Deco, Rachel

Rachel Deco is an Engineering Associate at Los Angeles County Sanitation Districts. She has a Bachelor of Science in Geochemistry from the California...

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About Deco, Rachel

Rachel Deco is an Engineering Associate at Los Angeles County Sanitation Districts. She has a Bachelor of Science in Geochemistry from the California Institute of Technology and a Master of Science in Civil Engineering from Loyola Marymount University. She has worked in the Wastewater Research Section for the past 10 years.

Deco, Rachel

Titles from this speaker

0.6 MGD Validation of a Unique Tertiary MBR Process to Provide NdN for Pure Water

Abstract

INTRODUCTION
The Los Angeles County Sanitation Districts (LACSD) and the Metropolitan Water District of Southern California (MWD) are jointly developing the Pure Water Southern California program, which would supply up to 150 million gallons per day (mgd) of potable reuse water to the region from LACSD's A.K Warren Water Resource Facility (Warren Facility). The Warren Facility is a 400-mgd capacity non-nitrifying High Purity Oxygen Activated Sludge Plant currently being evaluated for a 'Flex membrane bioreactor (MBR)' concept that would employ a modular design enabling different reactor modes as needed by the program (Figure 1; Fitzgerald et al., 2024).

One potential mode is nitrification-denitrification (NdN) tertiary MBR (tMBR) using glycerol as the carbon source. This mode would offer additional treatment barriers between wastewater and the product water but at higher operating cost. Initial design utilizing a post-anoxic configuration showed nitrite (NO2) accumulation when tested at demonstration scale (Lai-Bluml and Trussell, 2020). Later designs utilizing a pre-anoxic configuration showed no such issue at bench and pilot scale (Liu et al., 2022; Deco et al., 2023). The current work validates these findings at demonstration scale (~0.6 mgd).

METHODOLOGY
Testing was conducted at the Napolitano Center's Demonstration Plant. The process' flow diagram is illustrated in Figure 2 and was seeded with mixed liquor from a local MBR. Warren Facility secondary effluent was utilized as the feed with characteristics summarized in Table 1. The glycerol source was MicroC-2000 (EOSi, Pocasset, MA). Additional design and operational parameters are summarized in Table 2.

The study included two major phases (Table 3): Phase 1 involved constant flow operation; Phase 2 involved diurnal flow operation, corresponding to program buildout. Routine monitoring results are summarized in Table 4. 16S rRNA metagenomic analysis was performed by DNASense (Aalborg, Denmark).

RESULTS
Observations Fitting Expectations
Figure 3 summarizes MBR filtrate nutrient levels from the study. During constant flow operation (Phase 1), all metrics met the targets: ammonium (NH4) and NO2 were consistently below 1 mgN/L; nitrate (NO3) was at or below 19 mgN/L; and soluble orthophosphate (SOP) was below 1 mgP/L. During initial diurnal flow operation (Phase 2a), process instability was encountered (discussion below). After re-stabilization, diurnal flow operation was revisited with enhanced dissolved oxygen (DO) monitoring (Phase 2c) and again met the targets.

Denitrification stability was judged by anoxic NOx (NO2+NO3) residual, which can correlate with NO2 accumulation (Liu et al., 2022). Anoxic NOx remained stable and low throughout the study (Figure 4), except: (a) during the process instability event (Phase 2a); and (b) when the system was stressed for lower NO3 target (Phase 2c). Carbon demand in chemical oxygen demand (COD) added to nitrogen removed (C/N) was in the expected range of 5~6 g-COD/g-N (Figure 5).

Unexpected Observations
Biological Instability Event
Diurnal testing (Phase 2a) showed periodic NH4 bleed through (Figure 3). This issue was attributed to a faulty DO probe and under-aeration. Airflow was increased in June which addressed NH4 bleed through but led to NO2 accumulation (Figure 6) and broad process instability, including drops in mixed liquor total and volatile suspended solids (MLSS and MLVSS) (Figures 7 and 8) and increases in filtrate SOP (Figure 9), COD (Figure 10), and time-to-filter (TTF; Figure 11). Influent inhibition was ruled out as a cause as the symptoms did not appear in other nitrifying pilots operated in parallel.

The instability event significantly reduced NO2 oxidation, while minimally affected NH4 oxidation (Figure 12). 16S rRNA metagenomic analysis showed a dramatic shift in nitrite-oxidizing bacteria (NOB) population from comammox-dominated to canonical NOB (Figure 13).

Diurnal testing was revisited with enhanced DO monitoring. During this period, the instabilities did not return, suggesting under-aeration as a potential cause for the instability. Additional microbial analyses are underway.

Biomass Yield The modeled biomass yield was ~0.3 lbs-VSS/lb-CODadded, but observations showed ~0.4 lbs-VSS/lb-CODadded (Figure 14). Two hypotheses were proposed: enrichment of specialist heterotrophs and internally stored carbon (ISC), as supported by the following:
- Ordinary heterotrophic organisms (OHOs) typically have a decay rate of 0.67 d-1, while specialist organisms, like methanol utilizers, have lower decay rates near 0.05 d-1. Analysis indicated that a specialist population with a decay rate of ~0.1 d-1 could explain the higher yield observed (Figure 15).
- Microscopy with Neisser staining suggests enrichment of organisms with storage granules (Figure 16).
- Increased airflow during process instability led to a loss of MLSS (Figure 7) and a reduced MLVSS/MLSS ratio (Figure 8), possibly due to rapid ISC oxidation.

BENEFITS AND SIGNIFICANCE
This work demonstrated that pre-anoxic NdN TMBR successfully addresses NO2 accumulation previously observed and met all key performance targets. The instability event encountered may have broader program and industry implications. Most notably, comammox-dominated nitrifying and ISC-driven denitrifying systems may be created with under-aeration and destabilized with a sharp increase in aeration.

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

Presentation time

13:30:00

13:45:00

Session time

13:30:00

15:00:00

SessionApplications and Optimization of MBR Technology

Session locationMcCormick Place, Chicago, Illinois, USA

TopicLiquid Stream Treatment - Nutrient Removal and Recovery

Author(s)

Liu, Michael, Fitzgerald, Colin, Danker, Bryce, Ronn, Alan, Maceiko, Shannon, Deco, Rachel, Mansell, Bruce, Tanuwidjaja, Dian, Constantine, Timothy, Latimer, Ron, Pitt, Paul, Sun, Yewei, Khunjar, Wendell

Author(s)M. Liu1, C. Fitzgerald3, B. Danker4, A. Ronn2, S. Maceiko2, R. Deco1, B. Mansell1, D. Tanuwidjaja2, T. Constantine3, R. Latimer4, P. Pitt4, Y. Sun4, W. Khunjar4

Author affiliation(s)LA County Sanitation District1, Metropolitan Water District of Southern California2, Jacobs Engineering3, Hazen and Sawyer4

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Sep 2025

DOI10.2175/193864718825159963

Volume / Issue

Content sourceWEFTEC

Word count16

A Flexible Design Concept for a 180 MGD MBR Facility

Abstract

Background The Metropolitan Water District of Southern California (MWD) and Los Angeles County Sanitation Districts (LACSD) are jointly developing the Pure Water Southern California (PWSC) program to produce up to 150 MGD of purified water at LACSD's A.K. Warren Water Resource Facility (Warren Facility) in Carson, California. The Warren Facility (Figure 1) is a 400 MGD capacity high purity oxygen activated sludge (HPOAS) facility that discharges treated (non-nitrified) secondary effluent (SE) to the Pacific Ocean. Product water from the PWSC Advanced Water Treatment (AWT) facility would be used for indirect potable reuse via recharge of local groundwater basins and possibly direct potable reuse through raw water augmentation of surface water treatment plants (Figure 2). Nitrogen management is a key component of PWSC and a flexible design approach that allows the facility to be optimized for current treatment needs, while preserving expandability to meet future requirements, is needed. As such, a series of Nitrogen Management Studies (Liang et al., 2019, Fitzgerald et al., 2021; Danker, 2022, LACSD 2023) were conducted to evaluate alternative process trains to manage nitrogen in the AWT feed. Based on these studies, the proposed process train for PWSC includes biological nitrogen removal followed by reverse osmosis and an ultraviolet advanced oxidation. The primary process includes a 180 MGD capacity flexible membrane bioreactor (Flex MBR, Figure 3) that would be fed Warren Facility SE. Additional processes that will be integrated into PWSC will include operation of two existing HPOAS reactors to achieve nitrogen removal and implementation of sidestream deammonification. When constructed, the MBR facility will be one of the largest in world. The Flex MBR includes a modular bioreactor design concept (Figure 4) that allows for the ability to operate in either nitrification only or nitrification-denitrification (NdN) mode. NdN can be achieved by addition of supplemental carbon (glycerol) and/or by blending primary effluent (PE) with SE, referred to as hybrid operation. Hybrid operation is intended to reduce supplemental carbon requirements. To further enhance reductions in supplemental carbon requirements, provisions have been included in the design concept to implement partial-denitrification/anammox (PdNA). Additionally, since the basins will be identically designed, the Flex MBR could also be converted to a traditional secondary MBR with PE feed (Figure 5). Pilot-Scale Testing To inform the Flex MBR design concept, pilot testing was conducted (Deco et al., 2023) for approximately one year to validate a pre-anoxic NdN concept (Figures 6 and 7). This concept was developed to mitigate partial NdN (i.e., nitrite accumulation) that was observed during previous demonstration-scale testing in a post-anoxic configuration (Liang et al., 2020) . In addition, initial proof-of-concept testing of the hybrid operating approach was completed. The study concluded that: (1) hybrid operation could result in significant savings in supplemental carbon addition and thus project life-cycle costs; (2) partial NdN can be effectively mitigated with a pre-anoxic configuration designed to control anoxic zone nitrate loading and associated nitrate residual (Figures 8 and 9); and (3) the post-aerobic zone provides a buffer to prevent high effluent nitrite concentrations in the event that anoxic zone nitrite accumulation does occur. Full-Scale Design Concept and Process Modeling Building on the pilot testing, the full-scale Flex MBR concept was developed and refined. A preliminary site plan at the Warren Facility is shown in Figure 5. Major infrastructure will include an influent pump station, fine screen facility, covered bioreactors, membrane tanks and an equipment building, chemical storage and feed facilities, and an odor control facility. The site layout was developed based on a PWSC program phased implementation plan of 115 mgd (Phase 1) and 150 mgd (Phase 2) product water flow. To facilitate the desired operational flexibility, the modular bioreactor design is partitioned into 12 equal zones (Figure 4). The modular concept utilizes a two-pass bioreactor with a multi-purpose central channel and targeted swing zones. The proposed configuration allows for half of a bioreactor train (one pass) to be taken out of service to reduce the out of service volume for maintenance activities. Bioreactor process simulations were completed utilizing BioWin. Design criteria considered for process simulations are shown in Table 1. Simulations were completed considering both the supplemental carbon-based and hybrid operating approaches. Modeling results are shown in Table 2 and Table 3. Key observations from the process simulations include:

*Nitrogen targets can be met without the use of an internal nitrate recycle

*Hybrid operation requires slightly higher return activated sludge rates, as compared to carbon based operation, to stay below the maximum design membrane tank MLSS concentration of 10,000 mg/L

*To meet the Phase 1 nitrogen target under current average day loading conditions, NdN, and thus carbon or PE feed, is projected to be needed on only 40% of days

*Hybrid operation is projected to result in significant savings in supplemental carbon

*Carbon-based operation simulations indicate that anoxic zone nitrate loading is predicted to align with pilot-scale testing

The Metropolitan Water District of Southern California and Los Angeles County Sanitation Districts are jointly exploring the potential of implementing the Pure Water Southern California program. This paper focuses on summarizing the preferred design concept, which incorporates a flexible MBR that would initially be operated in tertiary mode and fed Warren Facility secondary effluent.

SpeakerFitzgerald, Colin

Presentation time

14:30:00

15:00:00

Session time

13:30:00

15:00:00

SessionOptimization of MBR Technology

Session number210

Session locationRoom 343

TopicAdvanced Level, Facility Operations and Maintenance, Municipal Wastewater Treatment Design

Author(s)

Fitzgerald, Colin, Constantine, Tim, Swaim, Paul, Melitas, Nikos, Natanom-Harrold, Nan, Deco, Rachel, Liu, Michael, Mansell, Bruce

Author(s)C.M. Fitzgerald1, T. Constantine2, P. Swaim3, N.T. Melitas4, N. Natanom-Harrold5, R.M. Deco5, M. Liu5, B.O. Mansell6

Author affiliation(s)1Jacobs, CO, 2Jacobs, MT, 3Jacobs, 4Jacobs Engineering Group, Inc., CA, 5Los Angeles County Sanitation Districts, CA, 6LA County Sanitation District, CA

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2024

DOI10.2175/193864718825159646

Volume / Issue

Content sourceWEFTEC

Word count11

Description: Leveraging Densified Activated Sludge and Partial...

Leveraging Densified Activated Sludge and Partial Nitrification/Denitrification/Anammox within an Integrated Advanced Water Treatment Facility for Large-Scale Potable Reuse

Abstract

The Los Angeles County Sanitation Districts (Districts) have been exploring options for implementing nitrogen removal at the Joint Water Pollution Control Plant (JWPCP), a 400-MGD capacity high purity oxygen activated sludge (HPOAS) facility, due to potential reuse and regulatory drivers. This paper summarizes pilot-scale demonstrations of a secondary BNR (Densified Activated Sludge, DAS) and a tertiary BNR (tertiary moving bed biofilm reactor, TMBBR). These approaches has proven successful at meeting the nitrogen removal targets and provide program enhancements, including densification and PANDA/PdNA.

The Los Angeles County Sanitation Districts are exploring nitrogen removal options at the Joint Water Pollution Control Plant (JWPCP), a 400-MGD capacity high purity oxygen activated sludge (HPOAS) facility, to address potential reuse and regulatory drivers. Two potential approaches developed were a three stage A2O configuration and a tertiary moving bed biofilm reactor. Both approaches were successfully pilot tested and demonstrated the ability to meeting nitrogen removal targets.

SpeakerSun, Yewei

Presentation time

13:30:00

14:00:00

Session time

13:30:00

15:00:00

SessionReconsidering Biological Treatment for Water Purification: Reuse-nutrient Removal-nexus I

Session locationRoom S404c - Level 4

TopicIntermediate Level, Municipal Wastewater Treatment Design, Nutrients, Potable Reuse, Water Reuse and Reclamation

Author(s)

Sun, Yewei

Author(s)Y. Sun 1; B. Danker 2 ; R. Deco 3; H. Long 3; M. Liu 4; A. Laleian 5; N. Melitas 4; B. Mansell 5; P. Ackman 6; P. Pitt 7; W. Khunjar 8; R. Latimer 9; H. Noteboom 10; R.M. Deco 3; H.C. Long

Author affiliation(s)Hazen & Sawyer 1; Hazen & Sawyer 2 ; Los Angeles County Sanitation Districts 3; Los Angeles County Sanitation Districts 3; Los Angeles County Sanitation Districts 4; Los Angeles County Sanitation Districts, 24501 Figueroa Street, Carson, CA, 90745 5; Los Angeles County Sanitation Districts 4; Los Angeles County Sanitation Districts 5; Los Angeles County Sanitation Districts 6; Hazen & Sawyer 7; Hazen & Sawyer 8; Hazen & Sawyer 9; 10; Los Angeles County Sanitation Districts 3; Los Angeles County Sanitation Districts 3;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2023

DOI10.2175/193864718825159099

Volume / Issue

Content sourceWEFTEC

Word count19

Partial Denitrification-Anammox Treatment of Reverse Osmosis Concentrate

Abstract

INTRODUCTION AND OBJECTIVES The A.K. Warren Water Resource Facility (Warren Facility) is owned and operated by the Los Angeles County Sanitation Districts (LACSD). The facility has an average daily dry-weather flow capacity of 400 million gallons per day (mgd) and employs a high-purity oxygen activated sludge (HPOAS) process (Figure 1). Non-nitrified secondary effluent (SE) is chlorinated and discharged to the ocean. LACSD has been investigating nitrogen management options that may be implemented at the Warren Facility to address two drivers: (1) effluent reuse for the Pure Water Southern California (PWSC) program which will produce 150 mgd of purified water and (2) total inorganic nitrogen (TIN) load reduction for ocean discharge. PWSC processes that will be implemented are shown in Figure 2. Implementing nitrification-denitrification (NdN) within PWSC is projected to result in a net reduction in the TIN load discharged to the ocean (~ 49%) relative to continued operation with HPOAS. However, LACSD is proactively investigating alternative approaches to enhance load reduction beyond that achieved by implementing PWSC. Outside of conventional strategies to increase nitrogen removal, the elevated mass of nitrate in the reverse osmosis concentrate (ROC) provides a unique opportunity to reduce ocean nitrogen discharge. While uncommon, approaches considered to denitrify ROC typically incorporate biofilms and high levels of carbon dosing. This paper presents a novel approach developed by LACSD that leverages the nitrate-rich ROC and ammonia-rich HPOAS secondary effluent (SE) (Figure 2, Streams 5 and 7) utilizing a carbon efficient partial denitrification-anammox (PdNA) process. In this approach, ROC and SE would be blended at a target NH4-N/NOx-N ratio in a reactor and supplemental carbon added to drive PdNA (Figure 3). The objectives of this study were to (1) conduct proof-of-concept testing of the ROC/SE Blend PdNA process and (2) develop design criteria that can be used for planning level full-scale process sizing and cost estimation. PILOT SYSTEM AND RESULTS The ROC/SE Blend PdNA pilot system included a batch blend tank, feed pump, single-stage PdNA moving-bed biofilm reactor (MBBR), and supplemental carbon (MicroC 2000) dosing system (Figure 4, Table 1). Supplemental phosphorous (H3PO4) was added directly to the batch blend tank. Seeded MBBR media was taken from an existing mainstream PdNA pilot system that has been in operation at the Warren Facility for over a year (Sun et al., 2024). ROC was produced at the PWSC Grace F. Napolitano Innovation Center (NIC) 0.5 mgd reverse osmosis facility. However, ROC was not always available during testing due to facility shutdowns. Therefore, for part of the study, reactor feed was prepared by spiking SE with NaNO3 or by spiking NaNO3 and NaCl to target the desired NH4-INTRODUCTION AND OBJECTIVES
The A.K. Warren Water Resource Facility (Warren Facility) is owned and operated by the Los Angeles County Sanitation Districts (LACSD). The facility has an average daily dry-weather flow capacity of 400 million gallons per day (mgd) and employs a high-purity oxygen activated sludge (HPOAS) process (Figure 1). Non-nitrified secondary effluent (SE) is chlorinated and discharged to the ocean. LACSD has been investigating nitrogen management options that may be implemented at the Warren Facility to address two drivers: (1) effluent reuse for the Pure Water Southern California (PWSC) program which will produce 150 mgd of purified water and (2) total inorganic nitrogen (TIN) load reduction for ocean discharge. PWSC processes that will be implemented are shown in Figure 2.

Implementing nitrification-denitrification (NdN) within PWSC is projected to result in a net reduction in the TIN load discharged to the ocean (~ 49%) relative to continued operation with HPOAS. However, LACSD is proactively investigating alternative approaches to enhance load reduction beyond that achieved by implementing PWSC. Outside of conventional strategies to increase nitrogen removal, the elevated mass of nitrate in the reverse osmosis concentrate (ROC) provides a unique opportunity to reduce ocean nitrogen discharge. While uncommon, approaches considered to denitrify ROC typically incorporate biofilms and high levels of carbon dosing. This paper presents a novel approach developed by LACSD that leverages the nitrate-rich ROC and ammonia-rich HPOAS secondary effluent (SE) (Figure 2, Streams 5 and 7) utilizing a carbon efficient partial denitrification-anammox (PdNA) process. In this approach, ROC and SE would be blended at a target NH4-N/NOx-N ratio in a reactor and supplemental carbon added to drive PdNA (Figure 3).

The objectives of this study were to (1) conduct proof-of-concept testing of the ROC/SE Blend PdNA process and (2) develop design criteria that can be used for planning level full-scale process sizing and cost estimation.

PILOT SYSTEM AND RESULTS
The ROC/SE Blend PdNA pilot system included a batch blend tank, feed pump, single-stage PdNA moving-bed biofilm reactor (MBBR), and supplemental carbon (MicroC 2000) dosing system (Figure 4, Table 1). Supplemental phosphorous (H3PO4) was added directly to the batch blend tank. Seeded MBBR media was taken from an existing mainstream PdNA pilot system that has been in operation at the Warren Facility for over a year (Sun et al., 2024). ROC was produced at the PWSC Grace F. Napolitano Innovation Center (NIC) 0.5 mgd reverse osmosis facility. However, ROC was not always available during testing due to facility shutdowns. Therefore, for part of the study, reactor feed was prepared by spiking SE with NaNO3 or by spiking NaNO3 and NaCl to target the desired NH4-N/NOx-N ratio and TDS concentration at similar concentrations to the ROC produced at NIC. Analysis of TIN removal performance data normalized to account for carbon dose did not indicate a statistically significant difference in performance based on TDS concentration.

The pilot system was started up in April 2024 and operated for approximately 5 months. Average conditions over a four-month period of stable operation (May to September 2024) are shown in Table 2. Influent TIN and NH4-N/NOx-N ratio, nitrogen loading rates, and supplemental carbon dose are shown in Figures 5, 6, and 7, respectively. Average influent TIN, NH4-N/NOx-N ratio, and supplemental carbon dose were 74 ± 4 mg N/L, 0.45 ± 0.10 g/g, and 1.9 ± 0.45 g COD added/g TIN influent, respectively. Average influent TIN, NOx, and NH4 loading were 0.55 ± 0.05, 0.38 ± 0.05, and 0.17 ± 0.03 g N/m2-day, respectively.

Performance results are summarized in Table 3. Average TIN, TIN removed via PdNA, NOx, and NH4 removals were 57 ± 16%, 63 ± 14%, 57 ± 15%, and 61 ± 29%, respectively. Corresponding average surface area removal rates were 0.31 ± 0.09 (TIN), 0.22 ± 0.06 (NOx), and 0.10 ± 0.04 (NH4) g N/m2-day. Supplemental carbon dose varied between 0.9 — 2.7 g COD added/g TIN influent and had a significant impact on performance (Figures 8 — 10). As carbon dosing increased or decreased over this range, a corresponding increase or decrease in TIN, NOx, and NH4 removal was observed. TIN, NOx, and NH4 removals ranged between 28 to 84%, 27 to 90%, and 17 to 99%, respectively.

PdN efficiency averaged 55 ± 15% and supplemental carbon demand averaged 3.5 ±0.59 g COD added/g TIN removed. Both parameters generally improved from start-up to the end of the study (Figure 11) and over the last month of stable operation averaged 65 ± 9% and 3.1 ± 0.45 g COD added/g TIN removed. The average PdN efficiency observed in this study is within the range reported in the literature for single-stage PdNA MBBR reactors with glycerol addition: 43 ± 29% g COD/g N (Macmanus et al., 2022) and 88 ± 13% g COD/g N (Klaus et al., 2023). However, the average carbon demand observed was ~ 1 g COD/g N higher, but notably lower than the 5 — 6 g COD/g N removed for glycerol driven FdN observed by Liu et al., 2025.

Planning level cost estimates (AACE Class 5) for full-scale implementation were developed to benchmark against previously evaluated concepts (LACSD 2024). Preliminary estimates suggest that ROC PdNA may be a financially viable approach. The presentation will provide a detailed overview of the pilot system.

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

Presentation time

10:30:00

10:45:00

Session time

10:30:00

12:00:00

SessionInnovations in Membrane Treatment for Reuse

Session locationMcCormick Place, Chicago, Illinois, USA

TopicAdvanced Water Treatment and Reuse

Author(s)

Mansell, Bruce, Coracero, Ariana, Deco, Rachel, Hsia, Patricia, Le, Tri, Fitzgerald, Colin, Constantine, Timothy, Sun, Yewei, Khunjar, Wendell, Danker, Bryce, Pitt, Paul

Author(s)B. Mansell1, A. Coracero1, R. Deco1, P. Hsia1, T. Le3, C. Fitzgerald3, T. Constantine3, Y. Sun4, W. Khunjar4, B. Danker4, P. Pitt4

Author affiliation(s)LA County Sanitation District1, City of San Mateo2, Jacobs3

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2025

DOI10.2175/193864718825159935

Volume / Issue

Content sourceWEFTEC

Word count8

Description: Pilot-Scale Investigation of Stormwater Treatment at Various Los Angeles County...

Pilot-Scale Investigation of Stormwater Treatment at Various Los Angeles County Sanitation Districts' Solid Waste Facilities

Abstract

Pilot studies were conducted at the Los Angeles County Sanitation Districts at multiple solid waste facilities to evaluate treatment to remove stormwater contaminants. The study found that influent metal concentrations were correlated with influent TSS. Study results showed that granular media filtration, microfiltration, and granular activated carbon was the most effective treatment system to remove the contaminants of concern at each facility.

The following conference paper was presented at WEFTEC 2021, October 16-20, 2021. To read the full abstract, see "Abstract" tab below.

SpeakerDeco, Rachel

Presentation time

9:30:00

09:50:00

Session time

08:30:00

10:00:00

SessionIndustrial Stormwater: Emerging Requirements, Historical Challenges, and Cutting-edge Treatment Technology

Session number408

TopicFundamental Level, Industrial Issues and Treatment Technologies, Policy and Regulation, Stormwater, Green Infrastructure, and Wet Weather

Author(s)

Rachel Deco

Author(s)R.M. Deco1; P. Ackman2; N. Melitas3;

Author affiliation(s)Los Angeles County Sanitation Districts, Whittier, CA1,2,3

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct, 2021

DOI10.2175/193864718825158090

Volume / Issue

Content sourceWEFTEC

Word count16

Description: Pilot-scale Validation of Tertiary MBR Design Concepts for Potable Reuse in Southern...

Pilot-scale Validation of Tertiary MBR Design Concepts for Potable Reuse in Southern California

Abstract

The Metropolitan Water District of Southern California (Metropolitan) and Los Angeles County Sanitation Districts (LACSD) are jointly exploring the potential of implementing the Pure Water Southern California (PWSC) program, which would include building an Advanced Water Treatment Facility (AWTF) capable of producing a 568 MLD (150 mgd) of purified water at LACSD’s Joint Water Pollution Control Plant (JWPCP) in Carson, CA. A series of studies conducted by both agencies have identified the application of a tertiary membrane bioreactor (tMBR) as a promising approach to provide nitrogen removal downstream of the JWPCP. This pilot study focused on evaluating tMBR design concepts with an emphasis on demonstrating successful operation of nitrification-denitrification (NDN) tMBR concepts. This study showed that NDN operated in a pre-anoxic configuration either utilizing supplemental carbon or primary effluent provides a promising approach for PWSC and potential future ocean discharge requirements for JWPCP

Pure Water Southern California is a potential reuse program to provide substantial water resiliency to Southern California. A series of studies identified use of a tertiary membrane bioreactor as a promising approach to manage nitrogen prior to advanced water treatment. The Los Angeles County Sanitation Districts initiated this pilot study to refine design and operational characteristics of the process.

SpeakerDeco, Rachel

Presentation time

16:00:00

16:20:00

Session time

15:30:00

17:00:00

SessionRefining Wastewater Effluent for Purification: Reuse-nutrient Removal-nexus II

Session locationRoom S404a - Level 4

TopicIntermediate Level, Municipal Wastewater Treatment Design, Nutrients, Potable Reuse, Water Reuse and Reclamation

Author(s)

Deco, Rachel

Author(s)R. Deco 1; B. Mansell 2 ; M. Liu 3; N. Melitas 3; C. Fitzgerald 4; T. Constantine 5; P. Swaim 6; R. Deco 1;

Author affiliation(s)Los Angeles County Sanitation Districts 1; Los Angeles County Sanitation Districts 2 ; Los Angeles County Sanitation Districts 3; Los Angeles County Sanitation Districts 3; Jacobs Engineering Group 4; Jacobs Engineering 5; Jacobs Engineering 6; Los Angeles County Sanitation Districts 1;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2023

DOI10.2175/193864718825159134

Volume / Issue

Content sourceWEFTEC

Word count14

Snail Away: Snail Mitigation of Nitrification-Only Tertiary MBR

Abstract

ABSTRACT
Physa genus snails were observed during nitrification-only tertiary membrane bioreactor (N-only tMBR) operation in support of Pure Water Southern California, a joint program between the Los Angeles County Sanitation Districts (LACSD) and the Metropolitan Water District of Southern California (MWD) to provide potable reuse water to Southern California. Development and testing of bench-scale protocol and pilot-scale testing evaluated several mitigation strategies including influent ultra-fine screening, free ammonia exposure, acute anoxia, chlorination, sodium chloride and iron. Results indicated that ultra-fine screening and free ammonia exposure were the most effective strategies to implement. These strategies will be tested at demonstration-scale at a 0.6 mgd facility to validate snail suppression effectiveness.

INTRODUCTION
Pure Water Southern California is a joint program being pursued by the Los Angeles County Sanitation Districts (LACSD) and the Metropolitan Water District of Southern California (MWD) to provide a new source of water for Southern California. Effluent from LACSD's largest facility, the A.K. Warren Water Resource Facility (Warren) will be treated for nutrient removal and advanced water treatment to meet potable reuse standards prior to distribution in the region (Figure 1). In advance of implementation, the Grace F. Napolitano Innovation Center's Demonstration Plant (Demonstration Plant) was built to evaluate nitrogen removal alternatives. While operating in nitrification-only tertiary membrane bioreactor (N-Only tMBR) mode, snails identified as Physa genus were observed in the membrane tanks, likely sourced from Warren secondary effluent (SE) (Figure 2). While initially addressed with more frequent membrane cleaning, snail proliferation could cause significant increases to both capital and operational costs at full-scale. Planning began in 2023 to provide viable snail mitigation options for future retesting at demonstration-scale and planning for full-scale operation. Potential mitigation measures based on literature review and previous experience were compiled and ranked with the most promising selected for evaluation (Table 1).

OBJECTIVES
The objective was to evaluate the most viable snail prevention, mitigation, and recovery measures identified from literature review and determine the most effective approaches for implementation at the Demonstration Plant and consideration for full-scale implementation.

METHODOLOGY
A bench-scale protocol using snails harvested and grown at the Warren Facility was developed that included the verification of snails of the genus Physa. The snails were placed in an acclimation tank filled with nitrified Warren SE, aerated, and fed with activated sludge from nitrification-denitrification water reclamation plants (Figure 3). The snails were acclimated and tested after reaching maturity. Ten snails were tested per batch in aerated Warren SE (unaerated for anoxic testing) in each test beaker. Ten snails were added to a second beaker to serve as the control. After each test, snails were placed in aerated SE for recovery and observed at 24 and 48 hours. The 48-hour mortality was reported. A separate protocol was developed for iron due to suppression from bioaccumulation. Mitigation measures tested at bench-scale are shown in Table 2.

Pilot-scale evaluation consisted of operating an existing pilot-scale tMBR (Figure 4) in N-only mode from April to September 2023 to determine if snails would proliferate under these conditions (Table 3). Monthly MBR snail observations were performed. An additional pilot was constructed to evaluate ultra-fine screening. A 75-micron and a 150-micron screen were evaluated alongside a 9.5 mm screen as control (Figure 5). Snails were seeded inside each mesh screen, and the holding tank was monitored to measure screen-size effectiveness. Further pilot modification was performed to optimize successful bench-scale strategies and mitigation strategies that were inconclusive at bench-scale due to the acute testing protocol.

<B>RESULTS AND DISCUSSION
Bench-scale testing results (Table 4) indicated that the 4000 mg/L NH4Cl at pH 9 showed the highest mortality with an average 48-hour mortality > 97.5%. Anoxic conditions, short-term chlorination, sodium chloride and iron exposure showed minimal to no mortality when compared to control. However, anoxic conditions will be further evaluated at the demonstration scale due to observed suppression in previous nitrification-denitrification modes at the Demonstration Plant. Anoxic conditions and chlorination may be more effective on suppression of younger life stages during continuous operation. Therefore, chlorination will also be re-evaluated at pilot-scale in flow-through mode and at demonstration scale.

Operation of N-only tMBR was successfully replicated at pilot-scale (Figure 6). However, monthly MBR observations did not show snail proliferation (Figure 7), possibly due to weekly hypochlorite and citric acid cleaning and will be further evaluated individually. Results showed that 75-micron screening was effective at snail suppression, but 150-micron screens might allow eggs to pass through the screen after one month (Figure 8). Additional work of ultra-fine screening is planned at pilot-scale and will also be incorporated in future testing at the Demonstration plant.

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

Presentation time

13:30:00

13:45:00

Session time

13:30:00

15:00:00

SessionTertiary Filtration: Case Studies for Design Optimization

Session locationMcCormick Place, Chicago, Illinois, USA

TopicLiquid Stream Treatment Technology - Secondary & Tertiary Treatment

Author(s)

Lynch, Bellanira, Deco, Rachel, Adams, Scott, Reinke, Ryan, Mansell, Bruce, Thompson, Shawn, Robinette, Matthew, Danker, Bryce, Fitzgerald, Colin, Di Giovanni, George

Author(s)B. Lynch1, R. Deco1, S. Adams1, R. Reinke1, B. Mansell1, S. Thompson1, M. Robinette1, B. Danker2, C. Fitzgerald3, G. Di Giovanni4

Author affiliation(s)LA County Sanitation District1, Hazen and Sawyer2, Jacobs3, Metropolitan Water District of Southern California4

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2025

DOI10.2175/193864718825160071

Volume / Issue

Content sourceWEFTEC

Word count9

Base text size -

Deco, Rachel

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