Assessing Water Quality In Your Facility
Water plays a key role in every building and facility. We use water for drinking, cleaning, in spas and pools, for fire suppression, landscaping, heating and cooling, and in a wide variety of manufacturing and production processes.
Most of us take water for granted; it’s always there when we need it. You turn on a spigot or valve and you get a steady stream. What more is there to know?
Water is no simple subject. And although it may all look the same, it is not. The quality and what’s in water can vary greatly from area to area and may change throughout the year if the primary water source changes. These changes can have major, minor, or no impact, depending on what water is used for in a facility. And that’s the bottom line. How water is used determines what level of quality or purity is required. If you’re only watering the grass, your concerns are much less than if you are drinking, bathing or making soda pop. When water is used for heating and cooling purposes we have a different set of concerns than if the water is used to clean printed circuit boards or computer chips.
Water is widely used for heating and cooling purposes in all types and sizes of facilities. In this article our primary focus will be the testing and treatment of water as it relates to heating and cooling systems, such as boilers, heat pumps, condensers, cooling towers and piping.
Why Water Analysis And Treatment Is Necessary
Heating and cooling systems operate at higher efficiency when the water is properly treated. One of the most common examples is a loss in heat transfer efficiency when scale builds up on the tubes or pipes in a condenser, boiler or other equipment. You can easily lose as much as sixty percent of a condenser’s efficiency due to scale build up.
If you don’t treat the water, the life of your heating and cooling systems will be considerably shortened. Instead of getting 20, 30 or 40 years of useful life, you can begin getting leaks in as little as 3 to 5 years. This is especially true with cooling towers and open loop systems where evaporation leads to concentrations of whatever minerals and impurities are in the source water or are added through the process of aeration.
Using a balanced water treatment program will reduce water consumption and sewer costs. In many cases water and treatment chemicals can be reused three to five times or more until they reach a cycle of concentration that requires blow down or bleed off to clean out the concentrated water and replace it with fresh.
Bacteria, viruses, molds, fungi, algae and slime will grow in water that is exposed to the air if it is not disinfected in some way. This growth will affect overall equipment efficiency and can clog pumps, filters and other components.
Another issue is health. Most everyone has heard of Legionnaires Disease and most know that it has been traced to the water in cooling towers and other locations that are open to the atmosphere and have standing warm water. Again, if proper treatment is not provided this disease and others will grow in open loop circulation systems.
How to Assess Water Quality
Testing is required to identify the content of the water you purchase. The first step is to request that your local water supplier provide you with a “water chemistry make-up” or “profile” of the water supply. This will tell you about the water on the date it was tested. With this information you can work with a water treatment contractor or service company to design a water treatment program that will meet your specific needs. They should also provide some on-site testing support and training so that your staff can monitor the water periodically and see that the appropriate chemicals are added either manually or automatically when and where they are needed.
The hardness content of your water will depend to a large degree on its source. If it is ground water, or ground water under the influence of surface water, coming from a well or wells, it will probably have a high mineral content. If it comes from surface water sources such as streams, rivers, lakes or springs, it may have a lower mineral content, but may contain more particulate and micro-organisms, especially during the spring months when run off is heavy.
According to Christopher Lee, General Manager of Technical Services for Clean Water Systems Northwest in Sumner, Washington, “The goal is to evaluate water chemistry and match available technology to the needs and application of the user. Sometimes it’s inexpensive and in other situations it can be very costly. If water plays a key role in a business, part of the site selection process should include a water chemistry profile so you don’t end up with expensive surprises at the last minute.”
Why Water Needs Treatment
The dissolved solids, suspended matter, and gases found in water are impurities that will have a harmful effect on heating and cooling systems if they are not treated. You cannot see dissolved solids, but they are present in the form of ions that carry a negative or positive charge and combine with other chemicals to form new chemical compounds that can attach to and attack metal surfaces.
Compounds that cause water hardness are some of the most troublesome as they collect on metal surfaces and form a heat absorbing and insulating scale. This is common in boilers, heat exchangers and piping and is caused by such compounds as sulfates and carbonates of Calcium and Magnesium.
Suspended matter has not dissolved and floats on the surface or in the water. It consists of small particles of sand, clay and mud as well as organic vegetable matter such as very small particles of leaves and twigs. Suspended matter will form sludge deposits in the bottom of boilers and cooling towers and can plug tubes reducing heat transfer that can cause overheating and loss of efficiency. Organic matter will cause foaming and needs to be removed or controlled with anti-foaming agents.
Dissolved gases that are a problem are Oxygen and Carbon Dioxide, which can cause corrosion and pitting in tubing and piping of a heating system. Free Oxygen and Carbon Dioxide are removed by venting in the system and dissolved Oxygen can be removed by addition of chemicals to the water.
The pH value of water is very important; the more acidic it is, the faster corrosion will occur. If water is too alkaline foaming will occur. The goal is to keep heating system water slightly on the alkaline side of the pH scale, but not so high that foaming becomes a problem.
A complete water analysis will provide information on hardness, Chlorides, pH, total dissolved solids and alkalinity. With this information a knowledgeable and trained professional can determine and recommend an appropriate water treatment program that will help keep systems operating efficiently and safely.
Water Testing
To determine the nature and amount of impurities in heating system water, a sample of the water must be taken and various tests performed on the sample.
pH is one of the most common and easiest tests to perform. This uses chemically treated paper that indicates by color the pH of the solution being tested. pH can also be determined by use of an electronic testing meter that senses Hydronium ions in solution.
A water hardness test is used to determine the amount of impurities and salts such as Calcium and Magnesium. To determine how much of these mineral salts are present a water sample is subjected to a titration test with a chemical that binds up the Calcium and Magnesium.
There are two types of alkalinity tests. One is the Phenolphthalein Alkalinity Test and the other is the Total Alkalinity or Methyl Orange Test. Each test is used to determine what type of alkalinity is present in the water and is based on a color change that takes place as different test solutions are added to a measured water sample.
Other tests that may be performed include:
- Dissolved Solids Test
- Phosphate Test
- Sodium Sulfite Test
- Chloride Test
For accuracy and safety it is recommended that the above tests be performed by a technician with experience in water chemistry and testing. Most water treatment suppliers can assist.
Water Treatment
There are many ways to remove impurities from water prior to its being used in a facility system or a manufacturing process. The process used to purify or condition water depends on many factors, some of which include:
- End use for the water and its disposal
- Cost – it may be more economical to treat water with internal methods than to pre-treat and in many cases both options must be utilized to obtain the desired results
- Volume and quality of water needed
- Temperature and pressure
Some common water pre-treatment equipment used in commercial and industrial facilities is listed below:
- Softeners: Removes minerals that cause hardness
- Demineralizers: Removes all dissolved minerals
- Distillers: Removes all dissolved and suspended solids
- Aerators: Removes Carbon Dioxide and Hydrogen Sulfide
- Filters: Removes suspended solids
- Clarifiers: Removes suspended solids
- Deaerators: Removes Oxygen and dissolved gases
- Dealkalizers: Removes all alkalinity
- Reverse Osmosis: Removes dissolved salts and minerals
- Lime Process Softeners: Removes Calcium and Magnesium hardness and Bicarbonate and Carbonate Alkalinity
- Ultraviolet Light: Kills bacteria and micro-organisms and reduces organic Carbon
- Ozone: Kills bacteria and micro-organisms and reduces organic Carbon
- Deionization: Removes almost all inorganic impurities and minerals
- Degassifier: Removes Carbon Dioxide
Chemical Treatment
The most common methods of treating or conditioning water are with additive chemicals that allow the water to act in ways that are more in line with the users’ needs.
Even though water is often pre-treated in some manner, on-going internal treatment of the water is needed once it is in the heating and cooling system.
Chemicals are added to obtain specific performance characteristics; additives are frequently used for the following reasons:
- Disinfection
Microbiocides of different types are added over a period of time to kill different organisms that may be found in cooling systems. This is not a problem with boilers as the water is at such high temperatures that all microorganisms are killed and the water is not open to contamination from the air. - Scale Control
One approach is to add third generation polymers to the water to keep surfaces clean and modify scale crystallization so scale particles can’t interlock and stick together and instead stay in suspension to be flushed out during bleed off or blow down of the system.
Another approach is to use a phosphate-based system that causes Calcium and Magnesium carbonate to drop out of the water as sludge in the bottom of the boiler which is then removed during blow down. - Corrosion Inhibitors
Sulfite and pH adjustment systems add chemicals to the water that prevent corrosion. These chemicals keep the water slightly alkaline, remove excess Oxygen and coat metal surfaces with a protective layer that actually isolates the water from the metal. - Sludge Removers
Polymers are added to the water that act as dispersers in that they wrap themselves around impurities and keep them in suspension so they will be flushed out of the system during blow down or bleed off cycles.
Manual Cleaning Of Cooling Towers
It is important to note that cooling towers need a good manual cleaning twice a year since they collect a large amount of soil and other debris from the air. A high pressure washer is a good piece of equipment for this application. A respirator, goggles, rubber gloves and other appropriate safety protection is required for anyone assigned to this task.
Product And System Costs
Chemical treatment costs range from $20 to $40 per gallon, with some concentrates using as little as one gallon of treatment per 72,000 gallons of make up water.
Automated systems that use conductivity sensors can be added to a single cooling tower for approximately $1000.
According to Steve Hammatt, Director of Technical Services for Chem-Aqua, a Division of NCH Corporation in Irving, Texas, “Any way you look at it, treatment and prevention are always far less costly than repair, restoration or replacement. Don’t fool yourself by looking only at the price per gallon of a product. The real cost savings is in what a product does for you.”
Future Trends
Products are evolving along with automated systems for monitoring and accurate dispensing of highly concentrated products. In concentrations of three to ten parts per million, you simply can’t get consistency with manual mixing.
As with all chemicals the trend is toward safer products that are less hazardous to use. One example is a glycol replacement that doesn’t eat metals and costs considerably less.
There is a lot more interest these days in water quality and how it impacts building occupants, systems and manufacturing processes. The technology is now available to test, monitor and do something about problems that only a few years ago we didn’t even know existed because we didn’t understand them. One example is the problem of lead and copper leaching out of plumbing in older buildings. Now we can test for such hazards, pre-treat the water and install plumbing systems that are safe for all uses.
