Advanced Oxidation with UV Light and Peroxide for Indirect Potable Water Reuse

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1 Advanced Oxidation with UV Light and Peroxide for Indirect Potable Water Reuse David Murray, Brown and Caldwell Robert Chalmers, CDM Mehul Patel, OCWD October 27, 2010 Pacific Northwest Clean Water Association Annual Conference, Bend, Oregon

2 Topics to Discuss Overview of the Advanced Oxidation Process (AOP) How and why is AOP used for wastewater reclamation and indirect potable reuse? Project examples Orange County Water District/Sanitation District South District Facility/Miami-Dade Water and Sewer Department Summary Questions

3 What is the AOP? AOP is a process for destroying trace organic contaminants in clean water using: UV Photolysis UV Oxidation by hydroxyl radical formation UV Photolysis and hydroxyl radical oxidation are separate photochemical processes that occur simultaneously

4 What is AOP Used in Water/Wastewater Treatment? Taste and odor compound removal (MIB, geosmin) N-nitrosodimethylamine (NDMA) destruction Pesticides and herbicides removal Petroleum additives (MTBE) treatment in groundwater Pharmaceuticals and personal care products removal

5 Electromagnetic Spectrum Disinfection is optimized at a wavelength of 254 nm, but other photochemical processes occur at different wavelengths UV Photolysis UV Oxidation

6 UV Oxidation Reaction Mechanisms UV Photolysis UV light is absorbed by the contaminant and is a physical process: Degradation rate depends on: Quantum yield of UV light energy Molar absorption coefficients of contaminants within the UV range Intensity and spectral distribution of the light source (i.e., lamp type, UV system design) Absorption of water background (UVT) Does not require peroxide addition

7 UV Photolysis

8 UV Oxidation Reaction Mechanisms UV Oxidation (Photo Chemical Process) UV light is first absorbed by hydrogen peroxide, producing hydroxyl radicals: Degradation rate depends on: Intensity and spectral distribution of the light source (i.e., lamp type, UV system design) Absorption of water background (UVT) Hydroxyl radical ( OH ) rate constant H 2 O 2 concentration Hydroxyl radical scavenging demand

9 UV Oxidation Hydroxyl peroxide Hydroxyl radical Chemical bonds are broken by hydroxyl radicals

10 UV and H 2 O 2 : Destroying Water Contaminants UV Oxidation is a contaminant destruction technology versus a phase transfer technology Disinfection is achieved simultaneously Safe (no storage of liquid oxygen or off-gas treatment required) Simple installation and operation Accomplishes treatment of a wide range of trace contaminants not treated by other technologies (e.g., nitrosamines such as NDMA) Small footprint Does not form bromate

11 UV Photolysis and UV Oxidation Balance Hydroxyl peroxide

12 Advanced Treatment Processes

13 AOP in Indirect Potable Reuse (IPR): Function Disinfection (including Cryptosporidium/Giardia) Removal of compounds destroyed by UV Photolysis (e.g., NDMA and other nitrosamines) Removal of compounds destroyed by UV Oxidation (e.g., pharmaceuticals, PCPs, industrial solvents, etc.) An extra measure of protection that builds public confidence in the quality of water Proven success: a number of successful and publicly-accepted IPR systems in the world employ UV Oxidation Cost effective: 3 to 5% of project capital <10% of project O&M

14 AOP Project Examples Orange County Water District (OCWD) Groundwater Replenishment (GWR) Project Fountain Valley, California Completed and in operation since 2008 South District Plant Miami-Dade Water and Sewer Department Miami, Florida Currently in final design based on OCWD experience

15 GWR Project, OCWD Indirect Potable Reuse

16 OCWD Water Facts Orange County s population of 2.5 million will add 700,000 people by the year 2020 Demand for water is expected to increase by 20% Water is 50% from groundwater and 50% imported Imported water from Colorado River will decrease in availability by 2016 Salt water intrusion is a major concern Imports from northern California may be limited

17 GWR Goals Provide up to 144,000 acre-feet of potable water per year ultimately 50% of water for salt water barrier wells 50% for groundwater infiltration basins Water must stay in ground for 1 year before use Reduce groundwater salinity Water will be comparable in cost to imported sources Project construction cost was $425 million

18 Water Factory Facility Replaced by the GRW Project

19 OCWD Area Map Brown and Caldwell

20 OCWD Process Flow Diagram

21 MF, RO and UV Provide Multiple Barriers for Disinfection Microfiltration (MF) Removes suspended solids and most bacteria Reverse Osmosis (RO) Removes Total Dissolved Solids, organics, bacteria and most viruses-2 logs UV Disinfection UV irradiation for primary disinfection of remaining virus- 4 logs Multiple barrier when membranes are breached Photolysis for destruction of NDMA and 1-4, dioxane

22 Why was UV first selected for the GWR system? Effectiveness Better than chlorine for virus inactivation Better than chlorine for Cryptosporidium UV is more environmentally friendly Does not require chlorine addition No disinfection by-products No community safety risk

23 Initial Disinfection Requirements Groundwater Replenishment <2.2 total coliform per 100 ml 50 mj/cm2 UV Dose per NWRI Objective is 4 log MS2 reduction Turbidity <0.2 NTU 95% of Time UV 254 nm >90% Dual feed power source Discharge to Santa Ana River < 2.2 total coliform per 100 ml During infrequent high-flow conditions Microfiltration plus UV disinfection

24 N-Nitrosodimethylamine

25 Interim NDMA Limits in California Interim action level is <20 ng/l Future limit could be <2 ng/l EPA has determined that the maximum admissible limit in drinking water is 7 ng/l, but has not set an MCL yet. It is a suspected human carcinogen. Concentration detected in OCSD secondary effluent was 5 to 300 ng/l Project goal is <10 ng/l NDMA Requires 1.2 log reduction

26 NDMA Removal UV Photolysis/advanced oxidation (AOP) UV dose rate expressed as EEO or energy consumed per order of NDMA removal per 1,000 gallons UV equipment is much larger than for disinfection alone with higher power costs H addition for hydroxyl radical formation

27 Electrical Energy per Order (EEO) Photochemical oxidation of NDMA is first order Energy consumed is same for each order degraded EEO is metric for photochemical/aop degradation Unit is kwh per 1,000 gallons per order removed EEO = EED/ log (c i / c f ) EED = Energy dose in kwh per 1,000 gallons c i = initial NDMA concentration c f = final NDMA concentration

28 Molar Adsorption Spectrum of NDMA Optimum at 228 nm

29 NDMA Removal Disinfection of MF/RO permeate UV transmittance at 254 nm >95% UV transmittance at 228 nm >90% Hydrogen peroxide dose of 5 mg/l Total Suspended Solids: Negligible Energy Dose per Order (EEO) from 0.2 to 0.7 Redundancy to meet Title 22 requirements

30 GWRS Operating Modes Normal Production for Groundwater Replenishment 70 mgd reclamation Wet Weather Operation 70 mgd reclamation 30 mgd discharge to Santa Ana River

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33 In-Vessel UV System Recommended Advantages of In-Vessel UV for GWR: No re-pumping required More compact footprint Easier to control flow Pressurized operation Maintenance crane not required Lower capital cost

34 UV Evaluation Process Types of Lamps Considered: Low Pressure Low Pressure/High Output (LPHO) Medium Pressure

35 Advantages of Prepurchase or Preselection More competition for equipment purchase Allows for selection of most economical system Selection based on life-cycle costs Allows final design to be optimized for selected equipment Defines equipment cost early

36 Trojan Technologies; UV Phox TM 72 Low Pressure/High Output Lamps (260W each)

37 Construction Phase 2004 to 2008 UV Reactor Train Feed Piping

38 GWR Facility Entrance Sign

39 Entrance to the GWR Facility Entrance to GWR Operations Building

40 GWR System Open for Public and Water Industry Tours OCWD encourages public and school tours and has many visitors from other water agencies

41 Screening System Screening required ahead of microfiltration

42 MF Facility In-tank MF configuration

43 MF Facility Connections

44 Reverse Osmosis (RO) RO used to remove inorganic and some organic contaminants

45 Reverse Osmosis 15 trains of 5 mgd capacity each

46 UV Disinfection Equipment installed under open canopy with electrical equipment in a housed area

47 UV Disinfection UV disinfection reactors stacked three high to conserve space in structure

48 UV Disinfection End view of lamp reactors and piping

49 UV Disinfection View of UV reactor trains

50 UV Lamps outside of Reactor Vessel 2 X 72 Lamp assembly and end cap

51 UV Reactor Vessel

52 UV Reactor Lamp connections and addresses

53 Product Water Pumps Designed by Brown and Caldwell

54 Grand Opening January 25, 2008

55 Grand Opening Opening the inlet

56 GWR Product Water Dedication ceremony January 2008

57 SDWRF Project-Miami

58 Pilot Plant Base Design Followed Orange County GWR Project Ammonia Limit Drove IX Process Not Part of GWR

59 Pilot Plant Pilot Plant Efforts

60 Pilot Plant Pilot Plant Objectives Validate Process Performance Optimize the Process Develop Design Criteria Qualify System Manufacturers Provide Confidence to Community and Regulators

61 South District Water Reclamation Facility Miami-Dade Water and Sewer Department Design Criteria Flow rate 21.0 mgd Minimum flow rate 5.25 mgd NDMA inlet concentration 200. ng/l NDA effluent concentration 2. ng/l NDMA Log 10 reduction 2 1,4-Dioxane inlet concentration 10.0 µg/l 1,4-Dioxane outlet concentration 0.5 µg/l MIB removal, Log 10 reduction 0.9

62 Water Reclamation Plant South District Water Reclamation Plant

63 Water Reclamation Plant Pre-purchase efforts Microfiltration System UV Advanced Oxidation System

64 South District Water Reclamation Facility Low pressure high output lamps bid versus medium pressure lamps on a life-cycle basis in May 2010 Equipment bidders were Trojan Technologies and Calgon Corporation Low bidder was Trojan with a cost of $4.1 million and a life cycle of $12.6 million over 20 years Project is in final design at this time

65 Final Thoughts UV used in combination with membranes provides a multi-barrier disinfection solution Disinfection required to meet NWRI guidelines Photochemical destruction of NDMA (<10 µg/l goal) Project completed for $425 million Cost of water about $525 per acre foot Eliminates need for new ocean outfall Reduces aquifer salinity Largest negative is high power consumption

66 Final Thoughts (continued) Provides water supply for 36,000 families Reduces dependence on imported water Removes micro-constituents by AOP Provides salt water barrier injection water Local control helps drought-proof Orange County

67 GWR Awards 2009 IUVA Project of the Year Among its many awards, the GWR System has been honored with the prestigious Stockholm Industry Water Award and the American Society of Civil Engineers (ASCE) 2008 Outstanding Civil Engineering Achievement Award.

68 Groundwater Replenishment Project Questions