Potable Water Reuse: Salient Features of an Environmental or Engineered Buffer Gary Amy, Joerg Drewes, Thomas Missimer Water Desalination and Reuse Center  King Abdullah University of Science and Technology Kingdom of Saudi Arabia

Categories of Reuse Definition Of Reclamation: Treatment for Reuse Planned/Intentional vs. Unplanned/Unintentional Reuse (e.g., Effluent-Dominated Rivers or Lakes) Potable vs. Non-Potable Reuse Non-Potable Reuses: Agricultural Irrigation  Crops Intended for Human Consumption (raw versus cooked)  Animal Crops Urban (Landscape/Golf Course) Irrigation Industrial Cooling and Process Water Groundwater Recharge or Injection Potable Reuse Indirect Potable Reuse (IPR), via an Environmental Buffer Direct Potable Reuse (DPR), Pipe-to-Pipe, via an Engineered Buffer?

Categories of Reuse - cont Primary Uses of Recycled Water (reclaimed wastewater) Agricultural Reuse  Constrained by location of use, seasonality, need for dual (purple pipe) distribution system, need for possible winter storage Industrial Reuse  Constrained by location of use, varying quality requirements, need for dual distribution system and storage Landscape Irrigation  Constrained by dispersed nature of demand Groundwater Recharge  Intent may vary (e.g., controlling salt water intrusion in coastal aquifers) but represents a salient feature of indirect potable reuse Unplanned, Unintentional Potable Reuse Widely Practiced Globally  Need to Move to Planned, Intentional Potable Reuse

Water Quality (not Water History) as Driver for Safe Water Reuse (Asano, 2006) Singapore: NeWater

Potable Reuse Constraints and Opportunities Water Quality Issues: (Secondary) WW Effluent Elevated Levels of Organic Matter (DOC) Effluent-Derived Organic Micropollutants (PhACs, EDCs, WW DBPs) Emerging Pathogens (e.g., new strains of E. Coli) Attributes of WW Effluent as a DW Source Proximity of Source RO in WW reclamation/reuse: Lower unit cost for WWRO than SWRO Range of Treatment Options Advanced Processes (membranes, oxidation, UV disinfection, adsorption) Natural Systems (aquifer recharge and recovery (ARR)) Direct (DPR) vs. Indirect Potable Reuse (IPR) Environmental Buffer (e.g., Aquifer Recharge and Recovery, ARR) in IPR

Indirect Potable Reuse Reservoir Wastewater WW Reclamation Plant e.g., Occaquan Reservoir, Virginia USA DW Treatment Plant Consumer

Indirect Potable Reuse WW Reclamation Plant Wastewater Surface spreading or injection e.g., California and Arizona Sites USA DW Treatment Plant Consumer Soil Passage (ARR)

Direct Potable Reuse Wastewater Consumer WW Reclamation Plant Pipe-to-Pipe e.g., Windhoek, Namibia (O3, UF, etc.) DW Treatment Plant Consumer

e.g., Big Springs, Texas (planned) Direct Potable Reuse Wastewater WW Reclamation Plant Pipe-to-Pipe e.g., Big Springs, Texas (planned) DW Treatment Plant Consumer

e.g., Cloudcroft, New Mexico Direct Potable Reuse Wastewater Post-Storage Treatment WW Reclamation Plant Engineered (Storage) Buffer Pipe-to-Pipe e.g., Cloudcroft, New Mexico (planned) DW Treatment Plant Consumer

Advanced Treatment Processes for Potable Reuse Advanced Disinfection (UV Irradiation) Difficult to Inactivate Microbes/Pathogens Constraint: Some UV-Resistant Viruses Oxidation (Ozonation, Advanced Oxidation) Organic Micropollutant (OMPs) Constraint: Metabolites (by-products) Adsorption (Activated Carbon, Iron Oxides) Organic Micropollutant (OMPS) and Inorganic Micropollutants (trace metals) Constraint: Polar OMPs Membrane Separation (ultra- and nano-filtration) (Physical) Removal of Microbes and OMPs Constraint: Removal of Small Microbes or OMPs Aquifer Recharge and Recovery (ARR)  An Advanced Process!

Where Can Advanced Processes Play a Role in Direct or Indirect Potable Reuse? Direct Reuse Advanced WW Treatment Barrier (after Conventional WWT) Advanced DW Treatment Barrier (after Conventional DWT) Indirect Reuse Advanced WWT before Environmental Buffer e.g., GW Injection after RO (OCWD GWRS in California USA) Advanced DWT after Environmental Buffer e.g., RO after GW Recovery (Fouling Potential Reduction by Soil Passage) Environmental Buffer (e.g., ARR) as an Advanced WWT/DWT Process

Indirect Potable Reuse (IPR)

IPR Concept Pre-Treatment Environmental Buffer Post-Treatment  Conventional WW Treatment  Advanced WW Treatment  Groundwater Aquifer  Surface Reservoir  Conventional DW Treatment  Advanced DW Treatment

The Water Industry Standard for to Indirect Potable Reuse e.g., California (OCWD) Microfiltration (or MBR) Disinfection Secondary treatment Tertiary filtration MAR (Direct Injection or Infiltration) ? AOP Reverse Osmosis

Environmental “Buffers” Inherent Component of Indirect Reuse Aquifer or Reservoir as Environmental “Buffer” Short-Circuiting? Retention Time (e.g., 6 months  Die-Off of Viruses % Reclaimed Water  Recycled Water Contribution (RWC) Storage vs. Treatment? Synergistic Hybridizations ARR  Membranes (NF or RO) Lowered membrane fouling (ARR pretreatment) Secondary barrier for organic micropollutants Oxidation  ARR Biodegradation of oxidation metabolites

Aquifer Recharge and Recovery (ARR) for Wastewater Reclamation Wastewater treatment plant effluent Post-treatment Pre-treatment Aquifer Recharge Recovery Primary Secondary Tertiary/Advanced None Oxidation (O3 , AOP) Membrane Filtration (MF) UF (viruses) NF (trace organics) Post disinfection (Chlorination or UV) (Depends on intended use of reclaimed water) Process conditions Residence time Travel distance Redox, HLR

ARR: Infiltration to Recovery (Cikurel, 2004)

Aquifer Recharge and Recovery (ARR): Variations on a Theme ARR = Aquifer Recharge and Recovery (injection well or infiltration basin  recovery well) - ASR = Aquifer Storage and Recovery - ASTR = Aquifer Storage Transfer and Recovery ARR (infiltration basin) Options for Management of Travel Distance, Travel (Residence) Time, Redox  Suitable (Geo)Hydrology and Storage ? Dissolution of Natural Contaminants (e.g., As) ?

Water Quality Benefits of ARR: Removals of… Turbidity Dissolved Organic Carbon (DOC) Bacteria, Protozoa, and Viruses Organic Micropollutants (OMPs) Pesticides Pharmaceutically Active Compounds (PhACs) Endocrine Disrupting Compounds (EDCs) Personal Care Products (PCPs) Nitrogen (ammonia and nitrate) Multi-Objective (-Contaminant) Process:  Potentially, A Total Treatment System Biologically-Driven  Sustainable

Detergents, NPEO, NP, OPEO, OP Performance of Drinking Water Treatment Processes for Removal of PhACs and EDCs (Janex-Habibi, 2007) Process Acidic compounds Neutral compounds X-ray contrast media Antibiotics Estrogens, EE2 Detergents, NPEO, NP, OPEO, OP Riverbank filtration 50 - >90% <10% 50 - 90% >90% Flocculation <20% 10 - 50% Ozonation 10 - >90% GAC, PAC PAC/UF NF UV 40 - 90% Chlorine <10 - 90% Chlorine dioxyde <10 - >90% RO and GAC: Poor Retention of low MW polar compounds (e.g., NDMA) AOP: Slow Oxidation of Chlorinated Flame Retardants

Organic Micropollutant OMP (%) Removals (Snyder et al, 2007) NDMA, 1-4 dioxane RBF GAC NF RO O3 AOP UV-H2O2 acetaminophen 99 80 50 97 androstenedione 85 96 caffeine 98 89 carbamazepine 13 88 DEET 91 70 95 76 82 diazepam 65 93 diclofenac 45 dilantin 22 86 erythromycin 92 64 estradiol estriol estrone ethinyl estradiol fluoxetine gemfibrozil hydrocodone ibuprofen 87 94 iopromide 61 58 meprobamate 74 59 60 75 naproxen oxybenzone 90 66 pentoxifylline TCEP 32 40 8 9 16 triclosan trimethoprim

Microbial Removals Microbe ARR MF Membrane UF Membrane Ozonation Total Coliforms 100 % (nd) 4.8 – 5.9 log 2.3 – 4.1 log 24 m 0.2 um 100 kD 0.3 – 6.3 mg/L-min Weiss, 2005 Farahbakhsh, 2004 Bourgeous, 2001 Owens, 2000 Giardia Cysts >1.9 log 4.6 – 5.2 log 4.7 – 5.2 log 1.5 – 2.7 log 0.1 – 0.2 um 100 – 500 kD 0.3 – 1.0 mg/L-min Jacangelo, 1997 Crypto Occysts >1.5 log > 7 log 0.6 – 2.7 log 0.25 um 13 kD 2.6 – 7.2 mg/L-min Hirata, 1998 MS2 Phage 8 log 0.2 – 1 log 1.7 - > 7 log 3 log 30 m 0.03 mg/L-min Medema, 2002 Jacangelp, 1997 Oh, 2007 ARR: Equivalent to Other Processes if Adequate Time/Distance

Direct Potable Reuse (DPR)

Direct Potable Reuse (DPR) Options Purified water (highly treated reclaimed wastewater) introduced directly into potable water supply distribution system Purified water introduced into raw-water supply immediately upstream of drinking water treatment plant Needs Engineered (vs. Environmental) buffer Demonstrate efficacy of present Industry Standard  MBR-RO-AOP Regulatory Aspects Allowable Recycled Water Contribution (RWC)  Loss of Identity Multiple Barriers (Wastewater) Source Control

Why Consider DPR? (Tchobanoglous et al, 2011) Drivers Shortage of adequate storage (environmental buffer) in proximity to WWTP  Constrained by local hydrogeology and required (e.g., 6-month) residence time Regulations mandating reduction in wastewater discharge into ocean (e.g., California, Florida) Limits to degree of non-potable (purple pipe) reuse Considering tertiary treatment + dual distribution system, agricultural use may be more costly than DPR; also, DPR is less costly than SWRO (desalination) Further increase the degree of WW reuse  increase market Constraint Public (and Regulator) Acceptance

DPR Research Needs (Tchobanoglous et al, 2011) Attributes of Engineered (Storage) Buffer  Need and, if so, Size Robustness, Reliability, and Multi-Objectivity of Individual Advanced (Treatment) Processes Synergies of Various Combinations of Multiple Barriers (redundancy?) Process and System Reliability Monitoring Requirements (locations, surrogates, indicators, on-line (e.g., TOC, UVA, etc.)) Is Reverse Osmosis an Essential Process (vs. nanofiltration?) Balancing Water Chemistry with Blended Waters (corrosion control, etc.)

DPR Industry Standards/Benchmarks (Tchobanoglous et al (2011) Windhoek, Namibia Advanced Processes: O3, GAC, UF (no RO!) Direct blending of reclaimed water with potable water

DPR Industry Standards/Benchmarks (Tchobanoglous et al, 2011) - cont OCWD Groundwater Replenishment System (GWRS) An IPR Facility, But Conceptually Approaches That Envisioned for DPR Advanced Process: MF, RO, AOP Groundwater Injection for Minimum of Six Months (of Storage)

Summary of Opportunities for DPR and IPR (Tchobanoglous et al, 2011)

Engineered (Storage) Buffer Need?  vs. Efficacy and Reliability of Multi-Barrier Process Train A Quality Assurance Buffer/Component Coupled with Monitoring to Allow Diversion of Off-Specification Water Size (residence time)?  Response Time One Larger vs. Several Smaller Tanks?

Possible Engineered Buffer Systems (Tchobanoglous et al, 2011)

DPR Engineered Buffer Considerations Buffer Storage vs. Storage coupled with Treatment Multi-Barrier Treatment for DPR Should engineered buffer be another treatment barrier? Role of buffer in managing chemical and microbial risk Need for/Attributes of Blending Placement of Buffer in context of WWT and DWT Tank vs. Packed Bed Surface vs. Subsurface Engineered Natural Buffer Creation of an artificial aquifer

DPR Engineered Buffer Considerations - cont On-Line Water Quality Sensors DOC, UVA, fluorescence, turbidity, Cl2 residual, conductivity, pH, DO, ORP, Cl- (distributed along flow path) (Truly) on-line sensors for microbiological contaminants ??? Specifications for water quality deviation? Automatic diversion of off-specification water To sewer? Reactor should approach plug flow (PFR) Residence Time Treatment Requirement or Simply a QA/QC Storage Response Time Use of Existing Clear Well as a Buffer Component (monitor Cl2 residual)?

Engineered Buffers Tanks (above or below ground) Lined (and covered) reservoirs Wadi ARR-bounded by natural geological buffer Aquifer storage and recovery (ASR)-saline water occurrence creates buffer Slurry wall isolation of groundwater systems Constructed aquifer Salinity barriers with slow flow to potable sources

Natural Buffer-Wadi Aquifer Natural Buffer-Sides of Wadi No Movement of the Wastewater Will Occur Outside of the Treatment and Storage Area

ASR Systems From Maliva and Missimer, 2012 ARR treated wastewater can be stored for later use in a “chemically-bounded” ASR system than uses a confined aquifer containing saline-water to contain the movement of temporarily stored water. Geology and saline water creates buffers.

Engineered/Constructed Aquifer in Low Hydraulic Conductivity Environment Constructed Rectangular Aquifer in Low Permeability Sediment with Injection or Infiltration at Up-Gradient End and Recovery by Wells at Down-Gradient End. Low hydraulic connectivity of natural bounding sediments provides the buffer.

Wadi ARR System Buffers for Isolation and a Regulatory Use Restriction The boundaries of the recharge, treatment, and collection zones would become restricted use areas designated solely for a reuse project with no well drilling or water use allowed under an “aquifer zoning” legal docturn. No slurry wall boundaries at system edges.

Wadi ARR System Containing Slurry Wall Buffers for Isolation Slurry walls fully surround the treatment, storage, and recovery zones. The slurry walls create the buffers.

Salinity Barriers Using Wastewater From Maliva and Missimer, 2012 Talbout Gap Salinity Barrier, Orange County, California-Travel time of treated wastewater to wells is over 25 years

Regulatory Buffers Natural buffers combined with aquifer zoning ASR combined with aquifer zoning Time of travel controlled return flow to potable water sources Solely regulatory aquifer zones with aquifer buffers based on modeling of travel time (both horizontal and vertical zoning)

Regional Considerations: DPR vs. IPR Because of Cultural and Religious Constraints, DPR is Unlikely for GCC/MENA Region Fatwa  Potable Reuse Permitted If Water Is Returned to the Water Cycle, i.e., IPR

Conclusions-IPR Indirect potable reuse (IPR) can be accomplished with public acceptable, but requires buffering from potable water during treatment and storage. Public acceptability can be achieved using IPR if all aspects of the process can be demonstrated to provide health security and aquifer integrity. Buffers are a key to gaining IPR acceptability

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