Introduction A commercial-scale short-term demonstration of biosolids pyrolysis will be conducted at the Synagro Drying Facility at the City of Baltimore Back River WWTP i, Maryland. The pyrolysis process is designed and supplied by CHAR Technologies, of Toronto, CA. This project aligns with current environmental priorities, particularly the need for PFAS (per- and polyfluoroalkyl substances) mitigation in waste streams. The proposed objectives for this temporary pyrolysis demonstration unit will be: a. Verify the PFAS (synthetic, per- and polyfluoroalkyl substances) characteristics of the biosolids, the Syngas and the Biochar confirming the anticipated PFAS destruction in the pyrolysis process. b. Demonstrate the viability of converting biosolids pellets into valuable by-products: syngas for potential energy recovery and biochar for agricultural or environmental applications.. c. Verify the performance of the pyrolysis process on biosolids continuously for at least six months. d. Verify the resultant Syngas characteristics, and the opportunities and requirements for reusing within the dryer system or upgrading to renewable energy. e. Verify the resultant Biochar characteristics, and suitability for its use as a soil amendment. This six-month demonstration, scheduled from January 2025 to July 2025, aims to provide valuable insights into the operational sustainability and environmental benefits of pyrolysis in biosolids management. Process Description The Pyrolysis Demonstration Unit from Char Technologies uses a pyrolysis process to thermally decompose biosolids pellets in the absence of oxygen; the absence of oxygen prevents incineration from occurring. This pyrolysis process occurs within a rotary kiln chamber with an external burner that after starting-up with propane, burns the Syngas generated during the pyrolysis process. The Char Technologies pyrolysis demonstration unit will process over 8 tons per day of dried biosolids pellets and is projected to produce approximately 143 standard cubic feet per minute of high heating value Syngas containing dust, steam, hydrogen, carbon monoxide, carbon dioxide and methane. The Pyrolysis Demonstration Unit includes Syngas scrubbers that convert the Syngas for internal use in the pyrolysis unit. The excess Syngas that is not used in the pyrolysis process will be combusted, in a thermal oxidizer unit before being discharged at the Demonstration Unit Stack. An isometric of the facility being constructed is presented in Figure 1. A photo of the pyrolysis kiln is provided in Figure 2. A process flow diagram is presented in Figure 3. Sampling and Analytical Methodology Comprehensive sampling and analysis will be performed throughout the six-month demonstration period, with multiple data points collected from key stages of the process. These sampling points are presented in red in Figure 3. Parameters measured include: - Feedstock and Biochar: Elemental and proximate analysis, metals, nutrients, PFAS - Wastewater Analysis: BOD/COD, nutrients, pH - Raw pyrogas, clean syngas, and exhaust gas analysis: hydrocarbons and VOCs, particulates and metals, acid gas, NOx and Sox, PFAS US EPA Method 1633 will be followed to test for all PFAS compounds. Sampling will be conducted at regular intervals to capture variability in process performance. Quality assurance measures, including duplicate and blank samples, will be implemented for data validation. The test methods used for analysis are outlined in Table 1. Results and Discussion We expect to have interim analytical results available by April 2025 for presentation at RBC. Primary discussion will include fate and transformation of PFAS compounds, but will also discuss biochar characteristics, syngas quality and lessons learned in operating and maintaining the pyrolysis unit.

Introduction Greenhouse gas (GHG) emissions, primarily comprising carbon dioxide (CO2), methane (CH), and nitrous oxide (N2O), are a major contributor to climate change, driving global warming and environmental instability (Gautam et al., 2021). These gases originate from various human activities, including energy production, transportation, agriculture, oil and gas industry, wastewater treatment, and waste management (Varon et al., 2021). Among these sources, methane is particularly potent, having a global warming potential significantly higher than CO2 over a 20-year period. This makes methane emissions a critical target for mitigation efforts, as reducing them can have an immediate impact on curbing climate change and its negative influence on the environment (Liu et al., 2019). Wastewater treatment plants (WWTPs) are considered an active source of GHG emissions, especially methane, which is generated during the biological processes that involve breaking down the organic matter during the anaerobic digestion processes (Khalil et al., 2024). There are multiple key emission hotspots within WWTPs including the sludge treatment areas, anaerobic digesters, and equalizer tanks, where anaerobic conditions can lead to significant methane release. In addition, there might be additional unexpected sources of GHG emissions that may contribute to the overall emissions from these WWTPs such as aeration tanks. As these emissions can be episodic and location-specific, continuous monitoring is essential for capturing real-time data on emission patterns and variabilities. Despite its significance, a major limitation in the wastewater sector is developing an affordable and continuous methane monitoring systems. Therefore, the use of advanced sensing technologies, such as ground and drone-mounted sensors, has been gaining greater attention during recent years. These technologies enable more precise and continuous monitoring, allowing for effective detection of fugitive methane emissions and identification of the hotspots that might otherwise go unnoticed. Continuous monitoring not only provides critical insights into emission dynamics but also supports timely interventions, helping to reduce the carbon footprint of WWTPs and contribute to broader climate goals. Objectives The main objectives of the current study are to: (1) install a group of ground sensors to isolate the methane emissions from different wastewater treatment processes; (2) identify the hotspots of methane emissions within the wastewater treatment facility based on continuous timeseries of fugitive methane emissions from different sources; and (3) compare the methane emissions from the ground sensors with other sensing technologies such as drone-based techniques. Methods and Materials In the current study, 16 ground sensors were installed in a local wastewater treatment facility (WWTF) in Ontario, Canada. The WWTF comprises the typical treatment processes including the primary and secondary treatment, anaerobic digesters, and solids management facilities. In addition, this WWTF receives high organic loading rates which can contribute to the fugitive methane emissions. The ground sensors were distributed around the treatment processes and building to continuously monitor the fugitive methane from these processes. For example, four ground sensors were installed around the aeration tanks to continuously monitor the methane concentrations and emissions from the basins. It should be noted that the observation period started in June 2024 where the ground sensors observed the methane concentrations on a 15-minute interval. Besides the ground sensors, a drone and Optical Gas Imaging (OGI) sensing campaigns were carried out in the WWTF in Summer 2024 to compare the methane concentrations and emissions from different monitoring levels including the ground and aerial sensing techniques. Results According to the preliminary insights from the time-series of methane concentrations using the ground sensors, it was observed that there are multiple hotspots for methane emissions within the WWTF. The average methane concentration at each ground sensor varied according to the location of sensor, the isolated process, and wind properties that play a crucial role in conveying the methane plume. For example, the average methane concentration over four months (i.e., from beginning of June until the end of September) ranged between 7.2 to 11.4 ppm for the sensors surrounding the aeration tanks (Fig. 1), indicating that these basins are a potential source of methane emissions. In addition, the average methane concentration was approximately 10.3 ppm near the primary clarifiers (Fig. 2a). Moreover, the range of the average methane concentration of the sensors installed around the sludge treatment facilities was 5.7 -- 11.2 ppm. Based on these observations, it can be emphasized that most of the treatment processes are considered hotspots for fugitive methane emissions with the WWTF. These findings were validated using the drone and OGI sensing approaches where the drone flights and OGI camera confirmed the locations of the hotspots for emitting methane within the treatment processes (Fig. 2). Conclusions and summary The deployment of ground-based sensors for the quantification and detection of fugitive methane emissions at the WWTF provided valuable insights into the spatial and temporal distribution of emissions. The sensors, strategically placed near the expected and unexpected emitters such as sludge handling units, anaerobic digesters, and aeration tanks, captured real-time data on methane concentrations, enabling the identification of persistent emission sources. Over the monitoring period, fluctuations in emission levels were observed that were linked to the operational activities and environmental conditions. This data underscored the variability of methane emissions and emphasized the importance of continuous monitoring to capture short-term spikes and long-term trends. Ultimately, the ground sensor campaign highlighted the potential for such technology to complement aerial sensing, providing granular, location-specific data critical for effective emission mitigation strategies in wastewater treatment operations.

Pyrolysis and gasification are experiencing a renewed interest within the wastewater industry as a method to process either the biosolids or the residuals. The reasons are a) mounting evidence that per and polyfluoroalkyl substances (PFAS) are removed from the resulting biochar, b) the volume of the final material may be reduced by 90%, c) the systems (in the US) are often easier to permit than incinerators and d) they allow for sequestration of carbon within the biochar thus reducing carbon footprint. In addition to removing PFAS from the biochar, removal of microplastics and pharmaceuticals has been demonstrated (Keller et al. 2024 and Liu et al. 2023). These reasons make a compelling case for thoroughly vetting these technologies for application in wastewater industry. In Germany, a number (6 -- 8) pyrolysis units have been operating on 100% biosolids for several years and have experienced difficulties due to siloxanes in the producer gas. In the United States two pyrolysis systems and one gasification system are operating and several others have been designed and are expected to be constructed or commissioned in 2025. However, there is limited information regarding the operational requirements and challenges of these technologies operating on a feedstock of 100% wastewater biosolids or residuals. Although these technologies are well established in other industries and their applications documented by a plethora of information when operating on feedstocks such as woody or herbaceous biomass and coal; there is limited information regarding operating on a feedstock of 100% sewage sludge biomass (SSB). The primary challenge of SSB is the a) high moisture content, b) relatively low heating value and c) presence of siloxanes. The focus of this presentation is the presence of siloxanes, which manifest in the producer gas, and plug the thermal oxidizer resulting in the system being offline as much as 30 -- 40% of the time. The presence of siloxanes in wastewater is well known. In one study measuring 17 siloxane compounds, the average influent loading of siloxanes was 15.1 kg/day (Bletsou et al., 2013). In another study, in which three siloxanes were measured, their presence constituted 39 mg/L of the total influent COD (Surita & Tensel, 2014). In addition, the fate of siloxanes in wastewater has been studied especially in relation to its presence in digester gas. However, the siloxanes remaining in the sludge after digestion create different challenges when the residuals are processed in thermochemical processes such as pyrolysis or gasification. Siloxanes are manmade organosilicon compounds consisting of an Si-O backbone with a methyl, ethyl, or other organic functional group. They exist either as linear chains, designated with an L or as cyclic rings, designated with a D (Dewil et al. 2006 and Appels et al. 2008). Two main classes of widely used siloxanes that enter wastewater treatment plants are polydimethylsiloxanes (PDMS) which are non-volatile and volatile methylsiloxanes (VMS) which are volatile organic compounds (VOCs) (Xu 1999 and Traina et al. 2002). Most (greater than 90%) of the PDMS are adsorbed to the extracellular polymeric substances (EPS) of the floc. Approximately, 50% of the VMS are either volatilized or air stripped in the aeration basin (Parker et al. 1999, Xu 1999 and Traina et al. 2002). The sludge sent to anaerobic digestion; therefore, contains almost all the PDMS and 50% of the VMS. During digestion much of the PDMS is hydrolyzed to smaller VMS compounds, some of which are removed with the digester gas. The remaining VMS and approximately 34% of total PDMS entering the plant, remain in the digested biosolids (Xu 1999, Parker et al. 1999, Traina et al. 2002 and Accettola et al. 2008). These remaining siloxanes, when sent to a thermochemical process such as pyrolysis or gasification manifest as a problem within the thermal oxidizer. The siloxanes remaining in the sewage sludge will volatize in the thermochemical process and exit with the producer gas. The problem manifests downstream, in the thermal oxidizer, which typically operates at 1,100 -- 1,200˚C. At these temperatures, siloxanes precipitate to silicon dioxide (SiO2) i.e., silica. The oxidative decomposition of siloxanes may begin at temperatures from 600 -- 850˚C depending on the local environment; with nearly complete oxidation occurring at temperatures ≥ 900˚C. The combustion equations for three common cyclic siloxanes are shown below (Tansel & Surita 2014): D3: C6Si3H18O3 + 12O2 → 3SiO2 + 6CO2 + 9H2O D4: C8Si4H24O4 + 16O4 → 4SiO2 + 8CO2 + 12H2O D5: C10Si5H30O5 + 20O5 → 5SiO2 + 10CO2 + 15H2O The equations indicate a) the production of SiO2, and b) the relatively high consumption of oxygen required. The latter may result in insufficient oxygen for the combustion of the gaseous fuels within the thermal oxidizer. Silica exists as either an amorphous or a crystalline (i.e., quartz, tridymite and cristobalite) structure. In the combustion of woody biomass amorphous silica may transform to cristobalite at 800˚C and cristobalite to tridymite at 1,000˚C (Yang et al.,2022). Therefore, the silica that forms in the thermal oxidizer maybe of multiple forms all of which pose a significant operational problem. The evaluation of several systems indicated the quantity of silica generated ranged from 3.25 -- 13.5 kg/day. See Figures 1 and 2. The result was that every 5 -- 7 days the systems had to be shutdown to remove the material. To do so required 1 day for cool down, ½ - 1 day for cleaning and 1 day for warmup/startup (i.e. 2½ to 3 days) or 30 -- 40% downtime. Typically scrubbing siloxanes from digester gas is accomplished in an adsorption process using granular activated carbon (GAC). However, this is not an option with producer gas because the high concentration of other energy rich VOCs that would be removed instead of combusted in the thermal oxidizer to provide the heat for the drying process. Removal of the siloxanes from the producer gas must be selective. An alternative, to removing them from the producer gas before precipitation is a thermal oxidizer designed around the precipitation of the silica, but without requiring shutdowns. Such a thermal oxidizer exists and is designed to effectively cause the siloxanes to precipitate to silica and automatically remove the material from the process. The system, shown in Figures 2 and 3, is a dual-chamber regenerative thermal oxidizer (RTO), utilizing a regenerative ceramic material that is automatically circulated and cleaned. The technology has been operating full scale at two facilities since 2012 and 2022 and will be piloted as part of a Department of Energy grant evaluating autothermal pyrolysis. Figure 5 shows the silica removed from the gas stream. Its use in the removal of siloxanes for the producer gas is a new and innovative approach to a recent problem arising from the combustion of producer gas generated from the pyrolysis or gasification of sewage sludge. This presentation will discuss the following: a) the forms of siloxanes in the wastewater and the operational problems resulting from their presence, b) a potential solution, using a technology already operating in industrial applications and c) the challenges in applying this technology to the removal of siloxanes in the producer gas.

Operating pyrolysis in an autothermal mode is a means overcoming heat transfer barriers while simultaneously intensifying the pyrolysis process resulting in an exponential increase in throughput for a given size reactor. Therefore, the proposed 2 dry-ton/day autothermal pyrolysis system, which will be built and operated at a large municipal facility as part of a U.S. Department of Energy Grant is a significant step forward in the development of a pyrolysis technology suitable for application at any large wastewater treatment facility. Several alternative modes of operation for pyrolysis are depicted in Figure 1. Currently available pyrolysis technologies operate conventionally, in the absence of an oxidant (i.e. air/oxygen) and are therefore, allothermal, meaning that the thermal energy required is external to the process as depicted in Figure 2. Since the reactions of pyrolysis are endothermic, the absence of an oxidant requires that the energy demand be met by the transfer of external thermal energy (i.e. heat transfer) via either the reactor surface (auger reactor) or the media (fluidized bed reactor). However, providing this thermal energy at typical pyrolysis temperatures of approximately 930ËšF (500ËšC) can be challenging, especially as the reactor becomes large. Hot gases can be employed for this purpose using tubular heat exchangers, but the low specific heat of gases requires large volumetric flows to meet the thermal energy requirement. Granular media is more suitable for direct heating due to their refractory properties and high heat capacity. However, both heat carriers require ancillary equipment to heat and circulate them. As the reactor becomes larger the energy required for pyrolysis, which is a function of reactor volume, increases faster than the surface area for heat transfer, which makes heat transfer rate limiting in allothermal pyrolyzers (Brown, 2021). Under these conditions, assuming a fixed diameter to length ratio, the reactor size scales to the square of the diameter, while the cost increases linearly with no economy of scale. For these reasons, currently available pyrolyzers, for the treatment of SSB are restricted to relatively small quantities of sludge and therefore small wastewater treatment plants. Allothermal pyrolysis is neither economically nor logistically feasible to scale to large applications. However, autothermal pyrolysis is. Autothermal pyrolysis refers to the special case of oxidative pyrolysis in which just enough oxidant (air) is introduced to oxidize enough of the products to provide the energy for pyrolysis within the reactor as depicted in Figure 3. The amount of energy required to provide the energy for pyrolysis is a function of the feedstock and may be relatively small (7 - 10% of the energy content of the feedstock) (Daugaard and Brown, 2003. The exothermic reactions of the oxidation of these products meets the energy demand of the endothermic reactions and the parasitic load of maintaining reactor temperature. The chemical reactions control the process and the capacity of the reactor scales as the cube of the reactor diameter. Therefore, autothermal pyrolysis would provide a several fold increase in capacity over conventional pyrolysis in the same size reactor. The difference between the two operating modes is demonstrated with the following experimental results operating on red oak biomass (Pollin et al. 2019). Operating in allothermal (conventional) mode, the pyrolyzer throughput was 253 lb/day (4.78 kg/hr). For autothermal operation, 11.4% of the stoichiometric oxygen requirement was introduced. The result was an increase in throughput to 814 lb/day (15.4 kg/hr), or a 3.2-fold increase. Figure 4 shows the effect on throughout as the reactor diameter increases. Autothermal pyrolysis increases the throughput of a given reactor by the cube of the diameter (D3). Although there was a shift in the constituent products, the specific energy yield remained constant which indicates that the energy available for drying remains the same for either mode of operation. The second significant advantage of autothermal pyrolysis is that it provides a reduction in scale reducing capital costs, whereas allothermal pyrolysis depends on economies of scale. For autothermal pyrolysis capital costs of the reactor are a fraction of allothermal pyolyzers at the same throughput as seen in Figure 5. Although autothermal pyrolysis is currently being demonstrated at Iowa State University at scales up to 50 dry-tons/day using feedstocks such as corn stover and red oak; the 2 dry-ton/day pilot to be operated at one of the Philadelphia Water Department (PWD) wastewater treatment plants will be the first system to operate on 100% sewage biosolids. Proximate, and ultimate analyses of the dried (<10% moisture) sewage sludge, is shown in Tables 1 & 2. The proximate analysis indicates total percentage greater than 100%. This is being investigate and one theory is that precipitation of siloxanes in the sludge to silica maybe a contributing factor. The enthalpy for pyrolysis will also be determined ahead of the research so that an accurate energy balance can be performed and included in this presentation.

INTRODUCTION/BACKGROUND Land application of biosolids provides benefits via recycling nutrients and carbon to soil. However, Per- and polyfluoroalkyl substances (PFAS) are becoming a main hindrance to land application of biosolids with increasingly stringent regulations (McNamara, 2023). PFAS are found ubiquitously in many industrial and consumer products due to their unique chemical properties. These same properties also make them highly persistent and potentially toxic to ecosystems and humans (Holmquist, 2020). New restrictions around land application coupled with a reduction in potential landfill sites for biosolids has led many WRRFs to investigate thermal processes for biosolids management (Winchell, 2022). Incineration provides the benefit of reducing residual solids loads to be managed. Pyrolysis and gasification are emerging thermal process alternatives that also reduce residual solids loads. Moreover, these two processes offer benefits of lower concerns for exhaust gas emissions and the ability to sequester carbon in the solid residuals (Winchell, 2022). Of particular interest now to WRRFs is that these thermal processes can remove and/or transform PFAS (Winchell, 2022; McNamara, 2023). While PFAS are part of the biosolids management decision tree, they are not the only important thing. Any process implemented today still needs to make sense in two decades even if PFAS are no longer a primary concern. Additionally, the relative importance of PFAS in light of other critical environmental concerns like global warming and eutrophication have not been widely studied. While facing a seemingly pivotal moment in biosolids management history, it is critical to understand management options and the relative importance of PFAS. For this research we combined PFAS fate data from our own experiments and from literature through thermal processes. These results were then included in the LCA as their own impact category and as an input to toxicity. To the knowledge of the authors, this is the first LCA on solids handling alternatives to date that has incorporated PFAS toxicity in this way and compared impacts to conventional LCA components. In short, LCA was used to compare thermal drying, incineration, pyrolysis, and gasification holistically with regards to their impacts on humans and the environment. APPROACH PFAS Fate Through Thermal Processes Lab-scale pyrolysis and gasification experiments were conducted as part of WRF Project 5211. Targeted analysis of PFAS was completed by Eurofins on influent biosolids and effluent solids (char), liquid (py-liquid), and gas (py-gas or gasification gas). These data were used to assess removal and release of PFAS in the effluent phases. Incineration data from Winchell, 2023 was used for incineration PFAS removal performance as a reference scenario. LCA Structure 1)Five biosolids treatment scenarios for a 'typical' WRRF were compared, distinguishing between different thermal processes: thermal drying only, pyrolysis at low (500 degrees C) and high temperature (800 degrees C), gasification, and incineration. See Table 1 for a description of each scenario's treatment train. 2)Mass and energy balances across the treatment trains for each scenario were conducted, as well as a global warming potential (GWP) evaluation, using the BEAM*2022 tool (NEBRA et al., 2022). 3)PFAS emissions were first characterized alone in an impact category called 'PFAS potential,' representing total mass of PFAS emitted in each scenario as fluoride equivalents. 4)PFAS emissions were then also characterized within the toxicity impact category using the modified USEtox PFAS framework from Holmquist et. al. 2020. 5)These results were than used as an input to the LCA to compare the five thermal process scenarios with five main impact categories: i) GWP, ii) eutrophication potential, iii) freshwater ecotoxicity potential, iv) human cancerous and noncancerous toxicity potential, v) and PFAS potential. RESULTS/DISCUSSION Global Warming Comparison The incineration scenario had the highest GWP, driven mainly by scope 1 emissions (Figure 1). The scenarios with a fertilizer offset credit applied had negative scope 3 emissions. This was particularly significant for thermal drying only, because the biosolids had the highest nitrogen content, which largely drove the GWP fertilizer credit. The pyrolysis scenarios were determined to have the lowest GWPs, largely driven by lower scope 1 emissions through carbon sequestration credits achieved by the stability of the biochar product. Eutrophication Comparison The thermal drying only scenario had the highest eutrophication impact, driven by the increased hauling of the wet biosolid compared to other scenarios (Figure 2). All land applied scenarios had a beneficial fertilizer offset credit as well. This credit was largely similar between these scenarios, as the phosphorus content of the solid drove eutrophication impact for fertilizer credit and was assumed to be similar between scenarios. The lowest eutrophication potential was in the pyrolysis scenario. Toxicity Comparison Little difference was observed in freshwater ecotoxicity and human cancerous toxicity, largely due to the dominance of heavy metals, making up at least 99.5% and 96.2% in these two categories across scenarios. Heavy metal loads in the end product were assumed to be similar across all thermal processes, as only a small portion of the heavy metals would volatize, and the majority would remain in the solid residuals. In terms of PFAS potential, pyrolysis did not appear to remove much PFAS, but instead transform them into different PFAS species. Incineration and gasification were the lowest in PFAS potential, due to their high PFAS removal performance. This led also to lower human noncancerous toxicity potentials (Figure 3). Overall, heavy metals had the highest impact in human noncancerous toxicity for each scenario, but PFAS were still impactful. It should be noted that two effect factors were presented for noncancerous toxicity in Holmquist's modified USETOX model (based on epidemiological vs. rodent data). To be conservative, the higher of the two was used. Relative Impacts of Inputs Figure 4 shows the relative contribution of each input to the relevant impact categories, focusing on the thermal drying only scenario for simplicity. Most notably, it can be seen that the impact of heavy metals makes up between 93.2-99.5% of each toxicity potential category for thermal drying only. PFAS emissions comparatively only made up to 6.7% of the toxicity emissions (for human noncancerous toxicity). Eutrophication is mainly impacted by electricity use, while GWP is mainly impacted by scope 1 emissions. The PFAS potential impact category was not shown in the figure. This is because there is only one input to the PFAS potential broken up by the effluent phase the PFAS are emitted to in each scenario. CONCLUSION/SIGNIFICANCE This analysis highlights the importance of PFAS when taken into context with other known and regulated toxicants in biosolids such as heavy metals. Heavy metals made up at least 99.5% and 96.2% of freshwater ecotoxicity and human cancerous toxicity impacts across all scenarios. Even when a conservative assumption for PFAS toxicity was used for human noncancerous toxicity, heavy metals made up the largest portion of this impact as well. This analysis also highlights two biosolids alternatives, gasification and pyrolysis. Gasification was observed to be a relatively low impact alternative in most of the LCA categories that also safeguards against uncertainty around PFAS toxicity and future regulations in biosolids. This option provides not just transformation, but potentially good removal of PFAS species. Pyrolysis however was observed to be the best option in this analysis when considering the relatively low impact of PFAS on the toxicity potential impact categories, and that pyrolysis had the lowest impact in the other critical LCA impart categories. The key impact of this work is the reframing of PFAS as not the only consideration, but one of many aspects to be included for holistic biosolids management.

Introduction Metro Water Recovery, based in Denver, Colorado, serves 2.2 million population equivalents through the Robert W. Hite Treatment Facility (RWHTF) and the Northern Treatment Plant. RWHTF has a design capacity of 220 MGD and treats an average daily flow of 130 MGD. The facility's solids handling complex includes gravity thickening, grease processing, dissolved air flotation thickening of waste activated sludge, two-phase mesophilic anaerobic digestion, centrifuge dewatering, phosphorus recovery, and biosolids management for storage, hauling, and land application. In 2016, Metro piloted the MagPrex post-digestion phosphorus recovery system (PREX) to address challenges posed by enhanced biological phosphorus removal (EBPR). EBPR results in high concentrations of soluble phosphorus in the digesters, which combines with magnesium and ammonia to form nuisance struvite, causing scaling in equipment, lowering dewatering efficiency, and upcycling phosphorus through the treatment process. In response to stricter effluent TP limits imposed by the Colorado Department of Public Health and Environment (CDPHE), Metro commissioned the world's largest PREX reactor in October 2020. This system allows RWHTF to reliably meet a TP target of 0.7 mg/L, with fewer operational disruptions associated with nuisance struvite formation. Phosphorus Recovery System Overview The PREX reactor is a completely mixed system receiving 600-800 GPM of digester effluent with orthophosphate (OP) concentrations between 350-450 mg/L. PREX quickly transforms OP into struvite by adding magnesium chloride and raising pH through air stripping via coarse air bubble diffusers . The reactor can harvest struvite as a reusable product, with large crystals settling in the reactor cone for separation, Figure 1. Since startup, the reactor has achieved >90% OP conversion, enabling Metro to maintain effluent TP concentrations below 0.4 mg/L. Optimization Objectives While the PREX system has successfully achieved the required OP conversion, opportunities for further optimization quickly became apparent. Initially, only 2% of the struvite formed in the PREX reactor was captured for reuse, and maintenance costs to address nuisance struvite downstream remain high (Figure 2), estimated at over $9,000 per month in labor alone. This study aims to enhance the system design and assess the downstream impacts on centrifuge dewatering, struvite scaling in PREX effluent, and centrate piping. The optimization efforts are guided by three key objectives: 1. Maximize Struvite Recovery: Increase recovery beyond the initial average of 300 lbs/day to meet the reactor's estimated potential of 2,000 lbs/day. This effort investigates changes to process operation and configuration to increase struvite recovery. 2. Minimize Downstream Struvite Accumulation: Address scaling in the PREX effluent and centrate system. Although anerobic digestors have observed a reduction of nuisance struvite, portions of PREX effluent system require a high pressure cleaning every three weeks to remove struvite accumulation. 3. Optimize Residual Magnesium for Dewatering: Evaluation of residual magnesium from the PREX reactor to improve dewatering efficiency by reducing polymer demand and lowering chemical costs. Methods The PREX reactor was operated under various conditions, including adjustments to hydraulic retention time (HRT), pH, and Mg:OP ratios. A 3D multi-phase turbulent model was developed to refine operational settings and predict particle settling efficiency. To assess struvite scaling, ion mass balances were performed on centrate samples collected at two points: upstream at the centrifuge discharge and downstream at the outlet to the sidestream deammonification reactor. These samples were analyzed for OP, TP, magnesium (Mg), and pH. Additionally, soluble and total magnesium concentrations were measured in the PREX effluent and centrate. The relationship between these concentrations, polymer demand, and dewatering performance was explored. Conductivity and zeta potential measurements were collected as potential proxies for cation concentrations, enabling real-time monitoring of dewatering performance. Results 1.Struvite Recovery Optimization The 3D CFD model revealed that only 10% of struvite crystals under 250 μm in size could be captured under typical airflow conditions (Figure 3). Particles with a diameter >700 um had an average recovery rate of 80%. However, over 50% of the struvite produced by PREX was less than 250 μm, significantly limiting recovery. Improvements included adjusting classifier operation such as classifier bed height , introducing dilution water, and recycling classifier overflow. These changes increased struvite recovery from 300 to 1,200 lbs/day. 2.Minimizing Downstream Struvite Accumulation While the PREX system significantly reduced nuisance struvite formation in the digesters, accumulation persisted in the PREX effluent piping due to the presence of small struvite crystals and turbulent flow, which caused localized pH shifts and the precipitation of residual OP, Mg, and NH4. Polyvinylidene fluoride (PVDF) liners are being installed in the effluent lines to reduce turbulence and mitigate scaling. Ongoing ion mass balance sampling will provide further insights, with results to be presented at the conference. 3.Residual Magnesium and Dewatering Performance Maintaining residual magnesium concentrations of 50-60 mg/L reduced normalized dewatering polymer usage per flow by 39%, resulting in chemical cost savings of $800,000 annually (from $2.9 million to $2.1 million) (Figure 4). Conductivity and zeta potential measurements strongly correlated with cation concentrations, indicating their potential use for real-time monitoring and future optimization. Conclusions The optimization of Metro's PREX system demonstrates the potential for substantial improvements in phosphorus recovery and operational reliability. Struvite recovery increased fourfold, highlighting the importance of fine-tuning operational parameters and integrating recycling strategies. Addressing scaling in effluent lines through material upgrades and improved chemistry management will further enhance long-term system reliability. Optimizing magnesium levels improved dewatering performance and delivered substantial chemical cost savings. Potential real-time monitoring using conductivity and zeta potential as proxies for cation concentrations offers an innovative approach to operational control and performance optimization. As phosphorus regulations become more stringent, these advancements position Metro as a leader in sustainable resource recovery. These findings provide valuable insights for other utilities aiming to enhance phosphorus recovery, minimize operational disruptions, and reduce chemical usage, advancing the next generation of phosphorus management for water resource recovery facilities.

SUSTAINABLE SLUDGE MANAGEMENT BY CONTROL OF MICROBIAL POPULATION DYNAMICS Rob Whiteman, Ph.D. Technical Director, ABS Inc. For 100+ years engineering technology has employed capital intensive processes for biological wastewater treatment (WWT) using the approach of in-situ growth to control the development of biology under aeration, to flocculate in the clarifier to meet Water Quality Standards. Issues of filamentous bulking and poor settleability result in less concentrated biosolids meaning larger volumes to handle along with poor dewatering characteristics meaning more polymer and expense for dewatering. The increased use of cleaners, antibiotics and hand sanitizers has led to deterioration in the microbial populations for good floc structure and settleability, while reducing viability. The handling and disposal of these biosolids residuals represents a significant cost to Utilities, which employ a range of equipment to reduce the volume and mass: digesters, presses, pelletization or incineration. With increasing environmental pressures for sustainable disposal methods driven there is a need for innovative 'point source reduction' (PSR) technologies and a method or process which improves settleability, allowing an increase in the mean cell residence time (MCRT), hence reduction in wastage and new ways to meet Class A pathogen reduction standards inexpensively. However, now with the discovery of microplastics in drinking water and biosolids, there is even greater demand for a point source reduction technology. Advances in biotechnology and understanding the role of microbial population dynamics in wastewater treatment have led to the investigation of PSR technology, a new approach using an ex-situ growth process to grow and routinely inject probiotics which controls the biology in the treatment system. This resulted in unprecedented beneficial results discovered over the past decade, which improved settleability allowing an increase in the mean cell residence time (MCRT) and hence reduction in wastage. With this reduction in biosolids residual, it was possible to extend the holding times to further reduce the mass of biosolids while improving the quality to make a Class A biosolids residual and in some cases Class AA, which is a breakthrough providing a sustainable, low-cost, affordable method of treatment and disposal. Side Stream Reactor: Biofermentation is a process and method for growing single cell microorganisms in a standalone side stream reactor. The process allows cultivation of specific microbes which are injected from the side stream reactor and have not been exposed to the selection pressures experienced by the wastewater treatment plant. The cultures are grown overnight and injected daily as a 'probiotic' allowing complete control of the microbial population for the first time in 115 years, since development of activated sludge in 1910. Improving Settleability: Settleability is the limiting factor for environmental engineers designing smaller, more compact activated sludge systems. Filamentous bulking is a common occurrence in municipal wastewater treatment, which causes poor settleability by bridging and preventing water escaping from between the flocs as the sludge concentrates in the clarifier. Several of these microorganisms are often associated with high loads of fats, oils and grease, such as Microthrix parvicella and others with long MCRT's of greater than 20 days, such as 0041 and 0675. While the concept of ageing was supposed to encourage flocculation, few systems can operate beyond 25 days without experiencing bulking. Through the introduction of selected microbes using the Biofermentation process, it has been possible to improve settleability substantially allowing the mixed liquor suspended solids (MLSS) to be increased by increasing the MCRT. . The process has been applied at one plant for 3.5 years during which time the MLSS has been raised from 3-4,000 to 9-10,000 with improved settleability and clarity. The improvement in floc structure is seen in Figure 1, while the settleometers are shown in Figure 2. This extended aeration plant now operates with an estimated MCRT in excess of 70 days. REDUCING BIOSOLIDS PRODUCTION: With the ability to improve settleability and hence increase MCRT comes less mass wasted. In part of another 5 year 'Cause and Effect Study', the biosolids production versus food to microorganism ratio (F:M) was compared as shown in Figure 3. The data shows a reduction in the amount of biosolids produced irrespective of F:M when treated with the probiotics. More importantly the R2 in the untreated is only 0.458, while 0.968 in the treated, which demonstrates a more stable, predictable biomass. Overall, the process showed typically a 60+% reduction in biosolids production in the aeration basin. Reducing biosolids production by this amount significantly reduces downstream handling and processing not to mention disposal. 'ADVANCED DIGESTION': Advanced digestion was used which involved injecting probiotics, which compensate for the long MCRT. Figure 4 shows the results in the lbs of biosolids produced per lb of BOD reduced over 10+ years comparing hauling to a chemical process (BCR) and probiotics with and without Advanced Digestion. When only using probiotics in the wastewater treatment system there is a 54-70% reduction in the amount of biosolids produced depending on whether comparing hauling or the chemical process. When coupled with the Advanced Digestion process this plant has experienced in excess of 90% reduction with no biosolids hauled from the facility since April 2017 through 2022. The digester was allowed to digest biosolids without addition of new biosolids for over 60-days. A geometric mean for fecals was taken, which showed that the biosolids met Class A standards (See Figure 5). Metals were also measured which indicate the residuals meet a Class AA under Florida Law. Mass reduction occurred as previously discussed, which is more paramount with new legislation on microplastics and other biosolids contaminants. This facility continues to lead the way in using Biotechnology to resolve biological challenges. In summary, the addition of probiotics has now been proven and even validated with respect to improving settleability by control of population dynamics, providing the operator more control to increase MCRT, while reducing biosolids production 60% economically. This has the ensuing benefits of opening up space downstream for Advanced Digestion, which further reduces biosolids production of up to 90% with the potential to create a Class A or AA residual or economically dispose of the final biosolids because of the substantial reduction in mass and volume.

Intensicarb® is a vacuum-based sludge concentration technology, that when installed to intensify anaerobic digestion at a Water Resource Recovery Facility (WRRF) could decrease hydraulic retention times (HRT) while maintaining solids retention times (SRT), providing various benefits towards process intensification. Previous work has demonstrated Intensicarb® feasibility for fermentation intensification (Okoye et al. 2022) and digestion intensification (Khadir et al. 2024) at lab scale as well as its economic feasibility for use as fermentation intensification for onsite WRRF supplemental carbon production (Armenta et al. 2023). This study presents a techno-economic analysis (TEA) of the Intensicarb® process when used to intensify mesophilic anaerobic digestion (MAD) at WRRFs of multiple sizes (10 million gallons per day (MGD), 50 MGD, and 250 MGD of influent flow). Significant reductions of overall lifecycle costs, including reductions in process volume and facility footprint were seen for all 3 facility sizes analyzed. Methodology Three facility sizes were evaluated, based on 10, 50, and 250 MGD influent flows, representing small, medium, and large facilities. This was correlated to digester solids loadings of 11,000, 54,000, and 270,000 lb/day respectively. Four scenarios of increasing intensification were developed and evaluated for each facility size. These scenarios were based on the decoupling of HRT and SRT provided by the IntensiCarb® technology. Average operating SRT was assumed to be 30 days for all scenarios, and the HRT was changed from 30 days (conventional MAD), to 15, 7.5, and 5 days with IntensiCarb®. These were designated as intensification factors (IFs) 1, 2, 4, and 6. Simplified process diagrams showing the conventional MAD process and MAD with IntensiCarb® are shown in Figures 1 and 2, respectively. Flows and loads used in each scenario were developed in Excel (Microsoft), with the assumption that volatile solids destruction was constant over the range of intensification studied (Khadir et al. 2024). Further assumptions are shown in Tables 1 and 2. These parameters were then used to develop the TEA, using a Net Present Cost approach and assuming a 30-year project lifespan. A nominal discount rate of 6% and an escalation rate of 3% were assumed (Construction Cost Index 2019-2022 2022; Guidelines and Discount Rates for Benefit-Cost Analysis of Federal Programs 2023). Costs associated with this TEA were developed based on vendor budgetary estimates for vacuum evaporators from PRAB and IWE, and AD tank mixers from Anaergia. Other equipment estimates, including conventional concrete AD tanks and associated pumps were developed based on previous Brown and Caldwell designs. Operational costs outside of labor, including electrical energy costs for pumping and mixing, sludge heating energy costs, and rehabilitation and replacement costs were developed based on the process modeling outputs and the budgetary estimates outlined above. A sensitivity analysis based on several key unit costs was developed to better estimate lifecycle costs for sites in North America with different operating costs. To simplify the analysis and provide a more conservative estimate of IntensiCarb®'s potential cost savings, two key potential benefits of the IntensiCarb® process were not included in this analysis. These were biogas recovery enhancement, and reduction of nitrogen levels in the sludge (Muller et al. 2024). Additionally, vendor estimates were used to develop physical layouts for all scenarios, which were compared on a volume and footprint basis to determine any physical space savings provided by the Intensicarb® technology. Results and Discussion The results of the TEA indicated significant reductions in process volume and footprint, particularly in larger facilities, leading to potential cost savings. These results are shown in Figure 3. The economic analysis showed that higher intensification factors generally result in lower life cycle costs, with the most substantial savings observed at intensification factors of 4 and 6. However, the benefits diminish at higher intensification levels for midsize plants due to the discrete sizes of evaporator equipment available. Life cycle costs for the 50 MGD facility are shown in Figure 4. The study concludes that IntensiCarb® technology is viable at small, medium, and large scales, with the largest savings seen at IF 6 for all sizes (27%, 26%, 16% NPC savings over conventional MAD seen at IF 6 for the small, medium, and large facilities respectively). Through a sensitivity analysis, key factors driving life cycle costs were identified, with natural gas, electricity prices, and IntensiCarb® facility construction costs causing the most impact on NPC. The baseline values for these costs, as well as their identified upper and lower bounds, are shown in Table 3. Future work should focus on empirical testing and theoretical analysis to refine cost assumptions and explore additional benefits like biogas quality improvement and nutrient recovery.

Introduction The Microbial Hydrolysis Process (MHP), developed to enhance anaerobic digestion (AD) performance, uses the hyper-thermophilic bacterium Caldicellulosiruptor bescii (C. bescii) in a post-digestion hydrolysis process. Unlike pre-digestion methods (Hansen et al, 2021), MHP feeds AD digestate to a 75°C hydrolysis tank populated with C. bescii for a hydraulic retention time of two days (Parry et al. 2022). Here, C. bescii and its enzymes hydrolyse cellulose and complex carbohydrates and convert them to volatile fatty acids (VFAs) in an anaerobic, neutral-pH reactor. The VFAs are then returned to the AD, where methanogens convert them into biogas. Figure 1 illustrates the microbial activity AD with MHP. The performance of AD with MHP has been tested at lab- and pilot-scale with consistent results; the addition of MHP increases volatile solids reduction (VSR) to greater than 75%. Figure 2 shows the results of MHP studies on solids from 4 different water resource recovery facilities (WRRFs) with well-performing existing AD systems. Encouraged by pilot results, VandCenter Syd (VCS) in Denmark is now designing MHP implementation at its Ejby Mølle WRRF, and conceptual and preliminary designs have been developed for several WRRFs in the US. An ongoing pilot at North Davis Sewer District (NDSD) in Syracuse, UT has operated at steady-state since July 2024. Data from this pilot and prior studies are used to refine a process model (Sumo) to predict AD performance with MHP based on feed characteristics. The results of the pilot study, the model and preliminary design, and analytical results for pathogens, microbial populations, sludge dewaterability, and sludge characterization will be presented. Material and Methods AD with MHP has been studied using solids from several facilities at both lab and pilot scales. Most recently, pilot-scale testing has been conducted at North Davis Sewer District in Syracuse, UT. The pilot-scale system consists two 325-gallon anaerobic digesters and one 140-gallon MHP reactor. Pictures of the pilot trailer located at NDSD and the pilot trailer process room are shown in Figure 3. The NDSD pilot system is operated to simulate proposed process changes to achieve Class A biosolids, boost VSR, and increase biogas production, using a staged AD with batch intermediate MHP and heat recovery. A simplified process flow diagram of the pilot MHP system is presented in Figure 4 and a process flow diagram of the proposed full-scale system with heat recovery is presented in Figure 5. Pilot Anaerobic Digester 1 (AD1) was fed digested sludge once per day from the full-scale digested sludge transfer pumps. Sludge from AD1 was automatically fed 4 times per day to the MHP tank, and hydrolysed sludge from the MHP tank was fed 4 times per day to Pilot Anaerobic Digester 2 (AD2). Characteristics of the full-scale system feed and digestate as well as the contents of AD1, the MHP tank, and AD2 were measured using standard methods. Routine analyses to monitor performance and stability include volatile and total solids, total acids, alkalinity, and pH, while additional sludge analysis assesses pathogen reduction, microbial populations, sludge dewaterability, carbohydrate composition, and VFA fractionation. The VSR of the digestion process with MHP, calculated using the volatile and total solids measurements, was the key indicator of performance. Results of this pilot study are used to calibrate a process (Sumo) model to predict digestion performance for facilities with different feed characteristics and will be discussed in the final paper. Findings Previous studies have proven significant improvement in digester performance with the addition of MHP, as indicated by the increase in VSR to 75 and higher. These findings were corroborated by the results of the pilot at NDSD, shown in Figure 6. The existing AD system at NDSD achieves 63.8 percent VSR on average, and the addition of MHP improved performance to 75 percent once steady state was achieved. Table 1 presents the comparison the proposed staged AD with batch intermediate MHP to baseline AD performance. The increased VSR and improved dewaterability result in a 38% decrease in wet tons of biosolids produced per year, and an estimated 18% increase in biogas production assuming the biogas yield is unchanged. Further, laboratory analyses confirm that batch MHP reduces the concentration of fecal coliform below detectable levels, meeting the EPA criteria for pathogen reduction in Class A biosolids. The operational data and results of routine analyses, microbial population analysis, and sludge characterization from the pilot study at NDSD have informed the continued development of a model to simulate the impact of MHP based on influent sludge characterization. With this model, performance of AD with MHP at other facilities can be predicted. Significance MHP represents a significant advancement in AD technology and offers the highest achievable VSR for municipal WRRF AD systems to date. By allowing the digestion of cellulose and other recalcitrant organics, MHP maximizes AD efficiency, thus increasing biogas yield and reducing biosolid production. These improvements result in substantial cost savings on biosolids management -- a major interest for WRRFs. These benefits position MHP as a scalable, innovative solution to enhance AD performance globally.

Introduction Advanced Primary Treatment (APT) is a process in which filtration or micro-screening technology is used to replace or supplement Conventional Primary Treatment (CPT). In this project, the Cloth Disc Primary Filter (CDPF) and Proteus Primary Filter (Proteus PF) have been demonstrated for 3 and 1.5 years, respectively. Significantly higher treatment performance values (i.e., 40 to 50 % higher) were observed with both primary filtration (PF) technologies compared to CPT. PF increases capacities of primary and secondary treatment systems minimizing (or sometimes even eliminating) expansion requirements for existing installations or reduce the required footprint for new installations. Primary filtration is also the most effective carbon diversion strategy at Water Resource Recovery Facilities (WRRFs). Carbon diversion involves reducing the organic load on secondary systems by redirecting more biochemical oxygen demand towards the solids line at the primary treatment stage, which reduces the aeration requirements for aerobic biological processes downstream. Resultant benefits of PF are: (1) savings in aeration energy costs, (2) increase in digester gas energy production, and (3) reduction in primary and secondary treatment footprint and volume requirements. Significant CAPEX and OPEX savings are realized because of these benefits. One important design and operational challenge for PF is the high primary sludge volume produced during backwash operation. Sludge produced from PF backwash is also thinner (i.e., 0.2 to 0.4 %) compared to CPT sludge. Thickening is an essential process component of PF systems and its design conditions are quite different due to high sludge volumes, low solids concentrations, and significant differences in sludge characteristics. Optimization of PF systems to minimize backwash sludge volumes and still achieving high treatment efficiencies is one of the main objectives of this on-going technology research and demonstration project. Methodology Funded by California Energy Commission, the focus of this project is to evaluate the treatment and hydraulic performance of several PF technologies at Linda County Water District's (Linda) WRRF located in Olivehurst, CA (Fig. 1). General information for the Proteus PF and CDPF systems are provided in Table 1. The Proteus PF and CDPF units are shown in Figs. 2 and 3, respectively. CDPF unit has been in operation since January 2022 and Proteus PF has been in operation since July 2023. The specific objectives of the project include: (1) Evaluate the performance of PF technologies; (2) Improve the treatment and hydraulic performances; (3) Optimize the design & operational criteria including sludge treatment system, and (4) Evaluate impacts on downstream secondary process. Inline turbidity/TSS sensors and flow meters have been installed at each PF system and sensor data are synchronized to provide real-time monitoring of treatment performance. Inline sensor data are complemented by lab analysis of 24-h composite samples from influent and effluent channels of each unit. Overall, the evaluation is based on hydraulic and treatment performances. The hydraulic performance was assessed using solids loading rate (SLR), hydraulic loading rate (HLR), and backwash reject ratios (BRR) of both PF systems. High HLR, low BRR, and high SLR typically correlate to lower capital and operational costs. The key parameters impacting BRR include: HLR, SLR, pressure build-up rate, backwash flowrate, and backwash frequency and duration. The treatment performance was evaluated based on total COD (tCOD), soluble COD (sCOD), total BOD (tBOD), soluble BOD (sBOD), TSS and total Kjeldahl nitrogen (TKN) removal. Treatment Performance of APT systems The performance of the Proteus Filter and Cloth Disk Primary Filter are reported and compared to conventional primary sedimentation. Proteus Filter: The TSS and COD removal performances of the Proteus Filter are shown in Fig. 4 and Fig. 5, respectively. Results were obtained based on 24-hr composite samples collected between July 2023 and September 2024. More than 100 samples were used to evaluate the removal performances. As shown in Fig. 4, influent and effluent TSS concentrations averaged at 471 and 100 mg/L, respectively, when the unit was operated between its average and peak flow design conditions. Influent and effluent COD, as reported in Fig. 5, averaged 981 and 419 mg/L, respectively. Cloth Disk Primary Filter: The TSS and COD removal performances of the full-scale CDPF system are shown in Fig. 6 and 7, respectively. Results were obtained based on 24-hr composite samples collected between May 2022 and September 2024. More than 150 samples were used to evaluate the removal performances. As shown in Fig. 6, influent and effluent TSS concentrations averaged at 421 and 56 mg/L, respectively. It should be noted that even though influent wastewater TSS concentrations varied significantly, a relatively stable effluent TSS between 50 to 70 mg/L was observed. Influent and effluent COD, as reported in Fig. 7, averaged 805 and 335 mg/L, respectively. Overall, the CDPF performance has been observed to be similar to the results obtained from previous demonstrations where 75-85% and 50-60% removal for TSS and COD were observed, respectively (Caliskaner et al., 2018, 2019, 2020, 2021, 2022). Performance Comparison versus Primary Sedimentation: Both PF systems were operated in parallel with the existing primary clarifiers at the Linda WRRF, and performance comparisons were conducted using samples taken during the same 24-hr sampling intervals. As seen in Fig. 8, primary clarifier (PC) achieved average removals of 38% for COD and 66% for TSS. As seen in Fig. 8, the Proteus PF unit achieved average removals of 65% for COD and 85% for TSS when operated at 2 gpm/ft2, which are 40 to 50 % higher compared to PC removal efficiencies. Similar high treatment performances were also obtained with the CDPF system when compared to primary clarifier. Average removals of 56% for COD and 85% for TSS were achieved with the CDPF system. Hydraulic Performance of APT systems The optimum design and operational conditions are investigated in this project considering HLR, SLR, headloss development (across the filter media), and BRR ratios. Summary of hydraulic values observed for both PF systems are presented in Table 2. PF backwash is triggered by preset filtration time or maximum headloss development , whichever comes first. Headloss development is measured by pressure transducers. Headloss development rates were observed to change with changes in HLRs. Proteus PF: As illustrated in Fig. 9, headloss development increases as the HLR increases resulting in higher BRRs. The daily average headloss development under HLR of 2 gpm/ft2 and 6 gpm/ft2 were 5.2 and 6.2 psig, respectively. The increased flowrate and HLR caused increased accumulation of particulate material within the filter media resulting in larger headloss values and hence higher BRR values. The HLR and BRR values with respect to time are summarized in Fig. 10. The Proteus PF system has been operated between 2 and 9 gpm/ft2 most of the demonstration resulting in an average BRR of 9.4%. Daily average HLR and SLR for the Proteus PF System during the demonstration is shown on Fig. 11. Based on an analysis of HLR and BRR values, HLR ranging from 2 to 2.5 gpm/ft2 are considered for optimum average flow design conditions and 5 to 6 gpm/ft2 are considered for peak flow design conditions. Cloth Disk Primary Filter: The volumes of filtered effluent, backwash reject, and sludge wasting are all monitored along with HLR and SLR values. Recorded HLR and BRR values are shown in Fig. 12. Similar to Proteus PF system, headloss development and BRR increase as the HLR increases. Average daily BRR values were observed to be approximately 10 percent under average design flow/loading conditions. Based on an analysis of HLR and BRR values, HLR value of approximately 2 gpm/ft2 is considered for optimum average flow design conditions and 4 to 4.5 gpm/ft2 are considered for peak flow design conditions. Impact of Primary Filtration Systems on Energy Consumption and Recovery One major project objective is to demonstrate the energy and capacity impacts of PF on WRRFs. Specifically, impacts of PF on MLE process and three Advanced Secondary Treatment technologies including Microvi, AGS and MABR were evaluated. Energy savings and footprint reductions are measured directly in addition to the process modeling studies to further investigate the impacts on BNR kinetics. The impacts of PF on secondary treatment and anaerobic digestion were predicted with SUMO process modeling using the obtained PF demonstration data. PF results in 25% in aeration energy savings and 35% increase in digester gas production (Fig. 13).

Introduction: A drought in eastern Colorado in 2021 and 2022 spurred South Platte Renew (SPR) to reconfigure its data management practices for its Beneficial Use (BU) Program. Low SPR needed to become resilient to future scenarios that could prevent biosolids land application. Drought led to crop failure, which in turn led to high nitrate soil levels barring biosolid application. SPR needed an inventory to assess the lands that could be applied to, inform future biosolid management needs, and track environmental trends in application. A Power BI Dashboard would provide an efficient solution by centralizing current and historic data and enhancing communication across SPR. Design: To develop the site inventory, SPR redesigned its data management practices and developed a dashboard to assess each biosolid application site. SPR expanded its sampling plan while centralizing the existing data. SPR compiled application, soil, crop, and biosolid data. SPR increased its soil sampling frequency to pre-planting and post-harvest to monitor nitrate uptake. SPR also created a dynamic application site status, an interactive timeline for contingency planning, and historic graphs showing environmental parameters like weather conditions. The Power BI Dashboard consolidated data from multiple sources into a user-friendly, visual interface accessible to all teams. The dashboard allowed SPR staff to monitor and analyze this information in real-time, enabling informed decision-making and timely adjustments to the biosolids application process. Implementation: To address the diverse needs of stakeholders, the dashboard integrated data from agricultural systems, weather databases, and biosolids management software. It tracked each field's crop history, ensuring compliance biosolid application. The tool also facilitated scheduling and planning for soil sampling, aiding the biosolid application process. It also compiled information for each plot, summarizing metal and nutrients results from historic soil sampling events. Furthermore, it contains data from SPR's test plot that has crop data from the 1990s so SPR can review trends due to biosolid or fertilizer application. Project Results: By centralizing critical data and improving access to information, the Power BI Dashboard enhanced operational efficiency, reduced planning time, and promoted better communication. It enabled the program to respond to changing weather conditions and crop needs, ensuring the sustainable and responsible use of biosolids in agriculture. It has helped South Platte Renew be more resilient to climate change as land available for biosolid application and storage space can be predicted while using historic data to inform management practices.

This presentation will explore the status of gasification and pyrolysis system projects that are either in development or recently commissioned. With ever increasing restrictions on landfill and land application and a growing concern with emerging contaminants, specifically perfluorinated compounds (ie. PFAS), there is increasing interest in these types of thermal technologies. The state of the research on these technologies to deal with emerging contaminants will also be presented. The presentation will provide a brief background on biosolids process technologies, highlight current biosolids trends including the barriers impacting technology and resource recovery, and provide an update on gasification and pyrolysis technologies that are currently being implemented in the marketplace. The presentation will present a biosolids road map and risk triggers that utilities can use in planning (Figure 1). There are several biosolids gasification and pyrolysis systems and demonstrations that are being planned globally including several in North America (such as Bioforcetech, Ecoremedy, Earthcare, Harvest Technologies, Pyrocal, Aquagreen and Heartland Technologies). The presentation will present an update on the status of these projects in North America as well as a status of projects internationally including in Germany, Australia and Asia. As part of the presentation, the results of a technology screening evaluation conducted for a large regional gasification and pyrolysis facility in Australia will be discussed. As most gasification and pyrolysis processes require upstream drying (Figure 2), the evaluation considered various upstream processing alternatives including anaerobic digestion, solar drying and thermal drying. The screening evaluation only considered technologies that have full scale operating installations and technologies that produce a biochar for beneficial use. These gasification and pyrolysis technologies for sludge and biosolids have not had great success historically and many past attempts to commercialize these processes have not been successful. Lessons learned from early adopters and considerations for future planning will also be discussed. The presentation will provide an update on technologies that are being implemented in the marketplace.