Increasing Water System Sustainability - Part 5:

Using Pretreatment Equipment to Remove Problem Causing Impurities

  • 28 mars 2023
  • Author: Chem-Aqua, Inc
  • Number of views: 3056
  • 0 Comments

The quality of water entering a boiler, cooling, or process system can have a significant impact on water, energy, and system efficiency. Raw makeup water can come with many different types of impurities, including dissolved and suspended solids, which can lead to energy-robbing scale deposits and equipment-damaging corrosion. Pretreatment equipment removes unwanted impurities from raw makeup water before they can cause problems in industrial water systems.

There are many types of pretreatment, with each impacting water quality in its own unique way.

  • Makeup Water Pretreatment Equipment OptionsFiltration: Removes suspended solids using various filter media (e.g., sand filter, multi-media filtration, bag filters).
  • Iron Filters: Reduces ion and manganese through oxidation and filtration.
  • Water Softener: Softens water by removing calcium and magnesium hardness ions. This is typically accomplished by exchanging hardness for sodium on an ion exchange resin. 
  • Dealkalizer:  Reduces carbonate alkalinity. Chloride cycle ion exchange is often used to replace carbonate with chloride on an ion exchange resin.
  • Activated Carbon: Reduces chlorine and organics through reaction and adsorption with its porous surface.
  • Membrane Filtration: Uses a semi-permeable membrane to remove bacteria and dissolved solids from water. Reverse Osmosis (RO) is commonly used to make high-purity water.
  • Demineralizer/Deionizer: Uses ion exchange to greatly reduce all dissolved solids to produce high-purity water.

Boilers
Water quality is highly important in a boiler water system. Scale deposits can be insulating and negatively impact fuel efficiency by impeding heat transfer. Corrosion can reduce the lifespan of boiler system equipment, resulting in downtime and lost production. A well-implemented water treatment program will allow the boiler system to operate using both a minimum amount of water and energy.

Pretreatment Impact

  • Water Softener: Reduces scale forming potential to maximize heat transfer efficiency and minimize energy and maintenance costs.
  • Dealkalizer: Reduces boiler alkalinity to minimize carbonic acid attack of condensate systems.  Decreases condensate neutralizing amine usage and costs.
  • Reverse Osmosis: Allows boiler systems to run at higher cycles of concentration, which reduces energy and water costs.
  • Activated Carbon: Removes free chlorine before an RO to protect the membranes from degradation.
  • Demineralizer/Deionizer: Allows boiler systems to run at higher cycles of concentration, which reduces energy and water costs, similar to an RO.  Higher-pressure boilers may require the higher purity water that demineralizer/deionizers can produce.
  • Iron Filter: Minimizes iron returned with the condensate that can form insulating deposits in boilers.

Cooling Towers
Scale deposits and corrosion can have negative impacts on a cooling tower system by reducing heat transfer efficiency, increasing downtime, and decreasing equipment lifespan. Applying the appropriate pretreatment technologies can help both the cooling tower and the systems it supports run more efficiently.

Pretreatment Impact

  • Water Softener: Reduces scale forming potential to maximize heat transfer efficiency and minimize energy and maintenance costs.
  • Iron Filter: Minimizes iron from makeup water that can form insulating and flow-restricting deposits.
  • Filtration: Removes suspended solids for cooling water to reduce deposits that can inhibit heat transfer, restrict flow, and house unwanted microbiological activity.
  • Reverse Osmosis Reject Water: Depending upon water quality, the reject (aka, concentrate) stream from an RO system can sometimes be used as a makeup source to cooling towers to reduce fresh makeup requirements.

Closed Loops
While designed to avoid direct air contact and evaporation, closed recirculating water systems can still experience insulating scale and microbiological deposits as well as equipment-damaging corrosion. Implementing the appropriate pretreatment technology can help mitigate these problems.

Pretreatment Impact

  • Water Softener: Reduces scale forming potential to maximize heat transfer efficiency and minimize energy and maintenance costs.
  • Demineralizer/Deionization: While also reducing scale forming potential to maximize heat transfer efficiency, stricter system requirements may dictate a higher purity water for operations with low tolerance to fouling.
  • Filtration: Removes suspended solids that can form deposits which can restrict flow, reduce heat transfer efficiency, house unwanted microbiological grown, and increase corrosion. Filtration can reduce suspended solids in the makeup water as well as on a sidestream of the closed loop water itself.

Process Waters
Process water systems provide water for a variety of manufacturing processes with a range of water quality requirements to keep the systems running efficiently. Examples include cleaning baths, chemical blending, cutting, product components, etc. The pretreatment equipment required will depend upon each system’s unique requirements. 

Potential problems caused by inadequate pretreatment include, but not limited to:

  • Scale deposits
  • Corrosion
  • Fouling
  • Streaking
  • Spotting
  • Adherence issues
  • Taste
  • Color
  • Microbiological Activity
  • Quality Control issues

Conclusion
Choosing the proper pretreatment strategy for a boiler, cooling, or process system can have a significant impacts upon achieving energy, water, and resource sustainability objectives. Chem-Aqua manufactures a full line of pretreatment options, including filtration, water softeners, dealkalizers, activated carbon, reverse osmosis, and demineralizers/deionizers systems. Contact Chem-Aqua to schedule an onsite consultation to determine which options best fit your needs.

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