Borgmann, Ruth

Ruth Borgmann is a Senior Associate at Hazen and Sawyer in the wastewater process mechanical group with a focus on biosolids management and design. She received her BS in Environmental Engineering from NC State University in 2012 and is a licensed professional engineer in North and South Carolina. In her free time, she enjoys walking her dogs, hiking and knitting.

Titles from this speaker

Description: Master Planning for Near-Term and Long-Term Residuals Management for a Multi-WRRF...

Master Planning for Near-Term and Long-Term Residuals Management for a Multi-WRRF Utility

Abstract

Background Renewable Water Resources (ReWa) operates nine (9) wastewater resource recovery facilities (WRRFs) in the upstate of South Carolina. Four facilities stabilize biosolids to achieve Class B pathogen reduction through anaerobic digestion. One (1) WRRF employs aerobic digestion for stabilization, and the four (4) remaining facilities transfer biosolids to other WRRFs for stabilization. Four facilities have dewatering equipment onsite to allow for dewatering and dewatered cake disposal at the landfill, but the remainder of the WRRFs must transfer liquid solids to these facilities for dewatering prior to landfilling. The primary method of biosolids management is land application of thickened, liquid Class B biosolids. The land applied solids range from 2% to 6% total solids. ReWa has over 10,900 acres of farmland permitted to receive biosolids. The contingency biosolids management method is dewatering and landfill disposal. Hazen and Sawyer was retained by ReWa to provide Biosolids Master Planning Services to develop near-term and long-term recommendations for a more flexible and sustainable biosolids management program. Evaluation of centralization of biosolids management was also considered. Development of the master plan will be primary focus of the presentation. ...Near-Term Evaluation Near-term solutions which could be implemented quickly and alleviate treatment and disposal constraints were evaluated. Low-capital intensity solutions were prioritized. Near-term solutions recommended for implementation included the following: - Procurement of a mobile belt filter press (BFP) to create operator flexibility at WRRFs with no onsite dewatering capabilities or supplement dewatering capabilities at facilities where dewatering infrastructure already exists. - Transition to a dewatered cake Class B land application program to provide management flexibility and to reduce volume of biosolids managed using dewatering infrastructure already present at selected facilities. - Construction of dewatered cake storage to create additional storage during periods of inclement weather when sludge storage tanks are full and biosolids cannot be land applied Implementation of each near-term solution was considered at appropriate WRRFs across ReWa's system. Benefits of a dewatered cake land application program include: - Improved logistics with fewer transport activities to move same dry mass of material - Reduced liability and risk exposure with fewer trucks on the road - Reduced GHG emissions from reduced transit mileage requirement - Reduced need for CDL drivers due to approximately four-fold reduction in number of trips - System wide O&M cost benefit Construction of a 45,000 sf regional covered storage facility at a centrally-located WRRF was also recommended. The WRRF was selected as the location for the regional cake storage facility due to the available land onsite, remote location and proximity to permitted land application fields. The 45,000 sf regional covered storage facility would provide approximately 25 days of storage systemwide based on 2020 sludge production and flow estimates and is consistent with what other Carolina utilities with robust dewatered cake land application programs have installed. Regulatory and Market Analysis In preparation for the facility making a Class B dewatered cake product in the near-term and potentially a Class A product in the long-term, a regulatory review, benchmarking with other SC utilities and a Class A market analysis was completed. Results of the market analysis were used to shape discussions regarding potential Class A alternatives investigated. It was recommended that for long-term planning, solids reduction in product mass and/or volume be strongly considered to reduce downstream management challenges either with land application or alternative management options. Long-term planning should also include trigger points that would dictate a change in biosolids management pathway to address a changing regulatory environment or sustainability initiative for ReWa. Figure 1 details a potential long-term biosolids management roadmap with regulatory trigger points for ReWa. Long-Term Evaluation Long-term improvement opportunities were based on evaluating advanced processing technologies, and beneficial use of digester gas. Thermal hydrolysis (THP), Lystek, CleanB and thermal drying were the advanced processing technologies considered at various facilities across the system; a site layout was developed for each advanced processing technology for facility buildout. In addition to these decentralized alternatives, several system wide alternatives were also evaluated to consider opportunities for centralization. In the long-term, it was recommended that ReWa transition to a thermally dried product to reduce volume of material handled and increase end use outlets. A centralized drying facility was recommended to take advantage of economies of scale and reduce staffing requirements across facilities. Locating a regional dryer facility at ReWa's largest facility was recommended. This facility has the largest amount of available digester gas to supplement thermal dryer fuel demands. There are several types of thermal dryers which should be investigated more thoroughly once ReWa is ready to progress with this phase of the biosolids management program. For the purposes of CIP development and planning, a dryer with the capacity to handle solids from the three largest WRRFs on an annual average basis through 2040 was assumed. Based on the current flow projections, maximum month solids loading and greater would need to be handled by a secondary outlet after 2034. This secondary outlet could either be through the dewatered cake land application program or installation of a second thermal dryer. By installing a thermal dryer to manage solids from the three largest facilities in 2030, ReWa could manage approximately 60% of the solids through the thermal drying pathway and the balance via the Class B dewatered cake land application program as shown on the left side of Figure 2. Additionally, moving from a 15% dewatered cake to a 90% dried pellet would significantly reduce the total mass and volume of solids managed by ReWa as shown on the right side of Figure 2. The recommended course of action developed can be advanced in phases as indicated in Table 1. The timeline shown is flexible and may be adjusted to address a changing regulatory environment or sustainability initiative for ReWa. This paper and presentation will describe the evaluations conducted as part of the master planning effort and present the selected biosolids management path forward as detailed above.

This paper was presented at the WEF Residuals and Biosolids Conference in Columbus, Ohio, May 24-27, 2022.

SpeakerBorgmann, Ruth

Presentation time

13:30:00

14:00:00

Session time

13:30:00

16:45:00

Session number15

Session locationGreater Columbus Convention Center, Columbus, Ohio

TopicBeneficial use, Land Application, Master Planning

Author(s)

R. Borgmann

Author(s)R. Borgmann1; C. Bullard2; J. Struve3; A. Price4

Author affiliation(s)Hazen and Sawyer; 1Hazen and Sawyer; 2Residuals and Biosolids Speaker; 3Renewable Water Resources; 4

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2022

DOI10.2175/193864718825158419

Volume / Issue

Content sourceResiduals and Biosolids

Word count13

Preparing for the Future: WAS Only Indirect Thermal Drying at Manchester Creek WWTP

Abstract

Summary This paper and presentation will discuss the planning that went into the design of a new solids processing facility at the City of Rock Hill's wastewater treatment plant, the Manchester Creek WWTP (MCWWTP), to accommodate a future secondary treatment process change and plant expansion. Specifically, the paper will discuss the accommodations that were made in design for existing and future feedstocks to the solids train. The pre-selection process for the belt filter presses (BFPs) and the indirect thermal dryer will be discussed including details on the manufacturer coordination and selection parameters. The benefits of thermal drying and flexibility inherent to the design of the MCWWTP's biosolids facilities will also be explored. Background The Manchester Creek WWTP (MCWWTP) treats wastewater for the City of Rock Hill, South Carolina. The MCWWTP has a currently permitted maximum month capacity of 20 million gallons per day (MGD). Final treated effluent is discharged directly to the Catawba River upstream of its confluence with Manchester Creek. A liquid train expansion and improvement project is currently under design to expand the plant to a maximum month capacity of 30 MGD, with an ultimate buildout capacity of 50 MGD. In the existing solids handling process, solids from primary and secondary clarifiers are currently blended and dewatered with two 2.0-meter width belt filer presses (BFPs) to approximately 22% total solids (%TS). Dewatered cake is transported to either the Water and Sewer Authority of Cabarrus County's (WSACC) sewage sludge incinerator to be incinerated; to the Anson County landfill for disposal; or to the McGill Environmental New Hill (NC) Facility for composting. The MCWWTP contracts dewatering operations, dewatered cake transportation, and dewatered cake disposal services to a contract service provider. In accordance with the latest MCWWTP Biosolids Master Plan, the City of Rock Hill is pursuing improvements at MCWWTP that will improve the dependability of the existing solids management options and expand the plant's biosolids facilities to handle the load associated with the plant expansion. Following the completion of the 30 MGD expansion, the MCWWTP will eliminate the primary clarifiers and utilize an aerobic granular sludge process leading to a change in solids feedstock to the solids train. The solids project will be constructed prior to the 30 MGD expansion and therefore must accommodate both the existing and future solids feedstocks as a part of the design. The updated biosolids facilities will improve plant operation, provide multiple outlet options (potential for Class A Biosolids), and provide improvements to outdated facilities. The project includes the following facilities: -WAS Storage - BFP Dewatering - Indirect Thermal Drying - All Ancillary Equipment The new Thermal Dryer Facility will be designed for WAS only thermal drying. By eliminating primary sludge (PS) in the dryer feedstock, the heat transfer efficiency (lb-water/hour per square foot heat transfer surface area) of the thermal dryers is significantly increased in comparison to PS + WAS solids, due to the recalcitrant nature of the blend. Furthermore, undigested PS does not form a granular product but tends to be more fibrous in nature, whereas undigested WAS typically forms a granular product with higher bulk density more suitable for land application, storage, and handling. Because the solids project will be completed in advance of the liquid train expansion there will be an approximately five-year period when primary solids will be produced at the MCWWTP and will still need to be processed, but not dried. Therefore, the new solids facilities include the provision to process PS and WAS separately during the five-year period prior to the expansion and process change completion. See Figure 1 for the initial process flow diagram with two separate treatment trains for PS and WAS and Figure 2 for the ultimate planned solids process flow diagram. Flexibility in Solids Facility Design Because all new infrastructure associated with the primary solids management train will be for a short period of time the overall project goal was to minimize capital expenditures on PS only equipment that could not be used following the process change. For solids storage, a small, bolted steel tank (25,000 gal) with a vertical turbine mixer was proposed for PS storage. Following the liquid train conversion, the PS tank would be taken out of service and could be repurposed elsewhere onsite or demolished. The capital expenditure associated with the PS tank was considered necessary for operator flexibility, but tank size was reduced to keep costs minimal. A new, larger WAS storage tanks was proposed to support the long-term plan for a conversion to a WAS only process and a new dryer operational schedule of 24 hours per day, 4 days per week at annual average conditions. The larger WAS storage allows the facility to practice continuous wasting and decouple the liquid train operations from the solids operations by providing a wide spot in the line as well as provide a homogenous feed to the BFPs. The proposed Dewatering Facility is designed to house up to four (4) belt filter presses to meet long-term buildout. Initially three BFPs will be installed in the building and PS and WAS will be dewatered on separate BFPs. Piping and valving interconnections will allow the two streams to remain completely separate but provide needed equipment flexibility and redundancy to have a shared standby machine. The WAS dewatered cake will be conveyed to the thermal dryer facility while the PS dewatered cake will be hauled offsite for processing. The dewatering building should see a seamless transition to all BFPs dewatering the same feedstock from the WAS Storage Tanks following the process conversion. Because the Thermal Dryer Facility will only be designed for a WAS only stream the facility should transition easily with the liquid train process upgrades. Future planning discussions with the paddle/screw dryer manufacturers revolved around the impact of the liquid train process change on solids dewaterability and solids loading to the dryer. Overall, the thermal dryer facility will significantly decrease the water content of the biosolids, which will reduce both the volume and wet mass to be transported and final product to be managed by Rock Hill and increase their product end use alternatives. Equipment Selection Two requests for proposals (RFP) were developed for pre-selection of the belt filter press manufacturer and thermal dryer system supplier to help expedite the design process. Pre-selection of the thermal dryer system supplier was an important step as each manufacturer has their own intricacies and design details. Working with only one dryer manufacturer following preliminary design allowed manufacturer specific details and requirements to be coordinated in advance of construction. Manufacturer coordination prior to issuing the RFPs included: bench scale testing across a range of primary and secondary sludge blends to understand the impact of the PS only, WAS only and PS/WAS blend on dewatering equipment throughput, polymer usage and dewatered cake concentrations and thermal dryer performance (fouling potential, heat transfer, final product quality). In addition, potential technology suppliers were invited to meet with Rock Hill to discuss their technology offerings and differentiators from their competitors. Manufacturers were given the opportunity to review the equipment specifications that were a part of the RFP package. RFPs were evaluated using the methodology shown in Tables 1 and 2. The paper and presentation will detail the selection process.

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

SpeakerBorgmann, Ruth

Presentation time

08:30:00

11:15:00

Session time

08:30:00

11:15:00

SessionCase Studies & Lessons Learned

Session number27

Session locationOklahoma City Convention Center, Oklahoma City, Oklahoma

TopicDewatering, Drying, Flexibility

Author(s)

Borgmann, Ruth

Author(s)R. Borgmann1, C. Bullard1, M. Bridwell1, A. Young1

Author affiliation(s)Hazen and Sawyer 1; Hazen and Sawyer 1; Hazen and Sawyer 1; Hazen and Sawyer 1;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Jun 2024

DOI10.2175/193864718825159450

Volume / Issue

Content sourceResiduals and Biosolids Conference

Word count14

Taking a Late Phase Detour: Dewatering System Redesign for the Plum Island WPCP

Abstract

Summary This paper and presentation will discuss the in-plant operating conditions leading to a late-in-the-design-process dewatering technology selection reevaluation for the Charleston Water System's (CWS) main wastewater treatment facility, the Plum Island Water Pollution Control Plant (PIWPCP). Specifically, the paper will discuss the steps taken to reevaluate the solids dewatering design after 90% design completion by transitioning the selected dewatering technology and making this change while minimizing impacts to the construction schedule already underway. The efficient and timely redesign around a new dewatering technology was achieved by leveraging onsite pilots, solids sampling and off-site assessments, as well as manufacturer presentations to assist CWS in reviewing the preferred technology vendor options. Ultimately, CWS selected centrifuges to replace the originally selected rotary fan press technology to ensure improved dewaterability across a wide range of influent characteristics. Furthermore, the paper will discuss the design challenges associated with accommodating a dewatering technology change while concurrently minimizing impacts to the building footprint and structural design in order to curtail construction sequencing design delays and allowing the Construction Manager At Risk (CMAR) contractor to begin pile driving and sub-surface foundation work as originally scheduled. Background The Plum Island Water Pollution Control Plant (PIWPCP) is the main wastewater treatment facility for Charleston Water System (CWS), providing wastewater treatment for the City of Charleston, Daniel Island, James Island, and several surrounding municipalities. The facility is positioned on a 22-acre island surrounded by salt marsh and discharges to the tidally influenced Charleston Harbor at a rated capacity of 36-MGD. This location causes significant constructability issues due to high ground water from tidal influences and local major rain events coupled with challenging subsurface issues and seismic codes requiring major structures to be built on pile supported foundations. Prior to design, a long-term facility master plan had been completed for the PIWPCP identifying facilities required to accommodate currently permitted flows of 36-MGD with expansion up to an ultimate facility capacity of 54-MGD on both the liquid and solids treatment trains. In accordance with the master plan recommended improvements, new solids handling facilities were included as part of the Phase 4 Capital Improvements Project. These capital improvements included the following new solids handling processes: - New Solids Handling and Dewatering Building with Rotary Fan Press dewatering technology - Three (3) Sludge Storage Tanks with Blending Pumps - Dewatered Cake Storage Sludge Hopper and Loadout Facility The existing dewatering unit process equipment at the facility includes three (3) rotary fan press dewatering units which dewater a blend of undigested primary and secondary solids resulting from the liquid treatment process. Secondary solids are gravity thickened prior to blending with the primary sludge solids immediately upstream of dewatering in a blending tank. CWS had many years of acceptable operating experience (See Figure 1, January 2017 through October 2021) with the existing rotary fan press technology entering the detailed design phase of the upgrade and had thus selected the same technology to utilize in the new dewatering facilities to be constructed during the Phase 4 Capital Improvements Project. The originally proposed Phase 4 Solids Handling Building was designed to hold up to seven (7) 8-channel rotary fan presses with ancillary feed, polymer makeup, and conveyance equipment to meet long-term buildout solids handling needs and accommodate facility expansion up to a 54-MGD ultimate treatment capacity. However, during the later stages of the facility design, CWS identified insurmountable issues with the existing rotary fan press technology used for dewatering (See Figure 1, After October 2021). Steep declines in dewatered cake solids content resulted in increased wet cake mass and volumes for transportation and disposal at a local landfill facility, significantly increasing downstream disposal costs. Concurrently, the local landfill was significantly increasing tipping fees for 'wet waste', further exacerbating solids disposal costs for CWS. In addition to reduced dewatered cake solids content, the rotary fan press solids and hydraulic loading rate performance declined which would require increased numbers of dewatering units to process the anticipated solids loadings under current and future operating conditions. This combination of impacts, decreased dewatered cake solids, increased downstream management costs, and reduced rotary fan press performance, caused CWS to investigate and reconsider the dewatering technology selection and basis of design for the new facility after the rotary fan press design had advanced to the 90% completion level. Upon further investigation, it was determined that influent characteristics at the plant had changed since the initial assessments, causing a detrimental impact on the proposed dewatering equipment performance. Some of the impacts were due to a new influent conveyance tunnel system and collection system behavior between wet and dry periods, new headworks facilities with increased grit removal capability, and new primary and secondary treatment facilities which were included with recently completed capital improvements projects (Phase 2 and Phase 3 projects). Following this initial investigation, CWS approved reconsideration of the dewatering technology selection to include other dewatering technologies (e.g., belt presses, centrifuges). Alternative Technology Selection Immediately following the decision to reconsider the dewatering technology selection, work began to conduct on-site pilot and demonstration testing of belt filter presses and centrifuges. Concurrent demonstration testing was conducted on the same feed sludge for the existing rotary fan presses, a trailer-mounted belt filter press, and a trailer-mounted centrifuge to assess dewatered cake performance and other design parameters for each technology. Table 1 and Figure 2 show the results of the concurrent dewatering technology testing. On-site testing was coupled with off-site and bench scale testing across a range of primary and secondary sludge blends to understand the impact of the primary to secondary sludge (PS/WAS) ratio on anticipated dewatering unit performance to inform operational decision making. Lastly, potential technology suppliers were invited to make presentations to CWS regarding their technology offerings. Ultimately, CWS selected high solids, horizontal decanting centrifuges to replace the rotary fan presses to ensure improved dewaterability across a wide range of influent characteristics and PS/WAS ratios. Following the updated technology selection, the planned dewatering facility had to be redesigned on an accelerated schedule for the new technology while staying within the same building envelope to retain as much of the prior design structural framing and layout as possible to expedite the design and permitting processes. This paper will share some of the design challenges associated with and overcome with the conversion from rotary fan press to centrifuge dewatering technology across the various engineering disciplines (e.g., process mechanical, structural / architectural, and electrical and control systems). Updated design of the new dewatering facility has since been completed with centrifuges (See Figure 3 for a rendering comparison) and construction is currently progressing on the facility.

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

SpeakerYeh, Jacqueline

Presentation time

15:45:00

16:15:00

Session time

13:30:00

16:45:00

SessionDewatering

Session number05

Session locationOklahoma City Convention Center, Oklahoma City, Oklahoma

TopicBiosolids, Dewaterability, Process Design

Author(s)

Yeh, Jacqueline

Author(s)J. Yeh1, R. Borgmann1, C. Bullard1, J. Hartwig J. Walker2, G. Hider2

Author affiliation(s)Hazen and Sawyer 1; Hazen and Sawyer 1; Hazen and Sawyer 1; Hazen and Sawyer 1; Charleston Water System 2; Charleston Water System 2;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Jun 2024

DOI10.2175/193864718825159439

Volume / Issue

Content sourceResiduals and Biosolids Conference

Word count14