Conference Papers

INTRODUCTION
Hydrogen Sulfide (H2S) is a byproduct from anaerobic digestion and when released into the atmosphere it can cause an offensive odor and is dangerous in high concentrations. Processes that produce H2S include wastewater treatment plants, sewers, piggeries, and landfills. Biological odor treatment is a method used to treat offensive odors in an efficient and environmentally friendly method but can be cost-prohibitive for small applications with low concentration. The goal of this project is to lower the cost of biological treatment of odors by introducing an odor concentration step. The concentration step is meant to reduce gas intake volume into the biological treatment system while supplying gas at a higher H2S concentration than produced by the source. The lower gas volume generated reduces the operating cost and size of the biological treatment system. Biological odor treatment has the potential to be more widely used by lowering the operation and installation cost. The test setup of this system is located at the Loup Central Landfill located near Elba, Nebraska. The landfill consists of 7.5 acres that has been filled with 402,000 yards of household waste from 1996 to 2016. An intermediate soil cover was placed on the 7.5-acre area in 2016. There is also a 10-acre area that is currently being filled with household wastes. The project has three main goals: 1) design a three-part biological treatment device, 2) install device at the Loup Central Landfill, and 3) monitor the device's effectiveness at treating H2S.

DESIGN AND OPERATIONAL APPROACH
The key assumption made when designing the system is that the landfill can supply a steady concentration of 1 part per million (ppm) H2S at a flow rate of 2 liters per minute (lpm). The biological treatment system consists of three different steps: (1) collection, (2) concentration, and (3) biological treatment. See Figure 1 for an overview of the biological treatment system steps. Collection System The collection system connects directly to the leachate cleanout system of the Loup Central Landfill. The leachate cleanout system is a network of perforated piping that lies underneath the landfill. There is a total of seven manholes at the surface level that connect to the leachate cleanout system. Figure 2 provides a map of the Loup Central Landfill with cleanout locations. Twenty-five feet of half-inch solid, plastic piping is placed down into the cleanout through one of the seven manholes. Due to the slope of the cleanout pipe, the end of the half-inch piping will sit six feet below the surface. A vacuum pump operating at a constant gas flow rate of 2 lpm is connected to the surface end of the piping. The pump directs H2S laden air into a flow controller. The flow controller directs the flow to the three different columns of the concentrator system. Concentrator System The concentrator system consists of three columns filled with activated carbon that operates in programmed flow-cycle. The cycle for each column consists of a lead phase, lag phase, and desorption phase (See Figure 3). In the lead phase, the flow controller directs the H2S laden gas from the landfill into the first column. The gas slowly saturates the column with H2S. The lag column collects the gas coming out of the lead column and acts as a polishing unit. The gas exiting from the lead phase column is at zero H2S concentration until saturation occurs. Simultaneously, there is a third column going through the desorption phase. During the desorption phase, air passes through the heated column. Studies are still being conducted on different desorption methods. The lead-lag column system consists of two columns in series. The lead column adsorbs most of the H2S while the lag column acts as a polishing tool to safeguard against exhaustion of the lead column. The fluid controller directs the low-H2S concentration gas and desorption fluid to one column at a time. The entrance for each column has a four-way cross to direct the flow from the three different fluid sources. At the exit of each column, there is a solenoid valve to direct the flow to either the next column for the lag phase or to the bio-trickling filter. Figure 4 shows the flow configuration of the concentrator system. The red flow lines indicate low H2S concentration gas coming from the landfill directed to the lead column and subsequently the lag column. The blue lines indicate the desorption fluid sent to the desorption column. The black line directed toward the bio-trickling filter indicates a fluid stream with a high H2S concentration. Biological Treatment System The biological treatment system is a bio-trickling filter. A bio-trickling filter is a column packed with inorganic material that is inoculated with micro-organisms. A polluted gas stream and trickling liquid slowly pass over the packed bed where the micro-organisms digest the pollutants transferred into the liquid stream. The bio-trickling filter is a PVC pipe packed with plastic material inoculated by activated sludge from a local wastewater treatment plant. Concentrated H2S gas is supplied to the bio-trickling filter by the concentrator system. A nearby water tank is pumped at a slow rate into the bio-trickling filter to transfer the H‚‚S into the liquid form. The dimensions of the column are dependent on the flow rate of the H2S gas exiting the concentrator system. The aim is to have an empty bed residence time of 60 seconds or more. Figure 1 provides a diagram of the bio-trickling filter included in the system overview.

RESULTS
The properties of the landfill, the desorption fluid, and the activated carbon directly impact the overall design of the biological treatment system. The main factors that affected are the cycle times in the concentrator system, the size of the concentrator columns, the amount of activated carbon in each column, and the size of the bio-trickling filter. The landfill affects the design based on the H2S concentration extracted out of the leachate cleanout. The H2S concentration is directly proportional to the amount of activated carbon required and the column saturation rates. Figure 5 shows the results of a two-day study on the H2S concentration extracted from the Loup Central Landfill. The gas extracted from the landfill ranged from 0 to 50 ppm H2S during the testing period. Figure 6 shows the range of H2S concentrations extracted from Cleanout #1, #2, and #3. The important characteristics of the activated carbon are the densities, H2S adsorption capacity, and ability to desorb H2S.

SUMMARY
The overall system design is an ongoing continuing project. The system will be functional at the Loup Central Landfill in the summer of 2021.

Promises are the uniquely human way of ordering the future, making it predictable and reliable to the extent that this is humanly possible.' — Author Hannah Arendt. In a complex world of remote work, generational differences, racial inequities, social media and a growing distrust of government — what better way than a promise to deliver predictable and reliable outcomes? Like many businesses, Toho Water Authority (Toho), a utility located in Central Florida, had a Vision, Mission, Values. This 'tried and true' set of statements highlighted what every utility is about — reliability, cost effectiveness, excellence, and protecting public health and the environment. While fitting for budgets, websites, financial reports and other official documents, statements like this are rarely remembered and often don't resonate with employees. How then, can this approach be expected to drive alignment and connection to targeted outcomes? In order to reflect the passion of public service that we strive to deliver, we retooled to adopt a succinct mantra called the 'Toho Promise' — a measuring stick for all of the utility's 350 employees. We will share the highlights of this journey. During this interactive presentation featuring specific successes and challenges, attendees will learn about transforming this simple idea into a winning strategy. Lessons learned will highlight milestones and revisions that led to the transformation through change management tools that can be adapted to help other utilities create executable plans and realize the customer value of having a company promise, beyond a company vision and mission statement. Daily Promises Kept Through the transformative journey, this Florida utility discovered that the Promise connects with its employees, reflecting the values, behaviors, and culture that public servants embody — most importantly transforming a philosophy into an actionable expectation for every day and every action. Through a methodical process, the Promise was unveiled and rewritten until streamlined — read 'simplified.' Ten words, three audiences and a powerful commitment. Undaunted by brevity, the tone was deliberate and the simplicity memorable. Employee photos further personified the intention of the words. The most powerful part of the promise was the morale building ideal that, no matter an employee's role or function within the organization, they were responsible for Toho keeping its Promise. That newfound power enhanced pride in workmanship and commitment to overall customer satisfaction that actively resides within all facets of the utility today. Principles and Priorities Added To enhance the Promise, Toho outlined four Priorities — 1) Providing safe and reliable services, 2) Protecting the environment, 3) Delivering value, and 4) Investing in the future. Our employees then defined a set of Principles they would put to work every day — taking ownership of 'how' Toho delivers on its Promise. The essentials from these steps will be shared with attendees who can takeaway lasting impacts and lessons learned using an interactive approach sure to inspire others who may be seeking similar solutions. Tools used as part of this change management process will be shared and highlighted. Toho's Promise is more than a statement. Even as our organization grows in service area, as new employees join the organization, and as our demographics change, it is who we are and who we want to continue to be. It is how Our Customers, Our Community, Our Employees Trust that Toho Cares.

The City of Hampton (City) recently finalized a Downtown Hampton Master Plan to guide future growth and enhancement of its downtown area. The plan includes improved street networks, additional green space, new housing, and commercial space. A key goal of the plan is to improve connections between the core downtown and the waterfront. Under Virginia stormwater regulations, implementation of the Downtown Master Plan will require reductions in pollutant loading to surrounding the water bodies such as the Hampton River and Chesapeake Bay. In support of this plan, the City also developed a Downtown Water Quality Master Plan to support their Downtown Master Plan development. The overall goal of the Water Quality Plan is to provide a pathway for the City to achieve pollutant reduction requirements and advance other City initiatives as the Downtown Hampton Master Plan becomes a reality. In accordance with Virginia's stormwater regulations (9VAC25-870-63), each redevelopment in the downtown area will require a 20% net reduction in pollutant (phosphorus) loading to the Hampton River and Chesapeake Bay, relative to the pre-redevelopment loading. The City intends to achieve this requirement by implementing water quality projects throughout the Downtown Hampton area. To select these sites, a project selection framework was developed to advance each of the City's goals including Resilient Hampton initiatives and increasing greenspace in the area. This presentation will discuss the development of the site selection framework, conceptualization of each stormwater treatment facility, and the final results of the study. Attendees will gain an understanding of stormwater treatment, site selection techniques, and insights into urban stormwater design.

ASTM Committee E64 on Stormwater Control Measures (SCMs) has published a series of new standards relating to specifications and performance protocols for manufactured water quality treatment devices (MTDs) including hydrodynamic separators (HDSs), media filters, and trash & debris capture technologies. These consensus-based ASTM standards have been developed to objectively measure the performance of these technologies to provide improved assurance on the efficacy of tested and verified technologies. This presentation will discuss the ASTM standards process and how it produces consistent quality procedures and products for the benefit of all stakeholders. An overview of these standards will be provided to gain insight into their rationale and essential elements. This presentation will also explore the potential benefits of using these standards as part of an SCM regulatory program; and what implementation of these standards within an authority having jurisdiction (AHJ) could look like. The prospect of a national validation process for ASTM standards via the Stormwater Testing and Evaluation of Products and Practices (STEPP) initiative will also be discussed. The overall intent of the ASTM standards process is to provide a high level of confidence to AHJs that the MTDs will provide long term and consistent treatment to meet water quality goals. Two E64 Subcommittees have been established to develop standards for both laboratory and field testing as E64.01 and E64.02, respectively. To date, laboratory standards include general specifications, standards applicable to HDSs, standards for media filtration, and a standard for trash & debris capture. General specifications address standard terminology for SCMs, silica-based test sediment and weighting factors for TSS removal on an annual basis. HDS standards and working items apply to TSS performance testing methods and data analysis, hydraulic characteristics and head loss, as well as scour testing to support online installations. Filtration standards and working items consider hydraulic characteristics, test sediment, performance testing and scour testing. The trash & debris capture standard is unique to laboratory protocols since it applies to manmade and natural materials >5 mm (5,000 microns) in two directions and uses a 'cafeteria style' approach for six testing elements. A standard for microplastics testing is also in progress. The first field-testing working standard addresses the use of autosamplers for the collection of paired influent and effluent flow-weighted composite samples. The development of new laboratory and field specifications and protocols is an ongoing effort with updates to existing standards occurring as the stormwater industry continues to advance MTD technologies and testing methodologies.

ABSTRACT
Biogas generated from anaerobic digestion typically requires gas conditioning before it is used to generate energy. Elevated concentrations of hydrogen sulfide (H2S) in the biogas is often a limitation for downstream processing of biogas. Full-scale tests using micro-aeration technology was undertaken at several water resource recovery facilities and showed that this new process-integrated technology has potential using minimum plant upgrading while contributing to the sustainability and economic efficiency of the energy recovery process of waste sludge digestion at water resource recovery facilities (WRRFs). Keywords: anaerobic digestion, biogas, energy recovery, hydrogen sulfide, micro-aeration.

BACKGROUND
Biogas generated from anaerobic digestion of sludge typically requires gas conditioning before it is used to generate energy. The high concentration of H2S in biogas typically entails a limitation for downstream processing of the biogas as it creates maintenance related corrosion problems in combustion engines, and the release of SOx in ‚ue gases. Traditional physical/chemical end-of-the-pipe technologies (i.e. chemical scrubbing using caustic/hypochlorite or iron oxide-based adsorbents) are relatively expensive and can present relatively high environmental impacts. Biotechnologies (i.e. aerobic or anoxic biotrickling filtration) or physical-chemical combinations with biotechnology (i.e. caustic scrubbing followed by biological oxidation) have recently emerged as cost-effective and more environmentally friendly alternatives. Nevertheless, these biotechnologies are still limited by their high investment costs and their generated byproducts such as sulfuric acid and/or elemental sulfur slurry that need further processing or disposal. Micro-aeration, which involves the dosing of a small amount of air during the digestion process, is a process-integrated biochemical method of removing H2S from the biogas. Micro-aeration has been researched and used in industrial biogas plants, but rarely tested at municipal WRRFs. It has been applied in eastern-Europe in full-scale sludge digesters at WRRFs, with H2S removal efficiency of more than 90% in most cases. Moreover, micro-aeration improved the degradability of COD and volatile suspended solids in all cases. The studies discussed in this presentation are, as far as the authors know, the first full-scale tests in Spain and North-America that try to overcome the lack of full-scale experience with micro-aeration in digesters at WRRFs.

OBJECTIVE
The main objective of this presentation is to share information about micro-aeration and explain how it has potential as an effective digester biogas conditioning technology. The presentation will include research and full-scale testing data and information. These full-scale experiences may provide a stepping-stone for further development and wider implementation.

METHODOLOGY
Micro-aeration technology was tested over a period of several months in different full-scale digesters at different WRRFs. A small amount of air was injected in the sludge recirculation mixing pipe after the pump using fine bubble air injection nozzles or in the headspace of the digesters. The biogas H2S concentrations and sludge characteristics such as pH, alkalinity, total solids, volatile solids were measured daily, while the biogas production and sludge feed were measured continuously.

RESULTS
A comparison between the different types of digesters (i.e. digesters with mechanical mixing and digesters with internal biogas recirculation for mixing) are made to provide better understanding in how micro-aeration can best be applied. An example of the reduction of the H2S concentration in the biogas before and after introducing the micro-aeration process is illustrated in Figure 1. The H2S concentration in the produced biogas dropped by more than 80% from 5,000 ppmv to less than 1,000 ppmv when the micro-aeration was stopped. Directly after stopping the micro-aeration the H2S concentration increased back up to 5,000 ppmv. Figure 1: Reduction of H2S in the biogas during the initial phase 1 of one of micro-aeration tests. The presence of small amounts of oxygen in the anaerobic digestion process in the full-scale test did not significantly impact neither on organic matter removal nor on the biomethane productivity when the amount of air injected is limited. In fact, these full-scale tests (like other bench-scale studies) revealed that, besides efficiently desulfurizing biogas, micro-aeration can potentially improve organic matter degradation during municipal sludge digestion. The volatile solids content dropped in this full-scale test by a few percent from about 66.6% without to about 63.6% with the micro-aeration technology. This drop in volatile solids and a potential more stable digestion process was likely caused by the higher hydrolysis rates and/or alleviation of sulfide toxicity. The potential capital cost savings as well as operational cost savings that micro-aeration technology can provide is substantial. The cost saving on iron sponge media change-out are determined and will be presented. Some of the lessons learned from the full-scale tests include (1) the effectiveness of the air injection method using fine bubble air injection nozzles, (2) the identification of the locations where not to install the nozzles and (3) the quantification of the consequence of overdosing of the injected air amount. Multiple full-scale application of MA in digesters have been reported for different type of digesters (Table 1). The overview shows the different full-scale applications including digester size, organic feed material, biogas production, digester mixing method, biogas production and H2S reduction obtained in the biogas. In general, 80 to over 95% of H2S reduction have been achieved in multiple full-scale applications. Table 1: Example of Full-scale Digester Micro-Aeration Studies and Applications for Biogas Desulfurization.

CONCLUSION
From the full-scale tests and related research, it can be concluded that micro-aeration technology holds great potential for being an effective gas conditioning technology for different types of digesters along with requiring minimal capital investment and operating costs. Micro-aeration would also further contribute to the sustainability and economic efficiency of the energy recovery process during the waste sludge digestion at a WRRF.

The American Society of Civil Engineers (ASCE) published its first manual of practice in 1992 to help the utility industry improve their manhole inventory. Since then, MOP 92 and been updated twice. The most current update is particularly helpful to anyone engaged or involved in manhole inspection, assessment, management, rehabilitation, renewal, or asset management. This particular edition, scheduled to be released as a final published manual, is much more robust and detailed (and helpful) than the prior to editions. This presentation will include an overview of the updates included in this 3rd edition (to be scheduled for release sometime in before March 2023, and highlight the information discussed in the chapters that have been updated. This presentation will also be a helpful one to anyone engaged or involved day-to-day operations, maintenance, and management of manhole structures in the following areas: Non-entry Manhole Inspection, Condition Assessment, Management, Rehabilitation and Renewal, Asset Management. The two prior editions of MOP-92 addressed manhole of the issues associated with inspection, scoring and prioritizing manhole structures. Under this newest edition, there is more emphasis and expansion of the Chapter 5 'Manhole Rehabilitation'. The release of the 3rd Edition will expansion of MOP-992 into nine chapters and they are as follows: 1.Introduction 2.Safety 3.Inspection 4.Quantification of I/I and Structural Condition 5.Manhole Rehabilitation Methods 6.Examining Cost-Effectiveness of Manhole Rehabilitation 7.Wall Thickness Design for Full-Depth Manhole Rehabilitation 8.Quality Management 9.Summary This presentation will go further to discuss specific technologies under Chapter 5 and will include nearly all of those technologies and products that are currently available for both private and public utilities to consider. These include (a) manhole covers and frames, (b) chimney seals, (c) wall joint seals, (d) injection grouting, and (e) coatings and liners. The presentation will wrap up with a presentation of some asset management strategies (and particularly a condition assessment matrix that is featured in MOP-92) along with the impact that these new approaches will be added to the NASSCO codes for both PACP and MACP.

A post-treatment process is required to reduce the volume temperature-phased anaerobic digestate (TPAD), so that it can be more easily transported and disposed of. The digestate liquid fraction contains a lot of nutrients as well and biosolids might contain pathogen. Traditional dewatering process that uses expensive polymers, separates solid and liquid parts to produce condensed biosolids. Polymer conditioning focuses only on volume reduction. TPAD has a high solid content which makes dewatering difficult. Other challenges associated to digestate dewatering such as nutrient and resource recovery, odour control pathogen contamination in biosolids is not addressed in traditional polymer conditioning. It is hypothesised that metal salts as coagulant and oxidants are added along with polymer to enhance the post-treatment of TPAD that would enhance dewatering, nutrient and resource recovery and pathogen elimination in dewatered biosolids. Through the combination of chemicals, the current research seeks to increase TPAD post-treatment efficiency by improving the removal of P in the liquid fraction while producing a Phosphorus (P) rich and pathogen free class A biosolids. To compare the effects of polymer conditioning alone, conditioning with polymer with ferric chloride (FeCl3), polymer, FeCl3 along with hydrogen peroxide (H2O2) before centrifugal dewatering, cationic polymer alone, combined polymer with FeCl3, and cationic polymer with FeCl3, H2O2 in a pH-controlled environment. The best combination of chemicals was 2.5 kg/t DS polymer, 2.1 kg/t dry solids (DS) FeCl3 and 600 mg/l H2O2 at pH 8.0 with the lowest turbidity 11 NTU, specific resistance to filtration (SRF) 0.08 Tm/kg, capillary suction time (CST) 11.5s. The combined chemical dose shows a 94 to 99% improvement in dewatering indices such as CST, turbidity and SRF than raw TPAD. Around 88 to 90% decrease in centrate, TS2- and PN/PS ratio was also observed that contributed to odour causing potential and increased dewatering efficiency. 100 % P removal was achieved with no P in the centrate and P rich biosolids was produced with 40% cake solid content after combined chemical conditioning. However, the fecal coliform level of raw TPAD cake from the full-scale plant exceeds the regulatory limit. The dewatered cake turned into class A biosolids with just 57 MPN/g DS fecal coliform content after combined chemical conditioning in the lab scale study. In comparison with untreated TPAD cake, pathogens were reduced 100%. Combined chemical application reduces polymer dose by 40% as well as associated cost. The novel combined chemical treatment with cationic polymer, FeCl3, and H2O2 at adjusted pH are used to enhance digestate efficiency as well as reduce costs, storage requirements, and address nutrient imbalance, pathogens, and odors that offered more sustainable management. Wastewater treatment plants are thereby recommended to adopt the novel combined chemical conditioning the synergistic chemical combination of polymer, FeCl3 and H2O2, adjusting pH at 8.0 with Ca(OH)2 for TPAD post-treatment while assessing the full scale adaptability through pilot studies.

The California Association of Sewerage Agencies Regulatory Workgroup prepared a guidance document in 2022-23 for wastewater agencies who produce biosolids and contract out land application services. The document is aimed at producers of Class B biosolids and it aims to help agencies oversee their contractors in a manner compliant with 40 C.F.R. § 503, i.e. EPA 503 regulations. The purpose of the document is not to address all the elements of an Environmental Management System, nor is it to substitute the best practice guidance from the National Biosolids Partnership. Rather, this document provides a simple distillation of duties retained by a generator of biosolids when the land application of the biosolids is handled by an outside contractor. EPA 503 regulations promote a spirit of cradle-to-grave involvement in biosolids handling on the part of the generator, yet the regulations leave room for interpretation. This is especially complicated for tasks that have been contractually transferred to the biosolids handler and are beyond the operational control of the generator, yet the generator remains responsible in principle. Further complicating interpretation is that EPA 503 does not clearly list generator duties for land application beyond sampling and analysis, leaving the reader to find duties throughout the full legal code. The document describes how the utilities should provide oversight via desktop review and in the field, before, during, and after land application. Aspects of the contractor's operation that can be reviewed via desktop include field permits, trucking routes, crops to be grown, and timing of application. Also, outreach to landowners and local regulators can be conducted in office. It is important to note that EPA 503 promotes communication between the generator and the landowner to ensure that the landowner is aware of the land application practice occurring on their fields. The document describes how a utility can conduct effective site visits to verify that land application practices are consistent with federal, state, and local (county) regulations. Site visits are also encouraged after application to verify the crop being grown at the site. Perhaps most importantly, the guidance describes agronomic loading rates. It provides definitions, calculations, and guidance related to biosolids analysis, soil analysis, field loading, and crop uptake. The guidance addresses how climate and soil type will affect assumptions. The guidance helps agency staff demystify and interpret field reports from a land applier. Finally, while the guidance document describes the limitations of contracts in abdicating a generator's duties, it nevertheless includes example contractual language to help agencies develop strong agreements. In general, the guidance is meant to help both new and experienced agencies monitor their biosolids land application practices. This talk will step through the guidance document and discuss input and nuances for the various recommendations. This talk will be useful to agency staff persons and biosolids contractors alike, as well as consultants and regulators. While the guidance was developed in California, it is applicable to all states.

The sewer collection system is an important infrastructure that protects the public health by safe disposal of wastewater. Sewer lines are designed for a certain carrying capacity, which is reduced by blockages, resulting in the risk of flooding and the occurrence of Sanitary Sewer Overflows (SSOs) that release raw contaminated sewage. According to the US Environmental Protection Agency, around 25% of the 23,000 to 75,000 SSOs are due to sewer line blockages related to fat, oil, and grease (FOG) deposits. Research studies have been conducted to understand the FOG deposit formation mechanism, sources of chemical constituents involved in FOG deposit formation, and engineering solutions to overcome the FOG-related SSO problems (He et al. 2017). These studies have shown that the long-chain free fatty acids (LCFFAs) from FOG discharge undergo a saponification reaction with calcium ion present in wastewater to form insoluble calcium soap known as FOG deposits that can adhere to sewer line surfaces to reduce its carrying capacity. The primary sources of FOG discharge are the food service establishments and domestic kitchen sinks, whereas sources of calcium can be attributed to the background wastewater as well as concrete structure corrosion. Previous research suggests that calcium released from concrete corrosion may have a more adverse impact on the FOG deposits accumulation on sewer line surfaces (Iasmin et al., 2014). The main contributor of calcium from concrete is the cement used as a binder. Research shows that the substitution of Portland cement by Supplementary Cementitious Materials (SCMs) such as Fly Ash (FA) reduces the calcium leaching potential of concrete exposed to corrosive media (Rozière et al. 2009). In the research discussed in this presentation, we will evaluate the use of FA to replace a large volume of cement to produce an alternative binder material for sewer line construction that reduces the calcium leaching from concrete corrosion, therefore, reducing the FOG deposit formation. We will also explore different factors such as- porosity and pore size, surface roughness, and surface pH of different sewer line construction materials to understand the FOG deposits adhesion mechanism. In our study, two High Volume Fly Ash (HVFA) concrete materials, Concrete-50 and Concrete-75, were produced by keeping the water to cementitious material ratio at 0.42 using 50% and 75% replacement of cement by FA, respectively. Additionally, control samples, Concrete-0, were cast with no FA replacement and used as a standard to study the effect of FA replacement. HVFA samples were tested for compressive strength (ASTM C39-15) and chemical durability (ASTM C267) to check their suitability as sewer line construction materials. Concrete samples were also tested for their calcium leaching potential at pH 5 and 7 by submerging them into Deionized Water (DI) for 90 days. The FOG deposit formation test was performed at pH 7 for a 30 days testing period by submerging concrete samples in synthetic wastewater prepared by mixing oleic acid as the LCFFA source, canola oil, distilled water, and calcium chloride as a background calcium source. The compressive strength test results show that after 90 days of sealed curing, Concrete-50 is well above 4 ksi; a threshold compressive strength used for sewer line construction materials. The chemical durability test results showed that 50% FA replacement enhanced the durability of concrete against corrosive media. After 90 days of leaching under corrosive conditions, Concrete-50 and Concrete-75 samples showed 75% and 86% reduction in calcium leaching, respectively, when compared with the standard Concrete-0 sample. The calcium leaching potential from HVFA samples also revealed that the calcium ion diffusion flux of the HVFA samples was almost similar and lower than the Concrete-0 samples. This observation suggests that FA replacement can reduce the porosity of concrete; thereby, reduce the calcium leaching potential from sewer lines under corrosive media. In addition to the calcium leaching potential, HVFA samples were also tested for heavy metals such as Arsenic (As), Cadmium (Cd), Chromium (Cr), Selenium (Se), Mercury (Hg), and Lead (Pb) leaching potential. After 90 days of leaching test, the cumulative toxic ion concentration for Concrete-50 and Concrete-75 samples did not exceed the pollutant discharge limit provided by USEPA clean water act. FOG deposition formation test results showed that 50% and 75% FA replacement can reduce FOG deposit formation by 55% and 67%, respectively. Therefore, results from this study suggests that a significant decrease in calcium release can be achieved through the use of FA as a cement replacement, which can eventually reduce the FOG deposit formation. To understand the FOG deposits adhesion mechanism on different sewer line surfaces, a combined FOG deposit formation test was conducted by submerging Concrete-0, Concrete-50, Concrete-75, Vitrified Clay Pipe, and PVC pipe into the synthetic wastewater for 30 days of the testing period. This test results revealed a similar FOG deposit formation trend (highest FOG deposition on Concrete-0 samples and lowest FOG deposition on Concrete-75 samples); however, no FOG deposits were found on PVC and Vitrified clay pipes surfaces. Hence, we hypothesize that the FOG deposit adhesion phenomena are primarily controlled by the sewer line material's surface properties in addition to the availability of calcium and LCFFAs. In the next phase of this study, to understand the effect of porosity, pore size, and surface pH on FOG deposit adhesion mechanism, porous ceramic materials with controlled pore size will be used for the FOG deposit formation test. Whereas, to study the effect of surface roughness on FOG deposits adhesion phenomena, HVFA and PVC samples will be prepared at different surface roughness and tested for the FOG deposition test. Results from these tests will be able to identify the key factors that affect the FOG deposits adhesion mechanism. According to Clean Watershed Needs Survey (USEPA, 2016), the total need for replacing sewer lines is $42 billion on top of $25 billion and $18 billion in the new collector and new inceptor sewers, respectively. Therefore, the present study will reduce the future sewer line construction and maintenance cost by reusing FA as an alternative sewer line construction material. Additionally, by studying the FOG deposit adhesion mechanism, this research will provide wastewater collection system utilities with strategies to develop new construction materials or potentially design future coatings that can enhance existing alternative materials to limit or reduce the FOG deposit accumulation on the sewer surface.

An overview of recommended technical design considerations, installation good practices and inspection strategies to help promote successful trenchless structural manhole rehabilitation in wastewater collection systems is presented. This presentation will discuss the various fully structural trenchless rehabilitation systems that are available, what makes these methodologies structural, and when it is recommended to use these different product types. Differences between semi-structural, interactive lining methods such as bonded resin‐based polymer coating/ lining systems including epoxies, polyurethanes, poly-ureas, as well as cementitious materials and geopolymers will be explained and compared with fully structural, independent manhole rehabilitation technologies in a neutral, non-commercial manner. Common problems that can be avoided through proper planning, design, product specification, installation and appropriate quality control procedures will be covered. The importance of performing QA/QC inspections throughout the rehabilitation process and what to look for when performing manhole condition assessment evaluations, with emphasis on implementation of proper surface preparation techniques will be discussed. Design methodologies, product selection, specification development, applicable inspection strategies, and technical standards will be referenced. Structural manhole rehabilitation case studies in Colorado and New Mexico will be introduced and discussed throughout the presentation, with focus on lessons learned for each project.

Summary This paper and presentation will discuss the in-plant operating conditions leading to a late-in-the-design-process dewatering technology selection reevaluation for the Charleston Water System's (CWS) main wastewater treatment facility, the Plum Island Water Pollution Control Plant (PIWPCP). Specifically, the paper will discuss the steps taken to reevaluate the solids dewatering design after 90% design completion by transitioning the selected dewatering technology and making this change while minimizing impacts to the construction schedule already underway. The efficient and timely redesign around a new dewatering technology was achieved by leveraging onsite pilots, solids sampling and off-site assessments, as well as manufacturer presentations to assist CWS in reviewing the preferred technology vendor options. Ultimately, CWS selected centrifuges to replace the originally selected rotary fan press technology to ensure improved dewaterability across a wide range of influent characteristics. Furthermore, the paper will discuss the design challenges associated with accommodating a dewatering technology change while concurrently minimizing impacts to the building footprint and structural design in order to curtail construction sequencing design delays and allowing the Construction Manager At Risk (CMAR) contractor to begin pile driving and sub-surface foundation work as originally scheduled. Background The Plum Island Water Pollution Control Plant (PIWPCP) is the main wastewater treatment facility for Charleston Water System (CWS), providing wastewater treatment for the City of Charleston, Daniel Island, James Island, and several surrounding municipalities. The facility is positioned on a 22-acre island surrounded by salt marsh and discharges to the tidally influenced Charleston Harbor at a rated capacity of 36-MGD. This location causes significant constructability issues due to high ground water from tidal influences and local major rain events coupled with challenging subsurface issues and seismic codes requiring major structures to be built on pile supported foundations. Prior to design, a long-term facility master plan had been completed for the PIWPCP identifying facilities required to accommodate currently permitted flows of 36-MGD with expansion up to an ultimate facility capacity of 54-MGD on both the liquid and solids treatment trains. In accordance with the master plan recommended improvements, new solids handling facilities were included as part of the Phase 4 Capital Improvements Project. These capital improvements included the following new solids handling processes: - New Solids Handling and Dewatering Building with Rotary Fan Press dewatering technology - Three (3) Sludge Storage Tanks with Blending Pumps - Dewatered Cake Storage Sludge Hopper and Loadout Facility The existing dewatering unit process equipment at the facility includes three (3) rotary fan press dewatering units which dewater a blend of undigested primary and secondary solids resulting from the liquid treatment process. Secondary solids are gravity thickened prior to blending with the primary sludge solids immediately upstream of dewatering in a blending tank. CWS had many years of acceptable operating experience (See Figure 1, January 2017 through October 2021) with the existing rotary fan press technology entering the detailed design phase of the upgrade and had thus selected the same technology to utilize in the new dewatering facilities to be constructed during the Phase 4 Capital Improvements Project. The originally proposed Phase 4 Solids Handling Building was designed to hold up to seven (7) 8-channel rotary fan presses with ancillary feed, polymer makeup, and conveyance equipment to meet long-term buildout solids handling needs and accommodate facility expansion up to a 54-MGD ultimate treatment capacity. However, during the later stages of the facility design, CWS identified insurmountable issues with the existing rotary fan press technology used for dewatering (See Figure 1, After October 2021). Steep declines in dewatered cake solids content resulted in increased wet cake mass and volumes for transportation and disposal at a local landfill facility, significantly increasing downstream disposal costs. Concurrently, the local landfill was significantly increasing tipping fees for 'wet waste', further exacerbating solids disposal costs for CWS. In addition to reduced dewatered cake solids content, the rotary fan press solids and hydraulic loading rate performance declined which would require increased numbers of dewatering units to process the anticipated solids loadings under current and future operating conditions. This combination of impacts, decreased dewatered cake solids, increased downstream management costs, and reduced rotary fan press performance, caused CWS to investigate and reconsider the dewatering technology selection and basis of design for the new facility after the rotary fan press design had advanced to the 90% completion level. Upon further investigation, it was determined that influent characteristics at the plant had changed since the initial assessments, causing a detrimental impact on the proposed dewatering equipment performance. Some of the impacts were due to a new influent conveyance tunnel system and collection system behavior between wet and dry periods, new headworks facilities with increased grit removal capability, and new primary and secondary treatment facilities which were included with recently completed capital improvements projects (Phase 2 and Phase 3 projects). Following this initial investigation, CWS approved reconsideration of the dewatering technology selection to include other dewatering technologies (e.g., belt presses, centrifuges). Alternative Technology Selection Immediately following the decision to reconsider the dewatering technology selection, work began to conduct on-site pilot and demonstration testing of belt filter presses and centrifuges. Concurrent demonstration testing was conducted on the same feed sludge for the existing rotary fan presses, a trailer-mounted belt filter press, and a trailer-mounted centrifuge to assess dewatered cake performance and other design parameters for each technology. Table 1 and Figure 2 show the results of the concurrent dewatering technology testing. On-site testing was coupled with off-site and bench scale testing across a range of primary and secondary sludge blends to understand the impact of the primary to secondary sludge (PS/WAS) ratio on anticipated dewatering unit performance to inform operational decision making. Lastly, potential technology suppliers were invited to make presentations to CWS regarding their technology offerings. Ultimately, CWS selected high solids, horizontal decanting centrifuges to replace the rotary fan presses to ensure improved dewaterability across a wide range of influent characteristics and PS/WAS ratios. Following the updated technology selection, the planned dewatering facility had to be redesigned on an accelerated schedule for the new technology while staying within the same building envelope to retain as much of the prior design structural framing and layout as possible to expedite the design and permitting processes. This paper will share some of the design challenges associated with and overcome with the conversion from rotary fan press to centrifuge dewatering technology across the various engineering disciplines (e.g., process mechanical, structural / architectural, and electrical and control systems). Updated design of the new dewatering facility has since been completed with centrifuges (See Figure 3 for a rendering comparison) and construction is currently progressing on the facility.

Green infrastructure and source control technologies are increasingly accepted as a best practice for reducing stormwater impacts on water quality and aquatic habitat in urban areas. However, impacts continue to grow in many watersheds within the United States even as progress is being made on other sources of water pollution (NRC, 2009). Stormwater management practices have been improved at the site level, but they are not being implemented on a large enough scale to offset water quality degradation caused by urban and suburban land use trends (WEF Stormwater Institute, 2015). Philadelphia is one city implementing green infrastructure on a large scale as a key component of its approach to manage urban stormwater and combined sewer overflows. The Philadelphia Water Department will complete its tenth year of program implementation in 2021. This paper will cover the status of the program, provide statistics on the types and locations of green infrastructure that have been implemented, and summarize performance monitoring data collected from systems operating in the field. PWD submitted its Combined Sewer Overflow Long Term Control Plan Update in 2009, as required by its National Pollutant Discharge Elimination System permits. In 2011, a modified version of that plan was approved for implementation through a Consent Order and Agreement (COA) with the Pennsylvania Department of Environmental Protection. The COA specifies combined sewer overflow reductions, pollutant load reductions, and implementation of green stormwater infrastructure targets intended to improve water quality in local watersheds and the Delaware tidal estuary. As the program approaches the ten-year milestone, it has implemented stormwater management features managing surface runoff generated by approximately 1,100 acres of impervious urban surfaces (Figure 1). Stormwater management features have been implemented through a variety of programs and on a variety of land uses (Figure 2). These include projects on private property initiated by code requirements governing redevelopment. Projects have been implemented on public property, including streets, sidewalks, and public facilities. Finally, projects have been implemented through incentives for private property. Post-construction monitoring data from selected sites indicate that systems are generally meeting or exceeding design performance expectations (Figure 3).