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ABSTRACT
San Diego’s Point Loma WWTP is a 160 MGD (240 MGD permitted), 100% advanced primary treatment plant that has historically used iron salts for collection system sulfide control and chemically enhanced primary treatment. Beginning in 2006, a PRI-SC® (Peroxide Regenerated Iron – Sulfide Control) program was implemented by adding H2O2 at the intermediate pump station PS2 (in place of the FeCl3), and again to the plant influent (ahead of FeCl3 addition for CEPT). The application of PRI-SC® in the Point Loma system was designed to provide at least $685/day in cost savings, to be achieved through reduced ferric chloride use at PS2 and Point Loma, while improving sulfide control and CEPT performance. Since integrating the PRI-SC® program full-time in 2008, SDMWD is realizing savings of approximately $4,700 per day (~$1.72 million/yr) compared to the 2007 baseline iron salts program. At the same time, both sulfide control and CEPT performance has improved. The cost savings were helped by the hedging aspect of the PRI-SC® program – iron salt price volatility in 2008 and 2009 was upwards of 45%. The PRI program has reduced the total iron salt use from the 2007 baseline rate of 32.5 dry tons per day to approximately 19.3 dry tons per day in 2009, with the core savings coming from an overall reduction in ferric chloride use at PS2 and the treatment plant (Table 1). Significantly, ferric chloride use at PS2 was eliminated and, for CEPT, it was reduced from 24 mg/L to 10 mg/L (16.6 to 6.8 dry tons per day) with no loss in performance. In addition, total sulfide removal has improved over baseline levels, and average CEPT performance exceeds the permit levels at 89% for TSS and 65% for BOD, and effluent water quality has improved (with 60% less spent iron (as FeS) present in the ocean discharge). For the most part, digester biogas H2S levels were maintained below the permit requirement of < 40 ppm, but required approximately twice the baseline FeCl2 feed rate. Even so, the overall program has maintained the stated savings benefit.
KEYWORDS: Sulfide control, iron salts, Chemically Enhanced Primary Treatment (CEPT), hydrogen peroxide, PRI-SC, Peroxide Regenerated Iron.
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Download San Diego PRI-TECH – WEFTEC 2010 (pdf)[/vc_column_text][/vc_column][/vc_row]
Abstract
Corrosion of collection system piping and components has become a big problem for many municipalities trying to handle growth while obtaining the maximum service life for existing collection system infrastructure. The goal of this paper is to present the results of a trial initiated in August 2005 by The Regional Municipality of York (York Region) to quantify the impacts of Peroxide Regenerated Iron-Sulfide Control (PRI-SC) for control of hydrogen sulfide (H2S) in a long retention time section of the collection system. Results showed that PRI-SC technology was able to provide significant reductions of H2S over a 12 hour retention time section of the collection system. In most sections that were monitored, the reduction of H2S was over 90% in both the gas and liquid phase. The Aurora forcemain discharges displayed a unique dose response during the trial due to gas pocketing and high turbulence at the discharge structures. Further monitoring at manholes immediately downstream from the Aurora forcemain discharges confirmed the hypothesis of gas pocketing at the discharge structures. Sections further downstream of the areas of interest in the Southeast Collector also showed some reductions in H2S levels. As expected, the levels of reduction were less than in the upstream sections due to additional H2S loaded wastewater mixing with the treated wastewater.
Keywords The Regional Municipality of York, Hydrogen Sulfide, PRI-SC, Hydrogen Peroxide, Iron Salts, Odor Control, Corrosion Control, Collection System, Wastewater
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Download Region of York PRI-SC – WEAO 2006 (pdf)
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ABSTRACT
The City of Raleigh has been using ferrous sulfate (FeSO4) for years in their collection system for hydrogen sulfide and plant phosphorus control. Several years ago the Neuse River wastewater treatment plant upgraded their ultraviolet disinfection (UV) system to a higher intensity lamp technology. Although the UV system was equipped with mechanical wipers, manual cleaning by plant personnel was required due to the elevated iron levels carrying over to the disinfection stage coupled with the lamp sleeve’s higher temperature. In 2008, the City of Raleigh implemented Peroxide Regenerated Iron Sulfide Control (PRI-SC®) as a means to improve collection system sulfide control and maintain plant phosphorus removal while reducing the amount of iron salts in the collection system. PRI-SC® chemical savings were found to be $80,300 per year. Manual UV sleeve cleaning frequency was reduced from 2 weeks to 2 months, saving 32 man hours per cleaning or $25,600 per year.
KEYWORDS: Hydrogen Sulfide, PRI-SC®, Hydrogen Peroxide, Iron Salts, Alum, Odor Control, Phosphorus, Ultraviolet Disinfection
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Download Raleigh PRI-SC – WEFTEC 2010 (pdf)
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ABSTRACT
Iron salts are used by municipalities worldwide to control hydrogen sulfide within collection systems and to enhance primary clarification at treatment plants. However, the two uses are not synergistic: the product of the sulfide reaction is predominantly ferrous sulfide (e.g., FeS), a tightly-bound black precipitate that does not enhance flocculation. Further, dissolved sulfide present in the plant influent can scavenge free iron added to enhance clarification. Adding supplemental iron salt for both purposes would increase costs and potentially cause problems associated with e.g., higher volume solids production, reduced alkalinity, elevated salinity levels, and depleted dissolved oxygen. This paper presents the results of a field trial conducted at the Orange County Sanitation Districts using a novel technology to moderate these shortcomings – Peroxide Regenerated Iron – Sulfide Control (PRI-SCTM, patent pending). The combination treatment involves adding an iron salt at the upper reaches of the collection system and hydrogen peroxide at points downstream. The process may be viewed as an oxidant (H2O2) regenerating the spent iron salt (FeS) in-situ – yielding ferrous / ferric iron and colloidal sulfur. The study involved three major interceptors and the results show the PRI-SC technology met the control objectives at a significantly lower cost than other commonly used chemical technologies. Further, much of the ferrous salt added in the collection for sulfide control was shown to converted to hydrous ferric oxide at the treatment plant for enhanced clarification purposes. OCSD has since extended the field test into a full year evaluation.
KEYWORDS Hydrogen sulfide, odors and corrosion, iron salts, hydrogen peroxide, enhanced clarification
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Download OCSD PRI-SC – WEFTEC 2003 (pdf)
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ABSTRACT
The Orange County Sanitation Districts (OCSD) currently utilize PRI-SC™ technology to control hydrogen sulfide emissions within its collection system. With PRI-SC™, ferrous chloride (FeCl2) is added for sulfide control and then the combined iron is regenerated using hydrogen peroxide (H2O2). OCSD also adds ferric chloride (FeCl3) at its treatment plants to enhance solids separation (CEPT). We previously reported on the improved sulfide control efficiencies in the collection system using PRI-SC™; however, little data were available at the time on regenerating that iron a second time (at the treatment plant) to benefit CEPT. This paper discusses the economic and performance benefits of doing so using hydrogen peroxide and bleach at OCSD Plant No. 2. The study involved beaker tests, jar tests and field trials, as well as an analysis of the historical plant records.
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Download OCSD PRI-CEPT – WEFTEC 2005 (pdf)[/vc_column_text][/vc_column][/vc_row]
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ABSTRACT
In August of 2012, Monroe County DES initiated a demonstration of Peroxide Regenerated Iron – Sulfide Control (PRI-SC®) technology as a performance improvement over the existing hypochlorite and hydrogen peroxide odor and corrosion control program. This demonstration was designed to control hydrogen sulfide (H2S) odors and corrosion along a line from Mill Seat Landfill PS where landfill leachate is introduced into the collection system along the Churchville force Main and gravity line (hereafter referred to as the “Churchville Line”) through to the Gates-Chili-Ogden (GCO) pump station. The program was specifically designed to moderate peak sulfide levels at critical points to lessen and eliminate odor complaints as well as moderate corrosion. It was designed to dovetail with peroxide feed at the GCO pump station to reduce the H2S loading entering the GCO Lift Station and reduce peroxide usage for sulfide control further downstream to the critical odor control point at Shaft 2. Shaft 2 is located on a small green area in the middle of a densely populated residential section of Rochester and was heretofore a source of multiple odor complaints.
The demonstration of PRI-SC® technology from the Mill Seat Landfill PS through the Churchville line to the GCO Lift Station provided odor and corrosion control in an additional 22.5 kilometers (14 miles) of pipe along the Churchville force main and gravity line, from Mill Seat PS to the GCO PS, while enhancing the GCO/Shaft 2 odor and corrosion control program at comparable cost to the current peroxide and bleach program.
KEYWORDS: Monroe County DES Pure Waters, Leachate, Hydrogen Sulfide, PRI-SC®, Hydrogen Peroxide, Iron Salts, Odor Control, Corrosion Control, Collection System, Wastewater
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Download Monroe PRI-SC – Leachate – WEF Odor Conference 2013 (pdf)[/vc_column_text][/vc_column][/vc_row]
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ABSTRACT
The results of a full-scale trial initiated in May 2006 by the Manatee County Southwest Water Reclamation Facility are presented, and the impacts of peroxide regeneration of spent iron salts on the removal of hydrogen sulfide (H2S) from anaerobic digesters at the SWWRF are examined. Treatment with hydrogen peroxide was initiated in a thickened primary sludge line containing an average 300 Lbs/day Fe (primarily as FeS) and 80 mg/L dissolved sulfide. Prior to treatment, dissolved sulfide levels in the primary digester averaged 20 mg/L and were found to drop to < 0.1 mg/L throughout the course of the trial. The vents of the primary digesters exhausted biogas containing an average 200 ppm H2S. After treatment, biogas H2S concentration reduced to 20 ppm on average. Within two sludge ages, similar effects were noted in the secondary digester. Additional positive changes were noted in the volume and quality of biogas produced, and in finished biosolids quality.
KEYWORDS Anaerobic digestion, odor control, corrosion control, hydrogen sulfide, hydrogen peroxide, iron salts, mercaptan, peroxide regenerated iron…
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Download Manatee PRI-DE – WEFTEC 2007 (pdf)[/vc_column_text][/vc_column][/vc_row]
Summary
This paper will present results of an odor control field study initiated in July 2008 by Lexington-Fayette Urban County Government (LFUCG) to quantify the impacts of iron and peroxide injection in the collection system on liquid and gaseous sulfide levels as well as the secondary benefit of phosphorus removal and sodium aluminate savings at the treatment plant.
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Download Lexington – WEFTEC abstract 2009 (pdf)[/vc_column_text][/vc_column][/vc_row]
ABSTRACT
Historically the technology to continuously monitor “odors” or odor units in real time has not been available. Since October 2009, the Hampton Roads Sanitation District (HRSD) has been successfully demonstrating new technology that is performing real time odor monitoring of the odors from the uncovered portion of the aeration basin at HRSD’s Chesapeake-Elizabeth wastewater treatment plant in Virginia Beach, Virginia.
The odorous emissions from the aeration tanks are measured continuously by a network of three OdoWatch® electronic noses. The network measures the odors continuously at 5-second intervals (dilution to threshold or odor concentration). The real time odor monitoring allows us to know the level of odors from the aeration tanks and potential off-site impacts with and without chemical dosing, instantaneously or historically. Chemical dosing of peroxide and iron is being performed at the raw influent to provide seasonal odor control of the uncovered portion of the aeration basin. The odor monitoring system includes a weather station so as to use dispersion modeling to map the odor plumes from the aeration basin in real time.
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Download HRSD – WEF Odor Conference 2012 (pdf)