WWTP OdorControl Project for Town of Friday Harbor, WA: 2009 - After local residents complained of bothersome odors coming from the waste water treatment plant, the Town decided something had to be done. At the outset the Town staff expected this to be a simple project. The Town wished to enclose the headworks and provide better enclosure for the sludge processing and dried sludge storage areas, placing all of these process components under negative pressure. Changes envisioned to mechanical systems were limited. Wayne Haefele & Associates was asked design these improvements.

Our code review, research into the regulatory environment and inquiries into the experiences of other wastewater agencies with respect to odor control opened numerous concerns touching on industrial ventilation and hygiene, fire and explosion safety, waste air characteristics and the appropriateness and limitations of treatment processes. All of these things indicated the need for a foul air collection and treatment process chain.

Capture strategies, calculation of flow rates and duct velocities, the processes chosen and sizing of process units required consideration and resolution of these concerns. The project grew to consist of additions to two existing buildings and installation of three new foul air collection systems incorporating five constant speed direct drive centrifugal blower units, an impingement plate scrubber unit, modifications to the existing headworks foul air biofilter (being used as a GAC filter) and construction of an open compost bio-filter with associated appurtenant plumbing, piping, electrical work and modifications to site piping.

Prior attempts at containment of dust and odors from the dried sludge storage area by sealing and caulking the existing structure had failed, allowing odors from the hot sludge to escape in surprisingly large volumes through small cracks and gaps in the walls and eves. To solve this problem, we designed all the process area enclosures to be positively sealed by incorporating a continuous 30 mil fusion welded pvc membrane hidden within the walls, floors and cielings.

Wayne Haefele & Associate's scope of work on this project encompassed research, building addition layout and structural design, foul air collection and treatment design, electrical power distribution and control design, construction documentation, project cost estimates, bidding assistance, construction management and inspection. The project was completed November 2011 at a total cost of $626,733.