Falk, Michael

Mike is serves as HDR's West Region Wastewater Market Sector Lead where he has worked the last 16 years. He specializes in process engineering and watershed-based approaches for managing nutrients. This presentation is a culmination of the last 10 plus years on a regional nutrient management collaboration across the Bay Area.

Titles from this speaker

A Watershed Based Approach for Managing Nutrients in San Francisco Bay

Abstract

The proceedings will present nutrient load reduction and cost findings from Nutrient Watershed Permit 1.0 and draft preliminary findings from Nutrient Watershed Permit 2.0.

SpeakerFalk, Michael

Presentation time

14:00:00

14:10:00

Session time

13:30:00

15:00:00

SessionCome Together, Right Now, Over Watersheds...

Session number111

TopicAsset Management, Nutrients, Policy and Regulation, Watershed Management, Water Quality, and Groundwater

Author(s)

Michael Falk

Author(s)M. Falk1; J.B. Neethling1; I. Wren2; L. Fono3; T. Mumley4; H. Kennedy1;

Author affiliation(s)HDR, Folsom, CA1Consultant, San Francisco, CA 2Bay Area Clean Water Agencies, Oakland, CA3San Francisco Regional Water Quality Control Board, Oakland, CA 4

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2021

DOI10.2175/193864718825157984

Volume / Issue

Content sourceWEFTEC

Word count12

Hybrid MABR Technology for Nitrogen Removal in a Low Suspended Growth SRT

Abstract

This paper focuses on the hybrid MABR technology for nitrogen removal at a WRRF operating in a low suspended growth SRT (i.e., cBOD mode). To date, full-scale MABR installations have been limited to WRRFs already performing nitrogen removal, whereby the MABR is working in a complementary fashion to the existing suspended growth activated sludge.

The novel application of using MABR in a low suspended growth SRT was piloted at Central Contra Costa Sanitary District (Central San) in the San Francisco Bay Area. Under this application, the hybrid MABR biofilm exclusively performed the ammonia/total nitrogen removal (i.e., non-complementary with the low suspended growth sludge). The focus of this presentation can be broken into three areas:
1) Background, objectives, and results
2) Sumo® modeling results
3) Carbon, energy, and greenhouse gas (GHG) emissions potential benefits for this hybrid MABR in a low suspended growth SRT mode

Background, Objectives, and Results
Central San is one of the five largest wastewater treatment plans in the San Francisco Bay Area with a permitted capacity of 53.8 mgd average dry weather flow. The Bay Area recently adopted total inorganic nitrogen (TIN) load limits (40 percent baywide aggregate TIN load reduction). Transitioning from secondary treatment to nitrogen removal at Central San is challenging due to plant capacity, site contaminated soil, and a return stream from incinerator air pollution control equipment containing cyanide (a known inhibitor of nitrifiers). MABR was selected for piloting as it has the potential to remove TIN within existing tankage while addressing the other listed challenges.

At the pilot onset, Central San had not yet received permit limits. The overarching piloting goal was to evaluate whether existing tankage could be retrofit with this intensification technology in a relatively fast construction project (~1 year) with minimal modifications to the secondary process.

Central San's pilot included four core objectives:
1. Confirm ability to form an ammonia removing biofilm on the membranes (addresses cyanide concerns)
2. Evaluate ammonia and TIN removal while maintaining low suspended growth SRT
3. Determine specific ammonia removal rates to confirm ability to remove ammonia/nitrogen in existing tankage
4. Determine the optimal MABR cassette's location at Central San

MABR Pilot Setup and Results
The pilot process flow diagram is presented in Figure 1. The pilot can be fed from different locations across the plant (see Figure 2). Details for each phase are provided in Table 1.

A summary for each phase (approximately 2-months each) and the corresponding results:
- Phase I (secondary clarifier influent feed): to demonstrate the hybrid MABR ammonia removal efficacy while maintaining a relatively low suspended growth SRT. The ammonia removal performance in Phase I is presented in Figure 3. Some key observations:
- Ammonia Removal occurred rapidly within initial 2 weeks with an effluent steady state of 5-10 mg N/L.
- Ammonia removal rate (approximately 2.1 g/m2/d) was similar to other full-scale installations with a longer SRT (typically 2-2.5 g/m2/d).
- TIN removal was minimal as expected due to limited available carbon at this feed location.
- Phase II (anaerobic selector feed): to verify that the hybrid MABR biofilm can effectively remove nitrogen in the presence of ambient cyanide. The ammonia and TIN removal performance are presented in Figure 4 and Figure 5, respectively. Some key observations:
- Ammonia Removal was similar to Phase I, showing robust and reliable removal.
- Up to 40% TIN removal was observed. TIN removal improved from Phase I, but it was still limited due to carbon availability.
- Phase III (blend of anaerobic selector and primary effluent): to stress the system with the highest possible cyanide, ammonia, and carbon levels. The ammonia loading and TIN removal performance were initially similar to Phase II as presented in Figure 6. Some key observations:
- Ammonia Removal was similar to Phases I and II, showing robust and reliable removal.
- Up to 50% TIN removal was observed.
- Upon increasing the loading rates, the nitrifying biomass appears to be the limiting factor as evidenced by an increase in effluent ammonia levels.

Full-Scale Hybrid MABR Modeling Results for this Low Suspended Growth SRT Mode
Sumo® was used as the modeling platform as its features lends itself to such attached growth systems. The datasets used were as follows: daily pilot grab samples, influent and effluent ammonia and nitrate online probes, daily composites from the raw influent and primary effluent samplers during the phases II and III, and diurnal sampling from July/August 2019.

A comparison of the data against the calibrated model is presented in Figure 7. Overall, the model was deemed reasonably calibrated to compare various MABR layouts and relative TIN removal performance.

The energy efficiency benefits of MABR are well documented with an emphasis on oxygen transfer efficiency (e.g., Castrillo et al., 2019) and simultaneous nitrogen removal. While attractive, how does a hybrid MABR operating in a low versus high suspended growth SRT compare in terms of cost, carbon, energy, and GHG emissions? For comparative purposes, a Modified Ludzack-Ettinger (MLE) configuration was used as a baseline while comparing the low versus high suspended growth SRT as shown in Table 2.

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

SessionLow SRT Performance of Membrane Aerated Biofilm Reactors (MABR)

Session locationMcCormick Place, Chicago, Illinois, USA

TopicLiquid Stream Treatment - Nutrient Removal and Recovery

Author(s)

Cunningham, Michael, Goel, Nitin, Falk, Michael, Zhang, Yihan, Pitt, Paul, Latimer, Ron, Daigger, Glen

Author(s)M. Cunningham1, N. Goel1, M. Falk2, Y. Zhang2, P. Pitt4, R. Latimer4, G. Daigger5

Author affiliation(s)Central Contra Costa Sanitary District1, HDR, Inc.2, Oakland County WRC3, Hazen and Sawyer4, University of Michigan5

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Sep 2025

DOI10.2175/193864718825159971

Volume / Issue

Content sourceWEFTEC

Word count13

Innovative Baffle System Tripling Primary Sedimentation Capacity and Saving Millions

Abstract

Learning Objective - To provide insight and share the experience of using an innovative baffle system in the primary sedimentation process at Dublin San Ramon Services District (DSRSD) to enhance the total suspended solids (TSS) and biochemical oxygen demand (BOD) removal efficiencies and increase capacity. Results of the stress testing indicated that PSTs equipped with baffle system achieved a total suspended solids removal of 46 percent at overflow rate of 8000 gpd/ft2 which is more than the triple the original capacity of the PSTs. Background The DSRSD operates a 17 MGD wastewater treatment plant in Dublin, California. The wastewater treatment plant had four primary sedimentation tanks (PSTs). Additional BOD5 removal in the primaries reduces loading to the secondary process thus reducing aeration demand as well as capital costs of new infrastructure for potential future nutrient removal requirements. Therefore, DSRSD initiated a project to increase the capacity and improve performance of the primary process. Feld testing and preliminary modeling was conducted to identify potential structural improvements. The study indicated that by optimizing the existing four tanks (with internal baffles) and adding one new tank, DSRSD would be able to achieve the goal. Objectives The objectives are threefold: 1.To introduce an innovative baffle system to increase the capacity and improve suspended solids and biochemical oxygen demand capture in conventional primary treatment. Such baffle systems could be applied at many conventional primary treatment plants leading to significant savings in downstream secondary treatment capital and operational costs. 2.To present the baffle systems as a potential replacement of chemically enhanced primary treatment as means of increasing solids capture. 3.To present DSRSD experience and lessons learned during the design, testing and construction of the baffle system. Status In 2017, DSRSD initiated an optimization study as part of the design project to investigate the potential of optimizing the existing PSTs. The study indicated that optimizing existing tanks and adding one more tank will achieve DSRSD goal. Since finishing the bulk of construction (2021), the primaries have exceeded the anticipated primary solids capture (upwards of 70 percent) under normal flow conditions. Stress testing indicated that the PSTs equipped with the baffle system was capable of achieving TSS removal efficiency of 46 percent at overflow rates as high as 8000 gpd/ft2. This overflow rate is almost triple the original flow rate that could have been sustained in the past (before installing the baffle system) by the PSTs while maintaining reasonable performance. A co-benefit of increasing the solids capture across the primaries is an increase in biogas production. Biogas production has increased approximately 20 percent. This increase is attributed to a combination of higher solids/organics capture across the primaries and primary solids having higher BTU content than waste activated sludge. Methodology Using CFD, an influent flocculation baffle, two mid-tank baffles , and a sludge protector canopy were modeled. Modeling results predicted that the preferred design would increase TSS and BOD5 removal efficiencies by increasing flocculation, improving the flow regime inside the tanks, decreasing short-circuiting, and decreasing sludge re-suspension. Field Testing and Data Analysis: Table 1 shows the sequence of the testing activities. PST#4 is one of the old tanks with deeper side water depth than PSts # 1, 2 and 3. As part of this project, internal baffles and transversal launders were installed into tank #4. PST # 5 is a completely new tank. For the stress testing, the old PSTs were taken offline to increase the loadings on the new PSTs. Effluent suspended solids and sludge density samples were collected as part of the stress testing. Figure 1 shows the results of the stress testing with both PSTs # 4 and 5 online. Table 2 summarizes the results of the testing. It is clear from the data that PSTs were able to achieve TSS removal efficiency as high as 59 percent at over flow rate of approximately 4100 gpd/ft2. On the second day of stress testing, PST# 4 was taken offline and the whole plant flow of approximately 15.75 mgd (average) was diverted to PSTs #5, during the testing, the effluent launders of PSTs # 5 were flooded indicating exceeding the hydraulic capacity of the tank. However, TSS removal efficiency was still satisfactory exceeding 46 percent. Conclusions 1.The new baffle system improved PSTs performance by increasing the TSS removal rate from 38 to 65 percent. 2.The new baffle system increased the process capacity of the PSTs and enables the PSTs of achieving TSS removal efficiency of 46 percent at over flow rate higher than 8000 gdp/ft2. 3.The new baffle system increased the TSS captured in the PST leading to increase ion biogas production. Significance: The baffle systems described herein improved TSS capture and allowed the PSTs to operate at much higher overflow rate than typically applied at conventional primary treatment. Such baffle systems could be applied at many primary treatment in many plants leading to significant savings in downstream secondary treatment capital and operational costs. Also, the baffle systems could be used in lieu of chemically enhanced primary treatment as means of increasing solid capture

An innovative baffle system has been utilized in the primary sedimentation process at Dublin San Ramon Services District (DSRSD) to enhance total suspended solids (TSS) and biochemical oxygen demand (BOD) removal efficiencies and increase capacity. Stress testing indicated that PSTs equipped with new baffle system achieved TSS removal of 46 percent at overflow rate of 8000 gpd/ft2 which is more than the triple the original capacity. Such a baffle system could be potential replacement of CEPT.

SpeakerGerges, Hany

Presentation time

11:00:00

11:30:00

Session time

10:30:00

12:00:00

SessionThree Different Flavors of Improvement for Preliminary/Primary Treatment

Session number522

Session locationRoom 349

TopicFacility Operations and Maintenance, Intermediate Level, Municipal Wastewater Treatment Design

Author(s)

Gerges, Hany, Yee, Jackie, Delight, Steve, Schilling, Bill, Falk, Michael, Greenfield, David

Author(s)H. Gerges1, J. Yee2, S. Delight2, B. Schilling3, M.W. Falk4, D. Greenfield5

Author affiliation(s)1HDR, CA, 2, CA, 3West Yost, CA, 4HDR Inc, CA, 5HDR, SC

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2024

DOI10.2175/193864718825159546

Volume / Issue

Content sourceWEFTEC

Word count11

Optimization Strategies: Optimization Approach - Decision Tree

Abstract

The Water Research Foundation (WRF) Guidelines for Optimizing Nutrient Removal Plant Performance (Project WRF 4973) began in early 2020 with a focus on developing guidance for the wide range of nutrient control techniques. Through this project, a decision tree will be developed based on an exhaustive peer review exercise to assist WRRFs in identifying such opportunities for enhancing their nutrient removal capabilities and optimize process performance. This presentation will cover the on-going efforts and solicit audience feedback for identifying opportunities to bolster the project outcomes (scheduled for 2022).

SpeakerFalk, Michael

Presentation time

10:00:00

10:20:00

Session time

08:30:00

12:00:00

SessionStrategies to Optimize WRRFs for Nutrient Removal

Session number510

TopicNutrients, Research and Innovation

Author(s)

M. FalkM. Falk

Author(s)M. Falk1; M. Falk1;

Author affiliation(s)HDR Inc, CA1

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2020

DOI10.2175/193864718825157508

Volume / Issue

Content sourceWEFTEC

Word count8

Watershed-based Nutrient Management: Bay Area Update on Treatment and By Other Means Strategies

Abstract

Problem Recent algal blooms in the Bay (2022 and 2023) have accelerated the need to develop nutrient management strategies across San Francisco Bay (Bay; emphasis on total inorganic nitrogen). This session will discuss the watershed-based collaborative approach that began over a decade ago and how the efforts are informing nutrient management decision-making. Goals and Objectives The session will begin with an update on the regional nutrient watershed permit (third permit), followed by an overview of findings from Regional Watershed Permits (WSPs) 1.0 (R2-2014-0014; HDR, 2018) and 2.0 (R2-2019-0017; HDR, 2023), and the corresponding menu of nutrient management options to inform decision-making. Furthermore, the session will address the importance of regional collaboration in advancing the nutrient management strategies. Introduction The Bay Area Clean Water Agencies (BACWA), working on behalf of the 37 municipal WRRFs discharging to the Bay, has been leading studies for more than 10 years to advance a watershed-based nutrient management strategy. The vision has been to use science to evaluate the health of the Bay ecosystem coupled with strategies for nutrient management at WRRFs (both inside and outside the treatment plant fenceline). Recent algal blooms in August 2022 and 2023 have accelerated the need to develop such a strategy as nutrient limits are looming in 2024 (anticipated adoption by year 2034). Specifically, the focus has been on managing total inorganic nitrogen (TIN). Approach The vision since the initial WSP in 2014 has been to develop a regional nutrient management strategy based on baywide load caps. As such, two separate Regional Watershed Permits (WSPs) were developed that focused on solutions at the treatment plant (WSP 1.0 in 2014) and by other means that focused on recycled water and nature-based solutions (WSP 2.0 in 2019). The results from each WSP menu of nutrient management options are in the process of being used to inform baywide decision making. The menu includes economics for improvements at each WRRF (optimization, sidestream, and upgrades), water recycling, and nature-based solutions. To date, the analyses has been limited to economics. By the end of the 1st quarter 2024, BACWA is including non-economic parameters as a means to effectively compare and contrast both solutions at the WRRFs and beyond (reuse and nature-based solutions (NbS)). Results and Discussion The results from WSP 1.0 are presented in Table 1. Optimization and sidestream concepts collectively are approximately $1B across the bay and it would translate to a combined total of 26 percent TIN reduction. The costs increase exponentially to greater than $10B with either conventional nutrient removal (15 mg N/L) or enhanced nutrient removal (6 mg N/L). Given the relatively high costs associated with WSP 1.0 which would be burdened by ratepayers, BACWA and its members moved forward with WSP 2.0 that considered recycled water and NbS. The overall recycled water findings are presented in Figure 1. BACWA members currently recycle approximately 14 percent of their dry season volumes to recycled water (data not shown). Figure 1 presents that the potential increase in volumes associated with reuse over time. There is the potential to triple reuse volumes over the next 25 years. This increase is predicated on numerous projects advancing beyond master planning, conceptual, and brokering of agreements. As such, confidence levels were applied to each project as illustrated in Figure 1 legend (referred to as confidence levels 1 through 4). The majority of the recycled water projects would divert nutrient loads away from the Bay. However, a significant portion of the TIN loads associated with planned potable reuse projects would end up in the Bay (listed as confidence level 3 and 4 projects). The analysis considers such challenges, as evidenced in a decline in the extent of TIN load reduction after year 2035. The TIN load reductions associated with reuse have the potential to double over the next 25 years compared to a tripling while evaluating water volume. The costs associated with all the listed reuse projects in Figure 1 is approximately $6B. While less expensive than the upgrades at each WRRF (refer to Table 1), this is relatively expensive for nutrient management. However, the other benefits associated with recycled water projects need to be considered while comparing against strategies at each WRRF. The NbS findings are not included in this proposal as it was limited to three WRRFs and it had marginal TIN load reduction. The session will conclude with a comparison (both economic and non-economic) of the nutrient reduction potential for all six nutrient management strategies: i) optimization, ii) sidestream, iii) upgrades (15 mg N/L), iv) upgrades (6 mg N/L), v) reuse projects, and vi) NbS. As previously noted, the non-economic analyses are in process and due the first quarter of 2024 (permit scheduled for April 2024). As such, the economic and non-economic evaluation will be included with the conference proceedings and session. Conclusion and Next Steps This watershed-based approach that considers science along with development of a menu of nutrient management options has the potential to serve as a template for other watersheds managing nutrients (regardless of the nutrient type).

Algal blooms across San Francisco Bay in 2022/2023 have accelerated the need to develop baywide nitrogen management strategies. This session will discuss the watershed-based collaborative approach that began over a decade ago. Results from the initial two Regional Watershed Permits (WSPs) will be presented, followed by an update on the recently adopted third WSP. The overarching goal of the collaboration is development of a menu of management options to foster local and regional decision-making.

SpeakerFalk, Michael

Presentation time

16:30:00

16:50:00

Session time

15:30:00

17:00:00

SessionNutrient Management: GET OUT (The Nutrients)!

Session number234

Session locationRoom 343

TopicIntermediate Level, Nutrients, Watershed Management, Water Quality, and Groundwater

Author(s)