Buckhorn Disinfection Byproducts / Backwash

Disposal Project

Board of Directors MeetingJune 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 WaterManagement Strategy

Backwash Water Management Strategies for the Buckhorn

WTP

Comparison of Solids Removal Alternatives

Alternative

Comparison Criteria (Score 1 to 5, 5 = best)

ScoreRegulatory Construction Cost

ApplicabilityParticulate Chemical

Compliance Removal Compatibility

1. Bag Filter w / Recycle 35

($255k) 1 1 5 15

2. Bag Filter w / Discharge 21

($760k – $910k) 3 1 5 12

3. Mech. Dewatering w / Recycle 33

($525k) 1 1 1 9

4. Mechanical Dewatering w / Discharge 22

($660k) 1 1 5 11

5. Conventional Drying Beds 31

($1,525k) 3 5 416 (site

constraints)

6. Proprietary Drying Beds 54

($355k) 5 5 4 23

7. Reuse Old Plant (Conv. Drying Beds) 31

($1,515k) 2 5 4 15

8. Leachfields 15

($200k) 1 5 5 17

9. Micro Screen 32

($595k – $900k) 2 3 5 15

10. Expand Pond 43

($500k - $650k) 3 5 5 20

Proposed Flow Schematic

Potential Site Layout

Recommended DeskinsTM 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)

3 3 10

ACH4

($25,000)3

($20,000/yr)4 5 16

Ferric Chloride

3($45,000)

2($25,000/yr)

3 3 11

REDUCE CHLORINE RESIDUAL

Clearwell Baffling/Chlorine Booster Stations

1($160,000)

3($20,000/yr)

5 2 10

pH Adjustment

Location

4($20,000)

5($0/yr)

3 5 17

Reduce CT Provided

5($0)

5($0/yr)

3 5 18

DISTRIBUTION SYSTEM MODIFICATIONS

Tank Mixing3

($175,000)5

($0/yr)2 4 14

ACH DBP Reduction

Recommended Phasing PlanGoal: ACH feed system operational Summer

2013; highest DBP concentrations have historically occurred during summer seasona

Step / Activity Est. Construction Cost ($)

2012 2013

J J A S O N D J F M A M

1. Solids Removal Project

355,000 Design B Construct & Startup

2. Full Scale Testing to Minimize Chlorine Dose

0b

3. Tank A Modifications

50,000 D B Construct

4. ACH Improvements 25,000 D B C & SU

Total Est. Construct Cost

430,000

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

Questions ?