Conference Papers

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.

Variations in Green Infrastructure (GI) Low Impact Development (LID) Best Management Practices (BMPs) within the right-of-way have resulted in problems with construction, maintenance, and durability. GI implementation guidance documents, standard details and specifications provide uniformity in planning, design, construction, and maintenance. By standardizing how LID is placed in the Right-of-Way agencies can reclaim valuable space for people to enjoy, turn a burden into a resource, reduce irrigation demand and stormwater runoff, and provide for a sustainable and resilient transportation corridor. When green stormwater infrastructure is integrated with complete street concepts numerous co-benefits strengthen the three pillars of sustainability; the environment, social equity, and the economy. San Diego County is one agency that implemented GI guidelines and standards. Green Infrastructure Guidelines are an outreach tool and are also intended to serve as a companion to the rest of the Green Infrastructure publications. They include an introduction, strategies, procedures and design examples for implementing Green Infrastructure projects. The strategies include tree wells, rain gardens, rock gardens, and permeable pavement. Green Infrastructure Design Criteria lay out general definitions, general policy, and landscape design criteria for Green Infrastructure strategies. Green Infrastructure Design Standard Drawings includes construction details which may be referenced in improvement plans. Green Streets Maintenance Schedules include a list with maintenance tasks, frequency, and time of year for initial, routine, and as-needed maintenance of each strategy. Green Streets Specifications include detailed construction material and installation requirements for strategies including aggregates, geosynthetics, underdrains, permeable pavement, engineered soil media, mulch, overflow risers, check dams, and tree grates. Building on the GI guidelines and standards developed within the Southern California region, these concepts were integrated into a Climate Resilient Infrastructure Guidebook for Riverside and San Bernardino Counties in southern California including climate resiliency strategies related to stormwater. The Guidebook complements city-level, climate-related transportation hazards and evacuation maps and other products developed as part of a larger resilient infrastructure initiative. The Guidebook serves as a guide to help educate local practitioners in making the transportation system more resilient to these changes. It is intended as a practical resource for jurisdictions and includes strategies, best practices, and methods for overcoming challenges and using climate resiliency tools to address changing patterns of extreme temperatures, heavy precipitation and flooding events, and drought. It was tailored to address the diverse climate, terrain, and needs of the region to ensure the long-term viability of the transportation system. Stakeholder groups and agency staff are instrumental in identifying implementation priorities and correcting procedural barriers to implementation. There is typically limited surface and underground area available within the right-of-way to accommodate often competing needs for travel lanes, parking, bike lanes, pedestrian sidewalks/paths, and utilities. In constrained right-of-way areas, this often leads to limited availability for implementation of green/climate resilient infrastructure strategies. Another challenge to implementing strategies within the public right-of-way includes often conflicting jurisdiction regulations, codes, ordinances, and standards from various levels (local through Federal) due to differing priorities of various project elements. Standardizing the implementation, design, construction, and maintenance of green stormwater infrastructure provide multiple benefits for the public and stakeholders. Integration of green stormwater infrastructure elements into transportation planning, resiliency studies and guidelines provides effective tools for planners and engineers to address changing patterns of extreme temperatures, heavy precipitation and flooding events, and drought.

APPLICABILITY The objective of this work is to develop an anomaly detection approach for biogas blowers using nonintrusive vibration sensors for machine conditions and health management. High-frequency vibration signals are collected from a tri-axial accelerometer installed on the exterior of the biogas blower casing. Long short-term memory (LSTM) artificial neural network algorithm is applied for signal classification. The proposed condition-based monitoring approach could provide a low-cost non-intrusive solution for asset management of compressors at water resource recovery facilities. INTRODUCTION Predictive maintenance (PdM) organizes maintenance activities according to the actual health state of machine tools, equipment, and systems [1]. Diagnostic PdM detect detects faults, determines root causes of operation anomalies, and estimates the current health state of a system under investigation to prevent unexpected failures. Condition-based monitoring is an approach for realizing diagnostic PdM as standardized by ISO 17359:2018. Condition-based monitoring can provide significant advantages in relation to product quality, safety, availability, and cost reduction in industrial applications. The recent advent of information and communication technologies and artificial intelligence presents a great opportunity to enhance the practice of data-driven assessment of the operation and maintenance of wastewater infrastructure [2, 3]. The objective of this study is to develop an anomaly detection approach for biogas compressors through vibration analysis for predictive maintenance. To achieve this goal, piezoelectric sensors and edge computing platforms (Raspberry Pi and Arduino board) are deployed on the biogas compressors. Machine learning algorithms are applied for classifying the collected vibration data for anomaly pattern recognition. METHODS The vibration monitoring in this study is implemented for compressor Unit 1 (KAESER) and compressor Unit 2 (SIEMENS) in a biogas facility. A low-power tri-axial accelerometer (model# ADXL345, Analog Devices, Wilmington, MA) is used with serial data communication devices such as Raspberry Pi and Arduino boards to collect vibration data from compressors. The data collection was initiated from the point of time when the compressor operated in normal condition and continued to the occurrence of any failures. The sampling frequency of the accelerometer is 1k Hz for each axis with a measurement interval of 30 minutes. Data are measured and obtained via Inter-Integrated-Circuit (I2C) bus. During the measurement, the sensor collects 10000 data points for each axis, which would take approximately 10 seconds, and is set to idle until the next measurement. The structure of the implemented condition-based monitoring is shown in Figure 1. The raw data includes the time stamp and acceleration data for the x, y, z-axis, and the sampled time for the corresponding sample. Sample x-axis vibration signals are visualized in Figure 2. The machine diagnosis is realized by scoring the anomaly levels of the vibration data, which will increase as failure approaches. Hence, an anomaly scoring model is tested to characterize the different levels of anomalies and provide an informative interpretation of forthcoming failures. The implemented model is inspired by dilated RNN network and Temporal Hierarchical One Class (THOC) network, which contributed to solving complex dependencies and vanishing gradients problems in layers. The THOC network is adopted and modified to develop the anomaly scoring model. The model consists of 3 long-short term memory (LSTM) layers with dilated skip connections. Details of the method implementation could be found elsewhere [6]. The sequential length of the transformed data is 36, and the input batch size is set to 128. In Fig. 3, each node represents a hidden RNN cell. The number of input nodes highlighted as green is determined by the sequential length of input data, which is 36. Similarity score obtained from the score function is translated to loss using the following equation that will be optimized through a training process. Adaptive Moment Estimation (Adam) optimizer is employed as it is known to have good capabilities of reaching global minimum with a high dimensional dataset. The structure of the implemented condition-based monitoring is shown in Figure 1. RESULTS The results of the model are shown in Figure 3. The input data (time-frequency domain) is visualized using power spectrum analysis. It is important to be noted that the Euclidean distance returns the length of a line segment between two vectors. Thus, the test data with a larger distance from the centers in each layer are expected to be assigned higher anomaly scores. As shown in Figure 3, anomaly points are captured when the power spectrum has abnormal patterns or when a peak value pops out from the power spectrum. Also, data points with small anomaly scores are not identified as anomalies, which might be sound as not all anomalies cause machine failures. Thus, a threshold should be carefully determined as it plays a critical role in linking such anomaly information with maintenance strategies. In this study, the threshold value is selected based on the 99.9 percentile in the anomaly scores. Different threshold values are used with an optimal threshold that prevents generating excessive false positives. The results may need to be compared to the actual machine condition such as whether abnormal operations were present while it was monitored. Since Euclidean distance may not be intuitive on a high dimensional dataset, different scoring functions are also tested for comparison. Chebyshev scoring function is adopted and the result is visualized in Figure 4. Chebyshev distance provides the greatest differences between two different vectors along any coordinate dimension. Hence, input data with the highest variance and difference are likely to obtain higher anomaly scores. As shown in Figure 4, the power spectrum with peak values tends to be identified as anomalies. In this case, the warning stage depicted with the orange line was applied with an additional threshold (99 percentile) to demonstrate a warning system that may be applicable to the data-driven maintenance strategy. In this study, the anomaly scoring model has been utilized to detect the abnormal vibration patterns and interpret them into anomaly scores. Based on the results from the proposed anomaly scoring model, a notification strategy can be established for further maintenance scheduling. The operation and maintenance manual or guidelines are provided by manufacturers of the machines. An example of the operation and maintenance manual of a compressor is shown in Table 1. Proper maintenance requires timely tracking of operation hours followed by appropriate actions such as checking oil levels, changing filters, and grease bearings. CONCLUSIONS AND RELEVANCE This study presents a condition-based monitoring approach for biogas compressors as an example of data-driven asset assessment. The test anomaly scores were calculated based on a similarity between unseen data and clusters that are learnable by machine learning algorithms. The study shows that condition-based monitoring using nonintrusive vibration sensors could be a useful asset management tool and providing early failing alarms of equipment embedded in WRRFs. The result of this study suggests that the operator's supervisory control and condition-based monitoring could be integrated for asset management (Figure 5). A combination of preventative maintenance following manufacturer's O&M manual and predictive maintenance guided by condition-based monitoring could lead to adaptive asset management program. Meanwhile, deploying condition-based monitoring solution at WRRFs may add additional responsibilities to the maintenance crew at WRRFs. Future studies are required to understand the operator demand, capital investment, and cybersecurity implications of condition-based monitoring for WRRFs. Attendance at this presentation will benefit operators and design engineers who are interested in data-driven asset management through condition based-monitoring. This study presented a novel application of deploying nonintrusive vibration sensors and edge computing for anomaly detection of biogas compressors. The method developed in this study could be applied in asset monitoring of other rotary equipment in WRRFs.

The mining of non-renewable phosphate rock is currently the primary phosphorus source for food production. Phosphorus recovery from secondary wastes is a key component for circular economy. Municipal digested anaerobic sludge, or digestate, is a liquid-solid mixed liquor produced from anaerobic digestion that is enriched with phosphorus (P). Around 40% of the phosphorus discharged by anthropogenic activity will end up in the wastewater sludge, making digestate a promising phosphorus source. Conventional method for phosphorus recovery from the digestate like struvite precipitation is practically challenging. One of the main reasons is the heavy chemical consumption and the high risk of handling corrosive acid/base. Electrochemical methods are of strong research interest lately due to the elimination of chemical use, flexible process control, and low environmental impact. In this study, we designed an electrochemical nutrient recovery cell (ENRC, Fig. 1) to achieve simultaneous phosphorus release and nutrient recovery from the digestate. The digestate was sampled from Missouri River Treatment Plant in late September of 2021. Most phosphorus exists in the solid fraction of the digestate and need to be firstly released into the aqueous phase, usually by lowering the pH, before the recovery. As shown in Fig.1, water electrolysis reaction will induce the acidification of the digestate and increase aqueous PO43- concentration in the anode. Meanwhile, electric field will drive NH4+ to migrate across the cation exchange membrane (CEM) into the recovery chamber. Results show the digestate was acidified from pH 8.0 to 2.0 in the anode of the ENRC after operating for 5 h under the current density of 25 A m-2, similar to the pH adjusted by the conventional HCl adjustment method. Both methods released 67.6~74.1% of total phosphorus in the digestate and achieved the comparable PO43--P concentrations of 253.47 ± 3.05 mg L-1 and 277.60 ± 15.2 mg L-1 (p-value > 0.05), rising from 27.72 ± 0.95 mg L-1 in the untreated digestate (Fig. 2). In contrast to the high NH4+-N concentration of 995.07 ± 53.11 mg L-1 in the HCl treated digestate, electrochemical leaching removed >99% of NH4+-N from the digestate (Fig. 2). The HCl adjustment increased Ca2+ concentration from ~89 mg L-1 to 479 mg L-1, much higher than 31 mg L-1 Ca2+ in the ENRC anode effluent, likely due to Ca2+ migration through CEM into the recovery chamber. The HCl treatment introduced a high concentration of Cl- (~4700 mg L-1), which was avoided in the ENRC anode effluent that had ~120 mg L-1 Cl- (Fig. 2). The nutrients were successfully recovered in the ENRC recovery chamber after continuous operation for 5 cycles. As shown in Fig. 3A, the ENRC released 147.59~215.24 mg L-1 PO43--P from the digestate at the end of each cycle, accounting for 40~58% of total phosphorus in the digestate. The catholyte removed 96-98% of the PO43--P and produced an effluent with < 5 mg PO43--P L-1. The PO43--P concentration in the recovery solution reached 142.62 ± 7.78 mg L-1 after the first cycle and gradually accumulated to 404.56 ± 20.44 mg L-1 after 5 cycles, which accounted for 72% of the total PO43--P released in the anode. Mass balance revealed that after removing the recovery solution, 6.9% of the released PO43--P remained or adsorbed in the recovery chamber (Fig. 3B). In addition, 9.8 % of the released PO43--P precipitated in the cathode chamber due to the high pH environment. The NH4+-N concentration in the recovery solution linearly increased to 3493.56 ± 194.13 mg L-1 h-1 after five cycles of operation (Fig. 3A), accounting for ~90% of the total NH4+-N in the digestate. After adjusting the pH to 8.5 in the final recovery solution, more than 99% of the PO43--P was precipitated to produce a solid with light brownish color. The inorganic contents in Fig. 3C shows that PO43--P contributed to ~13.62% of dry mass in the product, which was equivalent to 31.19% P2O5 content and would meet the 25%~37% P2O5 requirement for economic grade phosphate rock. Calcium was the major metal and took up ~16.54% of the dry weight in the product, indicating a good soil phosphorus availability. After the nutrient extraction, around 42% of the dissolved COD was removed and the digestate settleability was significantly improved. This work has demonstrated an effective electrochemical approach to extract nutrients from the waste digestate and can be extended to treat phosphorus-rich biosolid wastes generated from different sectors. This work has been published: Wang, Z. and He, Z.* (2022) Electrochemical phosphorus leaching from digested anaerobic sludge and subsequent nutrient recovery. Water Research. Vol 223, Article 118996.

Anaerobic digestion is a process central to the stabilization of sewage sludges while also proven to be the effective first step in many resource recovery programs. Mesophilic anaerobic digestion has proven efficient, effective, and reliable process for decades. However, with increasing capital costs, increased value of recovered resources and a societal push toward decarbonization, in an attempt to limit the impacts of climate change; interest in intensification of the digestion process has grown. In the past decade the adoption of intensified or advanced digestion processes has increased. Processes like thermal hydrolysis, thermophilic digestion and co-digestion have demonstrated that conventional process limits, performance and stability indices need to be reassessed and defined for the next generation of water resource recovery facility. Metro Vancouver, has experience with advanced digestion technologies, like its Class A series thermophilic anaerobic digestion system at Annacis Island, pioneering its adoption in the late 1990's. However, since its adoption and nearly 20 years of effective operations the true capacity limits of this process have yet to be defined. To define the operational limits of a biological process, a range of process metrics must be considered these include: - Substrate loading capacity. -Minimum solids retention time - Acclimation potential to inhibitory compounds - Process reaction rates - Dynamic stress responses and recovery (load, temperature, feed composition, toxicity, etc.) To elucidate these metrics at scale is possible, but the impacts of potential process failure can be significant, including long recovery times, process restart, loss of treatment and odors. Any of which can represent significant costs when managing thousands of cubic meters of material (millions of gallons). These risks further increase when new processes are being implemented and/or augmenting an existing digestion process. Further, testing new unproven technologies at scale that on paper would appear to be effective often prove to be more complicated than first envisioned, resulting in increased costs. These costs could result in a premature cessation of process development. One approach researchers and early adopters have addressed these challenges is through the bench testing, on-site and at universities. While these often provide evidence for proof of concept, they are limiting in scale and scope; often not integrating the true variability in operation that a full-scale facility, leading to conservative designs or non-adoption due to risk avoidance. Ultimately this slows the progression of technology advancement. Metro Vancouver, has elected to accelerate the testing and adoption of new processes for its wastewater treatment plants through the construction of the Pilot Digestion Facility (PDOF). This facility consists of three 8 cubic meter digesters, and a feed skid. The digesters are capable of operating at range of temperatures, retention times, mixing strategy and process phasing strategies. The PDOF not only allows for new processes to be tested but also existing systems to be stress tested to defined the maximum capacity of their existing assets. Further, at this scale, it is possible to test processes under real-world conditions, to better assess implementation at scale and process viability at scale. In June of 2023, the PDOF completed construction and commissioning and was started-up at the Lulu Island Wastewater Treatment Plant, in Richmond, BC. One of the first test plans implemented was to evaluate the reproducibility of pilot results relieve to the full-scale operating digesters. Three PDOF digesters were operated at solids retention times of 15, 20 and 28 days respectively on a mix of thickened primary (TPS) and waste secondary sludge (TWSS). Core process metrics were monitored to determine, system performance and compared to the full-scale operating digesters. Figure 1, shows the relationship between digester operating SRT and volatile solids destruction, after each of the three test digesters had reached stead-state and compared it to reference data and LIWWTP's current digester operations. What is apparent from the PDOF and the reference data is that 15 days SRT appears to be an inflection point around which further reduction in operating residence time will result in notable reduction in solids destruction which ties directly to biogas production. The current industry primary practice for resource recovery is biogas generation and methane utilization. Understanding this inflection point and being able to accurately test around this point will provide significant understanding of the total benefit of future process optimizations. Further what is also apparent is that the sludge a LIWWTP is more degradable than a 'typical' sludge, based on the reference data information. This is likely due to a combination of very low industrial input, high volatile content and a low overall residence time in the secondary system, a trickling filter solid contact system. The fact that the PDOF system produced similar VSr to the full-scale, suggests the system is performing in a similar manner to the full-scale digester, making extrapolations to full-scale relatively direct. In terms of reproducing the performance of the anaerobic digesters at LIWWTP, there was generally good agreement in the data, between the pilot and the full-scale digesters in terms of solids destruction, volatile acids, alkalinity and ammonia, Table 1. Biogas data was not completely reliable during this time as condensate was impacting meter accuracy on the pilot units. Modifications to the meter orientation, appears to have improved the response. As part of understanding the overall potential of anaerobic digestion and to gather further in-sites as to the fundamental mechanisms driving the observed results, microbial ecology analysis was conducted to understand changes in the consortia present. As part of this baselining observation the result of these efforts will be discussed. Figure 2, presents the relative abundance of different phylum level populations with time for each of the PDOF digesters and a single steady-state point for the LIWWTP digesters. Figure 3, further refines that focusing Euryarchaeota, which contain the methanogens. With the successful demonstration of the mesophilic operation of the PDOF facility, completing commissioning, the first tests of intensified digestion have commenced. The process being converted over to thermophilic operations to evaluate the limitations of the process. As of authoring the digester temperature has been increased and the microbial population is transitioning to thermophilic, as denoted by the significant increase in volatile acids and deterioration of biogas production. A process condition understood to be typical. Once steady thermophilic operation has been reached a range of process conditions will be tested. These include, reduced SRT and increased organic loading rate. This not only will demonstrate the potential for LIWWTP to utilize thermophilic digestion to increase capacity but also further define the capacity at the larger Annacis Island WWTP. This paper will discuss the results of the completed baselining operations, including lessons learned, and observation due to different operating retention times for mesophilic digestion. It will further present relevant observations from the conversion to thermophilic, which are in progress now.

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.

Charlotte Water (CLTWater) has 123 MGD of capacity between five major wastewater treatment plants (WWTPs) and is interested in sustainable and cost-effective technologies that may be selected for future WWTP expansions or for replacement of existing treatment infrastructure. Aerobic granular sludge (AGS) is an innovative secondary wastewater treatment technology that can achieve biological nutrient removal (BNR). Aqua-Aerobic Systems, Inc (AASI) is the vendor for AquaNereda, the patented AGS system that utilizes specific biological and hydraulic selection pressures to produce and maintain the AGS in a sequencing batch reactor (SBR). CLTWater elected to pilot AquaNereda to understand how it might be used to expand the capacity of our overall system, either at an existing plant or in place of another BNR technology at our new plant under design, the Stowe Regional Water Resource Recovery Facility (SRWRRF). An AGS pilot was performed at McDowell Creek WWTP from June 2019 to February 2020 to determine its viability as a treatment for CLTWater. Before starting the AquaNereda pilot, CLTWater developed a list of objectives to achieve during the piloting process with actionable and achievable goals defined for each objective. These objectives included 1. Evaluating simulated performance representing treatment with and without primary clarifiers 2. Observing development of granules from flocculant sludge 3. Evaluating solids characteristics 4. Evaluating process control and operability 5.Involving State regulatory agencies to facilitate potential future permitting processes To address the objective of evaluating solids characteristics, a separate solids study was conducted at Bucknell University to provide insight on solids handling and treatment impacts for potential full-scale Nereda implantation. CLTWater wanted to assess impacts to digestion performance, dewatering, and recycle streams when aerobic granular sludge (AGS) and conventional activated sludge (CAS) are treated concurrently. During the study, Bucknell operated four lab-scale digesters that were fed several solids blends (Table 1) including two 100% thickened waste activated sludge (WAS) digesters to demonstrate differences between AGS and CAS WAS and two 60% primary sludge (PS)/40% WAS digesters to simulate McDowell's current digestion process and the expected maximum contribution of AGS to any digestion process at CLTWater. Waste solids from the Nereda pilot reactor treating primary effluent were thickened to ‰¥5% using gravity belt thickening and shipped to Bucknell with thickened PS and CAS-WAS from McDowell's full scale processes. Bench-scale 20-day HRT mesophilic anaerobic digesters were fed daily. Biogas production was monitored throughout the trial, but other analyses were performed after 71 days (~3.5 SRTs) to ensure results were representative of steady-state conditions. Results include quantified metrics and other observations related to 1) digester performance VS destruction, biogas production; 2) solids handling sludge viscosity, polymer demand, cake solids, cake metals content and odor production; and 3) recycle streams digestate nutrient concentrations. For digester performance, results showed that volatile solids reduction (VSR) for AGS-WAS was comparable to CAS-WAS with slightly different methane yields between Digesters 3 and 4 (60% PS/40% WAS). Minor differences in solids handling parameters were observed including marginally higher viscosity and polymer demand for digested solids that included AGS, but these differences were more pronounced in the digestate from Digesters 1 and 2 (100% WAS). Recycle stream soluble TKN concentrations were similar regardless of WAS source; however, recycle streams from reactors including AGS-WAS were characterized by markedly lower soluble TP concentration. The finding of much lower soluble TP concentration for AGS-WAS was surprising given that the Nereda process includes enhanced biological phosphorus removal (EBPR) and the pilot reactor performed comparable EBPR as the full-scale mainstream conventional BNR process. Unfortunately, the pilot timeline did not allow for additional investigation into the cause of this observation, but further research may be warranted in this area. This presentation will discuss high-level results from each of the objectives targeted during the AquaNereda pilot but will focus mainly on the solids-related findings. We will present overall conclusions from the pilot as well as lessons learned related to implementing a pilot for a process that has broad reaching implications across a wastewater treatment plant. Finally, the future of AGS implementation at CLTWater will be discussed.

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.

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.

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.

As the City of Somerville navigates aging infrastructure, regulatory pressures, climate change and redevelopment opportunities, innovative and cost-effective approaches for urban flood relief are being implemented under its Union Square Stormwater Mitigation Program (Program). The City is in its 10th year of program implementation. This project demonstrates how stormwater authorities and consultants can adapt their integrated planning over the course of a project life-cycle. It also features how municipal urban flooding can be creatively solved by engaging in inter-agency cooperation during major public transit projects. Flood mapping and construction photographs of the various projects construction will be featured. BACKGROUND The Union Square area is a commercial district with dense adjacent residential development that lies at the bottom of a large, combined sewer catchment. Presently, stormwater is conveyed by municipal sewers to the Massachusetts Water Resource Authority (MWRA) regional combined sewer system. The MWRA system is capacity-limited downstream of this connection. Flooding is experienced during wet weather equivalent to an existing 2-year / 24-hour design storm or greater. The flooding originates from a historical filling of the Millers River in 1879 and impacts many minority-owned small businesses, the City's Public Safety Building and multiple neighborhoods designated as Environmental Justice Neighborhoods for Minority and Income. INTEGRATED PLANNING Planning originated with an Evaluation of Flood Reduction Alternatives in Union Square (2013). This hydraulic modeling and project prioritization study evaluated the different surface runoff management and storage options throughout the watershed to mitigate or eliminate flooding in the Union Square area. To avoid maintenance-intensive combined sewage facilities, the preferred scheme was to separate sewers and overflow excess stormwater to detention facilities of various sizes. The first project planned was the Nunziato Field Stormwater Storage Tank ($13.6 Million, 2017) being a 1.6 MG storage facility located below a park with rain garden. The project was designed with sewer separation of adjacent streets on a hillside. It functions to capture peak flows and is pumped out post-storm event. The park's design also includes a interactive rain garden for stormwater quality and public education. During design of the Nunziato Tank project, an opportunity arose during expansion of the MBTA public transit system. Upon seeing that the project included stormwater conveyance for 50-year design storm events, City planners quickly recognized that the infrastructure would be underutilized when Union Square flooded. By making a connection to it, the City could regain a stormwater outfall in the Millers River watershed. To validate this plan, the City integrated MBTA's hydraulic models into its own citywide hydraulic model (InfoWorks ICM). The raised railway bed meant that stormwater would be pumped to it, which risked exceeding the available capacity of the MBTA system. Different combinations of pump capacity and storage volumes were evaluated with different degrees of sewer separation tributary to Union Square. The modeling performed convinced all parties that a maximum pumping capacity of 50 MGD could be allowed. An agreement was then negotiated for the City to discharge into the MBTA drainage system. Upon conceiving this stormwater pump station, the City began to modify its Program: -Climate change design storms for the Year 2030 time horizon were established, enabling resiliency planning for intense precipitation. A future 5-year design storm was established comparable to an existing 10-year event. -Design and construction of the Spring Hill Sewer Separation ($23.4 Million, 2021), a 71-acre project involving complete streets and green infrastructure improvements, became the new priority to unlock more stormwater to be conveyed by the future pump station. -Construction of the Nunziato Tank project was re-sequenced to occur after the pump station to allow further optimization and phasing. POPLAR STREET PUMP STATION Now, four years after developing the concept, the Poplar Street Pump Station ($80 Million, 2023) is beginning construction on a 2-acre brownfield site. The project includes a 6,100 SF building that centralizes stormwater operations across the City, a 4 MG underground storage tank, and high-visibility green infrastructure consisting of rain gardens, infiltrating bio-basins and three blocks of infiltrating tree ways to emphasize stormwater management and public education of the facility. The site is also being co-developed as a public park themed around art and urban agriculture, with adjacent complete street improvements. The pump station site lies in the center of the Brickbottom district, where its own microcosm of integrated planning required a non-traditional approach to wet weather engineering. Over the course of three years, an inter-discipline team of planners and engineers successfully resolved the facility's design with a host of complex interfaces: 1.Historic Arts Community — local citizenry passionate about maximizing the park site 2.Brickbottom Vision Plan — prioritizing alternate modes of transit next to the site (pedestrians, biking, buses and rail) 3.GLX Community Path Connection — incorporating ADA pedestrian ramps, bike lanes and a public plaza above the force main discharge 4.McGrath Boulevard — an ambitious DOT plan to eliminate an elevated highway next to the site 5.MBTA Bus Network Redesign — incorporating a prominent bus stop into the site 6.Utility Renewal — upgrade of aged water and gas mains along the force main alignment Wet Weather Management & Control During pump station start-up in late 2025, its operation will be unmanned and rely on telemetry shared between City and MBTA facilities. Level sensors monitoring storm drains along the railway will signal when the MBTA drainage system has reduced capacity, generally coinciding with the existing 5-year design storm event. Variable-speed drives are controlled to slow pumping and match the reduced capacity. For larger storms approaching an existing 10-year design event, no capacity may be available during the peak of the storm. It is these situations when the 4 MG underground storage tank activates as a peak shaving facility and is later pumped out post-event. This combination of pumping and storage eliminates stormwater flooding along the Somerville Avenue corridor for the existing 10-year design storm, providing a stimulus for large scale redevelopment. Recently enacted City stormwater regulations further require large developers to reduce their stormwater runoff into the public right of way (piped and/or overland) such that the 10-yr proposed peak flow is less than the existing 2-yr peak flow. Privately operated storm water storage tanks are being constructed in this area, enhancing the flood resiliency of Union Square. Another aspect of the pump station is how it fits into the National Pollutant Discharge Elimination System (NPDES) permitting framework. The City is studying whether the pump station discharge should be listed as a co-permittee under the MBTA's NPDES General (agency) permit or for it to be part of the City's NPDES MS4 (municipal) permit. Stormwater quality will factor into this decision.