Case study ——
State-of-the-Art Wastewater Treatment Facility at Blue Plains for DC WASA

Manufacturing units engineered to withstand the harsh conditions of wastewater treatment facilities while delivering an energy recovery efficiency of at least 65%.

The District of Columbia Water and Sewer Authority (DC WASA) required fully outdoor air handling units for its state-of-the-art Blue Plains wastewater treatment facility.

Project Details

  • 12 identical rooftop units
  • Two-level stacked plate heat exchangers
  • 18,800 CFM of outdoor airflow and 15,250 CFM of exhaust airflow
  • Built entirely (100%) of 316 stainless steel
    • Fans
    • Dampers
    • Unit cabinet/housing
    • Structural frame
    • Belt guards
    • Spring isolator cages
    • Fiberglass floor grating for return air
  • 1,000 MBH corrosion-resistant direct-fired burner
  • Programmable DDC controller with BACnet communication protocol
  • NEMA 4X electrical wiring
At least 65%
energy recovery

Context

A design tailored to the demands of wastewater treatment.

During the initial assessment of this application, the primary objective was to take a closer look at the harsh operating environment of this wastewater treatment plant. The main chemical compound that had to be considered was hydrogen sulfide gas (H2S).

Need

The units had to withstand the harsh conditions found in wastewater treatment facilities while delivering energy recovery efficiency of at least 65%.

Solution

As a leader in the potash mining sector, Bousquet Applied developed and refined a custom 304/316 stainless steel unit for potash mine applications, avoiding the need for a fully aluminum and galvanized steel construction.

Results

The 304/316 stainless steel construction of the units also incorporates features such as a riveted panel assembly system, a formed and welded stainless steel sheet metal frame, specialized coatings for the gas burners, and other key components to prevent corrosion and premature failures caused by this harsh environment. Every element, regardless of size, is critical to maintaining the integrity of the unit. From large fans down to nuts and bolts, each component plays a key role in the unit’s structural integrity, since the unit is only as strong as its weakest link. That is why Bousquet Applied paid special attention to the fans, motors, belt guards, spring mounts, sensors, wiring, dampers, actuators, gas manifolds, heat exchangers, hinges, handles, supports, window trims, access ladders, switches, nuts and bolts, and more.

One of the main points of comparison between a potash environment and a wastewater environment is hydrogen sulfide gas, which is relatively well tolerated by aluminum surfaces. This makes it possible to use epoxy-coated aluminum plate heat exchangers, maximizing energy recovery without concern for premature corrosion.

The selected aluminum heat exchanger provides 65.7% sensible energy recovery efficiency and 78.8% latent energy recovery efficiency. This relatively high efficiency will significantly reduce natural gas heating demand, since these units will operate continuously.

Annual natural gas savings are estimated at 17,733 m3 (638,000 ft3) per unit.

This is equivalent to a reduction of 3,898 tons of CO2 emissions per year for the facility!

Working in a challenging environment?
We design the right solution for it.

Case Study ——
Toronto Transit Commission McNicoll Bus Garage

Manufacturing air handling units designed to deliver the highest possible energy recovery efficiency with the lowest possible cross-contamination rate.

Built to Toronto Green Standard requirements, the facility includes multiple sustainable features, including one of the largest green roofs in Canada, solar panels, and a perforated metal solar wall to harness solar energy and help heat the building.

Project Details

  • 33 energy recovery units and 9 make-up air units
  • Two-level stacked plate heat exchangers
  • Total supply airflow of 700,000 CFM
  • Programmable controller with BACnet communication protocol
  • NEMA 4X wiring
70% heat
recovery

Context

A solution engineered to maximize energy recovery without compromising air quality.

The TTC required fully outdoor air handling units that would deliver the highest possible energy recovery efficiency while minimizing cross-contamination to the greatest extent possible.

Need

The cross-contamination limitation stemmed from the fact that the 250 buses parked or serviced indoors released significant amounts of combustion gases into the exhaust airstream. The high-efficiency requirement made the use of plate heat exchangers challenging, while the low cross-contamination requirements virtually ruled out the use of energy recovery wheels.

Solution

In collaboration with Klingenburg GmbH, 33 cross-flow air-to-air plate heat exchangers were selected and manufactured to provide virtually no exhaust air carryover, along with efficiencies of 70.9% under wet conditions and 60% under dry conditions, in accordance with AHRI 1060. Outdoor air and exhaust air bypasses were also integrated to limit frost buildup, facilitate direct purge, and reduce fouling of filters and heat exchangers.

Results

The high-efficiency, AHRI-certified heat exchangers, combined with the use of direct-fired burners, will generate substantial natural gas savings since these units will operate continuously. Annual natural gas savings are estimated at 4,408,111 m3 (158,595,546 ft3) for the site as a whole.

This represents a reduction of 80,572 tons of CO2 emissions per year for the facility!

Every application comes with its own requirements.
We develop the right solution.