Highly Colored Water Removal Using Nanofiltration Membranes at the Colored Water Treatment Facility. Adam Zacheis, Project Manager Carollo Engineers

Transcription

1 Highly Colored Water Removal Using Nanofiltration Membranes at the Colored Water Treatment Facility Adam Zacheis, Project Manager Carollo Engineers

2 Topics 1. Background - Mesa Water District (Mesa) Water Supply 2. Colored Water Characteristics 3. Original Plant and Need for New Technology 4. Membrane Pilot Testing 5. New Facility Processes 6. Public Perception - Benefits to the Consumer 7. Project status

3 Formed in 1960, Mesa Serves an 18 Square Mile Area in Orange County 1. Water supply sources: a. Groundwater b. Imported water c. Recycled water 2. 23,000+ retail accounts a. Costa Mesa b. Newport Beach c. Unincorporated areas Mesa Service Area

4 Mesa s Primary Source of Supply The Orange County Groundwater Basin Santa Ana River Watershed Ontario/Chino San Bernardino Orange County Groundwater Basin Riverside

5 Majority of Groundwater Production is From 300 to 1000-ft Costa Mesa 0 Wells Orange Recharge 700 1,400 2,100 Colored Water 0 miles

6 Mesa Will Treat 8,000 AFY of Highly Colored Water From the Lower Zone MESA CWTF (8,000 AFY) IRWD DATS (8,800 AFY) Orange ,000 1,400 1,000 2,000 2,100 0 miles

7 Colored Water 1. Color from ancient redwood forest 2. Treatment to meet secondary standard = 15 c.u. 3. Removal to 1 c.u.(non-detect)

8 Original Plant and Limitations 1. Ozone and Biological Treatment Plant a. Color increased from 120 to 170 C.U. b. Ozone dose up to mg/l c. Increasing bromate formation/control costs. d. Original Treatment System Became Limited 2. Membrane separation became more economical

9 The Primary Project Driver 1. Migration of color water from deeper aquifers 2. Orange County Water District Requirement a. Water quality program b. Pump more water from lower zones c. Production zone lowered to 600-ft to1000-ft d. Impacts to quality Color increase to CU (exceeds treatment capability of existing system) 3. Facility capacity increase from 4,000 gpm to 6,000 gpm a. Make up for less clear groundwater available

10 Pilot Testing Was Performed to Confirm Design Parameters Water supply: Well 11 at 750-ft depth Pilot Unit: 2 stage system with concentrate recycle Membranes: 4 diameter HYDRACoRe NF Pretreatment: Cartridge filter Scale 1 mg/l

11 Basis of Design Raw Water 1. Treatment Challenges a. High color b. High ph + sulfide c. Low hardness d. Bromide (DBPs)

12 Basis of Design Finished Water Goals 1. Post treatment challenges a. Sulfide and methane removal b. Alkalinity management c. DBP control d. Stabilization

13 Full Scale Processes 1. Raw water Well Nos. 6 and Sand Separators and Cartridge Filters 3. NF System 4. Degasifier and Scrubber System 5. Post Treatment and Pumping 6. Chemical Systems

14 Process Overview

15 Raw Water Filtration and Chemical Addition Conditions Feedwater 1. Sand Separators Used a. Wells have history of sand production b. Auto backwashing sand separators 2. Scale inhibitor added as a protective measure 3. Cartridge filters for provided for final protective barrier

16 Two Primary NF Systems Are the Heart of the Process 1. Primary NF a. Two-stage system with concentrate recycle b. 95% system recovery 2. Benefits of two-stage system with concentrate recycle a. Increased turndown capability b. Simplified piping and instrumentation 3. HYDRACoRe membranes by Hydranautics a. Poor rejection of ionic constituents b. High rejection of color

17 A Secondary NF System Recovers Additional Water 1. Treats primary NF concentrate a. Primary NF concentrate pressure will be boosted by an inline centrifugal pump 2. Increases the overall plant recovery from 95% to 98% recovery 3. Membrane options a. Low fouling traditional NF membranes Nano-BW (Hydranautics) b. HYDRACoRe 50

18 Air Stripping Selected for H2S and Methane Removal 1. NF permeate ph adjusted to below ph ~6.1 by adding CO2 upstream of degasifier a. Converts all sulfide to H2S 2. Counter-current flow with plastic packing media inside the degasifier to increase air-water transfer 3. Offgas treated using single stage chemical scrubber a. Caustic and bleach

19 Alkalinity Recovery is Necessary to Stabilize Finished Water 1. Low finished water hardness a. ph and alkalinity only for corrosion control without supplemental calcium source 2. CO2 at ph < 6.3 is stripped out during H2S/methane removal 3. Carbonate must be added back to the finished water for ph stability and corrosion control 4. Addition of CO2 + caustic soda creates bicarbonate alkalinity in degasified permeate CO 2 Storage And Feed System

20 Post Treatment Pumping 1. Degasifier effluent pumped to existing ground storage (1.25 MG) a. Upstream post-treatment b. Chloramination 2. High Lift Pumps (100 psi) pump from ground storage to distribution system

21 New Treatment Plant Control System 1. Fully automated system 2. Automatic start-up of wells, NF System, and post-treatment systems 3. Data collection and normalization a. Automatic alerts for CIPs b. Historical trending of operational data 4. SCADA output of operational reports and water quality data

22 New Treatment Process 1. Moving to more economical membrane treatment for color removal 2. Hydranautics HydraCoRe50 a. High permeate flux at low pressure b. Strong negatively charged membrane surface c. Chlorine tolerance d. Low salt/high organics rejection e. Low fouling

23 New Building with Improved Operating Environment 1. Key Features a. Pumps separated from process area for noise control b. Mirror image train design used to minimize floor space requirement c. Existing ozone contactor converted to transfer pump station d. Future expansion area arranged to minimize Phase I investment

24 Preliminary Site Rendering Proposed Degasifer and Scrubber Proposed NF Building and Product Transfer Pump Station Existing Chemical Storage and Feed Existing Ground Storage Tank Existing High Lift Pump Station Existing Ozone Generator Building and Administrative Offices

25 Construction Photos - Demolition

26 Construction Photos New Facility

27 Beyond the Process 1. Promote benefits rather than process.

28 Interpretive Landscaping

29 Project Status 1. Final design cost estimate: $23 million 2. Bid Price: $17 million 3. Projected water cost: $354/AF (with subsidy) 4. Project currently under construction 5. Completion in August 2012

30 Thank You