Alfa Laval HYAC provides efficient and reliable cooling in US municipal wastewater plant

Top performance, high operational reliability and minimal environmental impact were key selection criteria when one of the largest wastewater treatment agencies in the US invested in a new cooling system for a set of pump drives. After thoroughly investigating several possible solutions, the agency chose to install two Alfa Laval HYAC hybrid air coolers.

DATE 2023-11-28

The wastewater plant, located in the Midwestern United States, is one of the largest in the country. It is a central part of a network of plants that treats sewage and stormwater from one of the most populated cities in the US.

Water-cooled pump drives

The raw wastewater is pumped up to the treatment plant from one of the tunnels, 300 ft below ground, built to act as buffers during periods with heavy loads. The pumps are controlled by variable frequency drives (VFDs) placed in an underground space. The VFDs develop substantial amounts of heat and require liquid cooling to operate.

For the last four decades the plant has used two Alfa Laval wet surface air coolers (WSAC), placed at ground level, to cool the water/glycol mixture used for cooling the VFDs. The WSAC units have operated very reliably and required minimal maintenance.

Tough requirements

While planning a revamp of the pumping system, the customer investigated the possibilities to upgrade the VFD cooling system. The list of requirements on performance, operating reliability, compliance with plant standards, personnel safety, etc. was long, and Alfa Laval was the only company that could fulfil them.

Alfa Laval HYAC hybrid air coolers

Combining traditional air cooling and closed-loop evaporative cooling, Alfa Laval HYAC hybrid air coolers offer reliable and effective cooling for a range of industrial applications. 

More about HYAC 


  • Higher thermal performance
  • Easier operation
  • Maximum operating reliability