Cecconi, Francesca

Francesca is a process engineer of Black & Veatch with 7 years of experience in wastewater treatment research and consulting. She achieved her...

Joined:

About Cecconi, Francesca

Francesca is a process engineer of Black & Veatch with 7 years of experience in wastewater treatment research and consulting. She achieved her bachelor and master's degree in environmental engineering from the University of Florence, Italy. She has achieved her PhD in Civil and Environmental Engineering from the University of California, Irvine in 2020. She specializes in carbon management, and sustainable design of nutrient removal/recovery systems.

Cecconi, Francesca

Titles from this speaker

Modelling of Primary Sludge and RAS Fermentation for Carbon Management Optimization at WRRFs

Abstract

Introduction Conventional wastewater treatment plants are transitioning to integrated resource recovery and upcycling, which requires effective management of biodegradable organic carbon. This involves developing approaches to carbon diversion, such as anaerobic digestion of primary sludge and waste activated sludge for energy and fertilizer (Gavala et al 2003). Alongside the push to enhance resource recovery, many WRRFs are also under pressure to meet strict effluent nutrient (N and P) discharge targets. While new nitrogen management strategies that do not rely on carbon are emerging, the majority of nutrient removal systems still follow a conventional, optimized nitrification-denitrification pathway that relies on biodegradable organic carbon to support denitrification. Moreover, biodegradable organic carbon is crucial for biological phosphorus removal. Years of experience have demonstrated that successful biological nutrient removal depends not only on sufficient organic substrate, but also on the right type of bioavailable carbon supplied at the appropriate location and time for optimal utilization (Wu et al, 2009; Huang et al, 2018). Our research aims to determine the best way to utilize the variety of organic-carbon rich feedstocks available in a WRRF and how fermentation can be used as a platform process to manage the logistics of biodegradable organic carbon supply and demand. To address these questions, we conducted a pilot-scale assessment of the fermentation of a blend of wastewater-derived primary sludge (PS) and waste activated sludge (RAS) from two treatment plants. Plant 1, which only performs BOD removal, has a short solid retention time (SRT) of 2 days, while Plant 2 performs biological nutrient removal (both TN and TP) and has a longer SRT of 10 days. We conducted batch fermentation experiments on different blends of RAS and PS over a two-week period to analyze biomass kinetics and the products formed during fermentation. We used the SUMO simulator software to model each batch experiment, calibrate the two-week experimental data, and analyze the hydrolysis rates and influent fractionation variations based on the feedstock characteristics. Material and Methods Experimental Set-up Pilot-scale fermentation experiments were performed using a purpose built two-tank pilot system (Figure 1). Each bioreactor have a capacity of 75 L (20 gal). The temperature was controlled at 20 degrees C in each bioreactor. Each fermentation experiment was run in duplicate for 14 days. Three blend scenarios of RAS and PS were targeted, for both Plant 1 and Plant 2 feedstocks: 1)RAS only 2)50% RAS and 50% PS in VSS mass 3)100% PS Modelling Data from each batch experiment were modelled using Sumo Dynamita to validate the observed results as well as elucidate the biological processes. Full plant models were configured for Plant 1 and Plant 2 (see Figure 2) and an SBR process unit was used to represent the pilot reactor. Default influent parameters and fractionation for the full plant models were initially used and were tuned in order to match the TCOD, TSS, VSS, sCOD, NHx and OP data. After the initial conditions were matched, the kinetics and biology were calibrated until the experimental curves were fitted. The reduction factor of anaerobic hydrolysis was also tuned from the 0.5 default to the 0.05-0.15 range, as observed in the Water Research Foundation 4975 report. Results and Discussion Figure 3 shows the timeseries of the soluble COD yield, expressed as mass of sCOD produced per unit mass of VSS (mgCOD/gVSS) throughout the experiment for the different RAS and PS blends, for both short SRT combinations (left) and long SRT combinations (right). For each test, the experimental data was simulated on SUMO and the results of the calibrated models are shown in the dashed line. It can be noticed that the sCOD yield is different between the different PS and RAS blend combinations and also between the long and short SRT RAS. Overall, the highest fermentation rate is achieved around 3 days from the start of the experiment for all the tests. Higher sCOD yields are shown in the first week, while the sCOD production largely slows down in the second week of the test. Figure 4, left) shows the 3-day fermentation rate comparison for the different RAS and PS blends, for both short SRT and long SRT RAS biomass. The reduction factor of the anaerobic hydrolysis kinetic parameter was calibrated for each test and varied between the different feedstock blends (Figure 4, right), showing higher hydrolysis rates with higher fermentation rates and higher PS content, as reported by Ozyildiz et al 2023. The average 3 day fermentation rates ranged from 0.25+/-0.1 mg sCOD/gVSS/h for long RAS only to 3.1+/-0.2 mg sCOD/gVSS/h for 50% PS and 50% RAS, long SRT. Overall, the 50/50 ratio was noticed to be the optimum ratio to maximize soluble COD production, with both RAS types, however a higher fermentation rate (around 50% higher) was achieved when longer SRT RAS was combined with PS compared to the short SRT/PS blends. The fermentation performance is driven by the ratio between the concentration of hydrolysing microorganisms, mainly deriving from RAS, and the fermentable substrate, which is more available in primary sludge. Our research outcomes will be of value to utilities aiming to integrate the stringent effluent nutrient (N and P) discharge targets with energy and resource

The main objective of this pilot fermentation testing was to evaluate the most effective utilization of the range of organic-carbon rich feedstocks within a water resource recovery facility (WRRF). Experimental results suggest that a 50-50 blend of primary sludge (PS) and return activate sludge (RAS) fermentation leads to highest sCOD yield. The experiments were modelled using SUMO by calibrating the hydrolysis rate, plant influent fractionation, and the hydrogen production yield.

SpeakerCecconi, Francesca

Presentation time

16:30:00

17:00:00

Session time

15:30:00

17:00:00

SessionEBPR Pulse: Current Trends, Full-Scale Optimization, Model for Sustainability

Session number227

Session locationRoom 243

TopicAdvanced Level, Municipal Wastewater Treatment Design, Nutrients

Author(s)

Cecconi, Francesca, Pifer, Leah, Bhattarai, Bishav, Downing, Leon

Author(s)F. Cecconi1, L. Pifer1, B. Bhattarai1, L.S. Downing2

Author affiliation(s)1Black & Veatch, CA, 1, 2Black and Veatch, WI

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2024

DOI10.2175/193864718825159568

Volume / Issue

Content sourceWEFTEC

Word count14

Soft-Sensor Application to Improve Ammonium Sensor Robustness in WRRFs

Abstract

Wastewater is a harsh environment for any instrumentation, however sensors implementation is fundamental in Water Resource Recovery Facilities. The study focuses on DO, pH, ORP, MLSS and ammonium sensors, with a specific attention on the last because of its promising application for ammonium-based aeration control. A software sensor is developed based on a Neural Network model with Principal Components Analysis as preprocessing of the raw data collected at a full-scale facility for a seasonal cycle. The soft-sensor predicts ammonium based on the other water quality data, to improve the hardware sensor robustness and enhance fault detection.

SpeakerCecconi, Francesca

Presentation time

15:10:00

15:30:00

Session time

13:30:00

15:30:00

SessionNext Generation Data Analytics

Session number201

TopicFacility Operations and Maintenance, Intelligent Water, Municipal Wastewater Treatment Design, Research and Innovation

Author(s)

F. Cecconi,Y. ItoD. Rosso,

Author(s)F. Cecconi1; ,2; Y. Ito3; D. Rosso1; ,2;

Author affiliation(s)Department of Civil and Environmental Engineering, University of California, Irvine, CA1; Water-Energy Nexus Center, University of California2; Horiba Advanced Techno Co, Ltd.3

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2020

DOI10.2175/193864718825157814

Volume / Issue

Content sourceWEFTEC

Word count10

The Key To Predict Anaerobic Processes Performance: Bioelectrochemical Sensors

Abstract

Introduction and Background
The use of bioelectrochemical sensors (BESs) to monitor biological processes in engineered environmental systems has received increasing interest in recent years. The BES is an electrochemical devise, based on the electrochemical interactions of microorganisms and enzymes with the electrodes. The signal produced using this sensor is a direct result of the microbial activity within the BES. In detail, it relies on the ability of some bacteria to transfer electrons from a reduced electron donor, the substrate, to a solid electrode material called anode, which is the electron acceptor. The anode is connected, via an external electrical circuit, to the cathode, which is covered by bacteria that catalyze the reduction of an oxidized electron acceptor (Lovley, 2011). The potential benefits of using these sensors include provide early warnings of biological process upsets, detect inhibitory effects of shock loads and toxic content and monitor nutrient depletion (Grattieri et al, 2017). Anaerobic processes, especially anaerobic digestion and co-digestion systems, could benefit from the implementation of these sensors to monitor the process performance, given their high operational complexity in managing the variation in feedstock composition, complex metabolic properties and feeding strategies. However, open questions remain on the efficacy and reproducibility of BESs. Our research aims to fill knowledge gaps related to feasibility of using BESs to monitor and predict the performance of anaerobic digesters. The specific objective of this study is to investigate the potential of a BES to identify the impact of a range of simple and complex organic substrates on digester performance and biokinetics.
Material and Methods
Experimental Set-up Lab-scale batch tests were performed using digestate from an operating anaerobic digester at a water resource recovery facility in California. Each test was performed at 35Â°C. The digestate was collected from the full-scale digester and mixed (mixer speed ~ 300 RPM) in a 15 L batch reactor (Figure 1). After a 2-hour acclimation period, an organic feedstock (0.6 L) was added to the batch reactor. The feedstocks evaluated in this research include acetate, isovalerate and primary sludge (PS).
Probes and Data collection The BES product SENTRY, manufactured by Island Water Systems (Charlottetown, PE, Canada) was employed in this research. The SENTRY BES reports a microbial electron transfer (MET) as a surrogate for biomass activity. One SENTRY probe, a pH sensor (DPD1, Hach Company, Loveland, CO) and an ORP sensor (DRD1, Hach Company, Loveland, CO) were installed in the batch reactor. In between each batch test, all the sensors were kept in the same mixed digestate and before each batch test the sensors were cleaned with a wet cloth. The SENTRY sensor did not require any calibration or chemical cleaning. Grab samples were collected throughout the experiments to measure Volatile Fatty Acids (VFA), soluble COD, NHx-N and Ortho P.
Preliminary Results and Discussion
Figure 2 and 3 show the results of the batch tests, where at time -2h the mixed liquor aliquot is added to the reactor and at time 0 the feedstock is added to the set up. The response of the BES system to different concentrations of acetate is markedly different (Figure 2). The use of an acetate feedstock of 2,000 mg/L and 22,500 mg/L resulted in an in-situ VFA concentration of 190 mg/L (Fig.2, top panel) and 950 mg/L at the start of the experiment (t=0), respectively. In both cases, the BES sensor responds rapidly to the feedstock addition, reaching a maximum level of metabolic activity (maximum MET value) within 1 hour. The complete depletion of acetate can be identified because the sensor response returns to steady state condition and the VFA concentration in the reactor returns to the baseline (i.e., pre-feedstock addition) level. Figure 3 shows the response of the sensor to three different sources of feedstock: Sodium Acetate (top), Isovaleric Acid (middle) and Primary Sludge (bottom). For the two complex feedstocks (isovaleric acid and primary sludge), the BES sensor response to the feedstock addition was slower and the metabolic activity (MET) continued to slowly increase while the substrate was converted to acetate (increase in VFA). Once the complex substrate was converted to acetate, the readily biodegradable matter was then depleted (decrease in VFA concentration) and the sensor response decreased until returning to the baseline level. Figure 4 shows, for all the experiments, the MET increase rate in the first 1 hour from the feedstock addition and the VFA decrease/increase rate in the first 2 hours. Initial VFA uptake rates increased proportionally with higher initial VFA concentrations. However, at high initial concentrations â€“ the initial VFA degradation rates appear to have reached a maximum (Figure 4, top left), suggesting a Monod kinetics model. The change in the initial MET signal shows a similar trend (Figure 4, top right): at higher substrate concentrations corresponds a higher MET increased rate until it reaches a maximum response. Overall the BES response shows a strong correlation to the initial VFA uptake rates (Figure 4, bottom panel), although this correlation does not reflect the impact of the initial VFA concentration on the change in the BES signal. Preliminary results from this research suggest that the signal from a BES is influenced by the initial substrate concentration and substrate biodegradability. Our current experiments are focused on evaluating the reproducibility of these results using additional feedstocks and evaluating the reproducibility of BES results using digestate biomass from other WRRFs. These results will be included as part of the full paper submission and presentation. Collectively, our study suggests that a BES can be used to monitor anaerobic digesters and detect upset events, since the sensor's bacteria are a good reflection of the digester's biomass composition and behaviour. Furthermore, the BES signal can be employed as part of a process control strategy to optimize digester feeding and mitigate overloading the digesters.

Bioelectrochemical based sensors (BES) have recently emerged as tools to monitor biological processes. This study investigates the potential of a BES to identify the impact of different organic substrates on digester performance. The sensor shows to respond to the substrate uptake rate and may provide a surrogate for the substrate hydrolysis rate. BES sensors show a potential application in in predictive capacity and could help utilities integrating the treatment of high strength organics.

SpeakerCecconi, Francesca

Presentation time

09:25:00

09:40:00

Session time

08:30:00

10:00:00

TopicIntermediate Level, Biosolids and Residuals, Facility Operations and Maintenance, Intelligent Water, Research and Innovation

Author(s)

Cecconi, Francesca

Author(s)F. Cecconi1; Y. Tse2; V. Rajasekharan3; S. Sathyamoorthy4

Author affiliation(s)Black & Veatch, Walnut Creek, CA1; Black & Veatch, Walnut Creek, CA2; Hach, Loveland, CO3; Black & Veatch, Walnut Creek, CA4