Sierra, Natalie

Natalie Sierra is the National Practice Lead for Solids and Energy at Brown and Caldwell in Andover, MA. A professional engineer with over 20 years of experience, she spent the earlier part of her career as the biosolids manager for the San Francisco Public Utilities Commission, and she brings her utility perspective to helping others in both long and short term biosolids and organics planning and management. She has been deeply engaged at the local and national level on regulatory issues associated with PFAS, including NEBRA and WEF.

Titles from this speaker

Description: Employee Network Groups as Engines for Change: How Candid Conversations Around...

Employee Network Groups as Engines for Change: How Candid Conversations Around Gender Create an Authentic and Empowered Workforce

Abstract

Women’s representation has increased significantly in the workforce, yet diversity and true inclusion, including opportunities to advance, remains an issue. In addition to addressing barriers to advancement, the global COVID-19 pandemic has caused many women to leave the workforce, unable to juggle competing demands over the duration of the pandemic. One tool for overcoming the challenges that women face in the workplace is an Employee Networking Group (ENG). The focus of an ENG is to work on the ‘how’ of improving inclusion rather than the ‘what’ of diversity so that as diversity of hiring pools improves, employees feel a sense of belonging, and choose to stay in a given workplace. This paper discusses the founding of the first ENG at our company and lessons learned along the way.

“Employee Network Groups as Engines for Change: How Candid Conversations Around Gender Create an Authentic and Empowered Workforce.” This paper discusses one tool in overcoming challenges that women and minorities face in the workplace – Employee Networking Groups (ENGs). The focus of an ENG is to work on improving inclusion so that as diversity of hiring pools improves, employees feel a sense of belonging and choose to stay in a given workplace. Our paper discusses the founding of our Women’s ENG at our company, the positive changes that have resulted, and lessons learned along the way.

SpeakerSierra, Natalie

Presentation time

11:30:00

11:45:00

Session time

11:00:00

12:30:00

SessionProactive Leveraging of Workplace Diversity, Equity, and Inclusion in Utility and Private Organizations

Session number208

TopicPolicy and Regulation, Research and Innovation, Utility Management and Leadership

Author(s)

Natalie Sierra

Author(s)N. Sierra1; N. Laughlin2;

Author affiliation(s)Brown and Caldwell, Boston, MA 1Brown and Caldwell, Lakewood, CO2

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2021

DOI10.2175/193864718825158043

Volume / Issue

Content sourceWEFTEC

Word count19

Description: Master Planning When the Ground Keeps Shifting: Portland (Maine) Water District's...

Master Planning When the Ground Keeps Shifting: Portland (Maine) Water District's Biosolids Master Planning Experience in the Age of PFAS

Abstract

Background Portland Water District (PWD) has four wastewater treatment facilities (WWTFs) with a capacity of more than 25 million gallons per day. Two of the four facilities - East End and Westbrook process most of the solids in the system and were the focus of PWD's comprehensive approach to assess the current solids system and develop a strategic plan that outlines the necessary upgrades, process modifications, and state-of-good-repair projects that PWD should undertake during the next 20-year planning period. PWD began contemplating this planning effort not only due to aging infrastructure, but rather due to increasing concern over lack of biosolids management options and rising public concern around per- and polyfluoroalkyl substances (PFAS) in biosolids. Throughout New England, decreased biosolids management capacity has been a rising concern. Much of the region relies upon landfills and regional incinerators, but beneficial use (land application) has served as a reliable, sustainable option for a number of utilities. In Maine, land application had been an accepted practice, with good market understanding of the benefits of biosolids, including biosolids based compost and thermally dried products. In 2019, however, PFAS contamination was discovered at a Maine dairy farm that had historically land applied both biosolids and short paper fibers. This led the Maine Department of Environmental Protection (DEP) to promulgate soil screening standards for two PFAS - perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). These screening standards were used to limit biosolids land application rates based on the concentrations of these two compounds, and the understanding that PWD might be able to land apply in the future served as an initial assumption of the study. Shortly after study initiation, the Maine legislature passed LD 1911, which prohibits the land application or sale of biosolids and biosolids-derived products in the state of Maine. While options were already limited before this new law, the only option for biosolids management in Maine is now landfill disposal. The passage of LD 1911 thus focused the biosolids master plan on technologies that significantly reduce volume and/or employ thermal destruction. Methodology The goal of this project is to create a 20-year system-wide implementable plan, including near- and long-term improvements that improve the reliability of PWD's solids handling assets while meeting the project goals of mitigating emerging contaminants risks, enhancing reliability and regulatory resiliency, and increasing the public's confidence in PWD's environmental stewardship. PWD worked with its consultant to create a master plan that has both near- and long-term improvements to improve the reliability of PWD's solids handling. Alternatives were evaluated based on regulatory, financial, social, and environmental goals and objectives. An overview of the master planning process is shown in Figure 1. Custom solids and energy models were created to reflect the operation of East End and Westbrook, which were used to determine alternatives for solids handling. The consultant team also provided PWD with estimated operational and capital costs, solids production, and energy requirements based on actual PWD unit costs. Throughout this process, the PWD and consultant team developed and evaluated seven alternatives at six workshops. The outcome of these workshops was a roadmap with several triggers rather than a final solution due to the uncertainty and expected changes in Maine's regulatory framework. Alternatives were evaluated using a mass and energy balance model that supported evaluation of both technical and operational performance. When combined with the capital investment required for each alternative, the model produces a net present cost (NPC) lifecycle cost of each alternative that, when compared to the baseline process condition, determines its financial viability. For this study, it was assumed that the planning horizon for the project would be 20 years. The alternatives evaluated are: -Alternative 0: Status quo. No operational or capital improvements. -Alternative 1: Modified baseline. Baseline operation with new dewatering and sludge storage. This alternative considers the possibility of sending dewatered solids to a merchant facility or to a landfill. -Alternative 2: Thin film Dryer. Westbrook dewatered solids hauled to East End, and the combined solids are dried in a thin film dryer and then disposed of at a landfill. -Alternative 3: PS AD + thermal dryer. Westbrook dewatered solids hauled to East End. East End primary sludge (PS) only mesophilic anaerobic digestion (AD) with thermal drying of all East End and Westbrook sludge. Landfill disposal with possible beneficial end use options in the future. -Alternative 4: Regional Pyrolysis. Westbrook and East End dewatered solids hauled to a PWD-owned regional pyrolysis facility, with either biodrying or thermal drying. Biochar is beneficially used. -Alternative 5: Regional Solar Drying. Westbrook and East End dewatered solids hauled to a PWD-owned regional solar drying facility. Landfill disposal with possible beneficial end use options in the future. Table 1 presents the results of the NPC analysis for these alternatives at a range of solids management costs, which are the largest contributors to the annual solids handling and processing costs. Note: Pyrolysis alternatives do not increase with rising tip fees, as it was assumed PWD had an agreement with the vendor to take the biochar at no cost. Sludge pyrolysis has not been demonstrated at PWD's size, so PWD decided the uncertainty with this technology was too significant at this high capital cost; therefore, PWD decided to continue to monitor the technology before making a final decision. The remaining alternatives were then evaluated based on non-cost factors including de-risking PWD on end use, sustainability, cost predictability, and improved reliability. Table 2 shows a summary of the goal factors for each of the alternatives. The modified baseline, which centers around improved dewatering, was found to be advantageous under current tip fees, and helps de-risk PWD as tip fee volatility increases. This was considered a 'no regrets' project as it both replaces aging infrastructure, and saves PWD money over the long term. With respect to the other alternatives, external factors, particularly the manner in which Maine DEP does or does not permit certain technologies, will affect which alternative should be implemented. As a result, a roadmap was made with key regulatory, market, and other implementation triggers to help guide PWD's actions in the next five years. The roadmap is presented as Figure 2, with the 'no regrets' project serving as the starting point (e.g. will be implemented). Key triggers will cause PWD to go on a certain path of the map, while additional triggers will further refine the likely or viable options. The final two branches (red and orange) of the roadmap are highly unlikely but could still be an outcome. The three key triggers are tip fees continue to rise, landfills reject biosolids, and tip fees stabilize or drop. This adaptable model allows PWD to make immediate improvements that will result in cost savings (dewatering upgrades and thickened sludge storage), while allowing for planning in the face of continuing regulatory flux. It is anticipated that over the next few years, Maine's regulatory approach will stabilize, clarifying the appropriate path forward. Conclusions While state and federal biosolids regulations are still uncertain, PWD can take the following actions recommended by the master plan: -Engage with regional partners now. Should support exist (both from Maine DEP and peer utilities) for regionalization, PWD and its potential partners would have time to determine challenging aspects of partnership such as governance. -Continue to engage with service providers as they explore merchant regional solutions. The master plan established a range of tip fees at which it could be advantageous for PWD to secure long-term management capacity. -Conduct a preliminary design project for the no-regrets projects at East End and Westbrook. This project would provide PWD with a basis of design report (BODR) in which dewatering technology and location would be selected as well as selection of size and location for sludge storage tanks at East End. The BODR would also include evaluation of conveyance of cake, automation of the screw press, and polymer changes at Westbrook. -Continue to engage Maine DEP on technology updates and data updates on PFAS mitigation. -Explore funding mechanisms and continue discussions with vendors on viable solutions. -Visit dryer and other vendor installations.

This paper was presented at the WEF/IWA Residuals and Biosolids Conference, May 16-19, 2023.

SpeakerSierra, Natalie

Presentation time

11:15:00

11:45:00

Session time

8:30:00

11:45:00

SessionSession 10: PFAS Challenges and Treatment

Session number10

Session locationCharlotte Convention Center, Charlotte, North Carolina, USA

TopicEmerging Issues (PFAS, Microplastics, Covid, etc.)

Author(s)

N. Sierra

Author(s)D. Price1, N. Sierra2, S. Firmin3, T. Chouinard4,

Author affiliation(s)Brown and Caldwell1; Portland Water District2

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2023

DOI10.2175/193864718825158820

Volume / Issue

Content sourceResiduals and Biosolids

Word count21

Description: Thermal Drying Economics: Integrating Market Analysis and Lifecycle Costs to Assess...

Thermal Drying Economics: Integrating Market Analysis and Lifecycle Costs to Assess Thermal Drying Feasibility

Abstract

Introduction In recent years, several regions of the country have experienced skyrocketing biosolids management costs. Though the triggers may be unique to each region, management capacity constraints are at the heart of these trends. Additional factors, such as concerns over PFAS in states like New Hampshire and Maine, have placed additional pressures on an already tight market. As utilities in regions like New England, Metro Atlanta, and the New York-New Jersey metro area are experiencing increases of 50-100% in biosolids management costs, the option of thermal drying may be a logical solution with respect to volume reduction and improved product quality. In several recent projects, Brown and Caldwell has integrated local market analysis, particularly trends in biosolids management costs, with traditional life cycle cost analysis in order to assist utilities in determining whether thermal drying could be a solution to mitigate risk around biosolids management. While no single answer applies, there are markets for which drying simply for volume reduction can curb rapid cost increases today, while other markets (particularly where natural gas costs are high and end use costs are not rising at as rapidly) would not necessarily trigger the need for such an upgrade. We will present an overview of the factors that go into such an analysis, as well as two recently completed case studies with different outcomes. Methodology The analysis begins with the end in mind, by assessing the regional market pricing trends for biosolids management. Opportunities for use of thermally dried products were also assessed at this point, to understand whether market capacity exists regionally for product acceptance. When coupled with costs associated with the current operation, this constitutes the baseline and provides some boundary conditions for a sensitivity analysis around end use costs. Alternatives were then built to incorporate both capital and life cycle costs including additional labor, chemicals, natural gas, and end use costs. Sensitivity analyses were then run live in a workshop setting around areas of risk, including end use and energy costs. Results and Discussion In the first case study, the cost of continued landfill disposal of unstabilized solids was compared against installation of a thermal dryer. Given regional market volatility and shrinking landfill capacity, landfill disposal cost projections were escalated at current (10%) and historic (5%) annual trends. A conceptual dryer design was developed to identify realistic capital and annual operating and maintenance expenditures and assessed over a range of end use scenarios from landfill disposal, contracted land application, sale to specialty markets, and onsite dried product pyrolysis. The lifecycle cost assessment, displayed in Figure 1, demonstrated that (1) thermal drying provided a strong economic benefit at the current rate of landfill disposal cost escalation, (2) thermal drying was economically viable even if landfill tipping fees returned to more steady, historic escalation rates and (3) the resulting volume of dried product did not provide the cost differential required to justify the additional capital expenditure for pyrolysis or added operational and maintenance complexity for pelletizing and bagging operations to sell to specialty markets. In the second case study, solids are already digested to Class B, and management costs are approximately $50/wet ton. When compared against other Class A alternatives, thermal drying was the preferred alternative on a life cycle cost basis. However, with multiple capital upgrades necessary, this utility wanted to assess when the best time — purely from a cost standpoint — would be to upgrade to Class A. Market analysis was used to predict possible cost trends for biosolids management over the next twenty years. Looking at a range of scenarios, shown in Figure 2, the BC team assessed the possibility of constructing a thermal dryer near term, 10 years out, or 20 years out. Given the anticipated rate of change of end use management fees, it was determined that building the project immediately was not necessary. Given the great degree of fluctuation in the regional biosolids market, it was preferred to monitor market trends and plan for a thermal drying facility as tip fees approached $150/wet ton. While it is anticipated that tip fees will rise that high within the 20 year planning period, it is unlikely to occur within the next 10 years, thus allowing this utility to prioritize other necessary projects. Conclusions The economic justification for installation and operation of a dryer is based on its resulting cost differential in residuals management. Emerging trends such as potential PFAS regulations and shrinking disposal outlets bring uncertainty to planning projections, but economic assessment tools that incorporate market fluctuations can be used to characterize a targeted set of future scenarios to provide a transparent and defensible basis for dryer feasibility. In comparing thermal drying against multiple scenarios for landfill tipping fee escalation, the utility in the first case study developed a clear understanding of the dryer's economic viability and the relative value of additional investments (e.g. pelletizer or pyrolysis). Market assessment can also bring greater certainty to economic evaluations by identifying target markets for dried product distribution and future trends within those markets. The second case study highlighted that understanding the market's anticipated rate of change can help pinpoint when installation of a dryer will be most effective in achieving cost control compared to alternative management options to assist with capital planning. Given that biosolids management costs are expected to continue to pose a threat to multiple US geographies, these case studies provide a valuable framework for the utilities assessing thermal drying to deploy the most viable solution given their local conditions.

The following conference paper was presented at Residuals and Biosolids 2021: A Virtual Event, May 11-13, 2021.

SpeakerSierra, Natalie

Presentation time

15:45:00

16:00:00

Session time

15:00:00

16:15:00

SessionInnovative Biosolids Process Enhancements

Session number2

Session locationSimu-Live

Topicbusiness case evaluation