Why THP Made Sense for TRA June 16, 2016
Central Regional Wastewater System Treatment Plant (CRWS) CRWS Solids Treatment Area 2
162-mgd ADF permitted and 125- mgd average daily flows Pre-THP Solids Process: Gravity thickening (Primary) DAFTs and GBTs (WAS) Blending Dewatering BFPs and Plate-and-frame press Lime stabilization CRWS Overview
TRA Solids Management Goals Produce Class A biosolids Minimize volume of biosolids Ensure redundancy and reliability Optimize use of existing structures Leverage potential markets for biosolids Maximize resource recovery
Solids Management Improvements 2011 Solids Master Plan recommendations Phase I: thickening and screening improvements Phase II: dewatering improvements Phase III: THP/digestion improvements Phase IV: additional digester and thickening for 2040 needs
Why THP made Sense for TRA Overall lowest life cycle cost Minimize volume of biosolids leaving the plant Minimize digester volume to build Produce Class A biosolids Optimize use of existing structures Leverage potential markets for biosolids in future Potential for resource recovery
Thermal Hydrolysis In Thermal Hydrolysis, sludge is heated and pressurized to make organic solids more readily biodegradable.. In other words, it s a pressure cooker. Before After
Thermal Hydrolysis Process (THP) Process gases (to digester) Raw sludge 14-18% DS REACTOR Recycled Steam 97 o C 1.5 hr PULPER 165 o C 6 bar 20 min homogenized sludge 11 bar hydrolyzed sludge steam 1.5-2 bar 102 o C 1.5 hr FLASH TANK to Digester 8-12% DS
Batch Testing Summary Testing conducted at Virginia Tech University Determined thermal hydrolysis would be an effective process for TRA 9 to 10% increase in VS destruction Ammonia production is not inhibitory, even at 42 o C, resulting in lower cooling costs Low odor product can be expected Almost 10% increase in solids concentration after dewatering Results are similar to previous testing for DC Water s Blue Plains WWTP
Proposed Solids Handling Process Primary Thickening Pre- Dewatering Biogas Dewatering Class A Land Application Solids Screening Thickening Thermal Hydrolysis Mesophilic Digestion Landfill Compost WAS Soil Amendment
Planned THP Facilities 3 thermal hydrolysis units and boiler system Heat exchangers and cooling towers 3 new digesters and digester building New pre-dewatering centrifuges, pumps, and polymer Rehab 2 existing digesters for blending/storage Chemical treatment for struvite prevention Dewatered biosolids storage and conveyance Gas pretreatment for boiler use and disposal Odor control
PHASE I Construct GT 7 Construct Primary Sludge Pump and Screening Station PS 15 (without screens) Install 2, 2-M Gravity Belt Thickeners Decommission Dissolved Air Flotation Thickeners Construct Odor Control Facility 15 New Decommission Demolish Rehabilitate Completed in Prior Phase
PHASE II Replace Elevator Rehab 3 existing BFPs Rehab lime silo roof Expand PS15, add screens Replace FP 3 with 2 new BFPs Odor control, electrical, OIP, bidding Demo Dissolved Air Flotation Thickeners New Decommission Demolish Rehabilitate Completed in Prior Phase
Project Implementation Phase I: low-bid contract in construction until spring 2016 Phase II: low-bid construction contract awarded August 2015 Phase III: final design in progress CMAR delivery method final completion expected December 2018 commissioning complete by July 2019 Phase IV: begin after Phase III complete
CMAR Procurement Overview Why Construction Manager at Risk (CMAR)? Design collaboration/quality Accelerated Schedule Cost Control Request for Qualifications Request for Proposals Contract Negotiation Board Approval First CMAR for TRA
Solids Phase III Progress CMAR contract Awarded at August 2015 Board Meeting GMP1 approved December 2015 GMP2 negotiations ended May 2016 Final completion potentially 2019 Commissioning completion 6 months after
Questions?