Redmond, Eric

Eric Redmond is a speaker at WEFTEC 2026.

Titles from this speaker

Description: How Do Different Odor Management Approaches Impact Downstream Processes? Nutrient...

How Do Different Odor Management Approaches Impact Downstream Processes? Nutrient Removal, Harvesting, and Odor Control Assessed through Whole Plant Sulfur Modeling

Abstract

Odor control modeling has not been a focus of treatment plant modeling in the past, but not because of a lack of importance. Large facilities in North America can spend over $1 M USD on chemical addition and operation annually. While sewer process models such as WATS and SeweX are widely used for sulfide modeling in collections systems, integrated sulfur models for whole plant process optimization and design are still not well used in practice. Historically, odor control was often viewed as a separate "black box" from whole plant process simulation work without a significant consideration for overall process impacts. The inclusion of sulfur cycling in whole plant simulation tools has given process engineers a new tool of investigation for whole plant impacts of odor control chemical addition. The results from TRA indicate there is value from an odor control perspective, but also from a plant wide operation and nutrient harvesting perspective. Increased use of whole plant modelling in combination with collection system odor control modelling can further increase the accuracy of future evaluations.

The inclusion of sulfur cycling in whole plant simulation tools has given process engineers a new tool of investigation for whole plant impacts of odor control chemical addition. The results from TRA indicate there is value from an odor control perspective, but also from a plant wide operation and nutrient harvesting perspective. Increased use of whole plant modelling in combination with collection system odor control modelling can further increase the accuracy of future evaluations.

SpeakerRedmond, Eric

Presentation time

8:30:00

08:45:00

Session time

08:30:00

09:30:00

SessionStraddling the Fence: Odor Impacts on Neighbors and the Plant

Session number404

TopicFacility Operations and Maintenance, Odors and Air Quality, Public Communication and Outreach

Author(s)

Eric Redmond

Author(s)D.D. Brannum2; M. Young2; U. Bazemo1; L.S. Downing1; L.H. Moss1;

Author affiliation(s)Black and Veatch, Kansas City, KS 1Trinity River Authority of Texas, Arlington, TX2

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct, 2021

DOI10.2175/193864718825158101

Volume / Issue

Content sourceWEFTEC

Word count22

Intensification on the Clock: How MABR Delivers

Abstract

[b]Abstract Summary[/b] Faced with rapid growth, TRA's DCRWS plant needed interim capacity before its major expansion would be completed in 2028. This presentation explores how Membrane Aerated Biofilm Reactor (MABR) technology was selected and integrated to increase treatment capacity. Specifically, challenges related to design and construction within active basins in less than 14 months' time. [b]Introduction and Background[/b] The Denton Creek Regional Wastewater System (DCRWS), operated by the Trinity River Authority (TRA), has been experiencing rapid growth. Originally designed to accommodate a flow of 11.5 million gallons per day (mgd), the plant has experienced unprecedented growth in recent years necessitating an expansion starting in 2022. In response to this growth trajectory, TRA initiated a phased expansion plan, with Phase 1 targeting a capacity increase to 16.5 mgd. Construction for this phase started in 2024, but was just underway when the plant saw a sharp rise in flows that was higher than anticipated – approximately 1 mgd in less than a 6 months. With construction of the major expansion phase not completing until 2028 concerns were focused on maintaining treatment performance and remaining within existing permitted capacity. Recent data was used to update projections and review capacity each year until construction was completed. The secondary treatment was the primary focus with increased organic loadings resulting in a significant peak flow capacity restriction, Figure 1. To mitigate this risk, TRA authorized development of a rapid solution to increase treatment capacity ahead of the major expansion project. Due to the increasing flows, the solution would have to be implemented without taking any existing treatment units offline. [b]The Solution[/b] The preliminary assessment indicated that intensification would be the quickest way to increase capacity. Intensification in the wastewater treatment realm often refers to increasing the capacity of existing infrastructure. The intensification technology selected was the membrane aerated biofilm reactor (MABR) system. MABR is an advanced biological wastewater treatment technology that integrates gas-selective membranes and attached growth biofilm processes. The biofilm develops on the outer surface of the membrane and is exposed to the bulk wastewater on one side and to oxygen on the other, enabling stratified microbial zones: (a) Aerobic/Nitrifying Zone (b) Anoxic/Denitrifying Zone. Because a portion of the biomass is retained in the biofilm and not subject to washout, the total sludge inventory in the bioreactor can be increased without increasing the mixed liquor suspended solids (MLSS) load to the clarifier. This increased biomass retention enhanced the overall treatment capacity of the secondary treatment process, Figure 2, without requiring major changes to the clarifier or aeration volumes. [b]Design, Construction, and Installation[/b] The facility consists of three aeration basins with Aeration Basins 1 and 2 being mirror images and Aeration Basin 3 double the size with a slightly different configuration. The strategic placement of MABR cassettes in Aeration Basins 1, 2, and 3 enabled enhanced biological activity without the need for extensive downtime or reconfiguration of major unit processes. The MABR system at the DCRWS Plant consists of 14 cassettes each in Aeration Basin No. 1 and 2 and 36 cassettes in Aeration Basin No. 3, making it the largest MABR installation in the US at this time. Retrofitting new treatment technologies into existing treatment trains can be difficult. The installation at the DCRWS Plant had the additional complexities of expedited timelines and the requirement of keeping the plant online without shutdowns. The MABR technology consists of cassettes similar to MBRs but are placed within the anoxic zone and provide aeration to a biofilm rather than filtration like the MBR. These cassettes typically hang into the zone, which created a significant challenge considering 10,000 lb cassettes and spans of up to 52 feet. The requirement to not shutdown any treatment trains led to a complex structural design. The team attempted to avoid this complex design by looking at alternative solutions, such as floating the cassettes or supporting cassettes in a cage from the floor. However, these alternative methods all proved to have flaws that would be prohibitive to implementation. Therefore, all structural supports had to be designed to span the basins without any intermediate supports. A significant focus will be on the special design and construction considerations for varying basin dimensions. The site included aeration basins with spans less than 20 ft (two MABR cassettes) up to 52 ft (six MABR cassettes). The longer span required significantly more structural evaluation with the end results a bridge truss type of support structure to enable installation while the basins are in service, Figure 3 and Figure 4. To meet the increasing demands the BV team, along with the manufacturer, designed and prepared bid documents in less than 3 months. This was successful due to a collaborative design between TRA, the consultant, and contractor. The MABR is currently onsite with the first cassettes scheduled to be installed in February and the final by March, Figure 5.

This paper was presented at WEFTEC 2026 in New Orleans, Louisiana.

Presentation time

16:30:00

16:45:00

Session time

15:30:00

17:00:00

SessionA Potpourri of Biofilm Technologies

Session locationErnest N. Morial Convention Center

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

Author(s)

Redmond, Eric, Ho, Tania, Davies, Tom, Salekar, Prachi, Nash, James, Downing, Leon

Author(s)E. Redmond1, T. Ho2, T. Davies2, P. Salekar1, J. Nash1, L. Downing1

Author affiliation(s)Black & Veatch, 1Trinity River Authority of Texas, 2Black & Veatch, 1Black & Veatch, 1Black & Veatch, 1

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Sep 2026

DOI10.2175/193864718825160474

Volume / Issue

Content sourceWEFTEC

Word count8

Description: Keeping It Simple: A Flexible Low-Code Digital Twin for a Capacity-Constrained...

Keeping It Simple: A Flexible Low-Code Digital Twin for a Capacity-Constrained Wastewater Facility

Abstract

[b]Motivation and Background[/b] Wastewater utilities are increasingly embracing digitization as a path to enhance real-time decision making through accelerated access to and analysis of operational data. While this holds the promise of producing operationally relevant visuals and recommendations, there are challenges to adoption. Complex or customized workflows require substantial development and can still break with process changes or data issues. A practical approach to common process control issues which leverages available software would be valuable to the industry. In this project, Trinity River Authority (TRA) and Black & Veatch are piloting a platform centric approach with a low-code emphasis to streamline implementation of process control digital twins (PCDTs). This work began with a digital master plan to determine how to expand on ongoing work to centralize data and develop operational dashboards. Involvement from TRA's IT and operational staff was critical to understanding their digital assets and data management / governance practices. TRA leverages a Water Information System Data Repository to aggregate operational data, along with Process Modeling Simulator software and data visualization tools for dashboarding. Concurrently, plans were underway to implement cloud-based warehousing solutions (now in place) to consolidate all organizational data and enhance availability. The decision was made to pilot a commercially available platform for model deployment and integrate the model derived data into the MS environment for further analysis and visualization to achieve the desired PCDT functionality. Selected model derived data is then fed to a Fabric hosted data lake, which in turn feeds the PowerBI dashboard; the primary interface for operators. Fabric's AutoML features enables low-code/no-code machine learning (ML) operationalization to compliment mechanistic model outputs.

[b]Denton Creek Piloting[/b] TRA's Denton Creek Regional Wastewater System (DCRWS) facility was selected for piloting for several reasons: with capacity limitations and upcoming process changes being the major drivers. The facility is nearing design capacity but expansion projects, including the addition of primary treatment and expansion of secondary basins, won't be completed until 2028. As such the primary aim of the PCDT pilot is to help operators target SRTs and develop peak flow management practices to balance nitrification stability and capacity risks.
• The nitrification safety factor (NSF) is the operating aerobic solids retention time (SRT) over the theoretical washout aerobic SRT. DCRWS must often operate at relatively low NSFs while still maintaining complete nitrification, Calculating the NSF in real time and comparing past NSFs with effluent ammonia over time helps in selecting an appropriate NSF. In this way, adequate but not excessive SRT targets which account for seasonal temperatures changes can be selected.
• The online SUMO model helps to assess data quality associated with parameters needed for the SRT calculation and to troubleshoot associated SRT control issues. Online calculation of a dynamic SRT which factors in daily organic loadings enables proactive SRT control, while maintaining the NSF closer to the target.
• Even at reduced SRT operation, the clarifier solids loading rates (SLRs) are high enough that, depending on sludge volume index (SVI), the sludge blanket (SB) height can approach risky levels. Mechanistic models do not reliably capture clarifier over-loading risks, but an analysis of historical DCRWS data has shown that simple statistical models factoring in settling characteristic, loading, and operation can reasonably predict sludge blanket height at DCRWS. As such, given an SVI a maximum SLR can be set and in turn inform wet weather management decisions or to determine if lower SRT operation is worth the risk of operation at a lower NSF. These data driven models are continually verified and updated using Fabric's AutoML.
• Future flow predictions are made using weather forecasts and ML models. Upcoming wet weather conditions are then evaluated through the SUMO model by embedding standard high flow operating procedures in the model's structure and controls. Ultimately, the goal is to inform operators when equalization basins may overflow and what the impact of step feeding may be on nitrification stability.
• Dissolved oxygen (DO) control is also important to stable nitrification. The aerobic zones are plug flow but only have one DO sensor per train at the end of the zone. The online mechanistic model can provide a soft sensor for DO profile to inform aeration control. For example, how do the DO setpoints and manual airflow control valve positions impact the risk of under-aeration at the head of the aerobic zone.

Digital twin architecture diagrams and example dashboard outputs are attached, though these will evolve over the coming year as new sensors are installed to provide real-time nitrogen and organic loadings and process changes are implemented. Further in early 2026 the facility will be installing Membrane Aerated Biofilm Reactors to manage capacity, and the Digital Twin will guide startup and operation of the system to maximize capacity of the secondary treatment system. Considering these expected changes, the presentation will also cover how this approach is adaptable to process changes and new data availability.

This paper was presented at WEFTEC 2026 in New Orleans, Louisiana.

Presentation time

14:30:00

14:45:00

Session time

13:30:00

15:00:00

SessionDigital Twins for Operational Support

Session locationErnest N. Morial Convention Center

TopicFacility Operations and Maintenance, Research and Innovation, Utility Management and Leadership

Author(s)

Dunlap, Patrick, Gaidhani, Chinmay, Naranjo, David, Kisner, Scott, Ruff, Caitlin, Redmond, Eric, Masters, Elaine

Author(s)P. Dunlap1, C. Gaidhani2, D. Naranjo3, S. Kisner3, C. Ruff1, E. Redmond1, E. Masters3

Author affiliation(s)Black & Veatch, 1Georgia Tech, 2Trinity River Authority, 3Trinity River Authority of Texas, 3Black & Veatch, 1Black & Veatch, 1Trinity River Authority of Texas, 3

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Sep 2026

DOI10.2175/193864718825160516

Volume / Issue

Content sourceWEFTEC

Word count14

Description: MABRs Are Neat, But How Do I Design Them? A Practical Design Methodology for Hybrid...

MABRs Are Neat, But How Do I Design Them? A Practical Design Methodology for Hybrid MABR/AS

Abstract

Membrane Aerated Biofilm Reactors (MABR) have been applied at full-scale wastewater treatment plants since 2017 (Underwood et al., 2018) to intensify conventional activated sludge (CAS) to increase flow and/or meet stricter effluent limits. MABRs are typically installed in a pre-anoxic zone and add nitrifying biomass to increase the nitrification capacity (Houweling et al., 2017). The design of MABRs is often done using a combination of process modelling, spreadsheet mass balances, and empirical methods. The objective of this paper is to demonstrate a straightforward design methodology for MABRs that references common design practice for CAS systems.

To achieve reliable nitrification in CAS, process designers typically define a design aerobic solids retention time (aSRTdesign) by applying a safety factor (SF) to a minimum aSRT (aSRTmin) as follows.

aSRTdesign=SF x aSRTmin

Where aSRTmin is commonly defined by kinetic equations presented in Metcalf & Eddy (2014) and can be adjusted to target specific effluent ammonia concentrations across a range of design temperatures, as discussed in Chapter 1 of Houweling and Daigger (2020). Figure 1 shows representative curves for aSRTmin and aSRTdesign with a safety factor of 2 as a function of temperature for an effluent ammonia target of 1 mg/L.

In order to intensify the treatment capacity of nitrifying CAS plants, a media-supported biofilm can be added into the system to enable reliable nitrification at shorter aSRTs than would be typically used. Houweling and Daigger (2020) published a set of design curves relating the fraction of inlet ammonia treated by the biofilm, FNit,B, to aSRT and nitrification safety factor. Figure 2 shows an example of one of these curves at 15°C.

A design methodology is proposed using a combination of the theory used in Figures 1 and 2, where the designer
a) selects a safety factor and design aSRTdesign for a CAS plant to achieve their nitrification goal and,
b) correlates the aSRTdesign and safety factor to a lower aSRT (typically the aSRT available at an overloaded CAS plant, aSRTavailable) plus a fraction of influent ammonia removal by the biofilm.

Application of the design methodology is demonstrated using examples from two real-world MABR designs, with one operating MABR equipped plant and one plant that requires an upgrade using MABR.

Case Study 1
The Hespeler WWTP located in Cambridge, Ontario, Canada is a 9.32 MLD facility that was upgraded with MABR in 2022. The MABR upgrade has achieved year-round nitrification at this facility, which was previously only able to nitrify seasonally (Lakshminarasimman et al., 2023). The design criteria for the Hespeler WWTP was to achieve an effluent of 5 mg/L as ammonia nitrogen at a temperature of 10°C with as low as 4 to 5 day aSRT in the aeration tanks (Natvik et al., 2020).

Figure 3 shows the conventional nitrification curves for the Hespeler case, targeting an effluent ammonia concentration of 5 mgN/L. At 10°C the aSRTmin to achieve 5 mgN/L is 5 days, whereas the aSRTdesign with 1.5 times safety factor is 7.5 days.

Applying the design points to the biofilm safety factor curves by Houweling and Daigger as shown in Figure 4, a 7.5 day aSRT corresponds approximately to a SF of 1.5 when FNit,B = 0. To maintain the nitrification safety factor at 1.5, some removal on the biofilm is required. In this case a 5 day aSRTavailable at SF of 1.5 corresponds to an FNit,B of 0.42, meaning that 42% of the influent ammonia must be removed in the biofilm.

The Hespeler WWTP has 36 ZeeLung™ MABR cassettes by Veolia with 1,920 m2 of surface area each for a total of 69,120 m2. At an average nitrification rate of 1.7 gN/m2/d the MABR will remove 117.5 kgN/d. The influent design ammonia load is 260 kgN/d. Therefore, the MABR will remove 45% of the influent ammonia load, which approximately corresponds to the design points illustrated in Figures 3 and 4.

Case Study 2
A wastewater plant in Texas, USA is approaching design capacity and requires a biological upgrade within a short time frame. The plant has a design temperature of 20°C and is required to meet a monthly effluent ammonia limit of 1.4 mgN/L and can operate at a bulk aSRTavailable of 4.3 days. Figure 5 shows the conventional nitrification curves for the Texas case for a target effluent ammonia of 1.4 mgN/L at 20°C where aSRTmin is 2.8 days and aSRTdesign is 5.5 days with a SF of 2.

Applying a 5.5 day aSRTdesign to the biofilm safety factor curves at 20&Deg;C corresponds to a SF of ~2.25, as shown in Figure 6. In order to maintain a SF of 2.25 at an aSRTavailable of 4.3 days an FNit,B of 0.29 is required.

The influent ammonia load for the Texas WWTP is 1340 kgN/d. To achieve a 29% ammonia removal, 389 kgN/d are required to be removed by the MABR biofilm. Assuming a nitrification rate of 2.6 gN/m2/d, a surface area of ~150,000 m2 is required.

The designs in case studies 1 and 2 use different safety factors, where a less stringent ammonia limit requires a lower safety factor and vice versa. Recommendations for safety factor for ranges of effluent ammonia limits will be presented along with one or more additional case studies.

This paper was presented at WEFTEC 2025, held September 27-October 1, 2025 in Chicago, Illinois.

Presentation time

13:30:00

14:00:00

Session time

13:30:00

15:00:00

SessionExploring the Capability and Flexibility of MABRs

Session locationMcCormick Place, Chicago, Illinois, USA

TopicLiquid Stream Treatment Technology - Secondary & Tertiary Treatment

Author(s)

Reeve, Matt, Houweling, Dwight, Downing, Leon, Redmond, Eric, Cecconi, Francesca

Author(s)M. Reeve1, D. Houweling2, L. Downing3, E. Redmond3, F. Cecconi3

Author affiliation(s)Veolia Water Tech1, Polytechnique Montreal2, Black & Veatch3

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Sep 2025

DOI10.2175/193864718825160087

Volume / Issue

Content sourceWEFTEC

Word count17

Description: Next Steps: Secondary Clarification Design and Operation as the Result of Aerobic...

Next Steps: Secondary Clarification Design and Operation as the Result of Aerobic Granulation

Abstract

Aerobic sludge granulation is an area of interest from both a research and implementation standpoint. Significant advancements have occurred at both the lab and full-scale levels that have furthered understanding on primary mechanisms for granule formation. As this work continues to advance a necessary compliment to this is also how sludge granulation impacts other processes, specifically secondary clarification. This paper and presentation will begin to highlight the potential considerations related to clarification, underflow, and influent configurations as they relate to sludge granules. One well understood aspect of sludge granulation is the increased clarification capacity as a result, however realizing and taking advantage of this capacity must also be understood.

SpeakerRedmond, Eric

Presentation time

13:20:00

13:40:00

Session time

13:00:00

14:00:00

SessionSettle Down! Case Studies of Secondary Clarifier Improvements

Session number604

TopicFacility Operations and Maintenance, Municipal Wastewater Treatment Design

Author(s)

L. DowningB.D. ShoenerE. RedmondE. Redmond

Author(s)L. Downing1; B.D. Shoener2; E. Redmond3; E. Redmond3;

Author affiliation(s)Black & Veatch, WI1; Black & Veatch, IL2; Black and Veatch, IA3

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2020

DOI10.2175/193864718825157570

Volume / Issue

Content sourceWEFTEC

Word count14

Description: Operational Considerations for Integration of AquaNereda Reactor Expansion with an...

Operational Considerations for Integration of AquaNereda Reactor Expansion with an Existing Activated Sludge Facility

Abstract

Introduction The application of the AquaNereda® process, were aerobic granular sludge (AGS) is applied in a sequencing reactor, is often seen as a replacement for the conventional activated sludge process. AquaNereda(R) is a sequencing process that utilizes a single tank for react and settle phases, and therefore is often not compatible as a retrofit with existing activated sludge systems that utilize separate tanks for reaction (aeration basins) and settle (final clarifiers). While this can be seen as a limitation for the application of AquaNereda(R), there is an opportunity to construct an expansion of facilities with AquaNereda(R), and then integrate the AquaNereda(R) in parallel to a conventional activated sludge plant. Four Rivers Sanitation Authority (FRSA), located in Rockford, Illinois, is currently working towards this integrated overall facility. While maintaining 40 mgd of average day flow capacity in a more conventional biological nutrient removal (BNR) activated sludge facility, FRSA is adding an additional 10 mgd of average day flow capacity with a new AquaNereda(R) AGS facility. The AGS facility will be operational in 2025, with the BNR upgrades being completed in 2026. During design of the new facilities at FRSA, the largest question for integration of the processes became how to manage the waste activated granular sludge (WAGS). Given the characteristics of WAGS in terms of percent solids as well as the sequencing wasting schedule from AquaNereda(R), it was decided to send the WAGS into the activated sludge system and then to waste to solids handling (see Figure 1 for a process flow diagram). The waste activated sludge (WAS) would then contain flocs from the activated sludge process as well as WAGS. This simplified operation, but there were major questions related to the impact of WAGS on the activated sludge process. Potential oxygen demand impacts, nitrification rates, and settling rates were all of interest to FRSA to understand the impact of WAGS. While most facilities would rely solely on process modelling to assess these impacts, FRSA has access to WAGS for testing. The AquaNereda(R) demonstration facility is on site and operating with FRSA wastewater. This facility (treating 200,000 gpd) generates WAGS that can be utilized for testing. Approach and Methodology To help understand the impacts and strategies to manage WAGS from the AGS facility, a series of bench scale tests were completed using WAGS from the AquaNereda(R) demonstration facility and WAS from the existing FRSA aeration basins. Three sets of bench scale tests were completed:

*Settling rate testing to identify potential enhanced settling, as outlined by Daigger, Redmond, and Downing (2017)

*Specific oxygen uptake rate (SOUR) measurement, utilizing standard methods, to assess the oxygen demand of the WAGS. The WAGS have the potential to exert a significant oxygen demand, as past work has shown a biomethane production potential of WAGS that is similar to primary sludge (Guo et al., Digestibility of waste aerobic granular sludge from a full-scale municipal wastewater treatment system, 2020).

*Nitrification rate testing, as outlined by Melcer et al (2003), to identify any potential seeding effect from WAGS. Results and Outcomes To evaluate the effect of WAGS on the settling characteristics of the existing waste activated sludge (WAS), batch settling experiments were performed using WAS and a mixture of WAGS-WAS at various dilution ratios to generate settling curves. The WAGS-WAS mixture proportions were calculated based on the predicted WAGS flows from the new AGS facilities. Figure 2 provides the settling rate impacts. Addition of WAGS increased the settling rate of the activated sludge biomass. The effect on settling rate would increase the peak flow capacity of the activated sludge facilities from 110 mgd to 130 mgd. SOUR testing indicated that the WAGS would have a 25% higher oxygen uptake rate than WAS (Figure 3). This indicates that there will be an oxygen demand associated with either particulate COD bound in the WAGS or potentially stored carbon. This oxygen demand is considered during aeration operation in the activated sludge system. The nitrification rate of WAGS (4 mgN/gVSS-hr) was similar to the nitrification rate of WAS (3.9 mgN/gVSS-hr). This was an unexpected result, as the WAGS likely contains a high VSS content of particulate COD from the influent. The benefit is that the WAGS will be adding a significant load of nitrifiers into the activated sludge system, increasing system resilience. The outcomes from this testing highlight how construction of an AquaNereda(R) facility in parallel to an activated sludge facility can provide a net benefit to the activated sludge facility. Applicability AquaNereda(R) has been sold as the evolution of activated sludge, but the requirement for a sequencing reactor can been seen as a limitation. The work completed highlights how an AquaNereda(R) process can be constructed in parallel to an activated sludge system, with positive impacts on the activated sludge facility. Audience Appeal Anyone looking at process expansion, nutrient removal requirements, and aging infrastructure would benefit from this presentation.

Application AquaNereda®, where aerobic granular sludge (AGS) is applied in a sequencing reactor, is often seen as a replacement to conventional activated sludge. During design FRSA facilities, the largest question for integration of the processes became how to manage the waste activated granular sludge (WAGS). The decision to send WAGS into the activated sludge system was informed by bench results showing positive improvements to SVI, stored carbon diversion and no nitrification impacts.

SpeakerDowning, Leon

Presentation time

13:30:00

14:00:00

Session time

13:30:00

15:00:00

SessionEvaluating Plantwide Impacts of AGS and DAS

Session number606

Session locationRoom 343

TopicIntermediate Level, Municipal Wastewater Treatment Design, Nutrients, Research and Innovation

Author(s)

Downing, Leon, Loconsole, Jennifer, Redmond, Eric

Author(s)L.S. Downing1, J.C. Loconsole2, E.D. Redmond3

Author affiliation(s)1Black and Veatch, WI, 2Black & Veatch, IL, 3Black & Veatch, IA

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2024

DOI10.2175/193864718825159637

Volume / Issue

Content sourceWEFTEC

Word count15

Primary Filtration Waste: How Do We Handle This High Volume Waste? Completing the Carbon Diversion PFD - SAF Pilot Results

Abstract

Introduction Intensification processes have been a focus largely for secondary and anaerobic treatment processes. These approaches have enabled utilities to increase performance, reduce footprint, and enable carbon redirection and capture. As we continue to evaluate drivers that include capacity, nutrient removal, carbon redirection, intensification, and energy reduction, enhanced primary treatment (EPT) plays a key role to whole facility integration considerations. Primary filtration technologies are increasingly evaluated as an alternative that enables high carbon redirection through >80% TSS and 50 to 70% BOD capture in a footprint that is approximately 25% of conventional primary clarification. This technology offers significant opportunity for facilities to divert carbon from liquid stream systems to anaerobic digestion, saving on aeration costs and increasing biogas production. However, full integration into existing facilities requires consideration to existing thickening facilities. Primary filter sludge is a high volume, low concentration that is 2 to 3x the volume seen with conventional primary clarifiers with a concentration of 3,000 to 5,000 mg/L. Further, the characteristics of the waste stream include a significant increase to non-settleable TSS and colloidal material that was previously not captured with conventional primary treatment. A comparison of anticipated capture efficiencies of thickening technologies (Figure 1) and footprints (Figure 2) indicates conventional gravity thickeners are significantly disadvantaged compared to other mechanical thickening technologies. Primary filter technologies are often solids limited vs. hydraulically limited (as in the case of tertiary filters). A reduction in capture efficiency of 5 to 10% has a resulting impact to filter loading rates, increasing surface area requirements by an equivalent rate. This technology review also indicated a potential opportunity for Suspended Air Flotation (SAF), offering a high hydraulic loading rate with potentially high capture efficiencies. SAF, provided by Heron Innovators, is similar to dissolved air flotation thickening but uses a surfactant to aid in solids separation and flotation. However, the technology had no primary sludge (filter or clarifier) thickening references and limited municipal waste activated sludge (WAS) case studies (with most installations to date being industrial applications). The Trinity River Authority of Texas (TRA) will soon be expanding the Denton Creek Regional Wastewater System (DCRWS) Facility. One component of the proposed expansion is the addition of primary filters. A preliminary assessment of a range of thickening technologies using economic and noneconomic factors indicated that SAF thickening could offer substantial economic benefits to TRA. Potentially, the SAF system could require the least amount of equipment, which correlates to a smaller footprint, and low chemical conditioning requirements, which translates to lower operations costs. As a result of the evaluation of technologies, SAF was selected as the basis of design for co-thickening blended (primary and waste-activated) solids. The decision to select SAF as the thickening option in this design constitutes an uncommon and innovative use of this technology. To confirm suitability of SAF for primary filter applications and to better understand the key design parameters driving SAF performance in the blended solids thickening application at DCRWS, a SAF pilot study was conducted at the Ten-Mile Creek Regional Wastewater System (TMCRWS) Facility. TRA and BV worked with Herron Innovators, Inc., providers of the SAF technology, to develop the pilot test. SAF systems are similar in concept to the older dissolved air flotation (DAF) systems in that both technologies float solids to the top of their respective tanks for thickening and removal. The key difference is that DAF systems use pressurized air dissolved in water while SAF systems instead employ a surfactant charged emulsion of air and water (also referred to as 'froth') to efficiently float solids. This allows SAF systems to achieve high solids loading rates (SLRs), which reduces equipment and space requirements. Table 1 provides a summary of key design criteria comparing DAF and SAF technologies. The SAF pilot setup explored low solids concentration, high volume feed solids conditions indicative of primary filter solids and blended solids (primary solids + WAS) thickening applications. Key questions were explored related to hydraulic and solids loading rates as well as polymer and froth dosages, to determine what targets for each of these primary design criteria are best correlated with overall thickening performance in terms of solids capture and the resulting thickened solids concentrations. The pilot was operated for a total of five weeks to test a range of loading rates and scenarios. Pilot Setup The SAF pilot study was conducted at TMCRWS from July 11th through August 18th, 2023. The study setup included a trailer-mounted pilot-scale SAF unit provided by Heron, specifically the CF125 model, which has a flow capacity of 350 gpm and a flotation area of 17 ft2. Throughout the study, TRA staff collected samples twice daily for analysis. Results The results of the pilot study which will be elaborated on in the full paper, include:

*Capture Efficiency oPrimary Solids Capture Efficiency — the primary solids thickening performance was excell

Primary filtration, increases capture efficiencies in a small footprint. However, the backwash creates challenges due to the large volume and low concentrations. Pilot study focused on Suspended Air Flotation (SAF), with primary and blended sludges. Results indicate SAF linked with primary filters is capable of high loading rates, 5 to 10x that of conventional dissolved air flotation (DAF), with capture efficiencies of 95% and 5% thickened sludge.

SpeakerRedmond, Eric

Presentation time

09:30:00

09:50:00

Session time

08:30:00

10:00:00

SessionThickening and Dewatering: Design Considerations

Session number301

Session locationRoom 354

TopicBiosolids and Residuals

Author(s)

Redmond, Eric, Knight, Greg, Ruff, Caitlin, Harness, Crystal, Downing, Leon

Author(s)E.D. Redmond1, G. Knight2, C. Ruff3, C. Harness4, L.S. Downing5

Author affiliation(s)1Black & Veatch, IA, 2Black & Veatch, GA, 3Black & Veatch, TX, 4, TX, 5Black and Veatch, WI

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2024

DOI10.2175/193864718825159648

Volume / Issue

Content sourceWEFTEC

Word count21

Description: Quaternary Ammonia Compounds: Why are they so common, and why is nobody talking...

Quaternary Ammonia Compounds: Why are they so common, and why is nobody talking about them?

Abstract

Abstract
Quaternary Ammonia Compounds (QACs) have long been recognized as niche contaminants in specialized industries outside of municipal wastewater treatment. They are known to affect biological processes, for example anaerobic digestion in agriculture settings. They are not regulated and are widely ignored as a factor for municipal wastewater treatment. Their use in everyday life skyrocketed following two pivotal moments: the ban on triclosan and triclocarban in soap products and the pandemic that resulted in widespread use of disinfection sprays across our society. Here, we report on two completely different wastewater treatment plants that had to deal with QACs causing upset to their biological processes (nitrification at one plant and anaerobic digestion at another plant). We employed contract labs to quantify QACs in influent wastewater along with toxicity testing. In one case, a new food preparation facility in Texas was utilizing cleaning products for daily routine cleaning and periodic deep-cleaning of specific equipment, unaware that the products contained QACs that could potentially cause an upset at the local wastewater treatment facility. One of their cleaning products they used was a detergent commonly used in households for dishwashing. Working closely with the local wastewater treatment, the facility significantly reduced their use of these products to enable them to safely discharge their effluent. At the other facility, QACs were attributed to upset startup with anaerobic digestion. We will present results on QACs and biological process function along with the models we employed to identify and remediate QAC issues.

Background
Quaternary ammonia compounds (QACs) are a class of compounds widely used for their disinfecting ability in the food industry for cleaning process lines as well as in the agricultural industry. QACs are the main active ingredient in disinfecting cleaner sprays (for example, Lysol) and liquid soap. QACs are widely used everyday, and they are widely detected in WRRFs (Mahoney et al., 2023).

QACs are used because they are intended to have negative consequences on microbial activity. Yet, WWRFs rely on microbial communities to carry out important processes, including nitrification and anaerobic digestion. While it is recognized that QACs can inhibit biological processes at WRRFs (Lu et al., 2024), they are rarely suspected to be the culprits for process upsets in everyday life. QACs are not regulated so they are not monitored. QACs are a broad class of compounds with several subgroups of chemicals. The variety of chemical types leads to a variety in inhibition.

This presentation will discuss completed results from two separate case studies on WRRFs that dealt with QAC problems. One was a small WRRF that knew where a primary source of QACs were originating from (Figure 1). We reveal how analytical chemistry work and modeling (Figures 1-3) allowed us to find another unsuspected source of QACs in the community. The second case study involved issues with QACs on the aeration basin that were caused by alterations in the sludge stabilization processes from supernatant recycle.

Methods and Results

Case Study 1
A small (<5 MGD) WRRF received discharge from a food processing facility, and was dealing with upsets to their mainstream biological treatment process. The facility worked closely with the WRRF to investigate their potential impact, substituting and reducing QAC-containing cleaning products and using a combination of toxicity testing of their discharged effluent with QAC analysis of wastewater to develop a management strategy. A dynamic model of the collection system upstream of the plant was developed to investigate ways of mitigating potential spikes in QAC concentrations that could cause problems for the WRRF. The model was developed using the GPS-X 8.1 simulator with an industrial pollutant library (Figure 2).

The investigation for the food preparation facility included two major tasks: (1) estimation of QAC concentrations and (2) toxicity testing. For the former, a process simulator was used to assess the dynamic impact of the discharge through a series of lift stations and altering their operation (depth used and flows) was modeled to show that they could lower the potential QAC spikes (Figure 3).

Toxicity testing revealed that the facility effluent did not decrease the measured SOUR, indicating it was not toxic to aerobic activity (including nitrification).

Case Study 2
A large (>50 MGD) WRRF employed a new process to improve anaerobic digestion. The process employed a pretreatment process that improved anaerobic digestion. However, the WRRF routinely monitored for QACs and noticed high concentrations in supernatant. The supernatant was recycled back to the head of the plant and coincided with decreased performance in the aeration basin. In this case, proactive monitoring of QACs allowed for easier assessment of the problem. QACs are not regulated so many WRRFs do not measure QACs. This case study will highlight lessons learned on how QACs can be released to the soluble phase and alter processes during startup.

A large utility monitored QAC in their aeration basins, raw influent and sludge processing units for 6 years. The data show a significant increase in QAC concentrations in the aeration basins. The increase correlates with the installation of a new anaerobic digester, likely caused by the recycle streams.

This paper was presented at WEFTEC 2025, held September 27-October 1, 2025 in Chicago, Illinois.

Presentation time

13:30:00

14:00:00

Session time

13:30:00

14:30:00

SessionCan Current Knowledge of CECs Keep Future Contaminants from Emerging?

Session locationMcCormick Place, Chicago, Illinois, USA

TopicContaminants of Emerging Concern & Trace Organics

Author(s)

Mcnamara, Patrick, Shaw, Andrew, Redmond, Eric, Hunter, Gary, Bazemo, Ulrich