Muller, Christopher

Dr. Christopher Muller is the National Technology and Innovation Lead- Solids and Energy, for Brown and Caldwell. Chris received in B.S. in Marine and Freshwater Biology from the University of New Hampshire in 1996. He later attended Virginia Tech where he obtained his M.S. in Environmental Engineering and a PhD in Civil Engineering. Chris has primarily worked as a process engineer in the areas of solids process, design, optimization and enhancement with a focus on co-digestion and resource recovery.

Titles from this speaker

A Surveillance Study: Per-and polyfluoroalkyl Substances (PFAS) in Biosolids

Abstract

This surveillance study was aimed at understanding concentrations of PFAS in biosolids. To address this objective, samples were collected from of twenty-five wastewater resource recovery facilities (WRRFs) throughout North America over a six-month period. A minimum of two samples were collected from each WRRF: Location A – sludge entering the stabilization process, and Location B – biosolids (post-stabilization sludge). Modified EPA Method 537.1 was used to analyze 40 PFAS compounds in these samples by Eurofins Laboratories. Only 20% of the measured PFAS compounds were detected in the biosolids samples. Three major solid stabilization methods were evaluated, anaerobic digestion, incineration, and chemical stabilization. Anaerobic digestion and chemical stabilization indicated increases in PFAS in Location B in comparison to Location A, except for in the case of incineration, where ash samples (Location B) did not contain any of the measured PFAS compounds above the method detection limit.

Per-and polyfluoroalkyl Substances (PFAS) are being extensively studied in all the matrices due to their ubiquitous presence in the environment and negative human health impacts. This study conducted a survey of twenty-five wastewater resource recovery facilities (WRRF) throughout North America over a six-month period to evaluate for PFAS other emerging contaminants in biosolids. Among the 40 PFAS compounds evaluated, only 20% were detected in biosolid samples. Concentrations of the detected PFA

SpeakerOza, Shubhashini

Presentation time

13:30:00

13:55:00

Session time

13:30:00

15:00:00

SessionUnderstanding and Addressing PFAS in Biosolids

Session locationRoom N426b - Level 4

TopicMunicipal Wastewater Treatment Design, PFAS

Author(s)

Oza, Shubhashini

Author(s)S. Oza 1; S. Estahbanati 2 ; J. Norton 3; N. Hontoria 4; X. Fonoll Almansa 5; M. Khan 6; C. Muller 7; K. Bell 8; J. Hatfield 4; S. Oza 1;

Author affiliation(s)Brown & Caldwell 1; Brown & Caldwell 2 ; Great Lake Water Authority 3; Brown & Caldwell 4; Great Lake Water Authority 5; Great Lake Water Authority 6; Brown & Caldwell 7; Brown & Caldwell 8; Brown & Caldwell 4; Brown & Caldwell 1;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2023

DOI10.2175/193864718825159011

Volume / Issue

Content sourceWEFTEC

Word count10

Description: Arrested Anaerobic Digestion and Recovery of Value-added Products Through...

Arrested Anaerobic Digestion and Recovery of Value-added Products Through Vacuum-intensified Alkaline Fermentation

Abstract

In this proof of concept experimental work, it was demonstrated that vacuum-driven fermentation can enable efficient resource recovery from municipal sludge and provide means to arrest anaerobic treatment to maximize extraction of added value products such as ammonia and volatile fatty acids (VFA). The concept relies on applying low vacuum to strip ammonium from fermented sludge, allowing the recovery of ammonium sulfate by chemisorption. Moreover, volatile fatty acids and soluble phosphorus, highly concentrated in the fermentate, can be separated using a pre-conditioning step based on iron flocculation and hydrogen peroxide (to precipitate phosphates) followed by mechanical filtration. This way, nutrient-free soluble carbon and volatile fatty acids can be recovered in the filtrate, while nutrient-rich solids can be further processed by anaerobic digestion or directly used as soil amendment and fertilizers. In this project, a feasibility study, centered on laboratory tests and model-based analysis, to determine the viability of this new process to accelerate the realization of circular economy in the wastewater industry. The study was designed to confirm the impact of pH on the ability to improve VFA production from fermentation and improve the selective separation of ammonia through stripping compared to conventional fermentation or vacuum assisted fermentation without pH adjustment. It also confirmed whether the value-added products recovered by vacuum technologies can maintain high yields and sufficient purity for circular applications (i.e., supplemental carbon for biological nutrient removal, fertilizers for agriculture, carbon-based precursors to bioplastics, etc.). The study demonstrated the improvement of ammonia recovery by more than double compared to vacuum at neutral pH. In addition, VFA yield was improved by 84% compared to the control. Operating in alkaline conditions ceased the methanogenesis process resulting in accumulation of VFA. On the other hand, the elevated pH reduced the undissociated acids concentrations, which may have resulted in improved hydrolysis and fermentation rates.

SpeakerAl-Omari, Ahmed

Presentation time

14:00:00

14:20:00

Session time

13:30:00

15:00:00

SessionAdvances in Anaerobic Digestion and Sidestream Treatment

Session locationRoom S404a - Level 4

TopicIntermediate Level

Author(s)

Al-Omari, Ahmed

Author(s)A. Al-Omari 1; Kirim 2 ; X. Bai 3; J. J. Walton 4; C. Muller 5; K. Bell 6; D. Santoro 7; G. Nakhla 8; A. Al-Omari 1;

Author affiliation(s)Brown and Caldwell 1; 5; 6; 7; 8;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2023

DOI10.2175/193864718825158984

Volume / Issue

Content sourceWEFTEC

Word count13

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

Description: Innovation Portfolio Management for Retrofitting Advanced Biotechnologies for...

Innovation Portfolio Management for Retrofitting Advanced Biotechnologies for Anaerobic Digestion Process at Lulu Island Wastewater Treatment Plant

Abstract

Metro Vancouver recently commissioned the Pilot Digestion Optimization Facility (PDOF) at its Lulu Island Wastewater Treatment Plant (LI WWTP) to facilitate the evaluation of different digestion optimization technologies without risk to full-scale plant operation. This study summarizes the integrated approach adopted at the pilot-scale preliminary design stage for two of these technologies. The first technology aims to increase biogas production rates by testing the Direct Interspecies Electron Transfer (DIET) process using electroconductive materials. The second technology utilizes a biological hydrogen methanation (BHM) process to convert the carbon dioxide portion of biogas into renewable natural gas (RNG) using hydrogen. Cost-effective pilot-scale conceptual designs are developed for testing the in-situ and ex-situ configurations of these technologies in order to reach a go/no-go decision quickly, while still producing replicable results for further scale-up. To guide the decision-making process for selecting these technologies for pilot testing, GHG emission reduction calculations and an energy balance model are used to evaluate the environmental impacts of implementing these technologies at full-scale. A Sumo model is used to evaluate the effects of implementing these technologies on process intensification.

Metro Vancouver, in collaboration with its partners, is developing innovative technologies that reduce greenhouse gas emissions and intensify existing digestion processes. Metro Vancouver will first assess the effectiveness and scalability of these technologies at the Lulu Island Pilot Digestion Optimization Facility. Metro Vancouver intends to incorporate these technologies into one of its treatment facilities if the technologies prove successful at pilot-scale.

SpeakerChegounian, Parisa

Presentation time

15:30:00

15:50:00

Session time

15:30:00

17:00:00

SessionImproving Biosolids Treatment Efficiency

Session locationRoom S403b - Level 4

TopicEnergy Production, Conservation, and Management, Intermediate Level, Research and Innovation

Author(s)

Kakar, Farokh Laqa

Author(s)F. Kakar 1; C. Muller 2 ; T. Barber 3; F. Kakar 1; P. Chegounian 4; L. Zaremba 4; T. Gregonia 4; P. Kadota 4; S. Sorensen 4; A. Al-Omari 5;

Author affiliation(s)Brown and Caldwell 1; Brown and Caldwell 2 ; Brown and Caldwell 3; Brown and Caldwell 1; Liquid Waste Services Department, Metro Vancouver, Burnaby, BC, Canada 4; Liquid Waste Services Department, Metro Vancouver, Burnaby, BC, Canada 4; Liquid Waste Services Department, Metro Vancouver, Burnaby, BC, Canada 4; Liquid Waste Services Department, Metro Vancouver, Burnaby, BC, Canada 4; Liquid Waste Services Department 4; Brown and Caldwell 5;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2023

DOI10.2175/193864718825159034

Volume / Issue

Content sourceWEFTEC

Word count18

Description: IntensiCarbTM- A Novel Vacuum Evaporative Process for the Intensification of...

IntensiCarbTM- A Novel Vacuum Evaporative Process for the Intensification of Anaerobic Digestion

Abstract

Mesophilic anaerobic digestion is the most deployed biological sludge stabilization process at wastewater treatment plants in North America. It also plays a central role in energy and resource recovery from wastewater treatment plants. This paper explores the application of medium vacuum pressure (~100 mbar) operated in a side stream recirculating reactor as a mechanism for process intensification and resource recovery, utilizing the IntensiCarbTM process. Currently within the industry the primary means of process intensification are either through the elevation of operating temperature (ex. thermophilic digestion), pre-conditioning of sludges (ex. thermal hydrolysis) or separation of solids and hydraulic retention time (ex. recuperative thickening). The IntensiCarbTM process utilizes the decoupling of SRT and HRT to increase process capacity while simultaneously reducing the influence of toxic metabolic by products through extraction (ex. ammonia-N). This paper discusses the results of side-by-side comparison of conventional mesophilic digestion with varying intensification factors (2x, 3x, 4x) for bench-scale trials conducted at Western University in London, Ontario, based on the process flow provided in Figure 1. The intent of this experimental design was to focus on understanding the fundamental process changes that occur when vacuum evaporation is applied to a conventional mesophilic digester. In particular, the question being investigated is whether the evaporation process and the extraction of materials result in any fundamental changes in the operation of the digestion process or does it simply operate in a manner similar to recuperative thickening. Table 1 provides a summary of the operating conditions tested, with Intensification Factor 1 (IF1) representing the control and IF2, 3 and 4 representing varying degrees of decoupling of both SRT and HRT. All the digesters were fed a mix of primary and secondary sludge (Ave. TS = 2.9%, VS =2.18%) periodically collected from the Greenway Wastewater Treatment Plant in London, Ontario. The digesters were all operated at mesophilic temperatures (~35-37 °C). Across the range of intensification factors tested, in general, all processes demonstrated effective anaerobic digestion of the sludge, noting that the highest intensification factor (IF-4) there were episodic instability events (data not shown). This suggests that either the process is approaching its maximum extent of intensification, or the specific combination of HRT and SRT is not sustainable. A number of factors could be causing this observed instability including insufficient active fraction of biomass at the extended SRT, the biomass population is at an inflection point with shifting populations or an undefined stressor is impacting the population. Additional research will be required to explore the ultimate limits of intensification. What is apparent from the data in Table 1 is that in general IntensiCarbTM does not appear to significantly change the extent of digestion with the VSr ranging from 46-55 percent relative to the control at 50 percent. However, the rate of digestion is significantly enhanced by the increase in solids concentration, resulting in overall higher solids throughput rate and rate of methane generation increasing from 0.29 m3-CH4/m3-digester-day to a maximum of 1.08 m3-CH4/m3-digester-day (Figure 2). A challenge with most process intensification strategies deployed to date is the impact of metabolic byproducts on the process. Of particular interest is ammonia, as it is produced through the decomposition of proteins, which constitute a significant fraction of sludge materials. To date no technology has effectively managed ammonia-N in-situ, resulting in risks for process instability and or significant population shifts, as reported by Mah et al. (2017) for THP. The concentration of ammonia in digesters tested were very similar (Table 1). This is significant in that the control of ammonia in the digester could support high loadings without the negative impacts. Figure 3 simulates what solids concentrations sludge would need to be loaded at to a conventional digester to achieve the same degree of intensification and the resulting total ammonium concentration in the digester would be. What is apparent from the graph is that conditions similar to those observed in thermal hydrolysis would need to be achieved, but the resulting total ammonia concentrations would approach the current limits of those systems. Furthermore, the feed solids would need treatment to reduce the viscosity to make the material pumpable. Figure 4, presents the nitrogen balanced conducted across each system, showing significant removal of ammonium-N to the condensate of the evaporator from the digestate. Supporting the observation that the IntensiCarbTM process creates a unique condition where the negative impacts of ammonia can be directly controlled in a highly loaded digestion process. Furthermore, the condensate is a very clean liquid, devoid of solids making it an ideal solution for ammonia recovery and beneficial use; potentially eliminating the need for centrate treatment for nitrogen. The combination of reduced nitrogen load and stable operations suggest the peak capacity of the IntensiCarbTM process was not achieved, in these tests. Plotting the empirically derived peak loading conditions for common stabilization processes and the resulting average total solids load, at a volatile fraction of sludge equivalent to the one used in this study, it is possible to investigate potential peak loadings; assuming similar process limitations of peer processes. The IntensicarbTM process, as currently tested, would appear to have a similar capacity to thermophilic digestion (Figure 5) for loading. However, at the highest average loading condition, IF-3, no process instability was observed, suggesting further intensification could be possible and should be investigated. Overall, the IntensiCarbTM, based digestion process is early in development but is demonstrating promise and the novel application of vacuum is generating conditions within digesters that have not been evaluated to date. The combination of process intensification through decoupling SRT and HRT and the depression of ammonia-N concentrations would suggest the system may achieve further enhancement as optimal operating conditions are defined. Concurrent with the completion of these bench trials a pilot facility is being planned by the Great Lakes Water Authority to further vet this process. This pilot will investigate the scalability of the technology, introduce of real-world operating dynamics, further optimize operating conditions to define a design loading criterion and develop a techno-economic analysis. Vacuum enhanced anaerobic digestion represents a novel process for the intensification of anaerobic sludge stabilization. Potentially offering unique opportunities for resource recover, ammonia-N and dissolved methane, as well as providing a mechanism to alleviate the current limitations associated with anaerobic digestion, metabolic byproduct toxicity. If successful, this technology could provide the next step forward in resource recovery from sludges.

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

SpeakerMuller, Christopher

Presentation time

11:15:00

11:45:00

Session time

8:30:00

11:45:00

SessionSession 12: Innovative Processes in Anaerobic Digestion

Session number12

Session locationCharlotte Convention Center, Charlotte, North Carolina, USA

TopicResearch & Innovations

Author(s)

C. Muller

Author(s)C. Muller1, A. Khadir2, A. Al-Omari3, D. Santoro4, E. Jang5, K. Bell6, F. Okoye7, J. Norton8, X. Fonoll Almansa9, G. Nakhla10,

Author affiliation(s)Brown and Caldwell1; USP Technologies2; Wester University of Ontario3; Great Lakes Water Authority4

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2023

DOI10.2175/193864718825158823

Volume / Issue

Content sourceResiduals and Biosolids

Word count13

Description: Intensifying Anaerobic Digestion with a Side-Stream Vacuum-Based Biosolids Treatment...

Intensifying Anaerobic Digestion with a Side-Stream Vacuum-Based Biosolids Treatment Technology: Process Validation Exceeding Expectations

Abstract

This study evaluates the application of a novel ex-situ vacuum-enhanced anaerobic digestion technology, referred to as IntensiCarbTM (IC), for process intensification through decoupling SRT from HRT, and ammonia recovery. Findings revealed that the IC sustain almost the same methane yield and COD destruction efficiency as the control at three times the organic loading rate (OLR). Furthermore, the ammonia concentration in IC- digester operating at 3 times higher organic loading was pretty much the same as the control, demonstrating the effectiveness of IC-technology in elutriating a large fraction of ammonia from IC-digester into the condensate. This leads to stable digester operation as well as a potential to generate revenue. The combination of high organic loading and low ammonia concentrations resulted in the prevalence of the higher growth rate Methanosarcinaceae in the IC-digester compared to the low growth rate Methanoseata predominance in the control.

A novel ex-situ vacuum-enhanced anaerobic digestion technology was evaluated for process intensification in anaerobic digesters. This technology, referred to as IntensiCarbTM (IC), could increase the OLR and volumetric loading by 3 times while maintaining stable methane yields and COD destruction. Ammonia recovery, reduced digester size, as well as reduced nitrogen loadings in sidestreams, are the major advantage of IC-technology.

SpeakerKhadir, Ali

Presentation time

13:30:00

13:50:00

Session time

13:30:00

15:00:00

SessionAdvances in Anaerobic Digestion and Sidestream Treatment

Session locationRoom S404a - Level 4

TopicIntermediate Level

Author(s)

Khadir, Ali

Author(s)A. Khadir 1; F. Omoye 2 ; E. Jang 3; D. Santoro 4; J. Walton 4; C. Muller 5; A. Al-Omari 6; K. Bell 7; G. Nakhla 8;

Author affiliation(s)Western University, Canada 1; Western University, Canada 2 ; USP Technologies, Canada 3; USP Technologies, Canada 4; USP Technologies, Canada 4; Brown and Caldwell, USA 5; Brown and Caldwell, USA 6; Brown and Caldwell 7; Western University, Canada 8;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2023

DOI10.2175/193864718825158983

Volume / Issue

Content sourceWEFTEC

Word count15

Description: The Addition of FOG to Thermal Hydrolysis: Experiences of Hampton Roads Sanitation...

The Addition of FOG to Thermal Hydrolysis: Experiences of Hampton Roads Sanitation District's Atlantic Treatment Plant

Abstract

Advanced anaerobic digestion processes offer unique opportunities for process intensification, biosolids product production and resource recovery. Thermal hydrolysis is the current state of the art for digestion enhancement, commercially available, typically doubling the capacity over conventional systems. Co-digestion in conventional digesters has demonstrated that doubling biogas production is possible with the right mix and quantity. Combining THP with co-digestion has the potential to maximize the bioenergy yield from a fixed volume of digesters. Hampton Road Sanitation District (HRSD) as part of its recent upgrades to its 54 MGD Atlantic Treatment Plant added thermal hydrolysis (CAMBI) and FOG receiving to enhance energy generation and provide a much-needed outlet in the region for resource recovery from fats, oils and grease. HRSD installed two B-6-4 CambiTM thermal hydrolysis units at the plant which discharges thermally hydrolyzed sludge to its 6 mesophilic anaerobic digesters. HRSD had the option of FOG addition pre or post THP, but to preserve the Class A biosolids status the sludge pre-THP was selected as the process configuration. The introduction of FOG to THP requires that it achieve the same level of pre-treatment that the sludge entering it, screened to less the 5 mm and largely devoid of grit. Combining these technical requirements and lessons learned from site investigations of operating co-digestion programs a first of its kind FOG receiving station feeding THP was designed and commissioned. Figure 1, shows the general process flow of the FOG system. It was designed around the using the Envirocare Beast and a pair of heated storage tanks to raise the temperature of the FOG to 131°F prior to introduction to THP. Based on prior experience with FOG receiving station design and operations a coned bottom to the FOG storage tanks was incorporated to allow for the deposition of grit, removing it from the material fed to the THP units. The cone based design also allows for decanting and concentrating of FOG if needed; otherwise the storage tanks are completely mixed. The heated FOG is then introduced to the pulper of the THP system, in place of dilution water. An extensive characterization study by HRSD (see Table 1) of its FOG found that at an average of approximately 6% solids FOG would serve as good source of dilution water, while enhancing the energy value of the feedstock to the digesters. Since commissioning in the summer of 2021, the FOG station as operated reliably; however unanticipated repairs to FOG receiving facilities at other HRSD plants resulted in higher-than-planned FOG loading to AT throughout 2021 (Figure 2). As a result, the FOG facility at AT operated close to its peak week design basis (Table 1) nearly continuously through its startup and early operation period without undue mechanical or operational difficulties. Some early lessons learned during early operation include: - Rheological properties vary widely in high strength wastes. Screens and systems designed to process 6% FOG were able to manage 20% humus production waste - Introducing FOG to the pulper has proven reliable and viable means of maximizing the energy yield of the system. - Additional FOG water storage (or decanting, in some applications) may be a useful feature to allow additional capture of FOG through the dedicated receiving system in lieu of processing through the headworks are peak loading conditions. Storage, rather than material processing and biological processing, have proved to limit the capacity of the AT system at unanticipated high loading. Operations the THP and digesters has proven to be stable even with the high FOG loadings, demonstrating the viability of the unique microbial population attributed to THP pretreatment. This is critical in demonstrating the overall efficacy of THP to be integrated into a larger resource recovery and bioenergy program. Early biogas production numbers were hindered by system leakage but since correction, has been in line with the anticipated loadings. As part of the discussion of operations the acclimation of the digester to FOG and other high strength wastes will be discussed, as introducing FOG to a THP digester is not the same as a conventional digestion system which is inherently influenced by the feed sludge active biomass. Further at the time of presentation the THP system will have been shut down and restarted as part of it annual inspection and maintenance providing further information on the impacts of FOG and high strength waste loadings on the THP process. But also provide information on the recovery of the biological process and a return to full loading under a co-digestion scenario. Overall this information is important as the adoption of THP increases across North America and little information is currently available surrounding the integration of co-digestion with THP. At the time of presentation nearly a year's worth of data and lessons learned will have been collected and presented.

This paper was presented at the WEF Residuals and Biosolids Conference in Columbus, Ohio, May 24-27, 2022.

SpeakerMuller, Christopher

Presentation time

16:15:00

16:45:00

Session time

13:30:00

16:45:00

Session number12

Session locationGreater Columbus Convention Center, Columbus, Ohio

TopicAnaerobic co-digestion, FOG, Thermal hydrolysis

Author(s)

C. Muller

Author(s)C. Muller1; C. Wilson2

Author affiliation(s)Brown and Caldwell; 1Hampton Road Sanitation District; 2

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2022

DOI10.2175/193864718825158446

Volume / Issue

Content sourceResiduals and Biosolids

Word count17

Description: The IntensiCarbTM Technology as High-Rate Process for Anaerobic Biosolids...

The IntensiCarbTM Technology as High-Rate Process for Anaerobic Biosolids Fermentation Intensification and Nutrient Recovery

Abstract

The IntensiCarbTM Technology as High-Rate Process for Anaerobic Biosolids Fermentation Intensification and Nutrient Recovery Gholamreza Bahreini1, Masuduz Zaman1, George Nakhla1, Kati Bell2, Christopher Muller2, Jose Jimenez2, Ahmed Al-Omari2, Domenico Santoro3, Eunkyung Jang3, John Walton3, Frances Okoye4, Farokh Laqa Kakar4, Elsayed Elbeshbishy4, Ferenc Hazi5, Imre Takacs5, Sudhir Murthy6, Diego Rosso7,8* 1Department of Civil and Environmental Engineering, Western University, CANADA 2Brown and Caldwell, USA 3USP Technologies, CANADA 4Environmental Research for Resource Recovery Group, Department of Civil Engineering, Ryerson University, CANADA 5Dynamita, FRANCE 6NEWHub Corp, USA 7Civil & Environmental Engineering Department, University of California, Irvine, USA 8Water-Energy Nexus (WEX) Center, University of California, Irvine, USA *Corresponding author (e-mail: bidui@uci.edu) Abstract: The performance of an innovative vacuum-driven mesophilic anaerobic fermentation technology for the treatment of municipal biosolids was compared against a conventional fermenter. Each system was fed by a 50:50 v/v mixture of primary and thickened waste activated sludge (TWAS). The vacuum driven fermenter allowed for nearly complete decoupling of hydraulic retention time (HRT) and solids retention time (SRT). Two testing conditions with intensification factors (IF), defined as SRT/HRT, of 1.33, and 2.00, were tested. Results indicated that the vacuum-driven technology could simultaneously reduce the reactor size significantly (half of the control volume), while also enhancing process yields and nutrient partitioning between fermented solids, fermented liquid, and condensate. Specifically, relative to the conventional fermenter, the yields of volatile fatty acids for the vacuum-driven fermenter were enhanced by 29.5% (IF=1.33) and 73.8% (IF=2.00). Additionally, the hydrolysis yields increased substantially reaching 280 mg ˆ†sCOD gVSS-1 (IF: 1.33), and 321 mg ˆ†sCOD gVSS-1 (IF: 2.00), compared to 241 mg ˆ†sCOD gVSS-1 in the conventional fermenter. Specific denitrification rates using the fermentates as a carbon source were comparable with acetate. Keywords: Anaerobic Digestion; IntensiCarb Technology; Resource Recovery Introduction Sewage sludge management accounts for almost one-half of the total sewage treatment cost. Anaerobic digestion, one of the most widely used sludge stabilization and waste management techniques (Appels et al., 2008; Nguyen et al., 2021) is credited with additional energy and nutrient recovery. Contrarily, due to high solids content and complex structure, large digester volume and long SRTs are needed (Neumann et al., 2016). The vacuum-driven IntensiCarb (IC) technology (a trademark of USP Technologies) is a promising alternative to conventional anaerobic digestion of wastewater biosolids as it reduces digester volumes, transportation and energy consumption, while it increases the volatile solids removal (VSR) efficiency and facilitates separate recovery of ammonia, volatile fatty acids, and phosphorus. This process evaporates water under negative pressures and at low temperatures, which completely decouples HRT from SRT, allowing residual solids to be retained longer in the reactor, resulting in enhancement of hydrolysis and acidification of particulate organic matter. Application of vacuum pressure during IC operation also potentially can enhance the process through change in partial gas pressures in the reactors which affects dark fermentation metabolic pathways (Rajhi et al., 2016). The IC technology can effectively divert the recovered resources into separate streams by stripping almost 50% of ammonia in the condensate, while retaining the carbon (VFAs) in the fermented sludge. The concept of decoupling SRT/HRT through vacuum makes the technology more accessible to a broader range of utilities, including small municipalities as it increases the volumetric and solids loading per unit reactor volume. The evaluation of the impact of the vacuum-induced fermentation was one of the main objectives of this project. Additionally, assessment of the quality of the fermentate as supplemental carbon source for biological nutrient removal was also tested in this research. Material and methods A bench-scale IntensiCarb system (Figure 1) with operating volume of 3L was placed on a pre-calibrated induction heater connected to a vacuum pump and operated in parallel to a conventional fermenter (2L). Both ferementers were fed with 50/50 (on volumetric basis) primary and thickened waste activated sludge from the Greenway WRRF (London, ON). Operating temperature and pressure were maintained and monitored at 45 °C, and around 1015 mbar during fermentation. Vacuum was applied once per cycle intermittently at differential pressure of -900 mbar (equivalent temperature of 45 °C) for 4, and 10 hours for IC stage 1, and stage 2, respectively. System pressure and temperature of IC were continuously monitored during vacuum. The reactors were fed daily and fermented sludge was wasted daily to maintain the respective HRTs (1.50-2.25 days), while SRT was fixed at 3.0 days. Operations at conventional, IC (stage 1), and IC (stage 2) were continued until reaching to stabilized steady state condition (Î” YieldVFA ‰¤5%). Results and Discussion Cumulative VFA and soluble COD of the fermentates were plotted against influent VSS fed to the fermenters (Figure 2). Results indicate stabilized performance of the reactors with good correlations between cumulative parameters (R2>0.99) at steady state for all the tested conditions. The production yields calculated at different phases of the experiment are summarized in Table 1. As shown, operation of the reactor with the IC technology resulted in 29.5% and 73.8% increase in VFA yield (IF of 1.33, and 2.0), respectively, compared to the conventional fermenter. Additionally, the hydrolysis yield of the conventional fermentation, was enhanced by 16.2% and 33.2% through IC operation. VFA generation rate measured per unit biomass in the reactors were 28, 33, and 39 mg Î”VFA gVSSr-1 d-1 for the conventional, IC (IF: 1.33), and IC (IF: 2.00) reactors respectively. These values show the enhancement of the process in the IC reactors over the conventional fermenter (Figure 3). Thus, the IC technology not only increased volumetric and solids loadings from 0.34 (m3sludgem-3fermenter d-1), and 4.2 (kgVSS m-3fermenter d-1), to 0.44, and 0.67 (m3sludge m-3fermenterd-1), and 5.4, and 10.1 (kgVSS m-3fermenterd-1), for IC reactors operated at stage 1, and 2, respectively; resulting in processing of biosolids in significantly smaller fermenters; but also improved the VFA and SCOD yields as proven in this study (Table 1). In a typical WRRF processing 1 ton d-1 of mixed PS/TWAS, operation of an IC fermenter (IF:2.00, SRT:3 d) can reduce the fermenter size by 25% (from 3 to 2.25 m3), while increasing the VFA production by 73% (from 760 to 1330 g VFA d-1). Results from batch denitrification tests using fermentate and acetate as carbon source revealed biomass-specific maximum denitrification rates of 0.28, and 0.24 mg NO3-N mgVSSRAS-1 d-1 for acetate and fermentate, respectively, indicating a comparable denitrification potential of the fermentate as an ideal carbon source like acetate. Conclusions Intensified fermentation using the vacuum-based IntensiCarb technology could simultaneously enhance fermentation and resource recovery as well as reduce fermenter size compared to conventional fermenters. The IC fermentate showed comparable specific denitrification rates to acetate. The outcomes of this study clearly showed the tremendous potential of the vacuum-driven fermentation to reduce cost and enhance performance of the widely used anaerobic wastewater biosolids fermentation.

This paper was presented at the WEF Residuals and Biosolids Conference in Columbus, Ohio, May 24-27, 2022.

SpeakerMuller, Christopher

Presentation time

14:00:00

14:30:00

Session time

13:30:00

16:45:00

Session number14

Session locationGreater Columbus Convention Center, Columbus, Ohio

TopicAnaerobic Digestion, IntensiCarb Technology, Resource Recovery

Author(s)

C. Muller

Author(s)M. Zaman1; G. Bahreini2; G. Nakhla3; K. Bell4; C. Muller5; J. Jimenez6; A. Al-Omari7; D. Santoro8; F. Okoye9; F. Laqa10; E. Elbeshbishy11; F. Hazi12; I. Takacs13; S. Murthy14; D. Rosso15

Author affiliation(s)Residuals and Biosolids Speaker; 1Residuals and Biosolids Speaker; 2Western University; 3Brown and Caldwell; 4Brown and Caldwell; 5Residuals and Biosolids Speaker; 6Residuals and Biosolids Speaker; 7

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2022

DOI10.2175/193864718825158432

Volume / Issue

Content sourceResiduals and Biosolids

Word count15