Conference Papers

INTRODUCTION: This case study offers valuable insights into innovative sewer control techniques, emphasizing the management of a high-flow 48-inch diameter public interceptor sewer. It illustrates how combining bypass operations, including flow-through plugs and multiple pumping systems, can address complex challenges effectively to avoid a 'sewage river' on the Las Vegas Strip. The study serves as a testament to the adaptability and efficiency required to ensure smooth sewage control and construction in a demanding urban environment with high visibility. Furthermore, it highlights the importance of meticulous project planning and the ability to navigate multifaceted obstacles. It demonstrates the critical role of problem-solving and showcases how the careful coordination of diverse operations can lead to the successful execution of development projects. BENEFITS: WHAT YOU WILL LEARN: 1.Innovative Sewer Control Techniques: This case study offers a comprehensive understanding of sewer control methods used in managing a high-flow public interceptor sewer system. It explores forward-thinking strategies, including the combined use of sewer bypass methods such as flow-through plugs and multiple pumping systems. 2.Project Planning and Problem Solving: This case study sheds light on how complex challenges can be addressed through meticulous project planning to overcome construction obstacles including highly congested roadways, limited space, complex geotechnical conditions, and critical timelines. It illustrates how careful coordination of various operations can lead to successful development projects. 3.Effective Public Infrastructure Management: The study highlights the adaptability and efficiency required for public infrastructure management, especially in densely populated and high visibility areas like the Las Vegas Strip. STATUS OF COMPLETION: This case study delves into the implementation of an innovative and strategic approach to ensure efficient sewage control in a high-flow public interceptor sewer located on the iconic Las Vegas Strip. The Developer was presented with the formidable task of accommodating the construction timeline of a new Las Vegas Strip resort, compounded by the concurrent aggressive Formula 1 track paving schedule. The challenge to overcome was timing so a solution was devised to relocate the point of connection for the new resort to core into an existing manhole instead of a cast in place manhole that would have avoided the complex bypass pumping system that now became a reality. The solution not only saved invaluable time but also circumvented the complexities of groundwater removal and permit requirements, thereby preventing potential construction delays and ensuring the critical Formula 1 track paving deadline was met. As the case study unfolds, it becomes evident that the existing sewage flows within the interceptor sewer exceeded the capabilities of a simple flow-through plug. This realization necessitated the adoption of innovative sewer bypass methods to ensure sewage control, even in the face of extreme volumes. The pivotal solution encompassed a comprehensive sewer construction process that began with the installation of onsite sewer components, followed by offsite sewer components, and culminated with coring into the existing manhole. To complete essential corrosion-protection work on the existing manhole, a sophisticated bypass system was set up, composed of a flow-through plug operation and two additional bypass pumping operations. These operations worked simultaneously to ensure efficient sewage control during the construction process. While this solution achieved its objectives effectively, it was not without its challenges. The project grappled with space limitations due to its location on the bustling Las Vegas Strip, keeping in place access to resorts and businesses on the Strip with the abundance of temporary piping, a point of connection that was over 26 feet deep, challenging geotechnical conditions related to groundwater at the manhole's depth, a strict timeline dictated by the Formula 1 track paving, and limited space for traffic control. CONCLUSION: In conclusion, the combination of these sewer bypass methods allowed the construction of the resort to proceed seamlessly, without interruption to the surrounding hotels, casinos, and businesses on the Las Vegas Strip. Furthermore, this case study emphasizes the potential for implementing combined bypass methods, such as flow-through plugs and pumping systems, to effectively manage complex sewage control in high visibility and densely populated settings. These innovative approaches offer versatile and dynamic solutions that can be widely applied in the field of public infrastructure management. This case study serves as a practical example, providing valuable tools for developers, engineers, and public agencies facing similar challenges. It also highlights the challenges that were unexpected and could have resulted in a major sanitary sewer overflow near the Las Vegas Strip. The successful completion highlights the adaptability and forward-thinking strategies necessary to address the unique challenges of high-flow sewage systems in urban environments. SUMMARY: Innovative sewer control techniques proved highly effective in the development and management of a high-capacity sewer system. This strategic combination of bypass operations, featuring flow-through plugs and multiple pumping systems, served as a solution to overcome a spectrum of project limitations and challenges. This case study showcases the successful implementation of advanced construction techniques and places strong emphasis on the roles of adaptability and project management. The valuable insights derived from this study provide possible solutions to professionals engaged in public infrastructure projects who face similar challenges within the field of sewer collection system management.

Purpose: Lift stations and force mains are essential to any wastewater collection system. Lift stations and associated force mains operate in a highly corrosive environment, typically subjected to widely fluctuating flows and pressure surges that affect force main integrity. Lift station and force main design seeks to avoid common damage modes, including H2S-induced corrosion and solids accumulation, but rarely benefits from the physical assessment of the installed and operating system to evaluate design robustness. The current study outlines the design and operational enhancements of lift stations and force mains as identified during the condition assessment of Lift Station 43 (LS 43) in the City of Phoenix (City). The City owns and operates 28 lift stations and approximately 72 miles of force mains, including approximately 62 miles of 12-inch and larger force mains. A comprehensive condition assessment of the LS 43 force main was performed as part of the city's ongoing efforts to understand and minimize the risk associated with buried infrastructure. The LS 43 force main conveys wastewater approximately 1.5 miles from LS 43 on 75th Avenue south of Southern Avenue along 75th Avenue to Broadway. The force main has three barrels constructed of 24-inch diameter ductile iron pipe referred to as Barrels 1, 2, and 3 and experienced two breaks associated with air accumulation. A comprehensive assessment was completed, including hydraulic modeling, CCTV, and electromagnetic (EM) inspection. The study's results can be adopted to improve the service life of not just LS 43 but any future lift station and force main. Benefits: The LS 43 assessment identified best practices to improve lift station and force main hydraulics and service life. By utilizing hydraulic modeling with different pump states, the assessment identified the areas of negative pressure and gas buildup. The results of hydraulic modeling were confirmed via CCTV assessment, which showed the presence of a miscellaneous waterline in the force main. This revealed that incorrect ARV placement obstructed the efficient functioning of the lift station and force main. This presentation will benefit that industry by outlining the factors contributing to air accumulation and remedial measures to address the concern. The presentation will also discuss design modifications such as the location and elevation of air release valves (ARVs) and the type of ARVs the industry should adopt to improve the life of the force mains. Additionally, EM assessment determined internal corrosion below the springline caused by solids accumulation, an infrequently considered damage mode for ductile iron pipe in force main service. Suspended solids in wastewater can settle in the force main and develop areas of microbially induced concrete corrosion (MICC). Efforts to allow for maximum future capacity in the initial design had resulted in low velocities and solids accumulation. Cleaning tools are regularly employed to dislodge accumulated solids, but the lift station and force main designs rarely allow for easy launch and retrieval of a cleaning tool. Additionally, there is no clear guideline on the cleaning frequency to improve the system's service life and reduce operational costs. The study aims to discuss the velocities needed to prevent solid accumulation, as well as the frequency and essential design modifications necessary to support regular cleaning. The recommendations presented in this study can be applied universally to any lift station and help the industry develop designs with cleaning and maintenance requirements in mind. Status of Completion: The investigation work to address ongoing air accumulation and internal corrosion issues is 100% complete. Results indicated the flow velocities and cleaning methodologies the City should utilize to prevent further internal corrosion and location for ARVs installation to prevent air accumulation. The City is in the process of procuring a consultant to design the recommended improvements. Conclusion: The City will now be able to allocate necessary funds for regular force main cleaning, identify locations of concerns, conduct regular maintenance, improve lift station efficiency, and improve service life. In conclusion, the study has identified best practices to improve lift station and force main hydraulics and service life. These best practices can be used to improve future force main designs.

Learning Objectives 1.Summarize the developments that have led to creation of sewer ventilation models. 2.Explain the steps required to build and calibrate a sewer ventilation model. 3.Show an application for using the ventilation model to size an odour control unit. Introduction Sizing air extraction for vapor phase odour control is a difficult task often leading to large safety factors and oversized equipment. Fan testing can be used to determine flow rates more accurately; however, it is a costly exercise that often only captures a limited range of wastewater flow conditions. Sewer ventilation modeling has evolved to accurately predict air extraction rates and optimum locations for installing odour control. This paper discusses the history of sewer ventilation modelling and presents case studies demonstrating applications of ventilation modeling for odour control in sewers. Development of Ventilation Modelling In 2007 the Water Environment Research Foundation undertook a review of all published literature on sewer odours and corrosion. Sewer ventilation was found to be the subject in most need of further research (Apgar et al, 2007). Field tests using tracer gas were used to measure air flows in large sewers leading to a proposed conservation of momentum approach to natural ventilation with the air/water interface modelled as flat plate with a drag coefficient. However, the drag coefficient value was unknown. (Witherspoon, 2009) In 2011 the Australian research Council initiated a project to determine the interface drag coefficient. This work culminated in a model for calculating air pressure and flow in a linear sewer network (Ward, 2011), subsequently, flat plate drag coefficients were measured in laboratory-scale studies at the University of Aalborg (Bentzen,2016) for use in the conservation of momentum method. In 2020 a software tool was developed capable of solving air pressure and ventilation in large, branched sewer networks, including representation of air extraction fans, and then overlay the ventilation results in sewer process models (Ward, 2022). Work is continuing to better represent how drop structures impact ventilation rates. The ability to overlay this ventilation model with the sewer process model allows for more accurate estimation of headspace H2S concentration and the required airflow rates to maintain sewer headspaces under negative pressure. Two case studies are presented where this methodology is applied. In one, the client was able to make changes to the sewer network prior to completion of design, and in the second, odour control systems were sized without the need for costly fan testing. Case Studies Region of Vaughan New Trunk Sewer Construction: The region of Vaughan, part of the Greater Toronto Metropolitan Area (GTA) is constructing a new major truck sewer, Jane St Trunk, and twinning portions of existing trunk sewers, Keele Langstaff. The trunk sewers will provide sufficient capacity to service the projected growth in Northeast Vaughan to the year 2051. Sewer process models and overlaid ventilation models were developed for 2024 (completion of the Keele-Langstaff segments) and 2028 (completion of the Jane St segments) growth scenarios. These time frames represent the lowest flow scenarios, i.e. highest sewer detention time, which are the conditions most susceptible to sulphide generation and potential odour release. Sampling took place to allow calibration of the models. A comparison measured versus modelled data will be detailed and as well as assumptions that were made during calibration. The major finding of the study was that the planned dropped structures along the Jane St Trunk caused sulphides to be stripped from the water into the gas phase, leading to elevated levels of H2S, see Figure 1. The ventilation model predicted the trunk would operate at a slight negative pressure due to the drag forces and closed nature of the sewer (minimal laterals and openings to atmosphere) with in gassing (negative pressures) at each maintenance hole/drop structure, creating a scenario in which the odours would not escape to the ambient environment. However, the region has had issues with corrosion at drop structures and the H2S levels were high enough for the region to request a redesign of the Jane St Trunk to mitigate H2S release and corrosion. The sewer design work is currently underway. Following its completion, the sewer process modelling will be recompleted. Adelaide Trunk System Odour Investigations: 18 of the 21 odour control facilities in the Adelaide Trunk system have been turned off to avoid odour complaints, resulting in a lack of ventilation along the system. The lack of ventilation has been identified as a major risk to a significant asset with severe corrosion consequences. Sampling took place to calibrate sewer process models and an overlaid ventilation model. The calibration of the ventilation model provided numerous challenges due to the large headspace in the main trunks resulting in slight pressures during sampling, uncertainty of the state of repair of large curtains pervious installed in the network to assist with zoned ventilation control and a siphon located close to the edge of the modelled domain. The zone of influence from the current fans was found to be minimal and reinstatement of decommissioned fans was not considered a suitable solution to the systemic odour and corrosion issues in the Adelaide Trunk system. Recommendations from the modelling will be discussed including recommended chemical dosing, lining sections of the trunk sewer and installing a large odour control unit in the vicinity of a new development, see Figure 2. Conclusions The development of a ventilation model which can be overlaid on a sewer process model is a value tool for accessing the generation and release of odours from the collection system and sizing odour control fans.

Purpose of the Presentation
The purpose of the presentation is to demonstrate the innovative approach to assessing sanitary sewer overflow compliance being used by Christchurch City Council (CCC), New Zealand. Continuous simulation of long-term rainfall data is used by CCC to assess overflow compliance rather than using a synthetic rainfall pattern that is intended to represent the target return period. Furthermore, collection system planning is based on a design storm that was generated based on statistical analysis of the 25-year rainfall continuous model simulation results. The presentation will show that SSO frequencies are sometimes not well represented by rainfall events that have an equivalent return period and that antecedent rainfall conditions and hydrologic and hydraulic (H&H) routing of flows unique to each collection system can help to select a better design storm to simulate overflow return periods of interest.

Benefits of the Presentation
This presentation should be selected because it will provide the following benefits to the audience and industry:
-- it will illustrate the difference in overflows predicted using a synthetic return period rainfall event and the overflow frequencies calculated based on continuous simulation of long-term rainfall.
-- it will show how the environmental regulators for Christchurch, New Zealand require continuous simulation of long-term rainfall to validate overflow compliance.
-- it will demonstrate the value in reviewing continuous simulation overflow results to develop more accurate design storms to be used for infrastructure planning.
-- it will show how a utility can use an improved approach to developing design storms to ensure investments are made in new infrastructure and infrastructure rehabilitation programs that are targeted in the relevant area of the collection system in order to meet consent conditions effectively.
-- it will illustrate how three different 15-year windows of rainfall from a 25-year period of rainfall can affect the outcome of the overflow frequency assessment but that the climatic variations do not have a significant bearing on the outcome of the overflow compliance.

Project Background
Christchurch City Council provides drinking water, stormwater, and wastewater across five council areas in the North Island, New Zealand. Christchurch has a complex wastewater network serving 373,000 people. Christchurch has a large and complex wastewater network serving approximately 373,000 people with a single wastewater treatment plant capable of treating 650 megaliters/day (MLD). Christchurch has two main river systems: the Avon River and the Heathcote River, which both flow into the Avon-Heathcote Estuary which then flows into the Pacific Ocean (see Figure 1). Christchurch City Council (CCC) holds a resource consent (permit) for the overflows to waterways. The resource consent allows an overflow frequency to each of these receiving environments which decreases over time to a 2 year ARI, based on 15 years of long time series modelling. In addition, no overflow site may overflow more than every six months on average, based on the same long time series modelling. The Christchurch Overflow Compliance Assessment project was commenced and completed in 2020. The project was completed using the latest model calibration completed in 2020 and was an update to the overflow compliance assessment completed based on the model previously calibrated in 2015. The overflow consent conditions require that continuous simulation of the most recent 15-years of rainfall be completed to assess the system performance. This project included continuous simulation of the most recent 25-years of rainfall and analysis of overflow results from three different 15-year windows to investigate whether the overflow frequencies are significantly affected by the 15-year window of rainfall selected. Overflow control measure alternatives to achieve the 2-year overflow return period target were previously assessed using a synthetic rainfall pattern. To determine whether this rainfall pattern would be appropriate for future planning studies, the long-term continuous simulation results were used to predict the location of overflows occurring more frequently than once every two years and then compared to the locations predicted using the synthetic rainfall pattern. This assessment demonstrated that the synthetic event did not provide a good representation of actual overflows and a new design storm was developed based on historic events.

Project Details
The objective of the wet weather overflow compliance assessment was to determine wastewater overflow compliance with the consent conditions stipulated by the environmental protection agency, Environment Canterbury (ECAN). This was undertaken using the calibrated hydraulic model to simulate system performance based on continuous rainfall data from the period of 1995 to 2020. To determine whether the rainfall window could have an impact on any of the consent compliance results, the assessment of overflow frequency and volume was performed for the following time periods:
1. 1995 to 2020
2. 1995 to 2010
3. 2000 to 2015
4. 2005 to 2020

The compliance assessment results summarised in Table 1 and Table 2 below, show the level of variation in overflow response according to the rainfall window chosen. While the variations are significant in some time windows, the compliance outcomes would not have been affected. Table 1: Overflow volume in each catchment for different time periods Table 2: Overflow frequency in each catchment for different time periods The objective of the design storm review was to ensure the design storm used for wastewater infrastructure planning is representative of a 2-year return period based on the 25-year continuous simulation results. The assessment was based on overflow volume, peak and spatial distribution. The 25-year continuous simulation results were reviewed to identify historical events that corresponded to an overflow return period of approximately 2 years. Due to a high degree of rainfall spatial variance in the historical events that were close to a 2-year return period, it was decided to repeat the overflow statistical analysis by receiving environment rather than system-wide. Based on the results from the overflow statistical analysis, several 2-year design storm alternatives (synthetic and historical) were shortlisted. The preferred 2-year design storm, presented in Figure 1, was the August 5, 1995 (northern basins) and April 17, 2014 (southern basins) composite event. This event provided the best representation of 2-year ARI overflow volumes, peaks and spatial distribution and comprised events of sufficiently short duration to be convenient for planning.

Conclusion
The results from this study demonstrate a novel and improved approach to developing design storms to ensure investments are made in new infrastructure and infrastructure rehabilitation programs that are targeted in the relevant area of the collection system in order to meet design criteria and/or compliance targets.

A sluggish velocity in critical decisions by utility Boards, Councils, and Commissions presents a significant risk to addressing the complex challenges in the modern water/wastewater utility. Including real-time data storytelling as part of a comprehensive business intelligence program can significantly accelerate decision velocity. When coupled with a utility-wide modern data warehouse that feeds the business intelligence platform all of the utility's disparate data in real-time, full decision perspective can be continually delivered to the decision maker no matter how complex the decision nor how many data sources are necessary to tell the story. The AWWA 2021 State of the Water Industry report [1] paints a clear picture of the complex challenges before today's water/wastewater utility oversight bodies. Aging infrastructure, capital improvement financing, long-term water supply, emergency preparedness, watershed protection, aging workforces, regulatory compliance, groundwater management, emerging regulations, cybersecurity, cost recovery, talent attraction, asset management, customer relationships, water loss — the breadth and depth of management, finance, and technical decisions demanded of today's oversight bodies is daunting. This decision complexity is further complicated by the lack of requirements for technical expertise to serve on City Councils, County Commissions, and many Boards of Directors. In The Psychology of Human-Computer Interaction, Newell, Card, and Moran [2] present a description of the Hick-Hyman law [3,4] which postulates the time to make a decision is a factor of the number of choices and the probability of occurrence of each choice. For any single technical issue a utility oversight body considers, there are (practically) multiple potential choices and (theoretically) an infinite number of choices. When considering stratified decisions, such as a simultaneous (1) water rate increase with (2) an assessment of water affordability and (3) the reduction of aged infrastructure backlog, no decision-time model exists that dependably describes the resulting decision timeline. What every utility executive knows is that the time-to-decision on any one of these issues is significant. In October 2019, Opelika Utilities (Opelika, Alabama) presented their Board of Directors with a Capital Strategic Plan that assessed the requirements for full lifecycle replacement of all horizontal assets. The assessment identified a rate of replacement that would require a 5X multiplier when compared to the current annual capital asset replacement program. General Manager Dan Hilyer, PE, identified the following critical decisions that would need to be made within the first years: 1.Fund the immediate replacement of 100% of system water meters with an Advanced Meter Infrastructure (AMI) system; 2.Establish the long-term disposition of the system's most aged water treatment plant; 3.Fund refurbishment of the aged plant or the design of a similar replacement plant; 4.Establish a timeline to fully fund all reserve accounts; 5.Establish a policy to minimize the long-term cost of money; 6.Establish an approach to resolve taste and odor; 7.Establish a capital improvement program sufficient to meet lifecycle replacement for 100% of horizontal assets; and 8.Establish an appropriate water rate to fund the other objectives. As of October 2020, the Opelika Board of Directors had accomplished only one of the necessary critical decisions, funding of the AMI project. Without an acceleration in the decision velocity, the necessary decisions to manage aged asset backlog, water affordability, aging workforce impacts, emerging contaminants, taste and odor, and many other challenges would be at risk. The very sustainability of Opelika Utilities hinged on the ability to accelerate all of the complex decisions before the Board of Directors. With a newly established enterprise data warehouse that delivers data across all of Opelika Utilities' data sources to the management team in real-time, the Opelika Utilities General Manager recognized an opportunity to establish a vision to accelerate Board of Directors decision velocity through the utilization of real-time data storytelling. The following regular Board decisions were identified to be included in the initial dashboard iteration: - Annual water rate setting; - Annual Capital Improvement Program; - 5-Year Capital Strategic Plan; - Annual analysis of water affordability; - Monthly management of the long-term cost of money; - Management of the aged infrastructure backlog; - Annual management of reserve financial accounts; - Annual budget setting; and - Long-term water rate and water affordability management. This approach to data storytelling requires the real-time delivery of data from the following data sources: 1.General Ledger; 2.Budget; 3.Geospatial; 4.SCADA; 5.Billing; 6.Metering; 7.Work Orders; 8.Service Requests; 9.Inventory; 10.Capital Assets; and 11. Human Resources. Opelika Utilities utilized this new capability and paired it with the following principles of dashboard design: 1. Provide the Board of Directors with the decision narrative; 2. Create perspective of importance for each decision; 3.Provide clarity of current state and desired objectives; 4.Demonstrate connectivity of decision points; 5.Provide feedback for all decision points; 6.Demonstrate consequences of decisions and present alternatives; and 7.Accomplish all objectives in real time. The resulting dashboard for the Opelika Utilities Board of Directors is providing a transformative experience in decision-making. Data storytelling provides the Board of Directors with a clear narrative and metrics to reduce long-term water rates, increase affordability, have confidence in the capacity of the water system, and minimize the short-term cost of borrowing money. The approach to data storytelling even gave the Board enough confidence to adopt a real-time automated variable water rate that equitably recovers the true cost of both water production and water service. The Opelika Utilities Board of Directors now makes multiple critical decisions each month — without hesitation — with full confidence and clear perspective. This technical presentation will tour through several of the data story dashboards used by Opelika Utilities, provide a brief overview of the business intelligence delivery platform that spans all utility data sources, and discuss the specific benefits realized by each story dashboard.

The District of Columbia Water and Sewer Authority (DC Water) currently oversees over $7.5 billion in assets and manages a ten-year Capital Improvement Program (CIP) with a budget exceeding $5 billion. To that end, DC Water launched a District-wide inspection program in the Spring of 2022 that aimed to inspect 40 miles of sanitary and combined sewers between 12 and 60 inches in diameter each fiscal year. Findings from these inspections would be used to identify and prioritize assets for rehabilitation under the CIP. Performing inspection work in any major city is no easy feat. Performing inspection work in the District of Columbia, one of the most densely populated cities in the United States that also houses a plethora of federal agencies and military bases, presented a multitude of unique complications. Along with more typical road blocks such as aging infrastructure leading to emergency repairs and unmapped assets discovered in the field, the surrounding stakeholders and property owners affected by the inspection program included foreign embassies, government agencies, the US Secret Service, Joint Base Anacostia-Bolling, the National Park Service, the Smithsonian National Zoo, the DC Department of Transportation, a prison, and even disgruntled homeowner associations, to name just a few. The project team expertly handled an assortment of communications for permit acquisitions, access coordination, and stakeholder outreach. As if these circumstances were not challenging enough, the procurement timeline resulted in a tremendously accelerated inspection schedule during which 40 miles of inspection work had to be prioritized, performed, reviewed for quality, and invoiced all within the last five months of the fiscal year. Through an innovative use of new software tools, and copious amounts of coffee, this seemingly impossible feat was accomplished on time and on budget. The project team employed several programs and technologies to efficiently process inspection media and data in order to meet the ambitious deadline. T4 Spatial's inspection management platform, t4 Vault, allowed the inspection contractor to easily upload inspection submittals to the quality reviewer. The platform's user-friendly display showing the inspection media and reports side-by-side greatly facilitated quality assurance and quality control (QA/QC) reviews. Additionally, InfoAsset Manager (IAM) was deployed in conjunction with t4 Vault to perform corrections to the NASSCO PACP and MACP databases. IAM also possessed useful capabilities to export tracking sheets documenting the status of inspections and inspection reviews. In the field, the project team employed the use of the Fulcrum app for field inspectors to easily submit daily logs and field entries. Crews also collected GPS using Terraflex. Dashboards using ArcGIS Online were developed to convey the most up-to-date inspection data in an easy-to-understand quantitative and visual format to the utility owner. The inspection program is now wrapping up its second fiscal year of inspections and, to date, has completed over 100 miles of pipe inspections and 3,000 manhole inspections.

Introduction The Woodman Point (WP) Water Resource Recovery Facility (WRRF) is owned and operated by Water Corporation. The WP WRRF is the largest treatment plant in Western Australia and services industrial, commercial, and residential customers in the southern Perth metropolitan region. The WRRF liquid stream treatment process was upgraded in 2019 to provide 180 ML/d wastewater treatment capacity (approximately 900,000 equivalent population). The Water Corporation selected a 120 tDS/d design horizon for the next WP solids handling upgrade, which corresponds roughly to the 180 ML/d design horizon and includes dewatered solids imported from regional WRRFs. Growth in the WP WRRF catchment is projected to continue beyond 250 ML/d and 160 tDS/d (including imported solids) in 2060. The existing egg-shaped digesters (ESDs) at WP WRRF use mesophilic anaerobic digestion to stabilize combined thickened primary sludge (PS) and excess activated sludge (EAS) into digested sludge (EAS is equivalent to Waste Activated Sludge), which is then dewatered into biosolids cake, suitable for direct beneficial use in agriculture under the Western Australia (WA) Guidelines for Biosolids Management. Biosolids must be Pathogen Grade 3 (P3) (equivalent to Class B), Contaminant Grade 2 (C2) or of better quality to be suitable for direct beneficial use in agricultural land. Without an upgrade to the current solids handling process, achieving the P3 C2 requirement is at risk. The only alternative for management of off-specification biosolids is landfill disposal, which is financially and environmentally unsustainable. Water Corporation completed a planning study in 2019 that identified EAS only thermal hydrolysis process (THP) and EAS only carbonization process as preferred technologies for consideration. The principal driver for implementing THP is achieving a design minimum digester solids retention time of 15 days within the existing digesters to meet P3 requirements. Carbonization was identified as an technology to potentially augment digestion capacity and manage emerging contaminants of concern, notably Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) and microplastics. Methodology Six different process options utilizing one or both of Water Corporation's preferred technologies, THP and carbonization, were evaluated to select the preferred process configuration for the WP solids handling upgrade. These options included: -EAS only THP PS and hydrolysed EAS are digested in the existing ESDs. -EAS only carbonisation PS is digested in the existing ESDs and undigested EAS to diverted to a new carbonisation facility. -Full THP Hydrolysed PS and EAS are digested in the existing ESDs. -Full THP with digestate carbonisation Hydrolysed PS and EAS are digested in the existing ESDs, and digestate is diverted to a new carbonisation facility. -Intermediate THP (i-THP) PS is digested in a new ESD. Digested PS and EAS are hydrolysed and digested in the existing ESDs. -Post THP PS and EAS are digested in the ESDs, with additional ESD capacity provided. Digestate is hydrolysed and dewatered. Dewatering centrate is returned to the digesters for further digestion. Simplified block diagrams for each option are presented in Figure 1 through Figure 6. Mass and energy balances were completed, incorporating key inputs from vendor-specific equipment/processes. Key outputs from the mass and energy balances are presented in Table 1. Post digestion THP was not evaluated in detail as it required the greatest additional digestion capacity, despite potentially providing the highest dewatered cake solids concentration. Results The THP options were assessed to be the most favorable options based on a multi-criteria assessment. One of the key drawbacks considered for THP is that it cannot manage emerging contaminants (including, but not limited to, PFAS and microplastics). The current regulatory environment does not require management of these contaminants. As a result, carbonization was considered as a future augmentation if PFAS were to become strictly regulated. The key drawbacks of biosolids carbonization at the time of evaluation was the technology was considered to be embryonic and not sufficiently established at full scale to be implemented with confidence by 2024 without any onsite trials, and there is uncertainty in acceptable the biochar bi-product end-uses in Western Australia. EAS only THP was selected as the preferred option as it balances initial capital expenditure by intensifying the existing process capacity, enhances generation of biogas, and allows for future implementation of other process options (including energy neutral carbonization). EAS only THP also provides the greatest (net positive) energy balance, without requiring supplemental fuel for heat/steam during normal operations. The EAS only THP option provides the flexibility to increase future plant capacity with another THP train and/or construction of the fourth ESD and implementation of i-THP. The capacity can be augmented in stages to manage capital investments. Alternatively, digestate carbonization can be implemented at any stage, with the benefit of having fully or partially digested solids as the feed to the thermal dryer, reducing the drying capacity required. Carbonization can also be implemented to manage emerging pollutants or minimize transport of the end product off-site. Figure 7 show the concept design layout of the EAS only THP implementation, with areas for future expansion. Conclusion This paper will benefit the water utilities, and consultants as it demonstrated how both THP and carbonization technologies can be complementary. EAS only THP was determined to be the preferred option for the 120 tDS/d solids upgrade, and a staged implementation approach to carbonization was identified for consideration beyond the 120 tDS/d. EAS only THP maintains the current biosolids quality required for the projected growth in plant capacity and balances initial capital expenditure by intensifying the existing process capacity while allowing for future implementation of other process options such as carbonization if PFAS were to become strictly regulated.

The City of Spokane (City) owns, operates, and maintains the wastewater and stormwater collection systems (collection system) in Spokane. These systems consist of a variety of assets and facilities, and accomplish the important purposes of:
-- Collecting and conveying wastewater from residents and businesses, along with stormwater runoff from areas with combined sewers, to Riverside Park Water Reclamation Facility (RPWRF) for treatment and discharge.
-- Collecting and conveying stormwater runoff from surfaces throughout the City for at least partial treatment and discharge.
Stormwater is discharged to a variety of endpoints, including the Spokane River (as part of the City's municipal separated storm sewer system [MS4]), into the ground (via bioretention and underground injection wells, also known as dry wells), or evaporated. Both the wastewater and stormwater systems have historically been operated with minimal data collection and supervisory or remote control capabilities, primarily because the assets and facilities have generally been achieving their desired performance. However, the City has long recognized the potential for improved performance of the collection system through the implementation of supervisory control and data acquisition (SCADA) for the collection system (referred to as the 'collection system SCADA'). The collection system SCADA will allow for increased monitoring and alarming, improved data management, and the potential application of real-time control (RTC) at combined sewer overflow (CSO) control facilities and interceptor protection tanks (IPTs). These improvements will result in reduced CSOs, reduced risk of sanitary sewer overflows (SSOs), more efficient operations and maintenance (O&M), and an increased understanding of how the system operates. Implementation and operation of the collection system SCADA would also have staffing and cost (capital and O&M) impacts on the City that need to be considered. Now that the City has constructed large and complex CSO control facilities and IPTs throughout the City as part of complying with the City's Waste Discharge Permit for CSOs and the RPWRF, the City has prepared a Collection System SCADA Master Plan (Master Plan), completed in May 2019. The purpose of this Master Plan was to:
-- Identify and evaluate potential opportunities for RTC at CSO control facilities and IPTs that could be implemented in the future, and assess costs and staffing impacts
-- Identify and prioritize monitoring and alarming improvements to the collection system, and assess costs and staffing impacts
-- Identify SCADA network and infrastructure needs to support the implementation and operation of the monitoring, alarming, and RTC improvements identified, and assess costs and staffing impacts

Establish an implementation roadmap for the selected collection system SCADA improvements and assesses the capital, O&M, and organizational impacts of implementing the recommendations As part of the Master Plan, the project team developed a system model of the City's sewer system, and simulated possible RTC scenarios to manage wet weather events. The model results indicated a reduction in CSO volume of between 30 to 40 percent, as shown in Figure 1, depending on the storm and level of RTC implemented. Not only did RTC reduce CSO volumes, but it also allowed for better protection of critical points in the interceptor system that are susceptible to surcharging. In conclusion, this project established a clear and implementable path forward for the City to implement SCADA in their collection system. The SCADA system will provide benefits on many fronts -- CSO reduction through RTC, improved O&M and performance due to real-time data collection, and improved reporting. This presentation will focus on describing the gaps and solutions identified in the Master Plan, with a particular focus on discussing the RTC analysis and results, and presenting the anticipated O&M impacts of making the improvements. This completed project was unique because it focused on using RTC as an adaptive management strategy for completed CSO control facilities. Many other municipalities are now in similar situations, where they have finished building CSO control facilities and are dealing with what to do if the control facilities are not sufficient to meet CSO reduction standards. This project provides an example of retrofitting completed facilities with RTC and monitoring in order to improve performance. Following the completion of this project the City has moved forward with designing and constructing the collection system SCADA, and will be making monitoring improvements at several high-priority pump stations and CSO control facilities.

Sewage drop shafts function as a powerful air moving devices by creating water-in-air waterfalls that move air like fans or air-in water fluid columns that transport and compress quantities of air when water velocities are greater than the bubble rise velocity. This creates situations where air in unvented tunnels can transfer pressure at the sewer obvert to the surface at shafts that, even when vented can lead to situations where air and water forcefully exits manholes at the surface and damages surrounding infrastructure (Figure 1). This damage can be severe in large wet weather events. One such event was in St. Louis Missouri on August 30, 2021, which caused a precast drainage structure top to separate from the main structure (referred to herein as the Ikea shaft, the result being visible in Figure 2 below). Another depressurization at Arkansas and McKean caused damage to the pavement near a drop shaft and is generally a nuisance to residents. For the Ikea shaft, SWMM models for the area were analyzed to estimate hydraulic flow through the sewers during cloudburst events. This accompanied creation of an inventory of all drop shafts associated with the tunnel of interest using record drawings. Model results were superimposed onto the inventory to determine how flow enters the deep tunnels, the quantity of flow at each inlet and outlet, and identify manholes where no flow enters the sewer from above. This review identified that the Ikea shaft was the first (in the direction of flow) that did not have flow from above that could otherwise prevent air pressure at the sewer obvert transferring to the surface, and that over half the drop capacity of the deep sewer system is upstream of the Ikea shaft.A previous evaluation of the structure had been performed. This investigation concluded that the drop shaft experienced a rise in the hydraulic grade line during wet weather, which caused the overflow events. As a result, a grate vent (visible in Figure 3) was installed on the structure. This helped mitigate issues, but a rising hydraulic grade line did not explain ongoing cover slab displacements. It was determined that the investigation had not directly considered the deep sewers upstream of the Ikea shaft, vent locations, and steady-state phenomena like air flow and entrainment effects. In response to these observations, one-dimensional model of the deep sewer system connected to the Ikea shaft was to estimate maximum entrained air flow rates based the geometry of the deep sewers and connected shafts (long section shown in Figure 4). To estimate maximum entrained air flow rates a pressurization model was developed by doing the following: - Derived simplified pressure loss/gain relationships for the sewers and drop shafts - Assuming bubbly or misty flow with air and sewage velocities equal. - Allowing for the compression/expansion of air along/down sewers/drops and the resulting change in mixture velocity along/down sewer/drops and the resulting impact on pressure loss/gain. - Based on conventional Colebrook-White friction factors and average fluid properties. - Forwards-calculated sewer flow rates based on input sewage and air flow rates at each drop. - Back-calculated sewer obvert pressure from the outfall to the sewer obvert for each drop based on the forwards-calculated flow rates, with iteration to allow adjustment and resolution of the resulting mixture fluid properties. - Used the derived pressure loss/gain relationship for the drops to calculate an air-sewage mixture column depth/height that would give the back-calculated sewer obvert pressure. - Used Newton's method to adjust the input air flow rates to give an air-sewage mixture column surface at drops below the incoming sewer invert by the distance necessary for the sewage to free fall to the mixture velocity at the column surface (as indicated in Figure 5). - With minimal sewage flows in drops downstream of the Ikea shaft, varied upstream sewage flow rates to indicate entrained air flow rates that could supplied to the Ikea shaft and the pressure at which they could be supplied (plotted in Figure 6 for three scenarios due to uncertainty of the exact location of the Ikea shaft in the network). A simplified model was selected for the evaluation because higher air entrainment rates are not considered plausible as there would be no driving force for air entrainment. The driving force for air entrainment is taken to be the deceleration of free-falling sewage entering the air-sewage mixture column. Maximum possible air entrainment is conservatively taken to be the air entrainment rate that gives an air-sewage mixture surface level at which there is no longer any free-falling sewage deceleration energy to drive air entrainment. Physically achievable air entrainment rates will be lower due to some energy being required to drive entrainment and overcome bubble rise velocities. This allowed for a flexible model that did not have high computational costs.↵ The model calculated that the maximum entrained air flow rates increase with obvert pressure before peaking and then declining with increasing obvert pressure, which is shown in Figure 6. These pressures were calculated to be well above the lifting pressure of cover slabs. Adequate venting of entrained air flow would be required to prevent high pressures developing under cover slabs. The analysis concluded that the historical depressurization incidents were a result of high entrained air flow rates and obvert pressures forcibly venting at the Ikea shaft. This location forcibly vents because the site lacks sufficient sewage inflow to prevents the obvert air pressure transferring to the surface. Being the first such shaft (in the direction of flow), it likely protected other downstream shafts without inflow that have a pressure retaining design. Other downstream drop shafts could also have a large vent grate or are much further downstream where obvert pressures are much lower and would therefore be less likely to violently depressurize. The maximum entrained air flow rates for the Ikea shaft indicated an order of magnitude increase in venting area was required. To mitigate this issue, GHD designed the new shaft cap in Figure 7 for the Ikea shaft with more than an order-of-magnitude increase in venting area, increased weight and some pressure balancing that reduces the net lifting force. This design enables a two orders-of-magnitude increase in the air flow rate that can be vented when compared with the previous cover slab (Figure 3). This was a relatively inexpensive modification that did not require complex models or deep energy dissipation structures to design and install. The methodology could be applied to similar sewers to assist with venting analysis and design without the need of more complex and computationally intensive modeling techniques. Modifications are currently in design and are expected to be installed prior to the conference.

The City of Chelsea, MA is strategically located as a gateway between downtown Boston and North Shore communities and is home to a vibrant, diverse population and industry that contribute significantly to the overall wealth of the region. Chelsea is served by the Massachusetts Water Resources Authority (MWRA) for water supply and wastewater collection. Many MWRA interceptors and a major regional headworks and pumping station are located in Chelsea. Like many other coastal communities in New England, Chelsea is serviced by a mix of combined and separated sewer systems that were built more than a century ago and are at the end of their service life. This outdated infrastructure hinders new development and growth, especially in the context of increased precipitation and coastal-induced inundation risk due to climate change. As a response to this concern, Chelsea has embarked on a city-wide master plan for sewer separation and infrastructure upgrades to systematically work towards attainment of the following three main goals: 1. Allow for future growth by progressively upgrading drainage infrastructure able to accommodate future population and increased stresses from climate change; 2. Eliminate CSOs by separating existing combined sewer areas and; 3. Reduce inflows to sanitary pipes from public and private properties that currently decrease available system capacity and increase operating costs to the City. In order to create this ambitious program, a significant modeling effort was carried out following a multi-step process. The first step consisted of building and calibrating a city-wide drainage model to help understand points with weak level of service and estimate peak flow and volumes reaching the MWRA interceptors and combined sewer overflows during dry and wet weather events. The City-wide model was built in Infoworks ICM using pipe network data from multiple sources such as record drawings, GIS, field inspections, and recently collected ground-level LiDAR information captured city-wide. The second step of the process consisted of developing conceptual level pipe layouts with the goal to achieve sewer separation city-wide and improve level of service. The conceptual level plans were developed using a 'best case scenario' approach (i.e. assuming an ideal drainage network can be built without necessarily accounting for other factors such as utility conflicts or permitting issues for new outfalls). The reasoning behind this approach was the desire to delineate a network able to attain optimum hydraulic performance based on natural topography and street layout and then work backwards, if needed, when conflicts identified during later phases of the process require this layout to be modified. The conceptual storm and sanitary systems were then incorporated into an Infoworks ICM model, which was used to fine tune the conceptual network (e.g. pipe slopes, pipe sizes necessary to provide the desired level of service or flow velocities for a given event). The third step was a planning level engineering effort where a street-by-street evaluation at each sewershed was performed. The feasibility and actions needed to go from the current condition to the proposed condition in the conceptual model were evaluated and alternative actions proposed when identified conflicts could not be resolved. The fourth and final step consisted of packaging and phasing the execution of the sewer separation and inflow reduction projects based on feasibility, City's priorities and constraints, as well as interim system conditions. This product is the City's new Master Plan for Sewer Separation and Drainage Infrastructure Upgrades, which will provide a systematic approach to drainage infrastructure improvements over the next few decades.

The first North American installation of the Cambi B6 modular THP was installed at the HRSD Atlantic Treatment Plant (ATP) in 2019 and started up in March 2020. The drivers for installing THP at ATP were to achieve Class A biosolids, maximize existing digester capacity, improve final product dewaterability, stackability and minimize storage requirements, in addition to receiving FOG to improve biogas production. Each year, the THP pressure vessels (Pulper, four Reactors and Flash Tank) require inspection, resulting in a planned shutdown of this critical system and requiring storage of liquid and dewatered solids upstream of THP as well as an interruption of feed to the anaerobic digesters downstream of the THP. This has also required temporary hauling of unstabilized pre-dewatered cake, as the liquid storage capacity at ATP is insufficient to store for the typical shutdown duration. At the ATP, as with many THP installations worldwide, there is no redundancy of the single Pulper and Flash Tank on THP train, and therefore it has been critical for the plant to develop and optimize processes to perform the required cleaning, inspection, and maintenance activities while minimizing the shutdown duration and expedite the return to normal operations. Since commissioning, HRSD has conducted four planned 'turnarounds', as well as experienced a handful of unplanned shutdowns that required quick responsiveness for repairs. After each shutdown, the staff have reevaluated performance, documented lessons learned and revised processes to improve the next one. Through this process of refining and updating guidance documents, for the third shutdown in December 2022, ATP had optimized to a 5-day shutdown, from stopping feed to the THP to returning the solids processes to normal operations. While this duration was in line with the most efficient Cambi B6 shutdowns at other installations in the UK and elsewhere abroad, it still required the hauling of unstabilized solids during the shutdown, approximately 15 solids trucks per day. Hauling operations are not only costly, but also increase the instance of odor complaints from the nearby neighborhood and high school adjacent to the WRF. Following the third shutdown, two Maintenance Operators (MO - maintenance staff) identified some innovative ideas that with the potential to shorten the shutdown enough to completely eliminate the need for hauling of unstabilized pre-dewatered cake. These ideas stemmed from their intimate knowledge of the THP equipment and their collaboration with the operators in order to have a comprehensive understanding of the operating requirements of THP and the capabilities and constraints of the solids handling system. The new approach was discussed at length internal to the plant and then further with HRSD leadership, as it was not without risks and the potential for extra costs. With support from all levels of HRSD, the fourth annual THP was conducted in December 2023. Prior to ever shutting down the THP and interrupting operation, maintenance staff worked with operations to sequentially remove reactors and cooling heat exchangers from service, cleaned and inspected them, all while maintaining the THP in service. The intent was to do as much as possible while still processing solids and feeding the digesters. At the same time, operations took the lead on preparing for the shutdown, managing the solids inventory strategically to maximize the available storage volume for the liquid solids upstream of THP. The actual shutdown of the THP lasted just over 24 hours, rather than the previous best practice of five days. HRSD completed the shutdown and cleaned the Pulper and Flash Tank and other critical parts and completed all maintenance activities in one day -- which is the shortest outage ever recorded by the many dozen operating Cambi THP facilities. This shutdown did not require any hauling of solids, and was performed by HRSD's own staff, other than the contract high-pressure cleaning services by Jet Blast. By eliminating the need for contract hauling and contractor staff to assist the MOs, HRSD realized a nearly $80,000 savings for the shutdown (Table 1). Through this process collaborating between O&M staff, the ATP has learned that many of the maintenance activities can be completed while service to the plant remains in operation. This paper will focus on the innovative ideas that arose from the collaboration between the ATP O&M staff, without which the no-hauling shutdown would not have been possible. Additionally, this presentation will provide lessons learned from this and prior planned and unplanned shutdowns and the approach taken by ATP to efficiently perform the required tasks while minimizing downtime. This presentation will benefit all WRF personnel, regardless of if THP is a part of the solids handling process. These lessons help ensure that the time for THP downtime, temporary operations and impacts to the rest of the solids handling processes are minimized. Most importantly, other WRFs will benefit from the experiences of the collaborative process conducted by HRSD to bring an idea from MOs to plant and HRSD leadership-- when everyone comes to the table with an open mind to reach a common goal. By empowering staff's creativity, WRFs can realize cost and labor saving innovations and at the same time demonstrate the value that everyone brings to the utility. This presentation will be presented by HRSD Maintenance Operators who were instrumental in planning and identifying innovative approaches for minimizing downtime and were key in executing this shortest Cambi shutdown on record. They will speak directly to their experiences, and how good ideas can be brought to supervisors for the good of the WRF. These speakers will be especially engaging to Operators and Maintenance staff. This presentation will allow time for and encourage questions and dialogue with the audience to learn not only about THP O&M details, how to collaborate as a team, bringing Operations and Maintenance together to execute complicated shutdowns and maintenance activities, but most importantly, how to foster a WRF culture that encourages and empowers staff at all levels to bring forth creative ideas for solving complex issues and how to support the execution of these ideas.

WSSC WATER is nearing completion of the Bio-Energy project to thermally hydrolyze and anaerobically digest all biosolids from their five Water Resource Recovery Facilities (WRRFs) at a centralized facility to produce a Class A biosolids. As part of this project, thermal hydrolysis pretreatment (THP) and mesophilic anaerobic digesters are being constructed at the Piscataway WRRF to provide the necessary stabilization to meet regulatory requirements as well as produce valuable digester gas, which will be converted to renewable natural gas (RNG) suitable for pipeline injection. See Figure 1 for an overall process schematic. The Bio-Energy project will fundamentally change how WSSC WATER manages biosolids, allowing a focus on long-term sustainable end products with a Class A dewatered cake biosolids, and RNG suitable for pipeline injection and use as vehicle fuel. The project will reduce the greenhouse gas emissions and result in significant operational cost savings. But with these benefits comes one of the biggest challenges of the Bio-Energy Project to treat the additional nutrient recycle loads that will be generated from sludge imported from the other WRFs and increased even more by THP and anaerobic digestion. Total nitrogen recycle loads from the Bio-Energy Project must be limited to ensure the Piscataway WRRF can maintain compliance with effluent discharge limits. A two reactor ANITATM Mox sidestream treatment process will startup concurrent with the digestion process to treat high ammonia filtrate from the Bio-Energy dewatering process. Managing filtrate generation in coordination with startup of both the Digester and Sidestream processes is essential to maintaining process compliance at Piscataway WRRF. Figures 2 and 3 present digester and sidestream treatment startup graphs. This presentation discusses the integrated startup plan for anaerobic digestion and sidestream deammonification at the Piscataway WRRF to meet multiple goals: - Stable startup of both biological systems, minimizing potential for digester souring, biological washout, etc. - Limiting nitrogen recycle to Piscataway WRRF - Expediting the commissioning schedule as much as practical to allow WSSC WATER to reap the benefits from this facility as soon as possible. Phase 1 Preparation and Seeding Phase 1 involves preparation and biological seeding of both digestion and sidestream deammonification, initially with one digester and one reactor. - Digester 1 will be partially filled with disinfected utility water to a minimum level to initiate pump mixing. The headspace will be purged with nitrogen to prevent an explosive atmosphere as methane concentrations increase. Steam will be used to bring the water to the mesophilic temperature range. Then liquid seed sludge will be imported from the DC Water Blue Plains Advanced Wastewater Treatment Plant (WWTP), which is thermally hydrolyzed and Class A. The digester is now ready to receive hydrolyzed sludge from the Bio-Energy THP process. - Sidestream deammonification has a similar preparation process. The first treatment reactor will be mostly filled with virgin media. Process flow from the WRRF will be introduced to the reactor to condition the media and promote biological attachment. Media conditioning will continue into Phase 2 - Digester Ramp Up to Piscataway Load. Once conditioning is complete, media with annamox biology from an operating ANITATM Mox process will be introduced to the reactor. The sidestream deammonification process is now ready to begin receiving filtrate. Phase 2 Digester Ramp Up to Piscataway Load Indigenous sludge from the Piscataway WRRF will be thickened, screened and dewatered prior to THP. THP throughput will be increased from approximately 4 dry tons/day (dtpd) up to the full Piscataway load, approximately 16 dtpd over approximately 30 days. During this ramp up, the ratio of volatile solids feed to volatile solids under digestion will be kept below 10%. At the end of Phase 2, Digester 1 will reach its normal operating level. Digester 2 will be prepared with water, nitrogen purge and heating before Digester 1 contents are split to Digester 2. Digestate will not be withdrawn during Phase 2 and no filtrate will be sent to the sidestream deammonification process. Phase 3 Sidestream Reactor 1 Startup and Initial Acclimation During Phase 3, digester feed will be held constant at the Piscataway WRRF load (16 dtpd). This period will be used to build the volume under digestion, establish robust mesophilic anerobic digestion microbial communities, and fine-tune operations prior to introduction of imported sludges. Digester withdrawal also begins during Phase 3 to generate filtrate to be used in the Sidestream Deammonification Reactors biological startup. Filtrate sent to the sidestream deammonification process will increase in both concentration and mass loading of ammonia (nitrogen), allowing the annamox bacteria to grow and acclimate to THP filtrate, increasing treatment capacity. During Phase 3, ammonia concentrations in the digesters and filtrate will also be increasing, and will be accounted for when calculating digester withdrawal and filtrate generation and dilution rates into the sidestream reactor. The sidestream process will start in moving bed biofilm reactor (MBBR) mode, with any sludge collected in the clarifier wasted to drain. Phase 4 Sidestream Reactor 1 Acclimation and Reactor 2 Preparation Digester 1 and 2 continue building the volume under digestion, establishing robust mesophilic digestion microbial communities, and fine-tuning operations during the 16 dtpd hold period. The influent ammonia concentration and load will be gradually increased to sidestream reactor 1. Dilution water will be adjusted to meet target feed concentrations and the mass loading will be gradually increased. RAS recycle will be initiated, and the sidestream process will convert from MBBR to integrated fixed-film activated sludge (IFAS) mode. Sidestream Reactor 2 will be prepared for startup, including conditioning of virgin media, introduction of seeded media and phased influent loading. Earlier startup of sidestream Reactor 2 represents an optimization from the initial startup plan, which deferred sidestream reactor 2 startup until reactor 1 was fully acclimated and performance tested. Phase 5 Increased Digester Loadings, Sidestream Reactor 1 Fast Acclimation and Reactor 2 Initial Acclimation After the digester 16 dtpd hold period, sludge will be imported from the four remote WSSC Water WRRFs to increase sludge to the Bio-Energy process. Both digesters will reach normal operating level, and digester withdrawal will be carefully managed to ensure filtrate does not overwhelm the sidestream reactor treatment capacity or exceed total allowable Bio-Energy recycle limits. While there is additional in-tank volume reserved for rapid volume expansion, once the digesters are full feed volume will generally match withdrawal volume, so sidestream treatment capacity must be sufficient to maintain total recycle load below plant limits. Sidestream Reactor 2 seeding and phased influent loading will commence at the conclusion of the Sidestream Reactor 1 slow acclimation period, and follows the same approach as reactor 1. Phase 6 Steady State Digestion and Sidestream Deammonification Phase 6 begins as the Bio-Energy process reaches full sludge load, with all indigenous and remote sludge being treated through THP and digestion. Both digesters will be in steady state operation. As Sidestream Reactors 1 and 2 complete ramp up to full treatment load capacity; startup will be complete, sidestream will be in steady state, and final operation and performance testing will commence. Conclusion Sidestream deammonification is critical to the successful implementation of WSSC Water's Bio-Energy Project, mitigating the impacts of increased nutrient recycle from THP and digestion with imported sludge from WSSC Water's remote WRRFs. The concurrent biological startups of sidestream treatment and digestion must provide stable startup of both biological systems while staying below nutrient recycle targets, all while maintaining an advantageous startup and commissioning schedule. The detailed planning undertaken for this facility allows for all parties to be fully informed and prepared moving into this integrated startup process.