1. 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

2. 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?

3. 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

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

6. 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

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

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

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

10. 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

11. 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

12. 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!

13. 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

14. Indirect Potable Reuse (IPR)

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

16. 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

17. 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

18. 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

19. ARR: Infiltration to Recovery (Cikurel, 2004)

20. 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) ?

21. 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

22. 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% %
>90%
Flocculation
<20% %
Ozonation
10 - >90%
GAC, PAC
PAC/UF NF UV %
Chlorine
< %
Chlorine dioxyde
<10 - >90%
RO and GAC: Poor Retention of low MW polar compounds (e.g., NDMA)
AOP: Slow Oxidation of Chlorinated Flame Retardants

23. 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

24. 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

25. Direct Potable Reuse (DPR)

26. 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

27. 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

28. 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.)

29. 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

30. 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)

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

32. 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?

33. Possible Engineered Buffer Systems (Tchobanoglous et al, 2011)

34. 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

35. 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)?

36. 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

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

38. 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.

39. 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.

40. 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.

41. 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.

42. 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

43. 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)

44. 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

45. 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

46. Thank you… 46