Maley, John

Mr Maley has been designing wastewater treatment plants for 19 years. Before his career in water/wastewater Mr. Maley work in maintenance and construction.

Titles from this speaker

Acute Digester Heating Issue Uncovers Chronic Plant Ailment

Abstract

PROBLEM STATEMENT/PURPOSE: In the Spring of 2020, the Little Patuxent WRF digesters had been running for a little over year when an anomaly occurred; the digesters began dropping in temperature. The purpose of this case study is to walk through the complex troubleshooting process that led to discovering an unexpected root cause. The troubleshooting and eventual solution to the temperature issue shed light on the fact that it was just a symptom of a much more systemic ailment. The clue that led to the discovery of the systemic issue was a mysterious sudden significant change in sludge density that appeared in historian data on Christmas Day 2019. The case study will then detail the investigation into the chronic issue and the eventual testing and recommendation of mitigation strategies. The forensic team included the Little Patuxent operations group, HDR experts, and industry experts notably the late Dr. David 'FlocDoc' Jenkins. The case study will wrap up with key take aways from both a process mechanical design and an operations perspective. This case study will focus on the trouble shooting methodology. BACKGROUND: Between 2017 and 2021 the Little Patuxent WRF in Savage, MD underwent a 2-phase biosolids upgrade with the first phase incorporating gravity and belt thickening, anaerobic digestion, phosphorous removal, sludge holding, and centrate deammonification. The 2nd phase added a dryer facility that included sludge conveyance, Cake storage, belt dryers, dried biosolid conveyance and storage. The case study that is the topic of this abstract occurs during a period when phase 1 was fully constructed and online and phase 2 was still under construction. METHODOLOGY: The initial temperature drop trouble shooting involved heat and mass balance evaluations centered around the digester heating recirculation and heat exchange system (heating loop). These evaluations showed that flow through the heating loop was slowing causing a compounding issue of heat exchanger fouling due to inadequate scouring velocity and a laminar flow condition both of which degrade heat exchange capacity. These issues occurred suddenly after the digesters had already been in service for over a year. The cause was found to be gas entrainment in the pump suction piping as well as gas binding at the recirculation pump impeller. Piping and pump modifications were made to address the acute issue of gas release in the heating loop. The case study will detail the modifications made, but in general they involve: - Modify piping to convey versus trap gas release - Trial and eventual purchase of a different type of recirculation pump. Parallel to the modifications made to heating loop the investigation continued into finding the root cause of the out of the ordinary gas release in the sludge. Online sludge density data revealed that the sludge density rapidly decreased from an SG of 1 to an SG below 0.95 at the end of 2019. Figure 1 - Historian data showing a divergence in digester pressure level vs. radar level beginning on Dec. 25 2019 Grab samples taken at various digester depths confirmed the accuracy of the online density monitoring. 3 potential causes around the date of the density change were identified an investigated. Those potential causes were: - A polymer spill - An annual dairy shutdown - A filament bloom in the bioreactors The case study will detail how the cause was narrowed down to the filamentous bacteria Microthrix that thrives during the cold season. Microthrix mitigation strategies were developed, tested, and implemented. These included but are not limited to: - PAC dosing trial - Chlorination at various locations - Selection control o Swing zones o Internal recycle location o Scum removal improvements Figure 2 - This chart summarizes the key parameters during the initial troubleshooting period. The digester radar-pressure level is the sludge density indicator, and it shows that by late August 2020 Microthrix impact on the digesters had subsided. The most recent data will be included in the case study. RESULTS: With the mitigation strategies implemented on the liquid treatment side of the process, Microthrix continues to cause difficulties during the cold season. Microthrix thrives on grease and the grease flow to the plant has only increased since 2020. A change that improved primary scum removal ended up being the most effective mitigation. The County is also working on rehabilitating a grease digester that has been offline for 20 years to further limit the impact grease has on the process. The pump and piping modifications originally implemented on one primary digester have continued to perform well and are now being implemented on the 2nd primary digester. DISCSSION/CONCLUSIONS: Filamentous bacteria such as Microthrix and Nocardia can be a perennial ailment on the liquid treatment side at wastewater plants that can also have downstream effects on the solids treatment side of the process. This case study will conclude with the author's lessons learned from a process mechanical perspective, and the co-authors lessons learned from an operational perspective. Generally these include but are not limited to: - Microthrix: o Results from PAC trial o Results from chlorination trial o Results from selection changes - most effective o Generally Microthrix is hard to combat in greasy environments - Digester heating loops should be designed to covey gas to the maximum extent possible - Digester recirculation and mixing systems should react to changing sludge density.

This paper was presented at the WEF Residuals and Biosolids Conference, June 18-21, 2024.

SpeakerMaley, John

Presentation time

10:15:00

10:45:00

Session time

08:30:00

11:15:00

SessionTroubleshooting & Optimization

Session number26

Session locationOklahoma City Convention Center, Oklahoma City, Oklahoma

TopicAerobic Digestion, Biogas, Whole-plant impacts

Author(s)

Maley, John

Author(s)J. Maley1

Author affiliation(s)HDR Inc. 1;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Jun 2024

DOI10.2175/193864718825159473

Volume / Issue

Content sourceResiduals and Biosolids Conference

Word count9

Description: Being Good Neighbors: How Monitoring and Modeling Led to Plant Wide Odor Control...

Being Good Neighbors: How Monitoring and Modeling Led to Plant Wide Odor Control Improvements

Abstract

Prince William County Service Authority (PWCSA) owns and operates the H.L. Mooney Advanced Water Reclamation Facility (AWRF) which is located in a residential community with parks and a walking path at the property line. Odor control has been added and upgraded over the last 20 years at portions of the AWRF; however, PWCSA aims to further reduce odors. A design-build project is underway that will include odor control improvements. The project includes sampling and dispersion modeling odor sources, evaluating treatment technologies, and designing and constructing the chosen system. This paper will discuss the sampling, extensive dispersion modeling, and fence line goal development that led to the design and future construction of a 95,000 CFM centralized odor control facility

PWCSA owns and operates the H.L. Mooney AWRF which is located in a residential community. Odor control has been added and upgraded over the last 20 years at portions of the AWRF; however, PWCSA aims to further reduce odors. A design-build project is underway that will include odor control improvements. This paper will discuss the sampling, dispersion modeling, and fence line goal development that led to the design and future construction of a 95,000 CFM centralized odor control facility.

SpeakerKenel, Kelsey

Presentation time

15:30:00

15:50:00

Session time

15:30:00

17:00:00

SessionManaging the Third Effluent Part I

Session locationRoom N426b - Level 4

TopicIntermediate Level, Municipal Wastewater Treatment Design

Author(s)

Kenel, Kelsey

Author(s)K. Kenel 1; S. Spence 2 ; M. Welle 3; B. Balchunas 4; J. Maley 5; M.M. O'Shaughnessy 2;

Author affiliation(s)HDR 1; Prince William County Service Authority 2 ; HDR 3; HDR 4; HDR 5; 2;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2023

DOI10.2175/193864718825159037

Volume / Issue

Content sourceWEFTEC

Word count15

Biogas/RNG Project Lifecycle

Abstract

PROBLEM STATEMENT/PURPOSE: This paper and presentation will detail the typical lifecycle of a municipal RNG project from the facilities planning phase through post startup operation in order to inform those considering such a project. It will delve into the common key decisions that are made along the way as well as specific details about these types of projects. The lifecycle will be broken down into the following major phases: 1.Planning 2.Design 3.Construction 4.Operation Historically municipalities would choose to anaerobically digest their wastewater sludge to reduce the volume produced to lower hauling and landfill costs compared to other stabilization methods. The biogas produced would mostly be flared with some potentially beneficially used to heat the digestion process. Over time methods have evolved to get increasing higher value out of the biogas that would otherwise be flared. These include electrical power production, combined heat and power systems, and heat recovery steam generation to name a few. In recent years a more lucrative biogas use has grown out of the renewable fuel standard (RFS). Under the RFS gasoline and diesel producers and importers (obligated parties) are required to purchase a certain amount of renewable fuel every year to offset transportation related greenhouse gas emissions and limit reliance on foreign energy. This has driven the value of biogas (in the form of renewable natural gas or RNG for short) to higher than the equivalent amount of natural gas and therefore many municipalities considering upgrades to their biosolids processes today are including anaerobic digestion with a method of selling their biogas (Figure 1 - RIN prices by category over time). RNG value lies largely with the renewable identification number (RIN) trading that occurs between producers and obligated parties. Figure 1 - RIN prices by category over time. RNG PROJECT LIFECYCLE Experience from the following municipal biogas RNG projects will inform the project lifecycle insight provided in this presentation. These projects are in varying stages of the 4 main project phases outlined in this presentation. - Thereasa St. WRRF, Lincoln, NE - Columbia Blvd, WTP, Portland, OR - Papillion Creek WWTP, Omaha, NE - Piscataway WWTP, Accokeek, MD - Cedar Rapids WPCF, Cedar Rapids, IA - Des Moines STP, Des Moines, IA - Arlington WPCP, Arlington, VA PLANNING The first step in an RNG project lifecycle is in the facility planning phase. This phase is usually kicked off when a municipality is looking to either implement an overall biosolids process improvement or wants to beneficially use biogas from an existing digestion process. Biogas beneficial use options at this phase will typically include combined heat and power, electricity generation, thermal drying, and pipeline injection. In most cases if there is a natural gas utility or transportation end user located within a reasonable distance of the plant RNG production will win out over the other alternatives. The strongest argument for RNG is financial but it also has environmental and social advantages over the alternatives which will be detailed (Figure 2 - Example of greenhouse gas (GHG) emissions for design alternatives). When producing and selling RNG is identified as a feasible path forward the highest priority becomes reaching out to potential receivers; either a natural gas utility or a vehicle fleet operator. The receiver must both be receptive to accepting RNG and provide details that will guide the design. These details include gas quality requirements, interconnection design, custody transfer, site location, payment and funding split. DESIGN The next major phase of an RNG project is final design. During this phase many key decisions are made. Many RNG projects have very similar key design decision points. The following are some of the design decisions that will be discussed: - Should there be gas utilization options in addition to RNG (Figure 3) - Biogas design flow and peaking factors - Whether or not to upgrade peaks in biogas production - Should there be gas storage? - Levels of redundancy (flare, compression, upgrading, etc.) - CO2 removal technology and tail-gas treatment - Design H2S, VOC, and siloxane concentrations and how to treat. - Gas conveyance (wet vs. dry) to upgrading system. Other important design details that will be discussed are examples of process control description, commissioning plan, and performance testing plan development. Figure 3 - Example of a process with many gas utilization alternatives. CONSTRUCTION After design the next major phase is construction. During construction coordination with the gas receiving entity continues and this presentation will give examples of the ongoing coordination that can be expected (including potential involvement of a RIN broker). Figure 4 shows an example of initial RNG acceptance coordination with the gas utility during startup. The period of commissioning, functional testing and performance testing is the most operationally intensive phase of construction. This presentation will give examples of how to prepare for a successful commissioning phase that involves all stakeholders. Specific detail will focus on team collaboration and process driven decision making. Figure 4 - Example of RNG acceptance coordination with gas utility. OPERATION The last lifecycle phase that will be covered is operation of an RNG production system. It will give details on what to expect in terms of revenue generation, operation and maintenance, uptime, and potential contingency scenarios (down time). Figure 5 shows maintenance of one of the most common H2S removal technologies, iron sponge adsorption. Figure 5 - Photo of iron sponge H2S removal media change - Courtesy of MV Tech

This paper was presented at the WEF Residuals & Biosolids and Innovations in Treatment Technology Joint Conference, May 6-9, 2025.

SpeakerMaley, John

Presentation time

11:15:00

11:35:00

Session time

10:15:00

11:45:00

SessionAdvancing Biogas and RNG: Innovations and Regulatory Challenges

Session number26

Session locationBaltimore Convention Center, Baltimore, Maryland, USA

TopicAerobic Digestion, Alternative Delivery Systems (Design-Build-Operate-Transfer), Biogas, Biogas To Biomethane, Biogas Utilization, Greenhouse Gases, Heat recovery, Renewable Natural Gas