Small-footprint, “green” technology lowers costs dramatically and offers ‘worry-free’ performance

Envirogen Technologies, Inc. (Envirogen) announced the successful start-up of a new bioscrubber tower system for odor control at the Anastasia Island Wastewater Treatment Plant (WWTP) in St. Augustine, Florida. The high performance, energy-efficient system will remove hydrogen sulfide (H₂S) from air at the plant’s headworks. A key factor in the selection of the vertical Envirogen bioscrubber tower is its ability to handle high concentrations of H₂S with a small physical footprint. Envirogen will also provide installation oversight and staff training services to ensure trouble-free operation at start-up. The bioscrubber tower system is another example of Envirogen’s biological treatment technology for air quality improvement that is gaining acceptance because of increasing interest by municipalities and engineering firms in sustainable treatment solutions. Nationwide, Envirogen has installed more than 150 biological systems for odor control, as facility operators recognize the low lifecycle cost and low environmental impact of this treatment approach. Hydrogen sulfide is an odor-causing gas that occurs in almost every wastewater collection and treatment system in the United States, and poses both health threats and corrosive damage to treatment systems that can decrease use life and increase costs.

According to David Enegess, Vice President of Envirogen Products and Envirogen’s East Region, the company has extensive expertise with this technology in the field and is poised to install many more of this type of system. “From our early developmental work over a decade ago to a demonstration at a 1 billion gallon per day plant, we’ve been working to optimize biologically based odor control technology with good success,” Enegess said. “The result is an extremely efficient, low-cost system that reliably handles H₂S and other odor-causing compounds with less energy, virtually no chemicals and with a smaller amount of land required than competing systems. Our experience puts us in a strong position to deliver the benefits of this truly innovative ‘green’ technology to municipalities and industry alike,” he added.

The Anastasia Island installation, located on a small island on the east coast of Florida, consists of two bio-trickling filter towers followed by a carbon adsorption unit for polishing. It is designed for 99% removal of H₂S at airflow rates up to 4,600 cubic feet per minute (CFM) and will be handling relatively high inlet concentrations of H₂S (500 – 1,000 ppm), a challenge for which the biotower design is ideally suited. In addition, the unit is built to withstand the hurricane-force wind conditions (up to 120 mph) that can occur in that region.

According to Larry Miller, Chief Engineer, Capital Projects for St. Johns County Utilities and Project Manager for the Anastasia Island plant expansion, the Envirogen system was an ideal choice to handle the plant’s odor control needs. “Initially, a chemical scrubber was specified for this project, until we determined that such a system would be cost prohibitive to operate given the high concentrations of H₂S at the site,” Miller said. “This bioscrubber tower gives us stable, low-maintenance performance in a tight footprint.  Envirogen also provided us with excellent support in clearing the many hurdles to getting this system up and running,” he continued.

Envirogen’s bioscrubber tower is a vertically oriented bio-trickling filter in which contaminated air is passed through a bed of inorganic media along with a recirculating water flow. Naturally occurring microorganisms present on the media surface consume reduced sulfur compounds (including H₂S), volatile organic compounds (VOC) and other odor-causing compounds, while the recirculation water allows for optimal control of pH, nutrient levels and biofilm thickness. The system is self-regulating, requiring little or no operator attention and minimal energy to operate. The tower configuration is ideal for high contaminant concentrations, VOCs and where space is at a premium. The systems can easily be expanded within the existing small footprint by adding vertical segments. Unlike chemical scrubbers, Envirogen’s biofilters eliminate the need for expensive and potentially hazardous chemical storage and handling. Low chemical and energy consumption and trouble-free operation allow these bioscrubber towers to deliver the lowest cost over the life of the installation.

 According to Enegess, biotowers are an increasingly popular option for municipalities and industry seeking to achieve worry-free, low cost odor control in space-restricted areas. “We’ve seen biofilters move from an emerging technology to a widely accepted one in a short time, largely because they answer today’s need for dependability, controlled costs and environmental sustainability in wastewater operations,” Enegess said. “With over 150 biofilters successfully installed at over 50 locations, we are seeing this approach become the industry standard for air treatment. Today, we are able to rapidly and effectively design customized solutions that are cost competitive with ‘off-the-shelf’ solutions, but that deliver more reliable, worry-free performance over the long term,” he concluded. For more information on this technology, visit www.envirogen.com.