109 - 120 of 21651 titles
Description: Eliminating PFAS - Bioforcetech Technology Shows Promise through EPA Testing
Abstract
Since it was founded in 2013, Bioforcetech has been working to rethink biosolids treatment at every step of the process. Our work has culminated in a deeply sustainable system that harnesses the energy already available in biosolids to dry and carbonize it with little to no external energy. Our patented Bioforcetech BioDryer (designed in house) and P-Series Pyrolysis machines (licensed and engineered in partnership with Pyreg GmbH) work together to reduce material volume and weight by 90%, lock available carbon in place for centuries, and produce a valuable biochar material all with 99% less external energy requirement than a standard paddle dryer. The Bioforcetech system is modular, capable of handling 80% of all US plants by linking units together in series, so that a plant can begin processing now with room to build as their capacity grows. At present time, we are proudly the only commercially available functioning pyrolysis project in the USA, and are running our units under some of the most stringent permitting conditions in the world (We have received an SSI exemption from the EPA and have received full permitting from BAAQMD). At Bioforcetech, we know that change is possible through collaboration across sectors and industries, which is why we are also investing in finding new applications for biochar that will lighten the carbon footprint of other industries and help grow the market for the material across the world. Our wastewater treatment is of utmost importance to human health. The accumulation of PFAS, PFOA, and PFOS in wastewater effluents puts our industry in a unique position to aid in the removal of these substances from our population.At Bioforcetech we have taken the PFAS issue as a personal challenge to overcome, and we are now proud to share that testing conducted on our technology shows considerable promise for its ability to successfully eliminate these harmful substances from input materials completely. When continuously applied, these CEC's bioaccumulate into the soils we walk on, the groundwater we drink, and the plants that we eat. As described by the EPA, high accumulations of PFOA, PFAS and PFOS can cause serious health effects including increased cholesterol levels, issues with infant birth weights, adverse effects on the immune system, cancer (for PFOA) and thyroid hormone effects (for PFOS). While the production of these chemicals has been phased out in the United States, similar chemicals like GenX have taken their place and continue to be created. The presence of PFAS, PFOA and PFOS in biosolids makes even the most beneficial land application of the material a serious risk to human and environmental health. In September 2019, we at Bioforcetech initiated testing of our drying and pyrolysis process to determine our ability to eliminate CEC's from biosolids. To do this, Bioforcetech isolated a single large batch of biosolids and tested samples of this batch for PFAS, PFOA, and PFOS at each step of our drying and pyrolysis process. An initial sample was taken of anaerobically digested biosolids at 17% solids content, a second sample was taken of 91% solids content biosolids after the batch was dried in our patented Biodryer, and a third sample was taken after the batch was put through our P Five pyrolysis machine. The analysis of these three samples conducted by Vista Analytical Laboratory showed the reduction of 38 PFAS, PFOA, and PFOS compounds to below detectable levels after pyrolysis from a significant presence in both of the biosolids samples. In May of 2020, an EPA PFAS Task Force representative contacted Bioforcetech as part of a search for technology that could solve the PFAS issue. We were happy to work with the EPA to further test our technology, and found the results promising again. The tests conducted on our biochar samples by the EPA Task Force in August of 2020 confirmed undetectable levels of 41 PFAS, PFOA, and PFOS compounds that the task force tested. The results from the EPA's analysis including methods involved will be formally published in November of 2021. The results of multiple tests conducted and confirmed by different constituents shows great promise for the ability of Bioforcetech's system to remove PFAS, PFOA, and PFOS from biosolids completely. While more rigorous testing must be completed, we are motivated and inspired by the results thus far. PFAS, PFOA, and PFOS have permeated every part of our planet. Wastewater effluents provide a unique context where these chemicals can bottleneck together and appear at relatively high volume. It is therefore our responsibility as an industry to leverage this context and destroy PFAS, PFOA, and PFOS before it accumulates further in our soil, food and within our bodies. Solving this challenge is crucial to completing the Bioforcetech mission; to protect nature and human health by providing technologies that deliver a zero waste future, transforming organic waste into sustainable products. We are looking forward to continuing this work.
This paper was presented at the WEF Residuals and Biosolids Conference in Columbus, Ohio, May 24-27, 2022.
Presentation time
15:45:00
16:15:00
Session time
13:30:00
17:00:00
Session number03
Session locationGreater Columbus Convention Center, Columbus, Ohio
Author(s)
Author(s)V. Villa1; E. Bridges2; G. Benisch3
Author affiliation(s)Bioforcetech Corporation; 1Bioforcetech Corporation; 2Bioforcetech; 3
SourceProceedings of the Water Environment Federation
Document typeConference Paper
Print publication date May 2022
DOI10.2175/193864718825158442
Volume / Issue
Content sourceResiduals and Biosolids
Word count11
Description: Future of Water and Wastewater Infrastructure and Policy in Sugar Land: A Story of...
Abstract
Investing in future water and wastewater infrastructure is one of the major decisions a City has to make. In May 2019, the Texas State Legislature passed House Bill 347 which severely limited cities' annexation authority by requiring landowner or voter approval for most annexations. With the limited ability to annex, cities must consider if they are willing to invest in infrastructure that is not within the City limits with the possibility that the area will never be annexed into the City. The City of Sugar Land, TX is in a position where it is approaching buildout with remaining growth opportunities consisting of limited redevelopment within the City limits and new development in the extraterritorial jurisdiction (ETJ). When the City began updating their water and wastewater master plans in 2019, the major focus was to address their concerns about the extension of utilities into the ETJ and the impact on City growth in the future. Sugar Land completed the master plan update process in 2021 and has insights to share with other cities. Since the completion of the master plan, Senate Bill 2038 allowed residents of an area to petition or have an election, depending to the population, to leave the ETJ. This presentation will provide implications of this new legislation on the planning process. Background The City of Sugar Land is the largest city in Fort Bend County, Texas with approximately 120,000 people and is located about 20 miles southwest of downtown Houston. In the past, growth primarily occurred though the creation and annexation of Municipal Utility Districts (MUDs). Currently, most the remaining ETJ areas are not large enough to be likely candidates for MUD development. As a result, the City is exploring alternative solutions to infrastructure development in the ETJ. Finding a solution to this unique set of circumstances required an innovative, collaborative approach utilizing the expertise of the City's planner and engineers. Through this innovative planning process, the project team was able to address the immediate concerns regarding the extension of utilities to individual properties in the ETJ, update City codes, ordinances, and policies to align with the council direction, and establish recommendations to address capital investments in water and wastewater infrastructure. The master plans update study had the following three objectives that were interrelated and dependent upon one another: 1.Conduct an assessment of Sugar Land's existing codes, ordinances, and policies; benchmark the existing policies against other cities; and provide recommendations for a policy to address the extension of utilities in the ETJ; 2.Develop water and wastewater master plan recommendations to plan for infrastructure growth in the City and ETJ; and 3.Combine these two separate tasks into a singular tool that could serve the planning and public works departments and outline a plan for implementation. Unique aspects of this study are listed below. The presentation will expand on each of these items and give the conference attendee insight on how Sugar Land approached their future capital project and policy questions. Non-traditional Master Plans In a traditional master plan, collaboration with City staff occurs during a small handful of workshops. In this study, planners and engineers from Sugar Land and Freese and Nichols met to collaborate, brainstorm, and work through the innovative policy and infrastructure planning process continually for about 2 years over a series on biweekly phone calls. These calls facilitated discussions that forced both planners and engineers to think outside the box and consider how the policies and master plans can, and should, work together to effectively plan for future water and wastewater infrastructure given the annexation challenges faced by the City. Involving City Leadership in the Planning Process Due to the significant financial investment required to provide regional water and wastewater service, the City needed to decide whether they wanted to be the regional provider of water and wastewater to the ETJ. During the process, presentations were made to City management to educate them as to how growth had historically occurred in Sugar Land, why the previous utility policies were no longer applicable, and what appropriate options to consider. Once the City management staff were looped in, City Council was asked to make the policy decision mid-way through the project such that the master plan and policy recommendations could be aligned with the City's direction. Action Oriented Work Plan Instead of a traditional Capital Improvements Plan (CIP), this master plan culminated in an action-oriented work plan. The work plan included recommended policy updates and future modeling/rehab/financial studies to develop specific water and wastewater infrastructure recommendations for the ETJ. Each work plan task included an easy-to-reference summary with associated information such as how the recommendation aligned with City goals, leading and partnering departments, scope of future studies, desired outcomes, staff action items, and recommended timeframe for implementation. A Document for All The study was delivered in a new and innovative reporting format unlike any prior master plans this team had worked on. Along with a traditional report, executive summaries were developed in a magazine-style format utilizing InDesign software. These executive summaries captured the highlights and recommendations of the study in an easy to understand, graphic heavy format, which caters to both technical and non-technical readers. While these executive summaries are designed to be go-to documents for the City staff, council members as well as public citizens can also easily access and understand the master plans, increasing transparency with the public. Takeaways Sugar Land approached the question they were facing with a non-traditional master plan that incorporated policy recommendations regarding the extension of water and wastewater service into the ETJ in response to changing legislative action. Utility managers, planners, engineers, public works staff, and consulting engineers of all experience levels will walk away from this presentation with unique perspective about a question most cities and utilities are currently facing or will be facing in future.
This paper was presented at the WEF/AWWA Utility Management Conference, February 13-16, 2024.
Presentation time
11:00:00
11:30:00
Session time
10:30:00
12:00:00
SessionStrategic Planning A
Session number03
Session locationOregon Convention Center, Portland, Oregon
Author(s)I. Rahman1, A. Garcia1, K. Ryan1, K. Clayton2
Author affiliation(s)Freese and Nichols 1; City of Sugar Land 2;
SourceProceedings of the Water Environment Federation
Document typeConference Paper
Print publication date Feb 2024
DOI10.2175/193864718825159325
Volume / Issue
Content sourceUtility Management Conference
Word count20
Description: Developing a Utility Strategic Plan Integrating Sustainability, Innovation and...
Abstract
The Metropolitan Water Reclamation District of Greater Chicago (MWRD) is a special-purpose district responsible for treating wastewater and providing stormwater management for residents and businesses in its 882-square-mile service area, which encompasses Chicago and 128 suburban communities throughout Cook County. The MWRD works diligently to protect Lake Michigan, the source of their drinking water, and to ensure the health and safety of residents and area waterways. In 2020, the MWRD embarked upon a strategic planning process to establish the vision and goals that would guide its work over the next five years. The MWRD engaged Arup and Civic Consulting Alliance to conduct the strategic planning process in collaboration with its Board of Commissioners and Executive Team. We brought expertise on structuring comprehensive stakeholder engagement for water utilities along with experience working with institutions to embed an equity-focus across their work — two strategic priorities for the MWRD in this round of planning. This new Plan built on the accomplishments of their 2015-2020 Strategic Plan. The goals were to: - Articulate the mission, vision, and strategic goals for the MWRD for the next five years - Identify a set of strategic initiatives to achieve those goals - Provide a framework for measuring progress and reviewing/updating the Plan on an annual basis The planning process began in September 2020 and was completed February 2021. The Strategic Plan was formally effective on June 3, 2021. We undertook a comprehensive, staged approach that consisted of four consecutive phases: - Phase 1: Led an intensive and iterative engagement effort to assess the MWRD's current state and identify its desired future state. That engagement effort included MWRD leadership and more than 500 MWRD staff, as well as approximately 50 stakeholder organizations that participated in a stakeholder workshop — including the Chicago Metropolitan Agency for Planning, the Metropolitan Planning Council, and a range of environmental and community-based organizations — and members of the general public who participated in public-facing surveys. - Phase 2: Conducted a workshop with the MWRD's strategic planning Steering Committee, which identified five strategic goals: resource management; stormwater management; workforce excellence; community engagement; and enterprise resilience. The strategic goals were formulated based on information and opinions collected during Phase 1. - Phase 3: Facilitated working groups for each strategic goal and developed a Strategic Roadmap for the MWRD to implement, including 150+ sequenced initiatives and metrics to measure progress. - Phase 4: Finalized the Five-Year Strategic Plan, which includes 5 overarching strategic goals, 32 strategies (that support the goals), and initiatives and a framework for the MWRD to update the plan annually. We presented on global best practices and industry trends to help guide the visioning process, and facilitated external stakeholder workshops to bring perspectives from environmental organizations, local communities, and regional planning groups into the planning process for the first time in the MWRD's history. Our Strategic Planning team leveraged industry frameworks from organizations such as the National Association of Clean Water Agencies (NACWA) and Water Environment Federation (WEF); and augmented with other trending research such as City Water Resilience Approach (by Rockefeller Foundation, Stockholm International Water Institute, Arup) and Circular Economy principles (Ellen MacArthur Foundation) to create a context-specific Strategic Plan for the MWRD. This resulted in a Strategic Plan that is innovative, responsive to key trends such as the growing threat of climate change, and the racial and social inequity in Cook County. As a result of this process, the MWRD is equipped with a Strategic Plan guided by the principles of engagement, collaboration, innovation, equity, and resilience. The MWRD's vision for its future state has been updated, and given the racial and social inequity in the communities served by the MWRD, its core values have been expanded to include equity and diversity. Moreover, these values are reflected in the specific strategic initiatives outlined in the new Plan. For example, one key focus is to identify and eliminate barriers to participation for disproportionately impacted areas (DIAs) — low-to-moderate income areas that may be more susceptible to flooding, and that often have less capacity to partner with the MWRD to implement stormwater solutions and alleviate local flooding. The benefits and significance of the Strategic Plan will be far-reaching for the MWRD to give a positive social impact to the communities it serves. These include: - Integration of an equity lens into the District's vision and strategies, to reduce the disproportionate impact of flooding and other water management challenges on low-to-moderate income areas in Cook County - District is equipped with a robust, collaborative, and community-informed strategic planning process that will guide it to a path to a more sustainable future The presentation will provide the following: - An overview of the overall strategic planning process - Steps to make the process more inclusive, and how staff at all levels were engaged, and how external organizations and the public were engaged - Identify the industry related frameworks that were used to develop the Strategic Plan - A review of key themes and initiatives identified in the Strategic Plan - Key outcomes that will forge stronger and more equitable connections with the communities the District serves - Lessons learned from conducting this process remotely and in virtual environments
This paper was presented at the WEF/AWWA Utility Management Conference, February 21-24, 2022.
Presentation time
11:00:00
11:30:00
Session time
10:30:00
12:00:00
SessionStrategic Planning
Session number3
Session locationHyatt Regency Grand Cypress, Orlando, Florida
Author(s)M. Garcia 1; V. Lee 2; C. OConnor 3; J. Witko 4; A. Fremier 5
Author affiliation(s)MWRD 1; Arup 2; MWRD 3; Arup Stokes 4; Arup 5
SourceProceedings of the Water Environment Federation
Document typeConference Paper
Print publication date Feb 2022
DOI10.2175/193864718825158201
Volume / Issue
Content sourceUtility Management Conference
Word count20
Description: Setting Expectations: Providing Flexible Project Guidance to Align the Management of...
Abstract
Abstract Description Loudoun Water's Project Support Office (PSO) has undertaken an innovative, yet practical, approach to establishing guidance documentation for the initiation, execution, and closing of projects across its many groups and needs. The resulting Project Delivery Guidance documentation avoids the common pitfalls of standardization efforts to provide accessible, actionable guidance to project managers across the organization. Abstract Located in the westernmost suburbs of Washington, D.C., Loudoun Water provides public water, reclaimed, and wastewater services to one of the fastest-growing areas of the country. As a result of recent growth, over half of Loudoun Water's infrastructure was installed in the last twenty years. The rapid growth will not stop- over the next thirty years, the area's population is expected to increase by another 125,000. Loudoun Water's capital planning assessments show that over one billion dollars in capital infrastructure is needed to serve future customers. Loudoun Water's responsibility to implement capital projects at such a hurried pace coupled with the need to update the two decades old project delivery system led to a strategic initiative of establishing a Project Support Office (PSO). The PSO works with various departments/divisions, supports to implement the capital and O&M projects, and carries out portfolio and program management level activities. The PSO led many tasks during its initiation to establish and ensure that optimal and required project management practices were followed across the organization to implement capital projects. The PSO assists project managers and project teams with their efforts to improve project definition, schedule, cost, and quality performance for their projects by defining minimum expectations and providing guidance and oversight. A primary goal of the PSO is to provide support documentation to aid project managers across the various divisions and departments to successfully initiate, execute, and close projects. As part of this goal, the PSO embarked on the development of a series of guidance documents aimed at providing project managers with a common understanding of the key deliverable components at typical design milestones, including preliminary engineering, 60% design completion, 90% design completion, and bid-ready design submittal. The Project Delivery Guidance documentation details the expected components (mandatory and optional) and completion level of specifications, design drawings, permitting, and coordination items at each design milestone. This presentation will describe Loudoun Water's approach to developing and implementing their new Project Delivery Guidance. A key focus of this process was soliciting input and generating buy-in and acceptance of the various stakeholder groups across the organization through collaborative workshops and guideline review cycles. The presentation will detail how Loudoun Water solicited feedback and insight into the processes and approaches of similar utilities and navigated the common pain points and pitfalls often associated with efforts to standardize an approach to critical processes across such a large organization. This work resulted in guidance documents that were broad enough to meet the varying needs of projects across Loudoun Water will be specific enough to provide actionable information to assist in the execution of projects.
This paper was presented at the WEF/AWWA Utility Management Conference, February 13-16, 2024.
Presentation time
10:30:00
12:00:00
Session time
10:30:00
12:00:00
SessionStrategic Planning A
Session number03
Session locationOregon Convention Center, Portland, Oregon
Author(s)S. Kolapalli1, M. Dalton2, T. Lipinski1, C. Brennan2, R. Nagel
Author affiliation(s)Loudon Water 1; Hazen and Sawyer 2;
SourceProceedings of the Water Environment Federation
Document typeConference Paper
Print publication date Feb 2024
DOI10.2175/193864718825159321
Volume / Issue
Content sourceUtility Management Conference
Word count16
Description: Application of Machine Learning in Stormwater Risk Management for the Johnson County...
Abstract
The Stormwater Management Program (SMP) is a Johnson County, Kansas program which partners with the 20 cities in the County to manage stormwater and is funded by a 1/10th of one percent, county-wide sales tax. It administers these funds on behalf of the Cities, historically by providing matching funds to Cities for eligible projects, including study, design, and construction projects. In 2016, SMP as part of new strategic asset management program implemented watershed-based approach to fund projects that incorporate flooding, water quality, and system management. Under 'System Management' program, SMP started funding inspection, rehabilitation, and replacement of stormwater asset projects. As part of this program, SMP developed a risk-based tool to prioritize stormwater assets. This tool is used to assign a prioritization score to all eligible assets contained in County-wide asset database. This prioritization score is calculated using Likelihood of Failure (LoF), Consequence of Failure (CoF), and total risk (Business Risk Score, BRE). The two fundamental building blocks for defining total risk (BRE) are LoF and CoF. LoF describes the chance of an asset failure occurring and CoF measures the severity of the impacts if an asset were to fail. Total Risk or BRE = LoF * CoF Currently, SMP employs a linear age-based degradation model and incorporates an adjustment factor for increased salt load in estimating LoF. to prioritize inspection of stormwater assets (hard assets). For rehab/replacement projects, field verified condition score is used. However, existing field verified condition rating systems like the National Association of Sewer Service Companies' (NASSCO) Pipeline Assessment and Certification Program (PACP) and Water Resource Commission (WRC) were initially developed for wastewater systems. These standard ratings do not capture the environment factors and other variables specific to stormwater pipes. Currently, no standardized methods exist for assessing the condition of stormwater pipes and structures in the U.S. Given these challenges, SMP engaged with NEER to utilize its cloud-based Machine Learning (ML) solution to identify the risk condition of the stormwater assets and implement a proactive data driven asset management program. As a part of this project, NEER developed a Machine Learning (ML) Model that is specific to Johnson County SMP to calculate LoF for all the hard assets such as inlets, junction boxes, bridges, culverts, enclosed gravity. All of these assets are represented either as Links or Nodes. During the ML model creation, all the data obtained from AIMS and local municipalities (physical, functional/operational) were standardized. The NEER team developed micro-ML models to populate several missing parameters for few nodes and links. In addition, several environmental parameters were also superimposed to the existing datasets. After the normalization of the datasets, the original datasets (113,124 links and 122,957 nodes) that had field verified conditions were selected for model training and validation. There were 39,814 links (35% of total links) and 44,600 nodes (36% of total nodes) that had field verified conditions. NEER was able to develop a best performing ML model using 80% of the data (field verified conditions data) for model training and the rest of the 20% of the data (field verified conditions data) for model validation. This ML model is able to predict LoF with an accuracy of 90% & 91% respectively for the existing nodes and links. This SMP specific LoF prediction ML model was configured to continuously train and optimize itself to improve accuracy over time. NEER also adopted the same methodology that is currently being used by SMP to calculate the CoF and Business Risk Exposure (BRE)/Total Risk score. This CoF and BRE/Total Risk score calculation was implemented in the NEER Platform, so that SMP can calculate CoF and BRE/Total Risk for each asset in Watershed Organization 1.
This paper was presented at the WEF Stormwater Summit, June 27-29, 2023.
Presentation time
14:00:00
14:30:00
Session time
10:45:00
15:00:00
SessionSession 03: Applying Technology to Elevate Stormwater Management
Session number03
Session locationKansas City Convention Center
Author(s)E. Thevar1; S. Smith2;
Author affiliation(s)NEER1; Johnson County, KS2;
SourceProceedings of the Water Environment Federation
Document typeConference Paper
Print publication date Jun 2023
DOI10.2175/193864718825158953
Volume / Issue
Content sourceStormwater
Word count17
Description: Importance of Digester Foaming Control in Moving Towards Energy Neutrality
Abstract
INTRODUCTION Sustainability is increasingly more important for the operation of wastewater treatment plants. To meet sustainability goals and better energy recovery, the current business as usual approach to anerobic digester operation is not ideal. Improving digester operation is crucial for effective energy recovery. Having a reactive approach to digester foaming prevents optimal digester performance and causes other problems like digester failure, poor biogas recovery, uncontrolled release of contaminated waste to the environment and odour. Figure 1 shows some of these impacts. The best way to mitigate digester foaming is through robust design, but if this is not possible there are several operating conditions that can be improved to control foaming. Sydney Water Corporation (SWC) recognised the importance of preventing anaerobic digester foaming. Digester foaming at SWC plants has been caused by multiple different issues and foam management can therefore be largely reactive. There are operational methods and digester design features in place at some plants that aim to reduce the occurrence of the impacts of foam events, however this is not widespread or consistent. Investigation into 5 plants was undertaken to determine the likely causes of digester foaming and gas entrainment and the most effective ways to manage this and where possible through design changes as upgrades occur. For plants where design changes are not possible in the near future, key operating conditions were reviewed, early warning signs for digester foaming events determined and management practices recommended to mitigate digester foaming. METHODOLOGY Digester foaming was investigated at 5 SWC Water Resource Recovery Plants (WRRP), including Cronulla, Malabar, Warriewood, West Hornsby and Hornsby Heights. Digester operation data was analysed to determine the likely causes of digester foaming issues and recommendations on proactive and reactive measures for foam management including how to prevent or mitigate foaming at these plants and across broader SWC plants were established and operator training provided. Digester operation parameters and recommended monitoring were also outlined. Best practice digester design to minimise foaming and maximise energy production was investigated, drawing on international experience. These design components were presented to SWC designers, along with recommended implementation methodologies. RESULTS The main issues causing digester foaming at the SWC plants investigated were seasonal foaming related to activated sludge processes, lack of effective redundancy or contingency measures associated with the digester process, and illegal industrial discharges to the incoming sewer. There are other fundamental operating issues that cause digester foaming, such as running with one digester offline for extended periods (for example, at 2 plants digesters were offline due to issues with digester lids, which resulted in excessive volatile solids load in remaining digester/s particularly when food waste was accepted), turning off mixing, high volatile solids loading rates in digesters, poor temperature control, unstable feed to the digesters, and large step changes in temperature and feed. Figure 2 shows the volatile solids (VS) loading rate and specific volatile solids loading rate (SVSLR) in the primary digester at one of the plants where primary and secondary digesters are currently operated in series. At this plant, there is inadequate solids retention time (SRT) in the digesters, as well as a high VS loading to the primary digester. The average VS load to the primary digester was 3.74 kgVS/m3.d and a peak loading rate of 4.5 kgVS/m3.d, where the recommended range is 1.6-3.2 kgVS/m3.d . Therefore, the anaerobic digesters are operated beyond the typical recommended VS loading rates. The high VS loading rate is also exacerbated by the unloading/loading sequence of flow, which results in intermittent VS loading, rather than constant loading across the day. The high VS load impacts the stability of the sludge and increases risk of foaming in the digesters. The SVSLR is a variation of VS loading rate that considers the VS in the digester as a function of active biomass. However, SVSLT may not account for the feedstock other than the wastewater sludge such as high strength organic matter. The maximum recommended SVSLR for mesophilic digestion without any pre-treatment is 0.16 kg VS/kg VS in digester day. As shown in Figure 1, along with the VS loading rate, the SVSLR for the primary digester is consistently above the recommended limit, making it vulnerable to the digester foaming and failure with fluctuation in digester loading rate. Best practice digester design to avoid foaming issues and maximise energy recovery include the use of standpipes for surface overflow (see Figure 2) and emergency withdrawal via p-traps (see Figure 3), minimisation of the top water surface area, installation of fixed covers and external gas storage, the use of pumped mixing to reduce short-circuiting and having adequate redundancy to ensure that there is no single point of failure. Digesters should have a conical shape to facilitate grit removal and more efficient mixing. Wasting foam from the surface in secondary activated sludge processes will also minimise the amount of trapped foam, improving conditions in the downstream digesters. Rolling out design changes in a systematic way as digesters are taken offline for planned maintenance is an effective way to facilitate continuous removal of foaming issues from upgraded digesters. In addition to benefits of maximising energy generation, achieving maximum hydraulic capacity within existing digesters by having external gas holders and running digesters full may allow capital upgrades of digesters to be delayed for a number of years if not decades, further improving sustainability of WRRPs. Where design changes cannot be implemented, there are operational improvements that can be made to manage digester foaming and increase energy production. Generally, if there are filamentous bacteria in the activated sludge bioreactor at a plant, there is a high likelihood of foaming in the digester. These foaming incidents are manageable through adjusting the operating parameters in the activated sludge plant. Digesters should be brought online slowly with small step increases in feed and temperature over time. A common misconception is that digester mixing should be turned off to control a foam event, however mixing should be turned down. Digesters should be operated with a top water level high into the lid, with sprays used to suppress foam and move foam to wasting points. Digested sludge should be withdrawn from the top and bottom of the digester, and consideration given to alkalinity correction when the pH in the digester starts to drop. Running the digesters without any safety factor and running some process equipment at loading rates higher than designed for will increase the risk of process upsets that could also contribute to foaming. Allowing a safety factor in terms of solids retention time and volatile solids loading provides plants with the ability to cope with under upset conditions and avoids the need to detune the digesters and the plant to minimise the risk of foaming. CONCLUSION By successfully managing digester foaming and operating digesters in a manner than maximises power generation, WRRPs can achieve more effective energy recovery and meeting energy sustainability and neutrality goals. Some fundamental issues that generally arose to cause digester foaming were: -Running with one digester offline for long periods resulting in much higher loadings and shorter SRT than originally designed -High VS loading rates in the digesters -Reduced effective SRT due to mixing being turned off and accumulation of grit and screening -Mixing generally not designed for current solids loading due to intensification -Poor temperature control for the digesters -Unstable feed to the digesters -Large step changes in temperature or feed due to heater failure or storm conditions Foaming subsequently resulted in lower biogas production, high costs for digester reinstatement, and poor run times on biogas engines due to poor biogas quality. Robust digester design which minimises digester foaming and gas entrainment is the most preferable management mechanism, and changes to digester components can be implemented over time as maintenance is undertaken. Where design changes are not possible, operational improvements can be made to greatly reduce digester foaming. This paper outlines some best practice measures that can save millions of dollars by avoiding catastrophic foaming events and will help maximise biogas production and energy generation.
This paper was presented at the WEF/IWA Residuals and Biosolids Conference, May 16-19, 2023.
Presentation time
11:15:00
11:45:00
Session time
10:45:00
11:45:00
SessionSession 03: Digestion Optimization and Troubleshooting
Session number03
Session locationCharlotte Convention Center, Charlotte, North Carolina, USA
Author(s)
Author(s)A. McDonald1, J. Cesca2, G. Bharambe3, D. Parry4, J. Gonzalez5,
Author affiliation(s)Jacobs1; Sydney Water Corporation2
SourceProceedings of the Water Environment Federation
Document typeConference Paper
Print publication date May 2023
DOI10.2175/193864718825158821
Volume / Issue
Content sourceResiduals and Biosolids
Word count11
Description: Advanced psichometrics based on citizen science. A history, a new standard, a...
Abstract
For more than 30 years, technical standards and criteria have been developed to quantify odor concentrations, odor characteristics such as intensity, hedonic tone and odor impacts. Within these 'traditional methods', and most of the odor regulations around the world, the capacity and knowledge of citizens are largely excluded from the analysis. However, involving citizens in gathering data about odor nuisance can significantly reduce the cost of odor studies, while giving citizens the knowledge and tools to address the odor pollution that affect them. WEFs MOP 25 also mentions citizen monitoring as part interactive community outreach programs that could collect data to represent real conditions in the community that also might help understanding the strength at which an odor becomes a nuisance. In classical psychometry, there is a certain consensus on the four basic factors that affect the sensitivity of individuals: experience, expectations, motivation and the degree of alertness of the receiver. Sensitivity of groups is also affected by these four parameters. In the case of people exposed to odor impact, there are however other factors that affect group sensitivity such as: the amount of population affected (city, town, scattered houses, etc.), the land-use where the receptors are located (industrial, rural, hospital, school, etc.), the housing uses (continuous, occasional, fortuitous, etc.), or even the type of environmental protection that the impacted area may have. Weighting receptor sensitivity may be assessed using traditional psychometric tools. Psychometry is a science that deals with theory and techniques to measure psychological perceptions. The contents of psychometry are usually built upon two blocks: Theory of surveys/questionnaires/tests and, scaling, methods to perform scales, rules. Key concepts in psychometry are validity and reliability. These two parameters can be measured statistically. Odor managers have a nice tool box when they want to assess odor impact by using traditional psychometry. The most common techniques used are interviews, surveys, odor diaries and analysis of records of complaints. However, there are many limitations of these psychometric approaches, being the main one that the odor timestamp record is not accurate and thus, there are more difficulties in assessing the reliability of the odor observations recorded. Advanced psychometry, uses citizen odor observations in real time to asses odor impact in a community. There several initiatives dealing with this new way of evaluating odor impact. The European Union Horizon 2020 Science with & for Society Call funded Distributed Network for Odour Sensing, Empowerment and Sustainability (D-NOSES) project aims to develop a methodology based on participatory strategies, collaboration of different stakeholders using an extreme citizen science approach. Building on action research and participatory design (Foth et al., 2006), the goal of the project is to support and guide a collaborative journey to tackle odor pollution with the active involvement of key stakeholders from the public sector, business, civil society, and academia. In the D-NOSES methodology (Balestrini et al, 2018; Arias et al., 2019), citizens are part of this process by framing odor issues in their affected areas. This is done through identifying local odor problems, collective data collection, collective analysis of the results and co-designing measures to tackle odor pollution. Data collected by citizens shows a real, local understanding of the problem, and reduces costs of odor pollution measurements at the same time. As part of the D-NOSES project, a pilot study has been conducted in Los Alamos, Chile (15,000 inhabitants). Modifications to the 20 year old WWTP were introduced in 2018, including a technology shift from SBR to Activated Sludge and scrubbers and biofilters for odor abatement. Still, the WWTP impacts three neighborhoods (Villa Caupolic¡n, Villa Esperanza and Kintupi Ruca), which are located in the dominant wind direction. The case study started in June 2019 with an odor annoyance assessment questionnaire as described in VDI 3883 part 1. The aim of the odor annoyance assessment was to have a clear, not biased, image of the affected areas, in order to have an improved focus of the citizen engagement strategy. Results indicate a plausible relation between odor annoyance values measured with the verbal and the thermometer scale. The latter ranges from 0 (not annoyed at all) to 10 (extremely annoyed). Arithmetic means for Villa Caupolic¡n (close to source) was 5.7. Kintupi Ruca averaged 3.4, while Villa Esperanza and Villa Caupolic¡n (distant to source) 1.7. Field inspections are carried out since December 2018 by trained assessors to determine the impact frequency of recognizable odors in terms of odor hours, using the grid method described in VDI 3940 part 1 (EN 16841). The assessment area covers the three neighborhoods with 17 assessment squares. No odor impact was observed for Villa Esperanza and distant to source zone at Villa Caupolic¡n. Close to the source zone at Villa Caupolic¡n and Kintupi Ruca largely have odor impact characteristics below the 10 % threshold value, but two assessment squares located nearby a pumping station exceed this threshold. Citizen data collection started at the end of November 2019 and was suspended in May 2020 due to the corona pandemic. In addition to random observations, a group of local residents were trained as panelists to realize twice a day a predefined 1.8 km track covering 17 of the 29 measurement points considered in the field inspections, reporting odor observation by using the OdourCollect app. The app enables to report types and sub-types of odors, intensity, hedonic tone, and comment on the duration of the odor episode and the potential source. Geographic coordinates and a timestamp are automatically recorded. Data analysis of the citizen monitoring comprises more nearly 3,000 individual observations. Therefore, new indicators are developed, adopting those proposed by traditional technical standards: Observations frequencies are calculated for each assessment zone, using the grid method evaluation described in VDI 3940 part 1 (EN 16841). Citizen had not been trained on VDI 3882 part 1 (odor intensity) nor on VDI 3882 part 2 (hedonic tone), but both characteristics can be reported with the OdourCollect app. The observed relation between hedonic tone and intensity can be described as linear functions. Finally, a weekly annoyance index is calculated for each assessment square and observation week using the equation given in VDI 3883 part 2. Therefore, the reported odor intensity is related to an annoyance category. The aim of this study is to identify drawbacks and potentials of combining different approaches in which citizens take an active role. It will also present advances in the development of a new standard based on the construction of collaborative odor maps through citizen science. The development of the standard is being promoted by the International Environmental Association of Odor Managers (AMIGO) and a handful of other groups and experts.
The following conference paper was presented at Odors and Air Pollutants 2021: A Virtual Event, April 20-22, 2021.
Presentation time
15:20:00
15:40:00
Session time
15:00:00
16:30:00
SessionPlanning the Odors Away
Session number3
Session locationLive
Author(s)Gerhard Schleenstein1; Carlos Diaz Jimenez2; Cyntia Izquierdo3;
Author affiliation(s)Ecotec Ingenieria1; Ambiente et Odora2; Ambiente Et Odora S.L.3
SourceProceedings of the Water Environment Federation
Document typeConference Paper
Print publication date Apr 2021
DOI10.2175/193864718825157937
Volume / Issue
Content sourceOdors and Air Pollutants Conference
Word count21
Description: Overcoming Operations and Maintenance Challenges in Siphons
Abstract
Some of the more complex pipes that reside within the wastewater collections system are known as siphons/depressed sewers and are often referred to in the field as 'bellies' or 'sags.' Such systems typically navigate wastewater flow in pipelines that are near bodies of water, subways, tunnels, and other fixed utilities. These lines are constructed when traditional gravity design is not permissible, and a continuous grade cannot be maintained. Flow navigates the siphon pipe until it reaches pressurized flow and often creates foul odors which can be minimized by air lines. Siphon design allows for single barrel, double barrel or multi barrel and the number of barrels is typically related to the agency's requirements on hydraulic efficiency, maintenance, emergency events, and bypass requirements. Additionally, siphon design is critical for the future life span of the pipe due to its impact on operations. A poor design can lead to blockages, sediment build up and direct impacts on minimum velocities that are critical in siphons. For operations and maintenance this is critical because Siphon debris levels must be monitored closely to evaluate future needs for additional barrels, increased maintenance requirements and necessary repair work. In this abstract we concentrate on different operations and maintenance approaches on various siphons and the economic impact it can create for the utility owner and contractors. The first approach that will be discussed will be centered around cleaning siphons that have not been maintained and where minimal information is available. Secondly, the methodology of inspection and the various means that can be attempted dependent on the technology used. Lastly the combined approach of both inspection and cleaning will be discussed and evaluated. One of the most expensive approaches is often seen as is one in which the contractor blindly attempts to clean a sewer line (whether it be a siphon or not) without the known conditions of the pipeline. Not only is this a high-risk module but it is one where variables such as the structural integrity of the pipe, sediment levels, unknown debris types, and so much more are put into question. This approach will discuss a few siphons in San Bernardino that where maintained under a clean first approach. An inspect first approach can often be the least economically bearing approach because it is one that assumes it has minimal information from the start. This is because this method creates the information the owner can utilize to provide details about the siphon. Sonar and CCTV will be discussed and how the different technologies provide for varying deliverables and the limitations of each. Finally, one of the most comprehensive approaches is one in which the siphon is inspected, and the asset is assessed providing tangible details so that the line may be properly cleaned at a price that is well evaluated. This method will discuss the success of an inspect/clean siphon project in San Diego. This presentation will provide much needed information for a topic that has very limited information. This is because nationwide siphons are sometimes not maintained due to costs and or limited staff already strained by the primary collections system. The specialized work is one that is becoming more necessary and vital due to the aging assets and the imperative need to avoid emergencies on them.
This paper was presented at the WEF Collection Systems Conference in Detroit, Michigan, April 19-22.
Presentation time
13:30:00
14:00:00
Session time
13:30:00
16:45:00
Session number3
Session locationHuntington Place, Detroit, Michigan
Author(s)
Author(s)V. Alvarez1
Author affiliation(s)RedZone Robotics, Inc1
SourceProceedings of the Water Environment Federation
Document typeConference Paper
Print publication date Apr 2022
DOI10.2175/193864718825158369
Volume / Issue
Content sourceCollection Systems
Word count8
Description: Follow the Drop: Empowering Communities to Build Water Security & Resiliency
Abstract
Follow the Drop is an innovative mobile application and data platform that is designed to enable cities to respond to climate change by collecting stormwater metrics and helping property owners to reduce flooding and pollution. Initial funding to develop the software came from the State of Hawaii Water Security Advisory Group and the Hawaii Community Foundation to support the reduction of stormwater runoff as well as build water security to meet Hawaii's Freshwater Initiative goals to increase water supply by 100 million gallons per day by 2030. In partnership with a local nonprofit, the initial prototype was beta-tested in Hawaii schools to ensure ease-of-use and was coupled with a 13-lesson plan design-thinking course for green infrastructure. Today the software and data platform is serving as a community engagement tool to support municipal green stormwater infrastructure (GSI) programs. Follow the Drop incorporates local rain sensor data and by taking a photo of an opportunity to capture stormwater from a drainage device (ex. downspout, catch basin, etc.), Follow the Drop automates the annual stormwater runoff volume, provides the optimum size green infrastructure system for that opportunity, and displays the volume of stormwater captured for the size and type GSI system inputted. The software also serves as a decision tool; the user is able to collect data from multiple opportunities and congregate and compare them in chart, map, or list view, to identify the best size and location for their green infrastructure project. Specifically for stormwater utilities (SWUs), the app can be distributed to its customers to identify opportunities to capture stormwater onsite to receive a potential fee credit, rebate and/or grant. The municipal agencies are able to track the locations, sizes, status and volumes of stormwater captured of submitted projects to support green infrastructure asset management, maintenance assurance, billing/fee credit management, compliance reporting, and sustainability metrics. The software is being piloted by the City and County of Honolulu to support its future SWU GSI incentive program to simplify the application process for property owners to submit GSI projects to receive fee credits. The presentation will provide the background including water resiliency goals set forth by the Hawaii Freshwater Initiative, current use cases and data output from the software for the Pilot, and next steps of the Follow the Drop program.
The following conference paper was presented at Stormwater Summit 2021: A Virtual Event held June 22-23, 2021.
Presentation time
11:40:00
12:00:00
Session time
11:00:00
12:00:00
SessionInnovation and Technology
Session number3
Session locationSimu-Live
Author(s)
Author(s)L. Venu1
Author affiliation(s)3Rwater, Inc.1
SourceProceedings of the Water Environment Federation
Document typeConference Paper
Print publication date Jun 2021
DOI10.2175/193864718825157969
Volume / Issue
Content sourceStormwater Summitt
Word count12
Description: Californias Revised Sanitary Sewer Regulations - Ready, Set, Go
Abstract
In 2006 the California State Water Resources Control Board (SWRCB) adopted waste discharge requirements (WDR) for sanitary sewer systems that currently regulate 1200 publicly operated collection systems with greater than one mile of sewers discharging to a publicly owned wastewater treatment plant. In 2013 these regulations were amended to modify the reporting requirements into the State sewer overflow database CIWQS, modifying the reporting categories for sewer overflows and requiring technical reports and sampling for overflows greater than 50,000 gallons. In 2019, professional organizations representing the enrolled agencies began discussions with the SWRCB staff regarding necessary changes in the requirements. Those discussions resulted in the public circulation of an Informal Staff Draft (IFSD) in February 2021by the SWRCB of a proposed replacement of the WDR. That draft was 85 pages long proposing to replace the 20-page 2006 WDR. It is the SWRCB's stated intention to revise and improve the enforceability of the WDR and to clarify and enhance system operational information from the 1200 enrolled agencies. In addition they have stated that the drivers for the revisions include the following SWRCB policies: -Reducing the cost of compliance (SWRCB Resolution 2013-0029) -Human Right to Water (SWRCB Resolution 2016-0010) -Comprehensive response to Climate Change Requirements Resolution 2017-0012) -Open data portal (SWRCB Resolution 2018-0032) -2017 Water Quality Enforcement Policy It is anticipated that the SWRCB will issue a Board WDR draft in late fall or early winter, and begin Board hearings following a 60-notice period in early 2022 with final WDR adoption in spring or early summer 2022. The 2006 and 2013 WDR requirements have resulted in meaningful reductions in both the number and volumes of sewage overflows across the state. The required State database for the reporting of all sewage enrolled agency overflows contains over 65,000 individual sewage overflow records since initiation in 2007. Total number of annual overflows have been reduced by almost 60% and the total volumes of overflows have dropped by approximately 40%. However large overflows greater than 1000 gallons discharging to Waters of the United Stated continue to be an area of concern to the SWRCB and to the enrolled agencies and are generally the result of winter weather issues or large diameter or force main failures. The SWRCB has done very limited enforcement on these large overflows but has not had the staff to deal with most. It is the enrolled agencies belief that greater enforcement and liability for the very small number agencies with these large overflows to waters of the US should be the first step in requiring compliance rather than a wholesale replacement of the 2006 WDR with substantial impacts on ALL 1200 enrolled agencies. The speaker has chaired the professional associations negotiations in the past two plus years with the SWRCB staff resulting in a substantial comment letter and redline markup of the IFSD for SWRCB staff considerations. These documents were submitted after a three-month intense face-to-face discussion period over the significant changes and poor language of the IFSD. The proposed changes in the IFSD were very prescriptive, enhanced enrolled agency legal risk and liability for expanded non-compliance while substantially expanding the operational requirements and information to be provided from enrolled agencies both annually and in the required sewer system management plans. The current podium presentation will review the successes of the 2006 WDR, discuss many of the significant new issues and anticipated requirements included in the WDR replacement requirements and the timeline for the 1200 enrolled agencies to obtain compliance. It is expected that these new sanitary sewer collection system requirements when adopted will be expensive especially for small and disadvantaged communities and will result in expanded consulting support services and litigation and enforcement on many sewer collection agencies. Several of the new topics anticipated to be in the revised WDR and to be covered at the podium may include the following: -Exfiltration from sewer systems -Resiliency requirements/ Capital Asset Management requirements -Substantially expanded Sewer System Management Plans requirements -Expanded annual reporting to State and Regional Boards -Expansion of sewer program financial, rate information and capital planning -Enhanced State enforceability -Detailed definitions of important terms used by the State -The inclusion of groundwater as the definition for Waters -Reduced requirements for well performing systems -Inclusion of private property systems satellite to enrolled agencies -Submittal of service area boundary mapping including surrounding water and sewer agencies -Requirement for Registered Engineers or collection system certified operators as designated officials -Use of Spill Rates per 100 miles per year for enrolled agency comparisons and performance evaluation It is expected that the new WDR will require additional public expenditures to comply even though it may, in the long term, enhance the operations of sanitary systems. As with many California regulations, these new requirements may inform other states and sanitary sewer regulations across the United States from the required changes and many new and expanded requirements. We have estimated that the resiliency requirements alone may require enrolled agencies to expend between 50 and 100 million dollars to comply. We also expect that this will require agencies to raise rates to customers to comply and will result in expanded NGO litigation and enforcement resulting from the revised WDR impacting agencies staff time for implementing compliance. This replacement of the 2006 WDR appears to move compliance enforcement to the private sector and away from the SWRCB Enforcement office due to staffing limitations. This may further enhance and expand the current cottage industry of sewer program litigation in California.
This paper was presented at the WEF Collection Systems Conference in Detroit, Michigan, April 19-22.
Presentation time
15:45:00
16:15:00
Session time
13:30:00
16:45:00
Session number3
Session locationHuntington Place, Detroit, Michigan
Author(s)
Author(s)P. Causey1
Author affiliation(s)Causey Consulting1
SourceProceedings of the Water Environment Federation
Document typeConference Paper
Print publication date Apr 2022
DOI10.2175/193864718825158325
Volume / Issue
Content sourceCollection Systems
Word count10
Description: Peer Scanning, Informative Interviews, and Design Thinking — Tactical...
Abstract
Transforming a utility's culture to embrace innovation requires redefining behavioral norms and recruiting stakeholders into the innovation environment. Often, utilities struggle with establishing innovation cultures due to ineffective change behavior techniques as well as complex and inflexible supply chain relationships. Peer scanning, informative interviews, and design thinking are all effective tools that can assist utilities with breaking down these barriers. Our team used these tactical approaches to serve as the catalyst for understating how to leverage innovation for the Birmingham Water Works Board (BWWB). BWWB sought out ways to use innovation for financial impact. It began by conducting a survey to determine ways that peer utilities have reduced operating expenses, reduced/delayed capital expenditures, generated revenue, experience economic development, or 'delivered value' to the customer. 17 utilities were surveyed to understand how they utilize innovation to improve their financial bottom line. Through exploring ways to reduce operating expenses, generate revenue, and optimize capital expenditures, utilities are using innovation to overcome financial hurdles. Insights emerged, detailing that utilities have felt real financial benefits from implementing innovative ideas, technologies, and business processes. 100% of the utilities experienced reduced operating expenses. While 47% experienced reduced capital expenses, only 29% of the utilities experienced increased revenue. Most utilities reported benefits were long lasting and were not one-time. 12 of the surveyed utilities participated in informational interviews to gather further details on their approaches. From conducting interviews, BWWB gained insight on items for possible implementation. Over 20 suggestions were mentioned; it included ideas such as regionalizing services to leveraging assets to partnering with vendors to develop technology. Overall, the initiatives mentioned were aligned with alternative revenue, economic development, cost savings, and management of customer expectations. To determine the feasibility of implementing some of the innovation approaches discovered, BWWB vetted the unique ideas. Since BWWB had already implemented several strategies similar to peer utility initiatives, those opportunities were not considered further. BWWB ultimately selected to vet 4 opportunities through the design thinking process. Tim Brown, the president of the design house IDEO, defines design thinking is defined as 'a human centered and collaborative approach to problem solving, using a design mindset to solve complex problems.' By bringing together diverse stakeholders and perspectives to engage on strategic opportunities, design thinking places the human at the front and center of a problem. Our process followed 3 themes: -Learn: Examine opportunities through the lens of all stakeholders involved and consider the jobs done by key players. -Inspire: Explore innovation approaches that have been successful in other utilities. -Create: Generate ideas that addressed opportunities identified in the Learn session and then developed an actionable roadmap to bring the ideas to fruition. Our team will present BWWB's case study approach to building its innovation culture as well as detail lessons learned along the way. BWWB recognizes that a culture of innovation is born when everyone can play. By using tactical approaches, BWWB focused on fostering new behavioral norms and engage key stakeholders in the organization as building blocks for developing its culture of innovation.
This paper was presented at the WEF/AWWA Utility Management Conference, February 21-24, 2022.
Presentation time
10:30:00
11:00:00
Session time
10:30:00
12:00:00
SessionStrategic Planning
Session number3
Session locationHyatt Regency Grand Cypress, Orlando, Florida
Author(s)Z. Seymour 1; J. Carter 2; P. Flannelly 3; M. Johnson 4
Author affiliation(s)Arcadis 1; UMC Speaker 2; UMC Speaker 3; Birmingham Water Works 4
SourceProceedings of the Water Environment Federation
Document typeConference Paper
Print publication date Feb 2022
DOI10.2175/193864718825158215
Volume / Issue
Content sourceUtility Management Conference
Word count13
Description: An Evaluation of Masked Nuisance Odors from a Source by Chemical and Sensory...
Abstract
Nuisance odors are caused by chemical odorants. Recent studies at the Orange County Sanitation District (OCSD) at two wastewater treatment plants showed that, besides hydrogen sulfide [H2S], eight other odorants in four different family of compounds were consistently present (1). These were rotten vegetable and garlic odorants (methyl mercaptan [MM], dimethyl sulfide [DMS] and dimethyl disulfide [DMDS]), ammonia, earthy/musty/moldy odorants (2-methylisoborneol [MIB] and 2-isopropyl-3-methoxypyrazine [IPMP]) and fecal odorants (indole and skatole). The odor profile method (OPM) with a trained odor panel was used to assess these odors during dilution of the samples. The OPM uses a 7-point odor intensity scale that is based upon the drinking water flavor profile analysis (FPA), a standard method of water analysis (2). The odorous air was diluted by an olfactometer in stages from Teflon bag samples and followed by an OPM analysis to show the decrease of odor upon dilution and the appearance of masked odors. The wastewater odor wheel was used to standardize odor descriptors during the analysis, Figure 1 (3). The objective of this study was to describe a new methodology to: 1) determine the concentration at which each odorant most probably becomes a public nuisance and 2) demonstrate how olfactometry and the OPM can be used together to show masking of odorants in real life foul air samples when the samples are diluted from a source. Experimental The Odor Threshold Concentrations (OTCs) were determined by a triangular forced choice sample presentation for each odorant (4). Each panelist was forced to choose between two blanks and an odorous sample. The panelists were asked to provide an odor intensity rating during dilution of the sample by an olfactometer, using the FPA scale. The odor intensity scale is based upon the Weber-Fechner Law (4) where a single odorant's intensity is proportional to the Log of the odorant's concentration. Odor Intensity (I) = k Log (Concentration) + b Figure 2 shows the relationship between odorant intensity and the corresponding log value of odorant concentration. The red line is the odor concentration-intensity curve, which is asymptotic on both ends towards no odor and unbearable odor, respectively. The blue line is the section of the red line that obeys the Weber-Fechner Law. The odor threshold concentration (OTC) corresponds to odor intensity one (I=1) and the odor recognition concentration (ORC) corresponds to odor intensity four (I=4) for each odor when 50% of an odor panel can define the corresponding odor intensity. An action level or odor nuisance concentration (ONC) was suggested to be set at the intensity of three (I=3) to ensure action is taken before 50% of the general population recognizes the odor. Results: Odor Persistency Curves for Odorants Observed at the Wastewater Treatment Plants Figure 3 shows the OTC and the ORC of the nine persistent odorants at two wastewater treatment facilities determined by Weber-Fechner curves for each odorant using dynamic olfactometry combined with the OPM. The OTCs were within range of those determined in the literature. The ONCs have never been referenced in the literature. The odor nuisance concentration results presented here are important to odor control because they provide information defining the nuisance odorant's isopleths in modeling and avoid a public nuisance. Observing the Odor Masking Effect Observed at the Wastewater Treatment Plants Dynamic olfactometry combined with the OPM were also used with actual foul air samples from different sources. When analyzing the dilution of the initial source concentration, it was observed that the initially prominent fecal and sulfur odors gradually decreased with increased dilution (Figure 4). However, a musty odor began to gradually appear while the fecal and sulfur odors became undetectable. We named this observation the 'peeling of an onion effect'. It is apparent that this occurs because the musty odors in the foul air sample are masked by the fecal and the sulfur odors. An example of the 'peeling of an onion effect' is shown in Figure 4, which are the results of dynamic olfactometry analysis combined with the OPM. It illustrates the gradual change in odors perceived with progressing dilutions of a foul air sample of Activated Sludge Reactor at OCSD. The fecal (I=5.6) and sulfur (I=4.2) odors were initially prominent (with no musty odors reported) in the foul air. During dilution, the intensities of both the fecal and the sulfur odors decreased. At greater dilution ratios, musty odors emerged, and the other odors became undetectable, producing the 'peeling of an onion effect'. The results indicate that while fecal and sulfur odors may dominate at or near the sources, musty odors may be the primary nuisance at or beyond the fence line after some downwind distance where the public may be affected. The 'peeling of an onion effect' occurs due to the low OTCs of musty odorants; MIB (0.02 ppb) and IPMP (0.004 ppb) compared to those of fecal odorants; indole (0.5 ppb) and skatole (0.018 ppb) and sulfur odorants; DMS (3.0 ppb), H2S (0.51 ppb), DMDS (0.2 ppb), and MM (0.08 ppb). In the presence of fecal and sulfur odorants at high concentration levels, the musty odor is less perceivable unless the fecal and/or sulfur odors are 'peeled away'. Figure 4 shows that the slope of the regression line for IPMP is the most gradual, indicating that musty odors are more persistent in air because its odor intensity decreases slower with downwind dilution than the other odorants. In comparison, the fecal and sulfur odorants lines are clearly steeper, indicating a faster decrease in odor intensities with downwind distances. Thus, musty odors may cause problems at or beyond fence-line even if they are initially masked by sulfur or fecal odors at odor sources. This estimation must be verified by onsite OPM analyses at downwind distances from odor sources as atmospheric and topographical conditions will affect this behavior.
This paper was presented at the WEF Odors and Air Pollutants Conference, May 16-19, 2023.
Presentation time
15:45:00
16:15:00
Session time
13:30:00
16:45:00
SessionYou Can't Manage What You Can't Measure
Session number3
Session locationCharlotte Convention Center, Charlotte, North Carolina, USA
Author(s)
Author(s)M. Suffet 1; V. Decottignies 2; Y. Zhou 1; Y. Bian 1; T. Vitko 3
Author affiliation(s)UCLA1; CIRSEE Suez Enviroment2; Orange County Sanitation District3
SourceProceedings of the Water Environment Federation
Document typeConference Paper
Print publication date May 2023
DOI10.2175/193864718825158770
Volume / Issue
Content sourceOdors and Air Pollutants
Word count15