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

Questions

William B. Dowbiggin, P.E., BCEECDM Smith

(919) 623-7964 dowbigginwb@cdmsmith.com