The Anson-Madison Sanitary District is operated by Woodard and Curran and treats 4 MGD of wastewater from Madison Paper Industries as well as the communities of Anson and Madison, ME. The treatment facility is located in close proximity to neighbors and has experienced odor issues for many years. Wastewater entering the treatment facility is oxygen deficient and the BOD degrading microorganisms are using sulfates as an oxygen source, forming high levels of hydrogen sulfide (H2S) gas. H2S levels have been recorded at 150ppm average with spikes of up to 800ppm.
In 2010 the District began adding calcium nitrate into the wastewater stream prior to the primary clarifier as an oxygen source for the microorganisms. This proved to be effective in controlling hydrogen sulfide levels, but very expensive ($1,000 per day).
In 2011 the District started exploring other options. Dissolved oxygen is the preferred source of oxygen for BOD degrading microorganisms and as long as aerobic conditions can be maintained, sulfide formation is effectively prevented. Woodard and Curran worked with ECO2 to design a SuperOxygenation System for the primary clarifiers. The goals were to eliminate H2S formation for employee safety, corrosion of equipment and control of odors. Another major goal was to off-set the use / cost of chemical addition.
The system was installed and started up in early 2012. Two VSA Oxygen Generators provide pure oxygen on-site and on demand for approx. $36,000 / year. The odors have been successfully eliminated and the SuperOxygenation System is saving the District about $300,000 / year.
Innovative and highly effective, SuperOxygenation technology is an eco friendly alternative to traditional chemical treatments for water and wastewater. Focusing on odor and corrosion prevention, ECO2 has helped cities across the country solve their needs in both municipal and industrial applications.
Odor Control for Primary Clarifiers
Primary Clarifiers are often the source for sulfide formation and downstream H2S odors. While the wastewater sits in the settling tank for several hours, dissolved oxygen is consumed and BOD degrading bacteria use sulfates as an oxygen source, producing dissolved sulfides. When the water flows over the
Impact of D.O. on Primary Clarifier Odor Control
effluent weirs, the turbulence strips out H2S, resulting in odor and potential corrosion.
Sulfide formation can be effectively prevented by maintaining aerobic conditions in primary clarifiers. The ECO2 SuperOxygenation System dissolves pure oxygen gas in water, raising the D.O. of the influent and providing for sufficient dissolved oxygen to satisfy the oxygen uptake rate and maintain aerobic conditions in the primaries. No sulfides are generated and therefore no H2S will be stripped out at the effluent weirs.
The ECO2 SuperOxygenation System efficiently adds sufficient D.O. to the primaries to maintain aerobic conditions and prevent sulfide formation. The ECO2 System raises the D.O. level in the influent stream to approx. 62mg/L. Since all of the oxygen is in a dissolved form, no spontaneous effervescence occurs in the influent well, despite the water being highly supersaturated with D.O. The available D.O. is consumed in the primary clarifier. A positive D.O. is measured at the effluent weirs, proving the existence of aerobic conditions in the primaries. Sulfide formation is effectively prevented during aerobic conditions and H2S off-gassing has been minimized, solving the Districts odor problems at a fraction of the cost of the prior chemical treatment.
|Oxygen Uptake Rate||5-10||mg/L/hr|
|H2S Concentrations before||150||ppm avg.|
|Oxygen Dissolution Capacity||1800||ppd|
|D.O. at Cone Discharge||62||mg/L|
|D.O. at Effluent Weirs||8-12||mg/L|
|H2S at Effluent Weirs||0||ppm|
Become a leader in water treatment.
ECO2 SuperOxygenation systems for water and wastewater treatment are designed and produced by Eco-Oxygen Technologies, LLC headquartered in Indianapolis, Indiana. The technology is the pioneering effort of Dr. Richard Speece, Centennial Professor Emeritus of Civil and Environmental Engineering at Vanderbilt University.
The ECO2 oxygenation method is a simple process based upon the scientific principle of Henry’s Law. No chemicals and no moving parts other than standard industrial water pumps are used. The result is a robust, reliable, economically competitive and environmentally friendly technology.
In municipal applications, ECO2 technology eliminates hydrogen sulfide odor and corrosion by dissolving pure oxygen in wastewater at high concentrations (50-75 mg/l) which prevents the formation of hydrogen sulfide and the associated “rotten-egg” odor. This approach saves money on alternative chemicals, provides pretreatment and does not increase total dissolved solids. ECO2 engineers are presently focused on wastewater projects in Maine, Indiana, California, Kentucky and Texas.