UV/Chlorine AOP for Potable Reuse: Lower Cost Option Keel Robinson, North America Water Reuse Leader

Transcription

1 Water Reuse in Texas San Marcos, TX UV/Chlorine AOP for Potable Reuse: Lower Cost Option Keel Robinson, North America Water Reuse Leader June 15 th, 2016

2 Agenda AOP 101 UV-AOP for Potable Reuse UV-AOP Design Considerations First Full-Scale UV/Cl 2 AOP Design 2

3 AOP 101

4 What is AOP? Advanced oxidation processes (AOPs) are technologies that generate hydroxyl radicals (OH ) Technology and/or Chemicals OH The goal of an AOP technology is to maximize the production of hydroxyl radicals (OH ) to provide fast reaction kinetics to most efficiently destroy specific contaminants at the lowest possible cost Organic Compounds OH H 2 O Intermediate OH Compounds H 2 O CO 2 4

5 Why Do We Need AOP? Some compounds are not strippable, adsorbable, or biodegradable. Some of these compounds are regulated (either at a federal level or state level) or are candidates for future regulations. AOP is often the best solution to destroy these types of compounds of concern. Contaminant of Concern Typical Source Regulated? 1,4-Dioxane NDMA Atrazine MIB & Geosmin Endocrine Disrupting Compounds (EDCs) Pharmaceutical and Personal Care Products (PPCPs) Industrial Micropollutantsincluding VOCs Solvent stabilizer, found in groundwater from past industrial releases Found in groundwater from past industrial releases, or formed in wastewater plants Herbicide, found in surface water bodies from agricultural runoff Taste & odor compounds found in drinking water from algal blooms Found in wastewater from human use Found in wastewater from human use Chlorinated Solvents, Petroleum Hydrocarbons, Fuel Additives, Phenols Yes (some states) Yes (some states) Yes No, but a nuisance to customers No, but under consideration No, but under consideration Yes 5

6 Common AOP Technologies Ozone + Peroxide UV + Peroxide UV + Chlorine Excellent for a majority of AOP applications due to highly efficient generation of hydroxyl radicals Ideal for NDMA, excellent for low concentrations of contaminants in RO effluent At low ph, chlorine reacts with UV to create hydroxyl and chlorine radicals. In some cases, may be more costeffective and implementable than peroxide. ALSO, OZONE AND OZONE WITH BIOLOGICALLY ACTIVE FILTRATION CAN BEHAVE AS AN EFFECTIVE AOP 6

7 Typical AOP Applications (examples) Groundwater Remediation/Wellhead Treatment (industrial micropollutants) Well From Contaminated Aquifer Air Stripper (optional) AOP Granular Activated Carbon (optional) Drinking Water/Surface Water Treatment (taste & odor compounds) Sedimentation Filtration Disinfection and AOP End of Pipe (industrial waste discharge, recalcitrant contaminants) Industrial Wastewater Treatment AOP Potable Reuse(1,4-Dioxane, NDMA, CECs) Filtered Secondary WW Effluent Membrane Filtration (MF, UF) Reverse Osmosis AOP 7

8 UV-AOP for Potable Reuse

9 Why Do We Need UV-AOP for Potable Reuse? Regulations for Indirect Potable Reuse California Groundwater Recharge Regulations (Full Advanced Treatment) o Section (Requires Reverse Osmosis and Oxidation Treatment Process) o 0.5 log removal of 1,4-Dioxane as an AOP surrogate because it partially passes through RO and is recalcitrant Big Spring, TX (TCEQ case-by-case) NDMA Commonly found in tertiary wastewater and partially passes through RO California Notification Level (10 ng/l) UV-based AOP more effective than O 3 -based AOP at NDMA removal Multiple Barrier Treatment Treatment redundancy to protect environment and human health Low molecular weight compounds (NDMA, 1,4-Dioxane, and CECs) pass through RO UV-based AOP provides pathogen barrier with maximum disinfection credit 9

10 Full Advanced Treatment Train Indirect Potable Reuse (typical FAT) Secondary or Tertiary Effluent Membrane Filtration Reverse Osmosis UV AOP Environmental Buffer This treatment train is ideal for UV-based AOP because RO produces a high quality effluent High UVT (>95%) reduces power demand of UV reactor Low DOC and alkalinity reduce scavengers, more efficient contaminant removal Other treatment trains are possible with oxidation processes such as Ozone or O3-BAF Ozone-based processes are very effective at removing a majority of trace organic contaminants (TOrCs) May be used as pretreatment to membranes and UV AOP May displace membranes and/or UV AOP 10

11 UV-AOP Design Considerations

12 Importance of Treatability Testing Bench-Scale Testing Quick and inexpensive, great screening and preliminary design tool Snapshot-in-time, but useful if water sample is representative of design conditions UV Collimated Beam Testing Dose-response curves Pilot-Scale Testing Optimize process under a range of real-life conditions Optimize equipment sizing variables Scale-up tool for full-scale design and performance guarantee Demonstration-scale for operators Regulatory and public acceptance 12

13 Dose-Response Curve LOG reduction (Pilot reactor) Log reduction Dose-response curve (CBD-Test) UV dose [J/m²] 13

14 Design and Operation of UV Reactor: Dose vs. EED Dose = I * t EED = P [ kw ] 60 * Q [ gpm ] UV Dose Setpoint Independently measured and verified through Collimated Beam Testing Provide a common design basis for all manufacturers Can be usedto scale up Ensures regulatory compliance whenusing validated dose equation (PSS) and on-line sensors Allows for energy savings byturning down power to lamps when conditions change Electrical Energy Dose (EED) Setpoint Does not directly measure UV output of lamps Specific to a reactor type Difficultto scale unless same reactor used for both pilotscale and full-scale Good parameter for comparing power efficiencyof different UV reactors and different operating conditions, but not measuring output of lamps May waste energy when conditions change 14

15 Validate Performance With Collimated Beam Testing Contaminant or Surrogate Spiking Collimated Beam Testing Device UV Dose and Log Removal Comparison RO Permeate Pilot-or Full-Scale UV Reactor H 2 O 2 or NaOCl UV Dose may be calculated via Point Source Summation (PSS) Method 15

16 Why PSS for AOP Applications? PSS equation developed through extensive validation testing of UV reactors by 3 rd party consultant PSS, CFD, and RED are different methods for calculating the average UV dose PSS accounts for real-time sensor inputs such as flow rate, UVT, and UV intensity Flow Rate (MGD) K (with 12600W lamps per row, 17 rows) UVT (%) PSS (mj/cm 2 ) CFD (mj/cm 2 ) RED (mj/cm 2 ) PSS calculation method is validated by CFD and RED 16

17 UV Dose Control S = UV intensity sensor reading (per row) P = ballast power (same to each lamp) INPUTS UVT = UV transmittance Number of rows on OUTPUTS Q = Flow Rate PLC 17

18 CBT Dose vs. PSS Dose LP UV/H 2 O 2 AOP 1,4-Dioxane Removal CBT vs. Pilot-Scale UV Reactor 5 ppm H 2 O 2 Log Reduction Collimated Beam Dose PSS Dose from Pilot UV Dose mj/cm 2 18

19 Upscaling and Sizing with UV Dose The reactor data and PSS model are validated using CBT data ideally generated in parallel on site The reactor UV dose is calculated in real-time based on the measured flow rate, UVT, and UV intensity The dose-response curve is used for upscaling using the same PSS approach with full-scale reactor 19

20 UV/H 2 O 2 AOP For Potable Reuse Has Been The Status Quo Has historically been the standard AOP technology for groundwater recharge/indirect potable reuse in California with multiple successful installations in operation today (e.g. Orange County, West Basin, WRD, Big Spring) Also used in drinking water for taste & odor and in groundwater remediation applications Hydrogen peroxide is relatively expensive and not readily used at WWTPs The photolysis of hydrogen peroxide is inefficient as only about 10% of the chemical is consumed in the UV AOP reaction; thus, incurring significant residual quenching costs 20

21 Introducing UV/Cl 2 AOP Recent academic research shows that UV/Cl 2 AOP is effective at low ph 21 Watts, M. & Linden, K., Chlorine Photolysis and Subsequent OH Radical Production During UV Treatment of Chlorinated Water. Water Res., 41:13:2871 Watts, M., Rosenfeldt, E,. & Linden, K., Comparative OH Radical Production Using UV-Cl2 and UV-H2O2 Processes. Jour Supply Water Res Technol - AQUA., 56:8:469 Watts et al Low pressure UV/Cl2 for advanced oxidation of taste and odor. Journal-AWWA Reverse osmosis for FAT produces a low ph permeate (~5.5) Sodium hypochlorite (chlorine) is readily used at most WWTPs Use of sodium hypochlorite may result in significant life cycle cost savings relative to hydrogen peroxide Residual chlorine may be desirable for additional pathogen credit and/or secondary disinfection First greenfield full-scale system under construction by City of Los Angeles

22 UV/Cl 2 AOP for Reuse Chemistry Considerations 22 Chloramines and Breakpoint Reactions Residual chloramines may be present in RO permeate prior to hypochlorite addition ph and Chlorine Speciation Lower ph favors free chlorine in hypochlorous acid form (slow hydroxyl radical scavenger) Higher ph shifts free chlorine to hypochlorite ion form (rapid hydroxyl radical scavenger) Disinfection by-product formation THMs/HAAs Chlorate Ref: Hach Target ph and free chlorine residual at inlet to UV reactor

23 Terminal Island Water Reclamation Plant

24 LASAN TIWRP AWPF AOP Design 5 MGD to 12 MGD expansion, converting chloraminationto comply with groundwater recharge regulations 18 month bench and pilot scale study including O3/H2O2, UV/H2O2, and UV/HOClled by LASAN, Trussell Technologies, and Carollo Engineers Selected UV/HOClbased on performance and life cycle costs Awarded AOP system to Xylem/Wedeco, startup expected in late 2016 AOP Design Basis: 3 to 12 MGD TOC < 0.25 mg/l UVT >96% CA Groundwater Recharge Regulations AOP Specifications: 6-log virus credit 0.5 log 1,4-Dioxane removal <10 pptndma in effluent UV dose = 920 mj/cm2 Free chlorine dose = 2-4 mg/l UV Dose is the design and operational basis, not EED First Ever UV/Cl 2 AOP Full-Scale Design 24

25 Wedeco MiPRO AOP Pilot System Containerized with climate control (HVAC), lighting, sink, and refrigerator Fully automated with PLC and Operator Interface Remote Monitoring & Datalogging Can run operate in various modes of operation including Ozone only, UV only, Ozone with Peroxide (AOP), UV with Peroxide (AOP), and UV with Chlorine (AOP) State-of-the art instrumentation 25

26 Terminal Island Treatability Testing Objectives 12 month pilot study to compare 6 different AOPs UV LP + H 2 O 2 UV LP + NaOCl UV MP + H 2 O 2 UV MP + NaOCl Ozone + H 2 O 2 H 2 O 2 + Ozone 26

27 27 Bench and Pilot Scale Results

28 Investment Decision: Chemical Savings $3.3M in chemical savings over 20 years NaOCl already on-site Additional pathogen barrier/credit with Cl 2 for FAT UV/Cl 2 AOP selected 28

29 Investment Decision: Real-Time Energy Savings UV Dose control reduces power usage Allows for variable power control to optimize power consumption and ensure regulatory compliance Q [gpm] UVT [%] UV Dose [mj/cm 2 ] EED [kwh/1000gal] Power Savings [%] Log removal of 1,4-Dioxane > > >0.5 29

30 Wedeco Full-Scale UV Reactor WedecoK143 Series LP UV Reactor Validated for 6-log virus removal 12 lamps per row 17 rows of lamps 1 UV intensity sensor per row 600W lamps 34:1 linear power turndown Low headloss Add more rows for linear expansion 30

31 Acknowledgments on TIWRP Project RoshanakAflaki, Ph.D, P.E., Plant Manager, Water Reclamation Division Donald C. Tillman and Los Angeles-Glendale Water Reclamation Plant 31

32 The End of Our Presentation Thank You! Questions? Keel Robinson 32