Category: Resources

Sulfide Control with Cloevis Biofilm Removal Service

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Project Scope

A major city in Florida had been experiencing chronic hydrogen sulfide (H2S) odor and corrosion problems at a forcemain discharge manhole and further downstream at a lift station, resulting in community complaints and collection system corrosion. Furthermore, the forcemain was located in the median of a busy roadway with no place to store a permanent chemical injection system. USP Technologies (USP) performed a system trial utilizing Cloevis Biofilm Removal Service. The trial quickly reduced H2S to desired levels at both control points and eliminated all odor complaints.

Technology

Cloevis Biofilm Removal Service (Cloevis BRS) is an innovative technology offering that removes the biofilms that adhere to the inner surfaces of wastewater forcemain walls, including the underlying Sulfate Reducing Bacteria (SRB) that produce hydrogen sulfide. As a result, gaseous hydrogen sulfide (H2S) production is eliminated. The treatment requires an initial conditioning period when the biofilm that harbors the SRB’s is removed, followed by maintenance treatments that are repeated as monitored lines show signs of SRB reformation.

Control of H2S has been achieved in wastewater collection systems with the utilization of many different technologies such as oxidation, precipitation, pH adjustments and vapor-phase systems. Cloevis BRS offers the benefits of lower cost, avoidance or minimization of on-site chemical storage, is unaffected by sulfide loading, retention time or oxygen uptake and has no labor/ maintenance demand. Other benefits include complete removal of sulfide odors for up to three weeks after treatment cycle and elimination of methane production within the treated segment as well as no downstream adverse impacts due to residual treatment chemicals. In addition, the effective cost of Cloevis BRS is similar to caustic shocking and less than conventional continuous chemical feed alternatives such as nitrate and iron salts.

Solution

The City’s forcemain length is 8,600 feet with a diameter of 8-10 inches and a retention time of 4-6 hours. It has a wastewater flow of 0.128 MGD, and prior to Cloevis BRS treatment, had baseline H2S vapor levels at 50-119 ppm and total liquid sulfide levels at 7.8 mg/L at the control location.

The initial conditioning period involved two separate 24-hour treatments which were completed two days apart. Maintenance treatments included one 12-hour treatment after the first 12 days and one 8-hour treatment after an additional 24 days. Ongoing maintenance Cloevis BRS treatments are completed every 3-4 weeks, depending on the rate of biofilm regeneration. Since the initial conditioning period, H2S average levels have steadily been at 5 PPM or less at the forcemain discharge manhole and sulfides at the downstream lift station have been greatly reduced. Additionally, odor complaints have ceased at these locations since USP began Cloevis BRS treatment.

Read More Download Sulfide Control with Cloevis Biofilm Removal Service (pdf)[/vc_column_text][/vc_column][/vc_row]

Biosolids Odor Control via Peroxide Regenerated Iron –PRI-TECH® Technology

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Project Scope

A field demonstration was initiated in February 2014 by the Suffolk County Department of Public Works (SCDPW) to quantify the impacts of Peroxide Regenerated Iron-Technology (PRI-TECH®) as a more economic approach in maintaining odor control in the solids handling phase at the Bergen Point Wastewater Treatment Plant (WWTP).

For approximately the last 30 years, the SCDPW Bergen Point WWTP has treated H2S and reduced sulfur compound-based odors in the sludge handling phase at the facility with potassium permanganate (KMnO4). The sludge handling phase includes unstabilized sludge waste from three locations: sludge from the primary clarifiers; thickened waste activated sludge; and chemical sludge from the facility’s scavenger sludge collection system. The three streams are co-mingled in a 0.25 million gallon capacity sludge blend tank (SBT) that is turned over approximately every 24 hours. The blended sludge is then pumped from the SBT to belt filter presses where it is dewatered and sent via screw conveyor to trailers located outside of the solids handling building. Unstabilized sludge has many more odor causing compounds versus digested sludge so the program needed to be capable of treating odors at all stages of the solids handling operation up to and including the off-site disposal facilities.

Suffolk County explored a PRI-TECH® demonstration program in an effort to achieve equal or better performance than the historical potassium permanganate odor control program while reducing operating costs. This demonstration evaluated the use of PRI-TECH® for controlling sludge odors, composed mainly of hydrogen sulfide gas and reduced sulfur compounds (mercaptans, etc.), while maintaining the belt filter press operation.

Technology

PRI-TECH® is a proprietary odor control technology that utilizes iron salts and oxidants in a fashion that reduces sulfides to elementary sulfur and reduces sulfur compounds to non-odorous compounds. This program was implemented by adding ferrous chloride (FeCl2) as the primary sulfide control agent into the primary sludge line upstream of the sludge blend tank. Hydrogen peroxide (H2O2) was added downstream at the sludge blend tank recirculation pumps to regenerate iron from ferrous sulfide (FeS) to either free ferrous and/or ferric iron. The H2O2 was also added to the online belt press feed pumps discharge piping to provide additional iron regeneration, oxidation of odorants and durational odor control. The iron also acts as a catalyst to allow the hydrogen peroxide to quickly and efficiently oxidize reduced sulfur compounds.

Solution

Odor control performance was analyzed by measuring liquid sulfide and mercaptan levels through a “shake” test in which these compounds are stripped into the vapor phase and analyzed with either OdaLog® portable gaseous hydrogen sulfide (H2S) instruments or H2S and RSH colorimetric tubes. In addition, H2S was measured continuously in the headspace of the SBT with an OdaLog® vapor H2S datalogger that had cellular transmission capability to allow for collecting data without disturbing the instrument and to allow for alarm set points to be established. Qualitative and quantitative monitoring of the dewatered biosolids trailer staging area was also performed. After program optimization during the demonstration period and ongoing operation, there were little to no recorded sulfides or mercaptans in the treated sludge from the SBT via shake test analysis. H2S levels were statistically similar in the SBT headspace averaging 0.2 ppm with a peak of 9 ppm under PRI-TECH® operation versus an average of 0.2 ppm with a peak of 14 ppm under the prior year’s KMnO4 operation.

The program monitoring was expanded beyond the plant to the outside disposal sites. Analytical methods for evaluating specific odor compounds were not available at any of the disposal sites. Durational odor control was evaluated based on subjective experiences and qualitative feedback of the operators at the disposal sites. According to operators, optimization of the program, which included the use of targeted dosing profiles, produced a reduction in odors at the disposal sites.

An additional benefit of the PRI-TECH® program is the potential to generate ferric iron (Fe3+) coagulant when the proper amount of H2O2 is added, which could assist in sludge dewatering and in producing higher percent solids in the pressed filter cake. Ferric iron is generated through the reaction of ferrous iron and hydrogen peroxide. During the demonstration period and ongoing operation over the first year, polymer use rates were unaffected and an increase in percent solids was noted in the filter cake from a comparable period the previous year.

Read More Biosolids Odor Control via Peroxide Regenerated Iron –PRI-TECH® Technology[/vc_column_text][/vc_column][/vc_row]

Biosolids Odor Control at Holding Tank and Belt Filter Presses via Hydrogen Peroxide

Project Scope A Midwest wastewater treatment plant was struggling with problematic hydrogen sulfide (H2S) levels at two points within their facility arising from biosolids processing. The factors driving the need for H2S control included worker safety, corrosion of electronics and concrete, implied regulatory limits and odor control. Along with normal residential and commercial flows, the facility also receives unpredictable slugs of high biological oxygen demand (BOD) wastewater from agricultural industries and handles septage hauler loads from a wide radius. USP Technologies (USP) implemented a full-service hydrogen peroxide (H2O2) solution with operator-adjustable dosing options to account for the unpredictable sulfide loadings and to lower H2S to acceptable levels at both their biosolids holding tank and dewatering building. Technology H2O2 is ideally suited to remove H2S from wastewater solids, provided that sufficient contact times are available – typically 2-5 minutes prior to the dewatering device. The efficiency of treatment depends upon the available reaction time, the initial level of H2S and the relevance of non-H2S odors. Under optimal conditions, effective dose ratios are about 5 parts H2O2 per part aqueous sulfide, and can be reliably estimated through beaker tests. The chemical reaction is as follows:

H2S + H2O2 → S0 + 2H2O

Background A biosolids holding tank receives all biosolids awaiting dewatering at the plant’s two belt filter presses. The tank is generally emptied every one to three days depending on biosolids generation rates correlated with industrial discharge volumes. The biosolids entering the tank, especially from the gravity thickeners, contain a significant sulfide load throughout the entire year. The holding tank employs mechanical mixing and aeration to minimize further sulfide generation, however, this causes extreme volatilization of H2S, exceeding 500 ppm. Previous control methods, including iron salt addition and “in-situ scrubbing” using a hydroxyl ion generating system only provided limited success in achieving desired targets. Compounding the challenge, the radicals generated interfered with the proper measurement of H2S. From the holding tank, biosolids are pumped to a dewatering building housing two belt filter presses. The turbulence of these belt filter presses causes most of the sulfide present to volatilize. A wet scrubber was installed and used for years to control the H2S, however, by 2014 it was at the end of its serviceable lifespan. Solution USP was invited to visit the facility to determine a more effective treatment strategy. Bench scale dose response tests utilizing shake tests were then conducted to determine theoretical hydrogen peroxide dosing needs and possible reaction times from several injection points. The optimal injection point was determined to be at the biosolids pump outlet, which provided approximately 3 minutes of reaction time before reaching the belt filter presses. Shortly afterwards, a full-scale H2O2 storage and dosing equipment system was installed. The H2O2 pumps were connected by relays to the biosolids pumps to ensure that H2O2 only dosed while the biosolids pumps were running. The program was demonstrated to be effective within the first hour of operation, with H2S levels brought down below 1 PPM both above the belt filter presses and within the dewatering building’s main room. The program continued with dosing rates throughout the first six months ranging from 1.5 to 6 gallons/hour. In addition, the operators were trained on how to both raise and lower dosing rates based on the observed H2S levels to mitigate variable industrial loadings. The removal of H2S from the dewatering facility eliminated the need for a costly replacement of their wet scrubber, and the customer invited USP to co-present our success story at their state conference. Read More Biosolids Odor Control at Holding Tank and Belt Filter Presses via Hydrogen Peroxide[/vc_column_text][/vc_column][/vc_row]

Biosolids Odor Control via Sodium Chlorite and Calcium Nitrate

Project Scope In upstate New York, a wastewater treatment facility historically utilized potassium permanganate to control odors at two locations in their biosolids processing operations. The first location was into the waste activated sludge (WAS) fed to a gravity belt thickener. The second location was into a mixed stream of primary sludge and thickened WAS blended in holding tanks and pressed before incinerating. In October 2014, the plant’s incinerator went down. Pressed solids were hauled off-site for disposal in a landfill. The plant began to receive odor complaints from the truck drivers and the landfill personnel, so the treatment rate of permanganate was doubled. This attempt at durational odor control was unsuccessful and the cost was $480,000 per year. The plant had been using a nitrate product for durational odor control in its collections system and learned from a nearby plant about USP Technologies’ successful application of a sodium chlorite based oxidant blend (chlorite) for immediate odor control supplemented with a nitrate solution (nitrate) for durational odor control. USP Technologies (USP) was then brought in to trial a similar solution. Technology Chlorite oxidizes hydrogen sulfide and organic odors without producing any harmful by-products such as chlorinated organics. Chlorite is very fast reacting, on the order of seconds, with hydrogen sulfide and organic odor compounds. As a result, it can be added directly to the sludge in the feed lines prior to the presses. The chemical reaction at neutral-acid pH: <p” style=”text-align: center;”>2 H2S + NaClO2 → 2 S<>0 + HCl + NaOH + H2O and at alkaline pH:

S<>2- + 2 NaClO2 → SO<>42- + 2 NaCl

Neutral-acidic conditions are favorable, as it only requires 3 mg/L sodium chlorite per 1 mg/L sulfide. Like permanganate, chlorite is not as effective at durational odor control, so nitrate was selected to perform this role. Sulfate reducing bacteria, under anaerobic conditions (as is the case in sludge holding tanks), typically use sulfate as a source for oxygen. When nitrate is present, however, the bacteria will preferentially select nitrate as its source of oxygen, preventing the sulfate from being reduced to sulfide and subsequently preventing the formation of hydrogen sulfide gas. Also, with an alternative oxygen source, other common bacteria can now consume dissolved sulfide ions and oxidize them back to sulfate and/or elemental sulfur, further reducing sulfide available to form hydrogen sulfide gas. Solution USP replaced the two potassium permanganate dosing locations with chlorite, and a separate nitrate dosing location was installed at the presses. Three 1,000 gallon tanks were installed for chlorite as well as a 14 gph diaphragm chemical metering pump at each dose point, which was interlocked into the plant’s SCADA system. At the gravity belt thickeners, the H2S levels were typically low but there are other problematic organic odors which are effectively oxidized with chlorite. At the belt filter press, H2S gas levels were higher (35-55 ppm) since the primary and waste activated sludges fed to the press typically sit in holding tanks for anywhere from a day to two weeks. The plant has ventilation hoods above each press that bring the gas to a scrubber, but the odors in the room were still strong enough to cause discomfort to the operators in the vicinity. An H2S monitor was hung at the press for continuous monitoring of H2S. Once the chlorite feed system was installed, sulfide in the sludge was able to be effectively oxidized, reducing the H2S gas at the press from 35-55 ppm down to 0-3 ppm. Figure 1 shows the effect of the chemical program. Additionally, as the data towards the right hand side of the graph depicts a point in time when the chemical feed was lost (a valve was closed). When not incinerated, the dewatered solids are hauled off-site for disposal at a landfill. The potassium permanganate provided very little, if any, odor control once the solids were loaded into the trucks, leading to many odor complaints. The addition of nitrate at the belt filter press via a 2,500 gal storage tank and dosing system proved to be effective as it completely eliminated further odor complaints. It is the plant’s plan to stop using their incinerator in March 2016, at which point nitrate will be used continuously. Read More Biosolids Odor Control via Sodium Chlorite and Calcium Nitrate

Vapor Fogging Technology for Hydrogen Sulfide and Mercaptan Control

[vc_row][vc_column][vc_column_text] A Southwest wastewater treatment facility was experiencing vapor hydrogen sulfide and mercaptan odors in the headspace of one of their pump stations. USP Technologies (USP) provided a proprietary vapor fogging technology (VFT) which involves fogging a dilute mixture of hydrogen peroxide (H2O2) and sodium hydroxide (NaOH) into the enclosed vapor space to oxidize H2S and mercaptan related odors. The process consists of two chemical storage/feed modules, a solution make-up tank, and a fogging apparatus. The underlying principle is absorption of gaseous H2S into an alkaline water solution, with concurrent oxidation of the absorbed H2S. The principles of operation are the same as those used in packed (and mist) tower odor scrubbers. The fogging systems are designed to deliver the appropriate amount of each chemical into the headspace to treat the vapor H2S and mercaptan loading on a continuous basis. USP provides a full-service project delivery scope for all the VFT and H2O2 equipment components, program management, application services, equipment maintenance and operations support. Other vapor fogging technology applications include treatment plant headworks, pump station wet wells, gravity sewers, and biosolids storage tanks.[/vc_column_text][/vc_column][/vc_row]

PENNSYLVANIA ISCO PROJECT – TOTAL CHEMICAL MANAGEMENT PROGRAM

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Total Chemical Management for Remediation

A remediation company was contracted to perform a cleanup of an abandoned gas station in south central Pennsylvania. The consulting engineer and the remediation contractor selected a treatment program utilizing In-Situ Chemical Oxidation (ISCO) as the preferred treatment technology. Due to the magnitude of the contamination and the widespread nature of the groundwater contamination, significant quantities of chemical (hydrochloric acid, ferrous sulfate, hydrogen peroxide, and sodium persulfate) and equipment were required to execute the site remediation. The scope and structure of the project required that a high volume of multiple chemicals be mobilized quickly which created a significant operational and cost challenge for the contractor. USP Technologies developed a Total Chemical Management program to efficiently, and cost-effectively, execute the project.

Solution

Based on the requirements for the project, USP developed a Total Chemical Management program to meet project schedules and budget objectives, which included the following:

Site Analysis and Hazards Review

USP engineering personnel worked closely with the remediation contractor to evaluate and plan for the specific hazards of the project site. Equipment was selected to ensure the chemical containment site security provided additional public protection. In addition, a water storage tank for emergency response and to support product dilution requirements was required as only a restricted-flow water source was available.

Read More

Download Case Study_Pennsylvania ISCO Project-17-HR (pdf)

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Supplemental Dissolved Oxygen, Rapid Response, Drum Conversion

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A Gulf Coast Refinery was using hydrogen peroxide (H2O2) in 55-gallon drums at their WWTU Bio Unit to supply supplemental dissolved oxygen (D.O.) to maintain target D.O. levels in the aeration basins during high COD loading periods. The drums were stored on wood pallets, which violated industry safety standards and also required handling (changing out the drums), which increased the risk of spills and exposure to operators. Furthermore, during a turnaround of an upstream unit, higher COD loading depleted the dissolved oxygen level in the WWTU Aeration Basins, resulting in ineffective treatment.

The refinery approached USP Technologies (USP) to engineer a bulk H2O2 chemical dosing system sized to meet the plant’s D.O. demand. USP responded to the refinery’s immediate need by quickly mobilizing a four-person Project Team that included a local account manager and experts in the areas of technical applications, equipment system design and equipment installation/maintenance.

The team installed a USP Rapid Response System consisting of a 5,000-gallon temporary storage trailer and a modular dosing control system. Upon the addition of Refinery Grade 27% H2O2, a class 1 oxidizer, to influent of the WWTU Bioreactor System, the D.O. target was maintained during the high COD loading period.

Once the temporary system was commissioned, the USP Project Team turned their attention to providing a permanent full service chemical storage and dosing system including a 5,000-gallon double-wall HDPE tank, dual pump dosing module, chemical, field service and monitoring system.

USP worked with the plant’s engineers to determine the optimum dose point as well as the proper location for the chemical storage tank. The changeover occurred following the plant turnaround and was completed by the USP Field Services Team without incident and without disruption to the treatment program.

Read More

Download Case Study_Refinery-GulfCoast-17-HR (pdf)

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Improve Safety and Operational Reliability

A steel mill was having problems with their existing H2O2 installations due to age and poor materials of construction, which led to significant routine downtime for repair. USP Technolgolies (USP) was asked to supply two turn-key equipment systems, thereby improving safety and operational reliability. USP supplied 35% hydrogen peroxide, one 1,100 gal turn-key storage and dosing system (pictured), one 6,500 gal turn-key storage and dosing system, remote tank monitoring & product inventory management services, equipment system installation, start-up and ongoing maintenance as well as applications support and safety training. The systems have been operating smoothly and without incident since installation.

Southeast Municipal Wastewater Odor Control

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Collections System Installation using PRI-SC®

This is a sample 7,800 gallon ferrous chloride (FeCl2) storage and dosing system installation within the collection system of a large Southeast municipality. The FeCl2 is used in conjunction with hydrogen peroxide as part of USP Technologies’ proprietary PRI-SC® process.

PRI-SC® is a combination treatment that integrates iron salts with hydrogen peroxide (H2O2) in a synergistic fashion. At the most basic level, PRI-SC® treatment may be viewed as an oxidant (hydrogen peroxide) regenerating the spent iron salt (FeS) in-situ, yielding fresh ferric (Fe3+) iron and colloidal sulfur. The combined treatment provides cost benefits superior to either chemical alone, while allowing greater flexibility as to the placement of storage and dosing facilities. Other benefits are accrued to the reaction, including: reduced solids (FeS) loadings, accelerated reaction rates and enhanced flocculation (in clarifiers). The process has particular benefit when employed for gravity interceptors, force main discharges and headworks treatment.

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USP Technologies

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Phone (804) 404-7696

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USP - Canada

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