Chemical Replacement with IER’s Gener-Ox™
Chemical-Free Odor and Corrosion Control Technology
History:

Gener-Ox MTS-100-20 Unit (150 GPM)A major municipality located in a populated Eastern Montana community receives approximately 8.5 million gallons per day of wastewater from a wide distribution area. The POTW plant’s influent stream includes 1.2 million gallons of relatively high strength industrial wastewater containing very high levels of soluble organic contaminants. This specific stream is transported approximately 5.5 miles to the local POTW head works. The initial mile of this sewer line is a force main, with the remaining 4.5 miles being gravity flow as it is comingled with other municipal and industrial wastewater. Due to the inherent warmth of the effluent stream, the high BOD content, and the lack of dissolved oxygen, anaerobic microorganism activity in the force main is very high. This anaerobic activity results in objectionably high concentrations of Hydrogen Sulfide (H2S) and other volatile organic acids (VOA’s) in the force main and gravity sewer as the stream passes several manholes in route to the local POTW. Concerns related to the toxic odors, as well as the extremely corrosive nature of H2S (due to the gas-phase conversion of H2S into H2SO4), forced the facility to explore all available options for the minimization of H2S levels in the effluent stream. Because of the significant transport distance and the high concentration of organic nutrient in the stream, the effluent rapidly builds a high concentration of H2S and VOAs as it travels toward the receiving facility. These volatile gases escape from solution upon exposure to turbulence at the point of force main break to gravity. This specific location is a manhole that upon gas-phase sampling was shown to pose a high risk to personnel for exposure to dangerously high H2S levels.

Without chemical treatment, H2S at this location was measured at levels ranging as high as 500 ppm. Prior to becoming aware of IER’s Gener-Ox™ System, the company was attempting to control the H2S problem by using a nitrate-bearing chemical treatment formulation. This very costly approach to H2S control resulted in annual costs in excess of $100,000. Of equal importance, the chemical treatment was still not providing reliable performance at the most critical manhole location. In some instances, the H2S levels even during chemical treatment were found to often exceed 100 ppm The never-ending chemical costs associated with treating the symptom of the problem (providing an alternate chemical feed to convert the anaerobic bugs from “sulfate reducers” to “nitrate reducers”) rather than addressing the root cause of the problem (anaerobic conditions) forced the company to investigate many other treatment options, including IER’s Gener-Ox™ technology.

Solution:

IER has developed a proprietary chemical-free, dissolved oxygen technology which is designed to convert anaerobic water systems into a fully aerobic environment. By converting force mains and sewer lines from anaerobic to aerobic conditions, the anaerobic organisms are either facultatively converted into aerobic microorganisms, or they are unable to survive and simply expire. This innovative technology, trademarked as Gener-Ox™, was installed at the location of the wet well effluent from the industrial facility in January of 2009. The result was an immediate and complete conversion of the system’s entire 5.5 mile wastewater sewage transport line from an anaerobic, H2S-producing environment to a fully aerobic, non-sulfur reducing environment. Prior to discharge to the pressurized force main, approximately 20% of the lift station’s effluent wastewater was passed through IER’s Gener-Ox™ system. Under high pressure conditions, gas phase oxygen was introduced into the Gener-Ox™ side stream and converted into a very high concentration of dissolved oxygen (DO) in the wastewater. This high DO stream was then re-introduced into the bulk wastewater effluent entering the pressurized force main. After just a few hours of contact time within the sewer line system, the H2S levels at each manhole sampling location ranged between 0 and 3 ppm. This very low detectable range of H2S has been held consistently throughout the summers of 2009 and 2010. In addition, a detectable DO residual has been consistently analyzed from wastewater samples as they are obtained daily from each manhole sampling point. With such dramatic H2S minimization, manhole and concrete pipe corrosion concerns have been dramatically reduced.

Overview:

IER’s Gener-Ox™ system for odor and corrosion control simply takes advantage of a pressurized environment (such as a force main) to drive high concentrations of a dissolved gas into solution, not unlike the solubility of carbon dioxide within an unopened bottle or can of pop. When the gas of choice is oxygen, the resulting dissolved oxygen in the wastewater becomes the primary oxygen-containing source for bacteria, converting the population from anaerobic to aerobic. This case study describes the benefits that were achieved by replacing the continuous feed of a relatively expensive treatment chemical with IER’s chemical-free Gener-Ox™ system. The system operates by utilizing Mother Nature’s oxygen supply, rather than having to deliver chemicals throughout a community to treat specific lift stations. Aside from the initial capital costs, the only operational costs associated with the Gener-Ox™ system are the utility costs. The utility costs associated with this system’s operation are limited to that necessary to operate a 20 HP centrifugal supply pump, a 30 HP air compressor, and a 115 volt oxygen concentrator, which is based on molecular sieve adsorption technology. Under full load conditions, the result is a monthly operational cost of approximately $1500 based on electrical costs of $0.065 KWH. This cost represents less than 20% of the previous yearly cost of ~$100,000 for the less effective and more cumbersome chemical treatment approach.

In brief, IER’s Gener-Ox™ odor/corrosion control system offered this client:
A dramatic reduction in Hydrogen Sulfide to either non-detectable or very low levels within minutes of initializing the Gener-Ox™ system, which has now been maintained for 18 months of application.
A substantial wastewater dissolved oxygen (DO) residual maintained from the facility’s Gener-Ox™ application point throughout the entire 5.5 miles of sewer line, which initiates the activated sludge process for the POTW.
Dramatically reduced gas-phase corrosion in the bell of concrete transport pipe and manholes throughout the treated sewer line.
Savings of approximately $80,000 per year in pure chemical/operational costs by elimination of the less-effective nitrate-bearing chemical treatment, resulting in a projected return on investment of less than two years.