Technical and Cost Evaluation of
Alternative Treatment Trains for
Indirect and Direct Potable Reuse
Bill Dowbiggin, P.E.; Bruce Chalmers, P.E.; Sheri Smith, P.E.
November 2015
2015 Annual
Conference
Raleigh, NC
Indirect Potable Reuse Includes an Environmental
Buffer like a Reservoir, River or Aquifer Between
the WWTP and the WTP
NC has lots of Indirect Potable Reuse (IPR) – at each
WTP with intake downstream of one of the major
NPDES discharges below (each colored area is a
river basin). This is termed De Facto or Unplanned
IPR.
3
What is the California Approach?
 Microfiltration, reverse osmosis,
advanced oxidation process
(MF/RO/AOP)
 Why look for alternatives to
MF/RO/AOP?
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Primary reason is the cost
Second reason is brine disposal
Lack of operator experience
Existing tertiary facilities
Abundant surface recharge capacity
Good water quality
 Demineralization isn’t necessary
 Nitrogen reduction isn’t necessary
What Else is There?
 Treatment capabilities: depends on treatment process used,
some removal is possible for nutrients (e.g. total nitrogen and
total phosphorus, TN and TP), total dissolved solids (TDS), total
organic carbon (TOC), and contaminants (or constituents) of
emerging concern (CEC)
 Treated water quality will depend on selected alternative
treatment process and the wastewater influent quality
Alternative
Treatment Method
1
Tertiary recycled water
2
MF/RO Blend
3
GAC or Ozone/Biologically-Activated Carbon (BAC)
4
Nanofiltration
5
Electrodialysis
California Model
MF/RO/AOP
 MF/RO/AOP to produce highest quality water
 AOP often with UV-peroxide
 Pre-approved by CA as part of 2013 draft GWR Regulations for surface
and subsurface application
 Recharge facilities: Surface spreading and groundwater
injection
 Treatment capabilities: nutrient, TDS, TOC, CEC removals
 Recycled Water Contribution (RWC): start at 75%-100%,
lowest blend water requirements
 RWC will vary by project and regulator
 Simplifies operations because of less reliance on blend water
California Model
MF/RO/AOP
WWTP
To WWTP
California Model
MF/RO/AOP
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Advantages
Approved by CA for surface
percolation and injection
wells
Best Available Technology
Numerous existing facilities
Produces highest-quality
water
Removes TOC, TDS, TN &
CECs
Accepted by the public
Shorter travel time/lower
initial diluent requirement
Potential elimination of
diluent water
Disadvantages
 Expensive to construct
 High O&M cost for power
and chemicals
 Brine management
required
Alternative Treatment
Alternative 1 - Tertiary Filtered Recycled Water
 Disinfected tertiary recycled water
 CA Recharge facilities: Surface spreading
only
 Treatment capabilities: no nutrient,
TDS, CEC removal, some TOC
 RWC in CA: start at 20% RWC, blending
req’d
 Montebello Forebay: permitted at 35%
RWC, TOC reduction to increase to 50%
RWC
 Chino Basin (IEUA): permitted RWCs range
from 25 to 45%
Alternative Treatment
Alternative 1 - Tertiary Filtered Recycled Water
Alternative Treatment
Alternative 1 - Tertiary Filtered Recycled Water
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Advantages
Approved by CA for surface
spreading
Meets T22 (CA reg for
reuse water) water quality
Less expensive to construct
Many WRPs already have
tertiary effluent facilities
for discharge
No brine management
required
Proven history (Montebello
Forebay since 1962)
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Disadvantages
Percolation only
May not meet basin plans
for TDS and TN
Requires extensive
amounts of diluent water
Requires long travel time (>
6 months)
CEC, TN removal by Soil
Aquifer Treatment (SAT)
only
Alternative Treatment
Alternative 2 – Blend of Tertiary Recycled
Water/Reverse Osmosis Permeate
 Blend of tertiary effluent and RO permeate
 Partial advanced wastewater treatment (AWT) train with MF/UF and
RO
 Phased AWT train with tertiary effluent (TE) initial phase followed by
MF/RO phase
 Combined or separate disinfection or disinfection/AOP
 Recharge facilities: Surface spreading only
 Treatment capabilities: Partial nutrient, TDS, TOC, CEC
 CA RWC: Begin at 20% RWC because of tertiary component
 Higher RWCs than tertiary effluent alone
 RO Capacity
 RO capacity determined for TOC reduction for desired RWC
 RO capacity can also be sized for TDS reduction
Alternative Treatment
Alternative 2 – Blend of Tertiary Recycled
Water/Reverse Osmosis Permeate
16.6 mgd
5 mgd
10 mgd
11.6 mgd
To
WWTP
0.8 mgd
15 mgd
0.8 mgd
Alternative Treatment
Alternative 2 – Blend of Tertiary Recycled
Water/Reverse Osmosis Permeate
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Advantages
Good water quality
Removes some TDS, TOC,
TN & CECs
Requires diluent water (but
not as much as TE)
Implementation can be
phased
AOP not required
Less expensive than
MF/RO/AOP
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Disadvantages
More expensive to
construct than tertiary
effluent
Moderate O&M cost for
power and chemicals
Some brine management
required
Percolation only
Alternative Treatment
Alternative 3 – GAC or Ozone-BAC
 Ozone & BAC in various configurations to
produce high quality water
 Processes: Ozone, BAC, optional MF/UF
polishing, disinfection
 Recharge facilities: Surface spreading
only in CA
 Treatment capabilities: No nutrient or
TDS removal, some TOC removal, CEC
removal
Filtered
WW
Disinfection
Percolation Pond or
Raw Water
Reservoir
Alternative Treatment with GAC or Ozone-BAC
 Existing Facilities:
 Goreangab WTP (Windhoek, Namibia) – Ozone-BAC, direct potable
reuse
 Fred Hervey WRP (El Paso, TX) – Ozone-BAC, indirect potable reuse,
irrigation and cooling water
 F. Wayne WRP (Georgia) – Ozone-BAC, indirect potable reuse into Lake
Lanier
 UOSA (Virginia) – GAC (pilot testing Ozone-BAC), indirect potable reuse
into Occoquan Reservoir
Pathogen
CDPH
Reqmt
WWTP
Title 22
Treatment
Ozone
BAC
UV
Virus
12
2
Up to 5
total
6
0
0
Giardia
10
2
-
4
0
6
Cryptosporidium
10
1
-
0
0
6
Travel
Time/
SAT
6
Total
>0
TBD
>0
TBD
>10
>12
>10
Alternative Treatment
Alternative 3 – GAC or Ozone-BAC
(optionally with Sidestream MF/RO)
15.5 mgd
15 mgd
3.4 mgd
2.9 mgd
To WWTP
0.26 mgd
0.24 mgd
Alternative Treatment
Alternative 3 – GAC or Ozone-BAC
 Advantages:
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Removes some TOC so less blend water
Effective at removing CECs
Elimination of concentrated brine stream
Potential for reduced energy requirements
 Disadvantages:
 Must be permitted as an “Alternative” process to increase RWC for
initial operation above 20% in CA
 Does not reduce TDS or chlorides
 Limited removal of nitrogen and phosphorus compounds
 Does not remove as much TOC as MF/RO/AOP, higher blending water
require
 Potential to form bromate when high bromide in source water
Ozone-BAC Pilot Testing Projects are Underway
for Gwinnett County GA and UOSA VA
Alternative Treatment
Alternative 4 – Nanofiltration
 Produces high quality water
 Processes: MF/UF, NF, UV-AOP (NF replaces RO)
 Recharge facilities: surface spreading, potential for
groundwater injection if CA approved “Alternative”
 Treatment capabilities: No nutrient removal, some TDS
removal, TOC & CEC removal
Alternative Treatment
Alternative 4 – Nanofiltration
 Advantages
 Potential lower power cost than RO
 Removes TOC nearly as well as RO
 Better water quality than T22, CA might
allow subsurface injection
 Disadvantages
 Power savings may be temporary
 Less TDS removal than RO
 No reduction of concentrate compared to
RO
 No MF/NF/UV-AOP installations in
California for IPR
 Poor removal of inorganic nitrogen
 No capital cost savings
Alternative Treatment
Alternative 5 – Electrodialysis Reversal (EDR)
 Process uses
 Replacement for RO for TDS
removal
 Sidestream TDS reduction
 Zero liquid discharge (ZLD) process
 Existing Facilities
 North City WRP (San Diego, CA)
 TDS reduction for irrigation
 Design/build: EDR vs RO
 6 mgd
 Fort Irwin 2014 (Barstow, CA)
 EDR is proprietary with GE as the
main manufacturer
Alternative Treatment
Alternative 5 – Electrodialysis Reversal
 Advantages
 Slightly higher recovery than
MF/RO/AOP at 85%
 Can reduce TDS and TN
 Can be used for ZLD
 Disadvantages
 Not a barrier process
 No TOC or CEC reduction
 Few full size installations with no
CA-permitted IPR facilities
 Time-consuming manual
membrane maintenance
 Potential electrical and leakage
problems
How to Decide?
 Influent and product water quality are critical to determining
which treatment process to use:
 Primary focus is on TOC/COD reduction in CA and some other
locations
 Secondary focus is on TDS, Nutrients and CEC reduction
 Consider whether current TDS and NO3 concentrations are
acceptable for example
 Consider what brine management options are available
 How much diluent water is available and at what cost?
How to Decide?
 Has the process been permitted for IPR?
 Consider sidestream treatment if needed:
 South Bay Water Recycling Project – MF/RO to reduce TDS
 Consider phasing of treatment:
 Reduces initial costs
 Helps meet water quality requirements
 Extends time for brine management technologies
 Impact of future regulations:
 Will facilities be applicable to DPR?
How to Decide?
CA Example Evaluation
Objective
Sub-objective
Maximize
Cost-Effectiveness
Initial Net Present Value (NPV)
Maximize
Reliability
Water Supply/Discharge Benefit
Minimize
Environmental Impact
Environmental Permitting Complexity
Maximize
Implementation
Permitting Complexity
Build-out Net Present Value (NPV)
Negative Impact on GW Wells
Environmental Value /Stewardship (Sustainability)
Public Acceptability
Improve Groundwater Basin
Basin Salt Concentration
Water Quality
Minimize Operational
Complexity
Integration/Operational Complexity
Reliability of Technology
Compliance Sampling Frequency
How to Decide?
CA Example Evaluation
(NF & EDR already eliminated)
Tertiary Filtration
Ozone – BAC
Partial MF/RO
MF/RO/AOP
Phased TE
And MF/RO
Cost Effectiveness
Environmental Impact
Groundwater Quality
Reliability
Implementation
Operations
Cost of Alternative Treatment Trains for a
10 mgd facility
Process
Capital Cost Range
O&M Cost Range
MF/RO/AOP*
$ 7-10/gpd
$ 1-2.5/thou gal
Ozone/BAC
$ 2.5-4/gpd
$ 0.3-1.2/thou gal
*Assumes ocean outfall available for RO
Conclusions
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MF/RO/AOP is still a popular and viable alternative in CA
MF/RO/AOP is the only proven process for injection wells
“Alternative” treatment processes should be investigated
Partial or phased MF/RO offers advantages of less cost and
lower brine production
Ozone-BAC can be less expensive and requires less blend
water but may need sidestream TDS and TN reduction
Ozone-BAC use is increasing outside of CA due to costeffectiveness for the quality and sustainability factors
Nanofiltration may have lower O&M costs than RO
EDR is not a barrier but can work as a sidestream or part of
a zero liquid discharge brine treatment process
Questions
William B. Dowbiggin, P.E., BCEE
CDM Smith
(919) 623-7964
dowbigginwb@cdmsmith.com