By early December 2014, working in partnership with the Municipality of Tara and the local office of the Ministry of the Environment and Climate Change, Lallemand Bio-Ingredients agreed to shut down all production until the problem could be effectively resolved.
With help from an Owen Sound, Ontario-based engineering firm specializing in environmental analysis and solutions, a plan was developed to cover the 41 m wide x 19 m oval shaped water basin by constructing a 1.2 m concrete retaining wall with a rigid 9 metre canvas dome. This would trap the aerosolized sodium selenite for treatment by a custom engineered odour abatement technology.
To avoid having to renovate the current wastewater treatment building to accommodate a chemical scrubber or media absorption device as well as air handling infrastructure, Lallemand chose Odorox® atmospheric hydroxyl generating technology from Hydroxyl Environmental Inc. It has proven to be successful with other wastewater treatment plant applications in Ontario for treating hydrogen sulfide. Since the electron potential of atmospheric hydroxyls exceeds that of Na₂SeO₃, this was an odour problem Odorox could also solve.
Odorox hydroxyl generators have been independently tested and scientifically verified. They produce the same steady state levels of atmospheric hydroxyl radicals and other oxidants as the sun’s rays in our atmosphere. These oxidants react with volatile organic compounds, water vapour and other chemicals in the air to generate the same mixture of organic byproducts produced in nature.
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These byproducts continue to be oxidized until they yield O2, CO2, H2O, etc., as found in nature. The technology can be used in occupied spaces as proven through recent independent, FDA compliant toxicology studies, which showed animals exposed to Odorox treated air were no different than unexposed animals.
Based on the economical odour abatement solution that Hydroxyl Environmental offered and the research the client had done investigating the technology, it agreed to move forward with Odorox equipment. All that was needed to accommodate the hydroxyl generators was a concrete pad for an aluminum storage shed, and the retrofit of two simple static ventilation screens. The shed was assembled adjacent to the dome and 9 metres from the current wastewater treatment building, where a 120v dedicated 20 amp service was made available to power the generators, and a single Odorox automation control panel was mounted.
Sitting within the shed on separate elevated aluminum platforms, two MVP14™ hydroxyl generators, each with its own 1,400 cfm blower package, draw clean outdoor air through the static ventilation screens and then blow hydroxyl-rich air through a 35.5 cm cut-out within the dome and shed walls. The 4,757 m3 domed structure created the perfect retention vehicle to allow generated hydroxyl ions to break robust Na₂SeO₃ molecular bonds, thus neutralizing the odour.
Mounted close to the exhaust vent within the dome is a Draeger Polytron 7000 oxidant sensor, which is used by the Odorox controller to adjust hydroxyl production from the generators. This unit measures oxidant concentration and compares it to pre-set limits within the controller. If the hydroxyl oxidant production is measured below the set-point, it is assumed that the generated hydroxyls are being consumed in reactions with odorous compounds and the device receives a signal to maintain hydroxyl production.
Once the measured oxidant level is above a set-point, hydroxyl production is stopped. This results in energy
savings and optic life extension over an “always-on” configuration. This automation feature and the ease at which the Odorox system could be connected to Lallemand’s internal network was another factor in the company’s decision to move forward. Hydroxyl production levels and other system status data are monitored through a web application. This allows engineers and maintenance staff to follow in real time the environmental conditions in the basin dome from their smartphones, or home computers.
In March 2015, Lallemand Bio-Ingredients received approval from the Ontario Ministry of the Environment and Climate Change to restart production. The company is continuing to work with residents of Tara as part of their commitment to eliminating all lingering fugitive odour concerns.
Martin Slepkov is with Hydroxyl Environmental Inc. Odorox and MVP14 are registered trademarks of HGI Industry, Boynton Beach, Florida. This article appeared in ES&E’s July/August 2015 issue.