Barker, Leila

Leila Barker is a Senior Engineer in the Research and Innovation Department at Clean Water Services, where she works on process engineering and research related to permit compliance and process optimization. Her focuses include running treatment plant process models and analyzing data from the District's 90-acre Natural Treatment System. Prior to pursuing engineering, she earned an undergraduate degree in violin performance, and she enjoys getting opportunities to experience live New Orleans jazz.

Titles from this speaker

Copper Removal in Constructed Surface Wetlands and Subsurface Pilot Reactors

Abstract

The Forest Grove Wastewater Treatment Facility (WWTF) discharges to a receiving stream with low dissolved organic carbon, ionic strength, and pH. These characteristics tend to result in restrictive water quality criteria for copper under the Biotic Ligand Model. Since 2017, the WWTF has directed treated effluent into a 95-acre Natural Treatment System (NTS) during the dry season (May through October) prior to discharge. Monitoring has demonstrated that these surface wetlands, with a design hydraulic retention time of four to five days, consistently remove soluble copper to <3.5 μg/L at a range of flow conditions. Alternative treatment technologies have been explored to improve effluent quality at other times of the year when the NTS is flooded and the WWTF discharges directly to the river. Subsurface flow pilot reactors with wood chip and biochar media were found to lower soluble copper concentrations to ≤4 μg/L at residence times greater than one day.

SpeakerBarker, Leila

Presentation time

08:30:00

08:50:00

Session time

08:30:00

09:30:00

SessionEffluent Polishing in the Real World

Session number509

TopicAdvanced Level, Municipal Wastewater Treatment Design, Nutrients, Water Reuse and Reclamation

Author(s)

L. BarkerB. BaumgartnerM. HodgesR. KapurK.J. Williamson

Author(s)L. Barker1; B. Baumgartner1; M. Hodges1; R. Kapur1; K.J. Williamson1;

Author affiliation(s)Clean Water Services, OR1

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2020

DOI10.2175/193864718825157464

Volume / Issue

Content sourceWEFTEC

Word count11

Development of Facility-Specific Zinc and Copper Nitrification Inhibition Thresholds for Local Limits Analysis

Abstract

Summary Publicly owned treatment works (POTWs) frequently use U.S. EPA-published data on nitrification inhibition thresholds to derive local limits for industrial users discharging to their water resource recovery facilities (WRRFs). For many constituents, the range of threshold values can vary by an order of magnitude or more. Many POTWs, lacking more specific information, consequently default to the most conservative guidelines when setting local limits. Clean Water Services (CWS) conducted nitrification rate testing at its WRRFs to identify facility-specific zinc (Zn) and copper (Cu) nitrification inhibition thresholds and translated these data to local limits. The resulting levels were higher than the EPA-published minimum thresholds for both metals while still providing confidence that resulting local limits would be protective of biological nitrogen removal processes at each WRRF. Background Controlling industrial discharges to a POTW is an integral part of the NPDES permit program. In conducting local limits analyses to establish limits for industrial discharges, POTWs consider several factors, including water quality standards, water quality-based NPDES permit effluent limits, biosolids use and disposal, and the potential for inhibition of WRRF biological processes. The most conservative of these values is used to establish the local limit. Limits are often driven by the need to shield the biological nitrification process from inhibition. EPA has published nitrification inhibition threshold values for a variety of substances in its Local Limits Development Guidance (EPA, 2004). For many substances, a wide range of possible inhibition levels have been identified. Because the data are decades old and studies are not well documented, there is limited confidence that even the most conservative thresholds would be protective of biological treatment processes. Additionally, use of the most conservative values can result in overly stringent local limits that place a significant burden on industrial users. Three CWS facilities rely on biological nitrification to meet ammonia effluent limits. Preliminary analysis suggested that local limits for Cu and Zn would likely be driven by the nitrification inhibition threshold. Given the wide range of inhibition levels in the EPA Guidance (0.05 to 0.48 mg/L for Cu and 0.08 to 0.50 mg/L for Zn) and the fact that CWS WRRFs have experienced influent levels above the lower end of the defined ranges with no discernible impact to the biological processes, CWS decided to conduct testing to establish site-specific nitrification inhibition levels for Cu and Zn for use in local limits analysis. Methods Testing used a modified version of ISO 9509:2006, which assesses the short-term inhibitory effect of substances on nitrifying bacteria in activated sludge over the course of several hours. The test substance is added to return activated sludge (RAS), which is spiked with a buffered ammonia substrate and aerated at constant temperature and pH while nitrate is measured to determine the rate of nitrification. Six reactors were operated concurrently, with varying levels of Zn or Cu dosed into five reactors. Each test included one control against which the nitrification rates of the dosed samples were compared (Figure 1). RAS from each of the three nitrifying facilities was tested. Nitrate was graphed vs. time (Figure 2) and nitrification rates were derived from the slopes, normalized to 20 degrees C using a temperature correction factor, and compared to the nitrification rate of the DI control. Most testing focused on levels below 5 mg/L, though several tests used doses as high as 55 mg/L. Samples were taken from several reactors at the end of each test and analyzed via ICP-MS to determine the total concentration of metals in each reactor, including the dose and background metals present in the RAS. Concentrations of metals in short-term batch tests do not directly translate to WRRF influent concentrations. Influent and RAS metals data, along with data on average primary and secondary removal efficiencies and typical summer SRTs and HRTs, were used to compute an average RAS-to-influent concentration factor for each metal at each WRRF. This factor was correlated with inhibition test results to calculate raw influent concentrations that, if sustained over time, would result in the test concentrations. Results were then fitted to a logistic sigmoidal equation to define a threshold for a response. Results Nitrification rates were normalized against controls and plotted against the concentration of Zn or Cu in each reactor (Figure 3, Figure 4). Durham and Forest Grove WRRF tests showed generally stable nitrifying activity at lower metal concentrations, with a downward trend starting around 2 mg/L for both metals. Rock Creek WRRF results did not demonstrate clear inhibition in this range, but the dataset for this facility was less extensive and included only three tests with metals concentrations above 2 mg/L. An example of the calculated raw influent response threshold curve is shown in Figure 5. Significance Published inhibition guidance may not be informative for POTWs wishing to protect biological treatment processes when establishing local limits for industrial users. Site-specific testing can be used to provide greater confidence in the local limits that are established and in their ability to protect biological processes at WRRFs.

Clean Water Services conducted tests to identify facility-specific zinc and copper nitrification inhibition thresholds at its WRRFs. This provided the technical basis to establish higher local limits with confidence that the biological treatment processes at each WRRF would not be negatively impacted. This work demonstrates how a short-term study can be carried out to reduce uncertainty and gain an improved understanding of risk, supporting the needs of both WRRFs and local industries.

SpeakerBarker, Leila

Presentation time

10:30:00

11:00:00

Session time

10:30:00

12:00:00

SessionAccommodating Industrial Effluents in Municipal Treatment Facilities

Session number519

Session locationRoom 340

TopicIndustrial Issues and Treatment Technologies, Intermediate Level, Municipal Wastewater Treatment Design

Author(s)

Barker, Leila, Kapur, Rajeev, Baumgartner, Bob, Schauer, Peter

Author(s)L.K. Barker1, R. Kapur2, B. Baumgartner1, P. Schauer1

Author affiliation(s)1Clean Water Services, OR, 2, OR

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2024

DOI10.2175/193864718825159571

Volume / Issue

Content sourceWEFTEC

Word count14

Living Capital Planning Tools

Abstract

INTRODUCTION Clean Water Services (CWS) operates four WRRFs that are expanded and improved through a ~$40 million yearly capital budget. The goal of the CWS capital planning approach is to have a level capital outlay year to year. Capital expenditures are reprioritized yearly to achieve this goal and to ensure that processes are expanded only as they reach capacity. Typical master planning approaches are updated only about every five years. A 'living' capital plan allows CWS to adapt to changes in critical assumptions that drive planning timelines and proactively manage capital expenditures. This paper presents the CWS approach to creating and managing a living capital plan and summarizes the benefits. OVERVIEW The first integrated capital planning tool was developed for the Durham WRRF in 2020 with Carollo and Jacobs, the consultants for the most recent Durham master plan project (Figure 1). As part of the ongoing West Basin master plan, work is underway with Carollo to develop the tool for the three interconnected West Basin facilities, which include Rock Creek, Hillsboro and Forest Grove (Figure 1). The initial pieces of the tool are developed in collaboration with consultants but the final product is owned and managed by CWS. The goal of the living capital planning tool is that it's updated every year and should improve and evolve over time. OUTCOMES FLOW AND LOAD PROJECTIONS Flow and load projections are developed from base assumptions in the flow and load spreadsheet. The process of building the spreadsheet provided CWS with a comprehensive understanding of all the critical assumptions used to generate the projections, making it easier to evaluate those assumptions over time. Alternate planning scenarios were also created based on differing growth assumptions for the Durham WRRF, and flow diversion alternatives for the West Basin WRRFs. Historic flows and loads are evaluated annually and compared to projections. Tracking observations against planning numbers makes it evident when revisions are necessary (Figures 2 and 3). While the intention is not to revise the projections every year, the spreadsheet tool and yearly evaluation process is meant to make the effort for revising projections more efficient when needed. PROCESS PERFORMANCE AND DESIGN CRITERIA Design criteria, which set the capacity of the unit processes (e.g. solids loading rate), and process performance criteria, which are assumptions based on operational observations (e.g. percent removal, solids capture, sludge volume index) are also evaluated yearly. The data validation and process capacity spreadsheets gather process performance assumptions and design criteria from the master plan and compare them to historical observations. This comparison determines when unit processes are approaching capacity triggers and identifies when unit processes should be optimized due to declining performance. One example of a process performance parameter (capture in the primary solids thickening process, Figure 4) that drove the capital planning timeline for secondary treatment (Figure 5) is illustrated here. Lower solids thickening capture sends additional solids loads to the secondary process, decreasing its treatment capacity. Just this single assumption changed the secondary capacity trigger year by 4 years (Figure 5). With projects at four WRRFs to phase, improving this 4-year discrepancy in secondary capacity allows capital outlay to be phased more effectively. MASS BALANCE SPREADSHEET VERUS PROCESS SIMULATOR CWS uses both a process simulator and a spreadsheet mass balance model to create solids projections for its West Basin WRRFs. The mass balance spreadsheet can be used to quickly evaluate scenarios that require a lower level of sensitivity and to identify scenarios that could have a major impact to timelines. This simpler, quicker approach is beneficial with the three interconnected West Basin treatment facilities as running a process simulator with all three WRRFs connected is complex and prohibitively slow. However, the process simulator generates more detailed predictions within each individual facility that are beneficial for informing comprehensive planning evaluations. Table 1 compares CWS experiences using these tools. CWS aims to extend both approaches to its East Basin capital planning system to take advantage of their complementary strengths. LESSONS LEARNED The living capital planning approach means that planning is not confined to periodic, consultant-lead master planning efforts. Tracking of flows and loads and other critical assumptions yearly against master planning values has provided valuable insights into when capacity and capital planning shifts are needed. It also daylights areas of conservatism or risk as capacity triggers are reached. Even if a utility is not running models or doing the projections themselves, tracking assumptions against reality is beneficial and achievable for any utility. Other benefits: Having ownership over the data and tools gives CWS the independence to quickly evaluate new scenarios (e.g. impact of a new large industrial user or shifts in population growth). Daylighting and tracking assumptions also aids in documenting the information that drives capital planning decisions. The integrated tool makes capital planning information more accessible to a wider range of CWS stakeholders from executive managers to operators.

This presentation presents the Clean Water Services approach to creating and managing a living capital plan and summarizes the benefits. The goal of our approach is to daylight areas of conservatism and risk as capacity triggers are reached and to routinely review unit process performance and plant influent flows and loads to catch and address deviations as they arise.

SpeakerMenniti, Adrienne

Presentation time

16:30:00

16:50:00

Session time

15:30:00

17:00:00

SessionLeveraging Automation and Analytics for Better Situational Awareness and Optimization: Part II

Session number224

Session locationRoom 350

TopicEnergy Production, Conservation, and Management, Facility Operations and Maintenance, Intelligent Water, Intermediate Level, Nutrients

Author(s)

Menniti, Adrienne, Sosa-Hernandez, Ornella, Barker, Leila, Schauer, Peter

Author(s)A. Menniti1, O. Sosa-Hernandez1, L.K. Barker1, P. Schauer1

Author affiliation(s)1Clean Water Services, OR

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2024

DOI10.2175/193864718825159537

Volume / Issue

Content sourceWEFTEC

Word count5