Doody, Alexandra

Ms. Doody is a principal environmental engineer and treatment process specialist at CDM Smith in Austin, Texas. Her professional experience ranges across the lifecycle of water reclamation projects, including bench-scale and pilot-scale treatability studies, process alternatives evaluation, mechanical design and construction oversight, as well as optimization and fine-tuning of process performance and operational costs. She also serves as CDM Smith's nutrient removal discipline leader.

Titles from this speaker

Description: Densification with Hydrocyclones: From Concept to Reality for BNR Improvements in...

Densification with Hydrocyclones: From Concept to Reality for BNR Improvements in Wichita, Kansas

Abstract

Selectively wasting poorer settling filaments and lighter mixed liquor particles and exposing mixed liquor to high F/M unaerated selectors can promote better settling sludge that can also yield additional benefits. Such benefits may include selective retainment of microorganisms that are beneficial for biological nutrient removal (BNR) and a reduction in pathogens that must be disinfected. This paper summarizes results from a pilot study of selective sludge wasting using hydrocyclones at a water resource recovery facility (WRRF) in Wichita, Kansas including improved settleability, more robust nitrification, and reduced E. coli counts in the clarified effluent. This paper also presents the design criteria and layout for a full-scale hydrocyclone facility that will be constructed from 2024-2027 as part of a BNR upgrade at the City’s Plant 2 WRRF.

Selectively wasting poorer settling particles can promote not only better settling sludge, but also retainment of microorganisms beneficial for nitrification and a reduction in pathogens. This paper summarizes results from a pilot study of selective sludge wasting using hydrocyclones at a facility in Wichita, Kansas as well as the design for a full-scale hydrocyclone facility that will be constructed in a BNR upgrade of the City's Plant 2 WRRF.

SpeakerDoody, Alexandra

Presentation time

14:00:00

14:20:00

Session time

13:30:00

15:00:00

SessionApplying Hydrocyclones for Densification

Session locationRoom S501a - Level 5

TopicFacility Operations and Maintenance, Intermediate Level, Municipal Wastewater Treatment Design, Nutrients, Research and Innovation

Author(s)

Doody, Alexandra

Author(s)A.T. Doody 1; J. Belden 2 ; A. Mande 3; M. Nelis 3; E. Staunton 4; S. Stewart 5; S. Mathur 6; A. Doody 1; J. Belden 2;

Author affiliation(s)CDM Smith, Inc. 1; City of Wichita, Kansas 2 ; CDM Smith, Inc. 3; CDM Smith, Inc. 3; CDM Smith, Inc. 4; CDM Smith, Inc. 5; CDM Smith, Inc. 6; CDM Smith, Inc. 1; City of Wichita, Kansas 2;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2023

DOI10.2175/193864718825159208

Volume / Issue

Content sourceWEFTEC

Word count14

Sidestream EBPR is About the Fundamentals: Simple Strategies to Enhance Biological Phosphorus Removal

Abstract

Over the past decade, increased attention has been placed on enhanced biological phosphorus removal (EBPR) configurations that include fermentation of a portion of the activated sludge biomass. Often this is accomplished in a sidestream reactor, and thus is referred to as sidestream enhanced biological phosphorus removal (S2EBPR). Recent research suggests that S2EBPR configurations promote more stable and lower effluent orthophosphate concentrations due to a more diverse microbial ecology compared to 'conventional EBPR' configurations. Such research suggests that S2EBPR encourages the selection for a larger prevalence of fermentative phosphorus-accumulating organisms (PAOs) which can metabolize a wide range of carbon sources in addition to volatile fatty acids. This scenario may improve process performance by reducing the reliance of the EBPR process on influent carbon in the form of VFAs. Four S2EBPR configurations that promote biomass hydrolysis and fermentation include: (1) sidestream RAS fermentation, (2) sidestream RAS fermentation with supplemental carbon addition, (3) sidestream mixed liquor suspended solids (MLSS) fermentation; and (4) mainstream unmixed in-line MLSS fermentation (UMIF). A Water Research Foundation (WRF) project (Project 4975) studied S2EBPR configurations to provide practical design guidance, operating tools, and modeling best practices for EBPR processes using biomass fermentation. Results of a UMIF full-scale pilot conducted at the Geneva WWTP in 2020 as part of this Project will be presented. The 5.0 mgd Geneva (Illinois) Wastewater Treatment Facility (WWTF) completed a major process improvements project in 2019, including modifications to the conventional activated sludge process to provide EBPR to meet tightening discharge permit requirements, including a total phosphorus limit of 1.0 mg/L. Bioreactor upgrades were recently completed to promote EBPR to meet this limit. The bioreactor design provides the flexibility to operate in either a 'conventional EBPR' design using an A2O configuration, or to operate with A2O in a UMIF configuration by turning off mechanical mixers in the second of two anaerobic zones and only operating them for 15 minutes per day. The retained sludge ferments at the bottom of the tank and generates VFAs. This sludge is continuously pumped at a rate of about 10 percent of the forward flow from the UMIF zone to the first anaerobic zone. This internal return flow distributes VFAs into the mixed liquor, where they become available to PAOs. During the commissioning of the EBPR process, the secondary treatment process was operated in three configurations: A/O, A2/O with nitrate recycle to Anoxic Zone A, and A2/O with nitrate recycle to Anaerobic/Aerobic Swing Zone B. Ortho-phosphorus profiles through the bioreactors are shown in Figure 1 for each of these configurations before operating in a UMIF configuration. Note that in this figure, each color reflects a different operating configuration, and the two lines for each color reflect the two individual bioreactors used in the study. The phosphorus profiles in each bioreactor were similar for each BNR configuration sampled, with effluent averaging about 0.6 mg/L in each. Following the commissioning period, the operators began piloting the UMIF mode to increase the anaerobic SRT, provide seed biomass for downstream anoxic/aerobic treatment, and encourage hydrolysis and fermentation of the settled MLSS which can be recycled to the head of the anaerobic zone with a recycle pump. The plant operated a UMIF pilot train in parallel with a conventional A2O train to compare their performance. Ortho-phosphorus profiles through the bioreactors under UMIF conditions are shown in Figure 2, with effluent averaging about 0.06 mg/L. The following observable trends were noted:

*Significant decrease in ortho-phosphorus concentration in the anoxic zones. This is primarily attributable to dilution by the nitrate recycle stream, though it may also be possible that some phosphorus uptake may occur by denitrifying PAOs due to the introduction of nitrate.

*A sharp decline in the ortho-phosphorus concentration in the first oxic zone. This is attributable to the sheer size of the Oxic Zone A, which is the single largest zone in the bioreactor, allowing for the longest hydraulic retention time in which phosphorus uptake can occur in an aerated zone.

*Operation with UMIF has resulted in excellent EBPR performance, with UMIF resulting in significantly lower orthophosphate concentrations in the final aerated zones in the bioreactors. This UMIF pilot demonstrates how a simple operational modification, like turning mixers on and off, can improve phosphorus removal with no capital improvements or time-consuming operational modifications. The UMIF configuration has positioned the WWTF well for upcoming further tightening of the TP limits to 0.5 mg/L. This presentation will provide not only a description of the anaerobic zone mixer operating strategy and how it improved EBPR performance, but will also include lessons learned and guidelines for operators to consider to fine tune the mixing strategy for their plant to avoid unintended negative consequences, such as increased ammonia release and resulting nitrite accumulation in the aerobic zones.

Enhanced biological phosphorus removal (EBPR) is a common process for permit compliance and protecting water resources, however performance can be unstable. Sidestream EBPR can improve performance by promoting the fermentation of biomass from the biological process in a sidestream reactor. The Geneva (Illinois) WWTF recently upgraded bioreactors for operation in multiple EBPR configurations, including unmixed in-line fermentation (UMIF), resulting in reduced effluent phosphorus concentrations.

SpeakerLubenow, Brian

Presentation time

10:30:00

11:00:00

Session time

10:30:00

12:00:00

SessionUsing Side-Stream Enhanced Biological Phosphorus Removal to Improve EBPR Performance

Session number523

Session locationRoom 350

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

Author(s)

Lubenow, Brian, Beaton, Nigel, Doody, Alexandra, Staunton, Eric, Vangyseghem, Bob

Author(s)B. Lubenow1, N. Beaton2, A. Doody3, E.T. Staunton4, B. Vangyseghem5

Author affiliation(s)1CDM Smith, Inc., 2CDM Smith, Inc., 3CDM Smith, Inc., 4CDM Smith, Inc., 5City of Geneva, IL

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2024

DOI10.2175/193864718825159694

Volume / Issue

Content sourceWEFTEC

Word count14

Wet Weather Capacity Can't be Built in a Day, But Improved Settleability Can Shift the Paradigm Quickly

Abstract

Introduction Johnson County Wastewater (JCW) desires to achieve treatment of 3Q (three times dry weather flow) during wet weather at all of its six WRRFs. JCW has presented at prior conferences how it pioneered the use of dual-purpose cloth filters for auxiliary treatment of wet weather flows at its Tomahawk Creek Treatment Facility (Szerwinski, 2023). This paper highlights an alternate approach taken by JCW at its Middle Basin Treatment Facility (Middle Basin) to improve peak flow capacity over the past 15 years, including results from a successful pilot of InDENSE hydrocyclones in 2023. Full-scale implementation of hydrocyclones will allow JCW to defer further into the future a costly upgrade to cloth filters for auxiliary treatment. Middle Basin WWTF Middle Basin has a permitted capacity of 55 million liters per day (MLD) and it currently treats an annual average flow of about 45 MLD. Figure 1 is a process flow diagram of liquid treatment facilities at Middle Basin, which has four independent trains each consisting of a primary clarifier, aeration basin, and secondary clarifier. The secondary effluent is then disinfected with ultraviolet (UV) lamps. These facilities are referred to as the Mechanical Plant. The fourth train was constructed from 2008-2010 to reduce the frequency of discharges from the facility's Equalization Lagoons to Indian Creek during wet weather. Previously, discharge from the Lagoons was allowed in the facility's permit if sodium hypochlorite was dosed and if numerical permit limits were met. However, numerical limits were not consistently met and thus the fourth train was built to improve performance. This expansion nominally designed the upgraded Mechanical Plant for a peak flow capacity of 87 MLD, which is only a 1.6 peaking factor (1.6Q) relative to the facility's permitted annual average capacity. Even though not required by permit limits, JCW also voluntarily converted the aeration basins into biological nutrient removal (BNR) basins configured in a modified Johannesburg process. Peak Flow Optimization Table 1 provides a timeline of the measures implemented over the past 15 years to incrementally increase the peak flow treated through its Mechanical Plant BNR trains. Addition of the fourth train substantially increased peak flow capacity of Mechanical Plant from only 1.2-1.5Q up to about 2Q. The quantity of discharges from the Lagoons was reduced by 87% on average. The number of days requiring lagoon discharge reduced from an average of 45 to 12 days per year. JCW experimented with additional operational changes -- some of which were successful and others which were not -- and both will be discussed further in our paper. The 2020-2022 improvements shown in Table 1 yielded a Mechanical Plant capacity regularly exceeding 2Q capacity up to about 98 MLD. The discharges from the lagoons reduced to an average of about 43 million liters (11 million gallons) and only 4 days per year. The reductions achieved in lagoon discharges from 2010-2022 were worth celebrating, but JCW has sought to find ways to continue increasing capacity while also reducing stress on operations staff by seeking improved sludge settleability to gain more secondary clarification capacity. Worse SVI30 often coincides with the rainiest months from March to May (Figure 2), and so sludge settleability has been the greatest limit to further reductions in lagoon discharge. This led JCW to initiate a pilot of InDENSE hydrocyclones in January 2023 to test how improvements in sludge settleability could enhance peak wet weather capacity. InDENSE Pilot Results Selectively wasting poorer settling particles and filaments from an activated sludge basin has been shown to improve sludge settleability. This can be accomplished with surface wasting or with external selectors. The use of hydrocyclones as an external selector to accomplish selective wasting is seeing increased adoption at municipal facilities (Sturm, 2020; Avila, 2021; Regmi 2022). The Middle Basin layout offered a unique opportunity to pilot InDENSE hydrocyclones for sludge wasting on one of the two worst performing BNR trains, while having the identical BNR train adjacent to it for comparison as a control train. Three weeks after startup of the pilot, JCW observed that the 5-minute settleability of mixed liquor in the pilot train decreased significantly below the independent control train (Figure 3). Six months into the pilot, benchtop settling velocity tests (Figure 4) were performed to characterize the capacity of the clarifiers, which is shown in Figure 5. These results correlate to the JCW staff's full-scale experience during a major storm event in February 2023, where the sludge blankets rose rapidly in the control train while less than 2-foot blankets were retained in the InDENSE train. Conclusion This paper will present what has and has not worked to increase peak flow capacity at Middle Basin WWTF, including a successful pilot in 2023 using InDense hydrocyclones for sludge wasting. Although a hydraulic bottleneck capital projects will be needed to further increase peak flow capacity, the implementation of InDENSE with these hydraulic improvements will help JCW to defer further into the future a costly upgrade to dual-purpose cloth filters to attain 3Q.

This paper describes the effective and ineffective measures taken to increase peak flow capacity at the Johnson County Wastewater Middle Basin Wastewater Treatment Facility, highlighting in particular the success of two measures: (1) a simple change in standard operating procedure (SOP) by operations personnel and (2) a pilot started in January 2023 using inDENSE hydrocyclones for selective sludge wasting to improve sludge settleability in the final clarifiers.

SpeakerDoody, Alexandra

Presentation time

15:30:00

16:00:00

Session time

15:30:00

17:00:00

SessionOptimizing Design for Increased Capacity

Session number228

Session locationRoom 349

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

Author(s)