Odor Control and Disinfection

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Dual technology reactor controls odors

Problem

Odors from two pump stations in Fort Myers Beach, Fla., were aggravating residents and tourists. Lee County Utilities turned to BioAir Solutions to provide a solution that did not disrupt the scenery or require frequent maintenance and chemicals.

 

Solution

The two-stage EcoPure system handles 1,000 cfm of air containing high concentrations of hydrogen sulfide (H2S) and other organic sewage odors. The unit combines a biotrickling filter of EcoBase plastic media with a carbon polishing stage. Primary treatment occurs in the biotrickling filter with its synthetic media consisting of uniform surface area, flow distribution, and biomass contact time.

Flow channels in the filter eliminate plugging. Controlled air turbulence optimizes mass transfer of inorganic and organic odorous compounds and proliferates the growth of the odor-removing bacteria. Combining activated carbon with the unit’s air purification power extends the carbon life up to 10 times over typical carbon filters for low emissions without high cost.

 

Result

The compact, quiet reactor removes more than 99.5 percent of H2S and more than 95 percent of all odors in the airstream. Minimal maintenance keeps operating costs low. 856/258-6969; www.bioairsolutions.com.

 

Manatee County solves odor problems

Problem

Seasonal odor complaints taxed the staff at the Manatee County (Fla.) Wastewater Treatment and Collection Department, and H2S gas corroded the infrastructure. Initially, the department addressed the complaints on a case-by-case basis, but, “We couldn’t keep up,” says Jim Marble, collections systems superintendent. “We needed to do more testing to achieve optimum performance from our chemicals.”

 

Solution

After working with Siemens Water Technologies, the county outsourced the operation rather than add seasonal personnel. Based on data collected at the site, Siemens Water Technologies Odor Control offered a comprehensive solution of the company’s liquid and vapor products under a single contract. Liquids targeting odor compounds included BIOXIDE, BIOXIDE-AQ, and ODOPHOS/ODO-FREE. Custom-designed feed systems dosed the sewers with them. Vapor technologies included wet scrubbers, biofilters, and carbon adsorption.

BIOXIDE solution reduced dissolved H2S concentrations of more than 50 ppm to less than 0.1 ppm. BIOXIDE-AQ solution, a combination of AQUIT and BIOXIDE solutions, reduced dissolved H2S levels from 50 ppm to less than 0.1 ppm in force mains, wet wells, and gravity interceptors. Aqueous solutions of ferric-ferrous sulfate (ODO-FREE) and ferrous sulfate (ODOPHOS) controlled H2S to 0.50 ppm levels.

Siemens used 12 of its technologies at various sites around the 22 mgd system. It maintained the systems and the county monitored the results. Products and services were billed on a consumption or time basis to eliminate capital cost.

 

Result

The solution ended consumer complaints and slowed corrosion of the infrastructure. The county calls a single entity to address odor issues. Records indicate that new problems are resolved in less than two weeks and old problems at existing sites within 24 hours. 866/926-8420; www.water.siemens.com.

 

Biofiltration system removes 99 percent of H2S

Problem

Odor sampling of the organic media biofilter in a pump station in Orange County, Fla., showed 5,500 ppm detection threshold in the outlet from residual H2S. Controlling odor was important to the Orange County Utilities Water Reclamation Division, as the station is near a large residential development.

 

Solution

The utilities selected the MÓNASHELL biofiltration system from Bord na Mona Environmental Products U.S. The waste airstream is directed into recirculating water within the unit. As it is pulled through the system rather than pushed to reduce the risk of escaping odors, odorous compounds contact microorganisms on the seashell media that begin the odor reduction process.

The process continues with the seashells, which contain high levels of calcium carbonate that neutralize the acid byproducts of sulfide oxidation. The media’s physical, structural, and chemical properties allow for smaller filters and higher efficiencies than conventional biotrickling filters. Advantages include low pressure drop and energy costs, built-in pH control, and low water consumption. The long-lived media requires no additional nutrients, has high porosity, sustains high irrigation rates, and retains large quantities of water.

 

Result

Pilot testing of the unit verified that it removed more than 99 percent of H2S from the pump station. Reduced sulfur compound (RSC) testing indicated the system removed the most prevalent compound measured — methyl mercaptan. Remaining RSCs were 0.005 ppm and detected volatile organic compounds were 2 to 60 parts per billion by volume. 800/787-2356; www.bnm-us.com.

 

Oxidant regenerates spent iron salts

Problem

The City of Raleigh, N.C., used ferrous sulfate (FeSO4) in the collection system to control H2S and effluent phosphorus. When the Neuse River Wastewater Treatment Plant upgraded to a higher-intensity UV disinfection system, the mechanical wipers failed to clean the lamps because of the sleeve’s higher temperature and elevated levels of iron salts. Manual cleaning every two weeks required 32 hours.

 

Solution

In 2008, the city implemented peroxide regenerated iron sulfide control (PRI-SC) technology from US Peroxide by adding hydrogen peroxide (H2O2) at the Walnut Creek lift station to regenerate FeSO4 fed from three upstream locations.

The iron salt absorbs dissolved sulfide as it moves down the line. Intermittent injections of H2O2 regenerate the iron salt, allowing it to absorb additional sulfide downstream. A final regeneration site at the treatment plant provides rapid oxidation of sulfides to less than 0.1 mg/l dissolved sulfide in less than five minutes, H2S loading to the influent scrubbers. Hydrous ferric iron can be used for additional odor control in primary treatment or for enhanced flocculation in clarifiers.

US Peroxide provided all applications and field support to install the H2O2 feed. It also provided turnkey service including H2O2 supply, double-walled chemical storage system, dosing equipment, remote telemetry monitoring, data collection, dose rate adjustment, applications support, and reporting. The city maintained the existing ferrous sulfate sites and plant alum feed and collected data for raw and final phosphorus levels per the NPDES permit.

 

Result

The city saved $80,300 per year in chemicals and $25,600 per year in labor, as the UV sleeve required cleaning only every two months. 877/346-4262; www.h2o2.com.



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