Conference Agenda

The water industry is composed of a diverse mix of people and businesses with unique perspectives of how to use innovation and inclusion to solve water challenges. The Racial and Social Justice Subcommittee of PNCWA will host a panel with small women- and minority-owned business owners, utilities/clients, and larger (prime) firms in the water industry to talk about what it is like being a Minority, Women and Disadvantaged Business Enterprise (MWDBE), the strengths they bring to the water industry, and what challenges they face. This discussion will also provide an opportunity for both large and small firms to have a dialogue about ways to address challenges faced when working together.

This discussion is intended to provide insight into the MWDBE experience, share ideas for better engaging MWDBE firms and leveraging their strengths, and give recognition to the value these critical entities provide from both a technical and a diversity, equity, and inclusion lens.

The panel will have up to 5 speakers, including two MWDBE speakers (e.g., Osborn Consulting, Leeway Engineering), one utility/client speaker (e.g., City of Portland), and one person representing larger firms (e.g., Jacobs). The panel will be facilitated by the RSJ Subcommittee. The intent for this panel is to provide multiple viewpoints into the benefits all firms in the water industry can achieve from inclusivity and open communication, and to highlight how these benefits transcend the professional world and touch our communities.

Building relationships with underserved communities is a hot topic for many utilities. Though relationship building is an important first step, putting relationship building at the core of our efforts can inadvertently cause harm by consuming a community’s capacity without addressing their needs. This presentation focuses on putting community capacity and needs at the heart of our engagement. The first half will focus on applying a capacity-driven model for engaging with communities of color. How can we meet people where they are, augment their capacity, then stand back and let them lead when they are ready? The second half of the presentation will focus on integrating community benefits into project implementation. How do we look beyond the current subcontracting community to create economic benefit for those who need it most?

At the end of the day, relationship building is an important first step but it comes with a responsibility to turn those relationships into positive change for those we want to serve. Only then will we truly be integrating equity into our engagement and our work.

ART – FOR THE VITALITY OF THE PUGET SOUND
IF IT HITS THE GROUND, IT HITS THE SOUNDS – A local community-focused stormwater pollution prevention awareness campaign
ABSTRACT –
Every year, millions of pounds of toxic pollutants flow into the Puget Sound. Rain washes yard chemicals, vehicle fluids, pet waste, and more down street drains directly into the Sound. For over ten years, the City of Tacoma has actively participated in the regional Puget Sound Starts Here stormwater awareness campaign, partnering with other NPDES-permitted cities and counties throughout Puget Sound. Yet despite these efforts, in 2017, a community satisfaction survey conducted by the Environmental Services Department indicated that 50% of Tacoma residents still believe stormwater is treated before entering into our waterways. However, in reality, 90% of stormwater is not treated. In 2020, the City of Tacoma, Environmental Services (ES) embarked on a hyper-local stormwater awareness campaign to supplement Puget Sound Starts Here and engage our community through the work of local artists. The campaign is called “If It Hits the Ground, It Hits the Sound.”
Through this campaign, art is incorporated into pavement murals, vehicle wraps, catch basin stencils, t-shirts, and videos, to communicate the impacts of stormwater pollution in more visual and cross-cultural ways. The artistic format is especially impactful because local artists generate the art to raise awareness within their own communities. In addition to art, ES hosted events to create space for community members to learn about the issues and share experiences and ideas. While providing jobs to local artists, the campaign also brings public art installations into underserved neighborhoods, transforming community eyesores into assets, discouraging vandalism, and enhancing pedestrian thoroughfares,
This presentation will describe the genesis of the pilot campaign, as well as the next steps in building on campaign awareness by pointing community members to pollution prevention actions and support resources provided by Environmental Services, evaluating campaign effectiveness, and hopefully soon utilizing GIS data, including Tacoma’s Equity Index map and Watershed Prioritization tool to prioritize neighborhoods for future art installations.

In 2020, The City of Lakewood completed an update to the FEMA hydrologic and hydraulic model for Clover Creek, located in Lakewood, Washington. The update revealed the 100-year floodplain for Clover Creek is significantly larger than previously modeled. The newly identified floodplain has the potential to completely close critical infrastructure, life-safety and commerce routes such as Interstate 5 (I-5), Pacific Highway, Sound Transit rail lines, and transportation routes to Lakewood’s only hospital.

The City of Lakewood completed a planning level study to evaluate potential alternatives and their resiliency, to reduce flood extents and protect existing buildings and infrastructure. The goal of the study was to build a foundation for the development of measures to protect the City and infrastructure through a resilient and sustainable project.

Working collaboratively with the tribes, public, regulating agencies, and impacted entities, the study initially screened and prioritized more than twenty potential options. Once screening was completed, a more in-depth assessment of four mitigation measures was conducted which included: stream and channel enhancements; construction of new levees: one near I-5 or one near the creek; and a do nothing alternative.

The Stream and Channel Enhancement Alternative identified riparian areas and disconnected floodplains that could be expanded and reconnected to enhance the capacity of Clover Creek to reduce flooding and provide environmental uplift. The I-5 Levee Alternative identified a new levee to limit floodwaters from and west of I-5, while land east of I-5 would remain within the floodplain limits. The Clover Creek Levee Alternative is a setback levee that would limit nearly all flooding and protect critical infrastructure providing the most comprehensive flood protection. The Do Nothing Alternative provides no improvements to mitigate flooding likely resulting in a regulated floodway across I-5 and require many owners to secure new flood insurance.

Each alternative was evaluated with basic assumptions and geometry modifications appropriate for each model run, to understand potential benefits/impacts for each alternative. The presentation will discuss how the selected alternative provides the greatest benefit and most resiliency for the City of Lakewood.

The current National Pollutant Discharge Elimination System (NPDES) Municipal Separate Storm Sewer System (MS4) permits in Oregon (Permits) include significant new requirements for stormwater design standards that impact the design feasibility, facility footprint, and effectiveness of stormwater facilities. The Permits require prioritization of low impact development, green infrastructure, and retention in stormwater design standards. For retention, permittees are required to develop a Numeric Stormwater Retention Requirement (NSRR) that retains stormwater onsite and minimizes offsite discharge of pollutants. This presentation will cover methods and data assumptions used in evaluating local rainfall data to identify appropriate design storms for sizing Permit-compliant stormwater retention and water quality facilities.

For one permittee, an NSRR design storm was selected using the annual average runoff-based method to retain 80 percent of annual average runoff. The analysis considered hourly rainfall data from two local gages. The design storm was estimated using two rainfall analysis methods for comparison: a rolling 24-hour method and a storm-event method. The results were sensitive to the analytical methods and the assumptions used as input parameters for those methods such as inter‑event times and period of record from the two local gages. Design storm results differed in size by as much as three times.

For another permittee, after completing a rainfall analysis, a sensitivity analysis was conducted to look at the impact of a proposed NSRR on stormwater facility footprints for scenarios that included a range of infiltration rates, drawdown time limitations, and development types. Facility footprints varied by as much as four times depending on the scenario.

The selection of a design storm for onsite retention requires an understanding of the nuances and significant implications related to different rainfall analysis methods and associated assumptions. It is also important to understand the development characteristics where the retention design storm will be applied. Design storm selection based off a clear understanding of methods and assumptions will best support goals for sizing facilities. This will allow facilities to meet requirements for runoff treatment, address feasibility constraints for implementation, and right-size facilities to effectively manage stormwater runoff and protect water resources.

The questions we ask and answer in the planning and design of stormwater retrofit projects fall into two general categories:

1) What do we need? We usually call this planning.

2) What do we get? We usually call this design.

In stormwater management the answer to what we need is rapidly changing. When many of our storm systems were first built the answer was “we need to get water away as quickly and as cheaply as possible to prevent flooding.” Today, the answer is closer to “we need a multi-use solution to retain water on-site, limit impact to surface and ground water hydroperiods, reduce pollution and erosion to protect and enhance our natural and built environments, provide community assets for place-making and access to greenspace, and prevent flooding.”

When our understanding of what we need is rapidly changing, it is challenging to set goals at the beginning of projects because we don’t know what we can get, especially in highly constrained built-out environments with limited space. The goals must adapt and evolve through the design process. Therefore, the success criteria are less goal oriented, “Did we meet our goals?” and more process oriented “Did our process optimize our solution for functionality and value?”

What we need versus what we get are the two rails of communication that must be advanced together to navigate a successful project with multiple and competing constraints and goals. If one rail gets too far ahead of the other then progress can easily be stalled, sidetracked, or derailed. So how do we tie these rails together to get what we need? We usually call this modeling.

Recent stormwater management planning and design projects will be used as case studies to discuss how modeling practices such as initial conceptualization, identifying constraints and boundary conditions, making explicit simplifying assumptions, and identifying the right approach and level of detail at the right time can be used to determine if we can need less, or if we can get more to achieve successful project outcomes.

Hydrologic and hydraulic models are typically deterministic, making assumptions about input parameters and calculating a single result for each output. However, this simplification may result in cost-increasing overly conservative assumptions. Additionally, this approach is unable to quantify risk presented by low probability events.

For example, ODOT’s guidance for inlet spacing calculations is to use either 30% or 50% as a clogging factor, depending on inlet type and location. Wouldn’t it be nice to know how resilient a collection and conveyance system is if some inlets are more substantially clogged during large storms?

In this talk, Seth will present the basic theory of probabilistic/stochastic approaches to modeling and disucss some applications this is already considered best engineering practice. He will show examples using Monte Carlo simulations with common tools like EPA SWMM and HEC-RAS to create probability curves of the model outputs. The talk will include specific references to open-source Python toolkits that will help others considering creating probabilistic models.

Finally, the talk will address potential uses including risk informed decision making processes, especially with regards to climate change risk, and sensitivity analysis applied to existing deterministic models. It will also discuss some of the limitations of this approach and seek feedback from the audience members who may use similar approaches.

The past decade has seen a wave of research and development of new technologies that allow for “process intensification” – those technologies developed to increase wastewater treatment capacity using less site footprint and/or tankage volume. These intensification technologies will be instrumental in addressing nutrient limitations from treatment facilities discharging to the Puget Sound. Such newer breakthrough technologies include aerobic granular sludge (AGS), mixed liquor densification, membrane aerated biofilm reactors (MABR), and mobile organic biofilm (MOB) technologies. Compared to these technologies, the Integrated Fixed-film Activated Sludge (IFAS) process, considered one of the original process intensification technologies, is now well proven and fully established, having been developed and applied since the 1990s. With the fervor at which these newer technologies are being embraced, the question that has arisen in the industry is this: Is the IFAS process still a viable technology?

This purpose of this presentation is to examine through performance of full-scale IFAS implementations whether the known benefits of IFAS technology (e.g., process robustness, ammonia-nitrogen removal for cold wastewater) outweigh the known drawbacks (e.g., higher aeration demands). Case studies of IFAS facilities are presented, highlighting the advantages and challenges of implementing this technology at four facilities: 1) Bend Water Reclamation Facility in Oregon/USA; 2) Field’s Point Wastewater Treatment Facility in Rhode Island/USA; 3) Twin Falls Wastewater Treatment Plant in Idaho/USA; and 4) Ellesmere Port Wastewater Treatment Works in the United Kingdom. The facilities have all been operating with the IFAS technology for a number of years, allowing investigation into the long-term benefits and limitations of the process. All of the facilities are able to meet their respective nutrient removal goals, providing the warranted capacity and performance requirements. Some of the facilities; however, have experienced higher than expected energy demands – specifically with respect to the seasonal air demand anticipated with the system. The viability of the IFAS intensification technology will be proven, specifically for site-constrained facilities that require improved total inorganic nitrogen removal, in documenting the success of these facilities. The shortcomings, and warranted improvements to the IFAS technology, will also be discussed – using lessons-learned from these projects.

The City of Peterborough Wastewater Treatment Plant (WWTP) is an 18 MGD conventional activated sludge plant in Southern Ontario, Canada. The plant consists of 4 aeration trains, originally designed for conventional suspended growth. The trains were converted to a moving media Integrated Fixed Film Activated Sludge (IFAS) system in 2006 (Plant 1) and 2011 (Plant 2). The system consisted of non-engineered plastic matrix material within metal media retention cages in the first pass of each tank. The moving media system had several operational challenges including media loss, non-uniform dispersion of media, increased hydraulic head loss, screen and diffuser maintenance difficulties.

The City of Peterborough retained R.V. Anderson Associates Limited (RVA) to implement an alternate IFAS system that would address problems with the existing configuration. Various alternatives were evaluated in terms of retrofit requirements, Operations and Maintenance (O&M) obligations, life cycle costs, Environmental Compliance Approval (ECA) requirements and other criteria. The selected fixed media IFAS system was the WavTex^TM woven media system by Entex Technologies Inc. (Entex). It included a total of 32 modules, each having buoyant media sheets tethered to 304L stainless steel support frames with integral coarse bubble aeration. This paper/presentation will go into details of the evaluation/selection and operation of the new IFAS system.

The final aeration tank with the new IFAS system was put in service in December 2021. To validate the system performance, testing during cold weather winter, high flow spring, and high temperature summer was required. The performance was monitored for Total Ammonia Nitrogen (TAN) removal at the rated capacity. The new Entex system was able to consistently meet TAN limits of 6 mg/L (summer) and 10mg/L (winter).

Based on the TAN results, ease of operation, and reduced O&M costs the new system proved to be able to meet the plant’s needs. Further details including testing methods, other parameters tracked, and plant performance will be discussed in this paper/presentation. At the end of this project, the City of Peterborough WWTP was able to install and validate an alternative IFAS system to address O&M issues which also met effluent requirements for the full rated capacity.

Partial denitrification (PD) is being considered as a potential alternative to partial nitrification (PN) for generating nitrite. This is due to the difficulty of suppressing nitrite oxidizing bacteria (NOB) at low mainstream temperatures and nitrogen levels. The Partial Nitrification/Denitrification/Anammox (PdNA/PANDA) process is an innovative way to remove ammonia from the mainstream by partially nitrifying it to nitrate, while leaving some residual ammonia in the post-anoxic phase. In this phase, the residual ammonia and nitrite generated by PD are removed via Anammox. The moving bed biofilm reactors (MBBRs) are often used as a tertiary polishing process for biological nitrogen removal (BNR) to meet the permissible total nitrogen (TN) limit of 3 mg/L. However, this requires large amounts of external organic carbon for denitrification. By replacing conventional BNR with PdNA/PANDA, energy savings and chemical savings of up to 60% and 80%, respectively, are projected. While PdNA/PANDA has been used to reduce carbon and aeration demand in mainstream biological nitrogen removal, its applicability in tertiary processes with low influent nitrogen loading (TN < 7 mg/L), frequent storm-related loading fluctuation, and stringent effluent TN limit (< 3 mg/L) has not been explored. Additionally, previous PdNA/PANDA studies have only been performed in lab- or pilot-scale systems. This presentation will highlight the experience and lessons learned from two pilot-scale PdNA/PANDA systems from two different utilities (Fairfax VA and Everett WA), and some ongoing works that effectively demonstrate full-scale mainstream deammonification via PANDA while meeting stringent nutrient limits. The major insights from pilot-scale studies are: 1. the PdNA/PANDA system can achieve effluent TIN limit of 3 mg/L at the design HRT/load/flux; 2. practical savings ranging from 20% to 30%; 3. feed forward methanol feeding control strategy can provide means for achieving stable PdN; 4. optimizing the influent NO3/NH3 ratio is the most critical step for successfully PdNA/PANDA. The major insights from the full-scale study are: 1. startup without seeding can be achieved in under 3 months while still meeting very low TN and ammonia limits; 2. chemical savings of approximately 30% are in line with pilot-scale studies.

The purpose of this presentation is to share the commissioning and start-up (C&SU) approach, execution and lessons learned of the first Thermal Hydrolysis Process (THP) built in Texas, and the second largest THP system in the United States, designed to process 375,750 dry lbs/day.

The Trinity River Authority’s (TRA) Central Regional Wastewater System (CRWS) serves 1.4 million customers in Dallas metropolitan area, with a treatment capacity of 189 MGD. CRWS’s Phase III B Solids Management Improvement Project includes replacement of the current lime stabilization treatment process with THP and anaerobic digestion. The goal of the Project is to significantly reduce the volume of biosolids produced and improve the classification from Class “B” to a Class “A” biosolid, which can be land applied or sold as fertilizer.

The biosolids treatment conversion from lime stabilization to THP and anaerobic digestion required both processes to operate in parallel. Due to the volume of equipment, impact to existing operations and risk associated with the activity MWH, in collaboration with TRA operations, developed a C&SU phased approach to facilitate the transition. The goal of the phased approach was to mitigate unknown process risk and minimize the impact to TRA’s daily operation. One example of risk mitigation occurred during Pre-THP Process Startup phase. Upstream of the THP system, there is a series of pre-dewatering equipment needed to be optimized with process fluids prior to introduction to the THP system. During process start-up the C&SU team identified the centrifuges were rotating backwards, despite extensive factory acceptance testing, field inspections, and water startup with the equipment vendor. This issue could only have been identified when process fluids were introduced into the system. If the team had not completed Pre-THP Process Startup the equipment reconfiguration would have impacted THP startup and Digester ramping, risking the loss of biomass following Digester Seeding.

Throughout the Pre-THP and THP startup, the team worked through numerous challenges to troubleshoot and optimize the systems. This presentation will explain how the team resolved each challenge and share lessons learned, resulting in the successful C&SU of the pre-dewatering equipment and THP system.

The Northwest has embraced watershed planning for over twenty years as a useful way to prepare for and implement strategies to improve the health of waterways while effectively managing limited budgets and staff resources.

Now, there are new challenges facing watersheds that Parametrix has begun to integrate into watershed planning and will discuss in this presentation.

Parametrix has worked with multiple jurisdictions to develop integrated watershed plans and long-term growth management studies. Parametrix has worked with 20 plus communities on integrated watershed planning from large to small.

As part of our planning process, we will discuss how to address long-term management of existing municipal systems while also plotting courses for future land use development and responsible growth. Parametrix will discuss how to set goals; determine strategies; and define actions and funding strategies for risk management, environmental stewardship, climate change, and compliance with stormwater regulations as the population of a watershed grows.

This presentation will discuss key elements common to integrated watershed planning, including:

- Land use planning that is compatible with watershed protection targets

- Watershed prioritization and identifying key water quality issues within watersheds

- Systems for scoring and ranking needs to prioritize elements within a capital project plan

- Equity and social justice

- Retrofitting and neighborhood redevelopment

- Green infrastructure evaluation and code review

- Solutions to existing flooding problems

- Asset management and prioritization of existing infrastructure

- Managing project milestones to support public-agency grant funding

- Public awareness and involvement

- Utility rate analyses for different funding scenarios and levels of service

Parametrix will also discuss several innovative approaches that have proven successful across these different plans:

- Developing a stormwater management vision and mission, identifying measurable outcomes for each plan element, and discussing risks early on

- Straight-forward ways to address the impacts of climate change in existing design requirements

- Basin-specific water resource protection standards

- Updating development standards, including infill, redevelopment, new site development, and water quality retrofits based on a more integrated understanding of potential impacts

- Use of key habitat-quality metrics to help prioritize protection and development efforts

Nestled within Seattle’s Washington Park Arboretum is the Arboretum Creek, which flows northward into Lake Washington's Union Bay. As with many urban streams, this creek was suffering from the impacts of deforestation, underground piping, urbanization, and flow diversion that started more than 100 years ago. In the 1920s, several hillside springs were diverted into the combined sewer system that ultimately now contribute to historical combined sewer overflows at the Montlake Cut. The nonprofit group Friends of Arboretum Creek (FOAC) has advocated for and led Arboretum Creek restoration efforts for several years. This presentation will share the development of partnerships and plans to restore the natural hydrology of the Arboretum Creek watershed by reconnecting two of the major springs with Arboretum Creek while also addressing localized flooding and treating stormwater runoff from a major arterial. The location of the headwaters is rich with history and community interest, including being an Olmstead Brothers park, the site of UW Arboretum collections and Japanese Gardens as well as a complex array of asset owners to coordinate across. This meant that the design requires close collaboration with partners to achieve not only water quality improvement but also enhance these valuable community resources.

Through funding by King County Wastewater Treatment Division with support and collaboration from the Seattle Parks Foundation, FOAC is developing design plans to collect runoff from the two springs as well as upstream urban runoff and convey the flows to the Arboretum Creek headwaters. These flows will be managed through a treatment train with easy-to-maintain upstream presettling and a subsurface treatment wetland, and ultimately arrive at the creekbed through hyporheic discharge. But wait, there’s more! The treatment wetlands will also be optimized to treat overflows from the adjacent Japanese Garden koi pond to address nutrients reduction. The presentation will highlight elements of the innovative design and summarize the collaboration and funding opportunities with partners to maximize benefits while integrating with the Washington Park vision and enhancing the horticulture collection within the park.

Many US cities have aging sewer infrastructure that was built prior to environmental regulations and the development of modern urban transportation networks and associated population growth. As a result, many pipes were built in ravines, streams, and low-lying areas that were subsequently filled and built upon. As these systems age with existing challenging maintenance access, now is the time to evaluate and build more resilient sewer systems that reduce environmental, maintenance, and public safety risk. This presentation will discuss the challenges and benefits of simplifying an aging sewer network by abandoning part of an urban sewer system and reversing the flow of an existing sewer pipe.

The City of Portland identified several thousand feet of combined sewer pipe in north Portland for rehabilitation due to mortality risk, hydraulic capacity risk, and operation and maintenance risk. Some of these sewers are located 20-50 feet below ground in an urban park crossing arterials, highways and abandoned rail. Results from an alternatives analysis proved the hydraulic feasibility of abandoning most of the difficult to access pipes within the park and reconstructing the upstream pipe to reverse the direction of flow within the City’s right-of-way. This creative solution avoids significant community disruption, reduces interagency coordination, and provides better access for future maintenance.

Reconnecting service laterals and catch basins to the reversed mainline presented the biggest challenge to flow reversal. In some sections, the proposed invert elevation is as much as 10 feet above the existing invert elevation. Additional topographic survey and potholing was needed to confirm the feasibility of reversing flow without pumping. Despite the complexities of flow reversal, this solution offered an overall benefit to the City of Portland and rate payers by simplifying maintenance and reducing the overall risk within the system.

King County’s Mercer and Enatai Interceptors were built in the 1960s and extend over 14,000 feet from northern Mercer Island into the Enatai neighborhood of Bellevue, Washington. The interceptors receive flows from North Mercer Pump Station, as well as the City of Mercer Island and City of Bellevue sewer systems. Some parts of the system are reaching the end of their useful lives, and future peak flows are projected to soon exceed the system’s capacity.

The new $58 million Mercer Enatai project includes two upgraded pump stations and a 4-mile sewer alignment that passes underneath residential streets, a major arterial, a regional bicycle and pedestrian trail, a navigable waterway, the Enatai hillside, a swim beach and park, and an environmentally-sensitive wetland. The numerous and varied stakeholders needed to be appropriately engaged with the right information at the right time, and in a way that is meaningful for each stakeholder group.

To uphold King County’s goal of being a good neighbor, the project team worked collaboratively, utilizing traditional outreach methods such as open houses, fliers, community events, and small group meetings. The team also used less common methods such as “walk and talks,” bike rides, online open houses, digital presentations, and targeted outreach for specific populations. The Covid-19 pandemic required a quick shift to virtual engagement.

This presentation will review the entire toolbox of outreach methods the project team used during the different phases of the project, and share thoughts on the lessons learned, varying degrees of success, and potential future approaches to engage communities on projects from cradle to grave.

The Sand Island WWTP is the largest treatment plant in Hawaii, serving Honolulu and surrounding areas and treating an average flow of 65 MGD. The facility currently provides preliminary treatment, chemically enhanced primary treatment, and UV disinfection prior to discharge through a 2.4-mile outfall. The WWTP is located on a highly constrained site adjacent to public recreation facilities, industrial facilities, and the primary access road from the island of Oahu to Sand Island located in Honolulu Harbor.

The City and County of Honolulu entered into a Consent Decree to upgrade the Sand Island facility to secondary treatment standards, and recently began construction of a 20 million gallon per day (MGD) membrane bioreactor (MBR) facility as Phase 1 of the secondary expansion. Phase 2 of expansion will provide the additional 90 MGD of secondary treatment capacity required to meet full secondary standards and support future growth. Phase 2 will also add peak flow equalization, upgrade preliminary and primary treatment, and expand solids treatment processes to treat the additional waste activated solids generated by the new secondary process.

Previous planning evaluated a wide range of secondary treatment technologies for the Phase 2 expansion, however since the site was not intended to support full secondary treatment, only intensified processes including MBR, biological aerated filters (BAF), and aerobic granular sludge (AGS) are able to provide the full secondary treatment capacity required within the footprint available. The 90-MGD Phase 2 expansion would represent one of the largest facilities in North America using any of these technologies, therefore the City conducted extensive investigation including detailed process evaluation and site visits to nine large facilities in the United States and Europe. A large group of City stakeholders evaluated the secondary process alternatives based on qualitative and quantitative criteria, relying on technical information from the design team and operational experience and performance shared by utility peers during site visits.

This presentation will describe the evaluation conducted to assess the large-scale intensified treatment processes considered for the Phase 2 expansion, review the City’s selected process, and describe how the technology is being implemented.

A major barrier to quantifying the true cost of grit is these costs are typically accepted as routine maintenance assigned to different parts of the plant so the root cause may not be identified as the common denominator. If grit is not managed by removal in the headworks it will continue onto downstream processes and must be managed throughout the plant. Grit deposits in downstream process tanks, taking up space, reducing retention time and increasing velocity which impacts treatment efficiency. Grit deposition in the aeration basin can increase energy requirements needed to achieve proper treatment. Accumulation in digesters can create unstable operating conditions by reducing volatile solids destruction, impairing mixing, and reducing gas production. To remove deposited grit basins must cleaned. Digester cleaning is expensive, dangerous and time-consuming, requiring taking the basin offline, exposure to toxic gasses, confined space entry, repairs and recommissioning, not to mention removing, handling and disposing of the deposited material. Grit is also responsible for abrasive wear to virtually all mechanical equipment.

All plants are interested in improving efficiency, reducing O&M costs, improving plant performance and reducing energy requirements or moving towards energy neutrality. If plant staff could monetize the cost of bypassing grit process improvements could be justified.

The purpose of this paper is to provide tools to understand effective design points for grit removal systems and assess the true cost of grit while shedding light on why the grit removal process is important.

Water and Wastewater Membranes need to be protected against fibrous & sharp debris. This not only protects all downstream systems & monitoring equipment, including water & wastewater membranes from premature surface abrasion & clogging, but site studies have shown that 1.0 mm & 0.5 mm aperture membrane pre-screening significantly reduces the annual number of membrane desludging/cleaning cycles by up to 3-fold. It also reduces the labor intensity of each cleaning cycle while eliminating clogging of aeration manifolds that scour membrane surfaces. Fine Pre-screening has become extremely important in protecting both membrane warrantees and lifespans. Laboratory & field experiments prove the vast majority of debris is caused by chopping & maceration equipment installed at pump stations or inside plants to protect downstream equipment from disposable wipes & plastics flushed into our sewer systems. The presentation will emphasize the importance of fine screening with data showing how short, fine cotton-wool-polyester fibers, human hair, as well as filamentous algae will pass through 6.0 mm, 3.0 mm and 2.0 mm aperture screens and “Recombine” downstream into larger rag type debris that increases the operating maintenance & cleaning cycles of all downstream systems and monitoring equipment. The Presentation will also include supporting pilot plant & field data that focuses on why velocity & headloss are the two most important operational characteristics in understanding how screens are properly sized, maintained & operated. Computational Fluid Dynamics Analysis (CFD) with (SCR) Screening Capture Ratio data will reveal the direct relationship velocity & headloss have on a screen’s capture efficiency & performance. It will also emphasize the aperture requirement for removing 2 dimensional versus 3 dimensional solids. A screen’s effluent quality affects the lifespan, operation & maintenance of all downstream systems & monitoring equipment. Headworks and membrane protection screens share the same velocity and headloss limitations that affect their performance and debris capture. Both lab and site test data will demonstrate and support the shared conclusions of this presentation. Whether the drivers are regulatory, reuse or to improve downstream process efficiencies, the trend has been to remove non-biodegradable debris, algae & aquatic remains from influent flow.

Lake Ontario is the primary source of drinking water for approximately half the population of Ontario, with the majority of that population residing in the Greater Toronto Area (GTA). In 2013, Source Water Protection studies identified sensitive areas near the drinking water intakes where the risk of impacts from accidental spills is considered a credible threat to human health and safety. A spill causing an acute contamination event at one of the water supply intakes could have catastrophic impacts to the population. However, the ability of stakeholders to assess the potential impacts and develop an appropriate response is presently limited to static planning level studies and maps. These proved to be useful tools for identifying the potential locations where pollutants may show up, but they did not provide any indication of the potential risks due to the conditions in the lake at the time of the spill.

In 2019, the Ontario Clean Water Agency together with the City of Toronto, Region of Peel and Region of Durham hired DHI to develop the Lake Ontario Water Quality Forecasting System (LOWQFS). The LOWQFS assists in evaluating the likelihood of a pollution event originating from any discharge source within, and adjacent to, Lake Ontario being transported to any one of the water treatment plant intakes located along the Greater Toronto Area (GTA) waterfront. The system collects climate forecasts and uses it to update a 3D hydrodynamic model of Lake Ontario to predict the water level, currents and temperature throughout the lake. The system also includes a Spill Forecasting tool for on-demand creation of spill events that are run using the latest hydrodynamic forecast. The results are made available for plotting of spill concentrations on a map and in time-series plots, and impacted water intakes are identified and reported to relevant stakeholders.

The system is currently in operation and emergency response plans are being updated to integrate the use of the LOWQFS into the protocols and workflows.

Environmental DNA (eDNA) refers to DNA shed by organisms into the environment, and can be captured in water, soil or air samples. By identifying DNA captured in a sample, we can infer species present within a given environment. As such, eDNA is a promising tool for understanding spatial and temporal variation in biodiversity across a watershed. Clean Water Services (CWS) is a water resource and recovery district serving Washington County, Oregon. CWS discharges to the Tualatin River, a meandering, valley-floor river, sensitive to nutrient inputs and stream flow augmentation. Accordingly, our watershed-based NPDES permit directs CWS to monitor the biological characteristics of 15 sites within the watershed each permit cycle. This work is typically completed using macroinvertebrate surveys, which are costly and limited in biological scope, and therefore provide limited information. Given eDNA’s promise as a means for characterizing broader biodiversity between sites, we are piloting eDNA as a novel method for gaining detailed biological information, that could potentially be used in the future in-place of traditional macroinvertebrate surveys. The first phase of a multistep project has been to monitor nine sites representing diverse habitats within the Tualatin River Watershed, on a monthly or quarterly basis through a metabarcoding eDNA approach using water and sediment samples. This presentation will discuss the observed differences in biodiversity between sites over the course of a year, and whether eDNA metabarcoding data can be used to assess temporal shifts in species-use at a particular site or habitat area. Additionally, we will demonstrate how aquatic algae identification via eDNA compares to morphological identification via microscopy, and suggest how this comparison may inform future studies. Finally, we will discuss how we plan to use these data to develop a framework for regularly monitoring biological characteristics to demonstrate the effectiveness of our watershed enhancement actions and in fulfillment of our NPDES permit.