Knight, Greg

Greg is an experienced process engineer with a 25 year history in the water industry. He has an extensive background in process design of wastewater and biosolids facilities and also previously worked as plant manager of a large potable water treatment facility in the UK. Prior to starting his career in water, Greg volunteered for 3 years as a Physics and Science Teacher in Ghana, West Africa.

Titles from this speaker

Implementation of a New Strategy for Gwinnett County's Biosolids

Abstract

WEFTEC, the largest water event of its kind in North America, offers water quality professionals the best in water quality education and training. With almost 200 technical sessions, workshops, mobile sessions, local facility tours and 1,000+ exhibitors, it is the premier water conference! The WEFTEC technical program is selected through a rigorous, peer-review process, ensuring that attendees experience the highest-quality education. WEFTEC speakers are experts and innovators, leading the way in water quality. The following paper was presented at WEFTEC 2020.

SpeakerKnight, Greg

Presentation time

13:30:00

13:50:00

Session time

13:30:00

14:30:00

SessionEvolution of Marketing, Technology, and Regulations for Biosolids Beneficial Uses

Session number212

TopicBiosolids and Residuals, Fundamental Level, Policy and Regulation, Public Communication and Outreach

Author(s)

G. KnightG. RamMohanR. HarrisL. MossJ. CarrB.F. DrouhardA. Travaglia

Author(s)G. Knight1; G. RamMohan2; R. Harris2; L. Moss1; J. Carr1; B.F. Drouhard1; A. Travaglia1;

Author affiliation(s)Black & Veatch, GA1; Gwinnett County Department of Water Resources, GA2

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2020

DOI10.2175/193864718825157788

Volume / Issue

Content sourceWEFTEC

Word count10

Implementation of Raleigh Water's Bioenergy Recovery Project

Abstract

Raleigh Water has made a significant investment in a Bioenergy Recovery Project at the 75-mgd Neuse River Resource Recovery Facility (NRRRF) to transform management of the City's biosolids. The Project is delivering a new system that will produce a high quality Class A biosolid product for beneficial use as a soil conditioner and renewable natural gas to offset fuel usage in the City's bus fleet. The new process will include sludge thickening, sludge screening, pre-dewatering, thermal hydrolysis, sludge cooling, anaerobic digestion, final dewatering, steam boilers, upgrading of digester gas to produce renewable natural gas (RNG), a sidestream deammonification system and potential future plans to accommodate potential receiving of fats, oils and grease in future. This presentation will focus on the following aspects of the project: - Design phase decision making related to selection of core technology -Maintenance of plant operations during construction -Planning for start-up and commissioning of the new system Design While the core process selection involving advanced digestion with thermal hydrolysis was made early in the project, several other key decisions needed to be made during the design phase to find the best-fit technical solutions to meet Raleigh Water's needs. Some of these key decisions are summarized in Table 1. The full paper will provide details regarding how these key decisions were made to ensure selection of cost-effective and efficient solutions to meet Raleigh Water's goals. Maintenance of Plant Operations (MOPO) During Construction The existing solids process and end use strategy at NRRRF included aerobic digestion of waste activated sludge (WAS) for liquid class B land application, lime stabilization of blended undigested sludge to produce a Class A product and third party composting of primary/WAS dewatered cake. It was vitally important that Raleigh Water maintained the ability to reliably process residuals during the construction period. A detailed MOPO planning exercise was undertaken to overcome various challenges associated with construction phasing and plant operation. Key 'pinch points' included: -The need to continue to process WAS while rehabbing the existing gravity belt thickener building -Continuing the ability to load out dewatered cake despite moving and re-purposing two cake bins to their new location for pre-THP cake storage -The need for continued final dewatering while rehabbing the belt filter press building -Conflicts between the existing lime stabilization system and plans for temporary dewatering Planning to overcome all of these challenges was achieved by the whole team including Raleigh Water staff, the design team of Hazen / B&V and the CMAR contractor, Crowder Construction. Schematics were prepared showing both the existing and new process with each step clearly marked up to show the solids processing route and key modifications to the process. This approach ensured that the whole team understood and was able to consider risks associated with the proposed approach. An example showing moving of the cake bins is provided in Figure 1. The full paper will provide details of the full strategy and key considerations for MOPO during construction, as well as lessons learned through the process. Proactive Planning for Commissioning and Operations Planning for commissioning of the Bioenergy Recovery Project has been a collaborative ongoing effort with monthly commissioning meetings held between the Raleigh Water O&M staff, the design team and the CMAR contractor. A key consideration has been the method for seeding and startup of the digesters and THP process. Because THP heats the feed sludge to a high temperature (killing off microorganisms in the sludge), seed sludge is required. To ensure that the digesters quickly meet Class A requirements, the plans included trucking of seed sludge from the existing THP digestion facility at Hampton Roads Sanitation District. Seeding with both liquid sludge and re-wetted cake were considered as viable options. Ultimately the team selected seeding with 1.0 MG of liquid sludge into Digester 2, to avoid the need for re-wetting of the sludge and the addition of alkalinity lost during dewatering at HRSD. The seeding approach involves the following steps: -Filling Digester 2 to 25 % full with disinfected reuse water -Heating the digester contents using steam injection into the recirculation line -Seeding with 1.0 MG of Class A liquid digested sludge from HRSD -Gradually ramping up feed from THP, based on a target volatile solids organic loading rate (lb of VS added per day per lb of VS in the digester) -Transferring 50% of the sludge in Digester 2 to Digester 1 when Digester 2 becomes full -Continuing to ramp up based on loading rate Projections showing the feed solids and digester levels are provided in Figure 2 and Figure 3 respectively. The final paper will provide an update on plant status based on activities completed in early 2023. Another key aspect of the proactive planning process has been to plan for additional staffing requirements and training needs for the facility, given the increased complexity of the new system in contrast to previous operations. The final paper will outline this transition process and planned staffing and training for the new facility.

This paper was presented at the WEF/IWA Residuals and Biosolids Conference, May 16-19, 2023.

SpeakerKnight, Greg

Presentation time

10:15:00

10:45:00

Session time

8:30:00

11:15:00

SessionSession 18: Managing Biosolids in the Carolinas

Session number18

Session locationCharlotte Convention Center, Charlotte, North Carolina, USA

TopicManaging Biosolids in the Carolinas

Author(s)

G. Knight

Author(s)J. Kiviniemi1, E. Bailey2, L. Joseph3, J. Bognar4, A. Hanna5, C. Bullard6, T. Lynch7, G. Knight8, C. deBarbadillo9, K. Proffit10, C. Link11,

Author affiliation(s)City of Raleigh1; Hazen and Sawyer2; Black and Veatch3; Crowder Construction4

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2023

DOI10.2175/193864718825158804

Volume / Issue

Content sourceResiduals and Biosolids

Word count8

Primary Filtration Waste: How Do We Handle This High Volume Waste? Completing the Carbon Diversion PFD - SAF Pilot Results

Abstract

Introduction Intensification processes have been a focus largely for secondary and anaerobic treatment processes. These approaches have enabled utilities to increase performance, reduce footprint, and enable carbon redirection and capture. As we continue to evaluate drivers that include capacity, nutrient removal, carbon redirection, intensification, and energy reduction, enhanced primary treatment (EPT) plays a key role to whole facility integration considerations. Primary filtration technologies are increasingly evaluated as an alternative that enables high carbon redirection through >80% TSS and 50 to 70% BOD capture in a footprint that is approximately 25% of conventional primary clarification. This technology offers significant opportunity for facilities to divert carbon from liquid stream systems to anaerobic digestion, saving on aeration costs and increasing biogas production. However, full integration into existing facilities requires consideration to existing thickening facilities. Primary filter sludge is a high volume, low concentration that is 2 to 3x the volume seen with conventional primary clarifiers with a concentration of 3,000 to 5,000 mg/L. Further, the characteristics of the waste stream include a significant increase to non-settleable TSS and colloidal material that was previously not captured with conventional primary treatment. A comparison of anticipated capture efficiencies of thickening technologies (Figure 1) and footprints (Figure 2) indicates conventional gravity thickeners are significantly disadvantaged compared to other mechanical thickening technologies. Primary filter technologies are often solids limited vs. hydraulically limited (as in the case of tertiary filters). A reduction in capture efficiency of 5 to 10% has a resulting impact to filter loading rates, increasing surface area requirements by an equivalent rate. This technology review also indicated a potential opportunity for Suspended Air Flotation (SAF), offering a high hydraulic loading rate with potentially high capture efficiencies. SAF, provided by Heron Innovators, is similar to dissolved air flotation thickening but uses a surfactant to aid in solids separation and flotation. However, the technology had no primary sludge (filter or clarifier) thickening references and limited municipal waste activated sludge (WAS) case studies (with most installations to date being industrial applications). The Trinity River Authority of Texas (TRA) will soon be expanding the Denton Creek Regional Wastewater System (DCRWS) Facility. One component of the proposed expansion is the addition of primary filters. A preliminary assessment of a range of thickening technologies using economic and noneconomic factors indicated that SAF thickening could offer substantial economic benefits to TRA. Potentially, the SAF system could require the least amount of equipment, which correlates to a smaller footprint, and low chemical conditioning requirements, which translates to lower operations costs. As a result of the evaluation of technologies, SAF was selected as the basis of design for co-thickening blended (primary and waste-activated) solids. The decision to select SAF as the thickening option in this design constitutes an uncommon and innovative use of this technology. To confirm suitability of SAF for primary filter applications and to better understand the key design parameters driving SAF performance in the blended solids thickening application at DCRWS, a SAF pilot study was conducted at the Ten-Mile Creek Regional Wastewater System (TMCRWS) Facility. TRA and BV worked with Herron Innovators, Inc., providers of the SAF technology, to develop the pilot test. SAF systems are similar in concept to the older dissolved air flotation (DAF) systems in that both technologies float solids to the top of their respective tanks for thickening and removal. The key difference is that DAF systems use pressurized air dissolved in water while SAF systems instead employ a surfactant charged emulsion of air and water (also referred to as 'froth') to efficiently float solids. This allows SAF systems to achieve high solids loading rates (SLRs), which reduces equipment and space requirements. Table 1 provides a summary of key design criteria comparing DAF and SAF technologies. The SAF pilot setup explored low solids concentration, high volume feed solids conditions indicative of primary filter solids and blended solids (primary solids + WAS) thickening applications. Key questions were explored related to hydraulic and solids loading rates as well as polymer and froth dosages, to determine what targets for each of these primary design criteria are best correlated with overall thickening performance in terms of solids capture and the resulting thickened solids concentrations. The pilot was operated for a total of five weeks to test a range of loading rates and scenarios. Pilot Setup The SAF pilot study was conducted at TMCRWS from July 11th through August 18th, 2023. The study setup included a trailer-mounted pilot-scale SAF unit provided by Heron, specifically the CF125 model, which has a flow capacity of 350 gpm and a flotation area of 17 ft2. Throughout the study, TRA staff collected samples twice daily for analysis. Results The results of the pilot study which will be elaborated on in the full paper, include:

*Capture Efficiency oPrimary Solids Capture Efficiency — the primary solids thickening performance was excell

Primary filtration, increases capture efficiencies in a small footprint. However, the backwash creates challenges due to the large volume and low concentrations. Pilot study focused on Suspended Air Flotation (SAF), with primary and blended sludges. Results indicate SAF linked with primary filters is capable of high loading rates, 5 to 10x that of conventional dissolved air flotation (DAF), with capture efficiencies of 95% and 5% thickened sludge.

SpeakerRedmond, Eric

Presentation time

09:30:00

09:50:00

Session time

08:30:00

10:00:00

SessionThickening and Dewatering: Design Considerations

Session number301

Session locationRoom 354

TopicBiosolids and Residuals

Author(s)

Redmond, Eric, Knight, Greg, Ruff, Caitlin, Harness, Crystal, Downing, Leon

Author(s)E.D. Redmond1, G. Knight2, C. Ruff3, C. Harness4, L.S. Downing5

Author affiliation(s)1Black & Veatch, IA, 2Black & Veatch, GA, 3Black & Veatch, TX, 4, TX, 5Black and Veatch, WI

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2024

DOI10.2175/193864718825159648

Volume / Issue

Content sourceWEFTEC

Word count21

Description: To Digest or Not to Digest -- An Updated Evaluation of an Age-old Question of Carbon...

To Digest or Not to Digest -- An Updated Evaluation of an Age-old Question of Carbon Management in Water Resource Recovery Facilities

Abstract

It has been accepted wisdom in the wastewater industry for many years that primary treatment combined with anaerobic digestion becomes more cost-effective the larger the size of the water reclamation facility, whereas at smaller facilities waste activated sludge (WAS) only systems are more commonly used. Primary treatment reduces the organic load on secondary processes, leading to aeration savings, and anaerobic digestion provides opportunities for beneficial use of biogas. However, for facilities with nutrient removal requirements, diverting carbon to anaerobic digestion can lead to a deficit of carbon for nutrient removal needs, and lead to costly addition of supplemental carbon. Meanwhile, treatment technology is constantly improving and changes in technology and green initiatives can have a significant impact on the optimum solution for carbon diversion. Several considerations are outlined below. ...Enhanced primary treatment (e.g. primary filtration): leads to higher carbon diversion to digestion and less carbon to secondary processes, reducing aeration basin volume and aeration costs, but potentially leading to higher supplemental carbon needs if nutrient removal is required. ...Primary sludge fermentation: can be used to solubilize some of the carbon in primary sludge for diversion back to liquid stream processes to meet nutrient removal needs, while also minimizing aeration basin volume that would otherwise be driven by additional aeration basin influent solids without primary treatment. Sidestream Enhanced Biological Phosphorus Removal (S2EBPR): provides the opportunity to ferment return activated sludge (RAS) or mixed liquor to drive biological phosphorus removal via carbon in the RAS/mixed liquor, reducing reliance on influent carbon or supplemental carbon. ...Partial denitrification anammox (PdNA): is an emerging process that has been proven at full scale and which has significant potential to reduce carbon needs for denitrification and also reduces aeration demand. Both S2EBPR and PdNA offer the potential to reduce supplemental carbon needs for nutrient removal, freeing up more carbon for diversion to anaerobic digesters. ...Renewable Identification Numbers (RINs): are green trading credits applied to the production of renewable fuel that incentivize the production of renewable natural gas (RNG) from biogas at wastewater facilities with anaerobic digesters. In addition to the current RIN system that incentivizes RNG, a pathway for electrical RINs (eRINs) may soon be available that could incentivize production of electricity (e.g. via combined heat and power systems) This paper will provide an economic analysis evaluating the impact of various factors on the decision of whether or not to implement primary treatment and anaerobic digestion at water reclamation facilities. Factors to be evaluated will include the following: 1.Facility size 2.Efficiency of primary treatment carbon capture (conventional versus enhanced primary treatment) 3.Nitrification only facilities compared to those with nutrient removal requirements for nitrogen and phosphorus 4.Implementation of primary sludge fermentation to provide more carbon to meet nutrient removal needs 5.Implementation of S2EBPR for more efficient use of carbon for P removal 6.Implementation of PdNA to reduce carbon needs for total nitrogen removal 7.Cost sensitivity to green incentives (e.g. RINs) for biogas upgrading To provide an example of the type of analysis that will be included in the paper, a preliminary life cycle cost analysis has been conducted for various sizes of facilities for the simplest scenario where only nitrification is required (no nutrient removal requirements). The full paper will expand on this analysis to develop life cycle costs to evaluate the factors outlined above. The following approach was taken: 1.Process unit sizing was developed for a range of facility sizes from 5MGD to 100MGD 2.Two scenarios were evaluated for each facility size, one with primary clarification and anaerobic digestion and the other with no primary clarification. 3.Capital, operating and life cycle costs were developed for each size of facility for each scenario. Details of the scope of capital costs included for each scenario are provided in Table 1. In general, the scope of capital and operating cost development was limited to items that would differ between the two scenarios being investigated. Details of the scope of operating costs included and key assumptions are provided in Table 2. It is acknowledged that the assumptions made inevitably impact the outcome of the evaluation and sensitivity to a range of assumptions will be included in the final paper. Net present costs were developed using a 2% inflation-adjusted rate over 20 years. Results are shown in Figure 3 and Figure 4. Key take-aways from this preliminary analysis are as follows: 1.Capital cost for the scenarios utilizing primary clarification and digestion were higher than those with WAS only activated sludge 2.Operating costs for the WAS only activated sludge scenarios were higher than those with primary clarification and digestion 3.As expected, economies of scale led to primary treatment and anaerobic digestion becoming more cost-effective as facility size increases The full paper will elaborate extensively on this analysis, providing utilities with useful insights to help understand under what conditions primary treatment and anaerobic digestion is favorable compared to WAS only activated sludge.

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

SpeakerKnight, Greg

Presentation time

09:10:00

09:30:00

Session time

08:30:00

10:00:00

SessionInnovations in Waste-to-Value Technologies: Carbon Management and Resource Recovery

Session number22

Session locationBaltimore Convention Center, Baltimore, Maryland, USA