wrote in an e-mail. “We have also contacted an outside expert to complete testing of the Y’s water.”

Health officials work backward
Kelly Craine, public information officer for the WMCPHD, said once the department was notified of the cases, its staff began “working backward” to discover a common denominator between the patients and pinpoint a possible source of their infection.

“The hot tub has been closed, and it is the only area that’s been closed,” she said. “Because of the mist, you always want to look at the hot tub as a possible suspect.”

YMCA visitors may need to take action
Health district officials said they believe the two patients contracted the Legionella between Feb. 4 and Feb. 21.

If you are a member, visitor or employee of the YMCA, located at 6800 Harvey Road, and you used the whirlpool, swam in the pool or traveled through the whirlpool or pool area this month and are feeling pneumonia- or flu-like symptoms, you should seek care from your health-care provider, according to Craine.


Four Legionnaires’ disease cases linked to Crookston hotel


CROOKSTON, Minn. — The Minnesota Department of Health is investigating four cases of Legionnaires’ disease linked to a hotel in northwestern Minnesota.

Four people reported getting sick between Jan. 22 and Jan. 27 after staying at the Crookston Inn and Convention Center. None of them stayed in the hotel overnight and visited the hotel for different occasions, the Department of Health said in a news release.

Legionnaires’ disease is a type of pneumonia caused by Legionella bacteria usually spread to humans by inhalation of contaminated water mist — often from sources like plumbing systems, air duct moisture and hot tubs. It is not spread from one person to another under normal circumstances.

State health officials are working with the hotel to find out what may have caused the outbreak. Based on existing evidence and past outbreaks, the Department of Health currently believes the outbreak may have originated in the hotel’s spa, which is currently closed pending lab test results.

The hotel is notifying people who stayed there between Jan. 14 and Feb. 13 that they may have been exposed.

Symptoms of Legionnaires’ disease include fever, muscle aches, shortness of breath and loss of appetite.

Closed Loop Systems Treated With Glycol

Closed Loop Systems Treated With Glycol

A variety of heat transfer fluids are used to provide freeze protection for industrial equipment and HVAC closed-loop heating and cooling systems.  These fluids may be used in systems that operate anywhere between -60°F to 300°F.

Many heat transfer fluids are glycol-based, containing either ethylene glycol or propylene glycol.  Additives may include corrosion inhibitors (high concentrations of phosphate or nitrite), alkalinity stabilizers, and in some cases – fluorescent dyes – where leak detection is desired.

Operators of these closed-loop systems can often experience long-term and difficult-to-reverse problems resulting from misapplication of these glycol-based solutions.  Glycol degradation and system deterioration can result if the wrong glycol is used or if low concentrations are present.  Problems associated with glycol degradation are:  runaway corrosion, persistent microbiological fouling and deposition.


Ethylene Glycol:  Most common for general industrial use,  Can be toxic.  Lowe viscosity (less energy required for pumping) and better heat transfer properties than propylene glycol.

Propylene Glycol:  Used in quick-freezing of wrapped foods and in hospitals where there is potential for contamination of potable water systems.  More environmentally friendly than ethylene glycol because of its lower toxicity.  Higher viscosity (less energy efficient) than ethylene glycol.

 Automotive Antifreeze:  Not suitable for HVAC and industrial applications because they contain silicate corrosion inhibitors which may cause fouling and pump seal failures.

Inhibited vs. Uninhibited Glycol:  Only inhibited glycols are recommended for use in closed systems.  Manufacturers and water treatment professionals add inhibitors (phosphate or nitrite and alkalinity) to minimize corrosion and to prevent glycol degradation.  Over time, uninhibited glycol will form acids, making the solution very corrosive (4 ½ times more corrosive than plain water).

 Glycol Stability:  When properly maintained, inhibited glycol solutions can last 20 years or more.  Uninhibited glycol solutions can be expected to break down in 2-3 years.

 Refractometer:  Measures percent glycol.  Accurate and portable method for both ethylene and propylene glycol.

Glycol quality should be monitored annually.  This testing is done to detect any symptoms of glycol degradation – such as:

  • pH depression (as low as 5.0) caused by production of organic acids
  • Formation of formaldehyde, ethanol, methanol and CO2.
  • Presence of a strong septic odor
  • Severe corrosion of mild steel and copper components (resulting soluble copper will cause galvanic corrosion on steel).
  • MB infestation particularly in stagnant areas.

Methods For Handling Degraded Glycol:  Based on manufacturers’ recommendations, the system should be drained, thoroughly flushed with untreated water, and recharged with inhibited glycol.  Salvaging degraded glycol is not recommended.  If microbiological activity is detected, biocides can be used after the flushing process and PRIOR to recharging with fresh glycol.

 Disposal Regulations: Ethylene glycol is classified as an extremely hazardous substance.  The POTW or wastewater treatment plant receiving the discharge should be contacted and written permission should be obtained before discharging water containing ethylene glycol.  Possible alternatives are:  disposal through a waste contactor or recycling through a solvent recovery vendor.

There are no requirements, as defined by SARA, for disposal of propylene glycol; however, you should check with the local municipality prior to disposal.

Recommended Treatment Practices:

 Maintain a minimum concentration of 30% inhibited glycol.  This concentration will ensure adequate corrosion and biological protection.  Supplemental treatment is not required.

  1. Monitor yearly by having the glycol provider test the glycol integrity and inhibitor concentration.  This testing will allow for any corrective actions to be initiated.
  2. If uninhibited glycol is used, you can apply a corrosion inhibited such as Metro DuBoth NB35 at recommended treatment levels.  Also, maintain close vigilance on pH, microbiological activity, iron and copper concentrations and corrosion rates.
  3. Manufacturers specify water impurities be limited to these maximum values:
    1. Chlorides……………..25 ppm
    2. Sulfates……………….25 ppm
    3. Calcium………………50 ppm
    4. Magnesium……………50 ppm

Pre-diluted glycol solutions can be purchased from manufacturers – if acceptable water quality is not available.

  1. Monitor yearly by having the glycol provider test the glycol integrity and inhibitor concentration.  This testing will allow for any corrective actions to be initiated.
  2. If uninhibited glycol is used, you can apply a corrosion inhibited such as Metro DuBoth NB35 at recommended treatment levels.  Also, maintain close vigilance on pH, microbiological activity, iron and copper concentrations and corrosion rates.
  3. Manufacturers specify water impurities be limited to these maximum values:
    1. Chlorides……………..25 ppm
    2. Sulfates……………….25 ppm
    3. Calcium………………50 ppm
    4. Magnesium……………50 ppm

Written by: Mark Botsford

First 2019 outbreak results in death in Pennsylvania By News Services 

The year’s first Legionnaires’ disease outbreak has claimed a life after two patients at a Richlandtown, Pennsylvania, care center were confirmed with the deadly respiratory illness, according to WFMZ-TV.

The two individuals, who came to Phoebe Richland Health Care Center from two area hospitals, were diagnosed on Jan. 2 and Jan. 5. The patient who passed away died due to multiple contributing health factors, according to a statement released by Phoebe Richland officials. The other resident is in stable condition and undergoing treatment.

No information was provided on either patient.

“The health and well-being of our residents and staff are Phoebe’s top priorities,” the Phoebe Richland statement read. “In the last few days, two residents who were recently admitted to Phoebe Richland Health Care Center were diagnosed with Legionnaires’ disease.”

Legionnaires’ disease is a severe form of pneumonia — that is, lung inflammation usually caused by infection – according to the Mayo Clinic. The disease is caused by Legionella bacteria, and most people are infected by inhaling the bacteria in the form of microscopic water droplets, usually in the form of mist or vapor.

Legionnaires’ disease is not contagious – that is, it cannot be passed from person to person. If it is caught early enough, it can be treated with antibiotics.

Phoebe Richland is working with the Bucks County Health Department to identify whether the facility is the possible source of the Legionella that infected the residents.

“We have engaged an outside vendor to conduct specialized water testing beyond our annual testing, which is performed in accordance to our water-management policies,” the statement read. “In the event that our campus is determined to be the source of the Legionella bacteria, we are taking measures to locate and eliminate any potential source of Legionella.”

Phoebe Richland is located at 108 S. Main Street in Richlandtown, about 50 miles north of Philadelphia. The facility offers long-term care, short-term rehab, memory support services, and respite care.

A mild form of Legionnaires’ disease — known as Pontiac fever — can produce signs and symptoms including a fever, chills, headaches and muscle pains. Pontiac fever, however, doesn’t infect the lungs, and symptoms usually manifest within two to five days.

University of Wisconsin outbreak hits 11

Six new illnesses have been identified in the Legionnaires’ disease outbreak at University Hospital in Madison, raising the case count to 11, according to UW Health officials. The outbreak was first reported on Nov. 28 when four cases of the deadly respiratory illness were confirmed. A fifth case and a fatality were announced the next day.
The new illnesses were not unexpected as officials expected the count to grow, due to the exposure window to Legionella, the bacteria that causes Legionnaires’ disease. Symptoms can present up to 14 days after exposure, and other patients could present symptoms up until Dec. 12, according to a hospital press release.
Four of the patients remain hospitalized, while six have been discharged or treated as outpatients. Their conditions are considered stable, and an antibiotic treatment protocol is working as expected.
One patient, who had been hospitalized with multiple, serious health problems, died last week. At the time of that pronouncement, Lisa Brunette, UW Health direction of media relations, said the “death was not unexpected.”
Hyperchlorination of the hospital’s hot water system has been successful in the reducing the bacteria, but monitoring at multiple sites within University Hospital is ongoing.
“We are confident the hyperchlorination worked as expected,” said John Marx, UW Health senior infection control practice specialist. “An aggressive program of monitoring and screening is in place to ensure the system is functioning as designed. Our commitment to the safety of our patients is unwavering.”
UW Health is working with the Wisconsin Division of Public Health (DPH) on mitigation and testing efforts and have extended an invitation to the Centers for Disease Control and Prevention (CDC), asking them to act as an additional expert resource.
Incubation period still active
If you are a patient, visitor or employee of University Hospital and are feeling pneumonia- or flu-like symptoms, you should see your health-care provider out of an abundance of caution.
By News Services on December 8, 2018

Legionella Found At All But 3 West Orange Schools

Legionella Found At All But 3 West Orange Schools: Officials

WEST ORANGE, NJ — First they were found at town hall. Then they were found at a half-dozen other municipal buildings. Now, less than six weeks after Legionella bacteria was discovered in the water at Redwood Elementary, West Orange officials have found additional samples of the hazardous pathogen at all but three of the district’s schools.

On Wednesday, West Orange Public School District administrators provided an update on testing that’s been taking place at all 12 schools for Legionella bacteria, the organisms that lead to Legionnaire’s Disease, a severe form of pneumonia commonly found in found in potable and non-potable water systems.

Test results for each individual school can be seen here. Read Superintendent Jeff Rutzky’s letter to parents and guardians here. Updated district statements about the testing can be seen here.

The district initially began testing for the bacteria at Redwood Elementary School last month after a parent whose child was attending summer camp there reported that her child was sick with what the doctor said could be Legionnaire’s Disease. The child was ultimately determined not to have the disease, Rutzky said.

However, officials began remediation efforts at the school after test results showed four of 15 samples had “very low levels of Legionella bacteria” on Aug. 14.


On Aug. 30, New Jersey American Water tested sinks and water fountains at Redwood Elementary School for coliform bacteria. The results were satisfactory in accordance with the Safe Drinking Water Act standards, school officials said.

Even though the Redwood Elementary School samples met the standard, OMEGA Environmental was hired to perform a disinfection procedure using a hyper-chlorinated solution on Sept. 10 and 11, officials said.

The procedure included:

  • “chlorine is pumped into the hot water heater and remains in the hot water tank for four hours to eliminate any bacteria”
  • “chlorine is then pumped through the hot water piping system and remains in the system for fourteen hours to eliminate any bacteria”
  • “chlorinated water is drained from the hot water tank and hot water piping system and flushed with fresh water”
  • “water samples are drawn and retested after the hyper-chlorination procedure to verify that the water again meets the Safe Drinking Water Act standards”

Officials also took the following steps at Redwood Elementary:

  • “installing filters on the water sources that tested positive”
  • “replacing faucets in the affected areas”
  • “proactively and temporarily covering all water fountains despite the fact that the Legionella bacteria only presents a risk from exposure to airborne droplets and not from drinking affected water”
  • “removing, cleaning and sanitizing all aerators (screens) in all rooms”
  • “where possible, changes in the plumbing systems will be done to minimize the potential for future bacterial growth”

West Orange school officials then began the process of testing the district’s other facilities for Legionella, including all 12 schools, the Central Office and the Bus Depot.

Samples for Legionella bacteria were positive in the Administration Building and all schools except Liberty Middle School, Betty Maddalena Early Learning Center, and Kelly Elementary School, officials announced Wednesday.

“All affected schools will undergo the same remediation as Redwood Elementary School by Omega Environmental, followed by retesting by Garden State Environmental,” school administrators said. “Water bottles should be available at all schools until testing and remediation is completed.”

To complete the process, the remediation is being carried out on weekends, administrators said.

The remediation schedule follows below:

  • Mt. Pleasant had the chlorination process completed on Sept. 19 and was retested for the Legionella bacteria on Sept. 24.
  • St. Cloud had the chlorination process completed on Sept. 22 and will be retested on Sept. 27.
  • Hazel will have the chlorination process completed on Sept. 28 and 29. Retesting will be done approximately four days after the chlorination process.
  • Gregory, Washington and the Administration Building will have the chlorination process completed on Oct. 5 and 6, Oct. 12 and 13 or Oct. 19 and 20. Retesting will be done approximately four days after the chlorination process.
  • Edison and Roosevelt will have the chlorination process completed on Oct. 26 or 27 or Nov. 2 and 3. Retesting will be done approximately four days after the chlorination process.
  • West Orange High School will be completed on Nov. 8 to 11. Retesting will be done approximately four days after the chlorination process.

“It is important to note that there are no confirmed cases of Legionella in West Orange,” Superintendent Rutzky said Wednesday. “We will continue to be diligent in our approach to remediate the water sources that tested positive for Legionella bacteria and proactive in completing the process as quickly as possible.”

School district administrators have been coordinating their responses with workers at the town Health Department, who have been conducting their own Legionella testing and remediation at several buildings, including Town Hall, Lafayette Park, O’Connor Park, Fire Headquarters, Firehouse No. 2, Firehouse No. 4 and Police Headquarters.

West Orange Director of Health Theresa DeNova previously provided the following information about Legionnaire’s Disease:

“It is not contagious, person to person… it is not airborne… it cannot be contracted by drinking or touching water… and the way it is contracted is by inhaling contaminated water mist.”

New Jersey American Water previously released the following statement about the situation in West Orange:

“Providing safe water is New Jersey American Water’s number one priority and a responsibility we share with all our customers. Although the drinking water we deliver is treated and meets all federal and state water quality standards and requirements, the quality of that water can change once it leaves our pipes and enters domestic plumbing systems. When we became aware of the issues the Township of West Orange experienced with Legionella in the plumbing infrastructure of its Municipal Township Building, we began proactively working with Mayor Parisi, his staff, health officials and town consultants to provide expert guidance and assistance as the town works to remedy this situation. We are committed to helping the Township resolve this issue as they work to disinfect and upgrade their building systems to ensure a healthy and safe work environment for their employees.”


Why Clean your Cooling Tower?

You may be asking yourself “I have a water treatment plan in place, why do I need to clean my Tower?”  There are multiple reasons to perform annual, or semi-annual tower cleanings.  The first being it is mandated by law in some states to maintain compliance.  New York State has made an annual physical tower cleaning mandatory with the regulations adopted in August 2015.

Besides legal compliance, another reason is to maintain system efficiency.   As a cooling tower operates, wind-blown dirt and debris can deposit into the basin of the cooling tower.  As the debris settles, it creates a shelter for microbiological organisms.  Once this occurs, the biocide cannot reach these organisms, and a corrosion cell then forms.   This debris can also begin to clog heat exchangers, strainers etc.  When this occurs heat transfer ability does drop resulting in increased power usage to run fans, chillers etc.  It can also cause premature failure to piping and the tower itself through microbiological induced corrosion.

The other reason, which is the most important, is for public health.  The regulations put forth by New York was in direct response to a Legionella outbreak within New York City.  As stated above, debris and bio-film can prevent a biocide from doing its job and reducing the risk of bacteria becoming airborne in the water vapor.

These are just a few reasons why the industry best practice and OSHA and ASHRAE 188 standard is semi-annual cleanings.

Is Superheating a Potable Water System After Positive Legionella Results Effective?

You’ve just received your Legionella analysis and the results show percent positivity above 30%.  What do you do?  You decide to superheat and flush the system by raising the temperature of the water above 140 degrees (also known as thermal eradication).  How effective is this procedure?  You won’t know until the retest results come back.  You receive the results and they are good, no positives.  The next round of testing approaches, the samples are collected, the results are in and you’ve got more positive Legionella results!  Why?   The answer is because after superheating the water, the biofilm is still there, you have not removed it; what you have done was kill whatever was in the bulk water, but unfortunately the biofilm is still there.  The organism thrives on the biofilm, it’s their nutrition, it’s what they live on.  Superheating and flushing will not penetrate and remove the biofilm.  If you don’t penetrate and remove as much of the biofilm as possible, you are going to continue in a vicious cycle of superheating and flushing, testing, and receiving positive Legionella results.

Now what do you do?  Should you superheat and flush again?  Should you try something different?  Your water treatment company suggests performing a chlorine dioxide disinfection.  What is chlorine dioxide?  It’s a chemical compound that consists of one chlorine atom and two oxygen atoms, it creates a gas that dissolves in water.  Once injected into the water system it will begin to penetrate and destroy biofilm.  There is never a guarantee that Legionella will not return after a chlorine dioxide disinfection, however, by using chlorine dioxide you have greatly increased the chances of removing bio-film and the source of the Bacteria, as opposed to super-heating which only provides superficial results.

Image result for potable water

Microbiological Control in Cooling Towers

From the water treatment industry’s perspective, the practice of controlling the proliferation of microbial fouling in HVAC/Industrial cooling water systems has traditionally been focused on keeping algae, slime and fungus in check.  Without proper control, organisms will colonize, grow, and turn into biomass and biofilm.  Displaced biomass can lead to restrictions in flow, loss of heat transfer and other serious water-borne problems.  In addition, a longer-term challenge is that accumulated bacterial slimes (biofilm) will lead to microbiologically influenced corrosion, metal loss and system failure.  Also, due to recent regulatory developments, the industry now has another objective to contend with.  This is to reduce the potential formation of disease-bearing organisms such as Legionella Pneumophila.  So, effective microbial control is at the center of overall cooling system performance as well the health of building occupants.

Cooling tower owners have numerous tools at their disposal.  These tools include application of chemical biocides, cooling tower chemical disinfections, and the selective use of mechanical support methods.  Among the mechanical support methods owners can rely upon we find deck covers (to shield sunlight), recirculating water filters (sand or media) to remove suspended solids continuously, basin cleaning filters to keep pans deposit free, and even air-intake screens to prevent additional dirt loading.  Cooling water biocides are applied routinely and typically involve the use of two different product categories – oxidizing and non-oxidizing micro-biocides.  These materials are designed to destroy existing organisms and also prevent new ones from growing.  The strategy of using two separate chemical micro-biocides is to ensure that cellular destruction is complete, and that strains do not develop immunity to resist treatments.

Owners working with industry professionals have numerous monitoring tools at their disposal.  Cooling tower inspections should be coupled with the use of microbiological testing. Micro testing is part of effective Water Management Plan development and includes testing for halogen reserves, bacteria and cellular activity, as well as specific testing for Legionella.  Best practice might also incorporate the use of bio-film detection strategies.  In conclusion, microbiological control of Industrial and HVAC cooling waters requires careful planning and resource allocation.  An appropriate selection of the tools now available to building owners can be selected and implemented to prevent problems, preserve capital equipment, and ensure the health of building occupants.


John D. Caloritis, CWT

Technology Director

The Metro Group, Inc

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