Everything you Need to Know About Cooling Tower Blowdown
Cooling tower blowdown refers to the process of discharging a portion of the circulating water from a cooling tower to control the concentration of dissolved solids and other impurities in the cooling water. The blowdown helps maintain the water quality within acceptable limits and prevent the buildup of scaling, corrosion, and fouling in the cooling system.
In this blog we will look at the purpose of cooling tower blowdown, blowdown methods, blowdown rate, blowdown treatment methods and blowdown disposal.
Purpose of Cooling Tower Blowdown
Cooling towers continuously evaporate a portion of the circulating water to remove heat from industrial processes or air conditioning systems. As water evaporates, impurities and dissolved solids become more concentrated. Blowdown is necessary to remove some of these concentrated impurities and prevent their accumulation.
Dissolved minerals in the cooling water, such as calcium and magnesium, can precipitate and form scale deposits on heat exchange surfaces and cooling tower fill. Blowdown helps reduce the concentration of these minerals, minimizing scaling.
High concentrations of certain impurities, such as chlorides, can accelerate corrosion in cooling systems. By controlling the concentration of these corrosive substances through blowdown, the risk of corrosion is reduced.
Blowdown also helps control the growth of harmful microorganisms, such as bacteria and algae, in the cooling water.
Two Primary Blowdown Methods
1. In manual blowdown, the operator periodically opens a blowdown valve to release a portion of the cooling water. The frequency and volume of blowdown are adjusted based on water quality measurements and system requirements.
2. Automatic blowdown systems use sensors or controllers to continuously monitor water quality parameters, such as conductivity or total dissolved solids (TDS). The system automatically adjusts the blowdown rate to maintain water quality within preset limits.
Blowdown Rate
The blowdown rate is the volume or percentage of water discharged from the cooling tower compared to the incoming makeup water. The blowdown rate is typically expressed as a percentage or as a ratio. The ideal blowdown rate depends on factors such as cooling tower design, water quality, and operating conditions.
Blowdown Treatment Methods
Wastewater treatment methods for cooling tower blowdown typically aim to remove contaminants, such as suspended solids, minerals, and organic matter, before the water is discharged or reused. The choice of treatment methods depends on the specific characteristics of the cooling tower blowdown and local regulations. J Mark has extensive experience in treating cooling tower blowdown and working within local regulations. In this blog, we will focus on some of the main methods that J Mark specializes in.
1. The first method we will explore is sedimentation. Sedimentation allows the suspended solids to settle out by gravity in a settling tank or slant plate clarifier.
A slant plate clarifier is ideal for large bodies of wastewater that need treatment, as they work quickly and effectively with minimal cost and monitoring.
As water enters a clarifier, the liquid is forced up through plates while gravity forces the solids to fall out of the flow. The solids settle in a cone shaped section for removal while the clarified liquid flows over the weirs and into a trough before being discharged through a connection at the bottom of the trough.
J Mark has 7 standard sizes of clarifiers that can be rented or purchased, with sizes ranging from 20gpm to 150gpm.
Click here to read about how J Mark clarifiers are only made from the highest quality parts.
2. Next, we will dive into Ion exchange. Ion exchange resins can be used to remove specific ions (e.g., hardness ions, heavy metals) from the water by exchanging them with less objectionable ions.
Ion exchange is a chemical process that eliminates dissolved ions in water and wastewater. Nitrate, fluoride, sulfate, and arsenic are examples of the kinds of dissolved ions that ion exchange can remove.
Those unwanted ions are exchanged with other ions that contain similar charges. As those ions are attracted to each other, the dissolved ions contaminating the water are removed and replaced by better ions.
Click here to read more about ion exchange and how it is used to remove unwanted contaminants.
3. Next, we look at filtration. Filtration involves passing the water through filters (e.g., sand filters, multimedia filters) to remove suspended solids and fine particles down to 5 microns.
Multimedia filters are an excellent way to get rid of silt, clay, grit, organic matter, algae, microorganisms, and more. These substances naturally occur in many water sources but aren’t so great for drinking.
Click here to visit our multimedia filter page to view the multimedia filtration options.
4. Lastly, we will explore reverse osmosis. Reverse osmosis is a membrane process that removes dissolved salts, minerals, and other impurities by forcing water through a semipermeable membrane.
Reverse osmosis is not the same thing as filtration. Reverse osmosis systems use a filtration process with multiple steps and include reverse osmosis in action.
Filtration can’t compare. Most filtration systems use activated carbon or a filter media, which is better than nothing, but won’t help with dissolved solids, arsenic, viruses, or bacteria.
J Mark offers reverse osmosis units for rent or to purchase. Click here to view more information regarding J Mark Reverse Osmosis units.
It's important to note that the treatment approach might involve a combination of these methods, and the specific design of the treatment system will depend on factors such as the composition of the cooling tower blowdown, local regulations, discharge standards, and the intended reuse of the treated water. Consulting with a J Mark specialist and regulatory authorities is crucial to developing an effective and compliant treatment strategy.
Blowdown Disposal
Blowdown water typically contains elevated levels of impurities, which can be harmful to the environment if directly discharged. Therefore, proper disposal of blowdown is essential. Common disposal methods include:
Sewer Discharge: In some cases, blowdown can be discharged into the municipal sewer system, subject to local regulations.
Evaporation Ponds: Blowdown can be collected in evaporation ponds, where it is allowed to evaporate, leaving behind concentrated solids that can be properly disposed of.
Onsite Treatment: Blowdown can be treated onsite using various water treatment methods to remove or reduce impurities before disposal.
J Mark Systems
Over decades, J Mark Systems has become an expert in cooling tower blowdown. With hundreds of installations under our belt, we have the experience you need to ensure that your water system is safe. You can trust our knowledge and rely on us for high-quality work in everything we do.
Every day, J Mark Systems works with industrial water systems to ensure that your water is clean for use by everyone who has access to it. We provide treatment solutions via wastewater treatment, reverse osmosis, and various treatment technologies like multimedia filtration and membrane separation.
Do you need wastewater treatment for cooling tower blowdown? We’re here for you, whether you know what you need or are looking for expert guidance. You can contact us to get started today! J Mark Systems has the treatment solution you need for your industrial water system.