Quick-Dissolving Alkaline Additive Provides Temporary Odor Control for the City of Tampa

The present paper describes a successful, novel method for controlling odors and corrosion in sanitary sewer systems. The City of Tampa Department of Sanitary Sewers operates the East Tampa Pump Station. East Tampa Pump Station delivers approximately 11,360 m3/day (3 mgd) of wastewater to the Howard F. Curren Advanced Wastewater Treatment Plant (AWTP). The City has addressed hydrogen sulfide and related odors at the East Tampa Pump Station for over 15 years with a mist-type chemical scrubber. In October of 2011 a project was initiated to rehabilitate the wet well of the East Tampa Pump Station.The rehabilitation and construction plan called for personnel to occupy the wet well six to eight hours a day for eight to ten weeks while the pump station remained in operation. During worker occupation the wet well would be opened and positive ventilation would be applied, which would cause bypass of the odor control system and release of odors to the surroundings. Odors and odor complaints are a primary concern in the vicinity of the pump station, so a temporary odor control plan was required. Vapor-phase technologies could not be used due to loss of vapor-phase containment during rehabilitation activities.The City first considered technologies which were already employed at other locations in the City collection system, namely magnesium hydroxide and nitrates. Both magnesium hydroxide and nitrates require a minimum of 30 minutes of detention time in order to be effective. The collection system upstream of East Tampa Pump Station consists of a large manifolded force main system and two trunk sewers with no dominant flows, making the logistics of applying these alternatives difficult and inefficient. A solution was desired that could be fed at a single point on site or immediately upstream of East Tampa Pump Station. A non-hazardous technology was preferred and would be required if fed off-site of the pump station.A quick-dissolving alkaline addition solution was employed. Since the alkaline solution employed dissolves quickly it was able to be applied at a single point upstream of the pump station. This allowed the dosing to be very tightly controlled and turned completely off overnight when the wet well was closed and the scrubber could be used.Since the solution used is non-hazardous, it was able to be dosed using a generator-powered feed system at a temporary location on the property of one of the stakeholders who would have been affected had there been odors associated with the project.The solution successfully controlled odors throughout the duration of the original project and a subsequent odor control replacement project.