Armenta, Maxwell

Max is an associate at Brown and Caldwell. Nutrient removal, process optimization, and process modeling are a few of his key specialties. Max joined...

Titles from this speaker

Description: An Evaluation Study of Santa Rosa's Existing Co-digestion Program: Why Truck Along...

An Evaluation Study of Santa Rosa's Existing Co-digestion Program: Why Truck Along when You can Optimize?

Abstract

INTRODUCTION Trucked waste programs allow WRRFs to turn organic 'waste' into a valuable resource and reduce greenhouse gas emissions through energy production. Implementing a trucked waste program maximizes the economic and societal value of feedstocks once considered environmental risks but requires oversight and maintenance to be successful. As WRRFs consider codigestion trucked waste programs, it is important for utilities to evaluate costs versus benefits, and to understand the associated operational, maintenance, administration, and monitoring requirements. The City of Santa Rosa installed a high strength waste (HSW) receiving station in 2017. The program accepts HSW such as fats, oils, and grease (FOG), brewery waste, and dairy waste while collecting revenue from tipping fees, generating energy, and recovering heat for plant processes. In addition to HSW, the City receives low strength wastes (LSW) including leachate, septic and chemical toilet waste, groundwater, gray water, and wine rinseate. While the trucked waste program operates at a net positive revenue, the City sought to further refine the program by taking a closer look at the impact from individual trucked wastes to their treatment processes to identify optimization opportunities. Brown and Caldwell (BC) and the City collaborated on a detailed study to complete the following: 1. Summarize baseline conditions 2. Identify optimization enhancements 3. Recommend enhancements while rebalancing tipping fees to maintain net positive program revenue BASLINE CONDITIONS Historical data was reviewed to identify the impacts of LSW and HSW on biogas and biosolid production. A solids-water-energy balance was completed to identify volatile solids reduction (VSR) and specific biogas production values for the WRRF. Results from the solids-water-energy balance are presented in Figure 1. Results demonstrated a 10 percent HSW flow and loading contribution in digester feed, which resulted in a 2.6 percent biosolids contribution and 15 percent biogas contribution. The relatively high VSR associated with HSW and validated through the solids-water-energy balance impacted relatively the high biogas contribution and low biosolids contribution. The LSW loadings were identified to contribute only about 1 percent of biogas, energy, and biosolids production; however, LSW sources were not sampled regularly, and assumptions were made based on values from textbooks and other local facilities for the solids-water-energy balance. Differences in total solids (TS), volatile solids (VS), and biochemical oxygen demand (BOD) concentrations impact the estimated LSW influence on plant performance. Interviews with operations identified ultraviolet transmissivity (UVT) impacts from leachate waste, which had been observed during wet weather events. Leachate impacts to UVT have been reported at flows above 1 percent by volume (gallon of leachate per gallon of wastewater), but the threshold for UVT impacts may vary depending on wastewater characteristics. The City accepts both pipeline and trucked leachate wastes. Figure 2 was created to provide a method for determining the limit of leachate that could be accepted depending on the leachate flow contribution (e.g., contributions of 1 to 4 percent by volume were plotted). Review of baseline operating conditions identified that program administration and trucked waste monitoring could be improved. Improvements to these areas required an increase in plant staffing, and the baseline assessment documented that trucked waste program administration responsibilities were shared among three environmental compliance roles. Consolidation of these responsibilities into a single program manager was recommended. Review of historical cost and revenue showed a net positive operating revenue from the trucked waste program. Tipping and permit fees were the main source of income. Energy generation, though significant (HSW was estimated to increase energy production by at least 15 percent), accounted for only 12 percent of total revenue for the City's program. This finding demonstrates the importance of setting appropriate tipping fees, although tipping fee revenues for the City include LSW as well. The three highest operating costs were evaluated as treatment costs from HSW loading, administration and compliance staffing costs, and biosolids hauling costs. OPTIMIZATION AND ENHANCEMENT OPPORTUNITIES The enhancement opportunities were divided into three categories: administration, process, and physical. A universe of potential enhancement projects was recommended based on the baseline condition assessment. The City screened enhancements and the remaining were advanced to an economic life-cycle analysis, as shown in Figure 3. LIFE-CYCLE ANALYSIS AND TIPPING FEE RECOMMENDATIONS A life-cycle analysis was completed in tandem with tipping fee rebalancing. Tipping fees were rebalanced to match the City's current net positive revenue, on average, for a 10-year lifecycle. This methodology allowed the City to determine which optimizations and enhancements to prioritize. Figure 4 demonstrates the baseline tipping fees versus recommended increases over the next 10 years. Increasing rates were necessary to keep up with escalating plant operating costs, and addition of enhancement projects (e.g., hiring additional staff, constructing a new waste hauler check-in station, etc.) was shown to have a significant impact on certain rates. BC recommended the following approach when increasing tipping fees: 1. Increase tipping fee rates for no greater than 25 percent of waste categories per year; Do not change tipping fees for most of the waste types to minimize risk of losing customers and revenue. 2. Increase rates by no more than 20 to 25 percent relative to the previous year. SUMMARY Diversion of organics from landfills provides a pathway for WRRFs to receive food waste and generate additional biogas for beneficial use. As these opportunities are considered, utilities should be aware of the requirements associated with implementing and operating a codigestion program. The lessons learned and recommendations from this study may help other utilities as they consider ways to improve plant performance and minimize risks and costs associated with the implementation, operation, and management of a trucked waste program. The lifecycle cost analysis highlights the importance of tipping fees to operate a program at net positive revenue.

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

SpeakerArmenta, Maxwell

Presentation time

14:30:00

15:00:00

Session time

13:30:00

16:45:00

SessionSession 14: Co-Digestion

Session number14

Session locationCharlotte Convention Center, Charlotte, North Carolina, USA

TopicCase Studies/Lessons Learned

Author(s)

M. Armenta

Author(s)M. Armenta1, A. Nojima2, R. Gundy3, 4,

Author affiliation(s)Brown and Caldwell1; City of Santa Rosa Water Administration2

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2023

DOI10.2175/193864718825158849

Volume / Issue

Content sourceResiduals and Biosolids

Word count17

Description: Fermentation Intensification with Vacuum-Assisted Technology: An Evaluation of...

Fermentation Intensification with Vacuum-Assisted Technology: An Evaluation of Full-Scale EBPR Alternatives Using a Calibrated Process Model Analysis

Abstract

IntensiCarb® is a vacuum-based intensification technology that provides process benefits in fermentation or anaerobic digestion. Applying this technology to fermentation allows for half the process volume to achieve improved yield of volatile fatty acids (VFA) for beneficial use. Generating VFA from fermentation provides a benefit to facilities that need supplemental carbon for nutrient removal targets in the liquid treatment process. VFA can be used by facilities to improve enhanced biological phosphorus removal (EBPR) performance, lowering effluent total phosphorus (TP) concentrations. An analysis was completed to evaluate the process performance and life-cycle costs of IntensiCarb® relative to chemical addition and conventional fermentation alternatives for TP removal. Experimental results on vacuum-assisted process intensification were used in the process performance analysis and GHG emissions were estimated to compare alternatives. The evaluation suggests IntensiCarb® is competitive with other alternatives to lower effluent TP with EBPR. FeCl3 chemical addition had the lowest life-cycle cost overall

IntensiCarbÂ® is a vacuum-based intensification technology that provides process benefits in fermentation or anaerobic digestion. An analysis was completed to evaluate the performance and life-cycle costs of IntensiCarbÂ® relative to chemical addition and conventional fermentation alternatives for the purposes of phosphorus removal. This paper describes bench-scale experimental results, presents model performance predictions, and compares life-cycle costs and greenhouse gas emission estimates.

SpeakerArmenta, Maxwell

Presentation time

16:10:00

16:30:00

Session time

15:30:00

17:00:00

SessionExtracting Carbon for Nutrient Removal

Session locationRoom S403a - Level 4

TopicFacility Operations and Maintenance, Intermediate Level, Municipal Wastewater Treatment Design, Nutrients

Author(s)

Armenta, Maxwell

Author(s)M. Armenta 1; F. Kakar 2 ; A. Al-Omari 3; C. Muller 4; K. Bell 5; G. Nakhla 6; D. Santoro 7; J. Boone 7; M. Armenta 1; R. Coleman 8;

Author affiliation(s)Brown and Caldwell 1; Brown and Caldwell 2 ; Brown and Caldwell 3; Brown and Caldwell 4; Brown and Caldwell 5; University of Western Ontario, London, ON 6; USP Technologies 7; PRAB, Kalamazoo, MI 7; Brown and Caldwell 1; Environmental Operating Solutions, Inc. 8;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2023

DOI10.2175/193864718825159027

Volume / Issue

Content sourceWEFTEC

Word count18

IntensiCarb for Anaerobic Digestion Intensification: A Techno-economic Analysis

Abstract

Intensicarb® is a vacuum-based sludge concentration technology, that when installed to intensify anaerobic digestion at a Water Resource Recovery Facility (WRRF) could decrease hydraulic retention times (HRT) while maintaining solids retention times (SRT), providing various benefits towards process intensification. Previous work has demonstrated Intensicarb® feasibility for fermentation intensification (Okoye et al. 2022) and digestion intensification (Khadir et al. 2024) at lab scale as well as its economic feasibility for use as fermentation intensification for onsite WRRF supplemental carbon production (Armenta et al. 2023). This study presents a techno-economic analysis (TEA) of the Intensicarb® process when used to intensify mesophilic anaerobic digestion (MAD) at WRRFs of multiple sizes (10 million gallons per day (MGD), 50 MGD, and 250 MGD of influent flow). Significant reductions of overall lifecycle costs, including reductions in process volume and facility footprint were seen for all 3 facility sizes analyzed. Methodology Three facility sizes were evaluated, based on 10, 50, and 250 MGD influent flows, representing small, medium, and large facilities. This was correlated to digester solids loadings of 11,000, 54,000, and 270,000 lb/day respectively. Four scenarios of increasing intensification were developed and evaluated for each facility size. These scenarios were based on the decoupling of HRT and SRT provided by the IntensiCarb® technology. Average operating SRT was assumed to be 30 days for all scenarios, and the HRT was changed from 30 days (conventional MAD), to 15, 7.5, and 5 days with IntensiCarb®. These were designated as intensification factors (IFs) 1, 2, 4, and 6. Simplified process diagrams showing the conventional MAD process and MAD with IntensiCarb® are shown in Figures 1 and 2, respectively. Flows and loads used in each scenario were developed in Excel (Microsoft), with the assumption that volatile solids destruction was constant over the range of intensification studied (Khadir et al. 2024). Further assumptions are shown in Tables 1 and 2. These parameters were then used to develop the TEA, using a Net Present Cost approach and assuming a 30-year project lifespan. A nominal discount rate of 6% and an escalation rate of 3% were assumed (Construction Cost Index 2019-2022 2022; Guidelines and Discount Rates for Benefit-Cost Analysis of Federal Programs 2023). Costs associated with this TEA were developed based on vendor budgetary estimates for vacuum evaporators from PRAB and IWE, and AD tank mixers from Anaergia. Other equipment estimates, including conventional concrete AD tanks and associated pumps were developed based on previous Brown and Caldwell designs. Operational costs outside of labor, including electrical energy costs for pumping and mixing, sludge heating energy costs, and rehabilitation and replacement costs were developed based on the process modeling outputs and the budgetary estimates outlined above. A sensitivity analysis based on several key unit costs was developed to better estimate lifecycle costs for sites in North America with different operating costs. To simplify the analysis and provide a more conservative estimate of IntensiCarb®'s potential cost savings, two key potential benefits of the IntensiCarb® process were not included in this analysis. These were biogas recovery enhancement, and reduction of nitrogen levels in the sludge (Muller et al. 2024). Additionally, vendor estimates were used to develop physical layouts for all scenarios, which were compared on a volume and footprint basis to determine any physical space savings provided by the Intensicarb® technology. Results and Discussion The results of the TEA indicated significant reductions in process volume and footprint, particularly in larger facilities, leading to potential cost savings. These results are shown in Figure 3. The economic analysis showed that higher intensification factors generally result in lower life cycle costs, with the most substantial savings observed at intensification factors of 4 and 6. However, the benefits diminish at higher intensification levels for midsize plants due to the discrete sizes of evaporator equipment available. Life cycle costs for the 50 MGD facility are shown in Figure 4. The study concludes that IntensiCarb® technology is viable at small, medium, and large scales, with the largest savings seen at IF 6 for all sizes (27%, 26%, 16% NPC savings over conventional MAD seen at IF 6 for the small, medium, and large facilities respectively). Through a sensitivity analysis, key factors driving life cycle costs were identified, with natural gas, electricity prices, and IntensiCarb® facility construction costs causing the most impact on NPC. The baseline values for these costs, as well as their identified upper and lower bounds, are shown in Table 3. Future work should focus on empirical testing and theoretical analysis to refine cost assumptions and explore additional benefits like biogas quality improvement and nutrient recovery.

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

SpeakerSeidel, Alexander

Presentation time

09:10:00

09:30:00

Session time

08:30:00

11:45:00

SessionInnovations in Sludge Management: Enhancing Anaerobic Digestion and Phosphorus Control

Session number10

Session locationBaltimore Convention Center, Baltimore, Maryland, USA

TopicAerobic Digestion, Anaerobic Digestion, Biogas Utilization, Biosolids, Biosolids treatment, Class A, Dewaterability, Phosphorus recovery, struvite, electrochemical, Pilot Scale, Process Intensification, Resource Recovery, Solids Pre-Treatment, Sustainability, thermophilic, THP, CAMBI

Author(s)

Seidel, Alexander, Armenta, Maxwell, Kakar, Farokh, Al-Omari, Ahmed, Khadir, Ali, Sheculski, Chris, Santoro, Domenico, Nakhla, George, Bell, Katie, Muller, Chris

Author(s)A. Seidel1, M. Armenta1, F. Kakar1, A. Al-Omari1, A. Khadir2, C. Sheculski3, D. Santoro2, 4, G. Nakhla3, K. Bell 1, C. Muller1

Author affiliation(s)Brown and Caldwell, 1 University of Western Ontario, Canada, 2Trojan Technologies, 3USP Technologies, 4

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2025

DOI10.2175/193864718825159759

Volume / Issue

Content sourceResiduals and Biosolids Conference

Word count9

Unique Approach to Inline Fermentation Stabilizes Biological Phosphorus Removal

Abstract

Many facilities do not have consistent or sufficient volatile fatty acids (VFA) available in the influent wastewater to facilitate efficient and effective biological phosphorus removal. The lack of influent VFA content has driven facilities to modify plant operations, taking advantage of influent carbon to generate their own VFA to ensure consistent biological phosphorus removal to maintain low effluent phosphorus concentrations. An intermittent mixing strategy with gentle pulses of compressed gas allows for VFA generation and transport to facilitate more stable effluent phosphorus. This paper reviews two water resource recovery facilities that recently upgraded their traditional anaerobic selectors to include inline fermentation with an intermittent mixing strategy to produce VFA for improved biological phosphorus removal. One plant increased phosphorus removal efficiency from 85% to 95%, while the other plant saw consistently lower effluent total phosphorus below 0.2 mg/L.

This paper was presented at WEFTEC 2023.

SpeakerArmenta, Maxwell

Presentation time

15:50:00

16:10:00

Session time

15:30:00

17:00:00

SessionExtracting Carbon for Nutrient Removal

Session locationRoom S403a - Level 4

TopicFacility Operations and Maintenance, Intermediate Level, Municipal Wastewater Treatment Design, Nutrients

Author(s)