Introduction: Ultraviolet LED technologies have progressed to the point where full-scale implementation is now on the horizon. The work outlined in this study is part of WRF project 5173 which investigates the feasibility of UV LEDs at different magnitudes of flow and water qualities. A 280nm, 100 GPM, closed-channel UV LED unit was installed in a wastewater facility in Nova Scotia, Canada to compare to a conventional open-channel UV disinfection system. This project represents the first ever installation of UV LEDs for wastewater disinfection at this scale and provides foundational data for understanding how UV LEDs scale as a technology. In addition, the practical experience gained during the installation process of this technology is valuable to consultants and utilities who may be considering the use of UV LEDs in the future. Project Background: Data was collected over a 4-month period before the installation of the full-scale UV LED system using the UV auditing approach. The UV auditing approach has been developed by Dalhousie University and provides an understanding of the delivered fluence for full-scale UV disinfection by leveraging bench-scale inactivation curves (Rauch et al., 2022). This approach has successfully demonstrated that UV LEDs can outperform conventional, mercury-based 254nm disinfection for some wastewater matrices (MacIsaac et al., 2023). UV auditing is also useful for utilities in understanding how LEDs will perform when considering mercury-free disinfection technologies. The LED reactor used for this work (shown in Figure 1) was manufactured by AquiSense Technologies and is a closed channel design with a 100 gallon per minute (GPM) capacity and was conducted over the Fall of 2023. The flow capacity of the LED unit represents approximately 10% of the average daily flow of the wastewater facility that it has been installed at. This installation marks the largest commissioning of a UV LED wastewater disinfection reactor anywhere in the world. Pre-installation data is shown in Figure 2 and was collected during the Summer of 2023. The average UV transmittance measured at the facility during this sampling period was 53% with an average power consumption of 35 KW. The disinfection results indicate that 280nm UV LEDs performed comparably to conventional 254nm low-pressure system and can provide sufficient pathogen inactivation when used at the full-scale. Additional Project Phases: The second phase of this work involves stress testing the UV LED reactor to define the range of performance in terms of power output, flow rate and UV transmittance. This work was conducted over a 4-week period in early 2024 and involved operating the reactor at a flow rate of 100 and 200 GPM, as well as power outputs ranging from 50-100%, and variable UVT during the sampling period. The final phase of this work involves the comparison between the UV LED reactor with the conventional, open channel, low-pressure UV system that is already installed at the facility. This work covers a 6-month period with twice weekly sampling of the inlet and outlet of both treatment trains. A scale analysis concludes this work by collecting samples of internal surfaces at the end of the six-month sampling period. This work identifies the differences in fouling mechanisms between each of the UV light sources. UV LEDs do not generate heat on the emitting side of the light source and therefore, are not expected to form inorganic scales in the same way that conventional mercury lamps do. This work provides foundational information for both consultants and utilities when considering approaches for testing the feasibility of using UV LEDs in wastewater facilities. UV LEDs have shown to be comparable in performance to conventional systems while avoiding several of the environmental, human health, and safety issues related to mercury-based UV disinfection. In closing, the tasks conducted in this work help achieve the goals in understanding UV LED implementation as defined in WRF 5173.

Background Water resource recovery facilities (WRRFs) around the world are constantly faced with significant challenges 1, 2. It is estimated that WRRFs are operating at an average of 81% of their design capacity, while 15% of systems are at or have exceeded that threshold3. As the most prevalent biological nutrient removal (BNR) process, any improvements to conventional activated sludge (CAS) processes are highly desirable in our industry4. However, upgrading CAS trains is costly and alternative technologies often tend to be more energy-intensive, expensive1, and time consuming to install, commission, and operate. Thus, the use of physical selectors (e.g., hydrocyclones) for biomass densification has emerged as a front-runner for increasing secondary clarifier capacity and improving nutrient removal. Objective and Approach Despite the many studies exploring the advantages of densified activated sludge (DAS) systems compared to CAS systems, DAS impacts on microbial communities and fecal indicator bacteria (FIB) are unknown2, 5. In 2023, the Water Research Foundation funded a tailored collaboration with the Metro Water Recovery (MWR) in Denver. The collaboration aimed to investigate FIB removal and disinfection kinetics. This study focused on CAS and DAS treatment trains at three North American full-scale operating WRRFs (Figure 1). The WRF project aims to: A) Compare E. coli concentrations over a 15-month period and investigate factors influencing differences (e.g., granulation size distribution, floc/granule mass fraction, floc/granule aSRT, microscopy, COD, Turbidity, TSS, NH3, pH, Temperature, Color, UV-254, TKN, TP, TOC). B) Determine how changes in Secondary Effluent (SE) properties between DAS and CAS affect disinfection efficacy using chlorine, peracetic acid (PAA), performic acid (PFA) and ultraviolet disinfection (UV) seasonally (n=12), with the same water quality parameters listed in Objective A. C) Assess impacts of operational variables on DAS and provide utilities with recommendations. These can include how to utilize modeling and statistics to improve performance using demand and decay values and mechanistic disinfection efficacy models D) Determine if additional analyses (e.g., protozoa counts, granule sieving analyses) provide operational value to utilities adopting DAS. Results Data collected for one year at the MWR Hite Treatment Facility highlights the statistically significant difference in E. coli concentrations between the CAS and the DAS trains (Figure 2). This could be explained by a variety of variables that have not yet been evaluated. FIB counts may be impacted by the predator protozoan community5, but this has yet to be supported by data (Figure 3). While percent mass fraction (Figure 4) and seasonality (Figure 5) have been hypothesized to impact DAS E. coli counts6, this has not been shown by the preliminary data collected, which highlights the importance of a more detailed study to explain the differences observed . Summary DAS is able to be implemented with low capital cost while increasing the capacity of CAS systems. However, there is little data on how SE from DAS systems impact downstream disinfection processes. This WRF project will evaluate the impact DAS systems have on disinfection processes compared to CAS systems. Data collection and testing for this project will begin in April 2024.

Ozone is well known as an effective disinfectant and oxidant and has been operated for drinking water treatment for more than 100 years, often in combination with biofiltration or biologically active carbon filtration. More recently, it is also applied on wastewater treatment plants (WWTPs) to mitigate the discharge of chemicals of emerging concern (CECs) into receiving surface waters. As a first European country Switzerland implemented a regulation to reduce the discharge of CECs from WWTPs in 2016. With the overarching goal to substantially reduce the load of CECs discharged into surface waters, requirements for advanced wastewater treatment were defined for the largest WWTPs and those plants which are discharging into sensitive water bodies in the country. In total more than 100 WWTPs of different sizes are affected. The discussion about the specification of the regulation was supported by pilot- and full-scale trials like at the WWTP in Regensdorf/Switzerland (Abegglen et al., 2009). Currently, there are ten WWTPs operating ozonation systems or combined ozonation + biologically activated carbon filters in Switzerland. The biggest installation is located at WWTP Werdholzli, which treats the wastewater of Zurich with a design flow of 6,000 l/s. No regulation for CEC mitigation on WWTPs is currently in place in the EU, but a draft of the Urban Wastewater Treatment Directive was proposed in October 2022, which for the first time includes requirements for advanced wastewater treatment. The approach is similar to regulations in Switzerland and defines an average removal of 80% for a list of indicator CECs, which will become mandatory for all large WWTPs (>100,000 PE) within the EU. In addition, requirements for CEC mitigation at medium sized WWTP will be assessed following a risk-based approach. Despite the lack of regulatory pressure, CEC mitigation has been applied at numerous WWTPs in different EU member states. In Germany, the installation of advanced treatment is funded by some federal state governments. Main treatment goal is the improvement of the chemical conditions of the receiving water bodies. Currently, sixteen ozonation systems are in operation on German WWTPs with the biggest at WWTP Aachen-Soers treating up to 3,000 l/s. In the Netherlands, Belgium, Sweden, and France first full-scale installations are close to start or in operation. Other EU member states such as Austria or Italy tested the process in pilot installation (e.g., KOMOZAK (Kreuzinger et al., 2015) and KOMOZAK II (Krampe et al., 2020)). It can be expected that the number of installations in the EU will increase rapidly once the revised UWWTD will become into place. Beside regulatory changes the design and control strategies have changed during the last years. The first installations were designed for ozone dosages up to 0.2 2 mgO3/mg DOC (Lyko et al., 2013), but recommended ozone doses decreased over time, these big ozone generators are nowadays operated a lower production level. Today, the recommended ozone dosages are ranging from 0.5 0.7mg O3/mg DOC (DWA, 2022) and can be even lower for combined processes of ozone and activated carbon. Ongoing research on related topics, e.g., testing of surrogate parameters for performance monitoring or dose control, leads to further optimization of the installed process. These optimizations significantly reduce the size of ozonation systems and the specific operational costs. In addition, different mixing concepts such as diffusors or injectors were installed and compared at pilot- and demonstration-scale. New tools such as computational fluid dynamics modelling (CFD) and kinetic model approaches support the optimization of ozone contact basins and support the layout of ozone mixing and effects on the water quality during the engineering of ozone installations. Additionally, the feedback from operators provides valuable input for improvement since some effects can only be seen during long-term operation. Based on experiences and optimization, new guidelines, for example in Germany (DWA, 2022) and Switzerland (VSA, 2021), support the design, installation, and operation of new systems. The current draft regulation in the EU includes medium to large WWTPs, which raises the question if comprehensive implementation of CEC removal is also expedient for small WWTPs. Although there is no active regulation in place, first projects were launched at smaller WWTPs that are discharging into small and sensitive waterbodies, which might even be used as drinking water sources. The adaptation of advanced treatment technology for small WWTPs bears new challenges because staff for operation and maintenance is often not available, influent flow and quality can have stronger variation, and specific operational and investment costs of smaller WWTPs are often higher. This presentation will provide an overview on current and planned installations of ozonation for CEC removal on WWTPs, highlight lessons learned from 15 years of full-scale operation, and outline expected trends for the future. Besides the discussion on small-scale WWTPs, we will emphasize potential synergies of CEC removal with the recently launched EU minimum requirements for water reuse in agriculture (EU Regulation 2020/741). Since reuse becomes more relevant for different EU member states, the considerations for CEC removal at WWTPs should include the option of future upgrades for water reuse purposes.

INTENDED OBJECTIVE: Biosolids from water resource recovery facilities (WRRFs ) are increasingly used for agricultural and recreational land purposes due to their sustainable means to replenish macronutrients. However, the relatively high phosphorous content of biosolids limits certain applications. This study aims to identify optimal locations for recovering vivianite and subsequently phosphorus, to allow class A biosolids reach ideal phosphorus levels. INTRODUCTION: Global consumption rates of synthetic fertilizers per unit of cropland have increased 3 to 8 times over the past half century (Lu et al. 2017). Class A biosolids are increasingly explored as an alternative to commercial fertilizers due to their effective means to replenish carbon and macronutrients (Gilmour et al. 2013). However, the N:P ratio of biosolids is typically lower than commercial fertilizers which can cause an accumulation of phosphorus when applied to soil, increasing risk for eutrophication (Penn et al. 2002). Therefore, it is critical to implement efficient phosphorus-removal technologies/techniques within the biosolids treatment train to improve the N:P ratio and limit the amount of phosphorus that result in the cake. Therefore, this study aims to analyze the P mass balance of the Blue Plains advanced wastewater treatment plant in Washington, DC as well as its vivianite characterization in full-scale. The process sampling, modelling and analysis led to identification of potential locations for vivianite recovery, and initial estimations on how much the P content in our class A biosolids might be reduced by recovering vivianite upfront. MATERIALS AND METHODS: Sampling campaign: Samples were collected in DC Water Blue Plains over a 3-month period (Mid-February to Mid-May 2022). Quantitative analysis: Phosphorus is measured by the EPA 365.1 method. Scanning Electron Microscopy with Energy Dispersive and Mossbauer Spectroscopy: Prepared by method in Prot et al. 2021. Modelling method: Visual Minteq version 3.3 with DOC SHM model RESULTS & DISCUSSION P mass balance at Blue Plains and P content in biosolids product Blue Plains advanced WWRF achieved a 98% incoming TP removal over its primary (enhanced-chemical phosphorus removal) and secondary systems through iron dosing. The removed P is diverted to the solids fraction and results in a Class A biosolids product (BLOOM) with 2.88% P (dry weight basis) and 28-32%TS (Fig.1A). The P:N ratio of our product is 1:1 and thus higher in P content than the target of 1:2 P:N for typical fertilizers. Decreasing P content in BLOOM by 50% or thus recovery 60% of vivianite would increase the value and applicability of BLOOM. Vivianite formation and formation potential along the Solids Treatment Train A total Fe/P molar ratio of 1.5 or greater allows for optimal vivianite precipitation (Cong et al. 2017) which is reflected in DC Water treatment flow diagram (Figu 1). Vivianite was detected in primary thickened sludge, blend of thickened primary (PS) and waste activated sludge (WAS), and digested sludge b ased on sequential extraction method in Wang et al. 2021. This was also further supported by the clear co-location of Fe and P in SEM images (Figure 2A and 2B). These locations are consistent with the vivianite scaling seen in primary sludge gravity thickening lines and centrifuge lines in the facility. Through quantitative analysis, the vivianite mass flow in thickened primary sludge, blended PS/WAS and digested solids accounted for 8%, 52%, and 49% of the incoming P to the plant (Fig. 1). These vivianite ranges are like those reported by iron-dosing plants in Prot et al. 2021 and Wilfert et al. 2016. Estimation of P recovery potential needed to impact Class A biosolids P content Based on the current vivianite-P levels in the three identified locations (Fig. 1), sludge after anaerobic digestion contained the highest level of vivianite-P. This is likely due to higher orthophosphorus levels after thermal hydrolysis treatment which allows for additional vivianite formation with Fe(II). This notion is supported by the low levels of Fe(II) concentrations after anaerobic digestion indicating that most of it is bound (Fig. 1). We estimated how much vivianite recovery efficiency we might need to decrease the P content in the BLOOM with an ideal target of ~0.014 kg P/kg TS and acceptable target of 0.022 kg P/kg TS. Given the highest vivianite levels in digested sludge, a recovery efficiency of at least 40% with ideally 70% is sufficient to meet our targets (Fig. 3). Utilizing vivianite recovery technologies such as magnetic separation (80% of vivianite recovery in digestates according to Wijdeveld et al. 2022), and other alternative options could provide the potential recovery target needed to improve BLOOM. CONCLUSIONS Based on current vivianite-removal technology efficiencies, removing vivianite will significantly impact the phosphorus levels in BLOOM. Results suggest that after anaerobic digestion is a preferred and feasible option to implement recovery technology due to its high vivianite content as well as the opportunity to recover vivianite in a fraction of the digestate to produce low P BLOOM rather than the whole biosolids treatment train. Future testing will explore recovery efficiencies of P and vivianite to confirm feasibility and setup a path towards pilot testing approaches.

A twin outfall relief sewer system for a major municipality is comprised of twin box structures approximately 11 LF in height and 10-12 LF in width, with average flows of 200-700 MGD. This sewer system is located below a military facility, making all inspections and repairs demand additional security considerations. During recent inspections of the twin outfall relief sewer system, CCTV footage showed areas of the sewer structure with extensive corrosion damage from microbial hydrogen sulfide (H2S). The damage caused by the H2S was so severe that the center wall between the twin box structures was missing for approximately 75 LF and much of the inner layer of reinforcement was also missing. The Owner's engineer performed structural analysis and determined the degraded portion of this structure was near collapse. Based on the as-found conditions and analysis performed, emergency remediation of approximately 910 LF of rectangular box structure was deemed necessary. The next step to minimize risk of collapse involved removal of the soil overburden in the region where the sewer system showed severe distress. The project team worked to develop a bypass system to reroute flows so permanent repairs could take place. Given the live flows within the structure, rehabilitation options needed to be selected prior to the bypass system being in place and the structure dewatered. This uncertainty regarding the condition of the structure required the repair system selected to be flexible to accommodate varying degrees of degradation. An innovative sewer rehabilitation technology was selected which involves installation of custom fabricated steel rings, HDPE interior protective layer, and a flowable grout to fill the space between the HDPE and the host structure. The design of the rehabilitation system can be adjusted based on as-found conditions, giving the project team the flexibility needed to move forward with repair design in parallel to installing the bypass and performing a more thorough condition assessment of the structure. This technology has a history of over 20 years of successful implementation in Japan with over 250,000 LF of successful pipeline repairs. This extended history along with extensive technical vetting allowed the project team to feel confident moving forward with a first-of-a-kind application in the United States. This paper will highlight the investigation, analysis, design, and emergent repair of this critical structure. Perspectives from the Owner, Engineer, and Contractor will be provided, along with insight on the options analysis process, and lessons learned throughout.

Antimicrobial resistance (AMR) makes diseases more difficult to treat and has been spreading worldwide. It is considered a major public health concern. Over the last two decades, numerous projects investigated the occurrence of AMR, especially antibiotic resistance, in wastewater. In 2023, several papers (e.g., Berglund et al., 2023; Wang & Smith, 2023; Zhao et al., 2023) reported the detection of antibiotic-resistant genes (ARGs) and mobile genetic elements (MGEs) in wastewater, resulting in negative news stories and media inquiries at water resource recovery facilities (WRRFs) about AMR and potential risks from wastewater or biosolids (Wigglesworth, 2023). In addition, the Centers for Disease Control and Prevention (CDC) has expressed interest in including wastewater-based surveillance (WBS) of AMR targets in its National Wastewater Surveillance System, which will lead to continued focus on AMR. This presentation is intended to help inform the water sector as attention to this complex topic grows. It provides a summary of concepts related to antimicrobial and antibiotic resistance and the current state of the science related to antibiotic resistance at WRRFs. It highlights the following take home messages:

*Antibiotic-resistant bacteria (ARB) and ARGs are widely detected, including in natural environments and food, but their associated human health risks remain poorly understood and inadequately characterized.

*The risk of getting infected by ARB is not greater than the risk of getting infected by the same antibiotic-susceptible bacterium. Humans are exposed to millions of microbes with antibiotic-resistant traits every day via natural and necessary activities, such as the ingestion of water and food (Pepper et al., 2018). Most of these exposures do not cause infections.

*Antibiotic-resistant bacteria and ARGs are detected at WRRFs, but treatment processes, including coagulation, clarification, filtration, disinfection, and anaerobic digestion, generally reduce their levels.

*The Global Water Pathogen Project (2019) estimates that conventional WRRFs reduce the types of ARGs observed and their numbers in raw wastewater by approximately 33% to 98%. Though some ARGs and mobile genetic elements (such as integrons) are not reduced.

*Current practices for wastewater and municipal drinking water treatment are adequate to prevent enteric bacterial infections from ARB via drinking water.

*Workers at WRRFs could be exposed to ARB and ARGs through contact with wastewater, solids, and bioaerosols. The associated risks are uncertain but can be mitigated by following the worker safety recommendations of the CDC (n.d.-a) and WEF (2020).

*Wastewater-based surveillance is an emerging approach to complement public health data, but is not intended to inform risk assessment from wastewater exposure.

*Water resource recovery facilities are important critical control points and are one of the most effective means of removing or reducing the occurrence of ARB and ARGs in wastewater and the environment.

In 2022, Allison Bell from the City of Minneapolis presented on the City's efforts to implement a new Green Infrastructure program into the public works team at WEFTEC. This presentation serves as a follow up on some of the progress that the City's program has achieved by featuring a success story from one of the city's most environmentally underserved communities. Several proposed street improvement projects entering the design and community outreach phase of planning has spurred the City of Minneapolis to leverage the opportunity to incorporate and optimize green infrastructure (GI) in conjunction within these projects. These projects were also all located within the Minneapolis South Side Green Zone (SSGZ). Minneapolis Green Zones are communities that have been identified as historically affected by environmental pollution, structural racism, and other forms of marginalization, that the City is prioritizing future efforts to achieve environmental justice. The SSGZ community has identified boosting GI, tree canopy, and green jobs as major elements that would contribute to the work to improve the conditions they experience. In 2022, the City partnered with HR Green to work with the SSGZ Council, community members, and the City's transportation design teams to understand, prioritize, and maximize the impacts the future transportation projects could have in the area. This effort focused on two of the upcoming projects ahead of a much larger study of the entire zone. Minneapolis and HR Green chose to take a different approach than in the past: to navigate working with an over-burdened community in such a way that does not increase the burden and allows for effective input. Sometimes this meant acknowledging historic racism in the development of the roads in the area, and sometimes this meant translating how city and engineering priorities aligned with community feedback. The community and the city worked together to develop goals and priorities for GI in this area. The project team made recommendations to incorporate GI within the road projects that aligned with the goals and priorities. They analyzed feasibility, impact, and costs, and laid out a plan for implementation and funding. In this presentation, we will walk through how we learned to work with the community, how to best listen and incorporate needs, and how to communicate and inform community members. We will also discuss the GI optimization work and how we translated community-driven priorities and city water quality priorities into project recommendations. Following the completion of this phase of GI prioritization, the City continued its partnership with the Mississippi Watershed Management Organization to fund the implementation of green infrastructure practices identified and prioritized in this study. Future expansions of this study into additional Green Zone locations are expected to take place during 2024.

Introduction As population growth, urbanization, and climate change intensify pressures on water resources, utilities are faced with an increased urgency for advanced water treatment (AWT) solutions and a need to enhance resilience against evolving climatic conditions. Concurrently, wastewater resource recovery facilities (WRRFs) are faced with increasingly stringent nutrient discharge limits that surpass the capabilities of conventional treatment methods. Consequently, utilities are compelled to adopt innovative approaches to address the quality and quantity of water supplies while ensuring regulatory compliance and sustainability. In this work, we highlight case studies of two forward-thinking utilities, distinguished by geographical contexts and unique drivers, yet united by a commitment to advance climate change adaptation strategies, achieve ultra-low nutrient limits, and integrate holistic one water initiatives. Metro Water Recovery (Denver, CO): Upcoming Colorado water quality regulations are set to impose stringent stream standards, notably 2.01 mg/L for total nitrogen (TN) and 0.10 mg/L for total phosphorus (P) on WRRFs, including Metro Water Recovery's Robert W. Hite Treatment Facility (RHWTF) and Northern Treatment Plant (NTP). AWT technologies like carbon-based advanced treatment (CBAT) schemes (e.g., coagulation/flocculation/sedimentation (floc/sed), ozone (O3), biofiltration (BAF), and granular activated carbon (GAC)) may address stringent nutrient limits while also aligning with Direct Potable Reuse (DPR) requirements. A study was initiated to: 1) assess the treatability of dissolved organic carbon (DOC), dissolved organic nitrogen (DON), and soluble non-reactive phosphorus (sNRP) using CBAT technologies; and 2) discern the capabilities of CBAT in concurrently achieving nutrient limits and DPR compliance. Evaluation of nutrient removal through tertiary CBAT processes spanned full-scale applications (floc/sed at NTP and BAF/floc/sed at RHWTF's Denver Water Recycling Plant (DWRP)) and pilot-scale (O3 only, BAF only, and O3/BAF at RHWTF), supplemented by bench-scale floc/sed (jar testing) and GAC evaluations (rapid small-scale column tests). Parameters such as O3 dose and empty bed contact times aligned with potable reuse standards. While full-scale floc/sed/filtration at NTP (Figure 1; Figure 2) and DWRP (Figure 3, Figure 4) (~20 mg/L alum) effectively managed particulate P and sNRP removal, it did not meet DOC and DON targets for Direct Potable Reuse (DPR) applications. CBAT testing showed potential for control of DOC and DON, albeit with the need for multiple potentially costly unit processes. The GAC runtime (up to 3,500 Bed Volumes for DOC and DON targets) was notably extended through enhanced upstream treatment. While floc/sed processes achieved comparable DOC and DON removal rates (up to 40% each) at the expense of elevated coagulant doses (80 mg/L Ferric chloride), O3/BAF treatments realized a modest 26% reduction in DON. Future pilot efforts aim to assess the efficacy of a comprehensive CBAT treatment train, inclusive of tertiary denitrifying BAF, to fulfill TN requirements and optimize DPR suitability. AWT Utility (Midwest): A midwest AWT utility has seen significant population growth in recent years and is estimated to double by 2040. Rapid growth and a desire improve the health of the receiving water body have urged the utility to consider alternative water supplies. Subsequently, the utility commissioned a CBAT pilot consisting of O3, two-stage BAF, GAC, and UV advanced oxidation process (UVAOP). The objective of this study was to pilot CBAT technologies to demonstrate the ability of AWT process trains to produce high quality finished water that meets stringent water quality targets. This study utilized a multi-barrier scheme of O3/two-stage BAF (aerobic/anoxic) to meet low TN limits. Filters were operated in several phases (Table 1) until effluent quality targets were met (TOC < 3 mg/L, TN < 2 mg/L, contaminants of emerging concern (CECs)- meet MCLs) and steady-state was achieved. Select operational parameters were varied during each phase and the resulting water quality surrounding the first anoxic BAF (BAF 3) is shown in Figure 8. Table 2 shows the effluent DO, nitrate (NO3-N) concentrations and corresponding % NO3-N removal achieved across each anoxic BAF. Results indicate that when supplemental carbon and upstream feed DO levels were controlled, anoxic BAF 1 established and maintained anoxic conditions and achieved NO3-N removals up to 60% with anoxic BAF 2 acting as a polishing biofilter (%NO3-N removal ~30%). When supplemental carbon and upstream DO quenching chemical doses were reduced, anoxic BAF 1 turned into a sacrificial BAF, consuming excess DO and displaying poor nitrate removals (~15%), while anoxic BAF 2 became the dominant anoxic biofilter (> 60% NO3-N removal). Piloting efforts demonstrate how a modified CBAT train may simultaneously meet low TN targets (< 2 mg/L) and produce high quality product water. Conclusion Case studies at Metro Water Recovery and a midwest AWT utility demonstrate CBAT's potential for improving finished water quality for reuse and meeting ultra-low nutrient discharge requirements. Project findings provide first guidance on how WRRFs can adjust operational setpoints using CBAT process infrastructure to meet DPR or discharge water quality requirements in ecologically sensitive and drought-prone watersheds.

Introduction: UV disinfection systems have gained popularity in wastewater disinfection applications as they can inactivate microorganisms while avoiding the injection of a chemical and any risk of a high disinfectant demand or disinfection byproducts. UV disinfection process design must account for UV Transmittance (UVT) which is a critical parameter that characterizes the ability of UV photons to pass through water and reach a microbiological target. Monitoring of UVT is achieved by online or benchtop readings, but online data can be skewed by sensor drifting or water quality impacts. Black & Veatch worked with two wastewater facilities where UVTs <55% were observed and employed machine learning to analyze correlations between measured UVT and various water quality parameters including carbonaceous biological oxygen demand (CBOD) and total organic carbon (TOC). UVT prediction allows for historical data to be verified whether the sensor was reading correctly or for optimization of UV system operation. Materials and methods: This study collected UVT and additional water quality data from each respective treatment facility secondary effluent at various sample collections intervals over the last 5 years. UVT was collected with online and benchtop instruments while other water quality data were collected via analytical methods accepted by 40 CFR criteria. Data cleaning and analysis was performed in R using various open-source packages and algorithms. Results and discussion: Review of Industry Guidance. Although there is no EPA requirement of a minimum design UVT for wastewater disinfection, guidelines have been followed in various states. The 2012 NWRI Guidelines set minimum allowable UVTs for wastewater applications based on the type of upstream treatment with a 55% minimum for applications with media filtration (REF2). In addition, 10 States standards recommends UV disinfection in wastewater be limited to effluent UVTs greater than 65% (REF3). However, UV disinfection has been implemented in states across the US with UVTs of 55% or lower, where various benchtop and full-scale data supports viable inactivation of microbes relevant to each projects operating permit. This study considered two facilities which are known to produce lower UVTs than conventional nitrifying treatment, Pure Oxygen Activated Sludge and Trickling Filter, from projects in Michigan and California, respectively. Machine Learning Techniques. Machine learning consists of algorithms and statistical models to analyze and draw inferences from patterns in data and can be utilized for various applications relevant to water treatment. This study reviews industry accepted techniques for employing machine learning for numerical predictions models based on multivariate regression and provides an in-depth review of the two algorithms employed in this work, Random Forests (RF) and Support Vector Regression (SVR). Case Study 1. A pure oxygen activated sludge treatment facility in Michigan undergoing a disinfection system evaluation was analyzed to consider UV disinfection to replace previous disinfection systems using sodium hypochlorite and ozone. Black & Veatch implemented an online UVT probe for a period of 12 months where the plant experienced various low UVT trends (<50%) that were impacted by ferric chloride addition, expected industrial source discharges, and sensor drifting. RF and SVR machine learning algorithms were employed to predict UVT based on CBOD, Solids and Temperature. Model results were successful in predicting UVT with an R mean squared value (RMSE) of 0.84 and 0.83, respectively (Figures 2 and 3). To mitigate the impact of excessive drifting of the online UVT probe, the model was further refined to predict periods where the UVT probe may have drifted out of calibration. Outcomes of these predictions could help promote instrument calibration or ensure historical data is accurate and whether or not it should be included in further analysis for process design of a UV disinfection system. Case Study 2. A regional wastewater facility in California undergoing a plant upgrade to employ UV disinfection for Title 22 non-potable reuse was also evaluated. As a part of process design and commissioning of the new Title 22 UV disinfection system, Black & Veatch analyzed 2+ years of water quality data where UVTs less than 50% were observed, which has been documented for trickling filter secondary effluent (REF4). Upstream trickling filter backwashing events were thought to have especially produced organic loads which impacted the UVT sensor and may have altered data collection after the system upset had already passed. TOC and TSS data were used to train the RF and SVR models to predict UVT across the monitoring period, with the SVR achieving a higher success in prediction with an RSME of 0.86 (Figures 5 and 6). Conclusions: 1.Applications where UVT is <55% can be managed contrary to some guidance and provide effective disinfection. 2.Machine Learning can verify analyzer trends to identify correct/incorrect historical data and ensure appropriate process design. 3.Machine Learning can be integrated with control approaches to accelerate response of UV disinfection systems based on anticipated water quality. 4.Multivariate water quality constituent regression could be paired with UV validation equations to predict performance and improve understanding of disinfection operations.

INTRODUCTION Water is key at every step of the lithium ion battery life cycle. This paper discusses four case studies involving the use of novel reverse osmosis (RO) membrane processes and energy recovery devices (ERDs) for lithium related water reuse, zero liquid discharge (ZLD), and resource recovery applications in China. The cases include several key stages of the li-ion battery life cycle including lithium brine mining, battery manufacturing, and battery recycling and how RO and ERDs are used to add value within these applications. 1. RO Related Trends for Industrial Wastewater Zero Liquid Discharge in China China has made water conservation and environmental protection key priorities and is ramping up regulations around wastewater discharge, limiting both the concentration of contaminants and discharge volumes. Industrial wastewater treatment is a crucial, but oftentimes expensive process. ZLD is becoming a requirement in many highly polluting industries. An example in the lithium industry is battery manufacturing, which includes many facilities that have been required to implement ZLD to prevent the discharge of certain contaminants and nutrients into the environment. The first case study will discuss and present data for a lithium battery manufacturing facility in central China that implemented ultra-high pressure reverse osmosis (UHPRO) operating at 1,500 psi with new UHPRO energy recovery devices (ERDs) to reduce energy use when implementing ZLD and resource recovery. The waste streams contain primarily ammonium sulfate, a valuable fertilizer sold as a byproduct. Recovering ammonium generates sufficient revenue to cover the ZLD system operating costs and eliminates a harmful discharge into the environment. 2. RO Related Trends for Lithium Mining in China Western China has significant amounts of lithium in salt lakes and in brines located in subsurface geological deposits. Some of the salt lakes in Tibet have low concentrations of magnesium and other divalent salts that can make it more challenging and expensive to extract lithium from the brine. In these locations, evaporation ponds are used to concentrate the brines and eventually precipitate out different salts into different ponds to allow the separation of monovalent salts so that when lithium bicarbonate (Li2CO3) precipitates, it is of sufficient quality for some lithium ion battery manufacturing. However, demand is growing for high purity lithium to help make higher quality cathodes. In the Qinghai province, there is more lithium in salt lakes and subsurface geological brines than in Tibet; however, the chemistry of these brines makes lithium extraction more challenging and expensive to implement with evaporation ponds, thus direct lithium extraction (DLE) is required. Novel nanofiltration (NF) and RO membranes are becoming common as tools to improve lithium quality and/or to increase lithium production in both of these mining applications. The second case study will discuss and present data from a lithium brine mining project in Tibet China that uses osmotically assisted RO (OARO) and ERDs to generate high-purity, battery grade lithium. The purity is improved by a OARO process designed to separate key monovalent salts, while also reducing by half the time it takes to concentrate lithium bicarbonate (Li2CO3) using evaporation ponds in an environment not ideal for solar evaporation. The third case will discuss and present data for a combination of low pressure RO, seawater RO, and UHPRO membrane systems with ERDs at a direct lithium extraction (DLE) facility at a salt lake in the Qinghai region of China. The RO systems concentrate lithium chloride (LiCl) downstream of an ion exchange based DLE system and upstream of a thermal evaporator used prior to conversion from LiCl to Li2CO3. UHPRO was added during a plant expansion to reduce the cost per ton of Li2CO3 from one of the first commercial DLE projects in the world. 3. RO Related Trends for Lithium Recycling in China In Europe and North America, various startups are conducting research and development (R&D) to demonstrate and commercialize recycling of lithium ion batteries to recover lithium and other key components for reuse. In China, however, the government has put the responsibility of recycling batteries onto the makers of EV materials such as automakers and/or battery manufacturers. While RO membranes are used to concentrate lithium chloride at battery recycling facilities in the US, it is not yet common and R&D is ongoing. In China, however, the use of RO systems for battery recycling is already common and a unique process has been developed to separate and concentrate lithium, nickel and cobalt with RO membranes prior to further processing to recover battery grade material. The fourth case study will be on a lithium battery recycling facility in China that is using a unique combination of pretreatment and a single RO system with ERDs designed for a unique operating strategy to recover lithium chloride, lithium sulfate, nickel sulfate, and cobalt sulfate from recycled batteries that include manganese and other challenging constituents prior to additional refining to recover lithium, nickel and cobalt for reuse in batteries.

BACKGROUND Silver Springs, located in North Central Florida, is one of the state's largest first-magnitude springs and has attracted visitors since the 19th Century. World famous for its crystal-clear waters, it is the ecological and economic engine in the area. However, flow and water quality data over the past nine decades show a significant decline in spring flow and increase in nutrient concentrations which has led to the ecological degradation of the Silver Springs and Silver River systems. OBJECTIVES While not yet required by regulation, the visionary City of Ocala, located within the Silver Springs springshed, constructed a treatment wetland designed for groundwater recharge to beneficially reuse their reclaimed water by offsetting their groundwater use and nutrient loads to Silver Springs associated with municipal wastewater management. Known as the Ocala Wetland Groundwater Recharge Park, this 35-acre infiltration wetland system receives and treats up to 5 million gallons per day (mgd) of reclaimed water and stormwater to recharge the Upper Floridan Aquifer (UFA), protects water quality, and recovers and enhances the flows to Silver Springs. The Silver Springs system is subject to restrictive Total Maximum Daily Load (TMDL) regulations for nitrate and has a recovery strategy to help meet its established Minimum Flows and Levels (MFL). The Ocala Wetland Groundwater Recharge Park project supports both nitrate load reductions and recharge to help augment flows in the springshed. The Florida Department of Environmental Protection (FDEP) listed the wetland park as one of the stakeholder projects to reduce nitrogen sources in the Silver Springs Basin Management Action Plan (BMAP) area and provided Springs Funding due to its benefit to the region (FDEP, 2012 and SJRWMD, 2017). METHODOLOGY In support of the design and permitting of this project, an onsite hydrogeologic investigation, consisting of soil borings and the construction of pumping and monitoring wells across the site, was conducted to produce site-specific data. A groundwater model was then calibrated to this site-specific data and was used to evaluate the site's capacity to recharge the aquifer and the fate of the applied water to recover flows in the Silver Springs System. These efforts included innovative applications of a calibrated groundwater model combined with a wetlands treatment model to quantify recharge while ensuring the protection of water quality. It was determined that this system would have a capacity of up to 5 mgd, infiltrate an average of 5 in/day, and reduce nitrate levels to background concentrations. The designed wetland system consists of 35 acres of infiltration wetlands divided into 3 cells to receive up to 5 mgd of reclaimed and stormwater on a project area of 60 acres. The design included organically shaped cells graded in-place without the need for import of export of material to construct berms. Wetland habitat diversity was maximized by creating different ecotones across the cells that range from deep open water to shallow wetlands, islands, and rookery areas. The design also included an innovative distribution header that controls flow to each cell independently based on water level setpoints in each wetland cell. This allows for seasonal operation of water levels to maximize recharge and wetland ecological value by mimicking wetland hydroperiods that are driven by seasonal rainfall patterns. RESULTS AND CONCLUSIONS As shown in Figure 1. nitrate concentrations in the monitoring wells located within the UFA, approximately 100 feet below the wetland park, show a downward trend following park start-up and wetland planting. Nitrate concentrations in the intermediate well (within the influence of the wetland) decreased from 0.5 mg/L to 0.1 mg/L and nitrate concentrations in the compliance well decreased from approximately 1 mg/L to 0.5 mg/L after the application of reclaimed water to the site and start-up of the park. In addition, onsite recharge rates average 5 in/day, achieving the infiltration rates predicted in the groundwater model (Figure 2). The Ocala Wetland Recharge Park provides a unique case study of beneficial reuse management that addresses water supply and water quality while also giving back to the community. Since opening in the September of 2020, the park has seen over 171 bird species and an average of 3,700 visitors per month. Designed to also serve the community, the Park includes 2.5 miles of ADA-accessible trails, interactive educational displays, and some of the best birding in the County as the park was designated a Great Florida Birding and Wildlife Trail site by the Florida Wildlife Commission in 2023. The City has also developed a website and social media for the wetland park to provide the public with park photos, activities, and educational information. Further serving as an amenity to the community, the park also hosts field trips for local schools and meetings for environmental organizations like the Marion Audubon Society. In 2021, the wetland recharge park's innovation was recognized by the National Recreation and Park Association as they awarded the park with both the Innovation in Conservation Award and the 2021 Best in Innovation Award. The park represents a multi-benefit nature-based solution that should be considered for other areas in need of addressing both water supply and water quality in an innovative and natural way.

Introduction Coastal regions globally are experiencing the growing manifestation of the effects of climate change, where the intensified frequency and severity of storm events, along with the rise of sea levels, pose escalating threats to communities, infrastructure, and ecosystems. It is in this context that nature-based solutions, often referred to as 'green infrastructure,' have emerged as sustainable and adaptive measures to counter the multifarious challenges arising from coastal vulnerability. The challenges and lessons learned from three living shoreline projects from around the country includes: Lister Park Project (LPP) on the south shore of Long Island, NY; Clover Island Shoreline Restoration Project (CISRP) at the Port of Kennewick along the Columbia River in Kennewick, WA; and Miami-Dade County (MDC) Living Shoreline Project in southeast Florida. Objectives This presentation will gain insight on lessons learned from three nature-based solutions projects in three separate geographies and environments. Seamlessly integrating flood protection, habitat restoration, and public access along the Mill River waterfront, the LPP addresses multifaceted impacts of climate change with a focus on community engagement. Simultaneously, the CISRP aims to overcome ecological challenges from historical waste concrete deposition, emphasizing biodiversity and shoreline stabilization through the creation of a strategically designed submerged bank for juvenile salmon. The MDC Living Shoreline Project initiative seeks to navigate regulatory complexities, developing a Living Shorelines Guidance Document for nature-based solutions. Status Construction of the LPP was completed in December 2023, the CISRP was completed in May 2023, Methodology The LPP integrates living shorelines-a nature-based design alternative employing a blend of green and grey solutions to combat erosion while concurrently promoting the restoration of vital ecosystems along a tidal river. This 5,500 LF living shoreline was meticulously designed to encompass a variety of riverbank conditions, serve as a buffer against both routine and extreme flooding events, thereby protecting the community and its assets. The CISRP confronts substantive ecological challenges stemming from the deposition of concrete waste along its shoreline. This has precipitated adverse effects on the habitat for federally listed species including juvenile salmon, which necessitated prompt and comprehensive restoration initiatives. The project's objective is to surmount these challenges through the systematic creation of a strategically designed submerged bank tailored to the precise requirements of juvenile salmon. Concurrently, the project addresses the stabilization of the shoreline, mitigating the effects of concrete deposition, and the establishment of riparian habitats fostering biodiversity. The MDC Living Shoreline Project involves the development of a guidance document poised to assist public and private entities in securing funding opportunities, navigating regulatory complexities, and incentivizing living shoreline creation through time and cost savings. Despite the recognized ecological benefits of living shorelines, challenges arise from perceived regulatory complexities. MDC, having undertaken multiple living shorelines projects on public lands, faces concerns over onerous regulations, prompting calls for changes in relevant acts and codes. Findings and Significance For the Lister Park Project, the design team encountered challenges necessitating adaptive solutions, such as the potential impact on existing utilities, change in conditions, and constraints of budgetary allocations precipitating iterative adaptations throughout the design and construction process. Additionally, existing conditions from when the living shoreline was surveyed to when construction began drastically changed due to the continual shoreline erosion. The CISRP stands as a testament for ecological sustainability, envisioning harmonious coexistence between industrial progress and environmental conservation on Clover Island. The MDC Living Shoreline provides a valuable resource for stakeholders involved in shoreline development and conservation within the county. These three projects emphasize the significance of adaptive strategies, tailored designs, and regulatory considerations in effectively implementing nature-based solutions to combat the multifaceted challenges of coastal vulnerability.