Sears, Keith

Keith Sears is AECOM’s North America Practice Leader for Nutrient Removal. He has a Ph.D. in Environmental Engineering from Purdue University,...

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About Sears, Keith

Keith Sears is AECOM’s North America Practice Leader for Nutrient Removal. He has a Ph.D. in Environmental Engineering from Purdue University, and has over 25 years of experience specializing in the area of advanced wastewater treatment. . He is currently an adjunct professor at the University of Manitoba, and is a past winner of the Robert Canham Award from the Water Environment Federation for his work on nutrient removal.

Sears, Keith

Titles from this speaker

Developing a Digital Protocol to Optimize Biological Nutrient Removal Performance

Abstract

Introduction
Recent advancements in sensor technology, automation, and the decreasing costs of digital technologies have significantly accelerated the development of digital solutions in wastewater treatment. When implemented effectively, these solutions prioritize insightful analysis over sheer data volume, concentrating on the importance of measuring data at the most strategic locations. This paper presents a distinctive combination of operational expertise and theoretical foundation behind a novel digital optimization control strategy for Biological Nutrient Removal (BNR). This strategy is informed by over 35 years of operational experience at full-scale BNR facilities, with specific proof-of-concept trials carried out at the Westside Regional BNR facility.

In 2019, WERF published the report 'Optimization and Design of a Side-Stream EBPR (S2EPR) Process.' A survey of six full-scale facilities found the Westside Regional BNR Facility achieved the lowest and most stable secondary effluent orthophosphorus concentrations among all plants studied.

Building on the findings of the WERF study and their evaluation of the Westside Regional WRF facility, an assessment of the facility's operational parameters was carried out to pinpoint the control strategies responsible for its exceptional performance. A standard operating procedure (SOP) was created and stress tested to evaluate how specific setpoints influenced overall effluent quality and interplay between key parameters. The developed SOP can be incorporated into a digital optimization strategy available for those utilities looking to improve BNR performance.

Approach
Over the course of a year, an optimized BNR control philosophy was developed by examining the interactions among several key operating parameters. The resulting control strategy achieved stable effluent PO4 concentrations below 0.1 mg/L without chemical use by establishing interdependent controls for the following:
1. Automated ammonia based SRT control
2. Automated ammonia based aeration control (ABAC)
3. RAS control for sludge blanket and underflow PO4/NO3 refinement
4. Automated carbon diversion for nutrient and energy optimization
5. Automated control of anaerobic zone HRT based on PO4 release

Discussion
Most treatment facilities in the Okanogan region must meet an effluent total nitrogen < 6 mg/L and total phosphorus < 0.25 mg/L. As a result, maintaining low effluent ammonia is an indirect requirement to achieving the total nitrogen limit. Therefore, the purpose of the automated ammonia SRT controller was to provide sufficient removal of ammonia, without an excessive aerobic SRT which in-turn leads to foaming, endogenous release of ammonia, and other unfavorable conditions. The automated ammonia SRT controller was set-up and based on real time effluent ammonia results. Setpoints were such that if the daily average ammonia concentration increased above 1 mg/L, the controller would increase SRT by 1.0% each day. If the daily average ammonia concentration dropped below 0.5 mg/L, the SRT controller would decrease SRT by 1.0% each day. The gradual increase and decrease of SRT, controlled by effluent ammonia, led to a high-rate process, which in turn facilitated an efficient subsequent step for phosphorus removal.

In BNR facilities, controlling the secondary clarifier sludge blanket level is crucial to prevent the contamination of RAS nitrates from returning to the anaerobic zone. Clarifier sludge blankets are capable of reducing nitrates by more than 5 mg/L depending on operation. However, too much NO3 removal can result in excessive PO4 release in the blanket and an overall decline in effluent quality. Full scale trials that will be presented in the full paper indicated that balancing NO3 reduction with PO4 release in the sludge blanket is an important control parameter. These full scale trials indicated that the optimum PO4 release in the blanket was in the 1-2 mg/L range. An indicative scan is shown in Figure 1. The concentration of NO3/PO4 in the sludge blanket was used as a control strategy for the RAS rate. When RAS PO4 release was greater than 2 mg/L the RAS rate was increased, and when less than 1 mg/L the rate decreased.

A control algorithm was developed to ensure consistent PO4 release in the anaerobic zone. Operational experience revealed that when PO4 release in the anaerobic zone exceeded 25 mg/L, it became challenging to effectively uptake such a high concentration of PO4 in the downstream aeration zones. Excessive release was an indication that carbon/VFA's would be more beneficially used for denitrification, and triggered diversion of high VFA fermentate to the downstream anoxic zone. The result was an optimized use of carbon for both phosphorus removal and total nitrogen removal.

Effluent ammonia was integrated into ammonia-based aeration control to complement the automated SRT controller. When effluent ammonia fell below 0.7 mg/L, the final cell's aeration D.O. setpoint was reduced to 0.5 mg/L. If ammonia rose to 0.8 mg/L, the D.O. setpoint increased to 1.0 mg/L.

Finally, controlling anaerobic zone HRT was critical, as excessive HRT not only released PO4 but also ammonia. This ammonia release ultimately necessitates oxidation to nitrate and subsequent denitrification, lowering plant efficiency. Further details will be provided in the full paper due to space constraints.

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

Presentation time

16:30:00

16:40:00

Session time

15:30:00

17:00:00

SessionInnovative Approaches to Design and Optimization

Session locationMcCormick Place, Chicago, Illinois, USA

TopicLiquid Stream Treatment - Nutrient Removal and Recovery

Author(s)

Sears, Keith, Stevens, Gerry, He, Xiaohong

Author(s)K. Sears1, G. Stevens1, X. He1

Author affiliation(s)AECOM1

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Sep 2025

DOI10.2175/193864718825159972

Volume / Issue

Content sourceWEFTEC

Word count11

Extending the Life of Wastewater Membranes Significantly Reduces Life Cycle Costs

Abstract

Abstract
Despite the significant reduction in membrane manufacturing costs, there is a perception within the engineering community that membrane treatment (i.e., MBRs) is more costly than conventional activated sludge systems. Membrane replacement costs have a significant impact on the overall net present value (NPV) of a facility. Membranes installed over the last decade can offer valuable information in estimating membrane life expectancy. Since replacement costs are very expensive, owners are paying more attention to operational adjustments that can extend membrane life. The City of Brandon is one such facility that installed their original membranes over 13 years ago and have observed minimal decline in performance. There is growing evidence that membrane life is determine by operational aspects more than any other factor. Since the City was new to operating an MBR facility in 2009, they began operation of the facility with strict adherence to the manufacturers protocol, and over time have made adjustments which they believe have had favorable impacts on membrane life. This presentation will highlight some of the key considerations made to the operation of the facility.
Background
In October 2009 the City of Brandon began operation of a three train MBR system. In December 2013, the City completed an expansion of the MBR facility, which included the addition of six more membrane trains. At the time the original membrane cassettes were installed in 2009 it was thought that the membrane life would be between 5-7 years. At the end of the 7th year, the membranes were performing very well, and the City decided to continue without replacement. By the end of the 11th year, there was still no decline in performance or increased chemical cleaning requirements. However, due to the uncertainty of how long the membranes would last, the City decided to replace a portion of the 2009 cassettes with new cassettes in December 2020. To get a better idea of how long the membranes will last, the City decided to leave one train (Train 4) populated with original 2009 cassettes. This unique configuration allows the City to operate the facility with differing aged membranes, and use this information to define the replacement strategy for the remaining membranes (see Figure 1).
Objectives
The objective of this paper is to provide a review of the performance of the various aged membranes at the Brandon WRF. The operational adjustments made since start-up will be discussed with a focus on how these adjustments have extended membrane life. Based on the current life expectancy of the membranes the NPV will be compared against the original NPV, providing a better assessment of the cost savings associated with extending the life of the membranes. The NPV information will be provided in the full paper. Membrane Trans-membrane Pressure and Maintenance Cleans Fenu et al (2012) evaluated the concept membrane life and noted that there is little information that defines life expectancy of membranes. Cote et al (2011) suggested that a slow increase in operating pressure and the need for more frequent chemical cleans should be the trigger for replacement. Building on this recommendation, the rate of pressure increase over time between maintenance cleans was evaluated and summarized in Table 1 and Figure 2. The information in Table 1 summarizes the increased pressures following a maintenance clean, done typically around every 60 days. Normal variations in pressure were observed due to varying influent flows, wastewater temperatures, and MLSS filterability. Since all membrane trains were fed the same MLSS and flow, a relative comparison between the pressure in the trains can be made. As expected, the new membranes had lower rate of pressure increase between cleans. However, the 2009 and the 2013 membranes (winter) were identical. During summer months the rate of pressure increase was lower for all trains due to a number of factors (i.e., lower viscosity, lower SRT, etc.).
The information in Table 1 indicates even for the oldest 2009 membranes, the pressure increase is very low allowing the membranes to operate without a maintenance clean for more than 2 months (as compared to the 3 per week originally anticipated). The data indicates that with the 60+ day period between cleans the pressure drop in all trains is restored, indicating an effective removal of foulants. The total number of maintenance cleans conducted over the year were similar for all trains (Table 2). In fact, in 2021 the oldest membrane train (Train 4) received the lowest number of cleans.
Filtered effluent turbidity from each train was similar ranging from 0.05 NTU to 0.08 NTU. In addition to the operating data from the plant, microscopic evaluations of the various aged membranes are currently underway. A preliminary scanning electron microscope image of the 2009 membrane is shown in Figure 3. Details of the microscopy analysis will be provided in the full paper.
Factors Impacting Performance of Brandon's MBRs
The City of Brandon has operated their membrane treatment system for over 13 years, and have made adjustments which they believe extended the membrane life. Operational adjustments discussed in the full paper will include the following: - Proper screening and pre-treatment requirements - Getting the biology right, allowing for colloid adsorption and organic compound degradation. - Reduced maintenance and recovery cleans based on need rather than fixed schedule
Summary
Operational aspects have a significant impact on membrane life, likely more than any other factor. This paper will highlight key adjustments made to the operation of the Brandon MBR facility which have extended their membrane life. Data will be provided on membrane fouling rates, cleaning frequencies, effluent quality, and microscopy analysis. Operational lessons learned will provide other utilities useful information when considering membrane technology, and those assessing the need for membrane replacement. Finally, the NPV of the facility based on the current membrane life will be compared against the original NPV providing an assessment of the cost savings.

SpeakerSears, Keith

Presentation time

15:30:00

15:55:00

Session time

15:30:00

17:00:00

TopicIntermediate Level, Energy Production, Conservation, and Management, Facility Operations and Maintenance, Municipal Wastewater Treatment Design

Author(s)

Sears, Keith

Author(s)Keith Sears1; Alexia Stangherlin2; Wes Knight3; Victor Wei4

Author affiliation(s)AECOM, Winnipeg, Canada1; City of Brandon, Brandon, Canada2; City of Brandon, Brandon, Canada3; University of Manitoba, Canada4

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2022

DOI10.2175/193864718825158684

Volume / Issue

Content sourceWEFTEC

Word count12

Optimizing Performance of a Side-Stream Enhanced Phosphorus Removal System

Abstract

In 2019, WERF Published the report "Optimization and Design of a Side-Stream EBPR (S2EPR) Process as a Sustainable Approach for Achieving Stable and Efficient Phosphorus Removal U1RI3/4869". The WERF study goals included the identification of the fundamental mechanisms involved in a RAS fermentation process (S2EBPR) and to develop criteria for effective design and operation of the process. To achieve the objectives, the research team conducted a survey of data from six full-scale facilities, simulated side-stream reactor batch testing, and performed full-scale pilot testing with side-by-side S2EBPR and conventional EBPR processes. The WERF report noted that the Westbank Process configuration was very stable and produced the lowest secondary effluent orthophosphorus concentrations of all plants studied. It was also noted that unique to the Westbank Regional Facility that more than 75% of the time phosphorus uptake was measured in the anoxic zones (Onnish-Hayden et al, 2018). Fluorescent In-situ Hybridization (FISH) and amplicon sequencing found relatively high abundance of Tetrasphaera in the S2EPR configurations. The highest relative abundance of the all the plants studied was found in the Westbank Regional Facility. The WERF researchers postulated that this could be attributed to the addition of primary sludge fermentate to the anaerobic side stream reactor and to the mainstream anoxic zone. It was thought that the fermentate could contain Tetrasphaera that could act as a seed to the mainstream providing a competitive niche to those organisms.

In 2019, the Water Research Foundation (WRF) published the report “Optimization and Design of a Side-Stream EBPR (S2EPR) Process as a Sustainable Approach for Achieving Stable and Efficient Phosphorus Removal U1RI3/4869.” The WRF report noted that the Westbank process configuration was very stable, had high concentrations of Tetrasphaera Bio-P bacteria, and produced the lowest secondary effluent orthophosphorus concentrations of all plants studied. This paper presents an analysis of approximately one year of plant operational fine tuning of the Westbank S2EPR process and presents key information used to develop a revised standard operating procedure for improving overall plant performance

SpeakerSears, Keith

Presentation time

14:30:00

14:45:00

Session time

13:30:00

15:00:00

SessionBringing It All Together: Guide to Designing and Implementing S2EBPR Processes

Session number502

TopicFacility Operations and Maintenance, Municipal Wastewater Treatment Design, Nutrients

Author(s)

Keith Sears

Author(s)K. Sears1; G. Stevens1; B. Stinson1; P. Galvagno1; A. Lambrecht1; B. Mazda1;

Author affiliation(s)AECOM, Winnipeg, MB1AECOM, Kelowna, BC2,4AECOM, Annapolis Junction, MD3Regional District of Central Okanagan, Kelowna, BC5,6

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2021

DOI10.2175/193864718825158140

Volume / Issue

Content sourceWEFTEC

Word count10

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Sears, Keith

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