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

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.

The North Texas Municipal Water District (NTMWD) is a regional wholesale provider to 24 communities spread between Collin, Dallas, Denton, Kaufman, and Rockwall Counties in North Central Texas, which are some of the fastest growing areas in the country. The service population is approximately 1.2 million people. NTMWD currently owns and operates:

*About 139 miles of gravity mains ranging in diameter from 8-inch to 60-inch

*About 96 miles of force mains ranging in diameter from 14-inch to 60-inch

*25 lift stations

*14 wastewater treatment plants This presentation will focus on methods and results of Years 1 (FY2017) through 7 (FY2023) of the 10-year Condition Assessment Program (CAP). In 2016, NTMWD began the CAP project with the goal to conduct a multi-sensor inspection of all large diameter gravity mains, condition inspection of all manholes, and condition inspection of all lift stations during the project cycle to develop a baseline condition score for each asset to compare in future inspections. The project team conducted several desktop analyses to identify the expected condition of the assets and prioritized the inspection of the assets based on consequence of failure and available funding. Each gravity pipeline is inspected using the RedZone Robotics Multi-Sensor Inspection Program (MSI) to measure the inside dimensions of the pipeline for comparison to the original specifications. This data is used to grade the pipe segment on a 1 to 5 scale with 5 representing the worst condition pipes in need of immediate attention. Through FY2023 of the program, the team has inspected approximately 593,753 linear feet (LF) of large diameter gravity lines with 35,318 LF (6%) receiving a score of 4 or 5. FY2024 is currently in progress and includes the inspection of approximately 96,789 LF of gravity lines and approximately 14,329 LF of force main inspections. It is anticipated that a detailed discussion of the gravity and force main inspections will be available at the time of the conference. NTMWD is concurrently working through a program to inspect each of their manholes using the RapidView IBAK PANORAMO(R) SI 3D Optical Manhole Scanner system. Through FY2023, the team has inspected 761 manholes. FY2024 will include inspections for at least 27 additional manholes. Each inspected asset is assigned a renewal action based on the observed and measured condition of the asset. For pipelines, these actions include replacements, point repair, O&M work, or re-inspection. Similarly, manholes receive either replacement, lining, point repair, O&M, or re-inspection recommendations. In addition to the inspection work, NTMWD is surveying all of the wastewater manholes and force main valves. During CAP FY2017, inaccurate manhole location data led to issues locating manholes to conduct inspections. Additionally, numerous manholes were identified during the pipeline inspections that were not present in the District's geographical information system (GIS). During surveying, it was found that some of the actual manhole locations were a considerable distance away from where the District's GIS indicated the manholes were located. As part of the survey process, inverts were measured for each pipe connecting to the manholes. The location and invert information presented in the placemark file used by Google Earth, Keyhole Markup language Zipped (KMZ), will assist the District in updating the GIS and their hydraulic model. What the team expected to find during this project was large diameter lines in fair condition with occasional defects. Instead, most of the lines (+90%) were observed to be in relatively good condition with minimal defects. The real surprise came from the difference between field verified, GIS, and as-builts records. Through the inspections:

*84 (and counting) previously unrecorded manholes have been identified,

*Significant changes in a few manhole locations,

*Several differences between as-builts and laser measured diameters have been identified,

*And connectivity discrepancies in the hydraulic model have been identified. As part of the FY2023 program, an updated risk-based assessment was performed to prioritize future inspections and re-inspections based on observations and recommendations from historical inspection data. A wastewater model of NTMWD's conveyance system was developed using the Innovyze InfoAsset Planner software to simulate an asset's likelihood of failure (LOF) and consequence of failure (COF). A total risk score was assigned to each wastewater line by multiplying the LOF and COF scores. LOF was based on an assets RUL score, material, age, maintenance history, and surcharged status, while COF was defined by the asset's accessibility, depth, redundancy, and traffic, potential environmental, potential I/I, and outage impact. The result was a maximum risk score of 100 with higher scores representing lines of very poor quality and extreme criticality. The wastewater line total risk scores were then grouped into ranges, and descriptive scores of Very Low to Very High were assigned. The results of the risk assessment showed that 93.26% of gravity mains and 79.92% of force mains have a risk grade of Very Low or Low. 1.19% of gravity mains and 8.02% of force mains are scored with a risk grade of High or Very High. The highest gravity main and force main total risk scores are 73 and 80.96, respectively. These results were then analyzed to update NTMWD's 10-year workplan.

Managing utilities operations effectively in the era of big data involves application of emerging technologies, tools, and modern practices. Houston's in-house Wastewater Infrastructure Planning team incorporates technological advancement in its daily operations. The City of Houston (COH) is the largest city in the state of Texas and the fourth largest city in the United States of America. Houston Water owns and operates 38 Wastewater Treatment Plants (WWTPs) with a combined permitted capacity of 564 MGD. The wastewater collection system includes approximately 6,000 miles of sewer pipes, 133,000 manholes, and approximately 380 lift stations spread out over 665 square miles area to serve about 2.3 million customers. Wastewater treatment plants (WWTPs) have long played a crucial role in safeguarding both the environment and public health. The conventional practices of operation and maintenance (O&M) within WWTPs have been predominantly reactive in nature. This reactive approach has created challenges for site staff operating in the field, as they grapple with noisy Supervisory Control and Data Acquisition (SCADA) systems and information overload. This often results in decisions being based on gut instinct rather than data-driven insights. In this context, plant operators typically become aware of issues only when equipment fails or performance reviews uncover underperformance, leading to a reliance on lagging performance indicators and a heavy focus on troubleshooting rather than proactive modeling and operations. To ensure the long-term sustainability and effectiveness of wastewater treatment plants, decision-makers require real-time visibility into plant operations with leading performance indicators that can enable them to optimize performance in a proactive manner. The harnessing of near real-time data from sensors, SCADA systems, IoT devices, and Work Order Management Systems presents an opportunity for WWTP operators to comprehensively understand their systems' performance using innovative digital tools that simplify rather than complicate their daily tasks. Over the past decade, COH has undergone a digital transformation of its wastewater management system. COH has developed an Advanced Infrastructure Analytics Platform (AIAP) which includes all data and analytics needed for wastewater infrastructure planning. This presentation discusses an early initiative by the planning team of COH aimed at developing a Data-Centric 'Smart' Operations and Maintenance platform. This approach begins with the essential step of integrating multiple databases or systems to gain a holistic understanding of the entire WWTP operation and maintenance landscape. In line with the City's Strategic Asset Management framework, this integration brings together the WWTP SCADA, HachWims, Work Order Management System, and Asset's Physical Attributes and Conditions into a unified system. This fundamental integration enables analysts to empower stakeholders to comprehend the status of WWTP operations and maintenance from multiple perspectives. The next critical step involves the development of comprehensive O&M Key Performance Indicators (KPIs) that serve as vital metrics for monitoring system performance. These KPIs, derived from the integrated databases, enable operators and decision-makers to assess the overall health of the WWTP system accurately. To transition towards a proactive mode of operation, advanced analytics and predictive machine learning algorithms are deployed to forecast influent characteristics. These forecasts, combined with real-time data from sensors and the SCADA system, allow for dynamic adjustments to energy consumption, chemical usage, and other operational KPIs. This dynamic approach ensures compliance with environmental regulations while enhancing operational efficiency. Moreover, a machine learning model developed based on the Work Order Management System enables predictive maintenance. It anticipates equipment failures, enabling maintenance teams to address issues before they escalate into costly breakdowns. By embracing proactive operation and maintenance, the integrated approach optimizes resource allocation across the board. This would eventually include personnel scheduling, chemical dosing, and various other aspects of WWTP operations, resulting in substantial cost savings. In conclusion, this presentation underscores the transformative potential of data-centric O&M for WWTPs. By adopting proactive strategies grounded in real-time data and predictive analytics, WWTPs can significantly enhance their efficiency, reduce operational costs, and bolster environmental stewardship. The transition towards data-centric O&M is a crucial step towards ensuring the long-term sustainability and effectiveness of wastewater treatment plants, positioning them as integral components of smart, forward-thinking cities. The tasks identified below are some examples of lesson learned:

*Collaborate with the WWTPs operation team to grasp the challenges and requirements for proactive optimization and maintenance.

*Understand, structure, and establish data systems to facilitate data modeling and integration.

*Utilize Business Intelligence tools such as Power BI and Python for exploratory data analysis and visualization.

*Develop data pipelines for seamless automatic data updates and document procedures to enhance digital transformation effectiveness.

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.

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 Concerns related to the formation of disinfection byproducts (DBPs) during chlorine disinfection of wastewater and other safety concerns regarding chlorine operation initiated a great interest in alternative chemical disinfectants. For example, peracetic acid (PAA) received significant attention due to its minimal aquatic toxicity and efficacy in reducing regulated fecal indicator bacteria (FIB) (Antonelli et al., 2006; Manoli et al., 2019; WEF, 2020). The generally low efficacy of PAA in inactivating viruses in wastewater along with the ongoing discussions about revision of the United States Environmental Protection Agency Ambient Water Quality Criteria to include a viral indicator (Dunkin et al., 2017), led to a strong interest in another peracid, performic acid (PFA), which its bacterial and viral inactivation capacity usually outperforms PAA (Ragazzo et al., 2020). The objective of this study was to establish efficacy of PFA as a disinfectant compared to PAA and sodium hypochlorite for secondary effluent wastewater applications. The inactivation of indigenous FIB by PFA has been evaluated and compared with PAA and sodium hypochlorite under identical conditions. The disinfection data were interpreted using the concept of integral CT (ICT) and modeled by an ICT-based double-exponential microbial inactivation kinetic model to develop ICT-response data. This abstract presents the initial results of the Water Research Foundation Project #5219 titled 'Performic Acid Disinfection in Wastewater Effluent and CSOs In Context of Disinfection By-Products and Future Ambient Water Quality Criteria for Viruses', with the participation of more than 10 wastewater treatment plants (WWTPs) across the United States and Canada. Similar experiments with the ones presented herein for the first WWTP will be performed for all participating utilities, thus the results of this project may have a significant impact on disinfection practices in North America. Additional to FIB experiments, disinfection tests on viral indicators inactivation and DBPs formation will also be performed in the framework of this project. METHODS Secondary effluent wastewater was collected from a WWTP in ON, Canada (activated sludge-based processes). Its basic water quality characteristics were: pH=7.6, TSS=7.7 mg/L, BOD=10.8 mg/L, COD=13.5 mg/L, TN=18.6 mg/L, and TP=0.4 mg/L. Disinfection bench tests were performed in 2 L of wastewater at 2 disinfectant concentrations (1 and 2 mg/L for PFA and chlorine; 2 and 3 mg/L for PAA). Samples were collected at 6 contact times (0, 1, 3, 5, 10 and 30 min) and analyzed for disinfectant concentration (Chemetrics and Hach methods) and E. coli, fecal coliforms, total coliforms and enterococci (standard membrane filtration methods) (GAP EnviroMicrobial Services, London, ON, Canada). RESULTS The residual disinfectant concentration data were used to calculate exposure to chemical disinfectant (i.e., integral CT) by fitting initial demand (D, mg/L) and decay (k, 1/min) (Eq. 1): ICT=((C0-D)/k)∙(1-e^(-k∙t))(1) where ICT is the integral estimate of the time-dependant residual disinfectant concentration (mg min/L), C0 is the initial concentration of disinfectant (mg/L) and t is the contact time (min). The FIB inactivation data were plotted as a function of integral CT (Figures 1-4) and modeled by a double-exponential inactivation kinetic model in the domain of ICT (Eq. 2): N=N0∙(1-β)∙e^(-kd∙ICT^m )+N0∙(β)∙e^(-kp∙ICT)(2) where N0 and N are the initial and after treatment concentration of bacteria (CFU/100 mL), β is the fraction of particle-associated bacteria, m is a parameter that describes initial resistance of bacteria to disinfectant, and kd and kp are the ICT-based inactivation rate constants for dispersed (free) and particle-associated bacteria, in (L/(mg min))m and L/(mg min), respectively. PFA exhibited the highest inactivation efficiency for all studied indigenous FIB, followed by chlorine and PAA (Figures 1-4). For example, model-predicted integral CT requirements for 1-log reduction of total coliforms and enterococci were determined as 3-4 mg min/L, 8-10 mg min/L and 40-45 mg min/L for PFA, chlorine and PAA respectively (Figures 3 and 4). Based on model predictions, to achieve a 2-log reduction of both commonly regulated E. coli and fecal coliforms, PFA required ~10 times lower ICT than both PAA and chlorine (Figures 1 and 2). We also present an advanced disinfectant dosing control strategy that accounts for changes in wastewater quality and quantity, together with the hydrodynamics of the contact chamber. Bench test results of PFA (Eqs. 1 and 2) were integrated into a process model to evaluate four dosing strategies, namely, flow pacing, constant ICT, constant ICT advanced demand, and constant ICT advanced demand/decay. Figure 5 and Table 1 show that the advanced control strategy achieves consistent performance and optimizes disinfectant dosage. CONCLUSIONS Results show that PFA was superior to both PAA and chlorine. Although the PFA pricing estimates are currently higher than that of hypochlorite, the lower ICT requirements of PFA may result in a competitive cost compared to chlorine. This indicates the need for site-specific testing to better understand disinfection efficiency and cost benefits of PFA as a wastewater disinfectant.

This year, cybersecurity attacks against our nation's critical infrastructure sectors have continued to challenge the operational integrity of our manufacturing environments and threaten our way of life. Cybercrime is an economic and national security sustainability threat. As we know, threat actor motives are often rooted in financial gain, as well as ideological differences. In short cybercrime is here to stay. Minutes matter, seconds count and the only control we have as people are over the decisions we choose to make to better protect our communities. As a result of consistently high cyber-attack attempts and incidents, recent changes to Federal and State administrative and civil laws have evolved to drive cyber risk management accountability. The time to act as a collective in the Water and Wastewater community is now because the quantifiable risk and liability associated with cyber-attack incidents has grown to an unsustainable level. To further contextualize, several states have waived sovereign immunity privileges relative to risk management, which directly places municipalities at risk from a Civil-tort liability perspective. Our goal as an organization is to help our customers on three fronts: fiduciary risk quantification, OT risk identification, and the development of a feasible OT system hardening roadmap that is tailored to your organizational needs. In this session, we will review the tactics, techniques, and procedures that every utility should know to protect themselves and build a comprehensive, unified IT/OT cyber resilience plan accounting for all potential security risk before, during, or after a cyber event. Additionally, a detailed explanation of next-generation OT networks and describe why traditional network isolation cyber defenses are no longer adequate for these mission-critical environments. We will offer a detailed cyber strategy and architecture to protect these networks' enhanced capabilities, along with common pitfalls and lessons learned. It is no surprise — Industrial Control Systems (ICS) are in the crosshairs of opposing nations and criminal organizations. Water and Wastewater facilities specifically need a heightened awareness due to their key role in the global supply chain. In addition to known bad actors, the modern facility is connecting to the outside world at an exponential pace and with greater connectivity comes greater security risk. Even well-intentioned actions can mistakenly impact network availability, interrupt operations, and halt productivity. Water and Wastewater organizations need a— including (but not limited to):

*Asset Inventory / Installed Base Identification

*Vulnerability & Risk Analysis

*Qualified Patch Management

*Cybersecurity Policy Development

*Endpoint Protection

*Perimeter Hardening (IDMZ) & Microsegmentation Deployment

*Zero-trust & Secure Remote Access

*Real-time Threat Detection

*Disaster Recovery Planning & Incident Response The best approach is risk-based in alignment with industry best practices with complete organizational adoption. Unfortunately, even the most sophisticated organizations can't manage all aspects of IT/OT cybersecurity alone — you need an ecosystem of trusted experts and partners by your side to extend your protection against next-gen security threats. To secure modern operational equipment — Computer OS Security, Network Security, Endpoint Protection, and continuous Security Monitoring. We will also review the emerging Managed Security Services leading the industry in data-driven cyber protection and response so that you can have confidence running a world-class ICS cybersecurity program.

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.

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 Total trihalomethanes (TTHMs) are disinfection byproducts formed through chlorine-based disinfection processes and are an increasing threat to wastewater, reuse, and drinking water systems. Recent regulations for direct and indirect reuse systems require reduction of TTHM levels. However, little guidance is available on appropriate technologies and methods for effective TTHM mitigation. Both removal technologies and alternative disinfection approaches offer possible solutions. This paper describes the comprehensive evaluation of TTHM mitigation alternatives that was conducted for a 15 megaliter per day (MLD) water reclamation facility (WRF) producing Class A reuse-quality effluent. Historical WRF operational data showed TTHM concentrations regularly exceed permitted limits. The permitting requirements for disinfection and TTHMs provide the basis of compliance for all alternatives considered. The facility's Aquifer Protection Permit (APP) specifies a TTHM alert level (AL) and discharge limit (DL) for TTHMs and fecal coliform. Alternatives were developed based on the treatment goal of reducing TTHM levels below the AL of 80 micrograms per liter (ug) and include peracetic acid (PAA), chloramines, air stripping, and source control. Figure 1: THM Speciation with Alert Level and Discharge Limit PAA DISINFECTION PAA can be a cost-effective alternative to chlorine-based disinfection systems. Existing disinfection doses and performance can indicate the efficacy of PAA disinfection, but there is little industry experience with achieving the disinfection performance required at this WRF. Bench testing was recommended to identify an appropriate dose range (Figure 2). While the bench testing showed good recovery of PAA through the contact period (Table 1), the maximum dose tested of 4 mg/L and 40 minutes contact time did not provide the effluent pathogen reduction required to comply with regulatory discharge limits. Figure 2: PAA Bench Test Results for 2 ppm Dose Table 1: PAA Recovery in Bench Tests Bench testing was inconclusive with respect to the design dose. However, recovery rates suggest higher doses would not reliably achieve disinfection performance targets as available residual PAA provided little disinfection between 20 and 40 minutes of contact. Additional bench or full-scale demonstration testing would be required to reduce uncertainty in design dose and refine cost estimates. CHLORAMINE DISINFECTION Under the proper ratio, chloramines bind up chlorine in a combined form and eliminate the pathway of TTHM formation. Chloramine disinfection requires a longer reaction time and CT target (total chlorine residual multiplied by reaction time). Disinfection kinetics can be complex and site specific; however, California's Title 22 regulations establish requirements for tertiary filtered disinfected water irrespective of free or combined chlorine. These requirements include a minimum CT of 450 mg-min/L in addition to total coliform limit of <2.2 MPN per 100 mL, corresponding to a minimum modal contact time of 90 minutes based on peak dry weather design flow. The limits from California's regulations were used as a conservative planning level basis and the expanded contact chamber footprint is conceptually shown in Figure 3. Figure 3: Conceptual Expansion Required for Chloramine Disinfection AIR STRIPPING Air stripping is a treatment method that effectively removes volatile organic compounds (VOCs) from a contaminated water source. The process forces air through contaminated water through the water via air stripping towers or aeration tanks. Several process alternatives for air stripping were considered including air stripping towers (3 or 6 tower configuration), surface aerators within a tank, and floating spray aerators within a tank. Vendors offer performance guarantees at the stated percentages to ensure that effluent water meets the permit's requirement, 80 ug/L, under a set of defined influent conditions (e.g., flow rate, TTHM speciation, temperature), as shown in Table 2. Table 2: Air Stripping Alternatives Performance Comparison SOURCE CONTROL ALTERNATIVES An evaluation of DBP precursors is also being performed to inform the identification and evaluation of potential source control alternatives. The results of this evaluation are pending and will be incorporated into a final presentation. RESULTS PAA was considered infeasible due to excessive risk and was eliminated for consideration. Variations of chloramine disinfection and air stripping were progressed to conceptual design for capital and annual operating cost estimates. The introduction of ammonia nitrogen and formation of NDMA from chloramines are considerable issues for the WRF. The net present values (NPV) for each alternative were estimated and air stripping towers were determined to be the most cost-effective alternative. This solution requires the smallest footprint (even in the two-pass system), has the lowest life cycle cost, and provides a confident performance guarantee given the plant sees its projected flows. This work serves as a valuable reference for utilities with TTHM concentrations exceeding current or anticipated effluent limits in drinking water, reuse, and wastewater applications. Table 3: Alternatives Cost Comparison Summary

Introduction: Metro Water Recovery's (Metro) Robert W. Hite Treatment Facility (Hite) in Denver, CO is permitted for a maximum month (MM) flow of 220 mgd and has two parallel liquids treatment trains including the North Secondary (NSEC). The NSEC utilizes a modified Ludzack Ettinger (MLE) process with a sidestream anaerobic reactor (SAR) to achieve nutrient removal. In 2018, Metro's facility plan identified a need for increased aerobic solids retention time (aSRT) to meet future potential total nitrogen (TN) and total phosphorus (TP) regulations (Colorado Regulation 31). To avoid costly expansion, Metro commissioned a full-scale demonstration train (NAB2) to trial densified activated sludge (DAS). This work documents findings from the full-scale demonstration facility and discusses how Metro is translating DAS into a full-scale solution at the RWHTF. Specifically, this paper will discuss factors that have led to the development and long-term operation of DAS with biological and physical selection, as well as provide insights into how particle size distribution (PSD) may be impacted by operational parameters and influence nutrient removal. Materials and Methods: DAS facility: The DAS demonstration facility (denoted as NAB2) consisted of an isolated, paired aeration basin and secondary clarifier from NSEC. Description of the facility is provided elsewhere (Avila et al., 2021). Metro operated NAB2 to test multiple distinct metabolic and kinetic selector configurations, with two primary configurations, Fig 1. A 'control' train was also operated without physical and biological selection. Routine influent/eff concentrations of organics, solids and nutrient content were determined using Standard Methods for the Examination of Water and Wastewater. PSD of the MLSS, hydrocyclone UF, and hydrocyclone OF were routinely characterized. Settling Column Testing: Settling column testing of bulk DAS ML was conducted on multiple occasions to determine the Vesilind equation settling coefficients (V0 & k) as well as the PSD. Additionally, settling properties for particle size fractions: <200µm, 200-600µm, and >600µm were characterized across a concentration range of approximately 1,500 mg/L to 6,000 mg/L. Activity Testing: Batch scale activity testing of bulk mixed liquor and three particle size fractions was used to evaluate nutrient removal rates of activated sludge in 5-gallon reactors. Analytes (NH4, NO3, NO2, and PO4) were measured with HACH TNT kits. Hydrocyclone Nozzle Testing: Hydrocyclone UF nozzle sizes ranging from 15 to 25 mm were individually tested at a target pressure of 30 psi. Flow measurements from the hydrocyclone feed and OF were recorded via flow meter. Total suspended solids (TSS) and PSD samples were collected from the RAS, OF, and UF. Process and Capacity Modeling - Data from NAB2 testing were used to develop, calibrate, and validate AB2 specific and a whole plant process model in BioWinTM and computational fluid dynamics (CFD) models of the NSEC secondary clarifiers. These models establish system capacity of existing infrastructure and design criteria for full-scale implementation. Results and Discussion: Impact of biological selection on densification: PSD of NAB2 biomass during configuration 1 (SAR-MLE) mode) stabilized into a uni-modal distribution, with median size increasing from 100 to 200 um respectively (Fig 2A). The average SVI30 for the NAB2 versus control basins were 102 mL/g and 153 mL/g respectively. PSD of NAB2 biomass during configuration 2 (SAR-A2O) mode reflected a bi-model distribution (Fig 2B). The average SVI30 for the test versus control basins were 81 mL/g and 173 mL/g respectively. Cumulatively, results suggest that improved settleability is observed when the mass fraction of granules (particles >212 um) in the sludge exceeds 15%. This was observed on multiple occasions when NAB2 operated in SAR-A2O mode with anaerobic food to microorganism ratio (F/M) being sustained between 1.0 and 3.0 lb sCOD/lb MLVSS-day. Impacts on PSD on Settling Performance and Biomass Activity: Settling velocity and compressibility were observed to increase as the particle size fraction increased (Table 1). Biomass activity results indicated that larger particle size fractions had lower denitrification and nitrification rates versus smaller particle size fractions while Bio-P activity was highest in particles greater than 200 um. These results indicate that minimizing particles sizes greater than 600 um may allow Metro to exploit high nitrification/denitrification/Bio-P rates and with superior settling and compressibility (Quoc et al., 2021). Influence of Physical Selective Pressures on PSD in NAB2 (Fig 3): Results indicated that mass flow through the UF could be reduced when the nozzle size decreases (Fig 2). This phenomenon can potentially be exploited to craft a wasting strategy focused on developing and keeping a target PSD. DAS impacts on Capacity: Stress testing indicated that NAB2 could be loaded at surface overflow rates (SORs) >700 gpd/sf and solids loading rates (SLRs) >60 pounds per day per square foot (ppd/sf) while still maintaining reliable blanket control and stable effluent TSS (Fig 4). Whole plant process and CFD modeling indicated that the densified scenario could allow Metro to successfully treat 2040 flows without needing to invest in additional aeration basins or secondary clarifiers, allowing for savings of $50 million dollars.