Parmenter, Adam

Adam is a Senior Professional Associate with 20-years of experience at HDR. His biosolids expertise comes from design, construction, operation,...

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About Parmenter, Adam

Adam is a Senior Professional Associate with 20-years of experience at HDR. His biosolids expertise comes from design, construction, operation, troubleshooting, and condition assessments of biosolids processing facilities around the country.

Parmenter, Adam

Titles from this speaker

Centrifuge Operational Adjustments Result in Cost Saving Opportunities at NEORSD

Abstract

FINDINGS & OBJECTIVE Northeast Ohio Regional Sanitary District's (NEORSD's) nine (9) dewatering centrifuges can handle a surprisingly diverse array of operating conditions and are capable of significant operational cost savings. These are findings based on unique full-scale centrifuge tests performed at its Southerly Wastewater Treatment Center (WWTC). The tests were done to understand how the centrifuges will work as upstream process conditions are stressed including wet-weather events and hydraulicly overloaded primary sludge gravity thickeners (GVTs). INTRODUCTION | BACKGROUND Wet-weather events greatly impact sludge operations at the WWTC. Operators try to maintain a >5-foot sludge blanket in the GVTs for downstream sludge storage and centrifuge operation purposes. However, wet weather events flush thinner sludge through the process and can overload GVTs. NEORSD engineering and operations wanted to determine if a consistently thinner sludge into the dewatering centrifuges would have any negative impacts to its operations. Allowing thinner sludge blankets at the primary clarifiers and GVTs would reduce hydraulic overloading incidents during wet-weather events. The goal of the testing was to simulate a lower solids sludge concentration (thin sludge) into a centrifuge and determine any needed setpoint changes for successful performance. A secondary goal of the testing was to optimize centrifuge operation including polymer dose and energy use. Six different tests were performed. The first two tests evaluated the impact of feeding low solid concentration sludge. Four additional tests were performed to optimize polymer use, recognize energy savings, and abilities to control percent cake total solids. The testing revealed that thin sludge down at least 0.8% can be successfully fed to dewatering without negative impacts to polymer, centrate quality, or cake total solids. In addition, at much as a 30% polymer dose savings could be recognized and electrical energy savings are possible. Process Flow Description The WWTC utilizes four (4) Sludge Storage Tanks to hold Primary Sludge (PS) and Excess Activated Sludge (EAS) prior to centrifuge dewatering and incineration. At the Sludge Storage Tank complex, three (3) Centrifuge Feed Pumps (CFPs) feed the sludge to the Renewable Energy Facility (REF) for centrifuge dewatering. The REF includes three (3) equipment trains, each consisting of three (3) centrifuges, design to operate at around 200 GPM each. The target minimum solids concentration of the centrifuge cake is 28%. The target for centrate capture rate is greater than 95%. Test Preparation A rigorous testing protocol was developed to create clarity in roles, responsibilities, sampling points, measurement locations, data recording. One unique aspect of the testing setup was how to introduce Non-Potable Water (NPW) into the centrifuge feed piping to simulate a desired thin sludge concentration. NPW introduction was made via a temporary piping system with clamp-on ultrasonic flow meter and globe valve for flow control. Polymer bench testing with feed sludge was performed to observe if any deleterious polymer consumption impacts were created with the introduction of NPW. FINDINGS OF SIGNIFICANCE Test #1 - Thin Sludge, Low Solids Loading Rate Testing included introduction of NPW into the feed sludge pipeline for a single centrifuge. The goal of this test was to confirm stable operations of thinned sludge, as low as 0.5% TS, down to the machine's minimum rated total solids throughput of 1,500 lbs/hr and determine if parameters need to be adjusted for stable operations. Operation of the centrifuge was unaffected with the NPW addition, feed sludge as low as 0.84% total solids, and machine loading rate to its minimum of 1,500 lbs/hr. Centrifuge performance maintained its Torque, Centrate Quality, and Cake Total Solids. No operational impacts were identified. These results add confidence to NEORSD's operations group that the dewatering system will handle thin sludge if it is encountered in the future due to wet weather events. Test #2 - Thin Sludge and High Solids Loading The goal of this test was to confirm stable operations of thinned sludge, with a 350 GPM hydraulic limitation, up to the machine's maximum rated total solids throughput of 4,500 lbs/hr and determine if parameters need to be adjusted for stable operations. Feed sludge total solids were sampled and tested prior to the beginning of the test. The sludge flow rate was then increased to the calculated maximum solids loading rate of 4,500 lbs/hr. Once stable centrifuge operation was confirmed at 4,500 lbs/hr, NPW water was introduced to achieve thinned sludge without exceeding the centrifuge maximum hydraulic loading rate. Operation of the centrifuge was unaffected with the NPW addition, operating at the maximum hydraulic feed rate of 350 GPM, and with a thinned sludge down to as low as 1.79% TS during this test. Centrifuge performance maintained its Torque, Centrate Quality, and Cake Total Solids. No operational impacts were identified. These results confirm the solids capacity of the machine, the machine's ability to run at the hydraulic maximum, and ability to handle changing conditions without impacting normal operation parameters. Test #3 - Polymer Reduction Optimization Polymer optimization is the process of adjusting the polymer dose without losing performance in cake total solids or centrate capture rate. The goal of this test was to determine if lower polymer dosing rates can produce similar centrifuge performance. The result of lower polymer dose at similar performance is a cost saving measure that NEORSD may consider in future operations. The process of reducing polymer dose on an existing centrifuge is an operator adjustment via the SCADA system. During the testing, polymer was reduced to as low as 5.2 lbs/dt active polymer dose while still achieving a 95% solids recover/capture rate. This represents a 30% polymer savings potential versus current full-scale operations and an opportunity for significant cost savings with limited impacts to operations. Test #4 - Increasing Centrifuge Bowl Speed for Cake Solids Control The centrifuge's normal operating speed was increased from the current setpoint of 2300 RPM up to 2500 RPM to observe any operational change or improvements. The centrifuge manufacturer's O&M Manual indicated that 2500 RPM is the recommended rotational bowl speed; higher than the 2300 RPM that the bowls have operated since they were commissioned. During testing, centrifuge operations were basically unchanged while the bowl speed was increased. The higher bowl did not reduce flocculation stabilization, nor did it provide any observable value to operations. The downside of operating at the higher bowl speed is the energy cost, increasing wear on the bearings, and increasing potential for vibration issues. Test #5 - Centrifuge Lower Bowl Speed The centrifuge's normal operating speed was decreased from the current setpoint of 2300 RPM to as low as 2000 RPM to observe operational changes or improvements. The speed at which cake total solids concentration decrease was at 2000 RPM. This offers and opportunity for energy savings if the bowl speed is reduced permanently. Data collected during the testing showed an 11-amp energy savings. In addition, if a lower bowl speed can be implemented less wear-and-tear on the centrifuge bearings and lower vibration offers an opportunity to extend equipment life. Test #6 - Centrifuge Lower Torque This test was performed to observe how a lower torque setting will decrease cake total solids. This could be used as a tool by operators if feed solids are too dry for the incinerator. Centrifuge torque was reduced from its current setpoint of 50% down to as low as 42% with performance impacts. Lowering the torque setpoint created a wetter cake as predicted. Operations may use this adjustment to manage their cake total solids going to the incinerator, especially if the solids are dry and the incinerator is overheated. DISCUSSION & RESULTS Six different centrifuge tests were performed, each of them provided additional insight to NEORSD operations staff. The robustness of the centrifuge operating system was confirmed with differing sludge concentrations and throughputs to handle future scenarios. Significant cost savings potentials and operational flexibility with polymer use and operating parameters were also confirmed. NEORSD is continuing to improve their processes with the knowledge of full-scale testing. The testing effort allows improvements to their system by providing reliable, efficient, and robust solids processing. Attendees of this presentation can gain detailed knowledge of centrifuge operation and understanding optimization opportunities at their facilities.

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

SpeakerParmenter, Adam

Presentation time

16:05:00

16:25:00

Session time

13:30:00

16:45:00

SessionCase Studies for Optimizing THP, Dewatering, and Digestion

Session number7

Session locationBaltimore Convention Center, Baltimore, Maryland, USA

TopicAnaerobic Digestion, Biosolids, Dewatering Optimization, Energy and Carbon Neutrality, fugitive methane emission, Full-scale Optimization, Greenhouse Gases, Mesophilic Anaerobic Digestion, Odor/Air Emissions, Operations And Maintenance, Process modeling, Reliability, Sludge Digestion, THP, THP, CAMBI

Author(s)

Parmenter, Adam, Merchant-Wells, Nicholas

Author(s)A. Parmenter1, N. Merchant-Wells2

Author affiliation(s)HDR, 1Northeast Ohio Regional Sewer District, 2

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2025

DOI10.2175/193864718825159779

Volume / Issue

Content sourceResiduals and Biosolids Conference

Word count11

Flux Capacity: Screw Press Sizing Of The Future

Abstract

The most common technologies for sludge dewatering in wastewater treatment plants include belt filter presses, centrifuges, and screw presses, with the latter known for their significant advantages in low power consumption and high efficiency during the dewatering process. Various manufacturers supply screw presses to wastewater treatment plants, offering pilot testing to assess the performance, throughput capability, and feasibility of dewatering units in diverse practical and controlled environments. However, unlike centrifuges and belt filter presses, the capability to compare the throughput of screw presses throughput between manufacturers is lesser known. While the throughput equipment capacity comparisons for centrifuges and belt filter presses are well-established through G-Volumes and filter areas, respectively, a similar standardization for screw presses is not widely recognized. The Tres Rios Water Reclamation Facility, owned by The Pima County Regional Wastewater Reclamation Department, serves as the centralized sludge handling and solids treatment system for the entire county, offering a treatment capacity of 50 MGD and over 180 WTPD of solid dewatering. Currently utilizing three centrifuges for sludge dewatering, the facility faces challenges related to high polymer and power usage. In response, as part of the county's transition from achieving Class B to Class A biosolids, a new dewatering facility employing screw presses was proposed aimed to reduce energy costs and enhance the efficiency and reliability of the dewatering process, ultimately supplying future solar dryers. During the summer and fall of 2023, three screw press pilots, and one volute press pilot were conducted in collaboration with various equipment manufacturers. The primary objective of these pilots was to verify and evaluate dewatering performance and ultimate equipment selection using digested sludge from the Tres Rios WRF. A new approach was implemented when comparing pilot test results relative to full-scale equipment selection. The approach is to compare 'flux' of each machine at its best performance point. The machine's flux is the rate of liquid and/or solids flow rate per surface area of the machine. In doing this analysis, full-scale equipment is sized relative to the pilot test's best performance at a proven flux rate. An equal flux rate from pilot to full-scale equipment will help ensure similar and expected performance at full-scale operation. To compare performance of the screw press units during the pilot testing, liquid and solids flux rates were calculated for each manufacturer. The liquid flux rate results of the three screw press manufacturers are shown in Table 1. The volute press manufacturer was not included in the evaluation due to the poor pilot test results compared with the other manufacturers. The lower flux rate, indicative of a higher dewatering capability, signifies superior dewatering through an extended residence. Manufacturer 2 and 3 out-performed Manufacturer 1 by providing higher filtration area. Manufacturer 1 was not recommended for further consideration due to small full-scale equipment size options, resulting in the preferred maximum liquid flux rate of 0.31 gpm/sf for best performance. The results from the pilot testing aided in identifying the required flux rate achieve best performance, and ultimately confirms full-scale equipment sizing for a range of operating conditions. Table 2 shows that both manufacturers required five installed units dewater the design load, and a throughput derating of up to 75% is needed compared with the listed manufacturer nameplate. In contrast to using screw press volume, relying on manufacturer recommendations, or arbitrary derating of equipment as a metric for performance comparison among different manufacturers, the presentation will present findings showing that flux rate calculation during pilot units provides fair and more realistic results. Larger screw presses are noted to lose efficiency as the ratio of surface area to volume decreases with the growth in diameter and length of the screw. This claim can be better studied with a flux rate that remains constant regardless of the equipment size due to the solids retention time being equal, which this pilot study investigated. Attendees of this presentation will gain valuable insights into the comparative performance of screw presses from different manufacturers post-pilot testing. This knowledge will aid in establishing informed selection criteria for optimizing dewatering solutions in wastewater treatment plants.

The paper evaluates screw presses for sludge dewatering at the Tres Rios WRF. Four pilot tests in 2023 assessed different manufacturers using "flux"—the liquid/solids flow rate per unit surface area. Superior dewatering occurred at lower flux rates, indicating higher capabilities with extended residence time. The study concluded that liquid flux rate is a more accurate performance metric than manufacturer recommendations or arbitrary derating.

SpeakerFraijo, Alejandra

Presentation time

09:00:00

09:20:00

Session time

08:30:00

10:00:00

SessionThickening and Dewatering: Design Considerations

Session number301

Session locationRoom 354

TopicBiosolids and Residuals

Author(s)

Fraijo, Alejandra, Parmenter, Adam, Prevatt, Jeff

Author(s)A. Fraijo1, A. Parmenter2, J. Prevatt3

Author affiliation(s)1HDR Engineering, AZ, 2HDR, MN, 3PIMA COUNTY WASTEWATER, AZ

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2024

DOI10.2175/193864718825159520

Volume / Issue

Content sourceWEFTEC

Word count9

Pima's Plural Purposes for PONDUS

Abstract

LEARNING OBJECTIVE: Pima County's Tres Rios Water Reclamation Facility (TRWRF) recently evaluated process benefits and cost effectiveness of including PONDUS into their process, ultimately deciding to proceed with the design and construction based on several advantages. Participants of this presentation will learn the findings of the evaluation including present-value and life-cycle costs of implementing the new process, positive impacts to digestion capacity, biogas production and sales, and solids loading rates at dewatering and the future Class A biosolids solar dryer system. INTRODUCTION | BACKGROUND The TRWRF, owned by The Pima County Regional Wastewater Reclamation Department (County), serves as the centralized solids handling and treatment system for the entire county, offering a treatment capacity of 50 MGD. The TRWRF currently produces approximately 180 wet tons per day (WTPD) of Class B biosolids at approximately 18-20% total solids content. With the goals to reduce TRWRF energy requirements, lower solids disposal costs, and address future biosolids disposal regulations the County is planning for a solar dryer to produce Class A biosolids. An opportunity to maximize these goals is to introduce a hydrolysis process that can further reduce biosolids volumes and reduce the size of the solar dryer. In addition, a hydrolysis process would create additional needed digester capacity, increase biogas production, and create a dryer cake going into the solar dryer amongst other potential TRWRF benefits. The thermochemical hydrolysis process PONDUS was specifically targeted based on limited additional operational requirements and small footprint. METHODOLOGY The PONDUS system is a thermal/alkaline hydrolysis process designed for breaking down bacteria cell walls from thickened waste activated sludge (TWAS). The cell membrane breakdown releases organic acids into the downstream anaerobic digester that ultimately feed methanogens to produce greater methane production. Note that this process is not designed to treat primary sludge (PS) that also goes into the anaerobic digester, as that material does not contain a high fraction of bacteria for lysing. The process combines the TWAS at around 6% TS with caustic soda (NaOH) to a pH of approximately 10. The TWAS is then heated to between 140o F and 160o F for 30 minutes for the reaction to take place. The system is offered from a single manufacturer Centrisys-CNP as a package which includes the chemical storage and delivery system, TWAS recirculation pumping and heat exchange, and instrumentation and controls. A preliminary mass balance and process flow diagram of the system is represented in Figure 1 below. Figure 1 PONDUS Mass Balance and Process Flow Diagram Potential Benefits The PONDUS system creates operational savings with increased biogas production and reduced total solids needing to be processed, which is the primary driver for using the system. Other benefits of PONDUS include the following: - Lower Viscosity: The hydrolyzed sludge reduces the digester feed sludge viscosity by over 50%. The biosolids can be pumped, mixed, and heated with lower energy requirements and allows for a higher TS loading rate into the digesters. A higher loading rate allows for reduced total digester volume required to meet minimum solids retention times (15 days), greater storage capacity, and allows greater flexibility for a digester to be taken offline. Additionally, the higher total solids feed rate to the digesters reduces the water heating requirement, and therefore reduces natural gas heating water needs on the digester boilers at an anticipated savings of approximately $80,000/year. The lower digester viscosity could also reduce energy demands on pumping and mixing systems. - Achieving Class A Biosolids: The PONDUS thermal/alkaline hydrolysis process will result in higher volatile destruction, resulting in more biogas and less sludge to manage. A secondary benefit to the volatile solids destruction is a further reduction in fecal coliform, salmonella, enteric viruses, and viable helminth ova in the biosolids exiting digestion. This further reduction will increase the ability for the Solar Dryer to achieve Class A biosolids under the 503 Regulations at a lower total solids concentration. The lower total solids exiting the future solar dryer will reduce dust production and create a better working environment. - Total Solids Cake Dryness: With a breakdown and reduction in volatile solids, a dryer dewatered cake total solids concentration can be assumed. Manufacturer data and an independent study of 17 different samples shows that the total solids of cake will increase between 3% and 6%. The independent study data from KBKopp Sludge Analytics is provided in Table 1. - Polymer Demand: Manufacturer data shows that a 20% decrease in polymer can be expected when using PONDUS. Table 1 implies that primary sludge subjected to PONDUS has a marginal polymer demand increase. Given the high WAS:PS fraction at TRWRF, and the nature of PONDUS breaking down volatile solids it can be assumed polymer demand will be reduced. - Dewatered/Dried Biosolids Odors: The PONDUS biosolids cake is reported to have a lower odor concentration than traditional anaerobically digested sludge. This is due to the greater volatile solids reduction. The benefits include reduced odor concentrations to treat, increased biofilter bed-life, and reduced risk of odor complaints. Operations and Maintenance Considerations The largest direct operational costs of the PONDUS system is caustic soda consumption. Daily caustic soda use is expected to be 155 gallons resulting as high as $280,000 yearly cost. Heating the TWAS in the PONDUS Lysing Reactor adds minimal cost from an overall perspective, as the heat energy required to heat the TWAS from 140o F to 160o F is eventually used in the downstream anaerobic digester process. Table 1 PONDUS Independent Study: Sludge Effect on PONDUS (Dr Julia Kopp, 2022) DISCUSSION Revised Mass Balance Estimate With a PONDUS system, the increase in biogas is expected to be 22% higher than the existing TRWRF anaerobic digester system. The daily biogas production would increase by 91 million BTU (MMBTU). The sell back value of those 91 MMBTU, with the EPA value of 11.7 Renewable Identification Numbers (RINs) per MMBTU and at $2.30 per RIN results in an additional $2,463 in biogas sales per day, or $899,000 in biogas sale per year. The expected increase in biogas production also reduces the total solids needing to be dewatered, dried through the solar dryer, and hauled away. Coupled with an expected dryer cake, the current 180 WTPD of solids through the existing plant processes ending at dewatering would be reduced to 124 WTPD of solids after dewatering. This is a 53 WTPD total solids reduction, or about two hauling trucks per day of reduction. At current costs per wet ton disposal of $27.20, this results in a potential savings of $526,000 per year. Implementation Risk The PONDUS process includes risks that must be recognized and managed to the extent possible. Key implementation risks include the following: - Full-Scale Implementation: The primary risk of the process is that PONDUS has limited installations to use as proofs and lessons learned. There are over 20 installations in Germany, with one fully operational facility in the US. While the thermal/alkaline process is well understood and proven, the unknowns of full-scale may reduce the estimated savings. To mitigate against this uncertainty, the County and its design team conduct a site visits and spend time at the existing US facility to help understand full-scale operations, maintenance, and data comprehension of the process. - The lysing process creates an opportunity for a lower centrate/pressate capture rate of solids downstream of dewatering due to the high volatile solids destruction rate. This can be addressed by using total solids metering on centrate/pressate to identify and fix under performance. - Increased nutrient ratios within the centrate/pressate from PONDUS is expected. Table 1 shows a 28% chemical oxygen demand (COD) increase, an 18% ammonia increase, and a 26% orthophosphate increase. Updated BIOWIN modeling may be necessary to to confirm impacts on centrate/pressate deammonifiaction and secondary treatment processes. RESULTS & STATUS Installation of PONDUS is anticipated to create an operational savings of $1,060,000 per year and a system payback in under 10-years. The County determined these savings opportunities along with added digester capacity and future solar dryer benefits justifies continuing with the project. The new PONDUS facility is now in design at TRWRF with a construction start date of 2025.

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

SpeakerParmenter, Adam

Presentation time

08:30:00

08:50:00

Session time

08:30:00

11:45:00

SessionInnovations in Sludge Management: Enhancing Anaerobic Digestion and Phosphorus Control

Session number10

Session locationBaltimore Convention Center, Baltimore, Maryland, USA

TopicAerobic Digestion, Anaerobic Digestion, Biogas Utilization, Biosolids, Biosolids treatment, Class A, Dewaterability, Phosphorus recovery, struvite, electrochemical, Pilot Scale, Process Intensification, Resource Recovery, Solids Pre-Treatment, Sustainability, thermophilic, THP, CAMBI

Author(s)

Parmenter, Adam, Prevatt, Jeff

Author(s)A. Parmenter1, J. Prevatt2

Author affiliation(s)HDR, 1Pima County RWRD, 2

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2025

DOI10.2175/193864718825159757

Volume / Issue

Content sourceResiduals and Biosolids Conference

Word count6

Description: Successful Startup, Commissioning, and Operation of a New Regional Biosolids Drying...

Successful Startup, Commissioning, and Operation of a New Regional Biosolids Drying Facility

Abstract

Objectives 1. Present lessons learned and findings from the startup and commissioning of a new biosolids facility with thickening, dewatering, and drying. 2. Discuss challenges and successes with training an operations team that is transitioning from hauling sludge to a third part compost facility to operating a full biosolids facility with thickening, dewatering, and drying. Status The City of Hickory (City) in Catawba County, North Carolina is currently constructing a new biosolids handling facility. Substantial completion is anticipated to be reached in the first quarter of 2025. Startup and commissioning of equipment is currently underway, and operations and maintenance staff trainings are being completed. The project team is collaborating with the operations team to develop standard operating procedures. Methodology Design The City is currently in a consortium of wastewater utilities that collectively own a regional solids management facility (RSMF) and contract the operations to a third-party. This facility receives solids from the members and produces Class A compost that is marketed and distributed as a fertilizer. A condition assessment in 2019 indicated that the entire facility was past or approaching the end of its useful life. The key recommendation of this effort was to construct new solids handling facilities at the City of Hickory's Henry Fork Wastewater Treatment Facility (HFWWTF). This recommendation was primarily due to the relatively large cost to replace equipment at the RSMF and the difficulty in beneficially using the composted biosolids product. After a technology review, site visits, and a request for proposal process, the City selected low-temperature, indirect drying for the production of Class A Biosolids at a throughput rate of 12 dry tons per day. HFWWTF was reliant on the existing RSMF facility for all sludge management, including thickening and dewatering. Therefore, the new Solids Handling Facility included the following additional infrastructure: - Solids Receiving Station -receiving station for solids trucked in from off-site facilities. - Gravity Belt Thickening -thickening for the HFWWTF WAS to reduce volume prior to dewatering. - Thickened Solids Holding -utilization of the existing Sludge Holding Tanks to provide flow equalization and temporary storage upstream of dewatering. - Belt Filter Press Dewatering - new dewatering equipment to prepare solids for drying. - Cake Storage -- new cake storage silo with live bottom to provide mass equalization and temporary storage upstream of drying. - Dried Product Storage - outdoor storage for dried biosolids product. - Odor Control - control odor infrastructure to manage odorous gasses from new infrastructure and processes. - Bulk Chemical Storage Facility -- store bulk chemicals for use in the thickening, dewatering, and odor control processes. As a regional facility operating at a wastewater treatment plant, process flows vary in their source, quality, and concentration. HFWWTF produces both primary solids and waste activated sludge (WAS). Other consortium members deliver thickened WAS (TWAS) with or without a primary solids component. Table 1 presents a summary of the major contributors and their daily average and maximum contributions (HDR, 2020). These are daily values and do not reflect actual hauling schedules. Some utilities haul weekly, while others haul monthly or less. This varying pattern of solids, sources, and loadings presents a challenge for polymer and feed rate optimization. During startup, standard operating procedures and tracking logs are being developed to allow operators to identify and maintain an optimized performance with a variety of different sludge characteristics. Startup and Training Due to the sequential and interconnected nature of the process flow and the lack of existing biosolids infrastructure, startup requires careful planning to ensure success. Each upstream process must operate in specific parameters prior to startup of the next process (i.e. the dryer cannot operate with cake lower than 16% solids). Process control checkpoints have been established to ensure process flow is available and adequate when required. Close coordination between all parties, Owner, Engineer, Contractor, and Manufacturer coordination has been and will remain critical during the startup and commissioning period. Operator training is also key to the successful completion of the project. HFWWTF staff do not typically operate or maintain solids handling equipment, therefore additional trainings are being scheduled outside of the traditional manufacturer provided sessions. These include overall systems trainings, site walkthroughs, and shadowing. Additionally, standard operating procedure documentation and tools are being developed to assist operation staff. This includes a comprehensive biosolids operations and maintenance manual providing a single reference point for the entire system. Findings Startup of the biosolids handling facility is currently ongoing. The ultimate focus of the paper will be results, conclusions, and lessons learned from this process. Initial findings point towards the following lessons learned: - Reliance on contactor scheduling accuracy and introducing backup plans for missed schedules - Startup of facilities requires precise coordination between all parties within the construction process - Process control milestones are necessary to ensure all equipment is commissioned with appropriate process flow prior to starting up equipment. - Process control milestones cannot exist in a vacuum and must be coordinated with the contractor's schedule to ensure the correct critical path is identified - Holistic system training is beneficial to operators and maintenance staff who may be experiencing new types of equipment - Creation of standard operating procedures that capitalizes on commissioning lessons-learned - How to continue efficient operations and continuous optimization of the system following startup, after the contractor and manufacturers are gone As startup and process optimization continue additional findings, including quantitative data, will be documented and shared. Significance of the Project As populations continue to increase, biosolids disposal needs will become more important for urban and rural centers alike. This not only drives the need for new equipment, but also the need to regionalize biosolids handling operations, either in a consortium or within a single utility. While beneficial, regionalization also introduces operational challenges with members providing sludge of varying quality and quantities. Coupled with the introduction of new equipment, startup, commissioning, and training is a vital process to ensure a successful transition from construction to operation. This transition increases process optimization, ultimately saving rate payers money through time, energy, and material savings. This project represents an example of a holistic approach to the startup and training period. Whole system overview trainings and standard operating procedure documentation are coupled with manufacturer provided trainings to jump start an optimized process and lead to a culture of continuous process optimization. While sometimes an afterthought, the startup and training process is critical to the overall success of a project.

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

SpeakerHeringer, Nelson

Presentation time

11:25:00

11:45:00

Session time

10:45:00

11:45:00

SessionExploring Pathways to Dried Biosolids

Session number3

Session locationBaltimore Convention Center, Baltimore, Maryland, USA

TopicBiosolids, Biosolids treatment, Class A, Constructed Wetland, Drying, Innovative Technology, THP, CAMBI, Training

Author(s)

Heringer, Nelson, Parmenter, Adam, Cox, David

Author(s)N. Heringer1, A. Parmenter1, D. Cox2

Author affiliation(s)HDR, 1HDR, 1City of Hickory, 2

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2025

DOI10.2175/193864718825159772

Volume / Issue

Content sourceResiduals and Biosolids Conference

Word count13

Description: The Results of Replacing a Class A Biosolids Stabilization Technology to Gain...

The Results of Replacing a Class A Biosolids Stabilization Technology to Gain Capacity and Save Money

Abstract

INTRODUCTION Due to historical and continued population growth, the Town of Erie Colorado's North Water Reclamation Facility (NWRF) needed to expand. The NWRF's existing solids treatment process utilized an alkaline biosolids stabilization process to achieve Class A cake. Frequent shutdowns of the dewatering system occurred due to significant scaling in its screw press, caused by the high dosage of lime. Acid addition was consequently introduced as a permanent solution to reduce scaling, but as a result, the stabilized solids did not meet Class A fecal coliform reduction requirements. Due to expansion needs and the current system issues, a new or greatly modified system was required. The Town became interested in evaluating a new solids processing system that would both meet the requirements of the desired Class A end-product, as well as reduce the total annual operating and maintenance costs. HDR was tasked with a comprehensive alternatives evaluation for several biosolids stabilization technologies to determine which option would best suit the Town. The evaluation included establishing design conditions, analyzing the existing system's capacity, performing a preliminary screening of all alternatives, conducting a non-economic evaluation for the narrowed alternatives, and developing an economic evaluation including capital and operation and maintenance costs. This approach incorporated both monetary and non-monetary considerations to ensure that the selected technology would meet the Town's short-term and long-term interests. APPROACH The initial step was to compare the capacity of the existing biosolids handling system against the projected 10- and 20-year solids flows and loads, and determine the scope of expansion required to keep the existing system in operation. The next step in the evaluation process was to perform a screening level alternatives analysis for other biosolids stabilization technologies. Several considerations were included in the analysis including the number of installations of each technology within the United States, feasibility of construction, extensive annual costs for operation or maintenance, and process safety. After completing the preliminary screening of biosolids stabilization alternatives, HDR and the Town eliminated multiple technologies from further consideration. The following stabilization systems were shortlisted for further evaluation: - Alkaline Biosolids Stabilization: Existing System Expansion - Autothermal Thermophilic Aerobic Digestion (ATAD) - BCR Neutralizer System The first alternative, which is to expand the existing lime stabilization system, assumed no changes to the plant's current biosolids stabilization process other than increased capacity. The second alternative, Autothermal thermophilic aerobic digestion (ATAD), examined changing the process to a two-step aerobic digestion system patented by Thermal Process Systems (TPS) that utilizes high temperatures to trigger microbial activity by high carbon consumption thermophiles. The last alternative, the BCR Neutralizer system, is a process in which sodium chlorite and sulfuric acid are combined to make chlorine dioxide, which is then added to thickened WAS. It is a batch process rather than a continuous flow process, and it uses three additional chemicals to obtain Class A biosolids: sodium nitrate, ferric sulfate, and sodium hydroxide. The non-economic evaluation played a key role in the selection process. The non-economic factors included: - Operator Attention - Operator Familiarity - Maintenance Requirements/Complexity - Flexibility to meet Future Flows and Loads - Footprint - Implementation - Redundancy - Sustainability - Safety The last step in further evaluating the three alternatives was to conduct a monetary comparative analysis by developing the opinion of probable construction costs and a net present value (NPV) analysis using labor, energy, and chemical costs for a 10-year and 20-year evaluation. RESULTS The non-economic evaluation demonstrated that the ATAD alternative was preferred to the BCR Neutralizer alternative following the non-economic evaluation. After operating a chemical lime system for biosolids stabilization and handling several operational and maintenance-related difficulties associated with it, the Town favored a treatment process that did not require heavy chemical use. Additionally, the Town preferred an alternative that would be easily implemented within the plant's existing process, and that would sustainably and reliably produce a desirable biosolids end-product, so that they could reduce their dependence on third-party hauling companies. The figure below shows ATAD alternative as the favorable stabilization process versus the BCR Neutralizer. Figure 1: Non-Economic Evaluation of Narrowed Alternatives (Town of Erie NWRF Expansion Preliminary Design Report, HDR, 2019) The economic evaluation showed that the ATAD alternative was twice the capital cost of the other two alternatives, however, after review of the 10 and 20 year net present values, the ATAD alternative was the most favorable. Table 1 below provides a summary of those costs. Table 1: NPV Analysis for Keep Existing and ATAD Alternatives (Town of Erie NWRF Expansion Master Plan, HDR, 2019) Construction started towards the end of 2020 and the ATAD process was in operation by the start of 2023. The biosolids system is currently processing an average of 2800 PPD. With a design capacity of 11,700 PPD, the treatment system will have capacity to meet future growth. By year end of 2023, the new ATAD process has provided annual cost savings to the Town including a reduction in chemical cost by $75,000, reduction in hauling costs by $100,000, 10% reduction in electrical costs and $40,000 reduction in gas usage compared to previous years using the existing lime stabilization system. CONCLUSION After the evaluation was completed, the ATAD alternative was selected by both non-economic and economic selection criteria. The selection would provide the Town with a more sustainable biosolids stabilization process and the best value given review of the NPV analysis. As a result of this decision, design and construction of a new ATAD solids treatment facility was built. The Town is currently producing Class A Biosolids consistently. Actual cost savings have been apparent compared to the existing system, with first year annual cost savings equaling nearly a quarter million dollars. The outcome of this analysis highlights the importance of reviewing the big picture and not just the initial capital cost for selecting a biosolids stabilization process. This approach can be implemented for facilities looking to improve their solids handling system by applying a similar evaluation process to ultimately achieve their goals.

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

SpeakerParmenter, Adam

Presentation time

10:45:00

11:15:00

Session time

08:30:00

11:15:00

SessionProgram Drivers: Economics, Regulatory, and Market Considerations

Session number24

Session locationOklahoma City Convention Center, Oklahoma City, Oklahoma

Topicbiological stabilization, Biosolids Management Planning, Class A biosolids

Author(s)

Parmenter, Adam

Author(s)A. Parmenter1, G. MacPhee1

Author affiliation(s)HDR 1; HDR 1;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Jun 2024

DOI10.2175/193864718825159462

Volume / Issue

Content sourceResiduals and Biosolids Conference

Word count17

Base text size -

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