1. November 2015
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.
2015 Annual
Conference
Raleigh, NC
2. Indirect Potable Reuse Includes an Environmental
Buffer like a Reservoir, River or Aquifer Between
the WWTP and the WTP
3. 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
4. Microfiltration, reverse osmosis,
advanced oxidation process
(MF/RO/AOP)
Why look for alternatives to
MF/RO/AOP?
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 is the California Approach?
5. 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
6. 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
8. California Model
MF/RO/AOP
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
9. 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%
11. Alternative Treatment
Alternative 1 - Tertiary Filtered Recycled Water
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)
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
12. 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
13. Alternative Treatment
Alternative 2 – Blend of Tertiary Recycled
Water/Reverse Osmosis Permeate
5 mgd
11.6 mgd
0.8 mgd
15 mgd
10 mgd
16.6 mgd
0.8 mgd
To
WWTP
14. Alternative Treatment
Alternative 2 – Blend of Tertiary Recycled
Water/Reverse Osmosis Permeate
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
Disadvantages
More expensive to
construct than tertiary
effluent
Moderate O&M cost for
power and chemicals
Some brine management
required
Percolation only
15. 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
16. 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 Travel
Time/
SAT
Total
Virus 12 2 Up to 5
total
6 0 0 6 >12
Giardia 10 2 - 4 0 6 >0
TBD
>10
Crypto-
sporidium
10 1 - 0 0 6 >0
TBD
>10
17. Alternative Treatment
Alternative 3 – GAC or Ozone-BAC
(optionally with Sidestream MF/RO)
3.4 mgd
0.24 mgd
2.9 mgd
15.5 mgd
15 mgd
0.26 mgd
To WWTP
18. Alternative Treatment
Alternative 3 – GAC or Ozone-BAC
Advantages:
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
20. 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
21. 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
22. 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
23. 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
24. 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?
25. 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?
26. How to Decide?
CA Example Evaluation
Objective Sub-objective
Maximize
Cost-Effectiveness
Initial Net Present Value (NPV)
Build-out Net Present Value (NPV)
Maximize
Reliability
Water Supply/Discharge Benefit
Negative Impact on GW Wells
Minimize
Environmental Impact
Environmental Permitting Complexity
Environmental Value /Stewardship (Sustainability)
Maximize
Implementation
Permitting Complexity
Public Acceptability
Improve Groundwater Basin
Water Quality
Basin Salt Concentration
Minimize Operational
Complexity
Integration/Operational Complexity
Reliability of Technology
Compliance Sampling Frequency
27. Tertiary Filtration
Ozone – BAC
Partial MF/RO
MF/RO/AOP
Phased TE
And MF/RO
How to Decide?
CA Example Evaluation
(NF & EDR already eliminated)
Cost Effectiveness Reliability
Environmental Impact Implementation
Groundwater Quality Operations
28. 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
29. Conclusions
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 cost-
effectiveness 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
Go through bullets
Introduce the 5 alterantive treatment processes.
Now lets talk about full advanced treatment, or FAT. Start at 85% and after 18 mth can go to 100%
FAT is the “California Model” of MF/RO/UV-AOP
It is pre-approved in the new CDPH regulations for both surface and subsurface recharge.
It is also able to treat the water for nutrients, TDS, TOC and CECs.
Since FAT removes the TOC to less than 0.5 mg/L, it will allow a RWC of up to 100% after an initial start-up period. The initial RWC may vary by area and by how much prior experience the owner has in indirect potable reuse.
No having blend water simplifies the operation for both spreading and injection.
Here is a simple flow diagram for FAT, showing. ONLY one can do deep well injection (percolation gives more trtmt)
Go through the list of advantages and disadvantages.
Read through the bullets showing 2 types filt – top is fabric on drums, bottom conv filters – could do MF too. GA has MBR to reuse
Again, a simple flow diagram.
Read quickly through advantages and disadvantages
Alternative 2 – blend of TE with MF/RO permeate. BLEND driver – reduce TDS
Read through bullets
Here is a diagram that shows the partial sidestream treatment of the TE with RO. Amt of RO pends on how much TDS, TOC or nitrate etc have to remove
Read through the bullets for advantages and disadvantages. Bruce has never been CEC limited. Percolation has no CEC limits – lots go away
Read through the bullets. In CA, at least san diego, they considered putting into reservoir DPR instead of IPR
Ozone can be used in various configurations.
Ozone BAC is an option that doesn’t have any brine stream to treat.
Spreading only
Limited nutrient and TDS removal, some TOC and some CEC removal depending on the ozone dose.
MFRO just if TDS, TN or TP limit – in GW have TN but not TP limit
Potential $ savings – unclear if last – when get dirty pressure sometimes rises to same as RO
NF is the nano – ESPA is RO
Pics are san diego
Partial and Phased MF/RO were rated the highest
These alternatives rated well on most objectives
Each provided good water quality that mitigated future groundwater desalting
Highest overall project Net Present Value
MF/RO/AOP was rated highly but is the most expensive project and generates the most brine.
Tertiary Effluent and Ozone-BAC:
Overall rating was significantly lower than MF/RO/AOP and partial MF/RO.
Lack of diluent water can be a problem.
Meeting basin limits for TDS can be a problem.
Eastern Municipal Water District near LA. RO rates great for WQ, not for cost
This shows they had enough blend water so partial trtmt does well
Phase TE (secondary plus conv filters) add MF RO 10 years later. Doing some RO early