Hunter, Gary

As a global process technology specialis assigned to Black Veatchs Water Technology Group, Mr. Hunter is responsible for process evaluation for both domestic and industrial wastewater treatment facilities. In this role, he is responsible for industrial pretreatment programs, treatment of emerging contamiants, domestic, disinfection facilities, and industrial reuse, and sustainability measures at treatment facilities. He has gained expertise in the design, operation and troubleshooting of wastewater treatment processes. Mr. Hunter holds a BSCE and MSCE from Brigham Young University. In addition he holds a BCEE and is an ENVSP certified engineer.

Titles from this speaker

A New Light UVC-LED for Wastewater Disinfection

Abstract

The growth of UltravioletC Light Emitting Diode (UVC-LED) systems in the water and wastewater market has been occurring at a geometric. Based on a recent survey (Cosman 2019) the number of vendors providing UVC-LED system has increased from 3 in 2017 to over 18 in 2019. While not all the companies provide systems for water and wastewater applications, the interest and growth of the UVC-LED vendors is occurring at a very rapid pace. The Electric Power Research Institute (EPRI) (2019) estimated the UVC-LED systems would reduce the capital cost of UV systems by 75 percent and the power use by 50 percent in the wastewater industry. Aqua-Aerobic Systems Inc. (Aqua-Aerobic) installed the METWATER UVC-LED unit at its Rockford, Ill test facility. Validation test runs were completed using filtered effluent as well as secondary treated effluent to determine the effectiveness of the unit in treating wastewater. A combination of various test runs were completed to determine the conditions under which the unit could be used to treat wastewater. Based on these results, computational fluid dynamic (CFD) and light intensity modeling was recommended to develop a plan to increase the treatment capacity of the test unit. The procedures for the models have been completed, however the actual runs have not been completed due to issues related to COVID-19. It is anticipated that the results of the model will show that a change to inlet conditions as well as baffling may need to be incorporated into the design of the existing unit to improve its overall effectiveness.

SpeakerHunter, Gary

Presentation time

08:30:00

08:50:00

Session time

08:30:00

09:50:00

SessionDisinfection on The Edge

Session number313

TopicDisinfection and Public Health, Research and Innovation, Water Reuse and Reclamation

Author(s)

G. HunterW. DeckerG. SmithR. SimonsO. Lawal

Author(s)G. Hunter1; W. Decker2; G. Smith2; R. Simons3; O. Lawal3;

Author affiliation(s)Black & Veatch, SC1; Aqua-Aerobic Systems, Inc2; AquiSense Technologies3;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2020

DOI10.2175/193864718825157849

Volume / Issue

Content sourceWEFTEC

Word count8

Comparing Four Innovative Technologies for Enhanced Leachate Treatment: An Evaluation of PFAS Foam Fractionation Efficacy

Abstract

Introduction: PFAS, a group of chemicals widely used in various applications due to their water and oil resistance, are persistent, toxic, and accumulate in the environment. Disposal of products containing PFAS in landfills can result in PFAS contamination in the landfill leachate that is discharged to water resource recovery facilities (WRRFs) andwhich can lead to groundwater contamination (REF1). Foam fractionation (FF) is a process that utilizes the surfactant nature of PFASs to separate them into foam, which is collected as a concentrate for further treatment (REF2). FF significantly reduces the volume of PFAS-containing waste, making it an ideal first step in a PFAS treatment process. This study evaluates four different FF technologies and provides insights for their implementation based on bench scale comparison results. Materials and methods: In this study, four technologies were evaluated for PFAS removal. The technologies and their providers are listed as TechA, TechB, TechC, and TechD in Table 1. Equalized volume samples (55 liters) were collected from an anonymous facility's EQ-tank and distributed to different technology providers for testing. Leachate wet chemistry parameters samples were determined in accordance with APHA standard methods. Table 2 lists the analyzed parameters. A total of 40 PFAS compounds were quantified using the EPA 1633 method, the Total Oxidizable Precursor, and the Total Organic Fluorine assay. Table 3 provides a complete list of these compounds and their concentrations before FF. Results and discussion PFAS Removal Efficiency: The study evaluated the removal efficiency of different PFAS into the foam phase for the four FF technology providers. The findings, depicted in Figure 1, align with previous literature: longer fluorocarbon chains and the presence of a more surface-active sulfonic acid head group result in greater PFAS removal compared to its carboxylic counterpart. The study also shows that removal efficiency improves exponentially with longer fluorocarbon chains, and chains longer than six carbons resulted in undetected levels. This supports previous research that suggests chain length has a greater impact than head group. Longer fluorocarbon chains make PFAS less soluble and more hydrophobic, enhancing its ability to adsorb onto air-water interfaces due to their superior surface properties. Impact of Process Configuration: Technology providers employed different strategies in using FF as indicated in Table 1. A notable finding from comparing these technologies is the effectiveness of cationic co-surfactants in removing PFAS. The cationic headgroup of these co-surfactants allows for binding to PFAS at the water-air interface. TechA and TechB tested a wide range of co-surfactants at 100 mg/L and found that CTAB-based surfactants are favorable in reducing the short-chain compounds up to 50% removal. The consistent observation of the use of co-surfactants showed enhanced stability and density of the foam that helps accumulate more foam and minimize the extent of interstitial liquid drainage before the foam is harvested (REF4). However, TechC experiments showed no impact of using 8 mg/L co-surfactant compared to the absence of co-surfactant. This can be attributed to reduction of additive performance due to electrostatic uptake by competing contaminants in leachate, suggesting the need for a higher dose. For TechC it was found that a 45-minute contact time is sufficient to achieve non-detection levels of long-chain PFAS in a leachate primarily dominated by PFCAs. The study also assessed the impact of the number of FF units in series, with the consensus being that using two to three treatment units is adequate to achieve the desired removal. TechD's proprietary model approach showed that increasing the treatment stages from 3 to 5 resulted in a 10% increase in the removal of short-chain PFAS, while long-chains remained non-detectable in both cases. TechC's unique two-stage method involves de-foaming the leachate from the first fractionation unit and then re-foaming the primary foamate generated over repeated primary fractionation cycles (Figure 2). This approach significantly reduces generated foam volumes, condensing the volume of foam by up to 180 times in the secondary foamate, minimizing the capital and operating costs associated with downstream destruction technologies. Conclusions 1.Findings of this work are illustrated in Figure 3. 2.Long-chain PFAS have been effectively removed to below detection limit, while short-chain PFAS require a polishing step using adsorptive media due to their low removal rate. However, this poses challenges due to the high fouling potential of the media. Therefore, the implementation of FF and modifications to its configuration strongly depend on treatment objectives and upcoming regulations. 3.For the specific leachate that was tested, a 45-minute contact time of and up to three treatment stages in series were sufficient for removing long-chain PFAS. However, these factors may vary based on the quality of the leachate water being treated. 4.FF is a highly selective method for removing surfactants without altering effluent water quality. This results in an effluent with similar water quality to the influent but significantly reduced concentrations of PFAS, VOCs, total suspended solids, and iron.

This article discusses how foam fractionation (FF) technology can effectively remove Per- and Polyfluorinated Substances (PFAS) from landfill leachate. The study found that FF is a highly selective method for removing surfactants without altering effluent water quality. These findings are crucial in addressing PFAS contamination in landfills and guiding the implementation of different FF configurations for PFAS removal.

SpeakerSabba, Fabrizio

Presentation time

13:30:00

13:50:00

Session time

13:30:00

15:00:00

SessionPFAS Removal and Destruction Using Novel Technologies

Session number605

Session locationRoom 244

TopicIndustrial Issues and Treatment Technologies, Intermediate Level, PFAS, Research and Innovation

Author(s)

Sabba, Fabrizio, Kassar, Christian, Hunter, Gary, Downing, Leon

Author(s)F. Sabba1, C. Kassar2, G.L. Hunter3, L.S. Downing4

Author affiliation(s)1Black & Veatch, NJ, 2Black & Veatch, AZ, 3Black & Veatch, SC, 4Black and Veatch, WI

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2024

DOI10.2175/193864718825159515

Volume / Issue

Content sourceWEFTEC

Word count16

Description: Emerging Separation and Destruction Technologies to Mitigate PFAS in Leachate...

Emerging Separation and Destruction Technologies to Mitigate PFAS in Leachate Destined for a Municipal Water Resource Recovery Facility

Abstract

Per- and polyfluoroalkyl substances (PFAS) have substantially altered our water and wastewater management landscape. It is now critical to understand sources of PFAS into municipal water resource recovery facilities (WRRFs) so that technologies can be assessed for PFAS reduction when needed. Landfills often have high levels of PFAS from the breakdown of consumer products that are composed of PFAS. Leachate is often sent to WRRFs and can be a notable source of PFAS to the WRRF. Reduction of PFAS in the leachate can be beneficial in light of limitations on biosolids land application due to PFAS, effluent surface water limit guidelines, and drinking water concerns when source water is heavily influenced by wastewater effluent. Leachate is a complicated matrix though, and assessment of technologies requires testing on actual leachate samples. Technologies can be categorized into two classes. Separation Technologies can remove PFAS from one phase (such as water) and concentrate the PFAS into another phase. These technologies remove PFAS, but they do not destroy PFAS. Destructive Technologies can actually break the carbon-fluorine bond and thereby destroy PFAS.

Objectives
The objective of this research study was to assess the suitability of both separation and destruction technologies on PFAS removal. Specifically, four emerging technologies were evaluated. Foam Fractionation can concentrate PFAS into a foam phase and remove PFAS from water by addition of air and/or surfactants. Electrochemical Oxidation generates radicals in-situ that can breakdown chemical bonds in PFAS. Supercritical Water Oxidation applies high temperature and pressure to breakdown chemical bonds. Lastly, thermal plasma employs a plasma torch to generate reactive oxidants and reductants to oxidize PFAS. These four technologies were assessed for PFAS removal, and their advantages and disadvantages were evaluated.

Status
Bench-scale studies on all four of these technologies have been completed for assessment of leachate treatment. PFAS analysis in the influent and effluent samples is complete.

Methodology
A municipal landfill's leachate-receiving facility provided samples from their equalization basin for shipment to each of the treatment vendors. Each technology treated 55 liters of leachate samples. Samples were analyzed for influent, effluent and intermediate (both foamate and liquid samples). Forty PFAS were analyzed using EPA 1633 method. Conventional water quality parameters in leachate were analyzed, including hardness, metals, pH, ammonia, nitrate, nitrite, total organic carbon, volatile organic compounds, and solids.

Findings
Foam Fractionation was tested as a technology that could concentrate PFAS in leachate and remove it from the water phase. In general, this technology was good at removing long-chain PFAS (Figure 1). PFBS, a short-chain PFAS, had negligible removal (Figure 1). Foam fractionation has low operational cost and is easy to operate, but it does not effectively remove all PFAS, and the foam fraction requires further processes because of its higher PFAS concentrations.

Two different SCWO technologies were assessed, and both technologies removed PFAS to below detection limit (Table 1). These results are not surprising because SCWO is a high temperature high pressure system. Advantages of SCWO are that it proves non-selective removal of PFAS, i.e., it removes both short and long-chain PFAS. Disadvantages include possibilities for corrosion and fouling as well as salt precipitation.

The results from the electrochemical oxidation tests were interesting as they showed that long-chain PFAS were effectively removed over time, while shorter chain PFAS, specifically PFBS, showed variable concentrations (as depicted in Figure 2). It is plausible that these short-chain PFAS were accumulated from the breakdown of longer-chain PFAS. One advantage of electrochemical oxidation is that it operates at ambient conditions and does not require substantial external additives. However, it does necessitate the use of electrodes, which can be costly, and it can generate short-chain PFAS.

Significance
These findings are important because they illuminate that there are viable technologies for removal of PFAS from landfill leachate, in particular long-chain PFAS including PFOS and PFOA. These two chemicals are of particular interest for land application of biosolids because several states use them for their interim guidelines on land application. Reducing PFAS in leachate that is destined for a WRRF would ultimately reduce PFAS levels in biosolids as well as wastewater effluent. Treatment of landfill leachate could be one targeted area to reduce the perpetual cycling of PFAS through the urban water cycle.

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

Presentation time

16:30:00

16:45:00

Session time

15:30:00

17:00:00

SessionPFAS Removal Technologies for Leachate and Complex Wastewaters

Session locationMcCormick Place, Chicago, Illinois, USA

TopicContaminants of Emerging Concern & Trace Organics

Author(s)

Mcnamara, Patrick, Sabba, Fabrizio, Kassar, Christian, Hunter, Gary

Author(s)P. Mcnamara1, F. Sabba1, C. Kassar1, G. Hunter1

Author affiliation(s)Black & Veatch; Marquette University1, Black & Veatch, Syracuse University1, Black & Veatch1, Black & Veatch1, , , ,

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Sep 2025

DOI10.2175/193864718825160155

Volume / Issue

Content sourceWEFTEC

Word count19

Improved Operating Practices for Emerging UV Systems

Abstract

UV systems are emerging as a cost-effective, reliable approach to disinfect treated wastewater effluent. As these new UV systems are brought to the market, effective operation and maintenance approaches must be developed and validated to ensure that facilities using these emerging UV alternatives can maintain compliance at sustainable and reliable operating costs. Over the past several years, two emerging UV systems that have shown promise for implementation at water resource recovery facilities are HOD UV and the UVC-LED systems. With these new UV systems entering the market, there is a need to understand the operating procedures required by these new systems and to determine how to improve existing operating practices. A comparison of operational and maintenance activities of Hydro Optic Disinfection Ultraviolet light (HOD UV) and Ultraviolet Light C - light emitting diodes (UVC-LED) was made to practices employed by WRRF staff. Proper operation and maintenance activities may result in longer life, resulting in lower operating costs.

Operational and maintenance activities are for critical for the optimized performance ultraviolet (UV) system. Two emerging UV systems UVC- light emitting diode (LED) and hydro optic disinfection (HOD) -UV. UVC-LED systems are projected to provide a 30 percent reduction in capital cost and 50 percent reduction in operating cost over traditional UV systems. HOD UV systems appear to be more efficient in the deployment of the UV dose which allows for less equipment to be used resulting in the reduction of operating and maintenance costs. This presentation provides a comparison of traditional UV operating and maintenance practices to those used by emerging UV systems

SpeakerHunter, Gary

Presentation time

8:30:00

08:45:00

Session time

08:30:00

10:00:00

SessionRiding the UV Wave: Tracking the Evolution of UV Technology (UV-LED) and New Applications

Session number402

TopicDisinfection and Public Health, Energy Production, Conservation, and Management, Facility Operations and Maintenance

Author(s)

Gary Hunter

Author(s)G.L. HunterNo Number Attached; L. Casson6; B. Drouhard2;K. Fredrickson1;D. Bitter3;B. Decker4;O. Lawal5;

Author affiliation(s)Black & Veatch Corporation, Greenville, SC1Black & Veatch Corporation, Atlanta, GA2Atlantium Technology, Lakewood Ranch, FL3Aqua-Aerobic Systems, Inc, Loves Park, IL4AquiSense Technologies, Erlanger, KY5

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct, 2021

DOI10.2175/193864718825158099

Volume / Issue

Content sourceWEFTEC

Word count8

Machine Learning In The Dark: Disinfection With <55% UV Transmittance

Abstract

Introduction: UV disinfection systems have gained popularity in wastewater disinfection applications as they can inactivate microorganisms while avoiding the injection of a chemical and any risk of a high disinfectant demand or disinfection byproducts. UV disinfection process design must account for UV Transmittance (UVT) which is a critical parameter that characterizes the ability of UV photons to pass through water and reach a microbiological target. Monitoring of UVT is achieved by online or benchtop readings, but online data can be skewed by sensor drifting or water quality impacts. Black & Veatch worked with two wastewater facilities where UVTs <55% were observed and employed machine learning to analyze correlations between measured UVT and various water quality parameters including carbonaceous biological oxygen demand (CBOD) and total organic carbon (TOC). UVT prediction allows for historical data to be verified whether the sensor was reading correctly or for optimization of UV system operation. Materials and methods: This study collected UVT and additional water quality data from each respective treatment facility secondary effluent at various sample collections intervals over the last 5 years. UVT was collected with online and benchtop instruments while other water quality data were collected via analytical methods accepted by 40 CFR criteria. Data cleaning and analysis was performed in R using various open-source packages and algorithms. Results and discussion: Review of Industry Guidance. Although there is no EPA requirement of a minimum design UVT for wastewater disinfection, guidelines have been followed in various states. The 2012 NWRI Guidelines set minimum allowable UVTs for wastewater applications based on the type of upstream treatment with a 55% minimum for applications with media filtration (REF2). In addition, 10 States standards recommends UV disinfection in wastewater be limited to effluent UVTs greater than 65% (REF3). However, UV disinfection has been implemented in states across the US with UVTs of 55% or lower, where various benchtop and full-scale data supports viable inactivation of microbes relevant to each projects operating permit. This study considered two facilities which are known to produce lower UVTs than conventional nitrifying treatment, Pure Oxygen Activated Sludge and Trickling Filter, from projects in Michigan and California, respectively. Machine Learning Techniques. Machine learning consists of algorithms and statistical models to analyze and draw inferences from patterns in data and can be utilized for various applications relevant to water treatment. This study reviews industry accepted techniques for employing machine learning for numerical predictions models based on multivariate regression and provides an in-depth review of the two algorithms employed in this work, Random Forests (RF) and Support Vector Regression (SVR). Case Study 1. A pure oxygen activated sludge treatment facility in Michigan undergoing a disinfection system evaluation was analyzed to consider UV disinfection to replace previous disinfection systems using sodium hypochlorite and ozone. Black & Veatch implemented an online UVT probe for a period of 12 months where the plant experienced various low UVT trends (<50%) that were impacted by ferric chloride addition, expected industrial source discharges, and sensor drifting. RF and SVR machine learning algorithms were employed to predict UVT based on CBOD, Solids and Temperature. Model results were successful in predicting UVT with an R mean squared value (RMSE) of 0.84 and 0.83, respectively (Figures 2 and 3). To mitigate the impact of excessive drifting of the online UVT probe, the model was further refined to predict periods where the UVT probe may have drifted out of calibration. Outcomes of these predictions could help promote instrument calibration or ensure historical data is accurate and whether or not it should be included in further analysis for process design of a UV disinfection system. Case Study 2. A regional wastewater facility in California undergoing a plant upgrade to employ UV disinfection for Title 22 non-potable reuse was also evaluated. As a part of process design and commissioning of the new Title 22 UV disinfection system, Black & Veatch analyzed 2+ years of water quality data where UVTs less than 50% were observed, which has been documented for trickling filter secondary effluent (REF4). Upstream trickling filter backwashing events were thought to have especially produced organic loads which impacted the UVT sensor and may have altered data collection after the system upset had already passed. TOC and TSS data were used to train the RF and SVR models to predict UVT across the monitoring period, with the SVR achieving a higher success in prediction with an RSME of 0.86 (Figures 5 and 6). Conclusions: 1.Applications where UVT is <55% can be managed contrary to some guidance and provide effective disinfection. 2.Machine Learning can verify analyzer trends to identify correct/incorrect historical data and ensure appropriate process design. 3.Machine Learning can be integrated with control approaches to accelerate response of UV disinfection systems based on anticipated water quality. 4.Multivariate water quality constituent regression could be paired with UV validation equations to predict performance and improve understanding of disinfection operations.

UV disinfection systems rely on the real-time monitoring of UV Transmittance to appropriately inactivate microorganisms and protect public and environmental health. This study demonstrated the use of machine learning to predict UV Transmittance in applications where potential analyzer error or disadvantageous water quality impacts the ease of operations or system cost, further validating process design assumptions and improving UV system control and operations.

SpeakerPimentel, Anthony

Presentation time

10:30:00

11:00:00

Session time

10:30:00

12:00:00

SessionWhat's New in UV?

Session number518

Session locationRoom 238

TopicDisinfection and Public Health, Intelligent Water, Intermediate Level

Author(s)

Pimentel, Anthony, Hunter, Gary, Torkzadeh, Hamed

Author(s)A. Pimentel1, G.L. Hunter2, H. Torkzadeh3

Author affiliation(s)1Black & Veatch, CA, 2Black & Veatch, SC, 3Black & Veatch, GA

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2024

DOI10.2175/193864718825159549

Volume / Issue

Content sourceWEFTEC

Word count11

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

Author(s)P. Mcnamara1, A. Shaw1, E. Redmond1, G. Hunter1, U. Bazemo1

Author affiliation(s)Black & Veatch; Marquette University1, Black & Veatch1, Black & Veatch1, Black & Veatch1, , , ,

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2025

DOI10.2175/193864718825160156

Volume / Issue

Content sourceWEFTEC

Word count16

Resilience, Sustainability, and Risk of Intermittent UV LP And LED Systems

Abstract

UV LP and LED systems were compared in their engineering viability for an intermittent flow, 1 MGD average flow UV wastewater system at 65% UVT regarding resilience, sustainability, and risk. Resiliency to system cycling, sustainability via a life-cycle cost comparison, and risk of maintaining system performance guarantees were evaluated for LP, current LED, and future LED systems. Overall, this assessment demonstrated the feasibility and future optimization of these systems in wastewater disinfection. As UV LEDs continue to develop and enter the wastewater market, full-scale UV LED systems could help wastewater treatment systems reduce energy cost, labor requirements, and monetary risk. Advancement of UV LP and LED systems in treating intermittent flows with minimal energy requirements will help the wastewater industry meet climate change and sustainability initiatives.

UV LP and LED systems were compared in their engineering viability for an intermittent flow, 1 MGD UV wastewater system at 65% UVT regarding resilience, sustainability, and risk. Resiliency to system cycling, sustainability in a life-cycle cost comparison, and risk of maintaining system performance guarantees were evaluated for LP, current LED, and future LED systems. Overall, this assessment will demonstrate the feasibility and future optimization of these systems in wastewater disinfection.

SpeakerPimentel, Anthony

Presentation time

09:00:00

09:30:00

Session time

08:30:00

10:00:00

SessionUV Disinfection: Where are we? Where are we going?

Session locationRoom S404c - Level 4

TopicDisinfection and Public Health, Intermediate Level, Municipal Wastewater Treatment Design, Research and Innovation

Author(s)

Pimentel, Anthony

Author(s)A. Pimentel 1; G. Hunter 2 ; A. Pimentel 1; H. Mettlan 3; R. Osborne 4; J. Garrison 6; S DeBoses 6;

Author affiliation(s)Black & Veatch 1; Black & Veatch 2 ; Black & Veatch, Los Angeles, CA 1; Black & Veatch 3; Black & Veatch 4; Clemson Wastewater Treatment Facility 6; Clemson Wastewater Treatment Facility 6;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2023

DOI10.2175/193864718825159162

Volume / Issue

Content sourceWEFTEC

Word count12

UVC-LED the Wave of the Future

Abstract

INTRODUCTION
In the wastewater industry, energy and operation costs are major factors in selection of a disinfection technology. Ultraviolet Light Emitting Diode (UV-C LED) systems based on a solid-state technology, generally tends to operate with low electrical consumption and less relative space to conventional technology. A comparison of LED UV to UV systems applied to wastewater indicating that there was large (over 50 percent) cost savings for this technology when applied to wastewater systems. UVC LED Technology currently is on a rapid development scale. UVC LED units were produced 2 years ago have changed dramatically the output and decreasing the production costs. Testing of three different UV-C LED water disinfection pilot-scale units at the U.S. Environmental Protection Agency (EPA) Test and Evaluation Facility in Cincinnati, OH. The pilot-scale testing included collimated beam testing and flow-through testing for both drinking water and municipal wastewater. During the first two studies the test runs targeted MS-2 bacteriophage and other organisms. The focus of the third test was on Legionella inactivation.
BACKGROUND
In much the same way that visible light emitting diodes (LEDs) have revolutionized the general lighting industry, UV-C LEDs are now viewed as the 'next generation' in UV-C disinfection and are expected to rapidly replace conventional mercury arc lamps in water disinfection applications. LEDs are made from crystalline compound semiconductors that emit light when energized. UV-C LED system integrators purchase many single-packaged UV-C LEDs and combine them into a larger UV-C LED reactor which is then equipped with electronics, thermal management system, optics, and housing to create a finished UV-C LED system or module. Point-of-use (POU) UV-C LED systems for the treatment of potable water are already commercially available and market competitive, but larger-capacity UV-C LED systems for municipal water and wastewater disinfection are still under development.
RESULTS<b/>
The primary objectives of this project were to evaluate the disinfection performance, reliability, and energy use requirements of three small-scale UV-C LED water disinfection units (e.g., one at 10 gallons per minute (gpm) and two at 20 gpm rated sizes) for a variety of test conditions. Test conditions included treating water to achieve public supply drinking water, municipal treated secondary wastewater, combined sewer, and reuse water requirements. Both Collimated beam and flow through testing was conducted to validate the removal of MS-2 and Legionella. MS-2 Testing Results of MS-2 Testing can be divided into two group. Collimated beam testing was Collimated Beam Results MS-2 bacteriophage was added to the dechlorinated water to conduct this test. The Ultraviolet Transmittance (UVT) was 98.7% at 280 nm. Collimated beam tests were performed at 280 nm with results shown in Fig. 1. Reuslts of testing indicate a 0.5 log removal of MS-2 per 5 mJ/cm2 increase in dose. These results match with data presented and used for development of NWRI response curves. Extrapolating the data, a 5 long inactivation would indicate that a 5 log removal of MS-2 could be achieved at a dose of 50 mJ/cm2 if the removal remained linear. Typically the inactivation curve is more geometric, therefore the predicted dose would probably be more closely to 100 mJ/cm2. Flow-Through Results Due to the piping configuration at the EPA T&E Facility, the flow rate to the unit was limited to 22.7 liters per minute (6 gpm). Flow-through testing was only conducted with MS-2 bacteriophage.. The test water was inoculated with MS-2. The MS-2 was fed at a rate of 93 mL/min. The water flowed through the unit for 3 minutes and then inlet and outlet samples were collected at 8-minute intervals. The results for both pilot unit 1 and 2 are shown in Figure 2. At 22.7 liters per minute (6 gpm), the pilot unit 1 could provide a 3-log removal at a dose of 85 mJ/cm2. Pilot unit 2 achieved a 4-log removal at 85 mJ/cm2 and with a flow rate of 15.14 liters per minute (4 gpm). Based on these flow rates, the power input would be in the range of 200-250 kilowatt-hours per million gallons (kWh/MG).
LEGIONELLA TESTING
Legionella Testing was conducted by USEPA to validate the dose response that could be achieved four different SerioGroups at three wave lengths. UVC-LED disinfection efficacy were evaluated for four Lp strains representing three clinically significant serogroups (sg1, 4, and 6) in drinking water utilizing both a collimated beam (at 255, 265, and 280 nm) and a point-of-entry (POE) treatment set-up (280nm). Understanding the inactivation differences between Lp serogroups in drinking water, especially for UVC-LED POE applications, will help determine the most effective remediation strategies needed to target specific isolates during contamination events. The focus of the testing was to examine the inactivation of legionella at 280 nm a that was the wavelength of the unit shown in Figure 3. However, for the POE tests, only sg6 displayed the highest reduction (mean Â± standard deviation) of 5.0 Â± 0.5 log10 CFU/mL compared to 3.5 Â± 0.5, 3.3 Â± 0.2, and 3.6 Â± 0.1 log10 CFU/mL for sg1, sg1 DW, and sg4, respectively.
DISCUSSION<b/>
Using the flow-through pilot test results, the project team developed scale-up factors to project energy use values for UV-C LED water disinfection. Because of the flowrate limitations, the energy use projections for the UV-C LED system are preliminary, and we provide the energy use values in relatively wide ranges. We project the energy use for UV-C LED disinfection of drinking water is in the 65-250 kWh/MG range. The projection is for a UV-C LED system treating drinking water with 90% transmittance at a UV dose of 40 mJ/cm2. The energy use projections for UV-C LED disinfection systems are comparable to conventional UV mercury vapor lamp systems. The energy use requirements for disinfecting drinking water are approximately 60-120 kWh/MG for medium-pressure mercury vapor lamp systems and 50-200 kWh/MG for low-pressure mercury-vapor lamp systems.
CONCLUSION
A summary will be provided of the advances of LED UV, focusing on its ability to reduce microbial transfer across several applications. There are often limits in place that prevent fully utilizing newer technology. When capital and operating costs come down, availability of products, new possibilities open up to apply technology. UV LED technology can be seen to following the same path. Test results collected by USEPA on the use of UVC-LED on MS-2 as well as Legionella have been shown to be able to achieve similar results to that in low pressure UV applications. System can be applied to point of use applications cost effectively and improvements in design will allow for deployment in larger flow systems.

UV-C LED Technology currently is on a rapid development scale. UV-C LED units were produced 2 years ago have changed dramatically the output of the systems. With the rapid changes that are occurring, the question exists: Where LED UV will be in 2 years (short- term as well as in 10 and 20 years)? Test results are presented from a number of bench scale (collimated beam) and demonstration scale tests. While a variety of test organism were examined, only test results on MS

SpeakerHunter, Gary

Presentation time

09:30:00

09:55:00

Session time

08:30:00

10:00:00

TopicFundamental Level, Disinfection and Public Health

Author(s)

Hunter, Gary

Author(s)Gary Hunter1; Bill Decker2; Oliver Lawal3

Author affiliation(s)Black & Veatch Corporation, Greenville, SC1; Aqua-Aerobic, Systems, Inc., Loves Park, IL2; AquiSense Technologies, Erlanger, KY3