Introduction Alternative delivery methods in the water and wastewater market are proven to provide owners with value added and risk reducing approaches for executing capital projects. These delivery approaches are often associated with large utilities completing projects with hefty budgets. However, the same approaches can have equal, if not greater, advantages to small utilities providing resources for limited staff, minimizing design changes, and saving time and money. Objectives The primary objective of this case study is to investigate the benefits and challenges of alternative delivery implementation at two small wastewater utilities. The City of Fruita, Colorado (Fruita) conducted two construction manager at risk (CMAR) projects on their wastewater system in 2023 for a total construction budget of approximately $3.0M. The City of Laramie, Wyoming (Laramie) is currently conducting their first CMAR project for their wastewater utility. Both utilities struggle with similar issues complimentary of the CMAR approach: 1) Technically understaffed for wastewater capital project execution 2) Budgetary victims of ever climbing cost of work, 3) Location and project size limit contractor interest in open bid opportunities Status Fruita took a unique approach to alternative delivery. Located approximately four hours from any major metropolitan area, Fruita found it difficult to entice contractors to pursue projects delivered with a traditional design bid build (DBB) method. As such, Fruita selects an on-call CMAR firm every five years and issues work packages with negotiated guaranteed maximum prices (GMPs) to address their on-going capital improvements program. In 2023, Fruita conducted two CMAR work packages — replacement of their oxidation ditch aeration grids and collection system improvements to mitigate hydrogen sulfide (H2S) generation (H2S project). The on-call CMAR contractor commenced work with a pre-construction contract at, or around the 30% design level to provide value engineering, constructability review, cost estimating, and scheduling. Both projects included critical construction sequencing operations with significant cost ramifications. For example, the H2S project included significant bypass pumping associated with manhole replacement. The engineer, CMAR contractor, and Fruita collaborated early to determine exact manhole designs and construction sequence of operations to minimize bypass pumping time. The resulting construction was completed approximately 25% ahead of schedule and under the GMP. Cumulatively, Fruita was returned approximate $400k in deductive change orders from the CMAR contractor from the $3M GMPs. Laramie has traditionally delivered their capital projects in a DBB method — selecting the low price bidder without direct attention to qualifications. Like Fruita, Laramie is understaffed and has budgetary restrictions. Low bid DBB projects were found to be taxing the already overstretch engineering staff to their limits on ability to deliver projects on time and under budget. Laramie's first CMAR project is the West Laramie Main Lift Station Replacement with construction anticipated to begin in the summer of 2024. Originally budgeted for a mere $2.0M, Laramie realized the breadth of their project goals could not be accomplished with their budget. As such, the engineer, selected CMAR, and Laramie began the value engineering process early in the design phase to find options to meet Laramie's goals within an attainable budget. This started with a 'wants, needs, and must haves' workshop identifying scope elements to be included in the project. Considerations on phasing, alternate materials of construction, and facility location adjustments led the team to lock in on an overall design meeting Laramie's goals and budgetary restrictions. Findings and Significance Several key takeaways will be discussed for session attendees. 1) Partnerships between contractor, engineer, and owner are key. While alternative delivery is an excellent approach to delivering projects for small communities, effective working relationships are vital. A healthy balance of support and doubt between the engineer and contractor allow for best value approaches to emerge successfully. Similarly, owner trust in the design process allows for vetting of many options providing value. 2) Contractor and engineer experience in alternative delivery is vital to success of the project. Limited owner staff with limited alternative delivery experience requires more attention to the design and construction process from trusted engineering and contractor teammates. Ideally, engineer and contractor have past relationships (for CMAR delivery). 3) Begin GMP development early to mitigate late-stage design modifications. Regular cost model check-ins are helpful to make sure the project is keeping within budget. Laramie's pause and realignment happened following 30%, minimizing design changes and extra project cost.

Introduction Mesophilic Anaerobic Digestion (MAD) is commonly used in larger WRRFs to stabilize solids and generate biogas for heat/energy (CHP) or injection into natural gas pipelines (RNG). The benefits of acid digestion ahead of MAD and post-aerobic digestion (PAD) after MAD have been generally understood and implemented at several facilities to improve operations. Those two MAD 'add-ons' had traditionally been only used independently. However, some very interesting and useful outcomes develop when a recycle loop is employed to send nitrite from the nitrifying PAD to the Acid Reactor for denitrification. Process Background More frequently discussed in the nutrient removal world, the presence of nitrate makes a reactor 'anoxic' not 'anaerobic'. The nitrate-laden recycle from the PAD helps the Acid Reactor by increasing pH, reducing corrosivity and creating optimal conditions for hydrolyzing bacteria. Because of this, the methanogens in the anaerobic digester are more efficiently able to produce more biogas with a higher methane content. The nitrates present in the Acid Reactor are denitrified in a reaction that is biologically and energetically preferred over sulfate reduction. Nitrate has been used to control odors within sewers, at headworks and elsewhere by suppressing the population of sulfate-reducing bacteria (SRBs). Within the world of anaerobic digestion, the nitrate pathway serves to significantly decrease the concentrations of Hydrogen Sulfide (H2S) in the biogas. Because of the recycle, the effects of the nitrification-denitrification occurring within the biosolids treatment process decreases the concentration of ammonia within the anaerobic digester. Since both ammonia and H2S can be inhibitory to methanogens, lower concentrations contribute to increased biogas production. Pilot Studies Recent pilot studies at several facilities in Indiana, California, Arizona and Michigan have shown some consistent and significant results that are summarized here. Additional data and discussion will be provided in the paper and presentation: H2S concentration in the biogas was consistently reduced by at least 90%, without the addition of ferric chloride or other chemicals, which would significantly extend the life of H2S removal systems and reduce odor and corrosion challenges and lower chemical costs. Biosolids mass (and hauling costs) are reduced in at least four cumulative ways: Increased volatile solid (VS) destruction, No metal salt precipitates, improved dewatering, and decreased liquid-stream solids production (through reduced loadings in dewatering return flow). Since pH is lowered and ammonia concentrations are lower, the stoichiometry is not conducive to struvite formation. Ammonia and H2S toxicity on methanogens is reduced. The combined effect of increased VS destruction and a richer (higher methane %) in the biogas results in a significant (~10%) increase in the net energy yield from the digesters. Dewatering significantly improved with added VS destruction and because aerobic biology more effectively breaks down the Extracellular Polymeric Substances (EPS) produced by cells during anaerobic digestion. In one pilot study, coagulant was eliminated, polymer dose dropped and the dewatered cake achieved 32% total solids. Nutrient control within the solids process eliminates the need for additional sidestream tankage, heating and additional processes. Conclusion The recycle from the PAD to the Acid Reactor promotes the nitrate pathway over less favorable (sulfur) pathways. Through reduced chemical use, optimized digester chemistry and biology, increased solids destruction, enhanced methane production and other consequential benefits, the capabilities of this process offer savings and solutions for several common MAD challenges. By harnessing the power of biology in creative ways, the entire anaerobic digestion system becomes more robust and resilient: less reliant on chemicals and external inputs.

Introduction At WEFTEC 2019, data from one year of operation of a newly built sidestream fermenter for a biological phosphorus removal (BPR) system was presented. This paper covers the first 5 years of operation of the Wakarusa River wastewater treatment plant (WWTP) at Lawrence, Kansas. New processes are always scrutinized by the industry. Was the pilot operation a fluke? Can its performance be repeated? Is the system lightly loaded? Is the process resilient and reliable? Data from the last 5 years shows that sidestream fermentation is reliable, but there were periods of degraded performance. The Wakarusa River WWTP was designed to treat 2.5 mgd (9 500 m3 /d) annual average flow of domestic sewage. The Wakarusa facility is essentially a new train located at another site for the Kansas River WWTP. Flow to Wakarusa has averaged about 2 mgd over the 5-year period (80 percent of the design capacity). The Wakarusa Facility is a 3-stage Bardenpho process with a flow-through anaerobic zone, an anoxic zone, and an oxidation ditch for aerobic treatment plus a sidestream fermenter for enhanced biological phosphorus removal (EBPR). The raw influent to Wakarusa is fairly 'fresh' with a little VFA (12 mg/L) and a low rbCOD to TP ratio (50% of the time less than 13.5). Not enough rbCOD was available for good BPR performance. The Bad: Impact of Return Flows on EBPR Performance Figure 1 shows the effluent orthophosphate (OP) concentrations from an online analyzer, and effluent total phosphorus (TP) concentrations from operator collected data and 24-hour composites for 2019. This graph contains over 150,000 data points from the on-line analyzer. Figure 2 shows the 30,000 points spanning from Nov 2019 to Sept 2020 and it is much easier to see the periods of good effluent from the not so good effluent quality. The permit limit is 1 mg/L TP on a 365-day rolling average. The Figure 1 graph show periods, highlighted by the pink transparent boxes, of high effluent P coinciding with periods when biosolids land application was delayed by excessively wet fields. This pattern repeats each year. Solids build up in the plant MLSS (or system increased SRT) and the basin MLSS concentration rises significantly which interferes with sidestream fermentation efficiency. A process model was developed in SUMO (Dynamita) to simulate the plant performance at increasing SRT conditions. Model simulations indicated that the VFA production in the fermenter decreased as the SRT in the activated sludge basin increased while maintaining a constant flow to the fermenter. Model simulations are continued to further explore this phenomenon to determine if operational conditions can improve fermenter performance. In 2022 there was an upset between Sept and Nov in system performance. The centrifuges had been in operation for 4 years and erosion/ wear of internals resulted in poor solids capture. The net result was poor BPR performance in Sept through Nov of 2022, highlighted on Figure 1. Poor solids capture resulted in the recycling of high concentrations of BOD, TSS and TP to the plant influent (Figure 3). Once the centrifuges were repaired and solids capture was under control, the effluent OP and TP returned to very low concentrations. After 5 years of operation, no ferric chloride has been added nor has there been any supplemental addition of a carbon source. After the high inventory of MLSS was reduced, the fermenter bounced back and produced a very low effluent OP concentration. The Good: Impact of Low DO Operation on TN and TP Removal Performance and Microbial Ecology Figure 4 shows the nitrogen profile in the system during the summer of 2022. The abrupt decline in the effluent nitrate concentration was intentional. The facility has two online DO probes located in the outer curve and the inner curve of the ditch system. The DO setpoints were initially set at 0.8 mg/L and 0.5 mg/L during start-up and during the summer of 2022 plant staff lowered the DO setpoints to around 0.2-0.3 mg/L. Effluent nitrate concentrations dropped to below 1 mg N/L. The effluent phosphorus concentration remained very low (Figure 1). During the July — August 2022 timeframe, the effluent OP and TP concentrations remained very low. Near the end of this trial period, centrifuge performance began to deteriorate and excessive solids in the system interfered with good BPR. These results indicate that low DO operation did not have a negative impact on phosphorus uptake as well as nitrification. As the DO setpoints were lowered, the AOB (ammonia oxidizing bacteria) population declined and the population of Commamox increased. Recent studies demonstrated the prevalence of Comammox Nitrospira can be dominant ammonia oxidizers in a mainstream low DO nitrification reactor. The Good: Impact of Fermenter SRT on VFA Species and PAO/GAO Population A study performed by University of Kansas on fermenter SRT and operating parameters showed the impact of SRT on the quantity of VFA formed and the diversity of VFA species (Figure 5). Acetic acid is still the predominant VFA present in the fermenter effluent. Figure 6 shows the PAO versus GAO as a fraction of the overall microbial population in the anaerobic zone. Very few GAOs were present in the system. Summary The sidestream fermentation process has been reliable and consistent in producing a low effluent OP concentration while at plant loading of 80% of design capacity

Silicon Valley Clean Water (SVCW), a water resource recovery agency in California, is nearly complete with its major infrastructure and conveyance upgrade program that used the progressive design-build (PDB) delivery for three interrelated projects valued at $569MM USD. This program, the Regional Environmental Sewer Conveyance Upgrade (RESCU), was implemented to replace SVCW's aging conveyance system and improve preliminary treatment facilities. Since 2016 when the program was initiated, SVCW has been an early adopter of PDB delivery for major wastewater infrastructure and has been focused on learning and sharing lessons learned to improve PDB delivery for the wastewater industry. This paper/presentation is intended to continue the sharing of lessons learned about PDB delivery for water/wastewater infrastructure projects throughout design, construction, startup and commissioning to better educate others who are considering and/or implementing PDB delivery for similar projects and programs. RESCU Overview: SVCW's RESCU program consists of numerous projects; however, the following three large CIP projects are at the heart of the program and account for over $569MM USD of construction cost:

*The Gravity Pipeline Project constructed a new gravity sewer pipeline [approximately 5,200 meters (17,000 linear feet) and 3.4-meter (11-foot) inside diameter], using a tunnel boring machine, that will serve as the main wastewater conveyance system to the treatment plant. Approximate project value is $264MM USD.

*The Front-of-Plant project constructed a new deep influent lift station [approximately 27.5-meter (90-feet) deep, 300,000 m3/d (80 mgd) capacity], located at the terminus of the Gravity Pipeline, and preliminary treatment facilities and connection piping to SVCW's main WRRF. Approximate project value is $169MM USD.

*The Pump Station Improvements Project is rehabilitating three of SVCW's conveyance pumping stations and portions of force main that contribute the flow to Gravity Pipeline. Approximate project value is $136MM USD. See Figure 1: RESCU Overview; Figure 2: Front-of-Plant. RESCU Program Timeline and Highlights: In 2016, SVCW began exploring PDB delivery as a viable approach for these three critical projects due to schedule extensions related to the overall program implementation approach. Like many other agencies, SVCW had to learn a lot about collaborative delivery prior to initiating these projects and talked with other agencies nationwide, attended Design-Build Institute of America (DBIA) conferences, and received guidance from Owner's Advisors. In 2017 through 2019, SVCW worked through a rigorous procurement process to select PDB teams for each of the three projects. The process included a Request-for-Qualifications (RFQ) stage, qualification interviews, reference checking, short-listing of selected firms, a Request-for-Proposals (RFP) stage, a proposal process, additional proposal interviews, confidential meetings and reference site visits to previous projects. From 2019 through present, the PDB teams have been working through individual project designs (BODR, 30%, 60%), final cost negotiation, and construction processes, but were coordinated as a program. Because the same PDB team was selected for both the FoP and PSI project, coordination was simpler between those projects. When the COVID pandemic began, SVCW had already implemented MS Teams for the RESCU Program and quickly to remote meetings with minimal delays. Early work packages were used to accelerate critical elements of work or equipment (such as the tunnel boring machine), which proved to be advantageous just before the pandemic began. As construction progressed through final completion, it became evident that startup of facilities with overlapping responsibility (e.g. Gravity Pipeline and Front-of-Plant) would require careful coordination between PDB teams, which is currently underway. Learning Objectives: The primary learning objectives for the paper are to educate attendees on the 'real life' implementation of PDB process, with particular emphasis on programs that include multiple interrelated projects. Because many agencies still have limited knowledge of collaborative delivery, it is important for our industry to share knowledge from those who have recently implemented this type of project delivery. Although some elements of the RESCU program were presented at WEFTEC 2019, those lessons shared were primarily about procurement and pre-design phases. Now that the program is nearly complete five years later, this paper will focus on lessons learned through the entire PDB process, with particular emphasis on the recent construction and close-out phases (2019-2024) that have not been described yet. Lessons learned will be broken into the following main categories:

*Procurement Process

*PDB team procurement and selection

*Co-location of teams

*Collaborative design processes

*Negotiating lump sum pricing and cost validations

*Benefit of early work packages for construction and critical equipment/material procurement

*Agency involvement during construction (submittals, etc.)

*Equipment selection and procurement using best value

*Design, construction and startup of projects with 'overlapping responsibility'

*Planning for outreach/permitting

*Equipment and/or design issues during startup

*Navigating the COVID pandemic/supply chain issues

Introduction The application of the AquaNereda® process, were aerobic granular sludge (AGS) is applied in a sequencing reactor, is often seen as a replacement for the conventional activated sludge process. AquaNereda(R) is a sequencing process that utilizes a single tank for react and settle phases, and therefore is often not compatible as a retrofit with existing activated sludge systems that utilize separate tanks for reaction (aeration basins) and settle (final clarifiers). While this can be seen as a limitation for the application of AquaNereda(R), there is an opportunity to construct an expansion of facilities with AquaNereda(R), and then integrate the AquaNereda(R) in parallel to a conventional activated sludge plant. Four Rivers Sanitation Authority (FRSA), located in Rockford, Illinois, is currently working towards this integrated overall facility. While maintaining 40 mgd of average day flow capacity in a more conventional biological nutrient removal (BNR) activated sludge facility, FRSA is adding an additional 10 mgd of average day flow capacity with a new AquaNereda(R) AGS facility. The AGS facility will be operational in 2025, with the BNR upgrades being completed in 2026. During design of the new facilities at FRSA, the largest question for integration of the processes became how to manage the waste activated granular sludge (WAGS). Given the characteristics of WAGS in terms of percent solids as well as the sequencing wasting schedule from AquaNereda(R), it was decided to send the WAGS into the activated sludge system and then to waste to solids handling (see Figure 1 for a process flow diagram). The waste activated sludge (WAS) would then contain flocs from the activated sludge process as well as WAGS. This simplified operation, but there were major questions related to the impact of WAGS on the activated sludge process. Potential oxygen demand impacts, nitrification rates, and settling rates were all of interest to FRSA to understand the impact of WAGS. While most facilities would rely solely on process modelling to assess these impacts, FRSA has access to WAGS for testing. The AquaNereda(R) demonstration facility is on site and operating with FRSA wastewater. This facility (treating 200,000 gpd) generates WAGS that can be utilized for testing. Approach and Methodology To help understand the impacts and strategies to manage WAGS from the AGS facility, a series of bench scale tests were completed using WAGS from the AquaNereda(R) demonstration facility and WAS from the existing FRSA aeration basins. Three sets of bench scale tests were completed:

*Settling rate testing to identify potential enhanced settling, as outlined by Daigger, Redmond, and Downing (2017)

*Specific oxygen uptake rate (SOUR) measurement, utilizing standard methods, to assess the oxygen demand of the WAGS. The WAGS have the potential to exert a significant oxygen demand, as past work has shown a biomethane production potential of WAGS that is similar to primary sludge (Guo et al., Digestibility of waste aerobic granular sludge from a full-scale municipal wastewater treatment system, 2020).

*Nitrification rate testing, as outlined by Melcer et al (2003), to identify any potential seeding effect from WAGS. Results and Outcomes To evaluate the effect of WAGS on the settling characteristics of the existing waste activated sludge (WAS), batch settling experiments were performed using WAS and a mixture of WAGS-WAS at various dilution ratios to generate settling curves. The WAGS-WAS mixture proportions were calculated based on the predicted WAGS flows from the new AGS facilities. Figure 2 provides the settling rate impacts. Addition of WAGS increased the settling rate of the activated sludge biomass. The effect on settling rate would increase the peak flow capacity of the activated sludge facilities from 110 mgd to 130 mgd. SOUR testing indicated that the WAGS would have a 25% higher oxygen uptake rate than WAS (Figure 3). This indicates that there will be an oxygen demand associated with either particulate COD bound in the WAGS or potentially stored carbon. This oxygen demand is considered during aeration operation in the activated sludge system. The nitrification rate of WAGS (4 mgN/gVSS-hr) was similar to the nitrification rate of WAS (3.9 mgN/gVSS-hr). This was an unexpected result, as the WAGS likely contains a high VSS content of particulate COD from the influent. The benefit is that the WAGS will be adding a significant load of nitrifiers into the activated sludge system, increasing system resilience. The outcomes from this testing highlight how construction of an AquaNereda(R) facility in parallel to an activated sludge facility can provide a net benefit to the activated sludge facility. Applicability AquaNereda(R) has been sold as the evolution of activated sludge, but the requirement for a sequencing reactor can been seen as a limitation. The work completed highlights how an AquaNereda(R) process can be constructed in parallel to an activated sludge system, with positive impacts on the activated sludge facility. Audience Appeal Anyone looking at process expansion, nutrient removal requirements, and aging infrastructure would benefit from this presentation.

BACKGROUND King County is executing a Combined Sewer Overflow (CSO) Long Term Control Plan (LTCP) aimed at reducing CSOs into local water bodies and protecting public health and the environment. The Georgetown Wet Weather Treatment System (GWWTS) is one of 14 Consent Decree projects in the LTCP. The remote GWWTS improves the resiliency of the regional King County wastewater system by capturing and treating 95 percent of the CSOs at two CSO outfalls into the Lower Duwamish Waterway. The GWWTS will operate an average of approximately 20 times per year, processing about 265 megaliters (70 million gallons) of wastewater annually. Construction began in late 2017 and achieved substantial completion in December 2022. The GWWTS is located in a dense urban neighborhood (Figure 1) surrounded by residential housing, commercial businesses, and light and heavy industrial facilities. Georgetown is a close-knit community that is diverse and home to many artists. King County's goal was to design a station that not only improves water quality in the Lower Duwamish waterway but also builds community by addressing the County's equity and social justice goals. King County developed a proactive community engagement plan to design a facility that reflected neighborhood values. OBJECTIVES The objectives of involving the community in the design of the GWWTS were: (1) identify community goals, and issues, (2) align the project vision and goals to the needs and goals of the community, and (3) implement design features that address those needs and goals. METHODOLOGY Two plans were developed at the beginning of the project to take into account community needs, goals, and issues.

*GWWTS Design Phase Public Involvement Plan (PIP) — The PIP was developed to identify and provide a profile of community needs, goals, and issues. The issues of the community were identified through a variety of methods including feedback at community briefings and drop-in sessions, direct verbal and written input, and Design Advisory Group (DAG) comments.

*Equity and social justice action plan (ESJ plan) — The plan sought to have the project team improve the determinants of equity in the Georgetown neighborhood through project commitments that relate directly to known community values, regulatory requirements and sustainability actions. Community values identified were documented through conversations and interviews with community members, community survey results, meetings with a community DAG and the Georgetown Neighborhood Plan. Implementation of these plans extensively involved the Georgetown community in the design process through:

*DAG meetings

*Community briefings

*Community surveys

*Community meetings

*Dozens of listserv communications, project updates, and newsletters

*Hundreds of phone calls, emails, and one-on-one conversations Through these many forms of communications, the project team learned that the top community issues were air and water quality improvements, pedestrian safety, and open or green space improvements. Community members highlighted the need for the site to serve as a 'gateway' to Georgetown. RESULTS AND CONCLUSIONS The community engagement resulted in a number of design elements, measures during construction, and collaborations to benefit the community. These included:

*The GWWTS design fits in with the industrial character of the corner while highlighting architecturally innovative design.

*Water conservation through a green roof on the operations and education center is shown (Figure 2). Site wide water cisterns (Figure 3) collect rainwater which is then used to irrigate the landscaping.

*Facility landscaping includes trees specifically chosen for their air quality benefits.

*King County's collaboration with the community to improve air and water quality extended beyond the GWWTS. A 'green wall' of planters extends down a nearby city block. By partnering with a local community, a local grocery store has rain gardens and cisterns with interpretive signage (Figure 4).

*During construction, King County managed a 24-hour project hotline with a commitment to respond within one day to all issues and concerns.

*The community expressed a desire to understand when the station was operational and improving water quality. A piece of art called 'Theater of a Storm' developed by a lighting designer illuminates successive treatment processes as the station begins receiving wet weather flow and flow progresses through the station. The multi-colored LED lighting of facilities is shown in Figure 5. When the station is not operating, LED lighting is deployed to create a visually appealing station at night.

*Public art commissioned as part of the project connects the neighborhood to its own weather and experience of rain. The artwork, called a rain monument, is shown in Figure 5. During dry weather, rain falls down the inside of the cylindrical monument with the intensity of the previous storm. During a rain event, there is no rain in the monument. Public outreach to include the community in the design of the station resulted in many positive developments beyond improving the water quality in the Lower Duwamish Waterway. Through careful planning, listening to the community, and incorporating community identified design elements, the GWWTS is a gateway and community asset benefiting both the environment and the people who live, work, and play in Georgetown.

Potable water reuse typically relies on treated wastewater from a conventional water resource recovery facility (WRRF) with further treatment through an advanced water treatment facility with chemical oxidation followed by membrane filtration. Conventional activated sludge (CAS) is used at WRRFs for bulk chemical oxygen demand (COD) and nutrient removal. Chemical oxidation and membrane filtration are employed to remove micropollutants and achieve additional pathogen inactivation. Although CAS is commonly used, it is not without challenges, such as sludge production, long detention times, susceptibility to treatment upsets, and lack of complete micropollutant removal2. In contrast, chemical oxidation can remove COD, making it suitable not only for advanced water treatment, but possibly for bulk COD removal as well1,3,5,6. It would be beneficial to evaluate the efficacy of replacing a sequence of CAS, chemical oxidation and membrane treatment with a simpler sequence of chemical oxidation (i.e., ozonation) followed by membrane treatment (i.e., reverse osmosis (RO)). This proposed system may achieve secondary treatment goals while also providing micropollutant removal and pathogen inactivation for potable reuse in a simpler process. However, no R&D reports were found that advance the proof-of-concept to eliminate CAS when chemical oxidation and membrane treatment are employed for municipal wastewater reuse. Currently, the scenario to eliminate CAS is at technology readiness level (TLR) 2 (concept and/or application formulated), whereas more work remains to move to TLR 3 (invention and research moving to proof of concept) and beyond4. In this study, bench-scale research was performed to prove the concept of ozonation followed by RO as a technology for municipal wastewater reuse (ozone-RO). Municipal wastewater primary effluent COD removal kinetics during ozonation were determined and compared to removal observed from CAS at a full-scale WRRF. Additionally, COD removal and nutrient fate and removal across ozone-RO were determined. Results were compared to COD and nutrient removal values achieved at a full-scale CAS followed by RO (CAS-RO). To determine ozonation COD removal kinetics, municipal primary effluent (PE) 24-h composite samples were collected from a WRRF (Fox River WRRF, Brookfield, WI). The CAS system fully nitrifies, with alum added to the secondary clarifiers for phosphorus removal. PE was ozonated in a 3-L batch ozone contactor at three different temperatures (7 degrees C, 22 degrees C and 34 degrees C). Ozonated gas was generated using a nozone generator (TG-10 Ozone Generator, Ozone Solutions, Hull, IA). A total applied ozone dose of 33 g O3/LWater over 3 h was used (45 g/m3 ozone gas with a 184 mg/L-min ozone application rate). To determine nutrient fate and removal, experiments were carried out using PE in the ozone contactor at 22 degrees C for 3 h. After ozonation, the water was sparged with nitrogen gas to remove residual ozone before a flat sheet RO membrane (FilmTec BW30XFRLE brackish water membrane) held in a cross-flow membrane cell (CF-106, Sterlitech). Pressure was held constant at 250 psi for 24 h. The RO process was then repeated with the same operating parameters but treating a 24-h composite sample of CAS effluent. COD, total and reactive phosphorus, total nitrogen, ammonia, nitrate, nitrite, and organic nitrogen concentrations were determined using commercial kits (Hach Company). Batch COD removal curves were fitted to the data using a first-order model with respect to COD concentration (Fig. 1) and the first-order rate constant (k) values were 0.0043 + 0.00037, 0.0046 + 0.00042, and 0.0067 + 0.0011 at 7 degrees C, 22 degrees C and 34 degrees C respectively. An ANNOVA test indicated that these k values were statistically different (p=0.0126). The resulting Arrhenius temperature coefficient value ( was 1.077. The CAS system had a 7-h average hydraulic residence time (HRT) before 1-hr secondary clarification compared to the ozone HRT of 3-h. Both COD and sCOD removal values with ozone and CAS were similar, and both treatment systems resulted in final effluent COD <5mg/L after RO treatment. Ozonation removed some phosphorus and converted some nonreactive phosphorus to reactive. It is hypothesized that phosphorus removal occurred by precipitation since a white precipitate was observed in the ozone contactor. Precipitation may have occurred due to a pH increased from 7.7 to 8.4 during ozone contact. Future experiments are planned to determine if this is the case. Final phosphorus and nitrogen concentrations from ozone-RO and CAS-RO systems were relatively low and similar. For example, total phosphorus concentrations for both effluents were below detection (<0.15 mg/L PO43--P) after RO. Although ozonation did not result in nitrogen removal, it did oxidize ammonia to nitrate (Fig, 4), which was subsequently removed by RO. This is significant since ammonia is not effectively removed by RO. No nitrite was detected (<0.6 mg/L NO2--N) in any samples. The concept of ozonation followed by membrane treatment was verified for municipal wastewater potable reuse and advanced from TLR 2 to TLR 3. Ozone rapidly oxidized PE COD under the conditions studied. In addition, quasi first-order kinetic constants and an Arrhenius temperature coefficient was established for ozonation of PE. Additionally, ozone-RO achieved final COD and nutrient concentrations similar to CAS-RO treatment. These data can inform system scale-up for R&D.

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.

INTRODUCTION The removal of organic micropollutants (OMPs) prior to discharge into the receiving water bodies is gaining interest globally. When it comes to ozonation, The Netherlands is currently investigating with water authorities the feasibility to remove at least 70% of 7 out of 11 guide OMPs (Table 1), with minimal bromate (BrO3-) formation (<1µg/L yearly average). In this framework, the water authority De Dommel (WSDD), in close collaboration with the bouwteam (WSDD, AM-team and CLCWater (combination of ADS, Witteveen+Bos, Moekotte, Nijhuis en Pannekoek)), is constructing a full-scale ozone installation at the waste water treatment plant (WWTP) of Hapert. The integration of Computational Fluid Dynamics (CFD) and the kinetic AMOZONE model was used in the initial phase of this project and reported at WEFTEC2023 (Muoio et al. 2023). In this work, the simulations performed at the design stage were used to design the digital twin (DT). Considering the water matrix, the reactor's geometry and its behaviour at different flows, the ozone generator, and gas diffusers specifications, the DT was design to support the operator's decision making process to achieve both maximum OMPs removal and minimal BrO3- formation. While the full-scale installation is under construction, the DT is currently used for operators' training and preparation to explain the relevant details of ozonation and the impacts of operational changes with the actual water matrix. This crucial step is essential for the staff preparation in understanding the details involved in the correct operation of a complex installation such as an ozone reactor and to finally connect the DT real-time with the installation. METHODS The AMOZONE model (Audenaert et al., 2019) is a detailed mechanistic kinetic model for the prediction of OMPs removal and BrO3- formation including a large number of chemical reactions derived from experience and literature (inter alia: Bourgin et al., 2018; Buffle et al., 2004; von Gunten, 2003). In the CFD-AMOZONE results, two OMPs (benzotriazole and venlafaxine) to evaluate the average removal. In fact, benzotriazole has one of the lowest sensitivities, while venlafaxine can be used as good indicator of the average removal of the 11 compounds (Figure 1). The compartmentalization of the 3D CFD results was performed considering the hydraulics behavior at different flows and the resulting chemical concentrations considering the water matrix fluctuations (Rehman, 2016). This allowed to design a flow-sheet model containing all the spatial information of the detailed CFD-AMOZONE results, but able to run long-term dynamics for parallel computing with the real installation. RESULTS AND DISCUSSION The several simulations performed in the first part of this project with the CFD- AMOZONE tool for defining the best design of the ozone installation at different operational conditions were used to design the DT. The volume compartmentalization allowed to produce a fast model that can run on a regular PC but which includes key information from the hydraulics and chemical points of view that allow very realistic simulations. With the DT operational alternatives can be run using real data from the effluent of the biological installation. In Figure 2, results of dynamic simulations at different ozone dosages report the bromate formation through 15 days with 15min data frequency. At the highest O3/DOC dosage the bromate threshold of 1 ug/L is exceeded at several moments, while reducing the dosage below a ratio of 0.4 shows a much conservative scenario. The OMPs removal is also a dynamic outcome of the ozone dosing strategy, and resulted to be maintained above 80% in average by operating at a dosing ratio of 0.4 O3/DOC. The addition of H2O2 was also tested (data not shown) leading to further BrO3- reduction and to an increase in the removal of those OMPs with higher sensitivity to hydroxyl radicals. Currently simulations are in progress to assure a minimized used of H2O2. For the safety of the microbiome at the natural pond at the effluent of the treatment plant. Finally, the DT confirmed that working at reduced ozone gas concentration can create a double advantage by lowering both bromate formation and energy need while maintaining the required OMPs removal. CONCLUSIONS In the first part of this project the CFD-AMOZONE integration supported the design of the ozonation reactor at Hapert WWTP. During the construction of the ozone installation a DT was created as a result of the 3D results generated in the first phase. The DT is currently used for operators' training and preparation. In this way, the relevant details of ozonation can be illustrated to those who will operate the installation with an intuitive tool, considering practical implications of operational changes and water matrix dynamics on the actual installation which they'll soon operate. Several scenario analysis for the Hapert ozonation reactor were tested with the DT using the AMOZONE model in flow-sheet configuration to maximize the removal of micropollutants and minimize the formation of bromate. The DT allowed to test different ozone dosages in long/term dynamic simulations and define the minimum required dose to contain bromate formation below 1 ug/L and micropollutants removal above the utility's target.

Background The most widely employed process control strategies within water resource recovery facilities (WRRFs) are model-based and built on expert knowledge. Examples include ammonia-based aeration control (ABAC) and nitrate-linked internal mixed liquor recycle (IMLR) control. Even where machine learning algorithms are integrated, they are based on supervised learning where the model is trained with the 'correct answer' embedded within the training data. While this approach is often successful, it relies upon high-performing historical control on which to train the model and can be handicapped by human biases toward certain operational modes. Control strategies based on reinforcement learning (RL) are different. In RL, the algorithm (or RL agent) interacts directly with the control environment during training to map optimal actions to observation state data to maximize a specified reward (Figure 1) (Silver et al., 2018; Sutton & Barto, 2018). In this way, the RL agent is entirely data driven and learns from direct experience. Although RL has gained attention as a tool for WRRF control optimization, there remain numerous open questions about the efficacy of employing RL agents to achieve valuable process optimization outcomes in WRRFs (Croll et al., 2023a; Nam et al., 2023). To help address these shortcomings the present study addressed three objectives: 1) evaluate common RL algorithms in the context of WRRF optimization; 2) evaluate the effects of increasing the number of processes controlled by the RL agent; and 3) evaluate the best performing RL agents to better understand how successful RL control strategies compared to domain-based control strategies like ABAC. Methods The present study evaluated RL agent control optimization in the context of the Benchmark Simulation Model No. 1 (BSM1) (Figure 2). The BSM1, a 5-zone bioreactor with a secondary clarifier, IMLR, return activated sludge (RAS), and waste activated sludge (WAS), provides a standard model construction and testing framework to assess and benchmark WRRF control performance through a simulation environment (Alex et al., 2008). It also has predefined dynamic influent and a facility operational cost function. The cost function accounts for direct operational costs, including aeration energy, mixing energy, pumping energy, and biosolids disposal, and indirect environmental costs based on the mass of pollutants discharged to the environment. By defining the BSM1 cost function, with variations, as the RL agent reward function, agents could be rapidly trained to minimize overall facility cost and compared to 'baseline' BSM1 operation. To facilitate training, a novel RL training environment (Croll et al., 2023b) was developed using OpenAI Gym (Brockman et al., 2016) to connect a SUMO (Dynamita) BSM1 simulation to the stable baselines3 (Raffin et al., 2021) package in Python. Four scenarios were evaluated in this study (Table 1). Scenario 1 (S1) tested four common RL algorithms to determine which was best fit for application to WRRF control optimization, representing four common types of RL algorithms: Deep Q Network (DQN), Proximal Policy Optimization (PPO), Advantage Actor Critic (A2C), and Twin Delayed Deep Deterministic Policy Gradient (TD3) (Croll et al., 2023b). RL agents in this scenario controlled the dissolved oxygen (DO) set point for Zones 3-5 (Z3-5). Scenarios 2-4 evaluated RL agents from the best algorithm, TD3, for their capacity to control a greater number of actions throughout the BSM1 (Table 1) (Croll et al., 2024). Results Despite only controlling a single action, neither the DQN nor the PPO algorithms were able to produce agents which met the BSM1 effluent limits. Both the A2C and TD3 algorithms produced successful agents (Table 1) (Croll et al., 2023b). However, actions recommended by the A2C agent were not practical for a physical system, as the agent tended to alternate between very low and very high DO setpoints, which would result in excess wear and tear on physical equipment (Figure 3). By contrast, the TD3 agent tended to recommend actions that looked very similar to ABAC control (Figure 3). Despite the success of the TD3 agents in Scenario 1, the TD3 agent only reduced the BSM1 cost by 1.8% over baseline control, likely due to the limited scope of control that the RL agent had over the BSM1 simulation. Increased scope of RL control was evaluated in Scenarios 2-4. As the number of actions under RL agent control increased, so did the level of BSM1 cost reduction, rising to 8.1% in Scenario 3 and 11.5% under Scenario 4 (Croll et al., 2024). However, it should be noted that under Scenario 4, with the addition of WAS control to the RL agent scope, the effluent was not compliant with BSM1 limits. Rather, the RL agent determined correctly that the single largest contributor to the BSM1 operational cost was biosolids disposal and effectively ceased all sludge wasting, opting instead to pay for the defined costs for environmental pollution. This finding highlights the importance of developing reward functions that accurately reflect operational goals and regulatory limits, and suggests that the BSM1 cost function may have undervalued effluent pollution. A breakdown of RL agent actions and key process parameters during RL agent operation under Scenarios 3 and 4 are shown in Figures 4-7. These will be discussed in more detail in the final paper.

BACKGROUND Recently, every industry has been striving to enhance their carbon management strategies, and the wastewater sector is no different. The pressing need for effective carbon and nutrient management plus compliance with stringent regulatory limits has prompted the need to explore innovative and intensified processes [1]. Anammox is a cost-effective and efficient microbial process that offers a shortcut for nitrogen removal in the nitrogen cycle. When combined with partial nitrification, the PNA process has the potential to achieve complete autotrophic nitrogen removal [2]. PNA has been considered to be an effective and cost saving alternative to conventional biological nitrogen removal, for the treatment of ammonia-rich wastewater [3]. Despite being introduced as an innovative method for nitrogen removal, PNA is not widely used for full-scale mainstream treatment. The primary challenges in applying PNA to mainstream treatment are associated with the unstable selection of nitrite oxidizing bacteria (NOB), mutual inhibition, and competition for the substrates involved in the combined processes [4]. With significant PNA engineering challenges, hindering large-scale mainstream application, the newly developed partial-denitrification (PD) process presents a more promising solution, offering emerging opportunities for a more flexible anammox-based operation [5]. Even with ongoing research, the underlying principles of nitrite accumulation remain incompletely understood and there is still a lack of insight on the mechanisms involved in the nitrite accumulation process. Based on a recent review article by [8], it was determined that nitrite accumulation in denitrification processes can occur through various mechanisms, including ecology shift, carbon type, feast and famine, etc. This study presents a comprehensive approach to assessing nitrite accumulation, taking into account factors such as microbial ecological shifts, alternative carbon sources, feast-famine and carbon internalization, and the effects of COD/N in kinetics. METHODOLOGY The study was carried out using a 10-liter bench-scale Sequential Batch Reactor (SBR) at Toronto Metropolitan University, with operational conditions based on prior batch testing results. The lab-scale SBR aimed to determine the denitrifying kinetics of the biomass, utilizing primary effluent from the Ashbridges Bay Wastewater Treatment Plant in Toronto as the primary carbon source. Batch tests were conducted during the acclimatization period and after full acclimation to assess denitrification rates and kinetics. Additionally, Nitrate/nitrite Utilization Rate (NUR) tests were performed in-situ at low and high F/M ratios. RESULTS The initial carbon used for the partial denitrification assessment was acetate, and the Figure 1-A depicts the peaks of nitrite accumulation over a 57-day period of reactor acclimatization. Batch activity tests were conducted every five to seven days, revealing a noticeable shift in the occurrence of nitrite peaks. During the first 30 days, nitrite peaks were observed 30-60 minutes after test initiation, but after this period, a distinct shift occurred, with most peaks occurring 10-15 minutes after commencement, suggesting potential microbial transformation. Additionally, a correlation was observed in tests conducted after 30 days between the nitrite peak level and the COD/N ratio, although not clearly depicted in the figure. Furthermore, during literature review, studies were found mentioning the significance of specific partial denitrifying microorganisms, which only reduce nitrate to nitrite. The data presented contradicts the theory of the absence of nitrite reductase in some bacterial populations, as nearly all tests resulted in complete nitrite depletion by the end of the test. A similar trend to acetate was observed during the acclimatization with methanol as the second carbon source (Figure 1-B). During the initial methanol-based test, an intriguing observation was made: a nitrite accumulation peak was detected in the system, albeit lower, and it took approximately 60-75 minutes to appear. Given the absence of methylotrophs in the system, efforts are underway to comprehend the reason behind this peak. It is theorized that the available internalized carbon within the system might have been the source of this peak occurrence. One of the key observations made during these tests was the correlation between COD/N and the level of nitrite accumulation, which is considered very important and interesting for practical applications of PD. As depicted in Figure 2, the initial peak within the range of 1.5-2.5 may potentially be attributed to a shortage of electron donors, leading to an imbalance in the system's redox potential. A decline around 4.5-5 was noted, which corresponds well with the stoichiometric demand for complete denitrification. Once again, a peak within the range of 7.5-9 was indicated, suggesting an excessive amount of carbon beyond the half saturation coefficient (ks), creating an imbalance. These observations are considered very important and interesting for practical applications of PD. CONCLUSION This study aims to bridge the existing knowledge gap by elucidating the operational factors that significantly impact the stability and performance of the PD process. The findings will contribute to the development of efficient operational strategies for mainstream PDNA systems.

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.