Conference Papers

Advanced anaerobic digestion processes offer unique opportunities for process intensification, biosolids product production and resource recovery. Thermal hydrolysis is the current state of the art for digestion enhancement, commercially available, typically doubling the capacity over conventional systems. Co-digestion in conventional digesters has demonstrated that doubling biogas production is possible with the right mix and quantity. Combining THP with co-digestion has the potential to maximize the bioenergy yield from a fixed volume of digesters. Hampton Road Sanitation District (HRSD) as part of its recent upgrades to its 54 MGD Atlantic Treatment Plant added thermal hydrolysis (CAMBI) and FOG receiving to enhance energy generation and provide a much-needed outlet in the region for resource recovery from fats, oils and grease. HRSD installed two B-6-4 CambiTM thermal hydrolysis units at the plant which discharges thermally hydrolyzed sludge to its 6 mesophilic anaerobic digesters. HRSD had the option of FOG addition pre or post THP, but to preserve the Class A biosolids status the sludge pre-THP was selected as the process configuration. The introduction of FOG to THP requires that it achieve the same level of pre-treatment that the sludge entering it, screened to less the 5 mm and largely devoid of grit. Combining these technical requirements and lessons learned from site investigations of operating co-digestion programs a first of its kind FOG receiving station feeding THP was designed and commissioned. Figure 1, shows the general process flow of the FOG system. It was designed around the using the Envirocare Beast and a pair of heated storage tanks to raise the temperature of the FOG to 131°F prior to introduction to THP. Based on prior experience with FOG receiving station design and operations a coned bottom to the FOG storage tanks was incorporated to allow for the deposition of grit, removing it from the material fed to the THP units. The cone based design also allows for decanting and concentrating of FOG if needed; otherwise the storage tanks are completely mixed. The heated FOG is then introduced to the pulper of the THP system, in place of dilution water. An extensive characterization study by HRSD (see Table 1) of its FOG found that at an average of approximately 6% solids FOG would serve as good source of dilution water, while enhancing the energy value of the feedstock to the digesters. Since commissioning in the summer of 2021, the FOG station as operated reliably; however unanticipated repairs to FOG receiving facilities at other HRSD plants resulted in higher-than-planned FOG loading to AT throughout 2021 (Figure 2). As a result, the FOG facility at AT operated close to its peak week design basis (Table 1) nearly continuously through its startup and early operation period without undue mechanical or operational difficulties. Some early lessons learned during early operation include: - Rheological properties vary widely in high strength wastes. Screens and systems designed to process 6% FOG were able to manage 20% humus production waste - Introducing FOG to the pulper has proven reliable and viable means of maximizing the energy yield of the system. - Additional FOG water storage (or decanting, in some applications) may be a useful feature to allow additional capture of FOG through the dedicated receiving system in lieu of processing through the headworks are peak loading conditions. Storage, rather than material processing and biological processing, have proved to limit the capacity of the AT system at unanticipated high loading. Operations the THP and digesters has proven to be stable even with the high FOG loadings, demonstrating the viability of the unique microbial population attributed to THP pretreatment. This is critical in demonstrating the overall efficacy of THP to be integrated into a larger resource recovery and bioenergy program. Early biogas production numbers were hindered by system leakage but since correction, has been in line with the anticipated loadings. As part of the discussion of operations the acclimation of the digester to FOG and other high strength wastes will be discussed, as introducing FOG to a THP digester is not the same as a conventional digestion system which is inherently influenced by the feed sludge active biomass. Further at the time of presentation the THP system will have been shut down and restarted as part of it annual inspection and maintenance providing further information on the impacts of FOG and high strength waste loadings on the THP process. But also provide information on the recovery of the biological process and a return to full loading under a co-digestion scenario. Overall this information is important as the adoption of THP increases across North America and little information is currently available surrounding the integration of co-digestion with THP. At the time of presentation nearly a year's worth of data and lessons learned will have been collected and presented.

Since 1998, Seattle Public Utilities (SPU) has innovated with retrofits of public right-of-way to improve stormwater using natural drainage systems (NDS). Based on lessons learned from prior projects and to address regulatory commitments, SPU launched the NDS Partnering program in 2017 to develop retrofits in the three major creek watersheds within the City: Longfellow Creek, Thornton Creek and Piper's Creek, see Figure 1. Due to topography, historical development patterns and standards and economic considerations much of this part of the city consists of informally developed right-of-way without curb or formal drainage infrastructure. This presentation will share the program goals, a summary of the site selection process and more importantly lessons learned in addressing the challenges and opportunities of partnering to retrofit underdeveloped urban right-of-way. The Plan to Protect Seattle's Waterways is a comprehensive strategy that embodies SPU's commitments that were documented in the July 2013 Consent Decree to address combined sewer overflows. It meets Seattle's federal commitments to create a Long-Term Control Plan (LTCP) that will make water quality improvements to Seattle's receiving waters, e.g., Puget Sound, Lake Washington, and the urban creeks that feed them. The final Plan received final approval in August 2015. Within the Plan to Protect Seattle's Waterways, SPU recommended the Integrated Plan (IP) alternative, which addresses water pollution from both combined sewer overflows and stormwater-only runoff into waterways. As part of the IP, SPU is committed to deliver high-value stormwater-only projects/programs ahead of a set of smaller-volume combined sewer overflow (CSO) projects for a greater overall water quality benefit. NDS Partnering is one of the three stormwater-only projects/programs recommended in the IP for pollutant reductions. In addition, the NDS Partnering program fits within SPU's Strategic Business Plan Focus Area No. 1, 'Better Protecting Your Health and Environment.' The mission of the NDS Partnering Program is to achieve the water quality goals identified in the City's Plan to Protect Seattle's Waterways. The NDS Partnering program emphasizes working with sister agencies, concurrent SPU programs and community partners to deliver high-value neighborhood improvements, including bioretention systems that will capture and treat stormwater before it drains to creeks feeding Puget Sound and Lake Washington. The purpose of the partnering in the NDS program is to develop shared projects within Seattle Public Utilities (SPU) programs and between SPU and other City agencies, such as Seattle Department of Transportation (SDOT), to offer multiple benefits to neighborhoods and ecosystems, including: greener, more attractive neighborhoods, lower risk of flooding, additional natural habitat for native plants and animal species, healthier creek ecosystems, calmer traffic patterns, and more street trees. For SPU, the NDS projects provide water quality treatment for street runoff that drains to urban creeks by retrofitting the roadsides with NDS (also referred to as bioretention cells) and addressing localized flooding issues. The City of Seattle has a long history in developing retrofits of right-of-way in urban creek basins beginning with the SEA Streets project in 1998. This presentation will focus on the current NDS program consisting of the Longfellow Creek Basin (due to be complete with construction in 2023), South Thornton Basin (due to begin construction in Spring 2023) and North Thornton and Pipers Creek Basins (under development and design). This program leverages innovations developed under some of the most recently constructed retrofit projects including the Delridge, Ballard (Phases 1 and 2) and Venema NDS projects to enhance the viability of green infrastructure in challenging site constraints and soils. These innovations include the use of weirs, underdrains, structural soil cells and underground injection control (UIC) wells. Working in underdeveloped or informally-drained right-of-way presents opportunities to address infrastructure gaps that will benefit the local community, specifically providing traffic calming, improving pedestrian access, and correcting nuisance drainage. This presentation will share the approach and response to community outreach to communicate impacts and receive feedback on tradeoffs on design of improvements. Additionally, the co-location of improvements with partner agencies presents opportunities to reduce overall project cost for the City balanced with increased coordination needs. Key issues addressed by the project include how to negotiate space constraints to co-locate new sidewalks with bioretention facilities in existing right-of-way. Another key issue commonly expressed by the community is minimizing impacts to automobile access and parking where historical use is informal and haphazard and existing driveways do not conform to code. Public investment in infrastructure presents the opportunity to improve community spaces and services. In addition to considering equity and deep connection with the community through the design process, the program also has had opportunities to incorporate art and create community spaces. This presentation will include examples where the projects have included a range of scale of art from small touches to enhance the individual elements of the green infrastructure to more significant efforts to incorporate public art in new pocket community spaces that are co-located and funded with the NDS projects. The project also specifically targets addressing local drainage issues where informal drainage is inadequate to collect and convey runoff from the neighborhood streets creating nuisance flooding. While addressing these local drainage issues is a significant benefit for the neighboring property owners, SPU was also challenged to incorporate NDS and drainage improvements in a manner to avoid conveying the additional runoff to create or aggravate existing issues downstream. The program addressed these challenges by evaluating the downstream system capacity, maximizing stormwater retention within the project and providing compensatory storage where required to minimized downstream impacts. In summary, this presentation will provide the opportunity to share lessons learned at a unique point in time that represents past, present and future of a program that is delivering green infrastructure improvements to over 60 blocks of neighborhood streets in the City of Seattle's urban creek watersheds. This program and presentation deliver unique and innovative techniques to balance the needs of the right-of-way to improve the quality of stormwater runoff. SPU strives for continual program improvement and delivering community-centered projects that achieve improved service with reduced costs.

King County's Wastewater Treatment Division (KC-WTD) standardized its dry media scrubber systems to utilize the horizontal airflow vertical bed (HAVB) configuration (Figure 1). This was done due to the relative ease the HAVB configuration provides for media removal and replacement relative to the traditional deep bed configurations and other designs. With almost thirty HAVB scrubbers in service and more than 18 years of experience with this configuration King County staff have refined their standard design based on lessons learned about scrubber vessel geometry, media bed retention system design, drainage, and maintenance access. KC-WTD staff have recently received reports from others in the wastewater industry that some utilities are still having difficulties with the operation of the HAVB configuration. The aforementioned lessons, design details and insights will be shared in this paper in the hope that others may benefit from KC-WTD's experience and avoid such difficulties. The HVAB circular cross section configuration allows spent media to be removed easily with a vacuum truck (Figure 2) and replaced easily by dropping replacement media in via large access hatches (Figure 3). However, if the media fill ports are not appropriately dimensioned with respect to the vessel diameter, gaps may form between the media and the vessel wall which will allow foul air to bypass the media and escape treatment which can lead to odor impacts. KC-WTD staff have developed, and will share in this paper, a simple means of avoiding the problem by comparing the fill port dimensions, vessel diameter media's angle of repose (Figures 4 and 5). KC-WTD has also encountered problems with media bed retention system failures, accessing the scrubber interior to perform routine maintenance and repair of internal scrubber features, drainage of condensate, media sampling port design and other issues that have caused difficulties both in the operation and maintenance of HAVB dry media scrubbers. The lessons learned from these problems have allowed the refinement of KC-WTD's HAVB design standard that operate successfully. It is hoped that by sharing these lessons and solutions that were developed will help others who choose to incorporate the HAVB dry media scrubber configuration into their odor control systems.

Mesophilic anaerobic digestion is the most deployed biological sludge stabilization process at wastewater treatment plants in North America. It also plays a central role in energy and resource recovery from wastewater treatment plants. This paper explores the application of medium vacuum pressure (~100 mbar) operated in a side stream recirculating reactor as a mechanism for process intensification and resource recovery, utilizing the IntensiCarbTM process. Currently within the industry the primary means of process intensification are either through the elevation of operating temperature (ex. thermophilic digestion), pre-conditioning of sludges (ex. thermal hydrolysis) or separation of solids and hydraulic retention time (ex. recuperative thickening). The IntensiCarbTM process utilizes the decoupling of SRT and HRT to increase process capacity while simultaneously reducing the influence of toxic metabolic by products through extraction (ex. ammonia-N). This paper discusses the results of side-by-side comparison of conventional mesophilic digestion with varying intensification factors (2x, 3x, 4x) for bench-scale trials conducted at Western University in London, Ontario, based on the process flow provided in Figure 1. The intent of this experimental design was to focus on understanding the fundamental process changes that occur when vacuum evaporation is applied to a conventional mesophilic digester. In particular, the question being investigated is whether the evaporation process and the extraction of materials result in any fundamental changes in the operation of the digestion process or does it simply operate in a manner similar to recuperative thickening. Table 1 provides a summary of the operating conditions tested, with Intensification Factor 1 (IF1) representing the control and IF2, 3 and 4 representing varying degrees of decoupling of both SRT and HRT. All the digesters were fed a mix of primary and secondary sludge (Ave. TS = 2.9%, VS =2.18%) periodically collected from the Greenway Wastewater Treatment Plant in London, Ontario. The digesters were all operated at mesophilic temperatures (~35-37 °C). Across the range of intensification factors tested, in general, all processes demonstrated effective anaerobic digestion of the sludge, noting that the highest intensification factor (IF-4) there were episodic instability events (data not shown). This suggests that either the process is approaching its maximum extent of intensification, or the specific combination of HRT and SRT is not sustainable. A number of factors could be causing this observed instability including insufficient active fraction of biomass at the extended SRT, the biomass population is at an inflection point with shifting populations or an undefined stressor is impacting the population. Additional research will be required to explore the ultimate limits of intensification. What is apparent from the data in Table 1 is that in general IntensiCarbTM does not appear to significantly change the extent of digestion with the VSr ranging from 46-55 percent relative to the control at 50 percent. However, the rate of digestion is significantly enhanced by the increase in solids concentration, resulting in overall higher solids throughput rate and rate of methane generation increasing from 0.29 m3-CH4/m3-digester-day to a maximum of 1.08 m3-CH4/m3-digester-day (Figure 2). A challenge with most process intensification strategies deployed to date is the impact of metabolic byproducts on the process. Of particular interest is ammonia, as it is produced through the decomposition of proteins, which constitute a significant fraction of sludge materials. To date no technology has effectively managed ammonia-N in-situ, resulting in risks for process instability and or significant population shifts, as reported by Mah et al. (2017) for THP. The concentration of ammonia in digesters tested were very similar (Table 1). This is significant in that the control of ammonia in the digester could support high loadings without the negative impacts. Figure 3 simulates what solids concentrations sludge would need to be loaded at to a conventional digester to achieve the same degree of intensification and the resulting total ammonium concentration in the digester would be. What is apparent from the graph is that conditions similar to those observed in thermal hydrolysis would need to be achieved, but the resulting total ammonia concentrations would approach the current limits of those systems. Furthermore, the feed solids would need treatment to reduce the viscosity to make the material pumpable. Figure 4, presents the nitrogen balanced conducted across each system, showing significant removal of ammonium-N to the condensate of the evaporator from the digestate. Supporting the observation that the IntensiCarbTM process creates a unique condition where the negative impacts of ammonia can be directly controlled in a highly loaded digestion process. Furthermore, the condensate is a very clean liquid, devoid of solids making it an ideal solution for ammonia recovery and beneficial use; potentially eliminating the need for centrate treatment for nitrogen. The combination of reduced nitrogen load and stable operations suggest the peak capacity of the IntensiCarbTM process was not achieved, in these tests. Plotting the empirically derived peak loading conditions for common stabilization processes and the resulting average total solids load, at a volatile fraction of sludge equivalent to the one used in this study, it is possible to investigate potential peak loadings; assuming similar process limitations of peer processes. The IntensicarbTM process, as currently tested, would appear to have a similar capacity to thermophilic digestion (Figure 5) for loading. However, at the highest average loading condition, IF-3, no process instability was observed, suggesting further intensification could be possible and should be investigated. Overall, the IntensiCarbTM, based digestion process is early in development but is demonstrating promise and the novel application of vacuum is generating conditions within digesters that have not been evaluated to date. The combination of process intensification through decoupling SRT and HRT and the depression of ammonia-N concentrations would suggest the system may achieve further enhancement as optimal operating conditions are defined. Concurrent with the completion of these bench trials a pilot facility is being planned by the Great Lakes Water Authority to further vet this process. This pilot will investigate the scalability of the technology, introduce of real-world operating dynamics, further optimize operating conditions to define a design loading criterion and develop a techno-economic analysis. Vacuum enhanced anaerobic digestion represents a novel process for the intensification of anaerobic sludge stabilization. Potentially offering unique opportunities for resource recover, ammonia-N and dissolved methane, as well as providing a mechanism to alleviate the current limitations associated with anaerobic digestion, metabolic byproduct toxicity. If successful, this technology could provide the next step forward in resource recovery from sludges.

Introduction: Anaerobic digestion is a proven technology to stabilize solids from water resource recovery facilities (WRRFs) and produce biogas. Enhancing anaerobic digestion would increase the volatile solids reduction (VSR), biogas production, and reduce the residual biosolids. The objective of this research was to explore how much the VSR could be increased in digestion with the addition of new technology: Microbial Hydrolysis Process (MHP). Typically, a well-performing anaerobic digester can achieve 55 percent VSR when fed a combination of primary and secondary sludge from a WRRF. High-performing digestion systems can achieve 60 percent VSR or higher, but none (until now) have achieved over 70 percent VSR. Jacobs with professors at Brigham Young University (Hansen, Jaron C., et al., Biofuel Research Journal Vol. 8 Issue 3 2021), developed the Microbial Hydrolysis Process using Caldicellulosiruptor bescii (C. bescii), a hyper-thermophilic bacterium that enhances the performance of any anaerobic digestion process. The MHP digestion process flow diagram is shown in Figure 1. The C. bescii bacterium and associated enzymes hydrolyze cellulose and other recalcitrant volatile solids that are otherwise resistant to digestion into volatile acids. These hydrolyzed volatile solids are fed to an anaerobic digester where methanogens convert them into biogas. One configuration of MHP feeds digestate from an anaerobic digester to a hydrolysis tank populated with C. bescii for a hydraulic retention time of at least 2 days at 75 degrees C. The hydrolyzed digestate is then returned to the digester to complete the digestion process by converting volatile acids into methane and carbon dioxide. MHP is compatible with any anaerobic digestion process including mesophilic anaerobic digestion (MAD), thermophilic anaerobic digestion (TAD), and thermal hydrolysis process (THP). The increase in VSR results in corresponding increases in biogas production and reductions in residual biosolids. The value of the additional biogas and cost savings of producing less biosolids reduce the operating costs of a WRRF. Methodology: The performance of anaerobic digestion with MHP was tested at lab-scale and pilot-scale systems on solids from three different WRRFs: City of Gresham Wastewater Treatment Plant in Gresham, OR with MAD and fats, oils, and grease (FOG) addition; Encina Water Pollution Control Facility (WPCF) in Carlsbad, CA with MAD; and Oakland County's Clinton River WRRF in Pontiac, MI with THP and MAD. The lab-scale system consisted of a test and control system: each with a 10 Liter (L) digester and a 5L hydrolysis tank. Figure 2 is a picture of the MHP digestion lab-scale system and Figure 3 is a process flow diagram of the system. The pilot-scale system consisted of a test system with a 1,200L digester and a 500L hydrolysis tank and a control system with a 1,200L digester. Figure 4 is a picture of the pilot-scale MHP digestion system and Figure 5 is a process flow diagram of the system. All tanks were mixed, heated, and automatically fed from digester feed tanks. The test and control systems were operated to simulate the full-scale digester operation for feed, retention time, and transfer rate between the digester and hydrolysis tank. Characteristics of the feed and contents of the digesters and hydrolysis tanks were measured using standard methods. The stability of the digestion process was monitored measuring Volatile Fatty Acids, Alkalinity, and Ammonia. The VSR of the digesters was the key indicator of performance and was determined from the TS and VS fed to the digesters compared to the TS and VS withdrawn from the digesters. Lab-scale tests for Gresham and Encina were conducted in the Gresham lab. Pilot-scale tests for Oakland County were conducted in the Clinton River WRRF lab. Labs at each WRRF were used to measure the characteristics of the feed and performance of the full-scale digesters. Findings: The digestion performance of the three WRRFs are indicated by the VSR. Results from lab-scale, and pilot-scale digestion systems have demonstrated significant increases in VSR compared to already high-performing digestion systems (e.g., THP and MAD). VSRs were observed to increase from 60 percent without MHP to greater than 75 percent with the addition of MHP. Figures 6-8 show the VSR results of the test and control systems compare to the full-scale systems. In all cases the MHP increased the VSR from current operation of 58-60 percent to over 75 percent VSR. Results were used to calibrate a process model (Sumo) to predict digestion performance for full scale facilities with different feed characteristics. Based on the results, conceptual designs were prepared for implementation at three WRRFs with three different technologies: MAD, TAD, and THP and MAD. The details of these designs are being reviewed by each utility and can be presented in the full paper. Significance: The significance of the research and development of MHP is the discovery of a new technology that enhances the performance of anaerobic digestion to the highest level achievable to date. Anaerobic digestion performance increased with the addition of MHP in tests on three different WRRFs. MHP increased the VSR from 60 percent to over 75 percent. The increase in VSR corresponded to a 25% increase in biogas production and a 25% decrease in biosolids production.

Introduction
Our urban centers are plagued by a variety of concrete storm water conveyance structures. Originally intended for flood control, they have simply moved the flooding to downstream areas while degrading natural stream habitat. It's well documented that nature-based solutions mitigate stream habitat degradation, but can they also perform a vital flood risk reduction purpose in our urbanized neighborhoods?

General Project Information
As part of a larger master plan for the Springfield Art Museum, Fassnight Creek was restored to a naturalized channel for flood mitigation, water quality, and wildlife habitat improvement. The Springfield Art Museum is located in the heart of Springfield, just south of Missouri State University. Adjacent to the museum is the historic Phelps Grove Park which is beloved by the community for its mature trees and pedestrian trails. The museum and Phelps Grove Park are surrounded by well-established residential neighborhoods and a high-level of pedestrian activity, which made this project an impactful addition to the urban greenspaces in the area. Before the capital improvement project, Fassnight Creek was confined in a narrow concrete channel with insufficient hydraulic conveyance. The Fassnight Creek Improvements widened the channel cross section significantly and naturalized approximately 1,000 linear feet of creek channel, encompassing 1.5 acres of newly re-stablished riparian area, that serves as an urban wildlife corridor and extension of the Phelps Grove Park greenspace. The restored channel contributes to the overall quality of place and helps to further integrate Phelps Grove and the Art Museum grounds. Key components of the natural channel design include use of void-filled native rock materials to emulate the natural stream bottom of local streams and extensive native plants. Construction included excavation of approximately 16,000 CY of soils, removal of 900 feet of concrete channel lining, removal of a public street crossing, installation of over 250 linear feet of 21-inch sanitary sewer main, two new pedestrian bridges, creating a natural pool and riffle stream, mitigating culvert erosion and re-alignment and narrowing of Brookside Drive centerline to give additional area for channel improvements. Channel Naturalization Details Native plantings provide multiple benefits including creation of habitat to support pollinators, aquatic species, and other wildlife. The native landscaping included planting of over 25 native trees and over 200 native shrubs. Missouri native plantings obtained from regional sources. In addition, City urban forestry crews carefully excavated and rehabilitated a small sycamore tree known to the local residents as the 'child sycamore' and this tree was successfully re-planted in the center of the creek corridor after the grading was completed. The plantings are integral to the project's goals to improve water quality and reduce flooding through filtration and uptake of common pollutants and absorption of stormwater runoff. The project also will increase awareness and acceptance of native plants due to its visibility by local and regional Art Museum visitors. The project will also enhance the Art Museum as a local field trip destination for Science, Technology, Art & Math (STEAM) programs. The Art Museum currently partners with the non-profit Watershed Committee of the Ozarks on the Placeworks STEAM Residency that uses journaling to connect science and art and includes field trips to the Art Museum. There is also a desire for the Art Museum to serve as a monarch way station to tie in with butterfly habitat efforts at the Botanical Center on the south side of Springfield. On this project, the channel slope and shear stress exceed a fine grain channel bottom or a fully vegetated solution which is likely why a concrete liner was used in the past. Fortunately, many local streams are predominately bedrock influenced gravel bed streams. We were able to mimic the natural stream bottom utilizing void-filled rock. Void-filled rock mimics local natural stream bottom where native graded cobbles, boulders, and small aggregates are mixed form a densely packed heterogeneous mixture. For the Fassnight Creek restoration project, the concrete was removed and the rock mixture used to create a stable natural channel bottom. The engineered mixture of stones and smaller sized river gravel aggregates compacted in layers ranging from approximately 2 to 4 feet thick. Selected areas of the void-filled riprap are planted with native grass plugs to add aquatic habitat value but also reinforce overbank areas of the channel with rooted plantings. Void-filled stone structures have been placed along the channel alignment to form riffles and pools seen natural streams alignments. These pools and riffles are the foundations for aquatic habitat in the creek.

Floodplain Information
A central project objective was to reduce base flood elevation (BFE) and mitigate flood risk for the Springfield Art Museum and surrounding residential properties in this area. Based on revised, preliminary 2019 FEMA maps, portions of the Springfield Art Museum and surrounding residential properties are within the 1% and 0.2% SFHA. Flood Insurance Rate Maps (FIRMs) and Flood Insurance Study (FIS) for Springfield are currently being updated to provide more accurate depiction of flood risk for the community but have not yet been formally adopted at this time. The City of Springfield's proactive approach now has the Art Museum and residential properties well positioned for the formal adoption of the revised preliminary FEMA floodplain maps. The improvements lowered the 1% BFE approximately feet. Following the Improvements to Fassnight Creek at the Springfield Art Museum, the surrounded properties finished floor elevations have a much lower flood inundation residual risk. Construction and Funding Fassnight Creek at the Springfield Art Museum was substantially completed May 31, 2022. The construction began in Spring 2021 and took slightly longer than 1 year to complete. Construction involved complicated sanitary by-pass pump around for sanitary sewer main relocations, and constant vigilance on the part of the general contractor to maintain erosion and sediment control best management practices during active construction within the creek. Following construction, the ribbon cutting grand opening occurred October 15, 2022 with the Mayor, City Administrator, three Councilmen, the Art Museum director and the Art Museum board of directors presiding. Fassnight was recently recognized as an APWA Missouri Chapter Public Works Project of the Year because it demonstrated a functional solution to flood risk reduction which can serve many other beneficial purposes for the community. The naturalized channel is the new grand entrance to the Museum, an inspirational functional piece of living art. The overall construction costs for the project were approximately $2.3 Million. The Project was partially funded by grant funding from the Missouri Department of Natural Resources, EPA Section 319 grant funding Administered by the non-profit James River Basin Partnership, and grant funding for native plantings from the Missouri Department of Conservation. The local funding share was provided by the City's ¼ cent capital improvement sales tax.

Faced with increasing costs for controlling hydrogen sulfide in its wastewater collection system, the City of Bakersfield, California commissioned an evaluation of its odor control program in 2019. Among the consultant recommendations was to consider using a more efficient treatment (ferrous chloride) in place of certain of the existing Calcium Nitrate dosing stations where costs were constrained. A particular priority were those stations along the higher flow interceptor segment where chemical demands and community sensitivities were highest. An expected benefit of iron dosing is its durational control capability, which should translate into fewer dosing stations. Consequently, field testing was suggested to assess the cost-benefit. As siting dosing stations for ferrous chloride solutions can be limited (due to the corrosivity of the product), a low-hazard form of ferrous chloride, SulFeLox®, was used. The study was conducted from April to June, 2021, and consisted of 12 days monitoring of the baseline Calcium Nitrate scenario, followed by 60 days of SulFeLox dosing at different feed rates, and concluding with 14 days of no chemical dosing (i.e., the true baseline scenario). The interceptor selected for the test was a 10-mile (5-6 hour retention), 12 mgd trunkline leading to the City's Plant No. 3 (Figure 1). The particular segment of focus begins where the discharge from the Romero PS (S1) enters the interceptor and ends at the Buena Vista PS (S2) approximately 3 miles (2 hours) downstream. Controlling vapor-H2S levels at the Buena Vista PS was the primary measure of success. To assess the durational control aspects of each chemical, sampling was also performed another 3-4 miles downstream at the McCutcheon PS (S3) - just ahead of the treatment plant (S4). In this study, the SulFeLox dosing station replaced two Calcium Nitrate stations: 1) at the Romero site (S1), and 2) at the Buena Vista site (S2). With Calcium Nitrate dosing (310 gpd, combined, from the two sites), the peak vapor-H2S levels recorded at the four sampling sites averaged 3, 94, 595, and 100 ppm (Figure 2a). The liquid-phase sulfide levels were 0.0, 2.9, 6.6, and 3.5 mg/L, respectively. With SulFeLox dosing (120-210 gpd), the peak vapor-H2S levels recorded at the four sampling sites averaged 0, 30, 652, and 31 ppm (Figure 2b). The liquid-phase sulfide levels were 0.0, 1.4, 4.7, and 2.3 mg/L, respectively. Comparing the Calcium Nitrate and SulFeLox results shows 66-83% lower vapor-H2S peaks at the Buena Vista (S2) and treatment plant (S4) sites, with less benefit at the McCutcheon site (S3) where vapors are impacted by H2S by other flows into the station. (Figure 2c). Site 2 (Buena Vista PS) is located in a particularly sensitive area, and prior tests suggested upstream Calcium Nitrate feed rates would need to be 500 gpd (or more) to maintain vapor-H2S levels below 25 ppm. Figure 3 shows the vapor-H2S results in this test, where SulFeLox feed rates of 120-210 gpd achieved the compliance targets and provided H2S reductions of 84-95% (relative to 146 gpd Calcium Nitrate). On a performance basis, the field results confirmed the consultant recommendation that (for system-wide H2S control) iron dosing from one site could provide improved results relative to Calcium Nitrate dosing from two sites. SulFeLox feed rates were determined that provide interceptor-wide H2S control to 25 ppm and 10 ppm. However, a direct cost comparison between the two treatment chemistries is complicated given that system-wide H2S control could not be demonstrated with Calcium Nitrate (per the 500 gpd test in a prior study). This present study did show, however, that the cost to control to target H2S levels using SulFeLox was $600-1000 per day, where the recurring cost for Calcium Nitrate was $850-950 per day (to control to the higher level of 100-140 ppm H2S). Subsequent to this field test, the City continued to feed SulFeLox at S1 (Romero PS) and has since replaced seven other Calcium Nitrate sites with three SulFeLox sites, reducing the total number of chemical feed sites from nine to four. As a result of this work, the City is now spending approximately $660 k/yr for SulFeLox to meet its system-wide performance targets, where it was previously spending $990 k/yr (for Calcium Nitrate). Further, with now a year's experience with dosing iron into the collection system, the treatment plant has observed operational benefits, including the elimination of need for ferric chloride feed to the plant digesters. Early in 2022, the City entered into a five-year supply agreement for providing SulFeLox iron product and related services and equipment. Future work is planned to evaluate iron regeneration ahead of the treatment plant (at McCutcheon PS, S3), recognizing that this trunkline comprises 70% of total plant flow but 100% of influent iron. Oxidizing the spent iron (as FeS) to hydrous ferric oxide (using hydrogen peroxide) is expected to provide additional benefit to treatment plant operations. Figures 1. Schematic of interceptor segment tested 2. Summary of field test results: Calcium Nitrate and SulFeLox rate performance 3. Buena Vista PS: Response of vapor-H2S levels to chemical feed rates (at the upstream Romero PS). 4. Buena Vista PS: Dose-Response summary comparison of SulFeLox to Calcium Nitrate.

Speakers: Karen Counes Program and Construction Management Practice Leader CDM SMITH Jenn Harrison Regional Team Leader, Program and Construction Management CDM SMITH Julie Lucas Senior Manager of Talent Acquisition Programs CDM SMITH Sara Varvarigos, Transportation Planner and Reboot/Re-entry Graduate CDM SMITH Category: Diversity & Inclusion - Presentation title: Reboot Re-entry: Returning to a Technical Profession After a Career Detour - Description: Two steps forward, two steps back. Sometimes detours happen in our well-planned lives. If you have had a break in your science, technology, engineering, and mathematics (STEM) career and are now ready to get back in the game, let CDM Smith help you restart your career by participating in our career re-entry program. In partnership with the Society of Women Engineers and iRelaunch, we offer a 16-week program each January through April for those who left their STEM career for 2+ years and now want to return. This is a paid, full-time temporary opportunity to help you train and rejoin peers in your field. Abstract/Content In 2018, CDM Smith joined a task force with the Society of Women Engineers (SWE) and iRelaunch, a pioneering organization on career return-to-workspace and essentially 'returnships' intended to re-integrate technical professionals into the workplace after career detours. SWE's STEM Reentry Task Force and iRelaunch's research and training programs were the basis for CDM Smith's Reboot/Re-entry Program, a 16-week, 40 hrs/week paid 'returnship' geared toward those employees trained in technical professions such as engineering and construction, but had taken a hiatus in their professional career. CDM Smith's formal Reboot/Re-entry program began in 2019, and can now claim 6 full-time hires as a result of the program.

ABSTRACT
City of Los Angeles Sanitation and Environment (LASAN) owns and maintains 10,800 kilometers (6,700 miles) of sewer and operates three Air Treatment Facilities (ATF) and ten Carbon Odor adsorbers located along the sewer system for removing odor and other related constituents from the collection system. The ATFs utilize Bio-trickling Filters (BTFs) technology followed by carbon adsorbers as polishing units while the Carbon scrubber sites utilize carbon adsorbers as the only treatment for foul air. In order to improve carbon life and reduce the footprint required for carbon vessels, LASAN started conducting a series of pilot tests to evaluate alternate carbon odor adsorbers with suspended media for all-around air flow compared with traditional flow carbon design. The results of this test were published in Water Environment Federation (WEF) Odor Conference in 2018 (Haddad-Zadegan/Gilani, WEF Odor Conference 2018 and UCLA Odor Conference 2017). The purpose of this test was to evaluate the performance of the new carbon vessel design with Suspended Media Chamber (SMC) and all-around air flow which provides larger media surface area, smaller footprint, and capability to separate moisture from the inlet air stream. This testing project conducted a side-by-side comparison between a deep bed traditional vertical upward air flow and the new all-around air flow design. LASAN procured and installed the new vessel design at eight (8) City carbon scrubber sites and this paper will share the result of the new scrubbers in term of their capability on removal of Hydrogen Sulfide (H2S) and other odorous compounds Volatile Organic Compounds (VOCs) from the inlet air stream. The new vessel design has the capability to separate the water voper from the inlet air stream contributing to a longer carbon life expectancy which results in significant cost savings for LASAN.

In response to flooding that occurred in August 2018, the City of Madison responded by initiating a comprehensive watershed planning program. Prior to this a number of large rainfall events had occurred in the City and caused flooding in various area. The tipping point for the City was reach on August 20, 2018, when an extreme storm event that was in excess of the 1,000-year storm event occurred and resulted in flash flooding and lake-level flooding within the City. A USGS rain gage recorded in excess of 10-inches of rain in under 12-hours. Precipitation amounts of up to 15-inches were estimated. The Atlas 14, 1000-year, 24-hour rainfall event for the area is 8.92-inches. The purpose of this project is to describe how one community moved forward from an extreme event and developed a watershed study program to become more resilient to future events. The Waite Circle area of Madison was particularly hard-hit by flooding, and as a result, was studied as part of the Wingra West Watershed Study as one of four initial projects undertaken. A detailed one-dimensional and two-dimensional hydrologic and hydraulic model was developed for the watershed to evaluate the existing stormwater conveyance system. The model was calibrated to monitored storm events and validated compared to historical observations from the August 20, 2018 event (see Figure 1). The model output was used to prepare flood inundation mapping that could be shared with the public and various stakeholders to help understand flood risks throughout the watershed under various storm events. The study considered various flood mitigation solutions including dispersed green infrastructure at varying levels of implementation (see Figure 2). Gray infrastructure that was considered included local storm sewer improvements, new relief sewers, new detention basins, improvements to existing detention basins, and culvert improvements. Ultimately a suite of measures, including improvements to five existing detention basins, enlargement of a culvert, construction of two relief sewers, and numerous local storm sewer improvements was selected to meet the City's flood mitigation goals for 10-, 25-, and 100-year storm events (see Figure 3). The project included three public information meetings and more than ten focus group meetings. The study began in 2019 and was ultimately completed in 2022. This presentation will provide information regarding the severity of flooding and the development of the City's watershed study program which included a hydrologic and hydraulic modeling guidance document and establishment of a stormwater system monitoring program. The Wingra West Watershed Study will be presented as a case study to show how model development and calibration occurred, how flood mitigation solutions were evaluated and selected, and how public participation was incorporated into the study process. The presentation will also include how the study phase was then transitioned into an implementation phase. One result of the flood response was a fast-track emergency culvert improvement project that was designed and constructed in less than 9 months to mitigate flooding in the Waite Circle area. This project was undertaken during the development of the overall watershed study and added a layer of complexity to the study. Project design began in May 2019 and construction was completed in December 2019. This compressed project time-frame required an expedited material procurement process and complex construction scheduling to achieve the required project completion date. The original culvert had failed, and an initial stop-gap repair had reduced the culvert capacity and contributed to the severity of flooding. A solution to this problem was needed prior than the schedule for the full study allowed. The improvement project enlarged the culvert to restore the original capacity, as well as allow for flow to be increased through the culvert in the future to further mitigate flooding. This was accomplished by designing the culvert to fully pass the 100-year storm event. Restriction plates were then installed to reduce flows until the downstream system capacity is improved such that higher flows can be safely handled. Additional complexities of the project included a small project site with numerous utility conflicts, limited site access, steep slopes, and challenging site restoration. In particular, a sanitary sewer interceptor sewer needed to be relocated from being located directly under the culvert. The relocation allowed for future maintenance and reduction of inflow and infiltration (see Figure 4). The presentation will conclude with a summary of the current status of the City's watershed study program and next steps for the program. It will also provide lessons learned and how the program has evolved to better serve the City. The Wingra West watershed study has been described by City Staff as one of the 'guinea pigs' of the program. Sharing the lessons learned from this study will allow others to improve their own stormwater programs and become more resilient to large rainfall events. By attending this session, participants will be better able to: 1.Describe challenges associated with flooding and flood mitigation in an urban watershed. 2.Recognize the importance of having a strong public outreach and communication program with various stakeholders for planning and implementation. 3.Understand the benefits and limitations of both gray and green infrastructure to mitigate flooding from large storm events.

INTRODUCTION The Metropolitan St. Louis Sewer District (MSD) is undertaking a long-term program called 'MSD Project Clear' to improve water quality for the St. Louis region by reducing the occurrence of basement backups and overflows caused by excessive wet weather sanitary and combined sewage flows. One of the approaches MSD is taking to meet this goal is constructing new infrastructure to increase the capacity of their existing sewer collection system, including new relief sewers, wet weather storage facilities, and tunnels to store and transport wet weather sanitary and combined sewer flows. This presentation will describe how wet weather storage technology was applied to attenuate excess flows and eliminate wet weather sanitary sewer overflows (SSOs) and backups in a portion of MSD's collection system. This approach has been used elsewhere in MSD's system and has potential application to other similar wastewater systems through the United States. PROJECT BACKGROUND In 2014, MSD, in association with engineering consultants Burns & McDonnell Engineering Company, Inc. and Wade Trim, Inc. began planning the Gravois Trunk Sanitary Storage Facility in Crestwood, Missouri. This facility is located along the 54-inch diameter Gravois Trunk Sewer, within the Gravois Creek watershed and the sanitary sewer service area of MSD's Lemay Wastewater Treatment Facility. Multiple sites were reviewed for location of the storage tank(s) based on a series of criteria, including operational flexibility, land needed and availability, location within the watershed and ability to meet hydraulic and flow reduction requirements, maintainability, reliability, operability, constructability, and environmental considerations. All sites evaluated were required to accommodate the preliminary storage requirement of 9.25 million gallons (MG). The site of an existing City of Crestwood public works maintenance facility was selected, which is located on Pardee Lane adjacent to the Gravois Trunk Sewer and Gravois Creek. HYDRAULIC MODELING Hydraulic modeling evaluations were performed to assess the capability of the facility to achieve two (2) goals: 1) the removal of two (2) Constructed Sanitary Sewer Overflow (SSO) Outfalls; and 2) limiting the hydraulic grade line (HGL) within the Gravois Trunk Sewer to a minimum of 8 feet below grade for a 10-year return period, except in areas where the sewer is less than 8 feet deep or in areas where basements will not be impacted. Meeting these goals will provide a 10-year Level of Service (LOS) for the Gravois Trunk Sewer. A calibrated XPSWMM model of the Gravois Creek watershed was used to verify that the required 10-year LOS is being provided for three different conditions, including for the 10-year 24-hour synoptic and 10-year 3-hour cloudburst design storms, as well as for a continuous simulation using 64 years of historical rainfall data to evaluate the long-term performance using real rainfall events. The 3-hour cloudburst event represents a high-intensity lower volume rainfall event, in comparison to the lower intensity, higher volume 24-hour synoptic rainfall event. The required storage volume to provide the 10-year LOS was determined using two methods: 1) Log Person method to determine probability of recurrence of exceeding required volume, and 2) meeting HGL limitation criteria for the downstream trunk sewer. The model was also run for the full rainfall data for the years 2000 and 2008 ('Typical' and 'Wettest' years, respectively) to evaluate the expected frequency that the storage facility would be in operation. Final design sizing concluded that the following minimum storage volumes would be required to provide a 10-year LOS: Synoptic: 7.97-MG; Cloudburst: 4-MG, and Continuous Simulations: 7.85-MG. Based on these results, a total storage volume of 8.0-MG was used for design. Modeling efforts also included development of a HEC RAS model to evaluate hydraulic conditions in the sewer downstream of the diversion structure for the purpose of optimally locating level measurement instrumentation to be used in process control of the facility. DESIGN CONFIGURATION Due to the site configuration, two (2) sanitary storage tanks with a storage volume of 4.0-MG each were planned rather than a single 8-0-MG storage tank. Above-ground storage tanks were designed using the AWWA D-110 Type III standard for Wire- and Strand-Wound, Circular, Prestressed Concrete Water Tanks. Tanks are 150-feet in interior diameter, with a maximum height above ground of 45-feet, in compliance with local ordinance. Tank floors are sloped to the center at a depth of approximately 8 feet below grade, and drained by gravity back to the trunk sewer. An aesthetics committee comprised of representatives of MSD, the design team, and public stakeholders was convened during design for the purpose of soliciting feedback on such features as tank façade, landscaping, and fencing. Other facility features included: - Non-staffed and fully automated - Diversion structure - Consolidation sewers - 54-MGD influent submersible pumping station - Granular activated carbon odor control system - Vertical turbine pumping system and rainwater harvesting system - Tank and wet well cleaning systems - Gravity dewatering sewers and control valves - Site paving, lighting, and landscaping including stormwater BMPs - Instrumentation and controls - SCADA system for centralized remote control - Control Building - Electrical Primary and Secondary Power - Miscellaneous Improvements POST-DESIGN ASSESSMENT Design was completed in 2018, and a construction contract in the amount of approximately $24 Million was awarded, after competitive bidding with four responsive bids received, to Plocher Construction Co. Inc. of Highland, Illinois. Construction began in 2019 and was completed in 2021. The Gravois Trunk Sanitary Storage Facility has been in successful operation by MSD since January 2021. CONCLUSIONS - AWWA D-110 tanks provide cost-effective above-ground storage - Above-ground wet weather sanitary storage requires extensive public outreach - Hydraulic analysis needs to consider future pipe lining, as well as potential for rapidly varied flow and/or backwater conditions in locations used for flow or level measurement - Need to build flexibility and operational feedback into facility design and process flow control strategies Refer to Picture 1 below for an aerial photo taken of the completed facility.

APPLICABILITY Optimized mixing improves digestion stability and increases digestion capacity. Our objectives were to evaluate nine mixing technologies for installation on existing digesters at a California WRRF, determine what retrofit modifications would be required and associated costs, and ultimately select a mixing technology for the digesters. Understanding available mixing options for existing digesters and how to evaluate them in a manner that defines retrofit requirements allows for better feasibility assessment and cost estimates than typical evaluations. DEMONSTRATED RESULTS/CONCLUSIONS Introduction The mixing systems for two existing digesters at a California WRRF were the gas lift 'eductor tube' type system which have been working well for the plant since initial installation. However, the utility wanted to determine if changing to a different mixing technology could reduce energy consumption while maintaining good digestion and the costs to implement such a change. Nine mixing technologies were considered in a phased evaluation that began with a technology screening/initial cost comparison to identify the three most beneficial options for the utility followed by a detailed structural analysis to finetune understanding of retrofit requirements and overall costs for those three options. The digesters are prestressed concrete tanks with column-supported concrete covers, so the tanks have unique structural constraints relative to retrofitting. Therefore, a finite element analysis (FEA) was performed on the three screened technologies to better assess feasibility, understand the extent of structural modifications required for installation, and the costs to implement the mixing system at the WRRF. Nine mixing technologies were considered in a phased evaluation that began with a technology screening/initial cost comparison to identify the three most beneficial options for the utility followed by a detailed structural analysis to finetune understanding of retrofit requirements and overall costs for those three options. The digesters are prestressed concrete tanks with column-supported concrete covers, so the tanks have unique structural constraints relative to retrofitting. Therefore, a finite element analysis (FEA) was performed on the three screened technologies to better assess feasibility, understand the extent of structural modifications required for installation, and the costs to implement the mixing system at the WRRF. Methodology The nine technologies and associated representative system manufacturers that were considered for the initial screening and cost comparison are listed below: Gas Recirculation: - Lance type (manufacturer supporting technology not identified/responsive). - Bottom mounted diffusers (Enviromix). - Gas lift 'Eductor Tube' (Walker Process). - Gas piston 'Bubble Gun' (Suez/Veolia). Mechanical: - Submersible high solids axial impeller mixers (Anaergia). - Vertical shaft agitators (Philadelphia Mixing Solutions). - Linear motion (LM) mixing (Ovivo). - Hydraulic draft tubes - externally mounted and roof mounted (Ovivo). Hydraulic: - Pumped mixing systems (Vaughan). Equipment proposals solicited from the vendors included the recommended number of mixing units for each digester, system layout, cut sheets, motor sizes, ancillary equipment needed, installation lists, and costs. Screening level evaluation criteria included the following factors: —Economic o Conceptual Level Capital Costs o Operation & Maintenance Costs o 20-Year Life Cycle Costs — Non-Economic: o Footprint o Performance o Number of installations o Operating history o Retrofit requirements and feasibility o Constructability o O&M requirements o Sensitivity to debris o Suitability for co-digestion o Position relative to industry trends Based on the initial evaluation, the following systems were deemed infeasible: lance type gas mixing due to outdated technology and externally mounted hydraulic draft tubes and pumped mixing systems due to large penetrations required in the pre-stressed digester walls. The remaining technologies were then considered relative to the non-economic criteria, capital costs, and life cycle costs. The cost estimates at this stage of the evaluation were high level and included base assumptions regarding retrofit requirements for implementation. From that analysis, four more technologies were screened out due to high life cycle cost. The three remaining technologies included: gas lift mixers (similar to existing), submersible axial impellers, and LM mixers. Advantages, disadvantages, and the initial 20-year life cycle cost for each of these three technologies following the screening level evaluation are displayed in Table 1. The cost for the gas lift system assumed replacement in-kind of existing eductor tubes but maintaining existing compressors which remain in good condition. Each of these remaining technologies involve elements that are fully or partially roof-mounted. The axial impeller and LM mixer technologies would impart new static and dynamic loads on the roof structure and the axial impellers would require new, large openings to be cut into the roofs. Furthermore, while the axial impellers can be supported off the walls and floor, the LM mixers are usually supported entirely by the roof. Both digesters have column-supported concrete roofs with heavy rebar reinforcement along the column line grid as indicated in yellow and green in Figure 1. Equipment installed in the blue areas of the figure would be most feasible. However, additional structural analysis was necessary to truly assess impacts for the axial impellers and LM mixers and their associated static and dynamic loads. To understand and fully vet feasibility and implementation cost of these technologies, FEA was performed for both digesters. In addition, the vendor-recommended number of axial impellers was lower for each digester than on other studies for similar applications. The vendor reassessed their recommendation, adding one more mixer on each tank. The technology evaluation and cost estimates were then updated with the more refined assessment of structural and electrical impacts and equipment proposals. Results An example of the FEA results for the LM mixer for both digesters is shown in Figure 2. These results showed that the loads imparted by this mixing system, would require significant structural upgrades including additional bracing and concrete beams between columns. The FEA for the axial impeller option indicated a need for additional reinforcement at new roof openings, but no more significant modifications. However, with the increased mixing units, this technology's capital and power costs increased. Previously assumed modifications were found to be unnecessary for the gas lift option, reducing the technology's capital costs. After updating the cost estimates, the previous initial results changed, making gas lift mixing the most economical option. Table 2 shows the final life cycle cost estimates for the three technologies. Conclusions The phased evaluation with detailed structural assessment confirmed that the existing gas lift technology is the best option for this utility even though it consumes higher power than other options. Results for other WRRFs with differently constructed digesters, power costs, or drivers for change may vary. Investigating the potential impacts on existing digesters from changing technologies can yield different conclusions than typical evaluations that stop at the initial step described above. CONSEQUENCES Our results show that technology evaluation requires thorough vetting and consideration of impacts on existing tanks. The mechanical, electrical, and structural requirements for implementation should be investigated to thoroughly assess option feasibility and cost. Furthermore, energy savings alone may not warrant change if the existing system is effective and well-functioning. RELEVANCE To reduce costs and improve performance, WRRFs are focused on optimization and fully leveraging existing infrastructure. While newer, efficient technologies are promising, thoroughly evaluating options against a utility's specific drivers and investigating the impacts of various technologies on existing infrastructure is essential to defensible decision-making. There is no one-size-fits-all solution.