Portiolli, Giovanna

Giovanna earned her Bachelors Degree in Environmental Sciences from Winthrop University and a Masters Degree in Environmental Engineering from North...

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About Portiolli, Giovanna

Giovanna earned her Bachelors Degree in Environmental Sciences from Winthrop University and a Masters Degree in Environmental Engineering from North Carolina State University. She worked in consulting before joining Charlotte Water in 2023 as a leader of the biosolids and residuals program, and today serves as the Resource Recovery Manager for the ultility.

Portiolli, Giovanna

Titles from this speaker

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Alternative Approach to Accelerate Beneficial Biogas Utilization and RNG Production

Abstract

Charlotte Water (CLT Water) is the largest public water and wastewater utility in the Carolinas, serving more than one million customers in the City of Charlotte and greater Mecklenburg County. Charlotte Water currently owns and operates five major water reclamation facilities (WRFs), treating an average of 325 million liters per day (ML/d) or 86 million gallons per day (MGD) of wastewater and is in design for a sixth plant, the Stowe Regional Water Resource Recovery Facility (WRRF). Stowe Regional WRRF will treat flows from the western portion of Mecklenburg County and will also accept and treat flow from two neighboring towns in a bordering county. The Stowe Facility will have the capacity to process 68 ML/d or 15 MGD of wastewater, which will eventually grow to 114 ML/d or 25 MGD. CLT Water has a phased regionalization program in place for consolidation of biosolids treatment at McAlpine Creek Wastewater Management Facility (McAlpine Creek WWMF) as shown in Figure 1, which includes solids conveyance projects and the design and construction of a thermal hydrolysis process (THP) system for pre-treatment of solids prior to anaerobic digestion. CLT Water completed a Biogas Production and Utilization Study for the McAlpine Creek WWMF in September 2020. This study projected expected biogas production at McAlpine Creek WWMF taking into account the regionalization of solids treatment and the installation of THP. The combined regionalization and digestion improvements are anticipated to increase biogas production to approximately 1,930 normal cubic meters per hour (Nm3/h) or 1,200 standard cubic feet per minute (scfm). These projected biogas production values were used to generate a bioenergy model to evaluate multiple alternatives for beneficial biogas utilization including Combined Heater and Power, Steam Generation for THP, Compressed Natural Gas (CNG) fueling, and Renewable Natural Gas (RNG) pipeline injection. The bioenergy model, shown in Figure 2, considered capital and lifecycle costs of each alternative and produced dynamic comparisons of the different alternatives based on varying assumptions and user inputs. A non-economic evaluation was also used to compare the biogas utilization options, including safety, risk and O&M considerations, bioenergy utilization, private development opportunity, and public relations. The outcome of the study was a recommendation to implement RNG pipeline injection as this would allow for the largest percent utilization (99%) of the biogas and the most flexibility to operations, while aligning closely with the City of Charlotte's Strategic Energy Action Plan (SEAP). Following completion of the Study, CLT Water proceeded with a competitive sale process, viewing the biogas as a personal property to be sold as a commodity to a buyer to be converted to RNG and soliciting sealed bids from project teams to implement the RNG strategy. As a condition of the sale, the potential buyer was required to provide a 'turn-key' solution for the utilization of the biogas by providing the buyer's own capital, facilities, design, construction, operation, management, and permitting services necessary to convert the biogas into RNG. The buyer will perform conditioning of the biogas and resell the resulting product gas as RNG, which will create Renewable Identification Numbers (RINs) that can be monetized via the federal RIN market as well as state level credit markets. The buyer will have the rights to all environmental credits/attributes such as renewable energy certificates, low carbon fuel standard credits, and other similar entitlements associated with the RNG. Figure 3 shows an arrangement of the proposed biogas utilization program. CLT Water conducted the following two solicitation steps in order to enter into an agreement for the sale: 1)Request for Proposals (RFP): Utilized to short-list qualified companies taking into consideration vendor qualifications and experience, demonstration of safe RNG operation practices, quality, delivery, workmanship, and any applicable environmentally preferable attributes associated with the company's proposed solution for RNG. The short-listed companies were qualified to receive an Invitation to Bid. 2)Invitation to Bid (ITB): sealed bid sale where short listed companies have an opportunity to provide CLT Water their best price for the purchase of unconditioned biogas within a defined cost framework. This procurement approach encouraged competition in the determination of the biogas value and efficiency of proposed solutions. CLT Water has completed the RFP and ITB stages, selected the highest responsive, responsible bidder, and are currently undergoing final contract negotiations which include a land license for the facility construction inside CLT Water property and an offtake agreement for the delivery of biogas. Design of the facility is expected to commence in Spring 2025 and is anticipated to be sized for 1,930 Nm3/h (1,200 scfm). The system will be capable of removing hydrogen sulfide (H2S), volatile organic compounds (VOCs), siloxanes, and carbon dioxide (CO2) to meet pipeline specifications. The presentation will summarize the history of the biogas utilization study, development of the RNG implementation approach, and highlights of design efforts completed at the time of the conference.

This paper was presented at the WEF Residuals & Biosolids and Innovations in Treatment Technology Joint Conference, May 6-9, 2025.

SpeakerPortiolli, Giovanna

Presentation time

10:15:00

10:35:00

Session time

10:15:00

11:45:00

SessionAdvancing Biogas and RNG: Innovations and Regulatory Challenges

Session number26

Session locationBaltimore Convention Center, Baltimore, Maryland, USA

TopicAerobic Digestion, Alternative Delivery Systems (Design-Build-Operate-Transfer), Biogas, Biogas To Biomethane, Biogas Utilization, Greenhouse Gases, Heat recovery, Renewable Natural Gas

Author(s)

Portiolli, Giovanna, Schaich, Laurel

Author(s)G. Portiolli1, L. Schaich2

Author affiliation(s)Charlotte Water, 1CDM Smith, 2

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2025

Volume / Issue

Content sourceResiduals and Biosolids Conference

Word count11

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Harvest Time is Here! -- Biosolids' Unspoken Role in Improving Our Declining Soil Health -- A Literature Review to Enhance Communication Tools for Biosolids Managers

Abstract

As utilities increasingly focus on implementing a circular economy, wastewater treatment plants' (WWTPs) byproducts are no longer viewed as waste, but valuable resources. Biosolids are a nutrient-rich recovery product that can be used as soil amendment, promoting sustainable agriculture, enhancing soil health, and ensuring the recycling of nutrients. Utilities aim to produce high quality biosolids and promote its beneficial use as they also undertake the crucial task of educating and informing farmers along with the general public on potential misconceptions regarding environmental and public health risks associated with biosolids land application. This scenario presents a great opportunity to partner with the farming community and establish open communication channels to overcome the often negative stigma associated with biosolids. Such partnership must include science-based information supported with data obtained from current research to respond to public concerns. Understanding the stakeholder concerns also helps identify future research needs, such as which crop types and soil classes to focus on, what parameters are of higher concern to stakeholders, and how to balance the priorities of different stakeholders. To help strengthening the communications, there is a crucial need to compile and interpret current scientific research on this topic and help utilities with their message based on scientific data. The beneficial impact of biosolids on soil health can be overshadowed by the increasing research on contaminants of emerging concern that is expected to be regulated. While there is a rapidly growing body of research on the treatment, fate and transport of potential contaminants in biosolids, measuring the impact of the biosolids application in agricultural settings requires long time frames. Additionally, the lack of a standardized framework for evaluating the soil health and reporting results and the variability based on region, types of crops studied, type of biosolids applied, and the parameters measured can make interpretation challenging. For farmers, the most important asset to provide nutritious crops and to generate high yields is the soil they are tending. Unfortunately, soil erosion, compaction, heavy use of synthetic fertilizers and pesticides have been the culprits of declining soil quality on the farmlands. In the United States alone, soil erosion costs the US $8 billion each year and reduces the agricultural food production by 33.7 million metric tons per year (Martina Sartori, 2019). Soil health can be improved if certain management practices are routinely incorporated into agricultural management such as minimal tillage, cover crops, reduced use of synthetic fertilizers and pesticides. There is a growing interest in finding ways to improve soil health first and foremost rather than focusing solely on increasing yields through chemical inputs. US Department of Agriculture's Natural Resource Conservation Service has been implementing best practices in this area, working with the farmers to improve not only soil health but also water quality in areas where farmland makes up much of the land in the watersheds. (USDA, 2024). The authors believe that biosolids can be an important part of the conversation seeking to improve and reverse the ongoing condition of degrading soils. Despite the growing concerns regarding contaminants of emerging concern in biosolids, on-going research will take time to come to a definitive and realistic conclusion. Until then, 'all-or-nothing' approach for land application will mean the reduced or eliminated use of a valuable resource to implement a better soil health practice. The authors have run a data query on SCOPUS, which is a Science Direct service for analyzing only peer-reviewed journals and cited research. The research on biosolids and soil has been going on since 1980s (Figure 1 and 2) but not until recently that we see the soil health aspect and term incorporated in it (Figure 3). Now that 'how and why' of soil ecosystem functionality is better understood, further actions can be implemented. Initial literature review efforts have already shown that the biosolids application increases soil carbon, microbiology, aggregate stability and decreases bulk density of soil (Ippolito James A., 2021) (Bolan N.S., 2013) (Villa Y., 2021) (Ippolito J.A., 2024). Nutrient management and recycling are also heavily researched as biosolids can act as a slow-release fertilizer, replacing the conventional, synthetic fertilizers that doesn't contribute to improving soil health. There is also research and discussion taking place across the soil community as to which parameters really are indicative of soil health and trying to establish a framework for the farmers to make evaluation easier and comparable across the sites (Bagnall D.K., 2023) (Liptzin D., 2022) (Rieke E.L., 2022). With this paper, the authors' goal is to complete thorough literature research on biosolids impact on soil health parameters in agricultural settings. We aim to detail the following as it pertains to the agricultural application of biosolids to the practical extent possible to provide water and wastewater utilities with a comprehensive literature review: - A map of the US showing where research has been undertaken. - A table summarizing and comparing research methodologies (crops, trial settings, biosolid types). - A summary of the findings and trends (soil health parameters measured, emerging contaminants of concern, timeframes, etc.). - Funding sources to support research. - Potential future research areas. - Contributions of research to existing biosolids management strategies At the end of this literature research, the authors will summarize previously completed research efforts and up-to-date results which will serve as an important tool to utilities as they develop and implement communication plans that support a sustainable management of biosolids programs. The literature research will also help utilities in their efforts to measure their contribution to soil health in their land application sites. The authors will evaluate the past soil test results from their current application sites, and identify control sites that can be sampled to make comparisons. Based on the initial findings, soil parameters and sites will be determined for the next steps of the localized research effort. The results will inform the communication tools with the farmers as well as the public.

This paper was presented at the WEF Residuals & Biosolids and Innovations in Treatment Technology Joint Conference, May 6-9, 2025.

SpeakerErdogan, Ilke

Presentation time

13:30:00

13:50:00

Session time

13:30:00

15:00:00

SessionNavigating Land Based Biosolids Management

Session number16

Session locationBaltimore Convention Center, Baltimore, Maryland, USA

TopicAerobic Digestion, Agriculture, Biosolids, Data Management, Decision Making, Market Development, PFAS/Emerging Contaminants, Risk Assessment, Soil Health, Stakeholder Engagement, Utility Management

Author(s)

Erdogan, Ilke, Portiolli, Giovanna, Steele, Muriel, Lockler, Joseph

Author(s)I. Erdogan1, G. Portiolli2, M. Steele2, J. Lockler2

Author affiliation(s)Stantec Inc., 1Charlotte Water, 2

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2025

Volume / Issue

Content sourceResiduals and Biosolids Conference

Word count26

Description: Troubleshooting VSR: A Multi-Approach Strategy Towards Significant Operational...

Troubleshooting VSR: A Multi-Approach Strategy Towards Significant Operational Savings

Abstract

Charlotte Water (CLT Water) is the largest public water and wastewater utility in the Carolinas, serving more than a million customers in the City of Charlotte and greater Mecklenburg County. CLT Water owns and operates five major wastewater treatment plants (WWTPs) with an average treated flow of 78.1 million gallons per day (mgd). Additionally, CLT Water oversees one of the largest class B biosolids programs in the southeastern United States, operating with 17,000 acres of permitted agricultural land in both North and South Carolina and producing over 100,000 wet tons (WT) of biosolids annually. CLT Water's largest WWTP is McAlpine Creek Wastewater Management Facility (McAlpine Creek), with an average treated flow of 41.3 mgd and 60,000 WT of biosolids produced annually. There are three major regulatory categories that are required in order to meet the Class B land application biosolids standards: (1) metals concentrations, (2) vector attraction reduction, and (3) pathogen reduction. This paper will focus on volatile solids reduction (VSR) - the vector attraction reduction alternative CLT Water uses to meet land application standards, the financial impact of a sudden failure to meet the VSR requirements, and the troubleshooting and optimization steps taken to address the issue experienced and to improve the overall solids treatment process. McAlpine Creek is a regional solids processing facility, which in addition to treating the solids produced at the plant, it also receives primary sludge (PS) and waste activated sludge (WAS) from the Sugar Creek WWTP (Sugar Creek) for treatment. McAlpine Creek is designed to receive primary solids from Sugar Creek through a dedicated force main, which connects to McAlpine Creek's primary solids gravity thickeners (GTs), while WAS from Sugar Creek, also designed to be pumped through a dedicated force main, connects to a combined WAS well at McAlpine Creek. Even though the infrastructure exists for Sugar Creek PS and WAS to enter directly into McAlpine's solids treatment train, due to a history of hydraulic overloading of the GTs, Sugar Creek's PS and WAS were being sent through gravity sewer lines and entering McAlpine Creek through the influent flow. McAlpine Creek solids treatment train currently consists of primary clarification, primary sludge gravity thickening, WAS centrifuge thickening, anaerobic digestion of thickened primary sludge (TPS) and thickened waste activated sludge (TWAS), and finally centrifuge dewatering of digested sludge. CLT Water meets the vector attraction reduction requirement by achieving a minimum of 38% VSR through the anaerobic digestion calculated on a monthly basis. Typically, McAlpine Creek achieves the minimum VSR requirement with a comfortable buffer, achieving around 45% VSR, without any major issues. In July 2022, operational staff became alarmed when they noticed a trending decline in VSR results prompting the need for immediate operational changes to be made. The efforts however were not enough to avoid a VSR failure of 36% in July 2022, which prevented CLT Water from land applying the biosolids. Instead, CLT Water had to landfill the entire July biosolids production, totaling over 4,000 WT which cost the City approximately $500,000. Operational efforts to troubleshoot the problem continued for several months past July 2022 with improved success later in the fall and through the same summer period of 2023. The main strategies implemented were: (1) digester feed optimization by improving performance of gravity thickeners, (2) VSR calculation method evaluation, and (3) data tracking and proactive sampling. Improving GT performance included adjusting pumping flow rates, throttling existing valves, and replacing malfunctioning valves from primary clarifiers to GTs to improve PS % solids from <0.5% to 1.0-1.5%. Another significant change was reverting the Sugar Creek PS and WAS transport and tie in points to their original design (PS connected to GTs and WAS connected to a combined WAS well), Sugar Creek's solids were no longer going to McAlpine Creek's influent. Additional optimization trials included actions related to polymer use, configuration of duty/standby GTs, and installation of TSS probes and VFDs on Sugar Creek's PS pumps to McAlpine Creek. While a few of the optimization trials did not cause any improvements, several of the strategies yielded positive results and improvements of PS thickening, digestion, and consequently, volatile solids reduction. CLT Water staff went beyond operational changes and started evaluating the VSR calculation method used by the CLT Water biosolids program for many years. There are two main allowable VSR calculation methods including, approximate mass balance and Van Kleeck. CLT Water uses the latter method. After initial research, staff learned the Van Kleeck calculation underestimates the VSR whenever there is grit accumulation inside digesters. Several digester cleanout projects at various WWTPs were performed over the last ten years including at McAlpine Creek confirming that significant grit accumulation does occur inside CLT Water's digesters. With this information, CLT Water started calculating VSR using both methods and tracking the results side by side. The evaluation showed that the approximate mass balance method yields a slightly higher VSR result and proved to be more representative of CLT Water's process due to the proven grit accumulation. Finally, based on the VSR calculation method evaluation, CLT Water decided to more closely monitor percent solids going into the digesters to predict any potential issues sooner, giving staff adequate time to make operational changes to avoid future failures. Additionally, CLT Water found it to be beneficial to run an EPA-approved alternative test (40-day anaerobic digestion bench test) during months that the percent solids based on historical trends were expected to decline. The 40-day digestion bench test was performed in August 2022, as an immediate response to the July 2022 VSR failure, and proactively conducted in the Summer of 2023. By continuing to perform the alternative test early in the months known to suffer from percent solids falling-off, if by the end of the month the calculated VSR results do fail, staff can use the results from the 40-day digestion bench test to meet the EPA requirements and potentially not interrupt any land application operations and incur unexpected landfill costs. This paper will detail out the multi-approach strategy taken by CLT Water staff to troubleshoot and optimize processes around thickening, anaerobic digestion, and VSR calculation which resulted in many lessons learned, benefits around the overall solids treatment processes, and significant cost savings in the biosolids beneficial reuse program.

This paper was presented at the WEF Residuals and Biosolids Conference, June 18-21, 2024.

SpeakerPortiolli, Giovanna

Presentation time

08:30:00

11:15:00

Session time

08:30:00

11:15:00

SessionTroubleshooting & Optimization

Session number26

Session locationOklahoma City Convention Center, Oklahoma City, Oklahoma

TopicClass B Biosolids, thickening, Volatile Solids Reduction

Author(s)

Portiolli, Giovanna

Author(s)G. Portiolli1, M. Steele1

Author affiliation(s)Charlotte Water1; Charlotte Water 1;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Jun 2024

DOI10.2175/193864718825159456

Volume / Issue

Content sourceResiduals and Biosolids Conference

Word count10

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Portiolli, Giovanna

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