Romero, Adrian

Adrian is a wastewater process engineer at Black Veatch in Kansas City, MO. He has a BS in Chemical Engineering and an MS in Environmental Engineering from the University of Kansas. He has over 3 years of experience in the wastewater field, including research on low DO BNR, wastewater-based epidemiology for sars-cov-2, and biological inhibition of heterocyclic organic nitrogen in activated sludge nitrification.

Titles from this speaker

Austin Water Integrated Approach to Odor Control: Sewer to Plant Considerations

Abstract

This paper presents the integrated approach by the City of Austin to address odor concerns in the Greater Walnut Creek Area and its sewershed. The project focused on the identification of the odor sources and their potential impact on the community using dispersion modeling. The project also used sewer process models to comprehend the entire collection system to determine H2S hot spots and to screen sulfide control strategies considering plant impacts. Results showed that the baseline scenario for the Walnut Creek WWTP exceeded the odor threshold set forth. The City is going through an expansion of the Walnut Creek WWTP that incorporates these findings into the design of odor control facilities to mitigate outside impacts. The resulting optimized strategy for the collection system relies on the use of pH adjusters; the WWTP currently uses it in its process thus representing ‘free’ chemical by dosing it upstream for odor control.

This paper was presented at WEFTEC 2023 in Chicago, IL.

SpeakerRomero, Adrien

Presentation time

14:30:00

14:50:00

Session time

13:30:00

15:00:00

SessionManaging the Third Effluent Part II

Session locationRoom S501d - Level 5

TopicCollection Systems, Facility Operations and Maintenance, Intermediate Level, Municipal Wastewater Treatment Design

Author(s)

Romero, Adrian

Author(s)A. Romero 1; K Koeller 2 ; M Berg 1; J. Rife 4; J. Rife 5;

Author affiliation(s)Jacobs 1; Austin Water 2 ; Jacobs 1; Jacobs 4; Jacobs 5;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2023

DOI10.2175/193864718825159225

Volume / Issue

Content sourceWEFTEC

Word count12

Description: Biosolids Master Planning in Tulsa, Oklahoma to Develop a Sustainable Biosolids...

Biosolids Master Planning in Tulsa, Oklahoma to Develop a Sustainable Biosolids Management Program

Abstract

Biosolids Master Planning in Tulsa, Oklahoma to Develop a Sustainable Biosolids Management Program The Regional Metropolitan Utility Authority (RMUA) is responsible for the plant infrastructure as well as the operation and maintenance of the 16 million gallon per day (MGD) capacity Haikey Creek Wastewater Treatment Plant (HCWWTP) in Tulsa, Oklahoma. To evaluate the future needs for treating and handling biosolids generated at the HCWWTP, the RMUA authorized engineering development of a biosolids improvements facility plan and concept level design of needed facility upgrades. For the past 19 years, unstabilized biological sludge from the aeration process has been thickened and then hauled to the Tulsa Southside WWTP for treatment via anaerobic digestion and land application. However, this practice requires hauling of 9-10 tanker trucks a day to the City of Tulsa's Southside WWTP and requires significant coordination between the two plants. The goals of this study were to identify existing conditions, estimate future loadings (up to 24 MGD) , and evaluate cost-effective alternatives to upgrade the HCWWTP to a stand-alone facility, produce biosolids product that could be beneficially used, and define a solution that is not only within the RMUA budget constraints, but defensible (with no regrets) to RMUA and its two partner agencies, the Tulsa Municipal Utility Authority (TMUA) and Broken Arrow Municipal Authority (BAMA). The study provided an opportunity to not only investigate technologies for producing Class B or Class A biosolids for beneficial use, but also to consider adaptability to changing regulations and potential energy savings and reductions in carbon emissions. The following outlines the steps which were used to develop an updated solids management plan and concept level design for RMUA. 1.Existing and Future Conditions - This task included an evaluation of existing solids handling processes at the HCWWTP and the ability of the existing facilities to meet future projected loadings. Estimates of future quantities of solids production were made to determine appropriate sizing of solids management equipment in the near term (next 5 years) and into the future (20 years). This analysis was used to develop appropriate sizing criteria for all solids handling system components such that any deficits in capacity needs and the timing of equipment upgrades to eliminate those deficits were identified for future planning tasks. 2.Evaluation Criteria Development and Identification of Appropriate Technology Solutions -Through a workshop discussion with RMUA staff, the universe of technology alternatives was discussed with the goal of identifying potential biosolids management solutions and appropriate evaluation criteria consistent with RMUA goals and objectives were established. These criteria and potential technology options were defined in a workshop with RMUA stakeholders as well as engineering subject matter experts and the relative importance of these criteria determined. Fifteen biosolids management options as compared to the status quo were then identified in a collaborative process for consideration by the stakeholder team. The evaluation criteria previously developed was then applied against the potential technology solutions aimed at meeting RMUA goals. Figure 1 shows the result of the weighted scoring of these alternatives. At the conclusion of this criteria development and technology options identification, six potentially viable alternatives were selected by RMUA for further evaluation compared to status quo including: - Chemical-Thermal Hydrolysis - Mesophilic Anaerobic Digestion - Composting - Thermal Drying - Mesophilic Anaerobic Digestion plus Thermal Drying - Mesophilic Anaerobic Digestion, Thermal Drying plus Pyrolysis 3.Plant Simulation Evaluations - Existing whole plant simulation models for the HCWWTP were modified to analyze and evaluate the 7 alternatives identified to determine overall impacts on process performance, energy recovery and use of existing assets (tankages and equipment). Outputs of the simulations included overall energy balances, green-house gas emissions, and process performance compared to status quo. The outputs of this modeling exercise were then presented in a workshop with RMUA staff and used to further define the short-listed alternatives for further investigation and refinement. 4.Cost Evaluations - The simulation models formed the basis for conducting capital, O&M and life-cycle cost analysis of the 8 short-listed alternatives identified. Comparative cost evaluations were developed including vendor quotes for large equipment and cost estimating data from previous engineering project experience. Cost estimating tools were then used to compare capital, O&M and life-cycle costs for each alternative. These costs were then considered alongside the non-monetary evaluation criteria identified to develop a cost-benefit analysis. Figures 2&3 show the results of these cost and cost-benefit analyses. An interactive workshop was then held with RMUA stakeholders to fully vet the alternatives and determine three potential technology options for implementation. 5.Site Visits - The RMUA stakeholders then toured three representative technologies in Oklahoma including anaerobic digestion, thermal drying and composting. At the conclusion of the site visits, RMUA stakeholders agreed that while all three technologies could work for them, composting was the best choice due to simplicity of the process and production of a marketable product. 6.Implementation Planning - Implementation of the composting alternative was defined in terms of phasing, scheduling and budget planning to ensure the design and building of composting dewatering and composting facilities with the right capacity will be developed at the right time to meet the City's near-term and long-term needs. Through their engineering partner, City of Tulsa was able to apply for and secure grant funding from the USDA for 20 percent or$ 9.8 million of the total project cost (estimated at $48 million). Project Status One of the most interesting aspects of the project was that based on the previous biosolids management study done in 2014, preconceived solutions of anaerobic digestion and improved dewatering to then land apply biosolids cake was thought to be the solution that would be recommended. However, by revisiting potential solution options and redefining what criteria were most important, several different solutions were reconsidered. Ultimately, site visits conducted by RMUA Staff proved to be extremely helpful in the selection of the composting process that is proven, simple to operate and produces a biosolids product with multiple uses. This selection really paid off when grant funding became available that the compost production process proved to be qualified for, saving the RMUA nearly $10M in costs. This part of the story will be detailed in the paper and presentation. The Haikey Creek Wastewater Treatment Plant Biosolids Improvements Project has been approved and is in the design phase of a 10.2 dry ton per day capacity aerated static pile composting facility expandable to 15.3 dry tons per day in 2060. Major facility components include gravity thickener improvements, sludge storage, new centrifuge dewatering as well as a new covered aerated static pile facility. This case study will present details and results of the entire planning process which will provide planners, engineers, administrators, and owners with insight into the planning process used to select the right solution using specific owner driven criteria as well as costs to choose the right solution for their biosolids management needs.

This paper was presented at the WEF Residuals and Biosolids Conference, June 18-21, 2024.

SpeakerWilliams, Todd

Presentation time

08:30:00

09:00:00

Session time

08:30:00

11:15:00

SessionCase Studies & Lessons Learned

Session number27

Session locationOklahoma City Convention Center, Oklahoma City, Oklahoma

TopicCompost, Master Planning, Residuals

Author(s)

Williams, Todd

Author(s)T. Williams1, A. Romero1, T. Johnson1, L. Ostervold2, M. Vaughan3

Author affiliation(s)Jacobs 1; Jacobs 1; Jacobs 1; Black & Veatch 2; City of Tulsa 3;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Jun 2024

DOI10.2175/193864718825159427

Volume / Issue

Content sourceResiduals and Biosolids Conference

Word count14

Got Options? Louisville's Biosolids Adaptive Planning Case Study

Abstract

Project Description This paper presents an overview of the adaptive planning process to address detrimental and unforeseen changing conditions for managing biosolids. This presenta results and provide a case-study of biosolids technologies, consolidation vs. decentralization of processes, regulatory compliance criteria, resilience and reliability issues, and a cost-benefit analysis of long-term biosolids management strategies. Managing biosolids from multiple treatment plants is a complicated and multi-faceted process requiring forward looking results that are adaptable to handle changing conditions. The process implemented, lessons learned, and results of the Biosolids Study will guide the next steps for implementation of a Regional Biosolids Management Program. Abstract Background The Louisville & Jefferson County Metropolitan Sewer District (MSD) has faced several utility management challenges over the past ten years that have limited their ability to advance new projects. These challenges included regulatory mandates, asset failures, climate impacts, and unplanned regionalization of utility service. MSD's Morris Forman Water Quality Treatment Center (MFWQTC) is the largest in terms of treatment capacity and oldest WQTC in Kentucky. During the early 2000s, MSD added a thermal drying process and began producing Class A biosolids pellets for beneficial use that were marketed and distributed as 'Louisville Green' fertilizer. MSD operates four smaller WQTCs. It quickly became apparent the new planning considerations are difficult to consider linearly. Their impact may change over time; can be minimized with advanced planning; and can be integrated with local priorities. MSD aligned with an integrated adaptive planning roadmap (Figure 1). Although MSD had already evaluated and considered many scenarios for future biosolids improvements with a Critical Repair and Reinvestment Plan (CRRP), the breadth and magnitude of changed circumstances resulted with an urgent desire to reconsider scenarios for future investment. This paper explains how MSD's various planning documents were integrated into a comprehensive Biosolids Study. The study evaluated a series of 'what-if' scenarios for potential future outcomes. Short-listed alternatives were compared and scored using a cost-benefit approach. Objectives The objectives of the Biosolids Study were threefold: (1) construct facilities to enable systemwide cake to be processed through THP-digestion-drying at the MFWQTC by 2027; (2) add capacity to eliminate landfill disposal by 2030 and enable downtime for major refurbishment of dryers by 2032; and (3) add thermal conversation technology to comply with future potential PFAS or microplastic regulations. Methodology Information from previous engineering documents was consolidated. WQTC process models were developed and population projections were applied to predict future flows and loads at each WQTC including potential changes in industrial activity, scoring criteria and weightings were developed, and a shortlist of alternatives was created. Considering the ongoing design-build project of a THP facility at MFWQTC, the project team evaluated technology scenarios, location scenarios, timing/phasing scenarios for seven WQTCs. Example scenarios included: 1) decentralized vs. centralize dewatering; 2) sludge screens; 3) digestion-drying; 4) add drying at the regional WQTCs; and 5) Lystek technology at the regional WQTCs. MSD did not begin a new Master Plan effort with this Biosolids Study. Rather, they built upon the information collected from a variety of events. As conditions related to biosolids changed, MSD determined if a scenario already existed in the CRRP, process model, or other documents. Scenarios were refreshed or developed based upon the living process shown in Figure 2. The project team confirmed the adaptive planning criteria aligned with current system needs and changed conditions (Table 1). Whole-plant process models for each WQTC were calibrated and utilized for development of solids projections and impacts on treatment for each of the alternatives. The facilities included in the Study are presented in to Figure 3. Results and Conclusions A comparison of the non-monetary criteria for all five alternatives is presented in Figure 4. Interestingly, the scenarios tended to vary by future demand; future flexibility; regulatory adaptability, and technology maturity. Capital and O&M costs were developed and reviewed with MSD stakeholders in subsequent workshops for the shortlisted alternatives. Total project life cycle cost were developed and a Benefit Cost Analysis was performed as shown in Figure 5. The estimated capital costs for the alternatives to implement the Third Dryer at the MFWQTC or implement the LystekÂ® process at three regional WQTCs are less than half of the estimated capital costs for the Drying at the DRG. MSD Stakeholders agreed the Third Dryer at the MFWQTC and the LystekÂ® process at three regional WQTCs were viable alternatives and planned to be incorporated into MSD's biosolids strategy for the 20-year planning horizon. Presentation will include: base case and four alternative scenarios; capital, operations and maintenance costs; and overall scoring of scenarios based upon cost and non-monetary factors; MSD's adaptive planning lessons learned; and lastly MSD's next steps for implementing a three phase scope of work outlined in the Study.

This paper was presented at WEFTEC 2025, held September 27-October 1, 2025 in Chicago, Illinois.

Presentation time

14:00:00

14:15:00

Session time

13:30:00

15:00:00

SessionBiosolids Planning from WRF to the WRRF

Session locationMcCormick Place, Chicago, Illinois, USA

TopicBiosolids & Residuals

Author(s)

Romero, Adrian, Burch, Robin, Thewes, Daniel, Pica, Leisha, Williams, Todd

Author(s)A. Romero1, R. Burch2, D. Thewes3, L. Pica3, T. Williams

Author affiliation(s)Black & Veatch1, Louisville & Jefferson County MSD2, Jacobs3

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Sep 2025

DOI10.2175/193864718825160158

Volume / Issue

Content sourceWEFTEC

Word count9

Low-Emission Hybrid Cogeneration for Optimal Energy Resilience

Abstract

Learning Objective
This presentation includes an assessment of the energy recovery system at a water resource recovery facility (WRRF), determining the optimal approaches for resiliency against:
- Increasingly stringent air emissions regulations
- Rising energy costs
- Electrical and gas grid outages
- Availability of adequate heat/power for permit compliance.

The audience should leave with an understanding of the risks and opportunities to the energy supply and production systems at a WRRF, how to mitigate those risks, how to capitalize on current financial and technological opportunities, and considerations for novel heat and power production systems, such as linear generators, fuel cells, and batteries.

Background Encina Wastewater Authority (Encina) serves a population of over 400,000 at the Encina Water Pollution Control Facility (EWPCF), with a capacity of 40.5 million gallons per day (MGD).
Encina commenced the Energy Resiliency Assessment (ERA), to:
1. Develop a combined heat and power (CHP) system to maintain air permit compliance
2. Prevent adverse effects during an outage of utility power
3. Develop a long-term plan for economic CHP replacement

Regulatory Drivers
The primary driver for the ERA was more stringent air quality limits, which, using formaldehyde as a surrogate, necessitated a 90% reduction.

The cogeneration (cogen) engines are the major contributor to these emissions, and therefore must achieve the required reduction. Table 1 presents the emissions design thresholds.

Operational Drivers
A primary goal is to eliminate black starts resulting from increasingly frequent disruptions in power supply from the grid. The ideal approach is onsite CHP production generating 100% of demands, only using the grid as a backup.

Cogen Alternatives
The existing engines must be upgraded or replaced for compliance with the formaldehyde limits. New alternatives considered various combinations of digester gas (DG) use (renewable natural gas (RNG) or fuel), as well as CHP source. Table 2 shows the summary of the new CHP technologies considered. Solid oxide fuel cells (SOFCs) and linear generators (LGs) were the most suitable technologies.

Project Structure and Financing
Significant energy incentives were available on a short timeline, including the Investment Tax Credit (ITC, 30-40% credit). Encina had a better chance of obtaining the ITC, if they implemented third-party owned and operated systems to provide power, and to monetize their DG as RNG.

Due to the uncertainty of pricing and incentives, the optimal way to determine the optimal technology and project structure (Encina owned and operated, third-party owned and operated, DG to fuel, or DG to RNG) was to allow the market to decide via a Request for Proposals (RFP) process.

#Recommended Project
The RFP process yielded 6 proposals, with a range of solutions and costs. The major finding was that the sale of RNG was not feasible as the capital costs were higher than expected, and the differential between natural gas purchase price for power, and RNG sale price, was too small. With no RNG, DG must be used for onsite for CHP, either in the existing engines, or via a new technology, all Encina owned and operated. As the capital costs for a full conversion to a new technology were too high, 3 final alternatives were considered:
1. 100% utility power
2. Existing engines + emissions controls
3. A low-emission hybrid, consisting of a 1 megawatt (MW) of LGs (cheaper than SOFCs) and existing engines + emission controls for the remainder of the power demand. (A 2 MW-hour battery was common to all alternatives)

The hybrid alternative is cheaper, and less risky than full-conversion to a new technology, and as LGs are more efficient than engines (45% compared to 31%), it allows 100% of the DG to supply 100% of the plant power. Table 3 presents the monetary comparison.

Encina selected the Low-Emission Hybrid - it requires the most capital, but has the lowest net present cost, and is eligible for the highest amount of incentives. It allows Encina to utilize 100% of its DG, where the engines would have been limited to 92% of current DG , due to the formaldehyde limit. Encina was able to safe harbor the ITC, and is implementing progressive design-build of the system.

Conclusions
Agencies are faced with increasing challenges to resiliently power their WRRFs. Regulations will become more stringent, power costs will rise, and the grid may become less reliable. WRRFs have an opportunity to be their own source of power, but it is a challenge to meet the diverse CHP needs in a cost and operationally efficient manner. A hybrid system can offer many benefits in transitioning a WRRF to an optimal future CHP system:
- Engines are often existing, reliable, and provide required heat
- Low-emission cogeneration, like linear generators and fuel cells, are more electrically efficient, and emit less pollutants
- Batteries provide instantaneous power supply, manage power quality, and can serve as a power equalization system to shave peaks

These components may be eligible for financial incentives, as communities seek to decarbonize and have a more decentralized, resilient grid. Encina has taken advantage of financial incentives, and will be optimally prepared future regulatory, economic, and operational challenges that may arise.

This paper was presented at WEFTEC 2025, held September 27-October 1, 2025 in Chicago, Illinois.

Presentation time

14:00:00

14:15:00

Session time

13:30:00

15:00:00

SessionMaking the Case for Energy Neutrality

Session locationMcCormick Place, Chicago, Illinois, USA

TopicBiogas & Energy Recovery

Author(s)

Couch, Ted, Parry, David, McClelland, Scott, Romero, Adrian

Author(s)T. Couch1, D. Parry1, S. McClelland2, A. Romero3, , , , , , , , ,

Author affiliation(s)Jacobs1, Encina Wastewater Authority2, Black & Veatch3

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2025

DOI10.2175/193864718825159947

Volume / Issue

Content sourceWEFTEC

Word count8

Description: Potomac Interceptor Long-term Corrosion Prevention Program: DC Water Using...

Potomac Interceptor Long-term Corrosion Prevention Program: DC Water Using Innovative Tools to Support Strategy Development

Abstract

DC Water’s Potomac Interceptor system has suffered from corrosion for many years. According to recent CCTV inspection, approximately 95% of the Potomac Interceptor has shown signs of corrosion. Inputting field data to sewer process models that integrate ventilation resulted in recommendations focusing on the operation of existing forced ventilation odor control systems to support reduction in corrosion. These recommendations have been adopted in the PI operation protocol. In addition, DC Water developed a long-term corrosion prevention program implementing various corrosion mitigation measures identified in the case study.

This manuscript presents a case study of DC Water's Potomac Interceptor (PI) Corrosion Control Strategy using sewer process models with newly integrated ventilation modelling. These models were used to determine the best operational strategy to prevent odor emissions, reduce corrosion, and improve management of the existing forced ventilation facilities. In addition, DC Water developed a corrosion prevention program to implement various corrosion mitigation measures identified in the case study

SpeakerYilma, Eyasu

Presentation time

13:30:00

13:50:00

Session time

13:30:00

15:00:00

SessionManaging the Third Effluent Part II

Session locationRoom S501d - Level 5

TopicCollection Systems, Facility Operations and Maintenance, Intermediate Level, Municipal Wastewater Treatment Design

Author(s)

Yilma, Eyasu

Author(s)E. Yilma 1; A. Satyadev 2 ; A. Romero 3; M. Ward 3; E. Yilma 1;

Author affiliation(s)DC Water 1; DC Water, Washington, DC 2 ; Jacobs 3; The WATS Guys 3; DC Water 1;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2023

DOI10.2175/193864718825159223

Volume / Issue

Content sourceWEFTEC

Word count16

Description: Process Understanding of Full-scale Micro-aeration to Improve Biogas Quality and...

Process Understanding of Full-scale Micro-aeration to Improve Biogas Quality and Anaerobic Digestion

Abstract

High hydrogen sulfide (H2S) concentrations are commonly seen in biogas produced from anaerobic digestion process in municipal water resource recovery facilities (WRRFs). These H2S concentrations cause the corrosion of concrete and steel, increases biogas conditioning costs, compromises the functions of cogeneration units, and leads to sulfur dioxide emissions. In addition, elevated dissolved sulfide levels in the sludge can inhibit the overall digestion process. Traditional methods of removing the sulfide have relied on chemical dosing into the digesters or biogas scrubbing, both increasing the costs of biogas utilization, often maintenance intensive and can present relatively high environmental impacts. This may lead to other issues including unnecessary adverse odours and less efficient operation of power generating assets. Biotechnologies (i.e. aerobic or anoxic biotrickling filtration) have recently emerged as cost-effective and more environmentally friendly alternatives (Munoz et al. 2015). Nevertheless, these biotechnologies are still limited by their high investment costs and their generated byproducts such as sulfuric acid and/or elemental sulfur slurry that need further processing or disposal (Kraakman et al. 2019). This paper explores the full-scale implementation of a relatively new process called 'micro-aeration' (MA). MA is a process integrated technology that employs a very small amount of air introduced into the anaerobic digester to raise the redox potential to partly oxidize the sulfides to elemental sulfur and remove it from the digester together with the digested sludge. Traditionally, exposure of the anaerobic digestion process to oxygen has been avoided due to its perceived negative effects on growth and activity of obligate anaerobes, especially methanogens. However, in recent years numerous studies have reported the potential beneficial effects on anaerobic digestion in terms of digestion process stability and digested sludge dewaterability when a small volume of air or oxygen is injected into the sludge (Jenicek et al., 2014). The MA process has been shown to reduce H2S in the biogas and sulfides in the waste stream by more than 90% (Ngheim et al., 2014, Jenicek et al., 2017). For this reason, MA has the potential to revolutionise sulfide removal in anaerobic digestion. However, the basic mechanisms involved in micro-aerobic sulfide oxidation are not fully understood and control strategies for MA are still being optimised. Complex biological and chemical interactions occur between sulfur, oxygen, iron, and phosphorus throughout the anaerobic digestion processes, which are well characterized in literature (Batstone, 2006). Despite recent developments in whole plant process simulators (Hauduc et al., 2017), and modifications to the anaerobic digestion model (ADM) (Flores-Alsina et al., 2016), the implications of these interactions, including within the MA context, have not been fully explored. This paper presents an increased understanding of the MA process by specifically reviewing the performance of a full-scale MA application by Sydney Water and by proposing a process model capable of representing the performance observed at full-scale MA and considers biological and chemical interactions. A review of other full-scale MA applications is also presented. METHODOLOGY This investigation comprised the following steps: Literature review of the existing MA process configurations and performance. Including recently reported full-scale pilot testing (Kraakman et al, 2019). Critical review of over three years of process data for a Sydney Water installation including MA conditions, solids and biogas balances and analysis of the sulfur balance around the digestion treatment process. Development of a process model for an existing installation using the SUMO platform with integrated sulfur chemistry. This involved developing an anaerobic digester process unit with capabilities to set up aeration conditions and calculate oxygen transfer for uptake by digester biomass and use in oxidative processes such as sulfide oxidation by Sulfur Oxidizing Organisms (SOOs). Figure 1 shows the Sumo process schematic of the modelled installation. RESULTS Analysis of the process data on the MA trials showed that normal H2S concentrations in the biogas of approx. 1,000 ppmv can be reduced by up to 92%. However, there is a clear trend when studying air flow rates and H2S removals where a normal removal of around 50% was achieved at air flows of 177 NL/m3 reactor volume-day or higher, with a maximum observed oxygen consumption of 6.65%/m. Moreover, increasing the oxygen to sulfide ratio did not necessarily increase H2S removal. Results for biogas H2S removal and impacts on methane content due to the dilution mostly by the nitrogen in the MA air injected are summarized in Table 1. These sulfide removals translate in an increased biogas quality for energy recovery in WRRFs with potential to lower costs of biogas conditioning. In terms of digestion performance, no statistical differences were observed in total solids reduction, biogas production and cake solids achieved when the MA was performed compared. General process model calibration was performed following the International Water Association's Good Modeling Practices Unified Protocol and the SUMO Process Simulator (Dynamita, Lyon, France). Calibration of the sulfur chemistry in the raw sludge and the digesters without MA was first achieved by estimating the particulate fraction in the influent sulfur speciation, and by considering the collection system operation in terms of iron addition, discharge of biological sludge from a neighboring treatment plant, and internal sulfur recirculation from a chemical scrubber targeting H2S. To calibrate the process model, model parameters needed to be adjusted to match the observations from the MA trials. Most critical seems the affinity constants and its related rate of sulfide oxidation in the model compared to default microbial and chemical kinetic parameters when applied to full scale digestor systems. Two sulfide oxidation pathways are identified for oxidation of H2S, one mediated by SOOs and another chemically mediated in the presence of a metal. From literature in the subject, it is still unclear which pathway would dominate, and simulations using the developed model in this project showed that both mechanisms have the potential to yield the oxidation rates needed to match results obtained. Given the research conducted by Van der Zee et. al. (2007), Jensen et. al (2009), and Ruan et. al. (2017), the MA model currently considers the biological oxidation as the most significant mechanisms for sulfide reduction during air injection. A better understanding of the residual iron-ion levels in the digester feed sludge and actual mass of the different sulfur species will be useful to refine the model. CONCLUSION This investigation presented a process model for a better understanding of the sulfur chemistry during the digestion process, with biological oxidation likely to be the most significant mechanisms for sulfide removal during the MA process. MA is a promising technology for sulfide control in anaerobic digesters; this investigation showed that up to 92% H2S removal can be achieved, although the performance to date has been variable for various reasons. Lower H2S level in the biogas decreases biogas treatment cost for energy recovery thus contributing to the economical and sustainable performance of the energy recovery process of waste sludge digestion at wastewater treatment facilities.

The following conference paper was presented at Residuals and Biosolids 2021: A Virtual Event, May 11-13, 2021.

SpeakerRomero, Adrian

Presentation time

11:45:00

12:00:00

Session time

11:00:00

12:15:00

SessionOptimizing Digestion and Co-Digestion

Session number3

Session locationSimu-Live

TopicAnaerobic Digestion, Biogas desulfurization, Energy recovery

Author(s)

A. RomeroJ. CescaD. Van RysB. JohnsonB. Kraakman

Author(s)A. Romero1; J. Cesca2; D. Van Rys3; B. Johnson4; B. Kraakman5

Author affiliation(s)Jacobs 1; CH2M/ Jacobs 2; Jacobs 4; CH2M 5;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2021

DOI10.2175/193864718825157951

Volume / Issue

Content sourceResiduals and Biosolids Conference

Word count13

Sulfide control optimization using sewer process models

Abstract

INTRODUCTION
The Albuquerque Bernalillo County Water Utility Authority (Water Authority) owns and maintains over 2,000 miles of pipes in the collection system to convey approximately 50 MGD wastewater from the service area to the Southside Water Reclamation Plant (SWRP). The Water Authority has implemented a range of methods and technologies for controlling odors and corrosion in the collection system, resulting in significant institutional knowledge and experience of this branch of engineering science. Nevertheless, the sewer network still faces corrosion challenges due to sulfide generation with numerous pipes that are at risk of collapse. Comprehensive analysis of a complex collection system to allow for the optimization of sulfide control relies on the understanding and quantification of the processes impacting sulfide production and release (Revilla et al, 2016). To facilitate this intricated task, properly implemented sewer process models become a valuable tool. This implementation could also support the evaluation of the impacts of the sulfide control strategy on the SWRP process performance. The objective of this project was to marshal and organize the resource expenditure on odor and corrosion control so that it is optimized, coordinated across the collection system, and harmonized with the pipe rehabilitation program and the identified operational constrains of the SWRP. A novel approach using sewer process model (the WATS model) was implemented to develop a comprehensive sulfide control strategy, and to empower the Water Utility with a tool to support the migration from a reactive to a proactive approach on asset management while being able to communicate to SWRP staff the potential impacts in the treatment process.

METHODOLOGY
The study area for the Water Authority collection system included approximately 250 miles of pipe with a minimum diameter of 15 inch in four main interceptors (plus tributaries). A sewer process model was used to apprehend the study area as a whole and analyze physical, biological and chemical processes bearing on odor and sulfide corrosion. Data Collection. The Water Authority collected data on several parameters as part of the regular monitoring program for the collection system in 17 locations and the influent to the WWTP. These included grabs samples for wastewater temperature, pH, total and dissolved sulfide, total iron and continuous monitoring of headspace hydrogen sulfide. Additional monitoring at each of the most downstream location in the four interceptors was performed. Sewer Process Modelling. The WATS model (Hvitved-Jacobsen et al, 2013) was selected as the most appropriate software tool for this purpose. WATS is currently the most rigorous and complete sewer process model in the world and is well suited to assessing the Water Authority sewerage. The model was set up using the existing hydraulic model of the system and considering the operation of the collection system at the time of the selected calibration period in terms of flow diversions and chemical addition. Considerations for the optimization strategy in the collection system were in place to prevent negative impacts in the SWRP: 1) a minimum pH of 7 in the plant influent needed to meet the permitted effluent pH; 2) a maximum magnesium concentration in the influent to prevent formation of nuisance struvite (impacts use of magnesium hydroxide); 3) a limit in the use of solids produced in the potable water treatment plant that have the potential to be used for sulfide control if discharged to the collection system.

RESULTS AND DISCUSSION
Model Calibration The WATS model for the Water Authority collection system was calibrated to dissolved sulfide and headspace hydrogen sulfide in the 17 monitoring locations throughout the four interceptors. In addition, diurnal pH data was available to refine model calibration. Data for winter and summer were available and seasonal models were developed to allow for a more detailed strategy for optimizing sulfide control. Stochastic simulations (n=100) were run and the results compared to the complete data set for the calibration period. Figure 2 shows measurement-model agreement for station 10. Alternatives analysis for sulfide control optimization The calibrated WATS model allowed for the screening of a wide range of alternatives, including chemical dosing at various dose rates using different chemicals at various locations, and assisted in the prioritization of pipe rehabilitation given the relative cost of on-going chemical treatment versus rehabilitation. The screening resulted in novel and the most cost-effective strategies with potential to be implemented in each of the four major interceptors. Some of this approaches include: Addition of iron-rich water treatment plant solids. The San Juan Chama Water Treatment Plant can discharge residual sludge containing high levels of iron for sulfide control in the collection system. Bench-scale testing provided the input to the WATS model in terms of sulfide removal efficiency. It was determined that the amount of solids the SJCWTP was limited to discharge to prevent negative impacts at the SWRP was enough to provide comprehensive treatment for the Edith Interceptor and partial treatment at the Valley Interceptor. Comprehensive treatment at the Valley Interceptor was achieved by dosing Iron for the upstream end and by applying PRI-SC to reach sulfide control at the downstream end of it, providing the most cost effective approach. Iron addition with pH adjustment and Peroxide Regenerated Iron for Sulfide Control (PRI-SC). An evaluation was performed using the WATS model combining chemical dosing for a synergistic and cost-effective interaction between Mg(OH)2, ferric and PRISC. As shown in Figure 2, the Westside Interceptor relies on iron addition in the upstream end of the system with pH adjustment using Mg(OH)2, recognizing that sulfide precipitation rate increases as pH approaches 8 units (Hvitved-Jacobsen et al, 2013). This treatment targeted Station 64 where the PRISC process allowed for a more cost-effective solution to achieve comprehensive treatment to the nearest pump station. In addition to considering the limitations set by the SWRP influent characteristics to protect plant operation, a qualitative assessment of the impacts of the optimized strategy on the performance of the SWRP resulted in potential benefits to sulfide control in the solids train; SWRP better prepared for potential stricter phosphorus limits; and) an increase in soluble substrate for enhanced BNR. The optimization routine using WATS resulted in chemical selection and dosing maximizing existing infrastructure while maintaining wastewater characteristics in the SWRP influent within the constrains identified by plant operations.

CONCLUSION
The careful implementation of the WATS process model to the Water Authority collection system allowed for the understanding of the processes bearing in sulfide production and release, and for the screening and identification of alternatives for controlling sulfide in the system as a whole and in an optimized manner. The results confirmed that the presented methodology allows for the incorporation of modelling tools in the decision making for management of collection systems.

The following conference paper was presented at Odors and Air Pollutants 2021: A Virtual Event, April 20-22, 2021.

SpeakerRomero, Adrian

Presentation time

13:40:00

14:00:00

Session time

13:00:00

14:30:00

SessionManaging the Unseen Underground Crisis

Session number2

Session locationLive

TopicChemical Treatment, Modeling, Sulfide Corrosion

Author(s)

Adrian RomeroMatthew WardJes VollertsenMark Holstad

Author(s)Adrian Romero1; Matthew Ward2; Jes Vollertsen3; Mark Holstad4;

Author affiliation(s)Jacobs1; The WATS Guys2; Aalborg University3; City of Albuquerque4

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Apr 2021

DOI10.2175/193864718825157927

Volume / Issue

Content sourceOdors and Air Pollutants Conference

Word count8

Transforming THP biosolids cake using a new biodrying process

Abstract

Utilization of the Thermal Hydrolysis Process (THP) to treat sludge before anaerobic digestion has been practiced since 1995. There are many benefits to this process including improved digestion performance, the ability to feed digesters at a higher solids concentration thereby reducing needed digestion volume by 50% or more, a reduction in the quantity of solids remaining after digestion, improved dewatering, and production of a low odor Class A exceptional quality (EQ) biosolids cake product (Barber, 2020). There are now more than 70 full scale THP plants operating worldwide with at least 20 more in construction or design that utilize this process.

One of the challenges that remains regarding implementation of the process is that even though a low odor Class A EQ biosolids is produced, the dewatered cake at 30% solids still looks like Class B biosolids cake and must be land applied on agricultural farmland, usually at a significant distance from the plant. Work has been done using simple windrowing to air dry thermally hydrolyzed biosolids cake to approximately 55-60% solids to produce a more soil-like material (Brower et.al., 2018). The air-dried biosolids product can then be more readily used in landscape and horticulture applications. However, the windrow air drying process can take 3-6 weeks or longer, requires a significant amount of covered land area, regular turning of the windrows to achieve the necessary level of drying, and includes risk of odor concerns due to the large area and frequent pile turning.

A simplified intensification process has been developed called Dune that takes advantage of the natural biological process to generate heat and to achieve drying of THP dewatered cake to 55-60% solids in less than 2 weeks (Figures 1 and 2). This process requires only a fraction of the space (approximately one third) required by windrow air drying while significantly reducing ammonia and odor emissions. The Dune process has been successfully demonstrated at field scale at two THP solids processing facilities: one in the US and one in the UK (Figures 3 and 4). A third field scale demonstration is in progress with the results being available before the transcript is due. The process uses a portion of previously biologically dried THP cake blended with fresh wet THP cake to produce a mixture that has adequate porosity and bulk density to allow for forced ventilation in an aerated static pile configuration.

Results of these field scale trials prove that sufficient energy remains within the dewatered THP cake to continue biological degradation with naturally occurring aerobic microorganisms present within the recycled dried THP cake. No external amendments are required. A major by-product of this continued biological degradation process is heat. By providing aeration to maintain aerobic conditions within the mass of the mixed materials, temperatures rapidly rise, and moisture is removed. The result is that the tonnage of the solids can be reduced by 50% which in turn will reduce costs of hauling and land application by 50% or more. In addition, the characteristics of the dried product are like a well stabilized compost or soil that can be utilized in horticultural applications such as landscaping, turf, and ornamental gardens instead of only agricultural farmland (Table 1). The product pH transitioned from slightly basic to just below neutral, the carbon dioxide respiration rate significantly reduced indicating more stability, and a slight decrease in volatile solids occurred showing further volatile solids reduction. These changes in the biosolids characteristics while maintaining Class A biosolids status allows for multiple products uses instead of only in agriculture, thus opening different product markets. Another benefit of the process is that by changing the conditions of the biosolids from anaerobic to aerobic, methane emissions from the stockpile of material are almost immediately stopped. Emissions testing of the process demonstrated a drastic reduction in methane emissions (Figure 5) and potential GHG reductions when compared to conventional storage of dewatered THP cake prior to land application.

The authors are performing a third field scale demonstration at another full scale THP facility in the first quarter of 2025. The testing results of that demonstration will be also reported in the final manuscript and presented at the conference. This presentation will provide a description of the Dune process and discuss results of the field scale demonstrations including the impact on product quality, product quantity, and methane emissions as compared to the conventional method of storing THP biosolids cake. O&M cost comparisons will also be provided showing the cost-benefit of full-scale application of the Dune drying intensification process to Class A THP cake compared to windrow drying or storage of cake without drying.

This paper was presented at WEFTEC 2025, held September 27-October 1, 2025 in Chicago, Illinois.

Presentation time

09:00:00

09:15:00

Session time

08:30:00

10:00:00

SessionInnovative THP Startup and Biosolids Finishing

Session locationMcCormick Place, Chicago, Illinois, USA

TopicBiosolids & Residuals

Author(s)

Williams, Todd, Alexander, Zac, Romero, Adrian, Multra, Melody, Funk, JuliaAnn, Le, Tri, Fotouhi, James

Author(s)T. Williams1, Z. Alexander1, A. Romero1, M. Multra1, J. Funk1, T. Le1, J. Fotouhi2, , , , , ,

Author affiliation(s)Jacobs1, DC Water & Sewer Authority2

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Sep 2025

DOI10.2175/193864718825159945

Volume / Issue

Content sourceWEFTEC

Word count10

Description: Trends in Improved Assessment and Implementation of Odor and Corrosion Control...

Trends in Improved Assessment and Implementation of Odor and Corrosion Control Strategies in Wastewater Collection Systems

Abstract

INTRODUCTION
Urban wastewater has historically been managed by separately optimizing the collection system (CS) and the treatment facilities. CS have been optimized through platforms that primarily focus on conveyance capacity defined by wet weather flow conditions. However, during dry weather conditions, the system becomes a bioreactor changing the characteristics of the wastewater and the environment within the pipe, often leading to sulfide production causing odors and costly corrosion problems. Considering that these are common and costly problems for utilities, there is a need for the development of cost-effective strategies to address them, and as an alternative to current trial-and-error practice and expensive sampling and piloting projects. The paper shares insights gained through the development and implementation of innovative tools that simulate biological, chemical and physical processes in CS including sewer ventilation. This understanding is key to effectively solving sewer odor and corrosion and determining wastewater transformations. Large and complex CS have been evaluated using sewer process models with the goal of solving odor and corrosion problems and related management strategies including: - Establishing risk profiles along wastewater conveyance - Developing management strategies for multiple zones of the systems while determining upstream and downstream impacts - Prioritizing areas for mitigation based on estimated pipe life and likelihood of odor complaints - Quantifying wastewater characteristics for wastewater treatment plant influent to determine potential impacts on performance. METHODS
Three case studies where sewer process modeling was used were selected for this paper. Further details of each project and a summary of the outcomes are presented in the Results and Discussion section.
Sewer Process Modeling
The projects utilized the Mega-WATS simulator to evaluate the CS, which is based on the WATS model (Hvitved-Jacobsen et al, 2013) targeting sewer biological, chemical, and physical processes within CS. This includes transformation of organic matter and sulfurous compounds under aerobic, anoxic, and anaerobic conditions. Mega-WATS represents a unique tool to estimate sulfide production for the potential for odors and corrosion. Changes in key plant influent characteristics can be estimated given changes in CS operation such as changes in flow rates, storage and chemical addition. With appropriate physical inputs and field data (e.g. COD, pH, hydrogen sulfide -H2S) the Mega-WATS models presented in this abstract were calibrated and used to simulate odor and corrosion problems and related management strategies.
RESULTS AND DISCUSSION
Albuquerque-Bernalillo County Utility Water Authority (Water Authority) The Water Authority has implemented a range of methods and technologies for controlling odors and corrosion in the CS that conveys 50MGD. Nevertheless, the sewer network still faces corrosion challenges with numerous pipes that are at risk of collapse. This study aimed to optimize odor and corrosion control efforts across the entire CS, in conjunction with and considering the pipe rehabilitation program and the identified operational constrains of the downstream plant (SWRP). The Mega-WATS model included approximately 250 miles of pipes. Model calibration used 16 sampling locations; an example of calibration results for hydrogen sulfide using stochastic simulations is presented in Figure1. An existing plant process model provided the considerations for the influent at the SWRP: 1)a minimum pH of 7 to meet the permitted effluent pH; 2)a maximum magnesium concentration to prevent formation of nuisance struvite, thus limiting the use of magnesium hydroxide for pH adjustment; 3)limit inert suspended solids concentration to avoid impacting the biological process. Iron-rich solids produced in the potable water treatment plant were considered for free sulfide control. Figure2 shows the distribution and type of chemical dosing and Table1 shows the proposed optimized chemical dosing rates and the expected savings, which are substantial. Milwaukee Metropolitan Sewerage District (District) The District has had a history of odor and corrosion issues, caused mostly by H2S in its collection system. The District's CS serves 28 communities with 1.1 million people and covers 423 square miles. Wastewater is transported to the Jones Island and South Shore WRFs. Physical sewer data were extracted from the District's hydraulic model to build the entire sewer network in Mega-WATS (295 miles of pipes between 8 and 150 inches). The project used a stepwise approach to determine the areas in the system that required attention and developed recommendations on the best solutions: 1. Field sampling was conducted to facilitate model calibration. 2. Using the calibrated model and historical odor complaints, 15 zones were identified for further evaluation of odor and corrosion issues. 3. A second sampling was conducted in ten zones where Mega-WATS modeling indicated the potential for odors and corrosion. The results led to the identification of eight priority zones to evaluate. Figure3 shows these areas. All zones were located at drops or near siphons. 4. Conceptual designs using liquid- and vapor-phase mitigation were completed using results from the model. 5. Cost and non-monetary factors were used to select the recommended alternatives (Table2). Oakland and Macomb County (OMID) The OMID wastewater CS has experienced corrosion and degradation in some sewer reaches due to microbial induced corrosion. Combined, the population of the two counties is more than 2 million people with a land area of more than 1,400 square miles. The counties CS includes sewers with depths up to more than 100 feet and diameters up to 11 feet. The H2S generated in the interceptor system is significant because of long detention times and large turbulent drop structures. In addition, the CS is used to store wastewater which results in anaerobic conditions and high sulfide generation. To provide a robust evaluation and selection of the best approach for mitigating odor and corrosion, the project included field sampling, Mega-WATS modeling and fan testing. Outcomes from this project included: - The identification of potential corrosion impacts (concrete loss) due to different flow regimes (Figure4) showing where a reduction in flow would increase corrosion rates. - Determination of chemical dosing (Figure5) and air flow rates for comparing mitigation alternatives and provide recommendations. - Air dispersion modeling was conducted to determine the levels of odor control required to mitigate odors and reduce complaints. - Recommendations led to an integrated approach with multiple zones for vapor-phase treatment and chemical dosing (Figure6). - Modeling of potential corrosion impacts due to different operating schemes including wastewater storage and release (Figure7) to estimate the increase in concrete loss per event (Figure8) due to increased sulfide production.
CONCLUSIONS New modeling approaches and simulation platforms such as Mega-WATS allows for the integration of wastewater collection and treatment systems. While process modelling of collection systems allows for proper asset management (corrosion prediction) and odor mitigation strategies of a wide range of system characteristics, as shown in the diversity of the case studies, it also indicates transformations in the wastewater characteristics that may impact treatment facilities.

This paper focuses on the development and implementation of the latest innovations in tools that simulate collection system sewer biological, chemical and physical processes, the understanding of which is key to solving sewer odor and corrosion problems. Complex sewer networks have been studied using the Mega-WATS model with the goal of assessing in-sewer problems and related management strategies. Three diverse case studies are presented.

SpeakerRomero, Adrian

Presentation time

14:00:00

14:25:00

Session time

13:30:00

15:00:00

TopicIntermediate Level, Collection Systems, Facility Operations and Maintenance, Intelligent Water, Odors and Air Quality

Author(s)

Romero, Adrian

Author(s)Adrian Romero1; Mark S. Holstad2; Matthew Ward3; Jes Vollertsen3; Micki Klappa-Sullivan4; Sid Lockhart5; John S. Siczka1; Bill Desing1

Author affiliation(s)Jacobs Engineering1; Albuquerque Bernalillo County Water Utility Authority, Albuquerque, NM2; The WATS Guys, Winston-Salem, NC3; Milwaukee Metropolitan Sewerage District, Milwaukee, WI4; Oakland-Macomb Interceptor Drain Drainage District5

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2022

DOI10.2175/193864718825158640

Volume / Issue

Content sourceWEFTEC

Word count17