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ABSTRACT

Historically, ferrous chloride (FeCl2) injection has been utilized to successfully control odors and corrosion within the sanitary sewer collection system of Fargo, North Dakota. However, increased odor complaints prompted an evaluation of the odor conditions present in the sanitary sewer system. Study results indicated that the current FeCl2 dosing rate was insufficient to control odors. In response, a number of liquid phase odor control treatment alternatives were evaluated. Due to the existing FeCl2 injection program, iron regeneration and improved odor control were realized through the innovative use of hydrogen peroxide. A program was initiated to demonstrate the efficacy of the proposed treatment strategy on a full-scale level. In response to improved sulfide treatment, reduced FeCl2 injection rates, and economic benefits realized during the demonstration program, the City of Fargo elected to incorporate the technology as part of their upcoming collection system improvements.

KEYWORDS: Odor Control, Hydrogen Peroxide, Ferrous Chloride, Hydrogen Sulfide, Dissolved Sulfide.

Read More Download Fargo PRI-SC – WEFTEC 2009 (pdf)[/vc_column_text][/vc_column][/vc_row]

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Abstract

The transition from splash fill and ACB fill to cellular plastic “high efficiency” film fill in cooling towers has reduced capital and operating costs. However, the generally tight and tortuous path that provides exceptional contact between air and water in these fills also makes them highly prone to fouling. In the US Power industry, environmental regulations limiting chlorine usage, inadequate or non-existent clarification and filtration equipment, and generally lower treatment levels exacerbate the difficulty of controlling deposit formation in the fill packs. Fouled fill sacrifices the “high efficiency” performance gains and, in advanced stages, results in fill collapse into the sump and expensive fill replacement. The purpose of this paper is to outline and review successful, pro-active fill cleaning techniques that preserve thermal efficiency and avoid fill replacement. Several case histories are provided.

Keywords: Cellular plastic fill, film fill, high efficiency fill, cooling tower, cleaning

Read More Download Effectively Cleaning Cellular Plastic Cooling Tower Fill – Electric Utility Workshop 2013 (pdf)[/vc_column_text][/vc_column][/vc_row]

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ABSTRACT

In 2008, the Green Bay (Wisconsin) Metropolitan Sewerage District acquired the De Pere Wastewater Treatment Facility and interceptors from the City of De Pere. Two of those interceptors received wastewater from paper mills exhibiting high biochemical oxygen demand and high temperatures. Mill wastewater contributed 80 percent of the total interceptor flows, making conditions highly conducive to sulfide generation. Control measures were necessary to prevent unacceptable hydrogen sulfide concentrations in the interceptors. A computer model was used, along with 7 months of collected field data, to assess the effectiveness of treatment alternatives. The calibrated sulfide generation factor in the model was lower but within a magnitude of the recommended value by Pomeroy-Parkhurst. To eliminate vapor phase hydrogen sulfide issues in one of the interceptors, a force main was installed to allow wastewater to be pumped from one of the mills directly to the treatment plant. A biological slime layer that formed in the force main appeared to inhibit sulfide generation or transfer of sulfide to the wastewater. The slime layer resulted in elevated force main pressures and lower flow rates. Hydrogen peroxide addition successfully reduced the slime layer. The two mills discharging to the second interceptor employed liquid phase chemical treatment using ferrous chloride and hydrogen peroxide to mitigate sulfide generation.

KEYWORDS: odor, hydrogen sulfide, paper mill, interceptor…

Read More Download DePere – WEF Odor Conference 2012 (pdf)[/vc_column_text][/vc_column][/vc_row]

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Abstract

Free Nitrous Acid (FNA) is the active agent underlying a new biofilm removal technology (“Cloevis”) for controlling sulfide production in wastewater force mains. The technology was developed at the University of Queensland and, after initial field testing in Australia, commercial field tests in the U.S. began in late 2015. These early test sites were chosen to reflect a range of force-main situations, including: short vs long retention times; small vs large wastewater flows; and force mains heretofore treated with nitrate, iron salts, or no treatment. In all cases, the Cloevis technology was able to bring the sulfide levels under target limits, although auxiliary (complementary) treatments are needed in two scenarios: where pre-existing sulfide enters the force main segment either through the influent flow or through a manifolded (interconnecting) force main; and where the candidate force main has accumulated deposits of fats, oils, and grease that coat and protect the biofilm. This paper will describe the Cloevis technology and discuss the results from three of the early field tests in the U.S.

Keywords

Sulfide Control, Corrosion Control, Odor Control, Force Mains, Biofilm Treatment, FNA, Free Nitrous Acid, Cloevis…

Read More Download Cloevis BRS – WEF Odor Conference 2016 (pdf)[/vc_column_text][/vc_column][/vc_row]

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Hydrogen Sulfide Control in Bio-Solids Processing with

    Hydrogen Peroxide – The Cedar Rapids Experience

By

Michael Fagan, Chester Szczucki  –  US Peroxide, Inc.

John Haase, Sam Kamhawy – Cedar Rapids Water Pollution Control Facility

  The City of Cedar Rapids Water Pollution Control Facility (WPCF) treats an average of 42 MGD of mixed industrial and domestic wastewater.  Due to the large percentage of industrial wastewater contribution (e.g. paper mills, corn processors, agricultural products), influent to the Cedar Rapids WPCF is “higher strength” than most municipal sewage, particularly with respect to BOD, sulfate, and nutrients.   These conditions result in efficient production of hydrogen sulfide (H2S) in both solid and liquid treatment processes, and thus create significant safety and operational challenges for the Cedar Rapids staff. One of the highest priority areas for improved H2S control was the bio-solids gravity belt thickener (GBT) building. During normal operations, H2S levels in the GBT building routinely exceeded the Cedar Rapids WPCF mandated levels for worker exposure (10 ppm).  Significantly, H2S spikes in the 100-200 ppm range have been measured directly above the gravity belt thickener table.  Due to these unsafe levels of H2S, shut down of the GBT’s and ventilation of the building was required before equipment maintenance or other work could be started.  This procedure negatively impacts the efficiency of the bio-solids processing operation.  High H2S levels in the GBT building over time has also caused severe corrosion of electrical components and equipment, and contributed to odors in and around the GBT building. Due to the safety and operational issues noted above, a program was undertaken to evaluate hydrogen peroxide (H2O2) oxidation of bio-solids sulfide prior to gravity belt thickening.  The objectives of this program were to: 1) Improve worker safety by maintaining GBT building H2S levels in the 0-2 ppm range 2) Reduce bio-solids processing “down time”, 3) Reduce corrosion and odors in the GBT building. This paper will present results from this ongoing program, which employs injection of hydrogen peroxide into the waste activated sludge line, several minutes ahead of the GBT’s.   Results from initial laboratory testing, through full scale implementation of this program will be reported. To date, the use of hydrogen peroxide has reduced H2S levels at the GBT’s by an average of  >90% which has maintained H2S in the GBT building to the target level of 0-2 ppm 95% of the time.  These significant reductions in H2S have accomplished the program objectives, e.g.:

• H2S levels in the GBT building are regularly maintained below Cedar Rapids 10 ppm exposure limits, resulting in safer working conditions in the GBT building.
• Routine equipment maintenance and other work in the GBT building can now be done without shutting down the bio-solids processing operation, improving efficiency.
• The environment in the GBT building is less corrosive. It is expected that this will extend the life of electronics and other equipment.
• Odors in and around the GBT building have been reduced

Further optimization of this H2S control program are underway, and include (bio-solids) flow pacing of the hydrogen peroxide metering pumps, and/or automated H2O2 dosing control based on gaseous H2S monitors in the GBT building.   Download Cedar Rapids – IWPCA Abstract (doc) Download Cedar Rapids – IWPCA Presentation (ppt)[/vc_column_text][/vc_column][/vc_row]