The June issue of WWD is a little different from the rest. Editor-in-Chief Elisabeth Lisican explains.
A critical requirement in wastewater handling is the prevention of escaping odor from lagoons and storage ponds. These malodorous sulfurous compounds can waft over communities unless they are capped effectively.
Even occasional lapses in the maintenance of an effective odor cap can have dire consequences. For example, the turbulence produced by brush aerators can release aerosols and bacteria-laden mist into neighborhoods, risking serious health hazards, public outrage and even facility shutdowns.
These problems can occur at municipal wastewater ponds and industrial storage basins, especially those holding manufacturing effluents. The only solution is ensuring that odor is capped effectively.
To ensure reliable odor control, wastewater managers often count on some elaborate methods to cover odor from storage basins and anaerobic ponds. Some plants spray or inject deodorizers to neutralize tank vapors. Others use expensive blower systems or windmills to filter odorous compounds or disperse them into the air—and away from nearby communities, they hope. Still, others count on chemicals like hydrogen peroxide to offset the odor.
All of these measures can be costly, especially in energy usage, and their capabilities are often marginally effective. Fortunately, growing numbers of wastewater managers are finding a much better, more reliable and efficient means for attaining real odor control.
Solar-Powered Water Circulators
Solar-powered long-distance circulation (LDC) has emerged as an excellent solution for odor control at industrial and municipal facilities. In particular, SolarBee circulators offer highly effective and efficient odor control at all kinds of wastewater facilities. With SolarBee on the job 24/7, those facilities can prevent health hazards and minimize—or even eliminate—air quality citations and public complaints.
Equally important, by using SolarBee, facilities can save money by eliminating the use of chemicals and deodorizers. The biggest savings of all, however, come from the fact that this solar-powered device requires very little, if any, electrical grid energy.
SolarBee’s LDC aerates ponds by circulating only the top 2 ft of the pond at rates of up to 10,000 gal per minute. This circulation occurs with a gentle, near-laminar flow, providing an oxygenated odor cap across the entire pond surface. Near-laminar flow means no turbulence, and that means no biological oxygen demand (BOD) is brought up to deplete the dissolved energy and destroy the odor cap. Because of this constant, uniform surface renewal, the LDC also provides increased anaerobic digestion, increased sludge densification and decreased sludge volume.
Case 1: Myrtle Beach, S.C.
The city of Myrtle Beach tried to control odor by installing a bubble diffuser aerator system at the bottom of its 48-acre raw sewage pond. Aeration’s suspension of particulates was supposed to prevent sludge buildup and odor creation, but the approach did not work. In fact, the diffuser aerator threw sludge and odor up to the pond surface, where it then wafted over the city.
In January 2005, Myrtle Beach installed six SolarBee circulators in the first three cells of its wastewater holding lagoons. The coarse bubble aerators in those cells were shut off. Measurements taken in August showed vast improvement from those recorded in June 2004. Dissolved oxygen was 4.5 mg/L, compared to 1.8 mg/L, and ambient H2S levels were zero in all points but one, which was a low 2.7 ppm.
Perry Shelley, superintendent of Myrtle Beach’s water reclamation facility, recently said that the SolarBee units continue to keep odor under control. Also, because the aerator blowers are not in use, the city is saving approximately $50,000 per year.
Case 2: Martinez, Calif.
Shell Oil’s Martinez refinery is less than a mile from a residential community, whose residents would complain if even a slight amount of odor was released into the air. The facility was using two brush aerators to control odor at the refinery pond, but it often failed to provide a continuous odor cap to the pond edges, thus allowing foul smells to escape into the air. Also, the turbulent action of the aerators disturbed pond sediment, causing BOD to rise and eat away the odor-insulating oxygen blanket.
David Williams, the facility manager, found an enduring solution by installing SolarBee units in the pond. Near laminar LDC provides an oxygenated odor cap across the pond’s entire surface 24 hours a day. The units save more than $10,000 per year in energy costs compared to the hard-wired aerators. “What we have,” said Williams, “is a paradigm shift in pond aeration.”
Best of all, the excellent results continue in Martinez. In December 2008, Shell Oil’s Ray Fong confirmed that the units continue to do a great job at providing odor control.