Young, Thor, Young

Young, Thor

Thor Young is GHD's North American Wastewater Treatment & Recycling Leader. He is based in Maryland and has been with GHD since 1990.

Titles from this speaker

Comparison of Ballasted Activated Sludge Technologies

Abstract

Overview
Ballasted Activated Sludge (BAS) technologies combine the benefits of enhanced settling and increased capacity with the familiarity of a Conventional Activated Sludge (CAS) system which many operations staff are already comfortable with. BAS technologies can make maximum use of existing infrastructure at many existing conventional treatment facilities. Recent innovations in BAS technologies have expanded the range of alternatives for process design engineers to consider, including some which merge characteristics of both BAS and aerobic granular sludge (AGS) technology into single system.
Background
The primary benefit of BAS is that it can dramatically increase the settling rate of the biomass (Young et al, 2013). Due to this high settling rate, ballasted processes can significantly increase secondary clarifier solids loading rates, which can, in turn, allow higher Mixed Liquor Suspended Solids (MLSS) concentrations to be carried in the biological reactors. The higher MLSS concentrations in the biological reactors allow for either higher Solids Retention Time (SRT) in the process, for greater treatment capacity, or some combination of both compared to a CAS process with the same tank volume. Therefore, BAS can typically achieve treatment objectives with less process reactor volume and less secondary clarifier area than conventional processes. A variety of inert media has been tested as potential ballast to bind with biological floc to enhance the settling characteristics of activated sludge. A commercially viable system using magnetite (Fe3O4), a readily available inert form of iron ore with a specific gravity of 5.2 for ballasting activated sludge was patented in 2010 by Cambridge Water Technologies (now owned by Evoqua) and as of 2021 the Magnetite Ballasted Activated Sludge (MBAS) process had more than 20 full-scale installations around the world. A more recently proposed innovation to this technology has experimented with the use of stacked tray grit separator units to separate the heavier magnetite ballasted floc faster, and in a smaller footprint, than is achievable with conventional secondary clarifiers (Gilmore, 2021). This would allow the technology to further shrink its footprint. Another recent innovation in BAS is the use of kenaf as the inert ballast media. Kenaf is a natural organic cellulosic plant fiber that is high in both surface area and absorptivity. Due to its high surface area, the kenaf core is capable of growing thick biofilms, some of which develops in the form of granules with high specific gravity which increases the sludge settling characteristics similar to what is achieved with magnetite ore ballast. However, the kenaf media also serves as a place for a biofilm to grow, such that a significant amount of the total biomass in the system consists of the biofilm growing on the suspended kenaf as opposed to strictly relying on the suspended biomass in a CAS or MBAS (Boltz et al, 2021). The use of kenaf media for activated sludge ballast has been patented by Nuvoda as the Mobile Organic Biofilm (MOB) process. Like CAS, reactor influent is combined with return activated sludge and treated in process reactors. Like the MBAS process, the system is initially charged with the inert media (in this case kenaf instead of magnetite) and then the bulk of the media is recycled back from the secondary clarifiers to the front of the process reactors in the return sludge while a fraction is recovered and recycled from the waste sludge. Unlike the MBAS, the biological activity is divided between suspended biomass and the biofilm. Therefore, the MLSS in the MOB process can be kept much lower than the MBAS or other alternatives. With both types of BAS technology, efficient recovery and reuse of the media is key to sustainable economic performance. In the case of MBAS, magnetite is recovered from waste sludge using shear mills followed by rotating magnetic drums to separate out the ballast from the biological solids. In the case of MOB, kenaf is recovered by pumping the waste sludge through rotary drum screens. The first full-scale municipal treatment installation of MOB was at Moorefield, West Virginia in 2016. MOB technology has been more recently piloted at larger utilities, including Clean Water Services in Oregon (Schauer, 2021).
Cost Comparison of Technologies for Target Installation
Concept design and lifecycle cost estimates were developed for the application of MBAS and MOB technologies at a 20 mgd capacity wastewater treatment facility in the Chesapeake Bay Region. These technologies were compared to each other and to the originally planned CAS upgrade of the facility.
These applications were applied to an existing CAS facility consisting of preliminary and primary treatment, 4-stage Bardenpho process reactors for biological nitrogen removal, and circular secondary clarifiers. The existing facility had severe limitations in secondary clarifier capacity and the Owner was planning to construct three additional secondary clarifiers and an additional process reactor in order to reduce solids loading rates and allow SRT targets to be reliably maintained in the process reactors, based on historical SVI values. Applying MBAS and MOB technology to this facility would reduce the number of new secondary clarifiers required and eliminate the need to construct an additional process reactor. On the other hand, MBAS and MOB technology required supplemental mixing in the process reactors and the addition of a ballast media recovery facility as well as periodic addition of new ballast media to keep the system fully charged. Design criteria for the concept designs are summarized in Table 1. The 20-year Operation & Maintenance Net Present Value and Project Lifecycle Costs of the concept designs are summarized in Figures 1 and 2.
Conclusion Based on the analysis, all three technologies offered similar lifecycle project cost for this target application. However, MBAS and MOB technologies provide reduced site footprint and lower projected operating costs. On the other hand, both MBAS and MOB require the operation of a media recovery unit to recover media from the waste sludge for reuse. The MOB system has significantly lower oxygen demands thanks to the lower SRT and improved oxygen transfer rates, and the higher yield of waste sludge can potentially yield more biogas, so that this system would be closer to energy neutrality than the other two systems. In this case, both MBAS and MOB was able to avoid the construction of a new process reactor and secondary clarifier, thus saving significant construction cost that was offset by the cost of the installed equipment. With optimization, it may be possible to further reduce the initial capital cost of applying these technologies and allow them to be more cost competitive compared with conventional approaches. At facilities where there is no room to add reactors and/or clarifiers, these technologies would offer an option for expansion while maintaining the treated effluent quality.

Ballasted Activated Sludge (BAS) technologies combine the benefits of enhanced settling and increased capacity with the familiarity of Conventional Activated Sludge (CAS). This paper provides an overview of Magnetite Ballasted Activated Sludge (MBAS) and Mobile Organic Biofilm (MOB) technologies and uses a case study to compare design criteria, capital and lifecycle costs, and non-cost decision factors to compare the two technologies with a conventional CAS approach.

SpeakerYoung, Thor

Presentation time

15:30:00

15:55:00

Session time

15:30:00

17:00:00

TopicMunicipal Wastewater Treatment Design, Nutrients

Author(s)

Young, Thor

Author(s)Thor Young1; Coenraad Pretorius2; Tom Biagioli3

Author affiliation(s)GHD Inc., Bowie, MD1; GHD Inc., Irvine, CA2; GHD Inc., Bowie, MD3

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2022

DOI10.2175/193864718825158688

Volume / Issue

Content sourceWEFTEC

Word count7

Data-based Headworks Design: The Value of Field Test Data for Screening Design

Abstract

To support the upgrade and replacement of existing coarse and fine mechanical screens at a large wastewater treatment facility treating a combined sewer system, field data was collected to analyze the solids capture effectiveness of different screen size and type combinations. Each facility’s wastewater influent is different, and different types of screens perform differently at different facilities. This paper shows the value of collecting screen performance field data to better inform screening facility equipment upgrade decisions.

To support the upgrade of existing coarse and fine mechanical screens at a large wastewater treatment facility treating a combined sewer system, field data was collected to analyze the solids capture effectiveness of different screen size and type combinations. Each facility's wastewater influent is different, and different types of screens perform differently at different facilities. This paper shows the value of collecting screen performance field data to better inform screening decisions.

SpeakerYoung, Thor

Presentation time

15:30:00

16:00:00

Session time

15:30:00

17:00:00

SessionDesign Tools and Technologies for Preliminary and Primary Treatment

Session locationRoom S404c - Level 4

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

Author(s)

Young, Thor

Author(s)T. Young 1; F. Glapion 2 ; L. Musselman 3; T. Young 1; S. Sturtevant 4;

Author affiliation(s)GHD 1; Alexandria Renew Enterprises 2 ; GHD 3; GHD 1; Hydro-Dyne Engineering 4;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2023

DOI10.2175/193864718825159122

Volume / Issue

Content sourceWEFTEC

Word count13

Dynamic Process Modelling for Aeration Blower Design at the Humber Treatment Plant

Abstract

The City of Toronto initiated a design and construction project in 2022 to replace the existing secondary treatment aeration blowers at the Humber Treatment Plant. A comprehensive review of historical flow and plant operating data was conducted to derive a design-year hourly diurnal flow and load profile (8,760 discrete data points) for input into a commercial wastewater process simulation tool. The output oxygen demands were used to generate process airflows considering varying wastewater temperatures, standard oxygen transfer efficiency based on net airflow per diffuser and diffuser depth, and dynamic alpha based on aeration basin oxygen uptake rates at each time step in the flow and load profile. Statistical and seasonal analyses were applied to the resulting airflow data sets to determine performance guarantee points at varying inlet air conditions for blower equipment preselection

The City of Toronto initiated a capital project in 2022 to replace the existing secondary treatment aeration blowers at the Humber Treatment Plant. A comprehensive approach was implemented to develop the process design basis for the new aeration blowers using dynamic wastewater treatment process modelling to derive process airflows for a one-year hourly diurnal flow and load profile. Resulting airflows were used to determine performance guarantee points at varying inlet air conditions.

SpeakerRizzuti, Daniel

Presentation time

08:30:00

09:00:00

Session time

08:30:00

10:00:00

SessionThe Big Bad Blower: Huffing and Puffing Air Through Your Aeration Basins

Session locationRoom S401d - Level 4

TopicEnergy Production, Conservation, and Management, Facility Operations and Maintenance, Intermediate Level, Municipal Wastewater Treatment Design

Author(s)

Rizzuti, Daniel

Author(s)D. Rizzuti 1; J. Kraemer 2 ; Pretorius 3; T. Young 4; T. Gretarsson 5; D. Pease 6; T. Shen 7; E. Eini 8; V. Szonda 6; D. Rizzuti 1;

Author affiliation(s)GHD Ltd., Waterloo, ON 1; GHD Ltd., Waterloo, ON 2 ; GHD 3; GHD 4; GHD 5; City of Toronto, ON 6; City of Toronto, ON 7; City of Toronto, ON 8; City of Toronto, ON 6; GHD 1;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2023

DOI10.2175/193864718825159068

Volume / Issue

Content sourceWEFTEC

Word count13

Description: Let Gravity Do The Work: Use of Siphon and Partial-Siphon Permeate Design for MBR...

Let Gravity Do The Work: Use of Siphon and Partial-Siphon Permeate Design for MBR Systems

Abstract

Introduction
Most membrane bioreactors (MBRs) use pumps to create a vacuum within the lumen or on the back side of the membranes to draw permeate through them. However, if the downstream head is sufficient, a siphon or partial siphon configuration can be used to draw permeate through the membranes by gravity. The use of a siphon can provide numerous benefits including lower capital and operating costs, as well as reduced equipment complexity and maintenance. Despite these benefits, the use of siphon and partial-siphon for permeation remains rare in MBR designs. This paper will explore siphon design and operation and draw on case studies to highlight potential benefits of siphon design in MBR systems.
Background
In an MBR, membranes are used to separate purified effluent (i.e. permeate) from mixed liquor following an activated sludge biological wastewater treatment process. Trans-membrane pressure (TMP) is the difference in pressure between two sides of a membrane. The TMP is influenced by many factors including the flux (flow per surface area) across the membrane, water temperature, mixed liquor concentration and characteristics, and biological and chemical fouling of the membrane surface. MBRs are typically designed to operate over a TMP range from as little as 1 to 2 psi (0.07 to 0.14 bars) with clean membranes at lower flux rates to higher TMP operation as flux rates increase and membranes become fouled. The vast majority of MBR installations rely on permeate pumps to overcome the TMP and hydraulic losses through the MBR system. Pump operation is usually controlled based on a combination of influent flow and the water level in the tank where the immersed membranes are located. As water level increases, permeate pump speed increases to maintain the water level in the tank within the desired operating band. However, when hydraulic conditions allow, permeate can be pulled through the membranes without the use of permeate pumps. Siphon Design Options In a full-siphon design, sufficient downstream head is available under all operating conditions for permeating through the membranes. Flow is typically regulated through the membranes by control valves on the permeate piping from each set of membrane cassettes. The control valves are throttled to maintain water level in the membrane tanks within the design operating band and control flow through the membrane system. In a partial siphon design, flow passes through the membranes by gravity under lower TMP operating conditions. If required, pumping is used under higher TMP operating conditions to generate additional negative pressure within the lumen or on the back side of the membranes. Two types of pumping arrangements are possible. In a closed-system partial-siphon design, conventional permeate pumps are used on the permeate piping to draw vacuum in the permeate piping when required. In an open-system partial siphon design, the permeate flow is conveyed to a lower tank open to atmospheric pressure where effluent pumps are used to draw down the water level in the lower tank when required. In the closed-system arrangement, bypass piping and valves are required around the permeate pumps to utilize the available head without pumping, while no bypass is required for the open-system arrangement. The three types of siphon designs are illustrated schematically in Figure 1. Note that all three types may require a backpulse tank to provide sufficient permeate storage to supply clean water flow back through the membranes periodically during maintenance or recovery cleans if reverse filtration is used for backpulsing or membrane cleaning by the membrane manufacturer.
Case Study 1: Brush Creek Water Pollution Control Facility (WPCF) The Brush Creek WPCF is a 6.0 mgd (22.7 MLD) treatment facility owned and operated by the Cranberry Township, PA. During upgrade of the original conventional activated sludge process to MBR in 2019, abandonment of the existing secondary clarifiers and effluent filters provided approximately 19 ft (5.8 m) of available driving head between the new membrane tanks and the existing chlorine contact tanks. After accounting for piping losses, this is sufficient to allow gravity permeation up to 4.8 psi (0.33 bars) membrane TMP. The required TMP across the membrane is a function of design operating conditions. For the Brush Creek WPCF, the optimum design was found to require a maximum TMP of 8 psi (0.55 bars). To accommodate the required maximum TMP at PHF through a full-siphon with maximum hydraulic losses would have required 29 ft (8.8 m) of driving head. The maximum required TMP could have been reduced through increasing the membrane surface area or lowering the maximum design mixed liquor suspended solids (MLSS), but this would have resulted in increased capital cost to purchase and house additional membranes or for larger BNR reactor volume. An open-system partial siphon arrangement was selected. Operational results for June 2019 through December 2021 are shown in Figures 2 and 3. TMP averaged about 0.5 psi (0.03 bar) during this period. The effluent pumps were required to operate only 115 hours during this 30 month period (mostly during high flow events), during other times all permeate flow was by gravity. Estimated construction and operating cost savings at design flow are shown in Tables 1 and 2.
Case Study 2: Linwood Water Reclamation Facility (WRF) The Linwood WRF is a 4.6 mgd (17.4 MLD) MBR facility owned and operated by the City of Gainesville, GA. Permeate flow from the immersed hollow fiber membranes is via full-siphon design since facility startup in 2008. The original membranes were replaced in 2017 through 2019. Operational results for 2017 through 2021 are shown in Figures 4 and 5. TMP averaged less than 1.0 psi (0.07 bar) more than 70% of the time during this period and never exceeded 3.6 psi (0.25 bar).
Conclusions
As shown in data reviewed from the Brush Creek WPCP and the Linwood WRF, the membranes operated for the majority of the time with less than 1.0 psi (0.07 bar) TMP. Therefore, if wastewater treatment facilities have as little as 3.3 ft (1.0 m) of driving head available downstream of the membrane tanks, they may be able to operate in siphon mode the majority of the time. This means that many facilities which may not have sufficient head to support full siphon operation may be still able to achieve substantial energy cost savings through partial siphon operation. In addition, a siphon system is more reliable and will continue to permeate even during a power outage. A siphon system also may reduce the amount of equipment and/or the rate at which pump and motor wear occurs. These benefits should be balanced against the added operational complexity of a partial siphon control system.

Using a siphon to permeate from membrane bioreactors (MBRs) can lower capital and operating costs and reduce equipment complexity. While a full siphon design requires 6-8 m of available head, a partial siphon design is practical if the available hydraulic head is much lower. In this paper, case studies of siphon MBR systems at Linwood WRF and Brush Creek WPCP are used to demonstrate MBR permeate systems can operate the majority of the time with less than 0.07 bar trans membrane pressure (TMP).

SpeakerYoung, Thor

Presentation time

16:00:00

16:25:00

Session time

15:30:00

17:00:00

TopicIntermediate Level, Energy Production, Conservation, and Management, Facility Operations and Maintenance, Municipal Wastewater Treatment Design

Author(s)

Young, Thor

Author(s)Thor Young1; Joel Kostelac2; Bridget Finnegan3; Graham Best4; Sarpreet Kuner5; Dewayne Cooper6; Mike Sedon7

Author affiliation(s)GHD Inc., Bowie, MD1; GHD Inc, Harrisburg, PA2; GHD Inc., Pittsburgh, PA3; SUEZ Water Technologies & Solutions, ON, Canada4; SUEZ Water Technologies & Solutions, ON, Canada5; City of Gainesville Department of Water Resources, Gainesville, GA6; Cranberry Township Sewer & Water Department, Cranberry Township, PA7

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2022

DOI10.2175/193864718825158719

Volume / Issue

Content sourceWEFTEC

Word count16

MBRs Are More Cost-effective Than Ever Before

Abstract

A cost model was developed to compare the capital and 20-year lifecycle cost of MBR vs. CAS treatment technology for a greenfield WRRF. Concept designs and cost estimates were developed for six treatment performance scenarios at two design flow capacities: 20 ML/d and 200 ML/d. Compared with a prior version of this model developed in 2012, MBR has become more cost effective compared to CAS in general, most notably for less stringent treatment requirements, while the cost savings of MBR for more stringent treatment requirements has improved, but more modestly. A primary driver of this is the advancements in membrane design, primarily the reduction in air scour energy for membrane cleaning due to new diffuser technology, greater membrane packing density reducing membrane equipment costs and further reducing air scour requirements, decreased membrane cleaning requirements and longer membrane life, and increased use of gravity permeation from membranes under average day operation.

SpeakerYoung, Thor

Presentation time

16:30:00

16:50:00

Session time

15:30:00

17:00:00

SessionAlternative Approaches to Intensify Secondary Treatment

Session locationRoom S404a - Level 4

TopicIntermediate Level, Municipal Wastewater Treatment Design, Nutrients

Author(s)

Young, Thor

Author(s)T. Young 1; J. Kraemer 2 ; D. Rizzuti 3; S. Malatches 4; J. Lim 5; C. Thiemig 5; T. Young 1;

Author affiliation(s)GHD Inc 1; GHD Inc, Waterloo, ON 2 ; GHD Inc, Waterloo, ON 3; GHD Inc, Toronto, ON 4; Veolia Water Technologies & Solutions, Oakville, ON 5; Veolia Water Technologies & Solutions, Oakville, ON 5; GHD Inc, Bowie, MD 1;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2023

DOI10.2175/193864718825159019

Volume / Issue

Content sourceWEFTEC

Word count8

Description: Real-world Reliability and O&M of High-speed Turbo and Integrally-geared...

Real-world Reliability and O&M of High-speed Turbo and Integrally-geared Blowers

Abstract

Aeration blowers consume around half of all electricity used at a water resource recovery facility (WRRF). Choosing the most efficient blowers can save money, electricity, and greenhouse gas emissions. High-speed turbo blowers and single-stage integrally-geared (SSIG) blowers offer some of the highest efficiencies for process aeration, but operations and maintenance (O&M) staff may not have experience with these technologies. This paper documents comparative O&M experiences between turbo and SSIG blowers compiled from interviews with thirteen (13) North American water utilities with medium to large size blower installations as well as the authors’ own experience and past projects. In addition, turbo blower reliability and failure data and maintenance contract information were solicited from turbo blower manufacturers and summarized. This information was used to support one water utility’s blower technology decision and the authors hope this information will be useful to other utilities as well.

This paper compares O&M experiences with turbo blowers and single-stage integrally-geared blowers from interviews with 13 North American water utilities with medium to large blower installations and the authors' experience and projects. Turbo blower reliability data and maintenance contract information from manufacturers is summarized. This information was used to support one utility's blower technology decision and the hope is this information will be useful to other utilities as well.

SpeakerKraemer, Jeremy

Presentation time

09:30:00

10:00:00

Session time

08:30:00

10:00:00

SessionThe Big Bad Blower: Huffing and Puffing Air Through Your Aeration Basins

Session locationRoom S401d - Level 4

TopicEnergy Production, Conservation, and Management, Facility Operations and Maintenance, Intermediate Level, Municipal Wastewater Treatment Design

Author(s)

Kraemer, Jeremy