Sivaprasad, Shyam

Shyam is a Water/Wastewater Process Engineer at Stantec. Shyam received his bachelors degree in Chemical Engineering from India and Masters degree in Agricultural Biological Engineering from The Ohio State University with research focus on thermochemical conversion and wastewater treatment. He is a certified LEED Green Associate and PE in the Environmental discipline. His experience includes biosolids processing and solids dewatering from planning level studies to bench scale testing, pilot testing and full scale detailed design.

Titles from this speaker

Description: Alternate: We're on the Road to Somewhere in Paradise: A Roadmap for Novel and...

Alternate: We're on the Road to Somewhere in Paradise: A Roadmap for Novel and Sustainable Biosolids Management at the Sand Island WWTP, Honolulu, Hawaii

Abstract

Introduction and Background The Sand Island Wastewater Treatment Plant (Sand Island) is located on the idyllic shores of Oahu with deep blue waters laying before it, lush green mountain of jungle vegetation behind it, Pearl Harbor to its left, and the bustling high-rises of downtown Honolulu and Waikiki to its right. Sand Island is owned and operated by the City and County of Honolulu (CCH). Sand Island is currently a 90 MGD primary treatment with UV disinfection and biosolids treatment plant with ocean discharge for its treated effluent and thermally dried pellets for its biosolids distribution. CCH is under a federal mandate to upgrade Sand Island to meet full secondary treatment water quality standards by 2035. Sand Island is undergoing its upgrade in two phases. Phase 1 is under construction to build ~20 MGD of Membrane Bioreactors (MBR) capacity and additional mesophilic anaerobic digestion capacity to handle the waste activated sludge (WAS) along with the projected increase in primary sludge due to the continued population growth within the CCH service area through 2035. Phase 2 is in progress transition into the detailed design phase and will complete the full secondary treatment capacity to 90 MGD including wet weather storage to carry Sand Island through a 2045 planning horizon. The selected secondary treatment process for Phase 2 is Aerobic Granular Sludge (AGS) and the combination of Primary sludge, MBR WAS and AGS WAS, a never-before-seen sludge cocktail in our industry and a unique blend to consistently process on a small island with limited space and options for biosolids product distribution. This is the backdrop for a one-of-a-kind solids alternatives analysis in paradise. The existing solids handling treatment at Sand Island involves conventional mesophilic digestion, dewatering, and drying. The existing solids handling system will require additional treatment capacity to process the increased solids load when full secondary treatment is in service. With this task at hand we set to work on pitting tried and true biosolids processing strategies for Sand Island against new effective options adaptable to the Hawaii market to produce sustainable biosolids and energy to fuel Sand Island. This will also lower the utilities' impact of the Island of Oahu and its limited and imported natural resources. Solids Treatment Alternatives Four distinct alternatives for the solids treatment upgrades were identified as potentially viable solutions and were evaluated on their merits to economically enhance process performance, redundancy and reliability. - Alternative 1: Conventional mesophilic anaerobic digestion (AD) + Thermal Drying (TD) - This alternative is the baseline case and uses the existing solids treatment process philosophy of mesophilic anaerobic digestion at a 20-day solids retention time (SRT) followed by rotary drum drying, producing Class A dried pellets for beneficial reuse (Figure 1) expanded to the new Primary Sludge + WAS solids projections through 2045. - Alternative 2: Thermal Hydrolysis Process (THP) + AD + TD - This alternative modifies the existing treatment process to include sludge pre-conditioning for THP followed by mesophilic anaerobic digestion, producing Class A biosolids and reducing the volume of solids undergoing digestion, followed by dewatering, rotary drum drying, and producing Class A biosolids for beneficial reuse (Figure 2). - Alternative 3: THP + AD + Combined Heat & Power (CHP) (No Dryer) - This alternative modifies Alternative 2 to eliminate the drying operation. THP produces Class A biosolids cake that can be land applied. However, the land application market for Class A dewatered cake in Oahu requires further analysis. Dewatered cake can also be accepted at H-POWER (Covanta Honolulu Resource Recovery Venture) to produce power. By eliminating thermal drying a surplus of biogas becomes available for heat and power generation through a CHP system with a very favorable return on investment (ROI) of 5 years due to the resource limitations of Hawaii (Figure 3). - Alternative 4: Thermophilic Anaerobic Digestion (TPAD) + CHP (No Dryer) - This alternative would modify and augment the anaerobic digestion process currently under construction at Sand Island with batch thermophilic anaerobic digestion at 55°C (131 °F) followed by mesophilic anaerobic digestion at 35 °C (95 °F) (TPAD) to produce a low odor Class A biosolids cake eliminating the need for thermal drying to achieve Class A Biosolids. However, the land application market for Class A dewatered cake in Oahu requires further analysis. Dewatered cake can also be accepted at H-POWER (Covanta Honolulu Resource Recovery Venture) to produce power (Figure 4). Capital, Operations and Maintenance (O&M) Costs Class 5 Opinion of Probable Construction Cost (OPCC) estimates include the costs associated with construction, engineering, administration, and contingency were performed. The total capital cost with high and low range sensitivity analysis estimates for Alternatives 1, 2, and 3 is depicted in Figure 5. Alternative 4 is still under evaluation and will be complete by the time of presentation. O&M costs include the costs associated with energy and consumables use, labor, and the maintenance for the improvements identified and detailed in each alternative. Figure 6 depicts the annual O&M costs associated with Alternatives 1, 2 and 3. Alternative 4 is still under evaluation and will be complete by the time of presentation. Net Present Value Analysis NPV analysis was performed to evaluate life cycle costs over a 20-year horizon which includes the cumulative capital and O&M costs associated with each alternative (Figure 7). Key Takeaways This presentation will provide insights on - Impacts of each alternative on the existing solids treatment train - Mass and Energy Balance analysis summary associated with different alternatives - Life cycle cost analysis for each alternative over 20-year planning horizon - Comparison of alternatives based on the following: -- Economic Criteria: Capital and O&M Cost -- Non-Economic Criteria: O&M Complexity, Technology Maturity/Reliability, Health & Safety, Product Application, and Footprint. - Furthermore, driving factors associated with higher costs in noncontiguous state such as Hawaii in comparison to Mainland states will be discussed.

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

SpeakerSivaprasad, Shyam

Presentation time

08:30:00

10:00:00

Session time

08:30:00

10:00:00

SessionTriple Bottom Line of Biosolids Master Planning

Session number21

Session locationBaltimore Convention Center, Baltimore, Maryland, USA

TopicAnaerobic co-digestion, Biomethane, Lipids/proteins/carbohydrates ratio, TWAS, Manure, SSO, Anaerobic Digestion, Biosolids, business case evaluation, Circular Economy, Cogeneration, Funding, Landfill, market diversification, PFAS/Emerging Contaminants, Reliability, Resource Recovery, Thermal Processes, THP

Author(s)

Sivaprasad, Shyam, Moncholi, Manuel, Tse, Yueyun, Sinha, Pooja, Lobo, Steven, Tsuchida, Tyler, Nishikawa, Jaime, Stephens, Heather, Armstrong, Bob

Author(s)S. Sivaprasad1, M. Moncholi 1, Y. Tse1, P. Sinha S. Lobo1, T. Tsuchida2, J. Nishikawa2, H. Stephens1, B. Armstrong1

Author affiliation(s)Stantec, 1Stantec, 1Stantec, 1R. M. Towill Corporation, 2R.M. Towill Corporation, 2

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2025

DOI10.2175/193864718825159781

Volume / Issue

Content sourceResiduals and Biosolids Conference

Word count25

Description: Knock Out, Drag Out Fight: Centrifuge vs. Belt Filter Press - Title for Best...

Knock Out, Drag Out Fight: Centrifuge vs. Belt Filter Press - Title for Best Dewatering Technology to Squeeze the Poop at William. E. Dunn Water Reclamation Facility!

Abstract

BACKGROUND The William E. Dunn Water Reclamation Facility (WEDWRF) is in Pinellas County, Florida and is operated by Pinellas County Utilities to treat wastewater collected from the County's northern service area, and to generate reclaimed water supply for the County's reuse distribution system. The WEDWRF is a 9.0 MGD capacity advanced 5-Stage Bardenpho process wastewater treatment facility that currently operates at an annual average flow of approximately 6.5 MGD. The existing solids management system for the WEDWRF includes two (2) rotary drum thickeners (RDT) for thickening waste activated sludge (WAS), two open top sludge holding tanks, two (2) belt filter presses (BFP) and truck loading bay. The existing BFP are old and require replacement. A pilot scale dewatering study was conducted with the following objectives: 1.Evaluate the dewatering performance of new belt filter press and centrifuge. 2.Optimize the polymer dosage to maximize cake solids and solids capture. 3.The efficacy of generating thickened waste activated sludge (TWAS) using RDT to thicken WAS prior to dewatering or bypass the RDT to directly dewater WAS as an operational, energy and polymer cost saving measure. 4.Analyze composite samples of centrate/filtrate stream for Chemical oxygen demand (COD), Ammonia and Phosphorous to determine the quality of the reject stream back to the headworks. 5.Perform life cycle cost analysis of dewatering operation and maintenance for BFP and Centrifuge. PILOT TESTING SCHEDULE The pilot testing was conducted between April 18, 2023 - June 6, 2023. Alfa Laval's BFP was tested between April 18 - April 20 for WAS, April 25 - April 27 for TWAS. Andritz centrifuge was tested between May 9 - May 11 for WAS, May 15 - May 17 for TWAS. Alfa Laval's centrifuge was tested between May 23 - May 25 for WAS, June 5 - June 6 for TWAS. A filtrate/centrate stream composite sample was collected on each day of pilot testing for both WAS and TWAS. RESULTS 1.Waste Activated Sludge The percent cake solids (%TS) obtained for WAS in Alfa Laval BFP ranged between 16.8-18.5% for the polymer dosage ranging between 10.0-16.8 lb/Ton. The solids capture for BFP was between 95 - 99%. Similarly, the percent cake solids (%) obtained for Andritz and Alfa Laval Centrifuge ranged between 20.0-24.5% for polymer dosage ranging between 14.5-62.9 lb/Ton for Andritz centrifuge and 13.2-35.7 lb/Ton for Alfa Laval centrifuge. The solids capture for Andritz centrifuge ranged between 89-96% and Alfa Laval centrifuge ranged between 94-99%. 2.Thickened Waste Activated Sludge The percent cake solids (%TS) obtained for TWAS in Alfa Laval BFP ranged between 15.8-17.7% for the polymer dosage ranging between 7.3-11.4 lb/Ton. The solids capture for BFP was between 96-99%. Similarly, the percent cake solids (%) obtained for Andritz and Alfa Laval Centrifuge ranged between 18.7-22.7% for polymer dosage ranging between 18.7-44.8 lb/Ton for Andritz centrifuge and 27.0-32.0 lb/Ton for Alfa Laval centrifuge. The solids capture for Andritz centrifuge was between 84-99% and Alfa Laval centrifuge ranged between 94-99%. 3.Centrate/Filtrate Analysis A composite sample of centrate/filtrate was collected on each day of pilot testing for both WAS and TWAS. For WAS centrate stream, the concentrations of COD ranged between 60 - 470 ppm, ammoniacal nitrogen between 0.1 - 0.3 ppm, total phosphorus between 2 - 48 ppm. For TWAS centrate stream, the concentrations of COD ranged between 102 - 2,440 ppm, ammoniacal nitrogen between 0 -150 ppm, and total phosphorus between 133 - 490 ppm. It is noteworthy to mention that the concentration of analytes reported here as received from the contracted laboratory. The key observations in the filtrate/centrate composite sample analysis are: 1.Concentration of the analytes appear to be lower during the belt filter press dewatering operation when compared to the centrifuge dewatering operation. 2.Concentration of analytes for TWAS filtrate/centrate stream appear to be significantly higher than for WAS. This indicates that there is release of nutrients in the holding tank. 3.The P concentration in the filtrate for TWAS appears to be in high enough concentrations that it could lead to the formation of struvite in the facility. This could decrease the dewaterability of the sludge and create maintenance issues, due to buildup in pipes and valves, at the facility. KEY TAKE-AWAYS The pilot testing results indicate that both BFP and centrifuge technology could be suitable for WEDWRF dewatering improvements. The BFP consistently achieved a cake solids concentration of 17.5 (%TS) for WAS. In the case of TWAS, the average percent cake solids were about 17.0 (%TS). Similarly, both the centrifuges performed better than BFP producing cake solids at an average of 22.0-23.0 (%TS) for WAS and 20.0 (%TS) for TWAS. However, the polymer consumption in the case of centrifuge was at least twice as much as BFP polymer consumption for both WAS and TWAS to achieve a 3-5% increase in percent cake solids. The centrate/filtrate composite analysis samples showed interesting observations with high concentrations of nutrients for TWAS. This could be attributed to the release of nutrients in the sludge holding tank. A determination of the exact duration and conditions that would cause this release of nutrients and soluble COD is something the pilot did not focus on. An understanding of the impacts of sludge degradation in sludge holding tanks especially in hot summer months is important for this and many other plants that use sludge holding tanks as buffers to limit plant dewatering operations schedules to only a few days a week. This could also impact the dewaterability of TWAS which was evident as the cake solids (%) obtained in TWAS was relatively lower than WAS. Furthermore, higher nutrient and COD loading in the centrate stream recycled to the headworks of the plant could lead to increase in aeration demands to treat the increased ammonia load . Similarly, there could be an impact in disinfection chlorine demand. To conclude, both BFP and centrifuge should be evaluated for both WAS and TWAS to have a complete understanding of overall life-cycle cost implications on each of those equipment. Life cycle cost analysis will be performed and presented by the time of Residuals and Biosolids Conference in 2024. This presentation will cover the pilot testing equipment operating parameters, feed characteristics, relationship between wastewater sludge cake solids and polymer consumption of dewatering WAS and TWAS, important parameters for plant operations decision making. Furthermore, the presentation touches upon nutrient and COD impacts of dewatering recycle streams and their potential impacts on plant effluent limits. ACKNOWLEDGEMENTS The presenters thank Pinellas County Utilities, Alfa Laval, and Andritz for providing pilot testing equipment trailers and for assisting during the pilot testing phase.

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

Presentation time

14:30:00

15:00:00

Session time

13:30:00

16:45:00

SessionDewatering

Session number05

Session locationOklahoma City Convention Center, Oklahoma City, Oklahoma

TopicBelt Filter Press, Biosolids, Dewatering

Author(s)