Kenel, Kelsey

Presented at WEFTEC 2023.

Titles from this speaker

Description: Being Good Neighbors: How Monitoring and Modeling Led to Plant Wide Odor Control...

Being Good Neighbors: How Monitoring and Modeling Led to Plant Wide Odor Control Improvements

Abstract

Prince William County Service Authority (PWCSA) owns and operates the H.L. Mooney Advanced Water Reclamation Facility (AWRF) which is located in a residential community with parks and a walking path at the property line. Odor control has been added and upgraded over the last 20 years at portions of the AWRF; however, PWCSA aims to further reduce odors. A design-build project is underway that will include odor control improvements. The project includes sampling and dispersion modeling odor sources, evaluating treatment technologies, and designing and constructing the chosen system. This paper will discuss the sampling, extensive dispersion modeling, and fence line goal development that led to the design and future construction of a 95,000 CFM centralized odor control facility

PWCSA owns and operates the H.L. Mooney AWRF which is located in a residential community. Odor control has been added and upgraded over the last 20 years at portions of the AWRF; however, PWCSA aims to further reduce odors. A design-build project is underway that will include odor control improvements. This paper will discuss the sampling, dispersion modeling, and fence line goal development that led to the design and future construction of a 95,000 CFM centralized odor control facility.

SpeakerKenel, Kelsey

Presentation time

15:30:00

15:50:00

Session time

15:30:00

17:00:00

SessionManaging the Third Effluent Part I

Session locationRoom N426b - Level 4

TopicIntermediate Level, Municipal Wastewater Treatment Design

Author(s)

Kenel, Kelsey

Author(s)K. Kenel 1; S. Spence 2 ; M. Welle 3; B. Balchunas 4; J. Maley 5; M.M. O'Shaughnessy 2;

Author affiliation(s)HDR 1; Prince William County Service Authority 2 ; HDR 3; HDR 4; HDR 5; 2;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2023

DOI10.2175/193864718825159037

Volume / Issue

Content sourceWEFTEC

Word count15

Description: Comprehensive Collection System Odor and Corrosion Control through Integrated...

Comprehensive Collection System Odor and Corrosion Control through Integrated Planning

Abstract

PURPOSE
The presentation will provide an overview of the City of Raleigh's Public Utilities Department, Raleigh Water (Raleigh Water) complex collection system odor and corrosion challenges, current approach to treating and handling odor and corrosion, and how modeling was used to evaluate hotspots and optimize treatment. The presentation will benefit the industry by providing integrated approaches to collection system odor and corrosion control assessment, design criteria, planning, and detailed treatment solutions through advanced sewer modeling.

PROBLEM STATEMENT
Raleigh Water is grappling with a complex and rapidly growing collection system with interceptors of varying age and materials, both concrete and inert. Due to the complexity and frequent changes, the system has areas at high risk of high hydrogen sulfide, potential odor nuisance, and corrosion. Raleigh Water maintains an active odor control program with the goal of addressing elevated and consistent odors within the wastewater collection system. The odor control program includes a liquid chemical feed program in which different odor control chemicals (ferrous sulfate, hydrogen peroxide, and calcium nitrate) are added to the wastewater at different strategic points within the collection system to reduce and/or suppress the formation of hydrogen sulfide. Routine monitoring of liquid and gaseous hydrogen sulfide levels is conducted to assess performance at the different dosage locations and to identify any needed adjustment to chemical feed rates. In addition to the chemical dosage program, Raleigh Water also has vapor phase odor treatment systems at several of its regional pump stations to treat the odorous air collected at the pump station. Raleigh Water's strives to build a programmatic system approach for odor and corrosion. Although the Raleigh Water has an expansive chemical dosing system in place that has had success, there are still gaps and areas in need of improvement. Raleigh Water recognizes these gaps and has a goal to optimize their system both for treatment and cost efficiency, while also minimizing elevated and consistent odors system wide.

BACKGROUND AND METHODOLOGY
Raleigh Water operates a collection system that spans over 2,500 miles of pipe, both gravity and forcemain, and conveys wastewater to one of three resource recovery facilities. Figure 1 shows Raleigh Water's collection system, locations of pump stations, dosing stations, and resource recovery facilities. The odor control treatment program is comprised of liquid treatment at more than 20 chemical dosing stations (varying chemical usage) and several vapor phase systems throughout the collection system. The chemical dosing stations throughout the collection system treat the system with different chemicals depending on the location. Calcium nitrate, iron, and peroxide are used throughout the system. In 2017, Raleigh Water completed an odor and corrosion control master plan that evaluated the ongoing treatment program for areas of improvement and potential areas in need of treatment. This was completed through extensive sampling, both liquid and gas phase, and collection system modeling. In 2022, HDR, The WATS Guys, and Raleigh Water worked together to build upon the findings from the previous master plan and assess Raleigh Water's collection system for odor and corrosion control using the Wastewater Aerobic/Anaerobic Transformation in Sewers (Mega-WATS) model. The Mega-WATS model was used for the project because it analyzes and solves complex in-sewer transformations including microbial-induced concrete corrosion, odor formation, and potential for nuisance risk caused by hydrogen sulfide air emissions from pressurized sections of the sewer. Additionally, the model can predict anticipated effects and results of utilizing hydrogen sulfide control strategies, both liquid phase and vapor phase throughout a collection system. The model was used as a key tool in an integrated master planning effort that began in January 2022 and will be completed in December 2022, providing integrated approaches to collection system odor and corrosion control assessment, design criteria, planning, and detailed treatment solutions through advanced sewer modeling. The analysis was done using two modeling scenarios:
1. 2022 average weather and flow conditions
2. 2025 projected average weather and flow conditions

The 2022 model was calibrated using 2015 sampling data as well as updated sampling data completed in June 2022. The model input parameters incorporated existing chemical dosing and vapor phase treatment information to represent field conditions and predict the level of hydrogen sulfide control within the system. The 2022 model findings were evaluated for corrosion risk and areas with high concentrations of hydrogen sulfide in comparison with known odor complaint locations.

RESULTS AND FINDINGS
The 2022 model results were used to determine odor and corrosion hotspots throughout the entire collection system. These hotspots were detected by assessing areas with model predicted hydrogen sulfide presence, known odor complaints, and/or model predicted corrosion. Plots similar to Figure 2 were used to define the hotspot areas and prioritize them based on parameters such as: hydrogen sulfide presence, odor complaints in the area, known high risk asset, high predicted corrosion rate, and known planned monitoring or replacement. The presentation will provide a more detailed assessment of the hotspots and how they were evaluated and prioritized from the modeling results. The 2022 odor and corrosion hotspots were used to develop over ten capital improvements solutions as well as potential operational changes. The developed solutions were primarily related to adding chemical dosing sites in areas with hydrogen sulfide hotspots that were not already being treated, as well as pilot testing different chemicals and combinations of chemicals along flow paths to assess for improved and optimized treatment. One specific flow path evaluated is made up of several oversized forcemains and has an overall detention time of more than 60 hours. The flow path currently has three chemical dosing sites that treat the line with calcium nitrate upstream and iron followed by peroxide downstream. Although his treatment combination has helped mitigate some of the hydrogen sulfide formation, there is still concern for corrosion and odor along the flow path. The project team completed a desktop evaluation on the flow path and found that the addition of a pH adjustment (to a pH between 8-9), such as magnesium hydroxide, upstream of the iron dosing improved the iron's precipitation capabilities with dissolved sulfide. The combination of pH adjustment followed by iron was predicted to be an effective chemical optimization strategy on other flow paths in the system as well. The model also predicted downstream pH with these chemical combinations matched would not adversely impact the resource recovery facility. The team has recommended pilot testing in various locations in the collection system to validate the treatment combination. This presentation will provide the detailed flow path findings, results, evaluation (economic and non-economic benefits), and recommendations that evolved throughout the project. The presentation will provide insight and potential mitigation solutions for other utilities experiencing problematic hydrogen sulfide levels, odorous air, ineffective chemical treatment or corrosion throughout their collection systems.

This paper was presented at the WEF Odors and Air Pollutants Conference, May 16-19, 2023.

SpeakerKenel, Kelsey

Presentation time

14:00:00

14:30:00

Session time

13:30:00

16:45:00

SessionModel, Monitor, and Treat: Controlling Collection System Odors

Session number8

Session locationCharlotte Convention Center, Charlotte, North Carolina, USA

TopicCollection System Odor Control

Author(s)

K. Kenel

Author(s)K. Kenel 1; M. Ward 2; J. Vollertsen 2; J. Bognar 3

Author affiliation(s)HDR1; The WATS Guys2; City of Raleigh3

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2023

DOI10.2175/193864718825158759

Volume / Issue

Content sourceOdors and Air Pollutants

Word count11

Description: Odors and Air Pollutants 2023 cover

Monitoring and Dispersion Modeling to Become Good Neighbors

Abstract

PROBLEM STATEMENT/PURPOSE: Prince William County Service Authority (PWCSA) owns and operates the H.L. Mooney Advanced Water Reclamation Facility (AWRF) in Northern VA. The AWRF is nestled in a residential community with parks and a walking path along the property line. The AWRF first implemented odor control in 2001, and subsequently upgraded the system in 2011 to provide odor control for preliminary treatment and solids thickening processes. To further reduce odors at the AWRF's property line and beyond, PWCSA is completing a design-build project that includes the assessment of odors at the AWRF through sampling and dispersion modeling, evaluation of odor control technologies, and the design and construction of the chosen system. The purpose of this abstract is to present the odor sampling, monitoring, and extensive dispersion modeling that led to the current design (2022) and future construction (2023) of a 95,000 CFM centralized odor control facility at the AWRF.

BACKGROUND:
The AWRF is located in Woodbridge, VA, approximately 30 miles outside Washington, DC and is in close proximity to several livable communities, nature parks, and walking paths. The AWRF is designed to treat 24 million gallons per day (mgd) average daily flow with current flows in the 14 to 16 mgd range. The AWRF has an existing packed tower chemical scrubber odor control system that treats odors from preaeration, screening, grit removal, and gravity thickening processes at the AWRF. Odorous air from solids dewatering and incineration are routed out of a high stack for improved dispersion. However, odor control improvements are needed to reduce odors within the AWRF site and reduce odor excursions into neighboring residential communities and walking paths outside the AWRF property line.

METHODOLOGY:
In the summer of 2021 odor sampling was conducted at various source locations throughout the AWRF to characterize the odors onsite coming from untreated sources and assess the treatment of the existing odor control facility. Odor sampling was completed during summer months to obtain samples under worst-case conditions (warm weather, higher anticipated odors). The sampled untreated process sources included the equalization basins, primary clarifiers, aeration basins, solids processing building odor exhaust (untreated odors routed to the high stack), and the incinerator exhaust stack. In addition to the untreated odor sources, sampling was also completed on the chemical scrubber inlet and outlet to assess the system performance. The odor sampling completed included: -US EPA Surface Emission Isolation Flux Chamber -Grab samples collected for olfactory odor analysis by ASTM E679 -Odor speciation using ASTM D194 -Reduced sulfur compounds using USEPA Method TO-15 (GC/FPD detector) -Field measurement of H2S using Acrulogs and Jerome 631X H2S meters -Ammonia, Amines, and Dissolved Sulfide with Colorimetric Detection Tubes -Temperature and pH Sampling data was evaluated and used to characterize the types and concentrations of odor species present at the AWRF, and to determine the odor emission rates from each odor source for use in the dispersion model.

RESULTS:
The results of the sampling showed the solids processing building exhaust to have the highest dilution to threshold (D/T) value, followed by turbulent zones of the primary clarifiers, anoxic stages of the aerobic basins, and quiescent zones of the primary clarifiers. The chemical scrubber exhaust results showed the system to be effectively reducing odors from the treated sources. The speciation sampling resulted in the detection of four odor compounds including hydrogen sulfide, methyl mercaptan, dimethyl sulfide, and dimethyl disulfide. Ammonia was also detected in samples from the solids processing building. D/T results were used to develop the odor emission rates (OERs) for each odor source. OERs were developed by translating sampled values into odor units per second (OU/sec) based on airflow and odor magnitude. The OERS were used as inputs for the baseline emissions model, also known as the AERMOD dispersion model. Meteorological data for the AERMOD dispersion model was sourced directly from the National Oceanic and Atmospheric Administration archives for representative observation sites. The most recent three years of available data (2018â€“2020) were used in this analysis and surface data was obtained from the Quantico Marine Corps Airfield, which is 8 miles south of the AWRF. The resultant impacts calculated by AERMOD are expressed in odor units per cubic meter of air (OU/m3) and can be compared directly to the sampled D/T values. Several scenarios of modeling were completed to evaluate existing conditions, identify the most impactful sources of odor dispersion, and assess potential treatment solution results for the sources. The baseline dispersion model, or existing conditions scenario, showed the predicted impacts from the sampled odor sources on site and their impact outside the AWRF fence line. Figure 1 provides the baseline scenario potential impacts. The worst-case D/T concentrations predicted to reach a given area are shown with the color/label. Based on the baseline scenario, the odor source impacts of the AWRF would be noticeable, and potentially a nuisance, for all areas above 7 D/T (shown in yellow in Figure 1). This includes the communities to the north and east of the AWRF, which have maximum odorous impacts of 7 to 10 D/T. The wide impact of the 3 D/T contour extends beyond the frame of this view, which suggests that the AWRF could potentially contribute to ambient odors greater than 1 mile from the fence line. Individual sources were modeled and showed the solids processing building exhaust and the aerobic basin anoxic zones to have the greatest D/T dispersion impact. Before additional treatment options were evaluated, an odor impact criterion, or D/T fence line goal, was developed with PWCSA during several workshops. Virginia odor criteria are plant-specific, and a survey of Virginia plants showed criteria generally range from 5 to 10 D/T with different averaging time requirements. It was determined that the impact goal should be one that minimizes the risk of negatively impacting neighbors but is balanced with controlling increased cost that will be incurred if goals are excessively tight. For PWCSA, the recommended goal of 100 percent compliance with 7 D/T (1-hour impact goal) at the fence line was used for the evaluation of the model. Once the odor impact criterion was determined, six (6) additional modeling scenarios were developed to evaluate the impacts from treating/reducing odors from the untreated sources. The scenarios were as follow: 1.Treatment of solids processing building exhaust (assumed 90% D/T reduction from solids processing) 2.Coverage and treatment of the primary clarifier odors (assumed 95% D/T reduction from solids processing) 3.Combination of 1 and 2 (treatment of solids processing and primary clarifier odors) 4.Combination of 2 and treating EQ basin odors (assumed 50% D/T reduction from EQ basins) 5.Combination of 2 and covering and treating odors from the aerobic basin anoxic zones (90% reduction of odors from anoxic zones) 6. All control alternatives combined The different modeled scenarios showed the greatest odor reduction results for control scenario 6 (all sources treated), followed by control scenario 3 (primary clarifiers and solids processing building treated). Although control scenario 6 reduced the 7 D/T line impact slightly more than control scenario 3, both scenario results show benefit and bring the 7 D/T line close to the fence line. The model predicted dispersion results from scenario 3 are shown in Figure 2. All six of the scenario results will be shown in the presentation.

DISCUSSION/CONCLUSIONS:
The sampling and modeling results were used to identify the primary clarifiers and solids processing building as additional sources for odor control treatment at the AWRF. Once the sources were determined, a capacity assessment was completed on the existing system which showed it did not have sufficient capacity to treat the additional sources. A complete treatment technology evaluation was completed for the AWRF based on the airflows, odor species present, and required treatment for dispersion. Ultimately, the team decided to move forward with a new centralized chemical scrubber facility re-using the existing vessels and a new vessel to meet the design capacity of 95,000 CFM. Chemical scrubbers were chosen based on the sampling results, odorous airflow capacity requirements, and site space constraints. The presentation will provide insight and potential project path solutions for other utilities looking to evaluate the odor impacts from their treatment facilities on neighboring communities, experiencing odor complaints, or wishing to evaluate dispersion modeling uses.

This paper was presented at the WEF Odors and Air Pollutants Conference, May 16-19, 2023.

SpeakerKenel, Kelsey

Presentation time

8:30:00

9:00:00

Session time

8:30:00

10:00:00

SessionDispersion and Ventilation Modeling

Session number6

Session locationCharlotte Convention Center, Charlotte, North Carolina, USA

TopicAir Dispersion Modeling