November 2015
Technical and Cost Evaluation of Alternative Treatment Trains for
Indirect and Direct Potable ReuseBill Dowbiggin, P.E.; Bruce Chalmers, P.E.; Sheri Smith, P.E.
2015 Annual Conference Raleigh, NC
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.
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?
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 ModelMF/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 ModelMF/RO/AOP
To WWTP
WWTP
California ModelMF/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
Alternative TreatmentAlternative 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 TreatmentAlternative 1 - Tertiary Filtered Recycled Water
Alternative TreatmentAlternative 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
Alternative TreatmentAlternative 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 TreatmentAlternative 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
Alternative TreatmentAlternative 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
Alternative TreatmentAlternative 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 Travel Time/
SAT
Total
Virus 12 2 Up to 5 total
6 0 0 6 >12
Giardia 10 2 - 4 0 6 >0TBD
>10
Crypto-sporidium
10 1 - 0 0 6 >0TBD
>10
Alternative TreatmentAlternative 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 mgdTo WWTP
Alternative TreatmentAlternative 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
Ozone-BAC Pilot Testing Projects are Underway for Gwinnett County GA and UOSA VA
Alternative TreatmentAlternative 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 TreatmentAlternative 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 TreatmentAlternative 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 TreatmentAlternative 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-objectiveMaximizeCost-Effectiveness
Initial Net Present Value (NPV)
Build-out Net Present Value (NPV)
MaximizeReliability
Water Supply/Discharge Benefit
Negative Impact on GW Wells
MinimizeEnvironmental Impact
Environmental Permitting Complexity
Environmental Value /Stewardship (Sustainability)
MaximizeImplementation
Permitting Complexity
Public Acceptability
Improve Groundwater Basin Water Quality Basin Salt Concentration
Minimize OperationalComplexity
Integration/Operational Complexity
Reliability of Technology
Compliance Sampling Frequency
Tertiary Filtration
Ozone – BAC
Partial MF/RO
MF/RO/AOP
Phased TEAnd MF/RO
How to Decide?CA Example Evaluation(NF & EDR already eliminated)
Cost Effectiveness ReliabilityEnvironmental Impact ImplementationGroundwater Quality 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
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