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​Argun Erdogan
Product Manager

Envirex® Sludge Heater / Heat Exchanger

Safe, reliable and long-lasting performance

Envirex® combination heaters/heat exchangers are integrally designed to ensure safe and reliable operatio​n for durable, long-lasting performance. This is the next generation of the well-known PFT sludge heater, for which Evoqua is the OEM.

The flame safeguard system and induced draft fan eliminate the possibility of dangerous gas leaks. In addition, the induced draft design permits the burner to operate at lower gas pressure, eliminating the need for gas booster pumps and optimizing the use of free digester gas.  The rear return section, known as the water back, is guaranteed to last the life of the boiler unlike conventional return sections that utilize refractory, which require frequent replacement.

Advanced options are available for maximum efficiency and low emissions requirements. A state of the art Honeywell combustion control system provides 24/7 monitoring and control to ensure maximum utilization of digester gas. A low emissions Honeywell/Maxon burner is also available to meet strict emissions requirements.

Envirex tube-in-tube heat exchangers are also available for applications where a facility already has a hot water source or is using a separate hot water boiler. The proven grooved piping system provides efficient heating or cooling of sludge with large return elbows to prevent clogging.

New Design Tool

Find out if the Sludge Heater / Heat Exchanger System is a good investment for your application. Receive a free proposal including system design, budget pricing and estimated cost savings. Click here to get started!



 Long Life and Ease of Maintenance

Unlike conventional heat exchangers, Envirex units are designed for ease of maintenance and long-lasting performance.

  • Cast Iron return bends ensure long life

  • Heat exchange tubes are held in place by gaskets and cast iron following rings to permit cleaning of the tubes without draining the water bath

  • The multiple gasket arrangement ensures early detection of gasket failure and eliminates the possibility of waste solids or water fouling the interior of the heat exchanger

Digester heater/heat exchanger maintenance is often overlooked. Read our article on Four Tips for Trouble-Free Digester Heater/Heat Exchanger Operation to reduce potential failure and downtime.

 Engineering and Service Support

Evoqua product engineers and service team can provide on-site inspections, engineering support, and process expertise for complete turnkey installation and repairs.

  • Inspection services for any component or complete digestion system
  • Personnel training and maintenance guidelines
  • Complete turnkey installation services and repairs available
  • OEM parts for all Envirex and PFT equipment
  • Engineering and process expertise
  • Control system upgrades  


Our team  has helped develop successful water and wastewater treatment systems for over 100 years using well known technologies. In addition, our industry leading database of OEM drawings provides for faster, more cost effective and responsive project execution. Envirex® Sludge Heater / Heat Exchanger