Buckhorn Disinfection Byproducts / Backwash Disposal Project Board of Directors Meeting June 14, 2012
Project Purpose and Issues Backwash Management Strategies DBP Reduction Alts and Recommendations Recommended Phasing Plan Presentation Outline
Project Purpose: Assure Compliance with Stage 2 Disinfection Byproduct (DBP) Rule (a) & Develop An Integrated Backwash Management Strategy Key Project Issues: Elevated DBPs in the Buckhorn WTP Distribution System Insufficient Pond 7 Storage Capacity for Backwash Waste Water Disposal Project Purpose and Issues (a) Effective October 1, 2013.
1.Expand Pond 7 to Contain 100-Yr Storm Event per WDR 2.Remove Solids at WTP to allow Recycle to WTP and/or Discharge Treated Backwash Water (BWW) to Pond 7 a)No WDR Required 3.Select Best Long-Term and Most Cost Effective Backwash Water Management Strategy Backwash Water Management Strategies for the Buckhorn WTP
Comparison of Solids Removal Alternatives Alternative Comparison Criteria (Score 1 to 5, 5 = best) Score Regulatory Construction Cost Applicability ParticulateChemical ComplianceRemovalCompatibility 1. Bag Filter w / Recycle3 5 ($255k) Bag Filter w / Discharge2 1 ($760k – $910k) Mech. Dewatering w / Recycle3 3 ($525k) Mechanical Dewatering w / Discharge2 2 ($660k) Conventional Drying Beds3 1 ($1,525k) (site constraints) 6. Proprietary Drying Beds5 4 ($355k) Reuse Old Plant (Conv. Drying Beds)3 1 ($1,515k) Leachfields1 5 ($200k) Micro Screen3 2 ($595k – $900k) Expand Pond4 3 ($500k - $650k)35520
Proposed Flow Schematic
Potential Site Layout Recommended Deskins TM System (Solids Removal and Dewatering)
Stage 2 DBR Rule Compliance Historical TTHM/HAA5 Results
TOC Removal Coagulation/Filtration Adsorption Oxidation Reduce Chlorine Dose Maintain Disinfection CT Maintain Residual Disinfectant throughout System Distribution System Modifications Reduce Water Age Tank Materials DBP Removal Strategies
Buckhorn WTP Distribution System DBP Sample Location
Comparison of DBP Reduction Alternatives DBP Reduction Alternative Capital Cost (1-5, 5 = Lowest) Operating Cost (1-5, 5 = Lowest) DBP Reduction (1-5, 5 = Greatest) Complexity (1-5, 5 = Simplest) Total Score TOC REMOVAL Chlorine Dioxide 2 ($180,000) 1 ($30,000/yr) ACH 4 ($25,000) 3 ($20,000/yr) Ferric Chloride 3 ($45,000) 2 ($25,000/yr) REDUCE CHLORINE RESIDUAL Clearwell Baffling/ Chlorine Booster Stations 1 ($160,000) 3 ($20,000/yr) pH Adjustment Location 4 ($20,000) 5 ($0/yr) Reduce CT Provided 5 ($0) 5 ($0/yr) DISTRIBUTION SYSTEM MODIFICATIONS Tank Mixing 3 ($175,000) 5 ($0/yr) 24 14
ACH DBP Reduction
Recommended Phasing Plan Goal: ACH feed system operational Summer 2013; highest DBP concentrations have historically occurred during summer season a Step / ActivityEst. Construction Cost ($) JJASONDJFMAM 1. Solids Removal Project355,000 DesignBConstruct & Startup 2. Full Scale Testing to Minimize Chlorine Dose 0b0b 3. Tank A Modifications50,000 DBConstruct 4. ACH Improvements25,000 DBC & SU Total Est. Construct Cost430,000 a First set of Stage 2 DBP compliance testing to be conducted prior to October 1, 2013 b Testing conducted by Agency operators and staff
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