The problem
The sludge handling facility at the Arlington, Virginia Sewage Treatment Plant — located approximately one mile from Ronald Reagan Airport — required odor control for three scrubber systems handling hydrogen sulfide and ammonia from sewage treatment operations. H₂S and NH₃ at municipal wastewater facilities create fence-line odor nuisances and occupational exposure concerns, and must be controlled to a minimum of 99.5% removal to satisfy permit requirements. The additional challenge: sustaining that removal efficiency under variable inlet loadings, including peak conditions above the original design basis.
Independent testing confirmed non-detect at the outlet across all three scrubbers — even at inlet loadings above design conditions — with gas velocity headroom of 600+ ft/min.
Why Q-PAC was selected
Q-PAC was selected because its mass transfer and pressure drop characteristics were superior to the parameters established by the specified operating conditions. Q-PAC's performance allowed system expandability beyond the expectations of the initial design concept, its pricing was competitive, and its performance was substantiated by numerous studies and real-world applications. Lantec's confidence in Q-PAC was backed by a 100% performance guarantee.
Project scope
Three packed bed scrubbers were installed:
- One 7 ft diameter scrubber using H₂SO₄ to remove NH₃ entering at levels in excess of 135 ppm
- One 4 ft diameter scrubber using NaOH and NaOCl to remove H₂S
- One 12 ft diameter scrubber using NaOH and NaOCl to remove H₂S
H₂S inlet concentrations exceeded 20 ppm. All three scrubbers were required to achieve a minimum of 99.5% removal.
Meeting the requirements
An independent testing report dated May 20, 1998 showed conclusively that all three scrubbers far exceeded their design requirements. At inlet loadings higher than any actual operating condition, all scrubbers produced non-detect concentrations at their outlets — meaning removal efficiencies substantially greater than the 99.5% specification.
Pressure drop across the packing was also tested. System designers concluded that the scrubbers could be operated at superficial gas velocities of 10 ft/sec (600 ft/min) or higher while still meeting pressure drop requirements and the 99.5% mass transfer efficiency target — representing a 30–40% capacity reserve available for future expansion.