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Mesophilic anaerobic digestion is the most deployed biological sludge stabilization process at wastewater treatment plants in North America. It also plays a central role in energy and resource recovery from wastewater treatment plants. This paper explores the application of medium vacuum pressure (~100 mbar) operated in a side stream recirculating reactor as a mechanism for process intensification and resource recovery, utilizing the IntensiCarbTM process. Currently within the industry the primary means of process intensification are either through the elevation of operating temperature (ex. thermophilic digestion), pre-conditioning of sludges (ex. thermal hydrolysis) or separation of solids and hydraulic retention time (ex. recuperative thickening). The IntensiCarbTM process utilizes the decoupling of SRT and HRT to increase process capacity while simultaneously reducing the influence of toxic metabolic by products through extraction (ex. ammonia-N). This paper discusses the results of side-by-side comparison of conventional mesophilic digestion with varying intensification factors (2x, 3x, 4x) for bench-scale trials conducted at Western University in London, Ontario, based on the process flow provided in Figure 1. The intent of this experimental design was to focus on understanding the fundamental process changes that occur when vacuum evaporation is applied to a conventional mesophilic digester. In particular, the question being investigated is whether the evaporation process and the extraction of materials result in any fundamental changes in the operation of the digestion process or does it simply operate in a manner similar to recuperative thickening. Table 1 provides a summary of the operating conditions tested, with Intensification Factor 1 (IF1) representing the control and IF2, 3 and 4 representing varying degrees of decoupling of both SRT and HRT. All the digesters were fed a mix of primary and secondary sludge (Ave. TS = 2.9%, VS =2.18%) periodically collected from the Greenway Wastewater Treatment Plant in London, Ontario. The digesters were all operated at mesophilic temperatures (~35-37 °C). Across the range of intensification factors tested, in general, all processes demonstrated effective anaerobic digestion of the sludge, noting that the highest intensification factor (IF-4) there were episodic instability events (data not shown). This suggests that either the process is approaching its maximum extent of intensification, or the specific combination of HRT and SRT is not sustainable. A number of factors could be causing this observed instability including insufficient active fraction of biomass at the extended SRT, the biomass population is at an inflection point with shifting populations or an undefined stressor is impacting the population. Additional research will be required to explore the ultimate limits of intensification. What is apparent from the data in Table 1 is that in general IntensiCarbTM does not appear to significantly change the extent of digestion with the VSr ranging from 46-55 percent relative to the control at 50 percent. However, the rate of digestion is significantly enhanced by the increase in solids concentration, resulting in overall higher solids throughput rate and rate of methane generation increasing from 0.29 m3-CH4/m3-digester-day to a maximum of 1.08 m3-CH4/m3-digester-day (Figure 2). A challenge with most process intensification strategies deployed to date is the impact of metabolic byproducts on the process. Of particular interest is ammonia, as it is produced through the decomposition of proteins, which constitute a significant fraction of sludge materials. To date no technology has effectively managed ammonia-N in-situ, resulting in risks for process instability and or significant population shifts, as reported by Mah et al. (2017) for THP. The concentration of ammonia in digesters tested were very similar (Table 1). This is significant in that the control of ammonia in the digester could support high loadings without the negative impacts. Figure 3 simulates what solids concentrations sludge would need to be loaded at to a conventional digester to achieve the same degree of intensification and the resulting total ammonium concentration in the digester would be. What is apparent from the graph is that conditions similar to those observed in thermal hydrolysis would need to be achieved, but the resulting total ammonia concentrations would approach the current limits of those systems. Furthermore, the feed solids would need treatment to reduce the viscosity to make the material pumpable. Figure 4, presents the nitrogen balanced conducted across each system, showing significant removal of ammonium-N to the condensate of the evaporator from the digestate. Supporting the observation that the IntensiCarbTM process creates a unique condition where the negative impacts of ammonia can be directly controlled in a highly loaded digestion process. Furthermore, the condensate is a very clean liquid, devoid of solids making it an ideal solution for ammonia recovery and beneficial use; potentially eliminating the need for centrate treatment for nitrogen. The combination of reduced nitrogen load and stable operations suggest the peak capacity of the IntensiCarbTM process was not achieved, in these tests. Plotting the empirically derived peak loading conditions for common stabilization processes and the resulting average total solids load, at a volatile fraction of sludge equivalent to the one used in this study, it is possible to investigate potential peak loadings; assuming similar process limitations of peer processes. The IntensicarbTM process, as currently tested, would appear to have a similar capacity to thermophilic digestion (Figure 5) for loading. However, at the highest average loading condition, IF-3, no process instability was observed, suggesting further intensification could be possible and should be investigated. Overall, the IntensiCarbTM, based digestion process is early in development but is demonstrating promise and the novel application of vacuum is generating conditions within digesters that have not been evaluated to date. The combination of process intensification through decoupling SRT and HRT and the depression of ammonia-N concentrations would suggest the system may achieve further enhancement as optimal operating conditions are defined. Concurrent with the completion of these bench trials a pilot facility is being planned by the Great Lakes Water Authority to further vet this process. This pilot will investigate the scalability of the technology, introduce of real-world operating dynamics, further optimize operating conditions to define a design loading criterion and develop a techno-economic analysis. Vacuum enhanced anaerobic digestion represents a novel process for the intensification of anaerobic sludge stabilization. Potentially offering unique opportunities for resource recover, ammonia-N and dissolved methane, as well as providing a mechanism to alleviate the current limitations associated with anaerobic digestion, metabolic byproduct toxicity. If successful, this technology could provide the next step forward in resource recovery from sludges.

APPLICABILITY The objective of this work is to develop an anomaly detection approach for biogas blowers using nonintrusive vibration sensors for machine conditions and health management. High-frequency vibration signals are collected from a tri-axial accelerometer installed on the exterior of the biogas blower casing. Long short-term memory (LSTM) artificial neural network algorithm is applied for signal classification. The proposed condition-based monitoring approach could provide a low-cost non-intrusive solution for asset management of compressors at water resource recovery facilities. INTRODUCTION Predictive maintenance (PdM) organizes maintenance activities according to the actual health state of machine tools, equipment, and systems [1]. Diagnostic PdM detect detects faults, determines root causes of operation anomalies, and estimates the current health state of a system under investigation to prevent unexpected failures. Condition-based monitoring is an approach for realizing diagnostic PdM as standardized by ISO 17359:2018. Condition-based monitoring can provide significant advantages in relation to product quality, safety, availability, and cost reduction in industrial applications. The recent advent of information and communication technologies and artificial intelligence presents a great opportunity to enhance the practice of data-driven assessment of the operation and maintenance of wastewater infrastructure [2, 3]. The objective of this study is to develop an anomaly detection approach for biogas compressors through vibration analysis for predictive maintenance. To achieve this goal, piezoelectric sensors and edge computing platforms (Raspberry Pi and Arduino board) are deployed on the biogas compressors. Machine learning algorithms are applied for classifying the collected vibration data for anomaly pattern recognition. METHODS The vibration monitoring in this study is implemented for compressor Unit 1 (KAESER) and compressor Unit 2 (SIEMENS) in a biogas facility. A low-power tri-axial accelerometer (model# ADXL345, Analog Devices, Wilmington, MA) is used with serial data communication devices such as Raspberry Pi and Arduino boards to collect vibration data from compressors. The data collection was initiated from the point of time when the compressor operated in normal condition and continued to the occurrence of any failures. The sampling frequency of the accelerometer is 1k Hz for each axis with a measurement interval of 30 minutes. Data are measured and obtained via Inter-Integrated-Circuit (I2C) bus. During the measurement, the sensor collects 10000 data points for each axis, which would take approximately 10 seconds, and is set to idle until the next measurement. The structure of the implemented condition-based monitoring is shown in Figure 1. The raw data includes the time stamp and acceleration data for the x, y, z-axis, and the sampled time for the corresponding sample. Sample x-axis vibration signals are visualized in Figure 2. The machine diagnosis is realized by scoring the anomaly levels of the vibration data, which will increase as failure approaches. Hence, an anomaly scoring model is tested to characterize the different levels of anomalies and provide an informative interpretation of forthcoming failures. The implemented model is inspired by dilated RNN network and Temporal Hierarchical One Class (THOC) network, which contributed to solving complex dependencies and vanishing gradients problems in layers. The THOC network is adopted and modified to develop the anomaly scoring model. The model consists of 3 long-short term memory (LSTM) layers with dilated skip connections. Details of the method implementation could be found elsewhere [6]. The sequential length of the transformed data is 36, and the input batch size is set to 128. In Fig. 3, each node represents a hidden RNN cell. The number of input nodes highlighted as green is determined by the sequential length of input data, which is 36. Similarity score obtained from the score function is translated to loss using the following equation that will be optimized through a training process. Adaptive Moment Estimation (Adam) optimizer is employed as it is known to have good capabilities of reaching global minimum with a high dimensional dataset. The structure of the implemented condition-based monitoring is shown in Figure 1. RESULTS The results of the model are shown in Figure 3. The input data (time-frequency domain) is visualized using power spectrum analysis. It is important to be noted that the Euclidean distance returns the length of a line segment between two vectors. Thus, the test data with a larger distance from the centers in each layer are expected to be assigned higher anomaly scores. As shown in Figure 3, anomaly points are captured when the power spectrum has abnormal patterns or when a peak value pops out from the power spectrum. Also, data points with small anomaly scores are not identified as anomalies, which might be sound as not all anomalies cause machine failures. Thus, a threshold should be carefully determined as it plays a critical role in linking such anomaly information with maintenance strategies. In this study, the threshold value is selected based on the 99.9 percentile in the anomaly scores. Different threshold values are used with an optimal threshold that prevents generating excessive false positives. The results may need to be compared to the actual machine condition such as whether abnormal operations were present while it was monitored. Since Euclidean distance may not be intuitive on a high dimensional dataset, different scoring functions are also tested for comparison. Chebyshev scoring function is adopted and the result is visualized in Figure 4. Chebyshev distance provides the greatest differences between two different vectors along any coordinate dimension. Hence, input data with the highest variance and difference are likely to obtain higher anomaly scores. As shown in Figure 4, the power spectrum with peak values tends to be identified as anomalies. In this case, the warning stage depicted with the orange line was applied with an additional threshold (99 percentile) to demonstrate a warning system that may be applicable to the data-driven maintenance strategy. In this study, the anomaly scoring model has been utilized to detect the abnormal vibration patterns and interpret them into anomaly scores. Based on the results from the proposed anomaly scoring model, a notification strategy can be established for further maintenance scheduling. The operation and maintenance manual or guidelines are provided by manufacturers of the machines. An example of the operation and maintenance manual of a compressor is shown in Table 1. Proper maintenance requires timely tracking of operation hours followed by appropriate actions such as checking oil levels, changing filters, and grease bearings. CONCLUSIONS AND RELEVANCE This study presents a condition-based monitoring approach for biogas compressors as an example of data-driven asset assessment. The test anomaly scores were calculated based on a similarity between unseen data and clusters that are learnable by machine learning algorithms. The study shows that condition-based monitoring using nonintrusive vibration sensors could be a useful asset management tool and providing early failing alarms of equipment embedded in WRRFs. The result of this study suggests that the operator's supervisory control and condition-based monitoring could be integrated for asset management (Figure 5). A combination of preventative maintenance following manufacturer's O&M manual and predictive maintenance guided by condition-based monitoring could lead to adaptive asset management program. Meanwhile, deploying condition-based monitoring solution at WRRFs may add additional responsibilities to the maintenance crew at WRRFs. Future studies are required to understand the operator demand, capital investment, and cybersecurity implications of condition-based monitoring for WRRFs. Attendance at this presentation will benefit operators and design engineers who are interested in data-driven asset management through condition based-monitoring. This study presented a novel application of deploying nonintrusive vibration sensors and edge computing for anomaly detection of biogas compressors. The method developed in this study could be applied in asset monitoring of other rotary equipment in WRRFs.

Introduction Water Resource Recovery Facilities (WRRFs) have increasingly been investigating and implementing co-digestion of food waste to generate revenue and maximize biogas production. In California, an additional regulatory driver is Senate Bill (SB) 1383, which requires organics diversion from landfills to mitigate short-term greenhouse gas emissions. To meet these goals, the City of Oxnard applied for and obtained an EPA grant to study food waste pre-processing and co-digestion implementation at the Oxnard Wastewater Treatment Plant (OWTP). Carollo developed a feasibility study for co-digestion implementation, and Dr. Matt Higgins (Bucknell University) conducted a bench-scale study involving co-digestion, dewatering, and odor testing of the City's sludge and source-separated food waste from the City's Del Norte Materials Recovery Facility (MRF). The results of the bench-scale study were then used to refine the design criteria and operational assumptions used in the feasibility study. This session will cover the approach and key findings of the bench-scale and feasibility studies. The City and the Carollo/Bucknell team hope that this study can serve as an example to other WRRFs interested in implementing food waste co-digestion. Bench Scale Study Three months of samples of primary and waste activated sludge from the OWTP and source separated food waste from the Del Norte MRF were sent to the Bucknell Anaerobic Digestion Laboratory (see photo in Figure 1) at Bucknell University. The food waste was diluted and blended before delivery. Four anaerobic digesters were operated, Digester 1 as a control with no food waste addition, and Digesters 2- 4 at increasing food waste loading rates. The target food waste VS loading rates to each digester expressed as the mass of VS from food waste divided by the total mass of VS in the digester feed (food waste plus feed sludges) were: Digester 2: 25%, Digester 3: 35%, Digester 4: 50%. In addition to evaluating digestion performance, this study also evaluated the impacts of food waste co-digestion on foaming potential, dewatering, and cake odor production. A summary of the findings from the bench-scale study is provided below: -Food waste characteristics: --The food waste slurry TS and VS content averaged 5.8 %TS and 81 %VS, respectively. -Digester performance: --The food waste did not impact the digesters pH, alkalinity, and nitrogen and phosphorus concentrations in any appreciable way at the loading rates in this study, except for the digester upset. --As expected, food waste co-digestion increased the volatile solids reduction (VSR), biogas yield (see Figure 2 for a graph of biogas production for the 4 Digesters), and methane content of the biogas. The overall VSR for the control digester averaged 45.9%, while the VSR for the test digesters was 52.4-59.5%. From this, the VSR for the food waste itself was estimated as 72-77%. --A digester upset in Digester 4 occurred when it was fed a food waste VS loading of 60% relative to the total VS loading. Based on this, a conservative maximum food waste loading for stable digestion of 45% was selected for the feasibility study. This limit allows for significant food waste addition while maintaining digester stability. -Foaming potential: --The viscosity and foaming potential increased as food waste loading increased. --No clear pattern was observed for volume expansion. The lower two loading rates of food waste (Digesters 2 and 3) had a greater volume expansion than the control, while at the highest food waste loading (Digester 4), the volume expansion was less than the control. -Dewaterability: oAs the food waste load increased, the polymer demand increased and the cake solids concentration decreased. The lower TS concentration could have been due to a lower concentration of divalent cations, which was observed in the higher food waste loading digesters. -Cake odor potential: oFood waste addition did not negatively impact cake odor potential. As a result of these bench scale results, the design team was able to refine site specific design and operational criteria for the full-scale co-digestion cost and energy feasibility study, including identifying the maximum design food waste VS ratios for stable digestion and quantifying anticipated changes in biogas production and revenue, polymer demand and costs, dewaterability and biosolids production post co-digestion. These criteria were adopted for the following desktop feasibility study. Feasibility Study The purpose of the feasibility study was to determine the required facilities, costs, and other impacts of food waste co-digestion and whether the benefits from increased biogas production and cogeneration power generation are sufficient to cover the implementation costs of a co-digestion program. A summary of the findings from the feasibility study is provided below: The capacity assessment determined that the OWTP has sufficient capacity in all their processes to handle the increased loads, except when one digester is out of service. In that instance, the City could divert a portion of the food waste to the Agromin composting facility rather than building an additional digester. The capacity assessment also found that, with food waste co-digestion, the OWTP would approximately double its biogas production. -The condition assessment found that the City has already made or plans to make many of the improvements identified in the condition assessment. Most notably, the City plans to refurbish a digester which is currently out of service. -This feasibility study evaluated a wide range of technologies for pre-treatment of source separated food waste to produce a bioslurry suitable for co-digestion. Three alternatives were selected for a more detailed life-cycle cost, site layout, and non-financial evaluation. A hammer-mill at the Del Norte MRF with additional polishing with a sludge screen at the OWTP was the preferred technology selected for this study (see Figure 3 for a process schematic). -The co-digestion program alternative was evaluated against a baseline alternative, whereby the City continues their current operations. The City's food waste is currently managed by a third party which composts it at the Agromin composting facility. -The hourly energy analysis allowed the City to accurately estimate energy savings from increased biogas production from food waste co-digestion by taking into account fluctuations in biogas production as well as varying electricity usage charges during the winter and summer and during on-peak and off-peak hours. -The energy analysis found that food waste co-digestion would increase cogeneration power generation by 79 percent compared to the baseline alternative. However, the net plant power usage for the co-digestion alternative is only 23 percent lower than the baseline when accounting for additional power loads for food waste processing. -The results from the energy analysis were fed into the cost/benefit analysis which consisted of a 20-year life-cycle cost analysis including capital and O&M costs to compare the baseline and co-digestion alternatives (see Figure 4 for cost results). The analyses found that based on the unit cost assumptions made, the co-digestion alternative is more costly both in capital and O&M costs compared to the baseline, even when accounting for the increased biogas production and cogeneration power generation of the co-digestion alternative. -The analysis identified that one of the major O&M costs is the cost for food waste slurry hauling from the MRF to the OWTP. A sensitivity analysis indicated that the hauling cost can greatly impact the affordability of food waste co-digestion compared to the baseline scenario. In conclusion, this bench scale study and feasibility study found that, while the City of Oxnard has sufficient capacity for food waste co-digestion, the co-digestion alternative is more costly compared to the status quo of continued composting of the City's food waste. These results are likely due to the fact that the biogas is used for cogeneration and to the high hauling costs assumed in this study. While the results are specific to the City of Oxnard, the approach taken in this project of combining feasibility studies with bench-scale studies can serve as an example for other WRRFs. This project demonstrated how WRRFs interested in implementing food waste co-digestion can use cost-effective bench scale studies to gain confidence in the techno-economic evaluation of full-scale food waste co-digestion.

INTRODUCTION The City of Tallahassee developed a biogas and energy optimization plan for its Thomas P. Smith Water Reclamation Facility (TPS WRF). The goals of this plan included optimizing imports of organic wastes to anaerobic digesters and maximizing biogas energy use in a way that is operationally sensible, economically beneficial, and promotes sustainability. The cornerstone of this plan was the development of a Solids and Energy Flow Model a tool that dynamically and holistically tracks flows of solids and energy in its various forms throughout the TPS WRF. Using this methodology, a multi-phased improvement plan was developed to address immediate issues with biogas blowers and improve short term biogas utilization rates, while also laying out a long-term path for a more sustainable future. The identified improvements included: -Replacing existing digester blowers to allow short term use of biogas in onsite thermal dryers. -Implementation of new FOG receiving with feeds to individual digesters. -Implementation of Renewable Natural Gas (RNG) to fuel City owned vehicles. BIOGAS BLOWERS TO FUEL THERMAL DRYER A previous plant upgrade had installed new digesters and a new rotary drum thermal dryer. Biogas blowers intended to be used to fuel the dryer failed during this project's startup and were never fully put into service. Recurring failures in the blower seals were observed within weeks of operation. Due to these failures the system was never started up on biogas and the dryer has been run on natural gas. Detailed investigations into the blower failures revealed that moisture buildup due to the specific blower location and elevation were the cause of recurring failures. Blowers were located in close proximity to the raw biogas draw off from digesters, leaving little pipe length to cool gas and remove condensate (Figure 6). Blower suction elevations were also located at the low point in the piping system which exacerbated the buildup of condensate in the blowers. Improvements included reconfiguring biogas piping to include moisture knockouts while installing new blowers with higher suction elevations (Figure 10). This upgrade will allow biogas to be used in the dryer as intended saving significant amounts of natural gas use (Figure 9) in a short-term timeline. This project was designed and is currently in the construction phase. During design it was discovered that the rotary drum dryer controls were never officially configured to use biogas. The Design Team worked with the dryer manufacturer to devise comprehensive and unified control strategies for the entire biogas system including coordinating dryer firing rates based on digester dome pressure. NEW FOG RECEIVING AND RNG The longer-term improvements identified included upgrades to the FOG receiving and sludge pumping systems as well as the implementation of RNG. Currently the plant receives FOG and septage in a single receiving station. Staff reported O&M issues with this station being undersized and having long piping runs to connect to the Blended Sludge Tank for distribution to digesters (Figure 3). An item identified during investigations was that FOG is currently blended with sludge in the Blended Sludge Tank (Figure 11) making it impossible to segregate FOG to individual digesters. This is important because the plan called for segregating FOG feed to individual digesters to maintain D3 RIN classification for a portion of the biogas directed to a future RNG system. The plan included a new trucked waste receiving station dedicated only to FOG. This new station would be located in closer proximity to the digesters and would provide individual feed pumps to send FOG to individual digesters (Figure 13). It was determined that Digester #3 that is currently being rehabbed could accept all the existing FOG loads received while leaving the remaining 3 plant digesters 'untainted' by FOG and able to produce D3 RINs. The plan called for specific enhancements to Digester #3 feed piping and pumping allow this unit to become the 'FOG heavy' digester. RNG was targeted as the long-term biogas utilization strategy at the TPS WRF due to several beneficial circumstances. First is the fact that the City of Tallahassee owns the natural gas local distribution utility pipeline. City NG pipeline staff have expressed high interest and willingness to facilitate a pipeline interconnection with the TPS WRF at a reasonable cost and terms while avoiding lengthy negotiations with 3rd party pipeline operators. The second is that the City already owns and operates a CNG sanitation fleet, giving the project a captive vehicle user for the RNG again without the need to negotiate terms with a 3rd party. The plan examined projected RNG production rates and compared them to the City fleet fuel use in Diesel Gallon Equivalents (DGE) per day. The fleet was found to have a steady consumption rate on a weekly and yearly basis that approximately matched the production of the proposed RNG system. With the benefits of these City owned partner utilities the RNG project was found to have significant long-term economic and sustainability benefits over using the biogas in the thermal dryer. CONCLUSION The plan provided Tallahassee with both immediate action items for improving their biogas system while laying the foundation for a more sustainable future. The biogas blowers to fuel the dryer could be implemented on a short timeline (~1 year) at a small cost (~$1 million) and would save an estimated 60,000 mmbtu/year of NG use at a savings of $570,000/year. This project is already in construction to provide short term benefits and operational flexibility while the larger and long-term projects for FOG receiving and RNG production are being developed.

Introduction Sludge generated from wastewater treatment typically goes through a series of handling processes such as thickening, stabilization and dewatering, before its final use or disposal. Anaerobic digestion is widely applied in medium to large water resource recovery facilities (WRRFs) for sludge stabilization. In anaerobic sludge treatment, fugitive methane emissions can occur from digesters (due to aging infrastructure), downstream storage, from associated pressure relief valves and pipework, and also due to methane slip through combined heat and power (CHP) engines and biogas upgrading. For example, work in Denmark over the past few years has quantified methane emissions at 69 biogas facilities and shows methane emissions account for up to 7.5 percent of the gas production at WRRFs (Fredenslund, A.M et al., 2021; Scheutz & Fredebslund, 2019). Large leakage of methane may negate the positive climate impact from biogas energy recovery and contribute significantly to the facility's operational carbon footprint. A portion of the methane generated is dissolved in the digestate, which can also be released during the downstream dewatering or sidestream treatment processes. In addition, long-term sludge drying (e.g., in lagoons) is commonly applied in many countries, such as Australia, due to its ease of operation and low operational costs. Methane generated from sludge drying lagoons is typically not captured and can be a significant greenhouse gas (GHG) emission source. In the US, a country-wide standard methodology for quantifying GHG emissions from the wastewater sector does not exist. Among the available reporting protocols, methodologies for quantifying fugitive methane emissions from sludge treatment and biogas handling are limited to combustion of biomass and biogas, which essentially assumes zero methane emissions from anaerobic digestion and biosolids dewatering processes. The latest Biosolids Emissions Assessment Model (BEAM 2022) has recommended a minimum of 1 percent of methane in biogas as fugitive emission and allows a user-input value if site-specific data are available. The lack of consistent methodology and lack of facility level measurement result in significant risk to facilities in the estimation of their fugitive methane emissions through the sludge treatment and biogas handling processes. This paper presents an overview of challenges and issues in quantifying fugitive methane emissions from sludge treatment and biogas handling, impacts on GHG inventory and practical tips for reducing methane emissions based on global experience to date across a growing number of case studies. Benchmarking Fugitive Methane Emissions Methodologies and Key Considerations In the 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories, a three-tier method is described for quantification of methane emissions from WRRFs. Tier 1 provides global activity and emission factors; Tier 2 provides for local in-country activity factors and/or emission factors and Tier 3 methods require facility level monitoring. Accurately quantifying fugitive methane emissions requires Tier 3 facility level measurement using methods such as differential absorption lidar (DIAL), tracer gas dispersion (TDM) and inverse dispersion modelling (IDM), which may be combined with point source leak detection or other process unit methods to determine location of leaks. This practice remains emerging with significant work ongoing in Europe to provide facility level quantification and mitigation at WRRFs. Elsewhere, Tier 2 methods are common. The UK Carbon Accounting Workbook is used by Utilities to report on operational emissions and includes country-specific (Tier 2) theoretical emission factors associated with the most common sludge and biosolids processes in the UK, with emissions based on mass of methane per unit of tonnes dry solids of raw sewage sludge (UKWIR, 2020). In the Australian National Greenhouse and Energy Reporting (NGER) framework, methane process emissions are indirectly estimated using sampled influent and/or effluent streams and application of assumed biogas generation and percentage biogas utilization to calculate the net tonnes of CO2 equivalent released to the atmosphere. This approach considers facility level data but does not require direct measurement of the GHG, hence still considered Tier 2. Emissions from biogas flaring is based on best practice flow rate measurements of the flared biogas and its methane concentration. Different facilities may have a range of approaches to sampling process streams for operational, planning or reporting requirements. Sampling locations, frequencies and methodologies can result in inaccuracies in estimating the fugitive methane emissions. The recently published IWA book 'Quantification and Modelling of Fugitive Greenhouse Gas Emissions from Urban Water Systems' includes additional information on fugitive methane emissions from a range of wastewater treatment, sludge and biogas handling processes, estimated through facility level monitoring (IWA, 2022). Table 1 provides a summary of key methane emissions from global case studies including both those which directly monitor methane emissions and those which use various alternative GHG accounting methodologies, generally aligned with Tier 2 level approaches. A more complete table will be provided in the full paper. In the absence of global full scale monitoring data to estimate fugitive methane emissions, existing methodology estimates may be beneficial for benchmarking emissions from sludge treatment and biogas handling processes however, Tier 3 level facility monitoring is required to accurately estimate methane emissions and to validate any mitigation efforts. Monitoring and Reducing Fugitive Methane Emissions Whilst published literature studies of methane mitigation are limited, practical examples of programs for monitoring and mitigation across European countries show the criticality of direct methane emissions monitoring, and operational approaches to mitigate methane emissions through regular survey, proactive leak detection and repair and independent certification. Table 2 summarizes some of the key sources and (limited) mitigation approaches from work to date; further details to be provided in the full paper. In future planning, it is critical that decisions regarding anaerobic versus aerobic sludge digestion consider fugitive emissions from existing and proposed assets. Conclusions Fugitive methane emissions from sludge treatment and biogas handling processes are a significant source of GHG emissions which must be monitored and mitigated by utilities taking action to reduce their carbon footprint. These emissions are particularly critical for WRRFs with anaerobic digestion and open anaerobic systems such as sludge drying ponds. There is lack of consistent methodology for quantifying and monitoring these emissions in North America, which could lead to over- or (more likely) underestimation of their contributions to the overall GHG footprint for the WRRFs. As shown by ongoing work in Europe, facility level measurement is critical in quantifying the fugitive methane emissions. This paper will provide practical recommendations to WRRF operators to guide best practices for methane monitoring and mitigation throughout the facility life cycle.

Throughout the United States, over 1,500 wastewater treatment plants (WWTP) are equipped with anaerobic digestion to stabilize sewage sludge into biosolids. In those facilities, the byproduct of digestion is biogas, a methane rich gas that has the potential to be used as a renewable energy source. Only a fraction of the WWTPs however utilize their biogas for renewable energy, outside of being used in boilers for process heating. If biogas is upgraded to biomethane, the gas is equivalent in quality to natural gas, only from a renewable source, then it is termed Renewable Natural Gas (RNG). Due to the environmental benefit of RNG, through GHG emission reductions and offsetting of fossil fuel natural gas, the value of RNG exceeds its energy value. With this in mind, Bartlett & West teamed up with the Oakland WWTP in Topeka, KS to develop a project for upgrading their biogas to RNG. The project was funded in 2018 and fully commissioned in 2022. This presentation will outline the process details along with design considerations and performance of the design. The treatment train consists of bulk desulfurization, biogas drying and boosting, activated carbon system, compressor and 3 stage membrane carbon dioxide removal. Construction, balance of plant requirements, and the injection station interface are important factors to consider and design around. The presentation will also focus on the economics, not only on a monetary but also the environmental benefit. The capital and operating expenses are apart of the overall proforma. And the final section will cover the lessons learned throughout the 4 year journey to completion.

Overview: Formed in 1954, East Valley Water District (EVWD) provides water and wastewater services for a population of more than 100,000 across 18,000 acres in the City of Highland and portions of the City and County of San Bernardino County, CA. EVWD initiated greenfield development of the Sterling Natural Resource Center (SNRC) to provide water recycling for groundwater recharge and enhance their core mission of water production. SNRC enables EVWD to provide in-house wastewater services to ratepayers, rather than relying on neighboring agencies. SNRC was envisioned with the ultimate goal to provide community resilience through utility reliability, resource recovery, economic development, and educational partnerships. SNRC takes a holistic approach to waste recovery, providing water recycling to replenish the Bunker Hill groundwater basin, leveraging biogas from anaerobic digestion to support plant energy needs, and converting solids to Class A soil amendment. The 2.2-acre eastern portion of SNRC houses state-of-the-art process equipment, and the western lot was developed to feature a new District headquarters, community center, and public green space. EVWD partners with community organizations to host events and activities, including educational and vocational initiatives. Following October 2018 groundbreaking, construction was completed in early 2022, and commissioning is ongoing. Operations are to begin in early 2023. EVWD worked closely with stakeholders to maintain construction progress through the pandemic. Approach to Resource Recovery: The greenfield 8 MGD wastewater resource recovery facility (WRRF) is designed to provide complete resource recovery, beyond the scope of traditional wastewater treatment. Ultimately, all wastewater entering the plant is turned into beneficial products supporting facility operations and the broader community. -Wastewater: SNRC treats up to 8 MGD wastewater, using a Fibracast membrane bioreactor (MBR) with FibrePlate membranes. Recycled water is injected underground to replenish the Bunker Hill Groundwater Basin, which serves as water supply for EVWD and neighboring communities, and improve drought-resistance. -Biosolids: Solids remaining after anaerobic digestion (AD) via Anaergia's OmnivoreTM high-solids digestion technology are transported to the nearby Anaergia Rialto Bioenergy Facility (RBF) (approximately 10 miles away) for thermal processing via pyrolysis to carbon- and nutrient-rich Class A soil amendment for agricultural use in Southern California. Nutrients: Sidestream treatment is provided by Anaergia's AMR system to recover nitrogen for use in commercial fertilizer (as discussed further below) and recycle nutrients back to regional agriculture. - Energy: Biogas produced from anaerobic digestion fuels 3MW of combined heat and power (CHP) systems to create renewable energy to meet plant power and thermal demands. In addition to self-sufficiency, this improves reliability of operations and reduces operating costs and therefore burden on ratepayers. -High-strength waste (HSW): SNRC receives up to 130,000 gallons per day of landfill-diverted HSW for co-digestion with wastewater biosolids. This supports methane emissions reductions from landfill, compliance with state organics recycling mandates, and enhances biogas production to support SNRC energy-neutrality. Tip fees collected offset operating costs at SNRC and support rate stabilization. Key Technologies: SNRC employs leading edge technologies from Anaergia and Fibracast to achieve resilient, self-sufficient operations with minimal residuals. -Fibracast MBR: Water is recycled using a MBR with FibrePlate membranes so that it may be used for groundwater recharge. These proprietary membranes combine the best advantages of hollow-fiber and flat sheet MBR systems, using aeration and mixed liquor cross filtration to continuously clean the membranes during operation. The membrane's high packing density, low trans-membrane pressure, and advanced automation leads to easy and reliable plant operations. -Anaergia Omnivore high-solids digestion: Omnivore was employed to cost-effectively provide the digester capacity required to process wastewater biosolids and HSW and generate biogas for energy neutrality. Omnivore uses Anaergia proprietary OmniMix high-solids mixing system together with robust thickening technology to increase the solids ratio in digesters, allowing for triple the feed capacity of a traditional digester, reduced footprint, and reduced and capital expense. This was particularly important at SNRC given space constraints. Anaergia screw presses are employed to pre-thicken digester feeds, which also reduces heat demand associated with heating excess liquid within the digester. Anaergia OmniMix mixers ensure the thickened digestate, including high-solids HSW, is adequately mixed to support tank turnover, digester health, and VSR. OmniMix mixers provide improved energy efficiency versus traditional mixing systems. Overall, Omnivore provides SNRC with reduced energy demand while supporting increased biogas production, advancing achievement of energy-neutrality. -Anaergia AMR sidestream treatment: After digestion, digestate is dewatered via Anaergia screw presses to 25% TS. The filtrate is processes via Anaergia AMR to recover up to 90% of nitrogen as ammonia, creating ammonium sulfate (AMS) fertilizer. AMR operations use heat generated via biogas CHP. Following sidestream treatment, filtrate is also treated via MBR for groundwater recharge. Strategic Partnerships: SNRC was conceived of primarily as a community resource beyond essential water and wastewater services. SNRC supports community and economic development by providing valuable resources for residents and strategic partnerships. -Workforce Development: SNRC resulted in creation of numerous permanent, full-time Greentech jobs within the District service area. Leveraging the new public spaces built as part of the project, EVWD intends to host community events, including educational events focused on SNRC capabilities to enhance engagement and sense of ownership. As SNRC is located across the street from Indian Springs High School, EVWD has launched a Water and Resource Recovery Career Pathway in partnership with San Bernardino City Unified School District. This program offers courses that highlight opportunities in the resource recovery sector and facilitate industry leaders sharing technical and personal stories to community members at no cost. A similar program has been established with San Bernardino Valley College. SNRC also house the Water Education Learning Lab (WELL) Program to provide readily-accessible hands-on experiences and training. Rialto Bioenergy Facility: Dewatered biosolids generated at SNRC will be transported approximately 10 miles to Anaergia's RBF, where they will be dried and pyrolyzed. The resulting Class A product is carbon- and nutrient-rich, and free of PFAS and other contaminants of emerging concern (CECs) such as microplastics and pharmaceuticals. This process allows both nutrients and energy from biosolids to be recovered and beneficially reused. Further, this partnership provides EVWD with a reliable and environmentally friendly guaranteed biosolids management outlet, compliant with California SB1383 regulations, which limit landfill disposal of organics such as biosolids. By establishing agreements within the region, vehicle miles and emissions associated with biosolids hauling are also significantly reduced. Anaergia Nutrients: EVWD and Anaergia once again teamed to develop the Anaergia Nutrients facility at an underutilized District property, approximately two miles from SNRC. The facility will blend Class A soil amendment produced at RBF with AMS recovered at SNRC to create a marketable carbon-negative commercial fertilizer. The user-friendly material can be readily substituted for more costly conventional fertilizers. As a result, two resources often treated as residuals are instead converted to a valuable product helping to close the loop on nutrient recovery and create ancillary benefits and improve profitability for California farmers. EVWD and its ratepayers directly benefit from enhanced property use, lease payments, and host fees. Waste Generators & Haulers: SNRC provides a reliable alternative HSOW disposal option that meets state organics diversion requirements that is also good for business. Rather than travel to landfill, waste haulers reduce vehicle miles and emissions by disposing of waste at SNRC and reduced trip time translates to more business. The mutual benefits mean robust and consistent feedstock source to SNRC for onsite renewable energy generation. SNRC is the result of a visionary mission for EVWD. It provides the new model for stewardship of scarce public resources while enhancing quality of life and economic growth.

Introduction Biofiltration is a term in the odor control industry used to define a vapor phase odor control technology category that focuses on the ability of microorganisms to remove nuisance odors from a foul smelling airstream. Biofiltration, biofilters, have been around for decades. It was Pomeroy in 1957 that constructed one of the first open pits filled with porous soil and perforated pipes for air distribution to treat wastewater odors. Systems evolved from those first porous soil biofilters to include bark and wood chips as support media to reduce compaction and enhance air movement in Europe in the 1970's. With rapid progression in the 1980's and 1990's in Europe, the technology began to slowly become accepted and used in North America as the previous black box approach turned more toward a science based effort. Today's biofilters include a range of medias (soil, bark, wood chips, compost, extruded wood, glass, proprietary, etc.) and styles (in ground, open, hybrid, modular, closed, etc.) that still all rely on the founding principle of biofiltration the ability of microorganisms to mitigate odors! For a plant (see Figure 1) in coastal central New Jersey, TRWRA, the application of an in ground, wood chip and compost open biofilter had been accepted years ago and treated plant odors associated with their solids processing/handling building (sludge thickening room, sludge dewatering room, and truck loading room), and two sludge storage tanks. The biofilter mitigated nuisance odors but the unit took up quite a bit of plant real estate as it was treating 19,600 cfm of odorous air, was more maintenance intensive then they envisioned, and the media was replaced every five years, which was a major event. With an upcoming plant upgrade, space was at a premium and the biofilter was evaluated to see if it could be modified, moved, or replaced. Satisfied with biofilter technology, the plant was willing to keep the technology but uncertain how to fit it and make it work. This paper will discuss the odor control evaluation conducted and how the plant got to keep the biofiltration technology but delivered in a new form. Project Statement The existing odor control system for the Solids Handling Building (SHB) and Sludge Storage Tanks (SSTs) consisted of an in-ground, constructed-in-place, wood chip media biofilter. The Two Rivers Water Reclamation Authority (TRWRA) indicated that the biofilter required increased maintenance to ensure satisfactory performance and that the media was nearing the end of its useful life and needed to be replaced prior to the evaluation. In addition, a new Main Pump Station (MPS) at the plant was in the planning phase and with no other available space, TRWRA management made the decision to use land currently occupied by the biofilter. As a result, an evaluation was conducted that focused on newer biofilter technology using a synthetic, proprietary media that significantly reduced the overall size of the biofilter and provided a guaranteed 15 year life for the media. The new standalone biofilter would treat the same odorous airflow from the SHB and SSTs. and provided a significant increase in odor treatment capabilities as compared to the existing biofilter. Based on the significantly reduced size it could be located adjacent to the existing SHB. As an added benefit the new biofilter was constructed and placed into service prior to the beginning of construction of the MPS to avoid unnecessary sunk cost for providing a temporary odor control system as well as related construction time delays. Evaluation Before considering either alternate technologies or biofilter systems, odor monitoring was conducted at the site to determine the odor characteristics of the various odor sources in order to share with the vendors. Continuous hydrogen sulfide, Hâ‚‚S, was monitored with data loggers (results presented in Table 1), grab air samples were collected and sent to an independent laboratory to analyze for reduced sulfur compounds (results presented in Table 2), differential pressure continuous monitors were placed in the SSTs to assess whether they were under negative pressure thereby containing the odors, and smoke tests were run to determine if any localized leaks were present on the SSTs. Conclusions Several biofilter vendors were contacted and provided the data collected at the plant. Simply replacing in kind was not an option for many reasons including size and the fact that organic media breaks down in the presence of the sulfuric acid byproduct, which affects media stability, air transmittance and treatment performance. The recommended odor control system consisted of two constructed-in-place concrete biofilter cells with covers containing engineered synthetic and proprietary media. The engineered synthetic media has several advantages over the original organic media it was replacing with respect to media life, treatment efficiency, pressure drop, media depth, and required footprint. These advantages led to a more sustainable system where less water, less pressure drop, less power, less maintenance, longer media life (minimally three times longer), and a stack discharge with higher velocity rather than an area-wide, low velocity, ground level discharge. Despite Covid-19 related supply chain issues with FRP duct work during construction, the system is permitted, operating, and meeting performance. TRWRA and the neighbors are happy!

The mining of non-renewable phosphate rock is currently the primary phosphorus source for food production. Phosphorus recovery from secondary wastes is a key component for circular economy. Municipal digested anaerobic sludge, or digestate, is a liquid-solid mixed liquor produced from anaerobic digestion that is enriched with phosphorus (P). Around 40% of the phosphorus discharged by anthropogenic activity will end up in the wastewater sludge, making digestate a promising phosphorus source. Conventional method for phosphorus recovery from the digestate like struvite precipitation is practically challenging. One of the main reasons is the heavy chemical consumption and the high risk of handling corrosive acid/base. Electrochemical methods are of strong research interest lately due to the elimination of chemical use, flexible process control, and low environmental impact. In this study, we designed an electrochemical nutrient recovery cell (ENRC, Fig. 1) to achieve simultaneous phosphorus release and nutrient recovery from the digestate. The digestate was sampled from Missouri River Treatment Plant in late September of 2021. Most phosphorus exists in the solid fraction of the digestate and need to be firstly released into the aqueous phase, usually by lowering the pH, before the recovery. As shown in Fig.1, water electrolysis reaction will induce the acidification of the digestate and increase aqueous PO43- concentration in the anode. Meanwhile, electric field will drive NH4+ to migrate across the cation exchange membrane (CEM) into the recovery chamber. Results show the digestate was acidified from pH 8.0 to 2.0 in the anode of the ENRC after operating for 5 h under the current density of 25 A m-2, similar to the pH adjusted by the conventional HCl adjustment method. Both methods released 67.6~74.1% of total phosphorus in the digestate and achieved the comparable PO43--P concentrations of 253.47 ± 3.05 mg L-1 and 277.60 ± 15.2 mg L-1 (p-value > 0.05), rising from 27.72 ± 0.95 mg L-1 in the untreated digestate (Fig. 2). In contrast to the high NH4+-N concentration of 995.07 ± 53.11 mg L-1 in the HCl treated digestate, electrochemical leaching removed >99% of NH4+-N from the digestate (Fig. 2). The HCl adjustment increased Ca2+ concentration from ~89 mg L-1 to 479 mg L-1, much higher than 31 mg L-1 Ca2+ in the ENRC anode effluent, likely due to Ca2+ migration through CEM into the recovery chamber. The HCl treatment introduced a high concentration of Cl- (~4700 mg L-1), which was avoided in the ENRC anode effluent that had ~120 mg L-1 Cl- (Fig. 2). The nutrients were successfully recovered in the ENRC recovery chamber after continuous operation for 5 cycles. As shown in Fig. 3A, the ENRC released 147.59~215.24 mg L-1 PO43--P from the digestate at the end of each cycle, accounting for 40~58% of total phosphorus in the digestate. The catholyte removed 96-98% of the PO43--P and produced an effluent with < 5 mg PO43--P L-1. The PO43--P concentration in the recovery solution reached 142.62 ± 7.78 mg L-1 after the first cycle and gradually accumulated to 404.56 ± 20.44 mg L-1 after 5 cycles, which accounted for 72% of the total PO43--P released in the anode. Mass balance revealed that after removing the recovery solution, 6.9% of the released PO43--P remained or adsorbed in the recovery chamber (Fig. 3B). In addition, 9.8 % of the released PO43--P precipitated in the cathode chamber due to the high pH environment. The NH4+-N concentration in the recovery solution linearly increased to 3493.56 ± 194.13 mg L-1 h-1 after five cycles of operation (Fig. 3A), accounting for ~90% of the total NH4+-N in the digestate. After adjusting the pH to 8.5 in the final recovery solution, more than 99% of the PO43--P was precipitated to produce a solid with light brownish color. The inorganic contents in Fig. 3C shows that PO43--P contributed to ~13.62% of dry mass in the product, which was equivalent to 31.19% P2O5 content and would meet the 25%~37% P2O5 requirement for economic grade phosphate rock. Calcium was the major metal and took up ~16.54% of the dry weight in the product, indicating a good soil phosphorus availability. After the nutrient extraction, around 42% of the dissolved COD was removed and the digestate settleability was significantly improved. This work has demonstrated an effective electrochemical approach to extract nutrients from the waste digestate and can be extended to treat phosphorus-rich biosolid wastes generated from different sectors. This work has been published: Wang, Z. and He, Z.* (2022) Electrochemical phosphorus leaching from digested anaerobic sludge and subsequent nutrient recovery. Water Research. Vol 223, Article 118996.

Charlotte Water (CLTWater) has 123 MGD of capacity between five major wastewater treatment plants (WWTPs) and is interested in sustainable and cost-effective technologies that may be selected for future WWTP expansions or for replacement of existing treatment infrastructure. Aerobic granular sludge (AGS) is an innovative secondary wastewater treatment technology that can achieve biological nutrient removal (BNR). Aqua-Aerobic Systems, Inc (AASI) is the vendor for AquaNereda, the patented AGS system that utilizes specific biological and hydraulic selection pressures to produce and maintain the AGS in a sequencing batch reactor (SBR). CLTWater elected to pilot AquaNereda to understand how it might be used to expand the capacity of our overall system, either at an existing plant or in place of another BNR technology at our new plant under design, the Stowe Regional Water Resource Recovery Facility (SRWRRF). An AGS pilot was performed at McDowell Creek WWTP from June 2019 to February 2020 to determine its viability as a treatment for CLTWater. Before starting the AquaNereda pilot, CLTWater developed a list of objectives to achieve during the piloting process with actionable and achievable goals defined for each objective. These objectives included 1. Evaluating simulated performance representing treatment with and without primary clarifiers 2. Observing development of granules from flocculant sludge 3. Evaluating solids characteristics 4. Evaluating process control and operability 5.Involving State regulatory agencies to facilitate potential future permitting processes To address the objective of evaluating solids characteristics, a separate solids study was conducted at Bucknell University to provide insight on solids handling and treatment impacts for potential full-scale Nereda implantation. CLTWater wanted to assess impacts to digestion performance, dewatering, and recycle streams when aerobic granular sludge (AGS) and conventional activated sludge (CAS) are treated concurrently. During the study, Bucknell operated four lab-scale digesters that were fed several solids blends (Table 1) including two 100% thickened waste activated sludge (WAS) digesters to demonstrate differences between AGS and CAS WAS and two 60% primary sludge (PS)/40% WAS digesters to simulate McDowell's current digestion process and the expected maximum contribution of AGS to any digestion process at CLTWater. Waste solids from the Nereda pilot reactor treating primary effluent were thickened to ‰¥5% using gravity belt thickening and shipped to Bucknell with thickened PS and CAS-WAS from McDowell's full scale processes. Bench-scale 20-day HRT mesophilic anaerobic digesters were fed daily. Biogas production was monitored throughout the trial, but other analyses were performed after 71 days (~3.5 SRTs) to ensure results were representative of steady-state conditions. Results include quantified metrics and other observations related to 1) digester performance VS destruction, biogas production; 2) solids handling sludge viscosity, polymer demand, cake solids, cake metals content and odor production; and 3) recycle streams digestate nutrient concentrations. For digester performance, results showed that volatile solids reduction (VSR) for AGS-WAS was comparable to CAS-WAS with slightly different methane yields between Digesters 3 and 4 (60% PS/40% WAS). Minor differences in solids handling parameters were observed including marginally higher viscosity and polymer demand for digested solids that included AGS, but these differences were more pronounced in the digestate from Digesters 1 and 2 (100% WAS). Recycle stream soluble TKN concentrations were similar regardless of WAS source; however, recycle streams from reactors including AGS-WAS were characterized by markedly lower soluble TP concentration. The finding of much lower soluble TP concentration for AGS-WAS was surprising given that the Nereda process includes enhanced biological phosphorus removal (EBPR) and the pilot reactor performed comparable EBPR as the full-scale mainstream conventional BNR process. Unfortunately, the pilot timeline did not allow for additional investigation into the cause of this observation, but further research may be warranted in this area. This presentation will discuss high-level results from each of the objectives targeted during the AquaNereda pilot but will focus mainly on the solids-related findings. We will present overall conclusions from the pilot as well as lessons learned related to implementing a pilot for a process that has broad reaching implications across a wastewater treatment plant. Finally, the future of AGS implementation at CLTWater will be discussed.

Industrial activities have created many brownfields throughout the Chicago metropolitan area. Brownfields are generally associated with poor soil health, inferior nutrient cycling, and attenuated soil ecosystem services, as demonstrated in low primary production and carbon (C) sequestration, low diversity of soil biota and plants, and high runoff with impaired water quality. Thus, restoration of brownfield sites not only increases the economic value of the sites, but also increases the ecosystem services the land provides. A research and demonstration site for brownfield restoration was established on Metropolitan Water Reclamation District of Greater Chicago (MWRD) land along the Chicago Sanitary and Ship Canal, which has been classified as a brownfield site due to prior use of the site for storage of petroleum and chemicals and destruction of soil horizons. Due to their physical, chemical, and biological properties, biosolids, which contain high amounts of organic matter, are an ideal soil amendment for degraded and contaminated soils. In addition to C and nutrients, biosolids contribute to an active microbial community, which is a critical component of soil ecosystem function, including nutrient cycling, C sequestration, plant symbiosis, and contaminant degradation. Research plots were established in October-November 2021 using Split Plot design with four replications. The main treatments were 1) control (no amendments to the existing soil), 2) air-dried biosolids at one-half rate (air-dried biosolids applied at 2.5 cm depth or 130 Mg ha-1), 3) air-dried biosolids (air-dried biosolids applied at 5 cm or 260 Mg ha-1), 4) composted biosolids (woodchips composted with biosolids-3:1 at 5 cm depth or 185 Mg ha-1), and 5) a blend of biochar and air-dried biosolids (pyrolyzed biosolids at 1.25 cm depth and air-dried biosolids at 3.75 cm depth or 105 Mg ha-1 pyrolyzed biosolids mixed with 195 Mg ha-1 air-dried biosolids). For the same thickness (5 cm) of soil amendment applied, the loading rate in weight basis was lower in composted than air-dried biosolids due to the lower bulk density for composted biosolids. Since composted biosolids contained more organic C (25.8%) than air-dried biosolids (19.8%) by mass, the C input from the two amendments applied in 5-cm treatments were comparable. The biochar/air-dried biosolids blend also leads to a similar C input to the 5 cm air-dried biosolids treatment, as biochar contained 21.5% of organic C, just slightly higher than that for air-dried biosolids. Subtreatments are two prairie plant communities with C4 grasses for subtreatment 1 and C3 grasses and forbs for subtreatment 2. The subplot size was 4.5 m x 5 m. The plots were hydro-seeded with native plants in November 2021. Additional seeding by drilling is still needed due to the poor germination during the first year, which is common for establishing native plants. This report will focus on assessing the impacts of biosolids on soil health in degraded urban soil, which supports plant establishment. We sampled soil in April 2022 at 010 cm depth and analyzed the key parameters for soil health, including soil organic C (SOC), nitrogen (N) mineralization potential (NMP), microbial basal respiration, microbial biomass C (MBC), and water-holding capacity (WHC). Due to the high gravel content of the brownfield soil, all results except for soil WHC are presented as 'stock' in 010 cm soil depth by using bulk density of soil materials (< 2mm). Results for two subtreatments within a main plot are pooled for this report of the soil measurement. All soil amendments drastically increased soil WHC from 53% to 100121% (dry soil weight basis), which is associated with the increase in SOC (Table 1). Soil organic C in the control plots had a mean of 17.4 kg ha-1 in the top 10 cm (Table 1) with a range of 10.026.0 kg ha-1). The C-rich soil amendments considerably increased SOC, leading to higher than 30 kg ha-1 in soil for all four amendments. Microbial biomass C measurement indicated that microbial populations were more abundant in plots with the soil amendments than the control: however, it varied depending on the amendment type (Table 1). Microbial biomass C was highest under the air-dried biosolids, followed by air-dried biosolids at one-half rate, composted biosolids, and the biochar-biosolids blend, and lowest in the unamended control soil. Microbial respiration, the CO2 output of the microbial community, reflects microbial quantity and activities and the utilization of substrates by microbes. We found that the soil microbial basal respiration in the control plots was low relative to the treatment plots (Table 1). The high biosolids rate had a higher basal respiration rate than the other treatments. The microbial metabolic quotient (qCO2), the respiration rate per day per unit microbial biomass, helps us understand the environmental stress level for microbes in the soil. High qCO2 indicates greater environmental stress for soil microbial communities. The full rate of air-dried biosolids reduced the qCO2 compared to the control, though the other soil amendment treatments had a similar qCO2 to the control (Fig. 1), indicating that air-dried biosolids can provide a less stressful habitat for microbial communities. Nitrogen mineralizing potential is important for evaluating N accessibility to soil microorganisms and plants. For the sampling period, approximately six months after plot establishment, control plots reflecting the degraded conditions of the site had a very low NMP of only 0.01 kg ha-1, compared to a range of 2.584.2 kg ha-1 in the treatment plots (Table 1). All three treatments that received air-dried biosolids had a higher NMP than composted biosolids. The results presented here showed that the use of biosolids as a soil amendment gave rise to significant improvement in the health of degraded urban soil, which will facilitate plant establishment and possibly drive interactions among microorganisms, plants, and soil components for restoring ecosystem services of the brownfield.

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.