Conference Papers

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

ABSTRACT British Columbia (BC) is 1.4 times the size of Texas. While only 1% of its land base is native grassland, these areas have been historically prized for homesteading and early agriculture. Today they are mainly used for ranching, but over a century of use has left many BC grasslands in a degraded state. These grasslands support more threatened and endangered species of birds, animals, and vegetation than any other terrestrial biome in the province. The OK Ranch is a 15,000 acre cow-calf operation located in the interior of BC, and was emblematic of these challenges. The upland grasslands of the OK Ranch experienced a decrease in productivity over the last century due to long-term agricultural and grazing practices, now compounded due to climate change. First Nations oral histories tell of tall grasses 'belly high to a horse' flowing with the upland winds, but due to historic homesteading and more recent attempts at cereal production in this dry, high-altitude area, soils were exposed to harsh elements and the natural forage was unable to return to previous production levels. In 2013, SYLVIS partnered with the OK Ranch's landowner to emphasize grassland restoration using biosolids to achieve effective stewardship as well as productivity for the ranch operation. Since that time, SYLVIS and Metro Vancouver, together with several research partners, have sought to understand and quantify the benefits conferred to the site through the careful use of biosolids as a soil amendment tool. This presentation will share the unprecedented understanding of what can happen for a degraded ecosystem when provision of critical soil conditioning supports rehabilitation. Specifically, we will discuss how: -Soils have been protected through the growth and expansion of a thatch layer, and reduction of bare soil and crusting throughout the site. -Grasses have recovered and now grow with vigour, producing up to 400% more biomass, while also being more nutritious for cattle and ungulates. -The changes in biomass and resilience have resulted in significant carbon capture on the landscape, both in short-term annual carbon through above ground biomass, but also in long-term belowground carbon capture and storage in soils and roots. -The improved grass structure has resulted in favorable habitat development for endangered or threatened insects, which in turn support threatened bird species, which has become a major research focus at the OK Ranch through a partnership with the University of British Columbia. -Mammals, large ungulates, and predators appear to spend more time in the grasslands. -The productivity has resulted in increased employment at the OK Ranch, with more cattle and more hands hired to help manage those cattle. -A desktop analysis of climate change mitigation and ultimate benefits to the environment provides a compelling case for the economic, environmental and societal value of grasslands restoration. The OK Ranch grasslands restoration project is more than just land application of biosolids. It demonstrates the layers of co-benefits provided through the restoration of semi-arid grasslands of not just soil improvement, but of carbon capture, habitat recovery, and economic development. . The presentation will conclude with a discussion of what levels of awareness and information sharing might be required, and what innovative strategies are available to increase uptake of beneficial use messages to achieve this kind of scale for grassland restoration in North America.

Dewatering Benefits of SLG Technology at the McDowell Creek Wastewater Treatment Plant Anish Luthra, PE, PMP, CDM Smith Kathryn Quaid, CDM Smith Muriel Steele, PhD, PE, Charlotte Water Charlotte Water's McDowell Creek Wastewater Treatment Plant (WWTP) has historically faced biosolids dewatering challenges related to achieving typical industry cake dryness for belt filter press dewatering of anaerobically digested biosolids. This presentation will discuss the dewatering benefits experienced by the plant by piloting a solids-liquid-gas (SLG) pretreatment process ahead of belt filter press dewatering. The plant's processes include screening, grit removal, primary clarification, 5-stage BNR for nitrogen and phosphorus removal, secondary clarification, deep-bed sand filters, UV disinfection, cascade aeration, gravity belt WAS thickening, mesophilic anaerobic digesters, and dewatering belt filter presses. Anaerobically digested solids from four primary digesters overflow into a single, common secondary digester. From the secondary digester, digested solids are pumped to the dewatering facility for final dewatering via Ashbrook belt filter presses. Dewatered cake is conveyed by a belt conveyor to a covered storage area before being loaded onto hauling trucks typically for land application, or alternatively landfill disposal. In recent years, the plant has struggled to produce dewatered cake total solids concentrations above 12.5% on average. In early 2023, Charlotte Water elected to pilot the solids-liquid-gas (SLG) pretreatment process offered by Orege to optimize the dewatering operations at the McDowell Creek WWTP. The SLG technology is composed of three parts - the SLG skid, an air compressor, and a deaerator. The SLG technology uses compressed air to modify the rheology of the digested sludge upstream of belt filter press. Low pressure compressed air is injected into the digested sludge, creating a floating emulsion sludge. Polymer is then added to the emulsion to complete the flocculation process ahead of dewatering. The emulsion's larger solids surface area improves polymer adherence, resulting in better water release and higher cake dryness. Before the pilot was commissioned, Charlotte Water developed pilot evaluation criteria containing a variety of measurable and subjective goals to determine pilot success. Pilot logistics were then established through a collaboration between Charlotte Water, CDM Smith, and Orege. It was determined that the plant's existing digested sludge pumps that normally feed the belt filter presses would not have enough head to overcome the pressure of the SLG unit. As such, a temporary 1000-gallon sludge buffer tank and additional sludge pump were provided. Temporary piping was installed to feed the buffer tank, sludge pump, SLG skid, deaerator, and belt filter press. A variety of polymer selections were also evaluated as part of the pilot to determine compatibility with the SLG emulsion. Once the pilot was commissioned, the baseline verification period began. The project team observed Charlotte Water's operation of the belt filter press under typical operating conditions and collected and analyzed baseline samples to compare against historical data. After a week of baseline verification, the pilot moved into the optimization period. During this period the belt filter press was started under typical operating conditions by Charlotte Water and baseline samples were collected before the SLG unit was started up for the day. During the three months of optimization, the project team made process adjustments to the SLG unit and belt filter press to determine the optimal operating parameters for pilot operation. Once the optimal pilot operating parameters were determined, the field staff performed a two-week field test. During the field test, the belt filter press was started under normal operating conditions and baseline samples were collected and analyzed. Then, the SLG unit was started up and optimal pilot operating parameters were set. Multiple samples were taken throughout the SLG run time before the unit was shut down and the belt filter press was adjusted back to normal parameters for a second round of baseline sampling. This process was repeated for 10 days, during which baseline parameters remained consistent and SLG parameters remained consistent. The pilot results suggested the SLG pretreatment process improved cake dryness by an average of approximately 2% total solids concentration. This is a significant improvement from the historical performance of McDowell Creek WWTP's dewatering operations. Polymer treatment rate and filtrate quality remained similar to baseline conditions. Table 1 contains average field test results and historical data. Figures 1-3 present daily average cake, filtrate, and polymer treatment rate results from the field test period. The project team is currently performing a lifecycle cost analysis to evaluate the capital cost investment of the SLG pretreatment process and the annual cost savings associated with the operational improvements of the SLG process, which will be ready for presentation by the time of the 2024 Water Environment Federation (WEF) Residuals and Biosolids Conference.

1.0 Purpose Wastewater sludges that contain more than 1.5 to 2 percent solids have fluid characteristics that are different than clean water. The complex non-Newtonian behavior of sludges requires more in-depth hydraulic analyses, especially when there is variability in solids concentrations. These complexities can be quantified using rheology, the study of the deformation and flow of matter. Rheology is required to appropriately design systems for non-Newtonian fluids such as primary sludge, waste-activated sludge, combined undigested sludge, thickened sludge, digester recirculation, and dewatering feed sludge. The primary goal of measuring and representing these rheological characteristics is to achieve a higher precision in hydraulic design. Rheological data was gathered for a solids improvement project at Kitsap County's Central Treatment Plant to develop hydraulic model inputs in AFT Fathom„¢ to then determine thickened sludge process design criteria. Measured rheological characteristics and updated design method findings were compared to typical rheological values and historical design methods to inform final design criteria for the thickened sludge process improvements. The measured rheological data and alternative design approach can be applied to future projects by leveraging a growing data base of rheological characteristics and alternative design approach performance data. 2.0 Rheological History and Historical Design Approaches There are typically two approaches to sizing sludge pumps. When plant data cannot be collected, it is common to use standard rheological values. A downside to this approach is that it is typically only recommended for pumping lengths of less than 100 feet. Alternatively, pump testing can be used to determine rheological characteristics but it requires a pump to already be installed and, in many situations, hydraulic analysis and design must be conducted prior to testing. It can also be difficult to estimate the pressure spike associated with pump startup to initiate sludge movement. 3.0 Rheological Experimentation An alternative approach to estimate sludge pumping hydraulics is to test plant sludge with a rotational rheometer and use that data as an input to a non-Newtonian hydraulic model. Through the use of a Brookfield DVNext rotational rheometer, rheological sampling and analysis for pumped sludges can be conducted (Ametek Brookfield Inc., 2019). This piece of equipment applies a shear force and torque to a fluid using a rotating spindle. It records the shear rate, which is a function of the spindle speed, the shear force, torque, and viscosity. Testing these values by varying the spindle speed creates a viscosity and shear stress profile for each sample. This profile characterizes the rheological properties of the fluid. The samples are also tested to determine the solids concentration so a relationship between the rheological profile and percent solids can be defined. 4.0 Application of Rheology to Modified Design Approach The purpose of these plant-specific studies is to improve hydraulic calculations using the observed rheological properties of the sludge to then establish design criteria for sludge pumping applications. AFT Fathom„¢ is a hydraulic modeling software that has capabilities to input observed rheological data and compare it with various non-Newtonian fit models to estimate the hydraulic impact of a given sludge. Such models include the standard Power Law, Bingham Plastic, and the Herschel-Buckley fits (Water Environment Federation and the American Society of Civil Engineers, 2010). AFT Fathom can then use these characteristics and fit models, along with other information such as preliminary pipe lengths and fittings, to determine the total dynamic head and other hydraulic design criteria (AFT Fathom 2023). To further improve the analysis, AFT Impulse„¢ can be used to estimate transient pressure spikes that may occur during pump startup The Fundamentals of Unfamiliar Fluids (Clark, 2021), (AFT Impulse 2023). 5.0 Case Study HDR is designing improvements for various solids treatment processes at Kitsap County's Central Treatment Plant. Amongst other miscellaneous solids improvements, new primary sludge, septage, and WAS thickening equipment and two new digesters will be designed. Equipment to support these process improvements such as thickened sludge pumps, process piping, meters, etc. are included in the design. Rheological data was collected from the plant to design new sludge pumps and ensure adequacy of existing sludge pumps for process modifications. 5.1 Experimental Approach Data was collected over four sampling events, two different seasons, and varied operational scenarios to determine a modeling and design basis for different sludge streams. Co-thickened primary sludge and septage, digested sludge, and thickened WAS samples were collected and analyzed with the rotational rheometer on site. Triplicate runs were conducted for a wide range of shear rates to collect each stream's rheological properties per testing methods recommended by the rheometer manufacturer (Ametek-Brookfield, Inc., 2017). Once trials were complete, onsite laboratory staff used standard methods to determine each sample's percent total solids and total volatile solids. 5.2 Experiment Results and Data Evaluation Test results revealed that shear stress values are, generally, positively correlated with the total solids of the samples. As anticipated, seasonal temperature impacted viscosity measurements with the colder conditions prompting more conservative design values. For each stream, shear stress and shear rate data were evaluated using the Bingham Plastic, Hershel-Buckley, and Power Law rheological fit models. Tested samples had a lower percent solids (4-6%) than the anticipated design condition after the thickener (5-8%). To address this discrepancy, measured rheological fit curves were extrapolated to estimate the properties of thickened sludge with a higher percent solids concentration than what was tested. This approach required multiple hydraulic model runs using each rheological fit model to determine the most reasonable design conditions and to avoid oversizing of the pumps. In summary, measured data for each sludge was input into the hydraulic model for each rheological fit and compared to typical design approaches to estimate the total dynamic head (TDH) that the thickened sludge pumps would experience. In some cases, typical design approaches provided more conservative TDH values as compared to the alternative design approach using measured rheological characteristics. Figure 1 depicts one example of testing results for thickened waste activated sludge (TWAS), thickened primary sludge and septage (TPSS), and digester sludge. Figure 2 depicts the rheometer on-site during a sampling event. Comparison of TDH for typical design approaches and alternative modeled design approaches based on measured data are compared in Table 1. Another rheological sampling event will be conducted in January 2024 to measure additional characteristics and seasonal variability for the sludges in question. These additional results will be compared to summer sampling data to finalize elected design criteria for the thickened sludge process improvements. 6.0 Future Development of Rheology In preparation of the aforementioned rheological testing, an internal best practice document was developed in collaboration with Matt Higgins at Bucknell University to define appropriate rheological testing criteria, data analysis methods, and design approaches using measured data. It is expected that this document will continue to be refined as more sampling events are conducted. Upon construction of each project, performance data will be evaluated to calibrate and improve the experimental criteria and alternative design approach. Rheological data sets from sludges tested at various plants can be compiled into a database to evaluate trends and consistencies in different sludges. Depending on the depth and breadth of data available and resulting findings, this comprehensive dataset may ultimately be used as a standard reference for design.

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

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

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

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

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

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

Background The Des Moines Wastewater Reclamation Authority (WRA) is made up of 17 metro-area municipalities, counties, and sewer districts in Central Iowa. They work together to protect public health and to enhance the environment by recycling wastewater and being the preferred treatment facilities for hauled liquid wastes. The Des Moines WRA has grown to be the largest wastewater treatment organization in Iowa and that has historically led to one major problem finding enough qualified employees to operate and maintain the treatment facility that serves half a million residents. In 2008, the Des Moines Wastewater Reclamation Authority (WRA) became one of the first municipalities in Iowa to take advantage of a Department of Labor (DOL) apprenticeship program by Iowa Association Municipalities (IAMU). The apprenticeship program was started because the WRA was struggling to find certified operators to hire. The job required that operators have an Iowa Grade 2 Wastewater Certification, and when a qualified candidate realized that they would be working overnights or evenings, they typically turned down the offer. With an apprenticeship, there are defined milestones that must be achieved in a timely manner, which allowed WRA managers to hire under-qualified candidates that would be required to complete the apprenticeship. Program Details The apprenticeship program is three years long in duration, it requires each apprentice to complete six thousand hours of on-the-job training and pass seven community college treatment and maintenance classes (with a C grade or better). Additionally, they must achieve their Iowa Grade 1 Wastewater Certification within the first year of employment, Class A CDL within two years and their Iowa Grade 2 Wastewater Certification by the third year. New hires that have pervious experience in the wastewater treatment field can receive previous experience credit for up to fifty percent of the on-the-job training hours. New employees that have already completed the any of the seven required classes will receive credit for them. With the acceptance of previous experience credit and classes previously taken, more experienced employees can be fast tracked while less experienced are allowed ample time to learn the ins and outs of working in the wastewater industry. When starting the apprenticeship program, WRA management created the position of Wastewater Training Specialist, in part to assist in the in the training of new Wastewater Operator Specialist employees. The first two apprenticeships classes (2009 & 2011) were held in conjunction with IAMU. The required classes were held at the facility with apprentices completing correspondence classes at Kirkwood Community College (Cedar Rapids, IA). After the 2011 apprenticeship class, the WRA brought the administration of the program internal and started to send apprentices to classes at Des Moines Area Community College (DMACC). DMACC just recently (2012) started to offer water and wastewater treatment classes in a traditional community college fashion with online, in-person or blended classes. According to Craig Hennager and Lori Card of DMACC, 'Apprenticeship students at times were 50% of the enrollment in the overall program. They kept the academic program viable as we grew and developed additional curriculum, establishing ourselves in Iowa as Water and Wastewater training leaders. Together we are making a difference.' Apprenticeship Success Since the inception of the apprenticeship program, there have been a total of thirty-seven apprentices. Of that total number, 30 have completed the program, with 23 still employed at the WRA. An additional five are currently in the program which leaves only two out of 37 that started and did not complete the program. As the program has continued, the WRA has discovered that the learning did not end at completion of the Apprenticeship Program. Out of the 30 to complete the apprenticeship, 19 have eventually achieved Iowa Wastewater Certifications 3 or 4 which is above and beyond the scope of the program. WRA's leadership in workforce development has helped staff advance their training and certification, DMACC to establish their Water Environmental Technology 2-year AA degree, and the local partner organizations like the Des Moines Water Works have followed suit to create an apprenticeship program for their water treatment operators. This program has been vital to the important job of providing qualified staff for the largest wastewater treatment facility in Iowa that is crucial to serves approximately 500,000 residents in Central Iowa.

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

In July 2019, a summer thunderstorm dropped up to 5.3 inches of rain in one hour over some parts of Fairfax County (up to a 1,000-year storm event), causing a reported 149 house flooding and at least $15M in damages. Studies continually show that these high intensity, short duration storms will become more frequent with climate change. The County had also recently enacted the One Fairfax policy, which states that departments must consider equity in the decision-making, development, and delivery of future policies, programs, and services. To comprehensively address flooding concerns, build resiliency into the stormwater network, and further the One Fairfax policy, the County pursued a more objective and equitable approach to flood mitigation by focusing on risk. At the time, Fairfax County's approach to flood mitigation was largely reactive. Flooding was identified through reported complaints. The County prioritized structural flooding adjacent to county easements and infrastructure and public flood mitigation projects were mostly at the individual lot level. The County recognized there were challenges with this method- residents did not always report flooding, older neighborhoods that developed prior to stormwater management standards often lacked public stormwater infrastructure or easements, and the approach offered few options for residents living in the floodplain. The County wanted to be more proactive and ideally address drainage issues before they caused flooding. Staff sought to develop a Geographic Information Systems (GIS) based flood risk map to meet multiple County needs. The map would help staff to select and prioritize capital improvement projects based on the frequency and impact of flooding. Regulators could utilize the data to inform plan review and code requirements. A public facing component could educate both residents and developers on a property's flood risk and an associated dashboard could track flood mitigation and resiliency metrics. Finally, the map would also build the foundation for a comprehensive flood risk reduction plan by helping County leadership and elected officials visualize the scope, cost, and timeline, to mitigate flood risk at a countywide scale. Fairfax County covers 395 square miles and does not have a comprehensive stormwater pipe capacity model. Staff recognized, however, that many of the conditions that make properties more vulnerable to flooding could be identified through existing GIS data. Stormwater management engineers worked together with GIS staff to develop a map to assess flood risk. The first version of the map used a parcel's location and proximity to ten potential flood hazard conditions to evaluate flood risk. Criteria included the following: structures within 30 feet of a FEMA floodplain, structures within 30 feet of a County recorded floodplain, structures in a 25-foot stream buffer, parcels with flooding or drainage-related complaints, parcels located in sumps, structures located in sumps, parcels in a subdivision older than 1972 (the year the County enacted stormwater management standards), residential infill lots (where older homes were torn down and replaced with much larger homes often lacking stormwater management), parcels located in subdivisions without stormwater quantity control facilities, and parcels located in subdivisions outside of stormwater facility drainage areas. Each criterion earned a parcel a score of one, with a total maximum score of ten. Over 350,000 parcels went through the selection process and were scored. Scores for each criterion were available at the parcel level, while total scores were available at the district or county scale as a heat map where the brighter color represented a higher flood risk. After reviewing the results, staff recognized some challenges with this first version of the map. The scoring double counted some of the risk factors. For example, a structure located in the FEMA floodplain, often also received points for being located in a County recorded floodplain and within the stream buffer. The scoring method also lumped fluvial and pluvial flooding together, making it difficult to evaluate the scope and cost of potential flood mitigation solutions. Perhaps most importantly, the map did not clearly and concisely convey flood risk to a lay audience, including both residents and county officials. A revised map narrowed the risk factors to the three main causes of flooding in Fairfax County- proximity to a floodplain, located in a sump condition, and the lack of overland relief. To identify these conditions, staff developed two flood risk analysis tools. The Potential Sump Conditions and Overland Relief Flow Accumulation Layers are the result of analysis performed on a Light Detention and Ranging (LiDAR) derived Bare Earth Digital Elevation Model. The Potential Sump Conditions layer highlights locations of sumps, or bowl-shaped depressions, where water pools and is unable to drain without flooding a structure. Flooding can also occur when there is a stormwater inlet in the sump, but it is overwhelmed due to the magnitude of incoming flows. The layer includes the volume and three-dimensional surface area of the sump. The Overland Relief Flow Accumulation Layer helps to visualize the natural overland runoff flow paths, including paths into and out of sumps. The flow path is strictly based on the bare earth elevation. This provides a clear picture of where the water flows when there is no stormwater management in place, or the infrastructure is overwhelmed. Using these tools, staff developed a revised flood risk map that analyzed four flood risk scenarios. Scenario One established a baseline by identifying all existing reported structural flooding. The second scenario highlighted structures in or within 15 feet of a mapped FEMA or County floodplain. Scenario three noted structures that intersected with or were fully contained within the Potential Sump Conditions Layer, where the sump depth was greater or equal to a foot and the overland relief drainage areas was greater than an acre. The final scenario noted structures that intersected the Overland Relief Flow Accumulation Layer where the drainage area was ten acres or greater. Staff then used the Fairfax County Vulnerability Index to apply an equity lens to flood risk. The Vulnerability Index is comprised of scores from several indicators from the American Community Survey data and ranks vulnerability low to very high on a census block scale. By overlaying the Vulnerability Index, staff identified the most vulnerable communities that were also more susceptible to flooding. Upon identifying these flood-prone neighborhoods, staff wanted to engage with the community to better understand their flood risk. Additionally, staff sought to increase resident awareness of its programs and services in these historically underrepresented communities. To do so, staff worked with a consultant to produce an Equitable Stormwater Management Engagement Framework (Framework) that outlines a systematic process for gathering input on flood mitigation needs and establishing new community relationships. The Framework's purpose was to create more inclusive, equitable, and authentic community engagement to ensure all voices are welcome in the County's planning and decision-making process. The document established a roadmap to achieve the following objectives- equitable consideration of flooding concerns without favoring one population over another, consideration of the vulnerability index and other factors, learning community issues and priorities, building trust with the community so residents feel comfortable contacting the County when issues arise, and understanding community values and priorities as they relate to stormwater and flooding. The Framework is intended to be living document that is updated as the County gathers lessons learned from its collective community of practice. In Spring 2023, the County plans to embark on the next phase of their flood risk reduction strategy. An interdepartmental workgroup will begin outlining a comprehensive flood mitigation plan that will include recommendations for a proposed Capital Improvement Plan project prioritization methodology, updated regulations for development and redevelopment, and programmatic solutions that will lead to a safer community and minimize property damage. Staff will also pilot the Framework guidelines by spearheading a targeted flood risk community outreach and engagement campaign in a highly vulnerable and potentially flood-prone neighborhood. Staff will continue to coordinate flood risk reduction strategies with Resilient Fairfax, a program to help County residents become more resilient to changing conditions and climate change-related hazards. This shift to a more objective and equitable flood risk approach will set the County up for a safe and more resilient future.

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

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

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

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

This paper and presentation will survey and analyze the latest lawsuits and regulatory developments affecting the beneficial use of biosolids, including compost, to provide wastewater and residuals professionals current information that will help inform their decisions on risk, liability, management, and planning. Slaughter and Silton regularly defend land application in litigation, and counsel both POTWs and biosolids service providers on regulatory issues. The speakers will discuss the challenges posed by local ordinances, tort litigation, and the ongoing campaign to regulate per- and polyfluoroalkyl substances (PFAS) in biosolids and groundwater. This talk will outline potential risks, while also highlighting strategies for managing land application and discouraging attacks on beneficial use in the face of a changing legal environment and local communities that may be hostile to land application. Slaughter and Silton will first address the dynamic and problematic regulatory landscape for land application, highlighted by Maine's ban on land application because of trace PFAS. Federal, state and local legislators and regulators, at the behest of many advocacy groups, have turned their focus to PFAS and other trace chemicals that may be found in biosolids. These efforts have spurred regulators to take a variety of actions, including EPA's September 2022 proposal to designate two PFAS-PFOA and PFOS-as hazardous substances under the federal Superfund statute. If the proposal is adopted as a final rule, it could pose risks to land appliers and POTWs. Silton and Slaughter will survey recently regulatory developments and their implications for POTWs, biosolids service providers, and farmers, including ongoing litigation challenging some of the stringent PFAS regulations. Slaughter and Silton will also address the interplay between state and local regulation by exploring several case studies involving local attempts to restrict or ban land application. Their discussion will cover California, where decade-long litigation over a local biosolids ban resulted in a trial and settlement striking down the ban. City of Los Angeles v. Kern County, 2017 WL 1292822 (Tulare Co. Super. Ct. Mar. 14, 2017). Notably, the Kern trial resulted in findings that land application poses few risks after hearing evidence concerning minimal concentrations of PFAS in soil and groundwater beneath a farm where biosolids had been land applied for decades. The speakers will also address recent developments in other states, including Pennsylvania, where the speakers recently challenged enforcement of a local waste ordinance against land application. Second, the speakers will survey risks to land application posed by tort lawsuits. The risk of tort lawsuits based on trace PFAS in biosolids, soil, and groundwater will be examined. Cases in which plaintiffs' lawyers have alleged nuisance conditions caused by land application will be discussed, including the important decision of the Pennsylvania Supreme Court in Gilbert v. Synagro Central, LLC, 131 A.3d 1, which ruled that farming with biosolids is a normal agricultural operation entitled to protection under Pennsylvania's Right to Farm Act. The presentation will conclude with how stakeholders in land application-POTWs, contractors, and farmers-can collaborate to reduce their risks and navigate a challenging, dynamic legal and regulatory landscape.

To transition toward cleaner energy production, Alliant Energy embarked on the development of the most environmentally friendly, natural gas-fired energy facility in the Midwest. The newly constructed West Riverside Energy Center (WREC) provides enough power to support more than 550,000 homes in the region. Located on a 90-acre site in Beloit, Wisconsin, the WREC became the first Envision Platinum-verified project in Wisconsin by following the Institute for Sustainable Infrastructure's framework for assessing sustainability, resiliency, and equity in infrastructure. The planning, design, and construction of the WREC leveraged Nature-Based Solutions to restore natural systems on the site. The project restored nearly 67 acres of natural environment surrounding the facility through the conversion of agricultural cropland to native prairie grasses and wildflowers, creating new habitat and improving habitat connectivity. In addition to the landscape restoration, the project was designed to mimic pre-development hydrologic conditions. Innovative techniques, including stormwater harvesting and re-use for process water, stormwater pond retrofits, and treatment train including rain gardens and bioswales helped the project achieve the Restorative designation for stormwater management, becoming the first Envision-certified project to reach this performance standard, in which stormwater management was not intended as the primary purpose of the project. The WREC manages nearly 170 acres of stormwater runoff through best management practices (BMPs) that include vegetated swales, a 1-acre infiltration basin with engineered subsurface media, 5,000 gallon stormwater harvest and re-use cistern, and land use conversion. HydroCAD and WinSLAMM were used to model project performance, indicating that event-based peak flow rates would decrease between 14% to 20%, and the property would reduce stormwater runoff by 65,000 CF on an average annual basis. WinSLAMM estimates that total suspended solids (TSS) will be reduced by 84% on an average annual basis as a result of the stormwater design. The design achieved ISI's Restorative designation for stormwater management by maintaining or improving pre-developed hydrologic conditions and retaining or repurposing more than 100% of the pre-development infiltration capacity of the site. These stormwater solutions complemented WREC's One-Water approach for the site. The facility minimized water consumption by implementing unique water treatment solutions, re-using water within the facility, and treating wastewater prior to discharge to the Rock River. A process water pre-treatment system allows for 8 to 10 cycles of process water concentration, compared to an industry typical standard of 4 to 5 cycles of concentration from untreated well water. The team also utilized a land management approach outside of the main building as part of a Phosphorus Trade Agreement to meet or exceed Wisconsin's nutrient discharge requirements. Co-benefits associated with WREC development and sustainable water management include a new multi-modal trail connection to a 12-mile walking, hiking, and biking trail. A 4 MW solar field was constructed to provide the generating station with the ability to quickly and efficiently adjust for power demands in real time. An energy lab provides an interactive forum for public education to communicate the benefits of the prairie restoration and renewable energy production. By following the Institute of Sustainable Infrastructure's sustainability framework, the WREC was completed under budget, and the facility was online in time for increased summer power demand. Successful planning, design, and construction of the WREC serves as a model for Nature-Based Solutions and sustainable water management in the Midwest. This presentation focuses on project goals, regulatory and design criteria management, modeling, design, and results. By implementing a one-water approach and nature-based solutions, this award-winning project incorporated sustainable water and environmental practices to contribute toward Envision Platinum verification.

Background Wastewater Treatment Plants (WWTPs) in South Carolina and Georgia have been historically dependent on landfill disposal for the management of the wastewater solids generated through their respective treatment processes. In Georgia and South Carolina nearly 65% of wastewater solids are sent to landfill. In recent years, landfills in both states have undergone policy changes that include steep increases in tipping fees for wastewater solids and a reduction in wet waste acceptance. The reduction of wet waste acceptance limits the percent wet waste (>40% moisture) accepted into landfills. In Georgia, landfills are required to develop a detailed Sludge Management Plan (SMP) if they accept more than a 5% wet waste to 95% Municipal Solid Waste (MSW) ratio. The changing landscape surrounding landfill disposal creates significant challenges for WWTPs in both states. The uncertainties resulting from these changes have served as the impetus for four WWTPs (two in Georgia and two in South Carolina) to evaluate new biosolids management technologies, beneficial use markets, and management methods. Objective Four utilities located in Gainesville, GA, Douglasville, GA, Beaufort, SC, and East Richland, SC underwent Biosolids Regulatory and Market Assessments for their respective WWTPs. The assessment worked to identify opportunities and challenges resulting from state regulations, local markets, and corresponding economics, associated with managing various biosolids products under consideration. Comprehensively, the Regulatory and Market Assessments for all of the utilities serve as a guide to the biosolids beneficial use and disposal outlets and management methods to achieve the following three objectives. 1. Identify permitting pathway for several biosolids products and management methods in Georgia and South Carolina; 2. Identify beneficial use and disposal outlets in the region for the respective baseline products generated by each WWTP; 3. Identify beneficial use and disposal outlets in the region for proposed products; and 4. Define market details including market capacity, storage requirements, and revenues and expenses associated with product management. Methodology The Biosolids Regulatory Assessments included a detailed review of existing Federal and state biosolids beneficial use and disposal regulations, as well as future regulatory federal and state regulatory considerations. Encompassed in the Market Assessment for each utility, the baseline solids management program was examined to understand existing practices and costs associated with solids disposal. Information about the local market preferences and demand for the biosolids products being considered for each utility was gathered through market research and interviews with potential market outlets. Collected data was used to identify the opportunities, challenges, and outside-the-gate program expenses (those expenses associated with product management only) associated with each market/product combination. The data from each utility was further analyzed to develop an idea of the current biosolids beneficial use and disposal trends relating to the management of several biosolids products in both South Carolina and Georgia. Four main products were evaluated including Class B digested cake, Class B and A/EQ alkaline stabilized cake, Class A/EQ compost, and Class A/EQ thermally dried granules. Findings and Current Status Assessment findings reveal that the development of beneficial use programs, both self-managed programs (SMP) and Third-Party Contractor (TPC) managed programs are available and viable in South Carolina and Georgia. Listed below are the main recommendations and findings that were consistent for each Market Assessment: 1. High Level of Interest in Class A/EQ Thermally Dried Granules: In each Market Assessment, thermally dried granules scored higher than other products due to the high level of interest noted in outlet surveys as well as the increased product flexibility within several different markets. Although interest level is high, many interested market outlets require a high-quality product, which is typically generated from rotary drum dryers. 2. Availability of Off-Site Stabilization Facilities: Off-site stabilization facilities are currently available with more coming online in the coming years. The majority of stabilization facilities in Georgia and South Carolina are composting facilities which product Class A/EQ compost for several markets. 3. On-Site Storage Requirement: 3 months of on-site storage is highly recommended, regardless of which market/product combination is pursued. The increase of on-site storage presents each utility with increased flexibility and resiliency. A summary of the selected products, most promising markets, relative outside-the-gate costs, opportunities, and considerations are summarized in Table 1. Furthermore, a summary of the regulatory considerations for Georgia and South Carolina can be found in Table 2. The Market Assessment findings indicate the current market conditions are strongly favorable for beneficial use of Class A/EQ compost and dried granule biosolids products. The presentation will further discuss the relative outside-the-gate costs associated with the management of each product as well as growing trends relating to the beneficial use of biosolids in this region.