Blending Odor Control into a City Gateway

In 2012, the City of Jeffersonville, Indiana completed the 10th Street Pump Station (10th St PS) Expansion Project which increased its peak capacity from 15 million gallons per day (MGD) to 50 MGD and included the addition of screening and grit removal facilities but no odor control. The 10th St PS is located at one of the main entrances into the City and multiple odor complaints were received shortly after the completion of the project, so plans were immediately initiated to provide odor control from multiple sources at the site.The unique challenges presented by this project required careful consideration, planning and execution and this paper will provide insight into the approach and solutions applied. Specifically, the issues were as follows:The 10th St PS receives combined sewer flow that can exceed 50 MGD but only averages 1.5 MGD during dry weather. Therefore, most of the time it is operating at 3% of its capacity, resulting in long detention times in the grit tanks, the settling of organics, and the emission of high levels of hydrogen sulfide (H2S).This is a highly visible area to the public and the City wanted the odor control system to blend into the surroundings as they developed this City Gateway. A priority was therefore placed on installing a low profile odor control technology.An important aspect of this project to the City was to maintain ease of access inside the Influent Structure and Grit Tanks for maintenance and cleaning purposes. This required special attention to the routing of the foul air ducts and to the locations of multiple access hatches in the covers. The Influent Structure was of particular concern as it contains an overflow screen that requires cleaning after each wet weather event. The Influent Structure is rectangular (~20 feet x 25 feet) with walls that extend above grade by 4-1/2 feet. The City requested to have continuous hatches along both sides of the structure which could be opened without requiring a worker to access the top of the structure.An odor study was conducted in September 2012, in order to provide recommendations for mitigating offsite odors. The odor study focused on multiple sources including the Screen Building exhaust, the Influent Structure, and the Grit Tanks. Two (2) rounds of sampling were conducted to capture data under differing environmental conditions. Air samples were tested for hydrogen sulfide (H2S), reduced sulfur compounds (RSCs), and odor Detection Threshold (DT). Wastewater samples were also taken at key locations for analysis. The results of the odor DT and RSC sampling will be presented in this paper. Moderate concentrations of H2S (7 — 28 ppm) and fairly significant concentrations of Methyl Mercaptan (MM) were measured from all three (3) sources, which required treatment. OdaLog monitoring revealed that peak concentrations of H2S (>300 ppm) were being released inside the Screen Building which posed both health and corrosion concerns. DT levels ranged from 5,000 to 60,000.The results of the odor study were used to prioritize the odor sources and to evaluate appropriate technology options for their control. The odor study evaluated multiple treatment technologies based on effectiveness as well as a 20 year lifecycle cost analysis. The study concluded that a bioscrubber or biofilter would be the best and most cost effective solution for odor control due to the high levels of H2S and minimal ongoing operational costs. Due to the high visibility of this area, the City chose to construct an atgrade, low profile biofilter as it could be concealed behind a decorative wall, which the City was planning.In 2013, the design of the odor control system for the 10th St PS was completed with the goals of significantly reducing the offsite odors and blending into the environs. The final design included an engineered organic media biofilter, a foul air fan, all ductwork, and covers for the Grit Tanks and Influent Structure.In September 2013, a contract was awarded and construction of the odor control system was completed within 12 months. Because of the need to access the Influent Structure overflow screen, an FRP cover fabricator and a metal fabricator were consulted to design a cover system with electrically actuated hatches that could easily be raised and lowered from ground level.Performance testing on the biofilter was conducted in June of 2014 and the system achieved greater than 99% removal of H2S. Additionally, odor complaints associated with the 10th St PS have been solved with a system that meets the requirements of effectiveness, appearance and access. In the year 2015, the City constructed an architectural wall which surrounds the pump station and biofilter. This large pump station is now well hidden from sight and smell.