Conference Papers

There are numerous challenges faced by the biosolids management industry throughout the United States, notably the elimination of land application in the State of Maine. In Florida, the reduction of land application sites due to the Clean Waterways Act of 2020 was a significant step towards a more rigorous approach to ensuring that biosolids do not contribute to water quality concerns throughout the state. Legislative proposals continue to emerge that could further limit or eliminate land application, while the EPA's PFAS roadmap aims to target water resource recovery facilities and biosolids for controlling PFAS. Additionally, the implementation of Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) provisions poses potential impacts on utilities. Given these challenges, it is crucial for multiple stakeholders to unite and ensure the continuity of effective and established biosolids management practices. Various multistate coalitions such as the Northwest Biosolids Association, Midwest Biosolids Association, Mid-Atlantic Biosolids Association, Northeast Biosolids and Residuals Association, Virginia Biosolids Council, and the newly formed Southeast Biosolids Association along with state associations such as the California Association of Sanitation Agencies (CASA) and the Virginia Biosolids Council, aim to bridge public, private and agriculture interests for a more powerful approach to advocacy and public outreach efforts to combat legislation and regulations that threaten the sustainable use of biosolids in agriculture. Many utilities do not have a robust advocacy program and especially those within municipal and county structures which typically are battling more localized priorities. The complexity of the issues leads to many local government leaders struggling to understand and advocate effectively on the issues. Equipping utility professionals with a better understanding of the public policy process, and how they can be actively engaged in the process, will enable a higher level of input by utilities for legislation and rulemaking. Additionally, utilities can join with leading associations that can help them track the specific issues in their state, and craft response letters for them to use, rather than relying on their respective organizations to provide this support. Multiple opportunities exist for utility professionals to be engaged in the process of shaping policies. Starting with the very beginning of the process which involves introducing proposed language for consideration, or secondarily proposing amendments to bill language being considered. Finally, even after a law is passed, the rulemaking process is an opportunity to provide input. This is then followed by ratification where it has to go back to the legislature to be formally voted on and adopted. All of these points throughout the policy process can be viewed as opportunities where utilities can weigh in and use advocacy to insert their viewpoint on the issue and help to influence, change, modify or even create a new policy. The purpose with public outreach is education. However, explaining the technical concepts of utility operations to the public can be a challenging task. According to research conducted by the University of Minnesota, people only retain 50% of what they learned 8 hours after learning it. 6 months later, that number drops to 25%. When it's all said and done, 75% of what was initially learned, is not retained. Understanding this significant learning loss can help in developing strategies to overcome it. This includes using tactics to convey technical information to non-technical people and condensing information down to the top three of four issues. Additionally, EPA provides methods for effective public outreach and engagement sessions which allow for a more meaningful dialogue with the public. This presentation will expound upon the context of for which biosolids regulations and legislation is being developed and provide guidance including practical tools to help utility professionals communicate with non-technical people, such as state and federal elected officials, along with educating them on how to craft a persuasive argument will improve their ability to communicate with these groups. It will also review EPA guidelines for the development of effective public outreach events that achieve better engagement with the community.

The prevention, mitigation, and management of combined sewer overflows (CSO) continues to be a focal point for municipal wastewater utilities throughout the country. Regulatory requirements are constantly evolving and continue to increase emphasis on public alerting. Modern digital solutions can be used to improve the way that utilities notify the public about the occurrence and effect of CSOs in their communities. This presentation will provide examples of enhanced CSO prediction and notification tools that leverage predictive analytics and machine learning to improve transparency in CSO management. In the first example, an alert system was developed to inform community members of the risk of high bacteria levels downstream from CSOs. The alert tool uses publicly available information that is fed into an algorithm developed with historic data and relationships, including time of travel and decay constants, specific to the river. The tool has been validated against several overflow events and predicts downstream bacteria concentrations within a reasonable and useful accuracy. The results of the predictive tool are available on a public website hosted by the regional planning agency. Innovative tools that leverage existing engineering information are effective at informing the public about the real-time contamination risks of combined sewer overflows. The second example demonstrates how surrogate modeling using machine learning can predict collection system flows, and associated CSOs, in real time. This example also maximizes the use of existing available data and information to create a modern prediction tool. A calibrated hydraulic model of a combined collection system was used to train a machine learning model to produce predictive flows based on real-time weather forecasts. The knowledge of when, where, and how much combined sewage is predicted to be released into local waterways can be used to alert the public of impending closures and advisories. This type of tool can also be used by utility managers and operators to plan for upcoming overflows and increased inflow to wastewater treatment facilities.

Introduction The waste activated sludge (WAS) produced in Washington Suburban Sanitary Commission's (WSSC Water) Water Resource Recovery Facilities (WRRFs) is historically known to have relatively poor digestibility, even with thermal hydrolysis pretreatment (THP). In agricultural waste management, it has been a common practice to co-digest a poorly biodegradable feedstock with an easily biodegradable feedstock to improve the overall digestibility of the former (Karki et al., 2021). Since primary sludge (PS) generated in WRRFs usually possesses much better digestibility over that of the WAS, this study tested the hypothesis whether blending PS with WAS can increase the biodegradability of WAS. Because WRRFs need to use more coagulants such as alum to precipitate more PS for the blending, the impact of alum on the WAS biodegradability was also taken into consideration. Therefore, this study investigated the effects of PS:WAS blending ratio and alum doses on the WAS digestibility in a THP-anaerobic digestion system. Meanwhile, this study also tested the hypothesis that blending PS with WAS may produce more recalcitrant dissolved organic nitrogen (rDON) as a result of Maillard reaction in THP (Zhang et al., 2020). Maillard reaction occurs between the carbonyl groups of reducing sugar and the amino groups of proteins (Hodge, 1953). Since PS and WAS are mainly composed of carbohydrates and proteins, respectively, and the typical THP temperature at 165 0C is ideal for Maillard reaction, it is a reasonable prediction that more rDON may form within THP fed with PS and WAS blending than without. Materials and Methods Experimental design Dewatered WAS and PS cake samples with around 20% total solids (TS) were collected from two WRRFs of WSSC Water. Depending on the Al that came with each type of cakes, additional Al was supplemented according to the Al doses designed in Table 1. Basically, more Al was supplemented when more PS was blended to simulate the scenario when more alum was consumed for more PS production. A jar test was performed to estimate the Al dose it took to produce enough PS for the blending ratio in Table 1. Then, the PS and WAS cake samples were either individually processed in THP-anaerobic digester (AD) systems as controls or blended according to the blending ratio as summarized in Table 1 to study the blending effects during this three-phase study. All cake feedstocks were diluted to 16% TS prior to feeding into the CAMBI pilot THP system operated at 165 oC for 30 min. The THP effluent was further diluted to 9% prior to being fed into the four pilot mesophilic AD systems. These ADs were inoculated with fresh effluent sludge from a full-scale THP-fed mesophilic AD at DC Water. The steady-state digestates were analyzed for understanding the impacts of PS:WAS blending ratio and alum doses on WAS digestibility. In general, four phases of studies described in Table 1 were performed with controls to understand the effects of 1:1 blended with low Al in phase I, 1:1 Blended with high Al in phase II, and 3:1 Blended with high Al in phase III. rDON determination The four AD effluent samples from Phase II study in Table 1 were subjected to a rDON test. This test was divided into two steps including air stripping and aerobic incubation. The goal of air stripping was to reduce the total ammonia nitrogen (TAN) of the AD effluent to lower than 200 mg/L. This is because the TAN concentration is significantly greater than that of dissolved organic nitrogen (DON) and thus may overshadow the DON level readings which are calculated as the difference between soluble Kjeldahl nitrogen and TAN. The aerobic incubation aimed to remove the biodegradable DON, and in turn the remaining DON in the system can be regarded as rDON. Results WAS digestibility The volatile solid reduction (VSR) has been used as an indicator of sludge digestibility (Luo et al., 2022). Hence, the steady-state VSR of all digesters were determined. Assuming the VSR of PS does not change with and without blending, the blended WAS VSR can be calculated and compared to the control WAS VSR without blending and Al supplementation to assess whether the WAS digestibility has been improved. As can be seen from Figure 1, the WAS VSR did not change with and without blending with PS at a 1:1 ratio without external Al addition. This means blending PS at this low ratio does not improve the WAS digestibility. When a low dose of Al was added to increase the blended sludge background Al level from 1.49 to 1.95%, it can be seen that WAS VSR decreased about 2%, indicating the inhibitory effect of Al on WAS digestion. The reduced hydrolysis rate as a result of binding between Al and protein in WAS has been regarded as the reason accounting for the WAS digestibility decrease (Luo et al., 2022). This conclusion was reinforced by the fact that WAS VSR substantially decreased to 15% when further increasing the background Al level from 1.95 to 2.85% without changing the blending ratio (Figure 1). It is interesting to see that tripling the PS blending ratios can bring WAS VSR back to 28% even when the same high Al dose (2.85%) was used in the sludge mixture. These observations suggest that co-digesting PS with WAS does not directly improve WAS digestibility; however, adding more PS does mitigate the Al inhibition on WAS digestion. It was reported in a previous study that Al is expected to play greater binding effects on WAS than on PS because the affinity of Al to proteins in WAS is higher than that to the polysaccharides in PS (Luo et al., 2022). Therefore, PS might be able to prevent the binding between Al and protein in WAS by acting as a barrier. Hence, the reduced binding potential between Al and protein in WAS could mitigate the Al inhibition on WAS digestion. rDON The centrates containing DON generated from all four digesters in phase II study (Table 1) were exposed to aerobic incubation for 14 days. Profiles in Figure 2a showed that centrates from PS only and blended sludge with high Al addition contained the least DON. PS does not contain much protein and thus is reasonable to produce less DON. Al ¬ is known to be capable of precipitating DON (Zhang et al., 2020), which may explain the low DON level in centrate with high Al addition. In contrast, the DON levels in both WAS only and blending sludge without external Al addition were two times greater. The same trends were also observed with the residual DON, namely rDON in Figure 2b. It should be pointed out that the rDON level in blended sludge was actually substantially greater than the average level from the two individual sludge without blending, indicating extensive Maillard reaction might have occurred when PS and WAS were blended. Conclusions It can be concluded from this study that blending PS does not directly improve the WAS digestibility. Instead, blending more PS did mitigate the inhibitory effect of Al on WAS digestion. However, blending PS with WAS promoted rDON formation due to Maillard reaction between the two types of sludges.

Background Wastewater infrastructure plays a critical role in urban communities, providing for the safe and efficient conveyance and treatment of sewage to protect human health and the environment. In the United States, over 16,000 centralized wastewater treatment plants serve approximately 74% of the population (Environmental Protection Agency, 2004). The majority of these plants provide at least secondary treatment of wastewater before discharging to local water bodies. Some plants may also provide advanced treatment to remove additional constituents that could impair the quality of receiving waters (EPA, 2004). Wastewater treatment plants (WWTPs) are strategic infrastructures that remove contaminants from wastewater, thus supporting human health and environmental protection (Panico et al. 2013). Majority of the wastewater treatment plants are generally located in low elevations to facilitate the conveyance of wastewater flows to the plant by gravity to minimize the number of pumping stations and the cost of wastewater treatment. Due to its location, wastewater treatment plants are more vulnerable to the extreme weather events such as floods, sea level rise and hurricanes. These extreme weather events could increase or decrease the wastewater flows to the plant, increase or decrease the pollutant concentration and increase or decrease the wastewater temperature depending on the type and severity of the events whether it is high precipitation and flooding or drought conditions or snow melt. During these events, the performance of the wastewater treatment plants can deteriorate or fail completely when it is stressed beyond the design or operation conditions, consequently impacting the human health and environment. The objective of this paper is to focus on the operational strategies that could be implemented at the wastewater treatment plants to face the challenges of extreme weather events to be more reliable and resilient wastewater treatment system. Objectives: During the extreme weather events, the operational failure and deterioration of effluent quality can occur due to high influent flows or pollutant concentrations. Some typical reasons for plant performance degradations are (NYCDEC 2000): loss of biomass from the aeration tanks and secondary clarifiers, overloading of the aeration system from high biochemical oxygen demand (BOD) loadings caused by solids washout, electrical overload of mechanical surface aerators, and decreased BOD removal efficiency due to shortened hydraulic retention time in the aeration tanks. The objective of this work is to illustrate how the operational strategies such as blending of the partially treated effluent with biologically treated effluent, increased aeration, increased chemical use, increased return sludge recirculation, controlling sludge retention time (SRT), use of unused or redundant tanks for aeration can be utilized to handle the increased influents flows and pollutant loads during the high precipitation (rainfall) associated with the extreme weather events. Methodology, Results and Discussions Influent flows and pollutant concentrations significantly influence the performance of the wastewater treatment plants in maintaining effective treatment to provide the desired effluent quality. High precipitation rates will result in increase in influent flows into WWTPs due to flow from combined systems and I&I. While the volume or 'flow' of the wastewater increases due to increased stormwater infiltration, the mass of pollutants in the wastewater may remain the same, resulting in a dilution of the influent to the WWTP which can affect biological treatment processes and solids separation process. Typically, the wastewater treatment plants are designed to handle the maximum month average daily flows while the plant is designed hydraulically to convey the peak hourly flows which is expected last few hours in a day. During the extreme weather events, the plant inflows may be expected to receive the peak flows for several hours or even few days depending on the severity of the weather event. In this work, a hypothetical conventional activated sludge plant of 5 MGD was created using the process modeling software BioWin 6.2 (Figure 1) to determine the performance and maximum treatment capacity of the wastewater treatment plant in response to the increased influent flows and pollutant concentrations (BOD, Ammonia-nitrogen, Total Suspended Solids (TSS) and Total Phosphorus (TP)) for the extended period of time under the following operational strategies: Diverting and blending partially treated wastewater: Flows that exceed the maximum biological treatment capacity of the aeration basin is diverted after the preliminary treatment system, treated at the primary clarifier, and blended with the biologically treated effluent from the main process. This strategy will be effective on facing the challenge of high flows as the pollutant concentration will be more diluted due to the extraneous stormwater mixed with the wastewater. Increasing Return Activated Sludge Recirculation: During the high flows, the sludge blanket at the secondary clarifier is likely to increase resulting high TSS leaving the effluent and impacting both the effluent quality and the biological treatment process in maintaining mixed liquor suspended solids. Increasing the RAS recirculation rate will alleviate this problem in maintaining the effluent quality in a short run. Increased aeration: During the high flows, although the pollutant concentration is likely to be low, the mass loading still could be relatively high resulting increase in high aeration demands. Increasing the airflow rate can remove BOD and increase the nitrification to remove the ammonia-nitrogen. Controlling Solids Retention Time: Solids Retention Time (SRT) is one of important operational parameter of the wastewater treatment plant operation in accomplishing desired BOD and nitrogen removal. SRT is dependent on several other operational parameters such as mixed liquor suspended solids in the aeration basins, excess waste activated sludge wasted from the secondary clarifier, influent flow rate, influent wastewater characteristics and RAS recirculation rate. Maintaining the SRT at desirable range by controlling other operational parameters could be an effective short-term strategy to deal with the increased flows from the extreme weather event. Increased chemical use: During the high influent flows, the chemical treatment can be used for improving solids separation and also for removing phosphorus by addition of the iron or alum along with polymers as a short-term strategy to improve the effluent quality. Use of unused or redundant tanks for use as aeration basins: Unused tanks, if any, at the wastewater treatment plant or back up tanks can be added at the wastewater plants to increase the hydraulic retention time (HRT) and SRT to provide the effective treatment. Conclusions This work will demonstrate how the operational strategies discussed in the above section can be used to determine the maximum handling capacity of a hypothetical 5 MGD wastewater treatment plant to prepare for the plant for the high influent inflows during the extreme weather events. The illustrative case study will provide the quantitative examples with limiting treatment capacities for each of the operational strategies discussed above using the process simulation results from the BioWin 6.2 Software that was used for creating the process model for the 5 MGD plant. The methods and operational strategies demonstrated in this work can be extended to the advanced wastewater treatment (AWT) facilities.

Pressurized pipeline infrastructure (both water and wastewater) throughout the US is reaching a critical stage of critical condition. The outlook of this infrastructure as recently described in ASCE's 2017 Report Card (and statewide individual report cards in each successive years) shows that the trend line of system deterioration is getting worse for both water and sewer conveyance systems. This trend will not change direction in a positive manner, unless a number of critical steps are undertaken. The report insists that the only feasible way to address this rapidly increasing rate of pressurize pipelines for both water wand sewer infrastructure deterioration is through asset management. Specifically, it states that 'Asset management provides utility managers and decision-makers with critical information on capital infrastructure assets and timing of investments. Some key steps for asset management include making an inventory of critical assets; evaluating their condition and performance; developing plans to maintain, repair, and replace assets; and funding these activities'. The ones that are hardest are also the ones that are, for the most part, pressurized 24/7/365. To turn this corner and establish better and more reliable information on the actual condition of these buried and essential pressurized assets, several recent (and very cool) advances in performing both external and internal inspection and assessment of water mains, force mains, valves, hydrants and other ancillary facilities has moved the level of understating condition and remaining useful life (RUL) to new levels. With these technologies and established protocols for determining their associated risks, cities and utilities are starting to bring this all together under effective asset management (AM) planning so that the three pillars of AM can be managed: sustainability, reliability, and efficiency. This presentation will highlight and describe both established and new technologies in the industry's large and ever-expanding toolbox to cost-effectively move through even the largest system representing several hundred miles of pressurized pipeline in a tiered or stepwise strategy to identify those assets that are considered highest in priority and in eminent state of operational failure. This process is illustrated in the following Exhibit A.We will discuss those technologies that fit under the four stages of assessment including those that are particularly effective using science-based systems such as acoustics, correlators, HDCCTV, sonde, GPR, ultrasonic tomography, electromagnetics, and transient wave propagation. These technologies represent a wide spectrum of manufacturers and providers. The presentation will then show how date from these sources can be used, alongside of updated and newly developed NASSCPO PACP codes to compile information from each level of assessment, transform this information into meaningful and representative condition grades and scores and then create prioritized reports for capital improvement and planning projects. The work flow process that will be discussed is shown in Exhibit B. Time permitting, we will show one additional step in the process of moving everything toward an asset management program which will enhance capital improvement, create prioritized planning (again based on risk-managed approach using a traditional risk matrix), and develop preventative maintenance activities and their relative work order frequencies. By using advanced field-based inspection technologies and incorporate them in a sequenced manner, the resultant engineered data will provide water and wastewater utilities with much better information to do PMP for the daily, weekly, monthly, and yearly planning and scheduling. Figure C shows how specific assets identified in the highest risk cells of a risk matrix are polled and integrated into CMMS for work orders and inventory management. In its essence we will show how utilities can logically and sequentially budget and fix buried pressurized before they fail using RISK and high-end technology for field, data assessment and prioritization. Two project examples will be presented to attendees.

Executive Summary: South San Francisco-San Bruno Water Quality Control Plant (WQCP) incorporated high-solids digestion to cost-effectively provide necessary capacity and avoid the need to build additional digester tanks. Following third-party validation of healthy digester operations in high-solids conditions, the WQCP advanced a food waste co-digestion pilot in partnership with a nearby waste management authority. The pilot demonstrated significant increase in biogas production, without negative impact to digester health. The initiative not only sets the stage for the WQCP to advance energy-neutrality but also supports achievement of state-level organic waste diversion mandates in California to support greenhouse gas reductions. Background: The WQCP identified a need to rebuild the plant's three existing digesters due to seismic concerns and built additional AD to meet future load growth. While capital planning initially called for new construction of five (5) digesters total, Carollo Engineers conducted an alternatives analysis considering high-solids digestion to more cost-effectively achieve the required digester capacity. Carollo evaluated a scenario pairing two (2) conventional AD with one (1) high solids digester employing Anaergia's Omnivore high-solids digestion platform. Anaergia's two-part Omnivore AD platform triples capacity of existing digesters to maximize existing WRRF infrastructure and provide redundancy. Anaergia's sludge screw thickener (SST) (Fig. 1) recuperatively thickens digestate to decouple SRT from HRT, allowing digesters to operate at significantly higher solids content. By separating water from digestate, excess water is removed and returned to plant headworks for additional treatment and/or nutrient recovery, while thickened solids (typically 12% TS) are returned to the digester (Fig. 2). Digestate is therefore thickened up to three-fold (6-8% TS) thus tripling F:M ratio and enabling organic loading rates up to 0.33 lb-VS/ft3/day. By decoupling SRT from HRT, Omnivore ensures SRT well over 15 days required for regulatory compliance and stable digester operation. To ensure proper mixing in higher solids conditions, Omnivore employs Anaergia's high-torque submersible propeller mixers (Fig. 3). These high-efficiency mixers are designed to effectively mix high viscosities that result from thickening digestate and resist ragging. By applying mixing energy directly to digestate, Omnivore mixing achieves a high standard of mixing performance, over 90% of the digester volume continuously mixed above critical velocity (0.3 ft/s) ensuring maximum volatile solids destruction, biogas production, avoiding settling of grit, and homogeneity de-risking upset events such as rapid rise. The Carollo evaluation indicated that the proposed configuration leveraging high-solids digestion would deliver equivalent digester capacity to the originally planned five (5) tanks. Further, lifecycle cost analysis confirmed that the high-solids alternative would not only achieve CAPEX savings but OPEX savings, resulting in approximately 10% overall savings over the project life. OPEX savings to the WQCP primarily result from improved mixer energy efficiency and reduced polymer consumption associated with dewatering. Application: In late 2020, construction was completed to retrofit Digester 1 (0.83 MG) with the Anaergia Omnivore high-solids digestion (HSD) system. The technology package included one skid-mounted sludge screw thickener (SST) for recuperative thickening, three high-solids submersible PSM digester mixers, three mixer service boxes, and all ancillary equipment for a complete Omnivore system. Existing mixers were removed from Dig. 1 and replaced with new Anaergia propeller mixers. Mixer selection was validated and informed by computational fluid dynamic (CFD) modelling, the results of which are summarized in Tables 1-4. The model demonstrated low energy demand, improved tank mixing, and energy-efficient mixing performance, particularly in high-solids conditions (6% TS), as compared to linear motion and pump mix alternatives. Platforms installed provide access to Anaergia service boxes (Fig. 3), which enable in-situ mixer access without interrupting AD operations. Each mixer is mounted to a vertical post inside the digester allowing for height and attack angle adjustments to achieve optimal mixing, resuspend settled grit, and break scum accumulation in upper layers. The SST and accessory equipment were installed adjacent to Dig. 1, reducing pump energy, footprint, and impact on WQCP operations. Dig. 1 was brought online on January 5, 2021. Recuperative thickening was initiated in February and achieved steady performance in April (Fig. 4). Third-party performance testing was conducted in conjunction with Anaergia from April to July 2021. The below performance criteria were evaluated and achieved (Table 5): -Min. volatile solids reduction (VSR) above 57% for 80% of the time over 90-day test period, over a 30-day moving average (Fig. 5) -Demonstrate stable digester operation with volatile fatty acid (VFA)/alkalinity ratio <0.2 (Fig. 6) Testing further confirmed successful HSD in Dig. 1 as demonstrated by increased digester feed volumes, TS loading, and VSR. A third-party Lithium-ion Tracer test was conducted to confirm achievement of mixer performance requirements. The independent study (1) validated achievement of Anaergia's high-performance mixing standard (>90% of digester volume >0.3 ft/s) and (2) aligned with CFD modeling of mixer performance, which indicated superior performance compared to alternate mixing technologies. Co-Digestion Pilot: In July 2022, following successful completion of performance testing, the WQCP began a pilot program to receive 1-2 deliveries per day of slurried food waste. The organic slurry is produced at the South Bayside Waste Management Authority's Shoreway Environmental Center. The materials recovery facility (MRF) employs an Anaergia Organics Extrusion (OREX) press and Organics Polishing System (OPS) to remove contamination from commercial source separated organics and create a clean, homogenized, pumpable organic slurry. The slurry is pumped into 5,000-gallon liquid tanker trucks and hauled approximately 15 miles from the MRF to the WQCP. The slurry is fed to Dig. 1 for co-digestion with indigenous biosolids. The high-solids digestion upgrades have facilitated the pilot by provided excess capacity for external feedstock, as well as high-solids mixing capability within the digester to maintain digester health and mixing performance. WQCP monitoring indicates significant increases in biogas production since the initiation of high-solids digestion and co-digestion, respectively. Ongoing data collection during the pilot will inform planning and design of food waste receiving and biogas utilization upgrades to facilitate long-term co-digestion and advance energy-neutrality at the WQCP. Note that the high-solids digestion design was developed to meet performance requirements and operational objectives requested by WQCP representatives and does not maximize use of Dig. 1 volume. Operation at higher solids would further increase digester capacity for future growth needs or expanded co-digestion. Conclusion: The Omnivore system effectively addressed the biosolids and residuals management needs of the WQCP leveraging existing infrastructure; provided third-party validated performance improvements; and facilitated a successful food waste co-digestion pilot. As a result of the project's success, the below benefits were delivered to the WQCP: -Avoided major capital expenditure of an additional digester -Addressed capital improvement needs -Redundant digester capacity -Reliable production of stabilized biosolids -Improved digester performance -Improved mixing performance -High-efficiency mixers with lowest overall lifecycle cost -Future-proofing for load growth and changes in feedstock composition -Enable co-digestion of organic waste -Increased biogas production and energy neutrality The cost-effective retrofit has the ability to unlock additional digester capacity and increase redundancy while simultaneously improving digester performance. With the additional AD capacity created, WRRFs can rapidly accommodate increased internal sludge loads, high strength waste (HSW) for co-digestion, and improve plant resiliency. A similar solution may be replicated at WRRF throughout North America to cost-effectively improve biosolids management while significantly enhancing the ability of municipalities to leverage existing infrastructure for meaningful resource recovery and energy neutrality.

The Brooklyn Trunk Sewer (BTS) was commissioned in 1964 to decommission the Spotswood Pumping Station and convey flows by gravity to the then new Brooklyn Pumping Station. Presently, the BTS conveys approximately 30% of Metropolitan Melbourne's sewage and consists of a 2.8 m diameter concrete lined tunnel that is 3,691 m long, with a depth to invert that varies between 31m and 45m below ground level. The Spotswood Pumping Station is now an exhibit at Scienceworks Museum and is open to the public. The lower half of the BTS has corroded significantly with peak concrete loss of 100 mm, over a period of approximately 58 years, and exposed reinforcement identified in numerous places. Melbourne Water wishes to reduce corrosion rates to defer significant sewer rehabilitation and/or potential duplication, if sewer relining is not feasible. These complications are further compounded by foul odour at Spotswood, which is at the junction of the BTS and major upstream connecting sewers. Ventilation and sulphide generation models have previously been built for the BTS to support decision making aimed at extending the life of the sewer. However due to the complexity of the sewerage system (which has five forced ventilation systems that interact), there was some uncertainty regarding the movement of air within the sewer as well as gas phase hydrogen sulphide (H2S) concentrations and relative humidity (RH). A comprehensive field monitoring campaign was conducted in March 2021 to understand and assess system operation and inform decision making regarding augmenting the BTS and associated ventilation systems. Tracer gas testing of the BTS using carbon monoxide was undertaken to reduce uncertainty regarding air flow movement (flowrate, direction) and interactions with upstream sewers. Pressure, H2S and RH logging, and liquid phase testing was conducted simultaneously to allow improved calibration of the sewer models (AFT Arrow Ventilation model and WATS sulphide generation model). The monitoring campaign presented challenges relating to sewer depth and diameter and number of monitoring stations (9 total). Irrespective, invaluable insight was gained relating to the behaviour of the BTS system compared to any previous modelling. Field testing was able to quantify air flow and direction in the BTS under different operating conditions and identify null points in the system which explained why particular sections of the sewer were more corroded (due to lack of air flow, high RH and H2S). Tracer gas testing also identified high sewage-air differential velocities in the BTS which is likely contributing to higher corrosion rates. Pressure monitoring identified the likely causes of odour complaints at Spotswood. Fresh air is forced into maintenance hole BTS007 which is the junction of the BTS and upstream connecting sewers and this results in the sewers being under positive pressure at times which increases the risk of odour complaints as foul air can escape through incompletely sealed covers and connections. The sewer models were calibrated using field data and used to address odour and corrosion issues for the BTS system and build on the knowledge gained from the BTS tracer gas testing project. Furthermore, multiple projects are scheduled to be delivered over the next ten years for the BTS and upstream sewers to enhance network performance and address asset management issues. The sewer models were used to optimise the delivery of these renewal/augmentation works considering the current asset condition and performance information and known projects that are likely to be delivered impacting the BTS. The key initiatives to address odour and corrosion issues for the BTS are outlined below. The sewer air-sewage differential velocity was minimised by halving the air flow rate by approximately 50% to provide a better balance between reduced H2S stripping and lower mass transfer rates of H2S into the biological slime on the surface of the sewer versus slightly lowered dilution of H2S in the gas phase (at lower air flow rates). The modelling was calibrated well for most of this complex system, but for the BTS itself it was poorer due to the interaction with tributary sewers. The modelling indicated that gas phase H2S concentrations would increase at a lower air flow rate. The WATS and SCORe corrosion rate estimation methods, indicated that corrosion rates would increase in response to minimising sewer air-sewage differential which contradicted the original hypothesis that overall corrosion rates would decrease by lowering the air flow rate through reduced turbulence and sulphide stripping. Furthermore, it was inferred that the upper most 1,300m section of the BTS could be in better condition due to the large volumes of fresh air that are forced into the sewer at BTS007 which reduces RH in this section. Higher corrosion rates (approx. 2mm/year) in the lower half of the BTS are likely due to high RH (approaching 100%) despite gas phase H2S concentrations being low (average of 1 ppm in the most corroded section). Corrosion rates in the lower half of the BTS will continue to remain unacceptably high regardless of whether the air flow rate for the BTS is reduced or maintained at current levels since RH is the dominant factor affecting corrosion. Interventions which reduce RH in this section were identified and included in the long term investment plan. Fresh air inducts were also proposed at strategic locations to dilute H2S and lower RH. Sewer modelling calibrated with sampling and system monitoring data was used to identify suitable interventions to increase the sewer headspace vacuum at Spotswood. Options that were considered included ventilating at a higher air flow rate and adding air flow restrictions to make the fans draw harder. The air flow rate for a replacement air treatment facility at Spotswood was increased from 1.8 to 7 m3/s and air curtains were strategically positioned to restrict rather than to block air movement in the sewer. Furthermore, the BTS007 fan was converted to a passive fresh air induct to avoid pressurising the sewers at Spotswood.

ABSTRACT Utilities are more and more frequently resorting to real-time control systems that intentionally block flows in interceptors to take advantage of available in-line storage during storm surges to combat overflows from sewers. Many utilities are also more and more frequently extending their pump station's wet wells into the sewers feeding the wet well to raise NSPSH and to effectively enlarge their wet wells, improving pump performance. Both practices have significant operational end environmental value. Overlooked in these efforts are the impact of often quite significant internal pressures on pipes with joints not capable of containing these pressures. Surcharged sewers with leaking joints, when pressurized even a few feet, pass massive volumes of water outside the sewer into the surrounding pipe bedding and pipe trench backfill. When hydraulic grade lines subside to normal (open channel) operating levels, the sewage pushed outside the pipes pours back into the pipe, bringing bedding fines that eventually result in pipe bedding envelope failure and pipe collapse. This paper identifies the causes, mechanisms of failure, evidence of likely failure if surcharges, inspection techniques to identify pipes at risk if surcharged, and rehabilitation methods once a pipe is thus compromised. This paper is relevant to any utility considering or using in-line storage. Relevance, Usefulness, and Takeaways Surcharging interceptors can result in catastrophic and hugely expensive repairs if the pipes are not prepared to contain the pressures. Determining if a pipe can handle the pressures sometimes requires more than CCTV inspection. This paper provides suggested assessment measures utilities can use protect themselves from these failures as well as identify the rather involved corrective measures needed if the wrong pipes are surcharged. Demonstrated Results The project used to demonstrate these condition assessment techniques and remedial measures is largely complete. This presentation will contain meaningful photograph and video clips to convey the lessons learned.

On the heels of a major BNR upgrade completed in 2016, Capital Region Water (CRW) in Harrisburg, PA set out on making significant improvements to its solids and energy streams. CRW operates a 22 MGD Advanced Wastewater Treatment Facility (AWTF) with a pair of mesophilic digesters dating back to last major plant expansion in the 1970s. These digesters are currently undergoing refurbishment including grit removal, new covers, and mixing. With BNR and fresh digesters in place, CRW is now setting its sights on sustainability goals by targeting a project to enhance energy recovery from its solids resources. To help identify the most beneficial energy recovery project, CRW engaged with an engineering team led by Arcadis in 2018 to undertake a comprehensive solids and energy planning effort targeting upgrades. The CRW plant already had an operational history of recovering its biogas for energy using CHP engines. The plant has been operating a set of 600 kW Waukesha 'Enginators' since 1984 to make electricity and recover hot water for heating (see Figure 1). Interestingly, CRW does not utilize the CHP electricity internally, but instead transmits its generated power to the local utility and receives full delivered unit pricing via an interconnection agreement. These engines are reaching the end of their useful lives, however, and the CRW staff initially envisioned an in-kind replacement of the CHP engines with upgrades to heat recovery. The solids and energy planning effort was aimed at looking at a wide range of options both in conjunction with and in lieu of CHP. For example, the plant currently co-thickens primary sludge and WAS in gravity thickeners, leading to significant seasonal deterioration in thickening performance (see Figure 2) especially after the implementation of BNR. One of the improvements examined was the separation of WAS for mechanical thickening to improve sludge feed concentrations to the digesters. This, along with the following list enhancement items were examined: Separated mechanical WAS thickening WAS lysis for enhanced digestion New CHP engines with upgraded heat recovery Biogas to Renewable Natural Gas (RNG) Acceptance of High Strength Waste (HSW) Backup power generation with CHP Upgrades to biogas compression and transmission The key tool used to evaluate all these options and their interacting effects was holistic solids and energy flow model (see Figure 3). With this tool, any potential combination of processes or loading rates was quantitatively analyzed for annualized cost, greenhouse gas (GHG) reductions, net power generation, and capital cost. Along with determining an operationally sound and cost-effective treatment facility, processes were also examined to meet goals of maximizing value of the plant's energy resources and supporting the cost effective Class B biosolids land application program already in place. There were some very significant site specific factors identified early in the planning process. One item was the existence of a natural gas 'peaker' facility directly adjacent to the AWTF fence line in the area of the digesters. This facility is operated by the local natural gas utility. Engagement with this utility revealed a positive and cooperative position regarding connection of RNG to their system. This meant that CRW had not only identified a partner for RNG, but also would have an interconnection pipeline requirement of essentially zero. Another site specific item for this project was the abundance of high quality HSW in the area due to the presence of local food producers such as Hershey Creamery and Utz Potato Chips. These producers have previously shown high interest bringing their material to the AWTF, making the acceptance of HSW a high priority for CRW. With these site specific conditions in mind, Figure/Table 5 give the results of some of the most prominent scenarios from solid and energy flow model tool. One of the major conflicts facing this facility and many others is the illogical incentive structure under the current Renewable Fuel Standard (RFS) where digesters receiving HSW get penalized as RINs are downgraded from D3 to D5. This was confounded by the acute drop in D3 RIN pricing occurring in late 2019 during the time of the study. Significant sensitivity analysis on both D3 and D5 RIN pricing was done using the flow model tool, allowing many potential future RIN pricing scenarios to be considered. Ultimately, the decision to target both RNG and HSW acceptance was made. While accepting HSW reduced RIN value potential, it also brings in tipping fees and avoids the higher sensitivity swings related to D3 RIN prices. Some other conclusions were as follows: The replacement of CHP engines with new equipment and upgraded heat recovery did not provide an annualized savings to the plant. This included maintaining the existing interconnection agreement at $0.075/kWh and taking a capital credit for offsetting backup power generation. The main driver was the high cost of biogas conditioning and the O&M support package which is difficult to overcome for newer engines at this scale. The addition of enhanced sludge thickening by separately mechanically thickening WAS did not provide annualized savings to the plant. However, this was viewed as a fundamental investment in solids infrastructure, providing operators more control over thickening and eliminating the difficulties with seasonal bulking and performance deterioration in the gravity thickeners. Savings from other parts of the project would offset this long term investment in improved operations. The addition of WAS lysis beneficial on an annualized costs basis, paying for its capital by increasing biogas recovered as RNG and reducing biosolids to be managed. Implementation of lysis was selected, with major driver being current dewatering difficulties. Currently the AWTF must produce 20% TS cake as part of their land application which has been a struggle. With lysis, a cake TS increase of 2-3% is expected which would significantly improve dewatering operations for land application. Based on the results of this work, CRW has moved forward with implementation of the recommended project with the design completed and construction slated to begin in early 2021. The project includes a new Thickening and Lysis Building to house new WAS thickeners as well as thermal-alkaline WAS lysis. Heated and lyzed WAS will be blended in-line with received HSW in a new feed line to the digesters. A new biogas to RNG skid will be implemented with the neighboring natural gas peaker facility taking custodial transfer of the product gas for injection into the pipeline. The engineering team has also recently identified a local PA 'green gas' program in the Philadelphia area willing to pay premium prices for RNG. Partnering with this type of offtake can remove headaches related to the RFS by avoiding swings in RIN market prices and value conflicts around accepting HSW. By partnering with local food producers and natural gas utility, this project serves as model for how cooperation and regionalization can significantly uptick the value that can be obtained for energy resources at a WRRF. This also demonstrates the value of effective solids and energy planning as CRW staff were able to quickly and confidently move forward with implementation, and take on long term operational improvements such as thickening in combination with money savings aspects like HSW and RNG.

Through much convincing, DOTs in Pennsylvania, Virginia, and Maryland started utilizing performance-based contracting to comply with their MS4 permits and compensatory mitigation needs. The contracts have turn-key scopes including the acquisition of land interests, design, permitting, construction, and long-term operation and maintenance of the associated ecosystems. These projects are stream restorations, wetland creation/enhancement, or both and were won with performance-based bidding on a $/lb. of TMDL reduction or $/ac of wetland credit generation. For one of RES' PennDOT contracts, RES guaranteed over 573,000 lb. of sediment reduction for a unit cost across three BMPs. PennDOT collaborated with three additional stakeholders, Capital Region Water, Susquehanna Township, and Lower Paxton Township, to generate sediment reduction benefits divided among the parties. The BMPs were located on both public and private land, additionally complicating the full delivery process. The MDOT State Highway Administration performance based MS4 TMDL reduction solution included 22,592 LF of stream restoration across six sites in Anne Arundel, Baltimore, and Frederick Counties. The projects combined for an annual reduction of 663 tons sediment, 2,535 lb. of phosphorus, and 7,798 lb. of nitrogen applied to SHA's Chesapeake Bay restoration goals. The VDOT project is enrolled as part of VDOT's Chesapeake Bay TMDL Action Plan and included approximately three miles of degraded channel along Wancopin Creek, as well as several unnamed perennial and intermittent tributaries to Wancopin Creek and Goose Creek on private property. The project proposed to reduce approximately 4,300 lb. per year of phosphorus per Protocol 1 in the Expert Panel Report and TMDL Action Plan Guidance. However, monitoring the completed phase I demonstrated over 95% efficiency in terms of load reduction, significantly higher than the 50% default rate outlined in the Expert Panel guidance. To decrease the unit costs by increasing project scale, RES increased the size of the project by creating a privately funded mitigation bank with the remaining streams on the property through restoration or preservation, generating credits to offset impacts authorized under Clean Water Act Section 401/404 permits. Mitigation activities on the site included 4,152 linear feet of additional stream restoration, 94.81 acres of riparian buffer planting, 31.67 acres of riparian buffer restoration, and 151.32 acres of riparian buffer preservation, generating a total of 21,557 stream credits. The divergence from the status quo of design-bid-build saved each of the taxpayer funded clients millions of dollars and reduced project timelines by years. While using stream restoration and wetland creation is not a new way of achieving TMDL reductions, the innovative full-delivery project approach has proven to be successful across multiple jurisdictions along the east coast.

APPLICABILITY Treatment and the security of disposal/beneficial use options for biosolids is constantly evolving due to more stringent regulations as new contaminants in wastewater raise concerns about potential migration into biosolids and subsequent impacts. Advancements in treatment technologies and development of new markets for different types of biosolids products offer opportunities to mitigate risks to current biosolids management options while maintaining a certain level of institutional control. Economics and utility-specific drivers and constraints play key roles in selecting the right combination of treatment technology and end use. DEMONSTRATED RESULTS/CONCLUSIONS JEA, one of the largest utilities in the State of Florida, has been highly proactive in evaluating and looking to the future with their biosolids program. In 2017, JEA prepared a master plan to evaluate replacing their aging biosolids handling facilities while charting a path for the future. The existing biosolids handling facilities are located at the Buckman Water Reclamation Facility (BWRF), JEA's largest WRF. The facility handles sludge from 9 of the 11 JEA owned and operated WRFs. Solids from the two remaining WRFs are dewatered and the cake is hauled to nearby landfills for disposal using separate, third-party hauling and disposal contracts. Currently, liquid sludge from JEA's three larger WRFs is pumped long distances via dedicated sludge force mains and received at the BWRF headworks. The solids are captured in the primary clarifiers at the BWRF and pumped to a raw sludge holding tank (RSHT). The solids from the remaining five JEA WRFs are hauled as liquid sludge and received at the RSHT. The existing biosolids handling facilities at BWRF include thickening, anaerobic digestion, dewatering and a thermal drum drying system producing a Class AA product. The Class AA product is hauled by a third party for polishing and product marketing for beneficial reuse. All the existing solids handling equipment is retrofitted in an old incinerator building that has also reached the end of its useful life. Since the equipment was retrofitted in an existing building, the layout has inherent inadequacies that result in operational challenges. Further, the thermal drum drying facility only includes a single drum that also reached its end of useful life, providing no redundancy. The 2017 master plan recommended decommissioning of the old thermal drying system and instead hiring the services of a third-party to receive the anaerobically digested Class B dewatered cake. The third-party would take full responsibility for further processing and final product marketing and ultimate disposal. The master plan recommended construction of a new solids handling building with new thickening and dewatering equipment to replace the aging infrastructure. However, this approach resulted in undue dependence on a third-party for cake hauling, further processing, and appropriate disposal of the biosolids, thus leading to uncertainty in capital and long-term operating costs, adherence to future regulations, and impacts of market conditions/changes on disposal of the product. As a result, in 2020, JEA revisited the findings of the earlier master plan. The 2020 master plan evaluated several short-term and long-term biosolids management strategies and recommended replacing the existing thermal drum drying system with two larger drum dryers providing greater process reliability and redundancy while continuing to produce a Class AA product with substantial volume reduction for ease of product transport and disposal. The 2020 master plan ultimately recommended constructing a new regional biosolids handling facility at BWRF, that can handle solids from all 12 WRFs owned and operated by JEA, thereby providing JEA the desired level of control for their biosolids handling and disposal options. Such regionalization could be adopted by other utilities seeking certainty and control for their solids treatment and disposal options. As part of the short-term strategy, JEA has refurbished several of the thermal drum drying system components. The utility is also in the process of rehabilitating the existing building for operator safety and extending the life of the building for the next 5 years until the completion of the new biosolids handling facilities. A new multi-story biosolids treatment facility (BTF) has been designed and is under construction as the long-term permanent solution for JEA. This facility, shown in Figure 1, will house new thickening equipment (5 gravity belt thickeners), new dewatering equipment (4 centrifuges), and two new thermal drum drying systems (evaporation rate of 10,000 kg/hr) with pellet storage and a truck loading station. As illustrated in Figure 2, the new BTF will be a regional facility sized to accommodate all solids generated by the 12 JEA WRFs. Unstabilized dewatered cake from three remote facilities will be shipped to the new BTF where plant effluent from BWRF will be used to dilute the dewatered cake to thickened sludge consistency and added to the anaerobic digestion process. This is intended to maintain a consistent feed to the drying process such that high-quality pellets are consistently produced and dust and fines formation is reduced. PROJECT INNOVATION A full-scale pilot of an in-line high-shear dynamic mixer coupled with a density meter was successfully conducted onsite to re-wet the dewatered cake solids (~21% total solids) from remote plants with plant effluent to produce a consistent product with a total solids concentration of ~4 to 5% to feed to the existing anaerobic digesters. This cake mixing concept, shown if Figure 3, could be a game changer for agencies seeking to ship their un-stabilized dewatered cake to regional facilities for stabilization and further treatment, while reducing transportation costs, truck traffic and avoiding significant capital expense at the smaller surrounding plants. This type of system could be integral to the regionalization that may be necessary to accommodate changes in biosolids management that could necessitate costly thermal processes to reduce potential impacts from constituents of emerging concern like PFAS.

The purpose of this presentation will be to discuss how the design used an Electrical Resistivity Imaging survey to find a highly feasible bore path under a river for Horizontal Directional Drilling. A recently completed project will be use a case study as well as another project with very similar conditions, but different outcomes due to the different approaches to geotechnical exploration. To reduce annual overflow volume for the Sanitation District No. 1 of Northern Kentucky, a new 18-in gravity siphon sewer was needed to convey flow across (under) the Licking River in Wilder Kentucky. The Licking River is tributary to the Ohio River and located just south of Cincinnati. The width of the river where the new siphon sewer crossing is located is between 300 and 400 feet, depending on the river level. Horizontal Directional Drilling (HDD) was the selected method of construction selected for the new siphon sewer. Since the proposed Licking River Siphon is a gravity system and connects into upstream and downstream sewers, the bore elevations had to be within a rather tight tolerance. From prior experience and challenges with HDD not maintaining line and grade, specifically along a riverbank where cobbles and boulders can often be found, Hazen and Sawyer utilized Electrical Resistivity Imaging (ERI) to find an optimal bore path. Standard split-barrel soil borings and rock cores were also used to calibrate the ERI survey, but they were not solely relied upon to determine the best bore path. Cobble and boulder fields are very hard to identify with only standard soil bores. Another prior HDD project on a very similar river crossing will be discussed where the cobbles and boulders led to construction delays and overruns, until ERI surveying was implemented. This presentation will also discuss other lessons learned related to trenchless and open-cut construction, such as inadvertent returns (frac outs), high river water, HDD tracking systems, production rates in hard rock, bidding document interpretations, USACE permitting, and various other issues. Part of this sewer project was located in a railroad's property which added its own design and construction challenges. The project was successfully completed in 2022 with the HDD being very close to the specified line and grade.