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Pilot Testing for Hexavalent Chromium Removal

Prepared for

Cadiz, IncOctober 2016

CH2M III

Contents Section Page

Acronyms and Abbreviations ............................................................................................................. vi

Executive Summary ............................................................................................................. 1-1 1.1 What is the Cadiz Water Project? .................................................................................... 1-1 1.2 How Widespread is Hexavalent Chromium in Water? .................................................... 1-1 1.3 How is Chromium Removed from Drinking Water? ........................................................ 1-1 1.4 How does the RCF process work? .................................................................................... 1-2 1.5 Is there much experience with the RCF Process? ............................................................ 1-2 1.6 What is the treatment technology being investigated at Cadiz? .................................... 1-3 1.7 What does the Treatment System Cost for Hexavalent Chromium and Arsenic

Removal? ......................................................................................................................... 1-5

Cadiz Water Project ............................................................................................................ 2-1 2.1 Introduction and Background .......................................................................................... 2-1 2.2 Conceptual Project Overview .......................................................................................... 2-1 2.3 Groundwater Quality ....................................................................................................... 2-2

Hexavalent Chromium and Arsenic in Groundwater ............................................................. 3-4 3.1 Introduction ..................................................................................................................... 3-4 3.2 Hexavalent Chromium Occurrence .................................................................................. 3-4 3.3 Hexavalent Chromium Water Quality Regulations .......................................................... 3-5

3.3.1 Federal Regulations ............................................................................................ 3-5 3.3.2 California Regulations ......................................................................................... 3-5

3.4 Treatment Alternatives for Hexavalent Chromium ......................................................... 3-5 3.4.1 In Situ Treatment .............................................................................................. 3-5 3.4.2 Ex-Situ Treatment ............................................................................................... 3-6

3.5 Arsenic Occurrence .......................................................................................................... 3-8 3.5.1 Arsenic Removal Treatment Alternatives ........................................................... 3-8 3.5.2 Conventional Filtration for Arsenic Removal ...................................................... 3-9 3.5.3 Potential for Simultaneous removal of Hexavalent Chromium and Arsenic .... 3-10 3.5.4 Proposed Treatment System for Pilot Testing .................................................. 3-11 3.5.5 Water Treatment Residuals .............................................................................. 3-17

Pilot Testing methods and Materials Groundwater Quality .................................................. 4-1 4.1 ATEC Pilot Equipment ...................................................................................................... 4-1

Pilot Testing Results ............................................................................................................ 5-1 5.1 ATEC Testing Objectives and Findings ............................................................................. 5-1

5.1.1 ATEC Testing Scenario 1 ...................................................................................... 5-1 5.1.2 ATEC Testing Scenario 2 ...................................................................................... 5-2 5.1.3 ATEC Testing Scenario 3 ...................................................................................... 5-4 5.1.4 ATEC Testing Scenario 4 ...................................................................................... 5-4

5.2 ATEC Overall Testing Results ........................................................................................... 5-6 5.2.1 Arsenic and Chromium Removal ........................................................................ 5-7 5.2.2 Iron Removal ..................................................................................................... 5-14

5.3 Filter Run Lengths .......................................................................................................... 5-15 5.4 ATEC Backwash Water Results ....................................................................................... 5-16

CONTENTS

Section Page

CH2M IV

Conceptual Design of Facilities ............................................................................................ 6-1 6.1 Summary .......................................................................................................................... 6-1

6.1.1 Treatment System Options ................................................................................. 6-1 6.1.2 Water Delivery Options ...................................................................................... 6-1

6.2 Water Quality Standards.................................................................................................. 6-2 6.3 Conceptual Design Using ATEC System............................................................................ 6-3

6.3.1 ATEC System Operation and Design Criteria ...................................................... 6-4 6.4 Backwash Waste Flow Handling ...................................................................................... 6-5

Cost Estimates .................................................................................................................... 7-1 7.1 Costs for ATEC Systems Treatment .................................................................................. 7-1 7.2 Cost per Acre Foot ........................................................................................................... 7-2

References .......................................................................................................................... 8-1

Tables

Table 1-1. Pilot Testing Treatment Results for ATEC Treatment System................................................... 1-5 Table 2-1. Summary of General Water Quality Parameters from Cadiz Wells .......................................... 2-3 Table 2-2. Preliminary Water Treatment Target Constituents .................................................................. 2-3 Table 3-1. Treatment Alternatives for Hexavalent Chromium .................................................................. 3-6 Table 3-2. Comparison of Arsenic Removal Technologies ......................................................................... 3-8 Table 3-3. Surveyed Systems ATEC Iron and Manganese Facilities ......................................................... 3-11 Table 3-4. Comparison of Pilot Removal Efficiency and Full Scale Removal Efficiency in Manganese Dioxide Media Filters ............................................................................................................................... 3-12 Table 3-5. Project Construction Components for Surveyed ATEC Water Treatment Systems ................ 3-14 Table 3-6. Capital Costs of ATEC Water Treatment Surveyed Systems, Escalated to 2016 Dollars ........ 3-15 Table 3-7. Annual Operations and Maintenance Costs Report for ATEC Systems, in 2016 dollars ......... 3-16 Table 4-1. Physical Characteristics of Filter Tanks and Media ................................................................... 4-3 Table 4-2. Pipe Configurations for Varying Contact Times ........................................................................ 4-4 Table 5-1. Pilot Testing Treatment Results for ATEC Treatment System................................................... 5-7 Table 6-1. Maximum Design Flow Rates .................................................................................................... 6-2 Table 6-2. Estimated Backwash Waste Volumes, mgd .............................................................................. 6-5 Table 6-3. Dry Weight Solids Produced Per Year ....................................................................................... 6-5 Table 7-1. CAPEX Estimates for ATEC System for 10-month Operating Period ......................................... 7-1 Table 7-2. CAPEX Estimates for ATEC System for 11-month Operating Period ......................................... 7-1 Table 7-3.OPEX Comparison for Treatment Systems................................................................................. 7-1 Table 7-4: Cadiz Treatment Costs Per Acre-Foot ....................................................................................... 7-2

Figures

Figure 1-1. Hexavalent Chromium Removal with Reduction/Coagulation/Filtration (RCF) Process ......... 1-2 Figure 1-2. Hexavalent and Total Chromium Concentrations from 2005 through 2012 after Microfiltration ..........................................................................................................................

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