Results

Wastewater treatment plants (WWTPs) were considered to be the biggest microplastics (MPs) source in urban environment (Carr, S.A., Liu, J., Tesoro, A.G., 2016.). Most of MPs in wastewater removed and transferred to sewage sludge (Magnusson, K., Noren, F., 2014.), on the other hand, evidence shown that lager plastic pieces might break apart into small pieces due to the physical or chemical factors in environment (Murphy, F., Ewins, C., Carbonnier, F., Quinn, B., 2016.), some of them will become secondary MPs, therefore, sewage sludge plays the most important role in MPs pollution. In this study, a WWTP in western Japan (we call it as WWTP A here) was the research target. Fig. 1 is the diagram of the sewage sludge treatment system of WWTP A, in this research, all 7 kinds of sludge in WWTP A (marked in red numbers) including primary sludge (raw and thickened), waste activated sludge (raw and thickened), mixed thickened sludge, digested sludge and dewatered sludge were sampled, and all non-fiber MPs larger than 100 μm in those sludges were analyzed. The size, plastic type and color of every MPs were recorded, concentration and annual discharge of MPs were calculated. The sampling will be conducted in some seasons and finally MPs flow in WWTP A was built. Since there are no standard analyzing method of MPs, an analyzing method for sewage sludge was examined and established in this research. Firstly, the pretreatment, if the sludge was in solid state, then dissolved it into milli-Q water until the water content was 96%, after that, all sludge was homogenized by ultrasonic (TOMY, 90% power output of 100 W, 80% duty) for 1 hour. Secondly, every gram (in dry weight) of pretreated sludge was digested by 60 mL of 30% H2O2 in 55 „ƒ for two days, the H2O2 was divided into two parts equally and used in the beginning of each day. After digesting, gravity separation using NaI was used to separate MPs from the solid remains. Finally, micro FTIR (Shimadzu, AIM-9000) was used to analyzing the suspicious MPs. In the summer sample of 2022, Fig. 2(a) shows the MPs concentration in different sludges, MPs concentration was 0.83×103 pcs/kg dry sludge in thickened primary sludge, 2.3×103 pcs/kg dry sludge in thickened waste activated sludge, 1.7×103 pcs/kg dry sludge in mixed thickened sludge, 2.7×103 pcs/kg dry sludge in digested sludge and 3.3×103 pcs/kg dry sludge in dewatered sludge. The MPs concentration in thickened waste activated sludge was much higher than thickened primary sludge, this indicates that more MPs were removed in secondary sedimentation tank in this WWTP, the conclusion here is different in other researches, some report that in some WWTPs, the majority of MPs was removed during primary treatment (Carr et al., 2016; Murphy et al., 2016; Talvitie et al., 2015), while another researcher report that the MPs concentration in primary and secondary treatment was basically the same level (Li et al., 2018.), that's may because the specific treatment method and discharge standard is different between WWTPs. In digesting and dewatering process, the MPs concentration raised 60% and 100% comparing to the mixed thickened sludge, there were two possible explains, one is that lager plastics may break apart into smaller ones due to the physical or microbial factors, the other is the loss of total solid cause the increase of the MPs concentration, combining the MPs amount data in Fig. 2(c), the break apart of MPs might be the major factor since the MPs amount also increased substantially in digesting and dewatering process. Table 1 shows the MPs concentration in this and some other researchers, we can see the MPs concentration varies greatly between WWTPs, the WWTP itself, seasonal reason, analyzing method, target MPs size or other detail cause this difference, overall, the MPs concentration in this Japanese WWTP was in the middle-lower level. Comparing between sludge types, it seems the MPs concentration in primary sludge was the lowest and highly related to the target MPs size, the target MPs size was set smaller, the more MPs would be found, this may indicate the widely existence of smaller size MPs in primary sludge. In waste activated sludge, digested sludge and dewatered sludge, the difference of MPs concentration between WWTPs became even lager and hard to find a pattern, thus it is critical to collect more data to provide some reference for governments to make MPs related policies. Fig. 2(b) shows the particle size of the MPs in different sludges, all MPs found in those sample was smaller than 1,000 μm, the percentage of 100-200 μm MPs was decreasing during the sludge treatment process, those MPs might loss with the separate water during thickening and dewatering. The percentage of 300-400 μm MPs increased significantly, this might because the fermenting bacteria or methanogens are somehow able to decompose MPs partially, it may make lager plastics become fragile and break into 300-400 μm MPs. Fig. 2(c) shows the MPs amount different sludges. The MPs amount in thickened primary sludge was 5.0×109 pcs/y, also much lower than thickened waste activated sludge which was 18.4×109 pcs/y, in mixed thickened sludge the amount was 24.0×109 pcs/y, in digested sludge the amount was 18.6×109 pcs/y and in dewatered sludge the amount was 21.9×109 pcs/y. Different to the concentration, the amount of MPs didn't increased during the sludge treatment process, instead, comparing to the mixed thickened sludge the amount decreased about 23% in digesting and increased 10% in dewatering, the decreased MPs may break apart and become smaller than 100μm thus can not be extract in this research, or possibly drain with the separate water during dewatering. In this research, significant number of MPs was detected in the whole sludge treating process in WWTP A in Japan, evidence also shows that sludge treating process was not able to have a proper treatment of MPs. The final fate of MPs must raise our concern, if those MPs were not treated properly, serious environmental pollution may occur in sludge utilization like compost or agriculture use.

Summary--Using a sewer process model to predict extensive collection system parameters related to odor and corrosion, e.g., sulfide and pH, the Albuquerque Bernalillo County Water Utility Authority (WUA) better understands its own system. The WUA has adopted and used the model in-house to address and resolve, quickly, confidently, and with documented, analytical justification, a wide range of operational, design, and planning issues. This model allows chemical feed optimization and assurance that appropriate wastewater is delivered to the Water Resource Recovery Facility (WRRF) to meet performance requirements. The model is complex and a significant undertaking, yet the WUA has been more effective and efficient since its adoption. This paper describes how to integrate these tools into the Utility's operations, including practical issues of structuring staff, growing the team with consultant support, and developing depth of staff. This paper also describes specific studies performed by WUA staff utilizing the model. Introduction The WUA owns and maintains over 2,400 miles of pipes in the collection system to convey approximately 50 MGD wastewater from the service area to the WRRF. The WUA has implemented various methods and technologies for controlling odors and corrosion in the collection system, resulting in significant institutional knowledge and experience in this engineering science. As part of the 2019 Collection System Odor and Corrosion Control Master Plan, Jacobs Engineering (Jacobs) and the WUA implemented a systematic approach to address odor and corrosion issues by developing a sewer process model of the WUA system. The model was created using WUA ArcGIS piping assets, hydraulic data, and wastewater characteristic data. The model used is the Wastewater Aerobic/Anaerobic Transformations in Sewers (WATS). The WATS model simulates sewers' complex chemical, biological, and physical processes through extensive mass balances and differential equations. The WATS software can predict hydrogen sulfide odor generation, concrete asset corrosion, chemical management, analyze wastewater characteristics at inflows to wastewater treatment plants, etc. The WUA's objective in using the model is to respond in real-time to unexpected-immediate, near-term predictable, conceptual design-phase and routine chemical feed considerations. The Collection Section operates and utilizes the model successfully for a wide range of tasks. Methods The framework for developing and running the WATS model in-house is shown in Figure 1. We identified an in-house engineer (Engineer) with strong technical skills but minimal previous experience in sewer odor control and assigned the responsibility of learning and utilizing the model. We provided a learning environment with adequate resources, strong support, and reviews. Technical support was provided by the modeler's direct supervisor and, under a contract established to provide training and related support, the lead process engineer (Consultant) for developing the WATS model of the WUA system. As noted in Figure 1, per typical WUA practice, the Engineer created a Standard Operating Procedure (SOP) that provides specific documentation and procedures for using the WATS model. The Engineer's knowledge is solidified through the process of writing the SOP. It serves as the Engineer's reference document and a training guide for staff assigned to assist or even to learn to operate the WATS model. After the Consultant provided basic training, it was time for the assigned Engineer to learn by performing or 'doing' repeated model use cases. This WUA Learn-by-doing approach is shown in Figure 2. Results Our first use of the model was to develop specific proposed locations, on three interceptors, for ferric chloride and magnesium hydroxide stations proposed by the Master Plan. Specific locations were found based on land availability, truck access, and other criteria. Chemical feeds were simulated with a target of 0.2 mg/L free iron downstream. Reports were developed in-house and provided to WUA Engineering for consultant design of the new facilities. The next use was to develop flow times from each permitted industrial user to the WUA's only significant WRRF. The WUA's WATS network is based on export data from the WUA's InfoSWWM model, including lengths and average velocities. In the typical use of the WATS model, upstream and downstream pipes are connected, establishing the line being evaluated. The model provides the flow time and multiple parameters pertinent to odor and corrosion control. A report was delivered to Pretreatment, providing a total flow time for each user. Pretreatment has used the report data once for a high BOD spill, but there were no obvious spill impacts to the WRRF influent. An ongoing use is managing the WUA's chemical feed program to prevent odors, manage corrosion, and deliver appropriate wastewater to the WRRF. The WUA utilizes six liquid-phase chemicals: ferric chloride, calcium nitrate, calcium hydroxide, magnesium hydroxide, hydrogen peroxide, and residual iron from the surface water treatment plant (SWTP). The WATS model is the tool used to optimize these feeds. In two studies, the model has been used to protect the WRRF. First, a calcium nitrate tank was to be replaced, and the tank had to be quickly emptied. The model indicated the nitrates would be consumed and would not reach the WRRF. Second, a low-pH Fluorosilicic Acid needed to be disposed of at the SWTP. The model indicated the pH impact at the WRRF would be minimal. In both cases, the model matched the actual results and provided confidence for the action taken. Recently, the model network was extended in two locations to study lines in design or under construction. One was a new gravity line subject to very high BOD. The network extended downstream included an existing gravity, a lift station, and a force main. Results indicated H_2 S levels in the gravity lines would be acceptable, but the unexpectedly high force main discharge would be investigated. The other is a proposed lift station and force main discharging to a gravity line unavailable for service connections. Figures 3 and 4 show results indicating the sulfide levels reached minimal levels well before a location where service connections could result in odor issues. We plan to use this 'free treatment' in the gravity line and not include liquid phase odor control but to provide managed airflow in the gravity line and construct corrosion resistance pipes and manholes. The WUA is currently designing a future satellite WRRF. The service area includes a calcium nitrate station that is to be replaced by a ferric chloride station at an upstream location. We are currently utilizing the model to estimate the increase in BOD when calcium nitrate is no longer fed, to optimize the ferric chloride feed and to estimate the resulting decrease in pH and alkalinity. Lessons Learned Modeling proficiency requires regular use. Once the designated Engineer has learned the model basics, the time allocated to the model may average 15% full-time employment. Naturally, some weeks may require nearly full-time efforts. We observed increased task requests as other groups within the WUA became aware of this new in-house capability. The WATS model has proven effective, but the utility investment and commitment must be recognized. The designated Engineer will ideally have a background in process engineering, but many of these subjects can be taught and learned over time. Sustaining depth of staff requires additional employees to be competent in the model. Writing a basic training SOP helps create and maintain the depth of staff. SOPs should be written with new advancements in the model and should be updated regularly. Benefits and Significance A utility benefits from operating a tool such as the WATS model in several ways. First, should anyone understand your system better than the utility itself? We believe a utility should best understand its system due to ownership and continuity. A utility is best served if it is prepared for all eventualities and can respond quickly. The WATS model allows the utility to do so. A utility continuously adds facilities and systems under a consultant-designed contract describing typical responsibilities. This contract structure often cannot direct timely decisions that optimize the utility-operated sewer systems. Finally, the utility benefits in responding quickly and adequately to a wide range of occurrences that all utilities endure.

Introduction At many water resource recovery facilities (WRRFs), when potential environmental impacts are viewed in their totality, thermally processing the sewage sludge remains an environmentally friendly and economically feasible option. Many of these plants have existing, older, multiple hearth furnaces (MHF). Often viewed as having greater emissions than the fluid bed reactors (FBR) which in recent years have gained a greater presence, that is only partially true. Both excess air and afterburner fuel demand can be significantly reduced by conversion of the MHF to a pyrolyzer/gasifier. The paper and presentation will explain how this is possible. History Operation of a MHF in pyrolysis or gasification mode is not a new concept. MHF systems have been used in carbon regeneration and activated carbon manufacturing for decades. Historical applications using MHF systems to process WRRF residuals in these process modes is, however, very rare. On the other hand, FBRs have been more frequently operated in a gasification mode to process WRRF residuals. The first full-scale FBRs operating in a gasification mode were installed at the Hyperion WRRF in Los Angeles. The design capacity of each of the three (3) FBRs was 132.5 dry tons/day of a heat dried biosolids, called sludge derived fuel (SDF). Through heat recovery, superheated steam was produced, then converted to electricity in a condensing steam turbine. The SDF was gasified in the FBR with sub-stoichiometric air addition to produce a syngas. The hot syngas was then combusted in a multi-stage combustion afterburner. The gasification/staged-combustion approach provided significant reduction in nitrous oxide (NOx) emissions compared to conventional incineration. Operation began in 1986 and continued for about 10 years at part load. Problems with the upstream drying process limited throughput to about 100 dry tons/day of SDF. Unfortunately, the continuing problems with the sludge dryers, and a significant decrease in the cost of land disposal, made continued operation no longer economically viable. While Hyperion was a FBR, adaptation of these concepts to a MHF is also feasible. Aside from a MHF being able to produce a synthesis gas with lower particulate than a FBR, a MHF offers another advantage. A safe and stable combustion mode in a MHF can be achieved at a significantly lower exhaust temperature than a FBR, which is because of the reactions that occur in the freeboard that typically create a 200°F(+) increase in exit temperature. The counter-current flow of syngas and sludge feed make an excellent thermodynamic reactor. When operated in a true pyrolysis mode, a biochar would be produced. While production of an agricultural biochar can sometimes generate political currency, it must be balanced against the loss of BTU's that may have to be made up with auxiliary fuel. The use of biochar in a local market will depend on the soil, agricultural needs, and pyrolysis conditions used for producing the biochar. Using the pyrolysis gas from a pyrolysis process is possible but the removal of the tars, oils, and other condensables produced during pyrolysis before sending the pyrolysis gas to a commercial burner have heretofore defied a simple, straightforward, and reliable solution. Any project contemplating on recycling pyrolysis gas directly back to a burner will venture into somewhat uncharted territory. In the early 1980's, the Allegheny County Sanitary Authority (ALCOSAN) installed a dual-mode MHF system at its WRRF in Pittsburgh, PA. This system was designed to process 76.5 dry tons/day of raw sludge, and incorporated both starved-air combustion and conventional excess air combustion modes. When operating in the starved air mode, the furnace was divided into four zones: drying, starved air/gasification, carbon burnout and ash cooling. Burners were fired in the carbon burnout zone, but were rarely needed to any significant degree in the drying zone, as combustion air was introduced to the drying hearths to release a portion of the syngas heat to support the drying process. The carbon burnout zone was operated with excess air to keep temperatures within acceptable limits and yield an ash with less than 2% carbon. The ALCOSAN system sacrificed the production of biochar to provide the heat needed for the gasification process and the drying of the incoming feed. Syngas was combusted in the external afterburner and a waste heat recovery boiler was provided downstream of the afterburner to produce steam for plant and process heating. In the design concept of this paper, bioenergy recovery from the syngas produced in a MHF pyrolysis/gasification system would incorporate an external 'syngas oxidization chamber' equipped with a flame safety pilot burner. This refractory lined vessel is very similar to a separate vessel conventional afterburner commonly installed on MHFs (Figure 1). From the oxidizer, a portion of the heat would be used to heat the Multiple Hearth pyrolysis / gasification reactor and/or to pre-dry the incoming feed. Potential slag formation in the syngas oxidization chamber remains a challenge. This challenge has been meet using indirect heated, rotary kiln pyrolysis reactors. The challenge of slag control and combustion chamber design will be discussed in the paper /presentation. Heat and Material Balances The Heat and Material Balance remains at the heart of any thermodynamic process and the Laws of Thermodynamics: You Can't Beat the Game You Can't Even Break Even This principal remains inviolate and it is essential that any complex design of this nature begin with a thorough heat and material balance at each stage of the process. This enables the engineer to evaluate the interdependencies between each stage; to identify potential problem areas or design challenges; and to fully understand the overall system performance. When a thermal dryer is used ahead of the gasification/pyrolysis, the treatment of the water vapor, thermal or other, must be included in any analysis within the overall Thermodynamic System Boundary. Thermodynamics does not allow a 'free lunch' and the energy requirements for thermal drying are significant. In this basic concept, energy recovery is provided downstream of the external afterburner chamber in the form of hot thermal oil that can be used in an indirect thermal dryer system. This paper will discuss the process in greater detail and through a series of pictorial Heat and Material Balances for both pyrolysis and gasification systems. This will give the reader a better understanding of the process and hopefully prevent repeats of the failures of many previous gasification and pyrolysis ventures. Often these failed to recognize the true thermodynamic balance and the myriad of yet unsolved problems of removing the tars and oils from the pyrolysis gas. Figure 2 illustrates the output from a detailed heat and material balance around a MHF gasifier. Figure 3 shows the distribution of the syngas components from this system. Figures 4 and 5 illustrate the output from detailed heat and material balances around the external afterburner chamber and a subsequent thermal oil heat recovery unit, respectively. Figure 6 provides a summary of the heat and material balances around the entire thermodynamic system boundary. Additional diagrams will be included in the final paper for other optional design concepts. Conclusions The advantages of MHF gasification are readily apparent. The WRRF sludge can just be scalped (thermally dewatered) to 40% and the syngas will have a flame temperature of 1,844°F. Similarly, a 35% solids feed will yield a syngas with a flame temperature of 1,637°F in the secondary combustion chamber. If these flue gases are taken through a thermal oil heater and exhausted at 400°F, the thermal oil will have sufficient heat to dry a raw feed solids of 20% to the feed solids required for the system. Further modeling and evaluation will be included in the final paper to assess the feasibility of MHF pyrolysis. An existing MHF represents a major capital investment and developing means to exploit existing infrastructure and improve performance can have a significant positive impact on both asset management and operational economics at any plant. Converting an existing MHF into a pyrolyzer/gasifier with the addition of a secondary combustion chamber (afterburner) and thermal drying/dewatering system may prove to be a viable option that is worthy of evaluation. With interest growing in the use of gasification and pyrolysis as alternatives to conventional incineration, the options presented in this paper could be attractive in appropriate circumstances and the design approaches described in this paper can be invaluable in assessing the viability of implementing the conversion of an existing MHF to a new pyrolyzer/gasifier system.

Microplastics (MPs) are a kind of pollutants that have attracted widespread attention in recent years. Previous research shows that the vast majority of MPs will be intercepted by sludge after the wastewater enters the wastewater treatment plant (WWTP) 1), and will enter the soil with the subsequent utilization of sludge. Before the sludge enters the soil, it is usually subjected to a series of treatments such as high-temperature composting and methane fermentation. Methane fermentation is an energy conversion of sewage sludge, and its use will expand in the future. Recent study found that the shape, quantity and size of MPs in methane fermentation or high temperature composting of sewage sludge changed 2) but the reason and the MPs' characteristics was not deeply studied. This research study and summarized the characteristics of MPs in the sewage sludge before and after methane fermentation in Japan. We sampled sludge before and after methane fermentation at WWTP A and B in Japan several times in 2022 from June to December. Both WWTP A and B use methane fermentation for sludge treatment. WWTP A uses mesophilic fermentation while WWTP B uses thermophilic fermentation. After organic matter removal using H2O2, ultrasonic treatment, and density separation steps, the sludge sample will be screened for particles suspected to be MP using microscopy and their chemical composition will be determined using μ-FTIR (AIM-9000; Shimadzu.Corp.). This study is focus on non-fibrous MPs with particle size greater than 100 μm. The size (long axis and short axis) and the plastic type of every MPs were recorded, concentration by dry weight and monthly discharge of MPs were calculated. With the above information, the characteristics of MPs before and after methane fermentation of sludge were summarized. In the sludge samples in this research, the concentration of MPs ranged from 0.72×104 to 1.8×104 pcs per kg dry weight. (Figure 1.) Overall, WWTP A had a higher concentration of MPs than WWTP B. The sludge from both WWTPs showed 2.9%-37.1% of decrease in MPs' concentration after methane fermentation. The concentration of MPs in samples from the same WWTP did not show great fluctuations from month to month. If the change in the amount of MPs in the methane fermentation system is calculated from the input and production of sludge, the amount of MPs was reduced by 50.1%-71.1% after the methane fermentation. For the plastic type, PE was found in all of the samples, accounting for 9.1%-21.7%. The detection rates of PP, PP-PE, acrylic and ABS were higher than 75%, PVC, PMMA and EVA were higher than 50%. Some particles with the spectral characteristics of MPs but with an ambiguous spectral information, or with the spectral characteristics of several MPs at the same time were founded. These particles may have been subjected to degradation or may be a mixture of plastics. Although it was not possible to determine the exact type of plastic, these particles were determined to be MPs in this study. The maximum size of MPs observed in this study was 1637.5 µm. 86.5% of the MPs in the sludge were smaller than 500 µm, 8.8% of the MPs were between 500 and 1000 µm, and only 4.7% of the MPs were larger than 1000 µm. (Figure 2.) The particle size of MPs became smaller after methane fermentation in WWTP A. Before digestion, the range of 200-300 µm had the most MPs. After digestion, the range of 100-200 µm had the most MPs. In WWTP B, the range of 200-300 µm had the most MPs but after methane fermentation, the percentage of MPs in this range has decreased significantly. After methane fermentation, there was a decrease in MPs' quantity. The degradation of MPs may have occurred during methane fermentation. Since there is a lower limit of detection of MP size in the analytical and detection methods, the accuracy of analysis decreases near this lower limit, and effective analysis is not possible for MPs smaller than the lower limit of size, 3) the possibility that the decrease in the number and size of MPs was caused by physical effects still cannot be excluded in this study.

1. INTRODUCTION Considering continuous generation of wastewater sludge in vast amounts and beneficial constituents, many countries have been using sludge on land. Nevertheless, land application of insufficiently treated sludge raises concerns due to transferring pathogens and trace pollutants, including toxic organics and microplastics (MPs) into the environment. MPs constitute a large portion of pollutants in sludge because of inseparable and versatile use of plastics in our daily life. Due to their small sizes (<5 mm), MPs can easily transport across environmental compartments and reach WWTPs in great amounts. WWTPs with modern technologies can remove MPs from wastewater with >90% efficiency but concentrate them in sludge. Anaerobic digestion of sludge is a widely used management option that stabilizes the sludge and reduces the amount to be disposed of. Various pretreatment methods have been developed to improve the efficiency of digestion such as thermal hydrolysis process (THP), chemical, and mechanical techniques. Recent studies have revealed that MPs can affect the efficiency of anaerobic digestion process.1 Furthermore, corresponding deteriorative effects of stabilization on MPs have been superficially addressed.2 Despite their stiff nature, exposure to abiotic factors such as heat, light, water, chemicals, and mechanical impacts may initiate structural changes and induce biodeterioration. For example, polyethylene terephthalate (PET), can hydrolyze to a certain degree in the presence of alkaline solutions due to saponification process in ester linkages. In addition, they can hydrolyze in wet conditions at high temperatures as in the case of THP.3 For the first time in literature, this study investigates whether alkaline pretreatment, THP and combined alkaline and thermal hydrolysis pretreatment (ATHP) processes applied for sludge disintegration and biogas enhancement can concurrently deteriorate PET MPs and lead them biodegrade during anaerobic digestion. Moreover, the study investigates the effects of different concentrations of MPs on digestion efficiency. 2.MATERIALS AND METHODS WAS and anaerobically digested sludge (ADS) were taken from a conventional WWTP serving a population of 4 million with a capacity of 765,000 m3/day. The model PET MPs were obtained by cutting water bottles into square shapes using scissors. Then, the particles were passed through a series of sieves to obtain MPs in sizes of 250-500 µm. WAS solubilization efficiency of three different disintegration techniques (i.e., alkaline, THP, and ATHP) were tested in varying conditions by monitoring soluble COD (sCOD) of WAS, which was spiked with 3 mg PET/g TS. Alkaline pretreatment was carried out for 5 days by dosing WAS with 0.5 M alkali using KOH and NaOH at 0.10 and 0.40 M, respectively. THP was performed at 127 °C and 1.7 bar for 30, 60 and 120 min using an autoclave. In ATHP, WAS samples (three sets) which had been alkaline pretreated (0.5 M) for 2, 4 and 5 days were autoclaved at 127 °C for 120 min. PET MPs collected from pretreated WAS were analyzed using SEM and FTIR to observe the changes they experienced during pretreatment. Biochemical methane potential (BMP) reactors of pretreated and unpretreated sludges spiked with 0, 1, 3, 6 mg PET MPs/g TS were set up in triplicates at a food-to-microorganism ratio of 1, and a total solids content of 2%. Reactors were coded as R0, R1, R3 and R6, with the letter P added for disintegrated reactors. All reactors were operated for 60 days under mesophilic conditions. Reactors were monitored for gas production throughout their operation. At reactor termination, digester performance and plastic characteristics were analyzed. 3.RESULTS AND DISCUSSION As shown in Table 1, disintegration degree (DDCOD) reached up to 81% by alkaline pretreatment in 5 days. Considering the most evident increase (71%), two days alkali pretreatment was selected. As the duration of separate THP was prolonged, solubilization increased only slightly and reached to a DDCOD of 19% at a maximum, comparable to literature.4 Although there was no notable difference beyond 30 min, 120 min was selected as the main purpose was exposing MPs to stress conditions before anaerobic digestion. Figure 1 shows that solubilization achieved in two days of alkaline pretreatment was improved with the addition of THP. However, the contribution of THP became relatively small beyond two days of alkaline application. Two days of alkaline application and a subsequent 120 min THP was selected for ATHP, which altogether resulted in DDCOD of 79%. MPs extracted from pretreated sludges were analyzed for changes in physical and chemical structure by evaluating their FTIR spectra and SEM micro-photographs comparatively with control samples. PET exposed to different pretreatment processes experienced varying levels of changes in different regions of the polymer structure, which differentiates the impacts of thermal and chemical stress factors. Both alkaline pretreatment and THP caused an overall decrease in the absorption intensity of PET. Crystallinity of the polymer increased the most with THP and followed by ATHP. Alkali treatment did not cause a significant change. Therefore, heat application might be the mechanism of increasing the crystallinity of ATHP pretreated PET. This is possibly due to the formation of new crystalline zones in polymer's structure from the breakdown of branches in backbone and bending on themselves. Partial melting and the recrystallization of the amorphous region of the polymer can be the reason of increase in crystallinity. It is evident from Figure 3(a) that MPs exposed to alkaline environment experience a strong surface peeling in comparison to untreated samples. Furthermore, THP seems to cause the corners of the square-shaped MPs to expand outward compared to those of untreated MPs. When two techniques were combined, the notable peeling effect caused by alkaline pretreatment diminished to a great extent, possibly due to the heat applied afterwards. The expanded MPs lost the previous changes occurred on their surfaces and reformed, but the cross-sectional layers appeared. As shown in Figure 2, ATHP pretreated reactors produced statistically higher amounts (22.0%) of methane than unpretreated ones regardless of the MPs dose. This can be attributed to that pretreatment process overwhelmed the impact of MPs on digesters. In contrast, the dose of MPs significantly affected the methane yield of unpretreated reactors. Among unpretreated reactor sets, R3 yielded the highest methane production (p<0.05), which was followed by R6, R1 and R0, in decreasing order. Both crystallinity and carbonyl index of MPs showed smaller changes by anaerobic digestion compared to more dramatic effect of sole ATHP. Figure 3(b) shows that there was an observable predominant impact of digestion, giving the MPs a squashed surface appearance and decreased surface thickness at some points. These images supported the current claim that MPs pretreated prior to anaerobic digestion becomes more prone to microbial attack. Acknowledgement: This study was funded by TUBITAK through the project grant 121Y156.

PROBLEM STATEMENT/PURPOSE: Prince William County Service Authority (PWCSA) owns and operates the H.L. Mooney Advanced Water Reclamation Facility (AWRF) in Northern VA. The AWRF is nestled in a residential community with parks and a walking path along the property line. The AWRF first implemented odor control in 2001, and subsequently upgraded the system in 2011 to provide odor control for preliminary treatment and solids thickening processes. To further reduce odors at the AWRF's property line and beyond, PWCSA is completing a design-build project that includes the assessment of odors at the AWRF through sampling and dispersion modeling, evaluation of odor control technologies, and the design and construction of the chosen system. The purpose of this abstract is to present the odor sampling, monitoring, and extensive dispersion modeling that led to the current design (2022) and future construction (2023) of a 95,000 CFM centralized odor control facility at the AWRF.

BACKGROUND:
The AWRF is located in Woodbridge, VA, approximately 30 miles outside Washington, DC and is in close proximity to several livable communities, nature parks, and walking paths. The AWRF is designed to treat 24 million gallons per day (mgd) average daily flow with current flows in the 14 to 16 mgd range. The AWRF has an existing packed tower chemical scrubber odor control system that treats odors from preaeration, screening, grit removal, and gravity thickening processes at the AWRF. Odorous air from solids dewatering and incineration are routed out of a high stack for improved dispersion. However, odor control improvements are needed to reduce odors within the AWRF site and reduce odor excursions into neighboring residential communities and walking paths outside the AWRF property line.

METHODOLOGY:
In the summer of 2021 odor sampling was conducted at various source locations throughout the AWRF to characterize the odors onsite coming from untreated sources and assess the treatment of the existing odor control facility. Odor sampling was completed during summer months to obtain samples under worst-case conditions (warm weather, higher anticipated odors). The sampled untreated process sources included the equalization basins, primary clarifiers, aeration basins, solids processing building odor exhaust (untreated odors routed to the high stack), and the incinerator exhaust stack. In addition to the untreated odor sources, sampling was also completed on the chemical scrubber inlet and outlet to assess the system performance. The odor sampling completed included: -US EPA Surface Emission Isolation Flux Chamber -Grab samples collected for olfactory odor analysis by ASTM E679 -Odor speciation using ASTM D194 -Reduced sulfur compounds using USEPA Method TO-15 (GC/FPD detector) -Field measurement of H2S using Acrulogs and Jerome 631X H2S meters -Ammonia, Amines, and Dissolved Sulfide with Colorimetric Detection Tubes -Temperature and pH Sampling data was evaluated and used to characterize the types and concentrations of odor species present at the AWRF, and to determine the odor emission rates from each odor source for use in the dispersion model.

RESULTS:
The results of the sampling showed the solids processing building exhaust to have the highest dilution to threshold (D/T) value, followed by turbulent zones of the primary clarifiers, anoxic stages of the aerobic basins, and quiescent zones of the primary clarifiers. The chemical scrubber exhaust results showed the system to be effectively reducing odors from the treated sources. The speciation sampling resulted in the detection of four odor compounds including hydrogen sulfide, methyl mercaptan, dimethyl sulfide, and dimethyl disulfide. Ammonia was also detected in samples from the solids processing building. D/T results were used to develop the odor emission rates (OERs) for each odor source. OERs were developed by translating sampled values into odor units per second (OU/sec) based on airflow and odor magnitude. The OERS were used as inputs for the baseline emissions model, also known as the AERMOD dispersion model. Meteorological data for the AERMOD dispersion model was sourced directly from the National Oceanic and Atmospheric Administration archives for representative observation sites. The most recent three years of available data (2018–2020) were used in this analysis and surface data was obtained from the Quantico Marine Corps Airfield, which is 8 miles south of the AWRF. The resultant impacts calculated by AERMOD are expressed in odor units per cubic meter of air (OU/m3) and can be compared directly to the sampled D/T values. Several scenarios of modeling were completed to evaluate existing conditions, identify the most impactful sources of odor dispersion, and assess potential treatment solution results for the sources. The baseline dispersion model, or existing conditions scenario, showed the predicted impacts from the sampled odor sources on site and their impact outside the AWRF fence line. Figure 1 provides the baseline scenario potential impacts. The worst-case D/T concentrations predicted to reach a given area are shown with the color/label. Based on the baseline scenario, the odor source impacts of the AWRF would be noticeable, and potentially a nuisance, for all areas above 7 D/T (shown in yellow in Figure 1). This includes the communities to the north and east of the AWRF, which have maximum odorous impacts of 7 to 10 D/T. The wide impact of the 3 D/T contour extends beyond the frame of this view, which suggests that the AWRF could potentially contribute to ambient odors greater than 1 mile from the fence line. Individual sources were modeled and showed the solids processing building exhaust and the aerobic basin anoxic zones to have the greatest D/T dispersion impact. Before additional treatment options were evaluated, an odor impact criterion, or D/T fence line goal, was developed with PWCSA during several workshops. Virginia odor criteria are plant-specific, and a survey of Virginia plants showed criteria generally range from 5 to 10 D/T with different averaging time requirements. It was determined that the impact goal should be one that minimizes the risk of negatively impacting neighbors but is balanced with controlling increased cost that will be incurred if goals are excessively tight. For PWCSA, the recommended goal of 100 percent compliance with 7 D/T (1-hour impact goal) at the fence line was used for the evaluation of the model. Once the odor impact criterion was determined, six (6) additional modeling scenarios were developed to evaluate the impacts from treating/reducing odors from the untreated sources. The scenarios were as follow: 1.Treatment of solids processing building exhaust (assumed 90% D/T reduction from solids processing) 2.Coverage and treatment of the primary clarifier odors (assumed 95% D/T reduction from solids processing) 3.Combination of 1 and 2 (treatment of solids processing and primary clarifier odors) 4.Combination of 2 and treating EQ basin odors (assumed 50% D/T reduction from EQ basins) 5.Combination of 2 and covering and treating odors from the aerobic basin anoxic zones (90% reduction of odors from anoxic zones) 6. All control alternatives combined The different modeled scenarios showed the greatest odor reduction results for control scenario 6 (all sources treated), followed by control scenario 3 (primary clarifiers and solids processing building treated). Although control scenario 6 reduced the 7 D/T line impact slightly more than control scenario 3, both scenario results show benefit and bring the 7 D/T line close to the fence line. The model predicted dispersion results from scenario 3 are shown in Figure 2. All six of the scenario results will be shown in the presentation.

DISCUSSION/CONCLUSIONS:
The sampling and modeling results were used to identify the primary clarifiers and solids processing building as additional sources for odor control treatment at the AWRF. Once the sources were determined, a capacity assessment was completed on the existing system which showed it did not have sufficient capacity to treat the additional sources. A complete treatment technology evaluation was completed for the AWRF based on the airflows, odor species present, and required treatment for dispersion. Ultimately, the team decided to move forward with a new centralized chemical scrubber facility re-using the existing vessels and a new vessel to meet the design capacity of 95,000 CFM. Chemical scrubbers were chosen based on the sampling results, odorous airflow capacity requirements, and site space constraints. The presentation will provide insight and potential project path solutions for other utilities looking to evaluate the odor impacts from their treatment facilities on neighboring communities, experiencing odor complaints, or wishing to evaluate dispersion modeling uses.

PURPOSE City of Atlanta Department of Watershed Management (DWM), through its Clean Water Atlanta (CWA) Program, is required by the ongoing First Amended Consent Decree (FACD) to develop Remedial Measures Reports (RMRs). RMRs are planning and conceptual design documents providing the basis of design for detailed design and construction plans for capacity relief and sewer structural rehabilitation projects. In parallel, DWM developed Watershed Improvement Plans (WIPs) for major watersheds in the City. The WIPs identified stormwater projects to improve water quality and reduce the volume of stormwater discharged to the city's creeks. Custer Avenue, Clear Creek, and Intrenchment Creek are three of Atlanta's combined sewersheds that collectively are served by more than 707,000 linear feet (134 miles) of combined sewers. To reduce CSOs and minimize urban flood risk, the RMRs identified approximately 164,000 linear feet of sewer requiring either capacity relief or sewer rehabilitation with an estimated capital cost of $201.1 million. The RMR defined projects were collectively referred to as 'gray' infrastructure projects. Concurrently, approximately 1,100 stormwater water quality and control infrastructure projects were identified city-wide, through the WIP process, at a total estimated capital cost of approximately $600 million. Collectively WIP projects were termed 'green' infrastructure projects. Considering the significant capital costs of the identified green and gray projects, DWM requested that the Program Management Services Team (PMST), under the lead of Stantec Consulting Services, undertake a project to answer three simple questions: 1. Would it be possible to integrate green infrastructure with the planned gray infrastructure projects to address combined sewer overflow (CSO) and sewer flooding problems in three combined sewersheds? 2. Would it be possible to reduce the capital cost of current RMR plans without impacting future levels of service? 3. Would solution optimization modeling present an opportunity to increase environmental and community benefits in line with wider DWM 'One Water' objectives? METHODOLOGY To answer the questions all applicable green and gray projects to DWM's existing InfoWorks ICMTM hydraulic and hydrologic models. Green projects that would not directly influence combined sewer flows were omitted. Only green projects, if implemented strategically, that could have a beneficial outcome in reducing CSO activations and reducing urban flood risk were included. PMST and DWM have utilized the hydraulic and hydrologic models for a wide range of engineering planning and design activities for more than 20 years and, as a result, the models are well populated, reliable, detailed, and were able to provide an excellent level of detail to start the optimization. The updated InfoWorks ICMTM models were then imported into a cloud-based optimization software, OptimizerTM. OptimizerTM is a genetic algorithm software designed to solve complex multi-criteria problems faster and more efficiently favoring speed of process over absolute accuracy. For this project OptimizerTM was applied to analyze hundreds of thousands of green and gray project combinations to establish the 'best outcome'. After establishing a baseline plan, OptimizerTM varied the size, scale, and combination of all possible solutions to create new plans for comparison against the baseline using three metrics: capital cost, hydraulic performance, and non-cost benefit. Each metric was applied as detailed: Capital Cost. The incremental capital cost of each project was calculated and entered OptimizerTM as a lookup table. During optimization, as project scales and sizes adjust, so do the costs. For gray projects, the increments related to pipe diameter, pipe depth, storage tank volume, etc. and where applicable, construction technique. For green projects, the increments related to the relative size of the solution based on its ability to capture an amount of rainfall runoff volume using rainfall depth and contributing area. Hydraulic Performance. Hydraulic performance was measured by applying hydraulic penalty scores to threshold exceedances in the model's predicted hydraulic grade line (HGL) and flood volume. Penalties were proportional to the exceedances and applied to to every combination of gray and green projects, OptimizerTM tried to achieve the best hydraulic performance by converging on the lowest total hydraulic penalty score. Co-benefits. Infrastructure value is an important criterion for DWM, this metric was designed to evaluate the value of all gray and green infrastructure to ensure OptimizerTM decisions considered the value of all projects. Co-benefits ensured consideration of social, environmental, and economic indicators were included in determining the best outcome. The principles applied to all projects was consistent with DWM's Triple Bottom Line (TBL) categories across all watershed initiatives. With all project information, including metrics uploaded to OptimizerTM, the optimization process was repeated more than 100,000 times to continually seek convergence, each time attempting to find a 'better' green / gray plan based on the metrics. RESULTS Unlike many models, OptimizerTM creates several potential outcomes and there were many combinations of green and gray plans that offered a broad range of possibilities. Some plans performed hydraulically better, some less expensive, and some realized much greater co-benefits; however, no single plan was deemed to be 'optimal'. Results were presented in the form of a three-dimensional (3-D) Pareto graph from which a subset of potential plans were selected. The dimension axis representing capital cost, hydraulic performance, and co-benefits. The 3-D Pareto graph showing possible plans is depicted in Figure 1. DWM were able to select a preferred plan for each combined sewershed. The selected plans and their relative costs are summarized in Table 1. CONCLUSIONS In conclusion, the Green/Gray Optimization project was able to positively answer all three stated questions. 1. Would it be possible to integrate green infrastructure with the planned gray infrastructure projects to address CSO and sewer flooding problems in three combined sewersheds? Yes, it is possible. The project demonstrated there were effective green alternatives for all three combined sewersheds with WIP projects making up 4% of the total capital cost in Intrenchment Creek, 6% in Clear Creek and 31% of the total capital project cost in Custer Avenue. 2. Would it be possible to reduce the capital cost of current RMR plans without impacting future levels of service? Yes, in all three combined sewersheds, cost estimates were lower. Custer Avenue's selected plan was 39% less expensive; Clear Creek's was 16% less expensive; and Intrenchment Creek's was 52% less expensive. In all cases, the hydraulic performance of the selected plans was better than the original RMR plan. 3. Would solution optimization modeling present an opportunity to increase environmental and community benefits in line with wider DWM 'One Water' objectives? Without question, the inclusion of green projects adds enhanced environmental and community benefits to the overall outcomes for DWM and better aligns with City wide objectives to move to a 'One Water' approach that values all water. Further, these co-benefits are added without compromising sewer system performance.

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.

Autogenous Biochar Production from Municipal Wastewater Biosolids Feedstock at the Ephrata Borough Authority WWTP #1 in Lancaster County, Pennsylvania, USA Lead Authors: Charles Winslow, GHD, charles.winslow@ghd.com Stan Chilson, GHD, stan.chilson@ghd.com Key Words; Pyrolysis, Volatile Organic Compounds (VOC), Biological Contamination, Synthesis Gas, Carbon Fraction, Carbon Dioxide, Greenhouse Gas, Biodryer, Dried Biosolids, Biochar EXECUTIVE SUMMARY The Ephrata Borough Authority (EBA) owns and operates two municipal wastewater treatment plants in Lancaster County, Pennsylvania. The biosolids produced from the 4 MGD WWTP #1 are unstabilized and currently disposed of at local landfills. As a result of rising landfill costs, reduced landfill availability, and concern about future PFAS regulations associated with municipal wastewater biosolids, the Authority engaged GHD to design a new innovative, carbon negative biosolids handling and processing system to produce biochar, a nutrient and carbon rich material with no detectable biological contaminants or PFAS compounds in the final end product, as well as resale value in several markets. This presentation evaluates EBA's decision making process in selecting biodrying coupled with pyrolysis versus other alternatives under consideration. The presentation also includes a summary discussion of pyrolysis fundamentals, including mass and energy balances. THE CHALLENGE One of the challenges many municipalities face is the prospect of doing something new. EBA was confronted with the challenge of upgrading their existing biosolids processing and handling system in the context of uncertain financial and regulatory factors. While they had an outlet for the anaerobically digested, unstabilized biosolids produced at their WWTP #1, they were concerned about this outlet's long-term viability and cost. With an eye on the future and the goal of producing higher quality biosolids and minimizing the amount of material for disposal, they began the process of evaluating their options. Ultimately two upgrade options were selected for final consideration. The first option was conversion of the existing digesters to a two-phase anaerobic digestion (TPAD) system consisting of both thermophilic and mesophilic digesters, which was capable of producing Class A biosolids. The second option was to scrap digestion altogether and to design a new biodrying and pyrolysis system capable of producing Class A biochar. Facing a similar scenario, many in our industry would arguably select the more well-known and established TPAD technology because familiarity breeds a certain comfort level, and our industry is generally risk adverse. THE SOLUTION EBA is a forward-thinking municipality, and they realized that the biodrying and pyrolysis system alternative offers a number of advantages over the two-phase anaerobic digestion option, including lifecycle cost savings and a more favorable construction sequence and schedule; however, if EBA selected this option they would be only the second operating biodrying and pyrolysis facility processing municipal wastewater biosolids in the USA. There are five known biodryer installations operating on wastewater biosolids only feedstock worldwide at the time of this writing. Biodryers are a tried and proven yet relatively new technology that produces Class A biosolids. The biodrying option does not require the addition of any new tanks, thus allowing for repurposing the existing digesters as liquid storage tanks. The biodryer solution also eliminates the need to recycle high strength nutrient loads, as required with TPAD, negating the need for side-stream treatment and mitigating potential impacts on the liquid side of the treatment plant. Coupling a pyrolysis reactor on the back end of the biodryers further reduces the amount of end product by another 60% on a mass basis, and produces a high-quality biochar, which is of such exceptional quality that it is no longer considered a biosolid, and that testing has shown to be devoid of PFAS compounds. More importantly, the inclusion of a pyrolysis reactor allows for the combined system to run autogenously, negating the need for external fuel sources after it is brought to temperature. The Authority was excited about the prospect of bringing this innovative technology to Ephrata, but conventional wisdom would suggest that the TPAD solution was the safer option. However, that being the case, the EBA made the bold move of selecting a new biodrying and pyrolysis process because of the long-term benefits in the face of regulatory uncertainty. PROJECT SUMMARY The project scope consists of new dewatering, biodrying, and pyrolysis equipment housed in a new building, as well as conversion of the existing primary and secondary digesters to aerated and covered sludge storage, including a biofilter for odor control. Construction is anticipated to begin by the end of 2021. At design the new solids handling system will process 8,400 dry lb per day of undigested biosolids through what is best described as a continuous / batch process. Centrifuges will be utilized to process liquid biosolids to produce 22% to 24% total solids (TS) dewatered cake. Dewatered sludge cake is fed to each biodryer drum and, once filled, the biodryer undergoes a batch process lasting 48 to 56 hours. At the conclusion of the biodrying process the material is about 80% dry and classified as a Class A biosolid. The dried material is stored in a hopper, which is used to continuously feed a pyrolysis reactor. The pyrolysis reactor strips the volatile organic compounds from the solid mass and further dries the material to about 95%, producing nutrient- and carbon-rich biochar in the process. The syngas resulting from the pyrolysis reaction is combusted to produce heat energy that is recovered and used to kickstart the biodrying process and maintain the pyrolysis reaction. The new carbon negative biodrying and pyrolysis system will operate autogenously after initial startup and heat up, requiring no external fossil fuel to maintain system temperature and operation. The amount of biochar produced represents a 90% reduction by mass relative to dewatered cake entering the biodryers. Biochar is a marketable product with no detectable PFAS, which Ephrata plans to sell for a small profit at the completion of the project. CONCLUSION The situation facing EBA is one that many municipalities will likely be confronted with in coming years as the disposal of municipal biosolids comes under increasing scrutiny. It is always a challenge to do something new because many municipalities hesitate at the thought of being an early adopter of a relatively new technology. In general, our industry is very risk adverse and, arguably, needs to become risk smart to evolve. The story of EBA and their evaluation and selection of innovative biodrying and pyrolysis technology can serve as a model and an inspiration to others considering a similar journey.

Prevalent biosolids management practices treat wastewater treatment facilities as cost sinks, leaving them to pay ever increasing disposal costs for biosolids. Utilizing hydrothermal carbonization (HTC) to convert wastewater solids and organic wastes into valuable products turns wastewater treatment plants into sustainable, revenue producing assets. Hydrothermal Carbonization, or HTC for short, is the cornerstone technology in SoMax BioEnergy's suite of solutions for organic wastes. SoMax BioEnergy's HTC process is a continuous thermochemical process that utilizes moderate temperatures and pressures of ~350F & 430F (180C & 220C) and less than 580 psi (40 bar). The HTC reaction has variable retention times based on the feedstock from as short as thirty (30) minutes and up to four (4) hours. When considering biosolids processing, HTC's greatest advantage is that the reaction takes place in an aqueous environment, eliminating the expensive process of drying biosolids prior to processing. The HTC process + drying of the BioCoal product, uses less energy than drying the equivalent biosolids alone. In fact, HTC uses the water present in the biosolids as the primary reactant to perform chemical reactions. The key reactions that occur during the HTC process are dehydration, hydrolysis, decarboxylation, and condensation, all of which result in a product with higher C:O ratio than original feedstock. Hydrothermal carbonization of biomass generates a biochar-like solid product, known as hydrochar, and a nutrient rich process water. Comparing hydrochar to the original feedstock, it is more easily dewatered, has greater fuel characteristics, sorption capacity, and has added benefits when used as a soil amendment, such as increased fixed carbon and carbon sequestration potential. Research institutes across the globe are creating value added bioproducts from hydrochar ranging from concrete additives, to battery electrodes and activated carbon. Considering alternative methods of biosolids processing (land application, compost, and anaerobic digestion), HTC is the most carbon efficient, creates the lowest greenhouse gas emissions, and utilizes a much smaller footprint. The hydrothermal carbonization thermochemical process is also more robust as it is not subject to the same sensitivity issues biological processes encounter. The Borough of Phoenixville Wastewater Treatment Plant, in Pennsylvania, has partnered with SoMax BioEnergy to build the first commercial scale hydrothermal carbonization facility in North America. While European and Asian countries already utilize HTC to treat organic wastes including woody biomass, sewage sludge, digestate, food waste, and even municipal solid waste, North America has yet to implement this technology. This changes with the Borough of Phoenixville project, which at the time of writing this abstract, has over $1,000,000 in project funding has come from county and state grants and is under construction with commissioning set for Q1 of 2022. At capacity the Phoenixville HTC project will process ~15,000 tons of prepared 15-20% solids feedstock, generating over 1,500 tons (d.b.) of BioCoal (hydrochar). SoMax BioEnergy and the Borough of Phoenixville are implementing a two-stage approach to maximize the benefits of the HTC facility to align with the Borough's sustainability goals. The first stage of the project is utilizing HTC for treatment of sewage sludge within the plant and surrounding wastewater treatment plants to process biosolids. The second stage will expand the HTC feedstock to include food waste from the Borough and surrounding businesses. Stage two includes introducing gasification technology that utilizes the hydrochar as a solid fuel to power the wastewater treatment plant and put electricity back on the grid. The Borough Council and Management team sees electricity generation from waste they would have paid to dispose of as a win-win situation and steps in the right direction to accomplishing their 2035 goal of 100% clean and renewable energy. The Borough of Phoenixville HTC project, when fully realized will generate over 150% of the electrical demand of the WWTP, covering all electrical and thermal demands of the HTC process, while utilizing the excess electricity for other borough owned properties. Over the 20-year project lifespan, it is expected to generate over $35,000,000 in savings with a capital equipment payback period of around 7 years. In Spring of 2020, SoMax BioEnergy's hydrothermal carbonization solution received recognition from the U.S. Department of Energy as a Phase One winner in the Water Resource Recovery Prize and this fall was 1 of 6 Phase Two submissions. Unfortunately, the Phase two winners are to be announced the second week of November, just missing the deadline of the abstract submittal. In this presentation, SoMax BioEnergy will: 1) Introduce the Hydrothermal Carbonization (HTC) technology 2) Compare HTC to the status quo WWTP technologies 3) Share research developments and HTC product applications 4) Use plant data to discuss the impacts of HTC on effluents and overall mass and energy balances of the plant 5) Talk about DEP permitting and pathways forward for beneficial use 6)Discuss the experience that is commissioning a new technology

NEW Water, the brand of the Green Bay Metropolitan Sewerage District, has completed a program, with initial planning starting in 2008, to replace its biosolids management system at the Green Bay Facility (GBF) in Green Bay, Wisconsin. The facility is permitted to treat 49 MGD of wastewater and process biosolids from the GBF and waste activated solids from their other wastewater facility, the DePere Facility (DPF). The GBF was constructed in 1975 and included a thermal conditioning system (TCS), belt filter press dewatering and two multiple hearth furnaces (MHFs) to process wastewater solids. This process train was chosen because agricultural land application in Wisconsin was deemed not to be practical. Subsequently, the TCS was shut down and in 2008, NEW Water took over operations of the DPF. The almost 40-year-old GBF did not have sufficient treatment capacity into the future and the equipment required replacement due to its age and increasing maintenance costs. In addition, the existing MHFs would not meet the pending federal Clean Air Act Maximum Achievable Control Technology (MACT) air pollution regulations for sewage sludge incinerators (SSIs) that became effective in 2016. Between 2008 and 2011, NEW Water and CH2M (now Jacobs) developed a Solids Management Facility Plan that evaluated numerous solids processing technologies and process trains to respond to these issues. Seventy-three solids unit processes were considered, some were eliminated and the remaining 52 unit processes were used to develop 17 process configurations. Of these 17 configurations, six alternative configurations were selected and evaluated in detail. The Digestion with Thermal Processing and Electrical Generation alternative was selected and later named the Resource Recovery and Electrical Energy Project, or R2E2. The R2E2 process flow configuration, shown in Figure 1, is an integrated solids processing system comprising mesophilic anaerobic digestion (MAD), dewatering and fluidized bed incineration with waste heat recovery (WHR). MAD was chosen as a first processing step to generate biogas for combined heat and power (CHP). High strength liquid organic wastes are co-digested in the MAD process to enhance biogas production and maximize power production and waste heat utilization. Dewatering using centrifuges, followed by fluidized bed incineration was selected as the most efficient method of managing the biosolids, given there is not land within economical distance of Green Bay for agricultural utilization. The fluidized bed reactor (FBR) is equipped with a partial scalping dryer, utilizing waste heat recovered from the FBR and using thermal oil to ensure autothermal combustion. Phosphorus is recovered from the dewatering centrate to produce a fertilizer product. In addition, beneficial uses of the residual ash are being pursued. The CHP, dewatering and FBR equipment trains were purchased and the balance of plant design completed in 2014. Construction commenced in August 2015 and commissioning and performance testing were completed by the end of 2018. Figure 2 shows operating data from the startup of the two digesters through August 2019. The system has been operating since November 2018, as an integrated system. Figure 3 shows a summary of the system energy distribution and usage at the design year of 2035 at annual average wastewater flow conditions. The R2E2 project is expected to generate more than 65% of the GBF projected electrical power requirements in 2035 using biogas only and up to 85% using supplemental natural gas to the full CHP loads. With the system thermal efficiency of about 60% based on heat recovered, the R2E2 project will meet NEW Water's goal of producing electricity in the most efficient way while maintaining autothermal combustion. The paper will discuss the energy recovery and production performance of the facility during the two years of full operation, including the Covid-19 period. Since operation of both digesters commenced, NEW Water has initiated its program of importing high strength organic waste (HSW) and has been increasing quantities to achieve design quantities. Biogas production has increased, with increased electricity production of green energy. The monthly biogas and natural gas electricity production, together with the monthly HSW imported quantities and generator run times in the first year are shown in Table 1. As part of the energy management system, SCADA options allow determining when is the optimum time to operate the CHP and the number of units to operate to reduce demand and other electrical charges. NEW Water continues to optimize energy production with waste heat recovery and matching plant heating requirements. The presentation will be of interest to municipal plant operators, wastewater utility managers, planners and design engineers who are considering integrated biosolids processing systems to maximize energy recovery and provide resource recovery opportunities.

Summary The pandemic hit Englewood at a time of dynamic change. Under new leadership, the City's Utility Department was in the midst of developing innovative solutions to address the aging water and wastewater infrastructure while maintaining customer affordability. Transformational change was necessary to establish a new baseline for level of service, and nothing was left untouched from the planning philosophy, prioritization of capital projects, financing alternatives and major adjustments to utility billing. Even the communication to City Council and the Water and Sewer Board was adapted to garner support for the City's new approach from the governing bodies and ultimately from customers. A series of informational presentations were made to City Council following the development of the master plans, and coupled with the financial evaluation, the case was made towards a defendable adjustment of rates and fees with a plan to invest over $140 million in the systems over the next five years. Addressing capital needs, taking advantage for new types of funding, implementing major changes to billing structure and procedures, and evaluating the impacts on customers, all hinge on a utility's ability to analyze the past and develop meaningful projections of the future. Englewood was able to accomplish its objectives in spite of the disruption introduced by the pandemic, and the results may be instructive to utility managers coping with similar disruptions in the future. Abstract The City of Englewood, Colorado serves about 11,000 water service connections and over 40,000 sewer service connections in areas just south of Denver. The City's water and sewer utilities survived for many years with little to no rate adjustments, but with significant capital investment needs uncovered by the City's master planning process, the City engaged in a financial planning and rate study process to meet its long-term financial obligations. The master plans resulted in a Capital Improvement Plan for the water and sewer systems that programmatically addresses the City's largest vulnerabilities. Prioritization of capital investment and optimizing operational strategies of the existing systems were important steps to develop a feasible and affordable plan. The City implemented a long-term financial plan incorporating debt and cash funding opportunities supported by modest, annual rate increases to maximize the Utility's financing capacity. The financial planning and rate studies (yes, multiple rate studies) included evaluation and implementation of a new water rate structure, tapping into all available financing tools, and transitioning from quarterly billing to monthly billing for many customers. This presentation will introduce each area of innovation the City considered in its financial overhaul. The master plan 'wish list' and the process City staff used to narrow down key desirable projects, such as lead service line replacements and water taste and odor improvements, will be described. The dynamic financial planning process will demonstrate how master planning and financial planning go hand-in-hand, especially in a time of disruption in customer demands. Further, financing decisions and the detailed process of applying for a WIFIA loan, will be described with a focus on data needs and on the management implications to the utility. Key decision points and lessons learned will be discussed and offered. Technical Content Through the use of dynamic financial tools, impacts of master plans, funding decisions including use of a Water Infrastructure Finance and Innovation Act (WIFIA) loan, converting flat rate water customers to volumetric billing, implementing a new billing system, and changing base billing practices from quarterly to a monthly schedule and customer bill impacts were evaluated. The City's consultants worked closely with City staff to customize financial forecast that minimized impacts on customers' bills. The Water and Sewer Board reviewed each step of the process prior to City Council consideration and acceptance. Project Status The Master Plans were developed in 2019 for the Water Fund and Sewer Fund, as well as for South Platte Renew, the water resource recovery facility co-owned with the City of Littleton and the third largest wastewater treatment facility in Colorado. Rate studies for South Platte Renew and the City's water and sewer funds were completed in 2020. The water rate structure was materially modified with a new monthly Capital Improvement Fee and increases to the variable charges. Moving into year three of implementing this change, budgets and rate increases for 2022 will be implemented, the WIFIA loan is expected to be closed in early 2022 and major components to the capital investment will be underway at the time of this presentation. Benefits and Significance Not every utility has access or the means to completely evaluate its financial sustainability. The City of Englewood proves a small to medium-sized system can thoughtfully change its approach to planning, structuring, and recovering costs. Further, the project demonstrates the ability of a focused process to achieve substantial change in the face of operational disruptions and uncertainty regarding changes in usage patterns. Finally, it demonstrates the ability of a project team to increase financial resilience while successfully maintaining a focus on affordability implications. Additional Co-Authors: Roger Austin, Vice President, Hazen and Sawyer Carol Malesky, Principal, Stantec Consulting Services Inc. Siyuan Rao, Senior Consultant, Stantec Consulting Services Inc.