Potable Reuse as a New Source of Supply for Gulf Coast Water Authority

GCWA: Ivan Langford III – General ManagerCarollo Engineers: Meera Victor – Project Manager

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Map

GCWA serves municipal, industrial, and irrigation users in Brazoria, Fort Bend, and Galveston Counties

City of Houston

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Shannon P/S – 60 MGD (Average Capacity)

Oyster Creek

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Map 2nd Lift P/S – 50 MGD(Average Capacity)Oyster Creek

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Map

Thomas Mackey WTP – 50 MGD

Oyster Creek

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Brazos River @ Juliff Intake in 2009 tells the story of drought situation

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Multiple options to supplement supply were investigated

1. Desalination

2. Obtain additional treated water from Houston

3. Participate in raw water supply from east Texas

4. Participate in Allen’s Creek Project

5. Potable ReuseNear-term,

lowest cost option

Longer term, higher cost option

Not Practical

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Map

ThomasMackey

WTP

Approximately 8.5 miles to Canal A

Over 32 miles toThomas Mackey WTP

Treated effluent from Houston’s SW WWTP provides a possible supply source

Houston SW WWTP(60 MGD max/30 MGD ave)

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WWTP discharge to A Canal is a “grey” area of TCEQ regulations

Waters of the State Discharges Permitted under 30

TAC §307 and §309 (TPDES) A WTP intake can be located as

close as 500 feet away

Brazos River

Not Waters of the State Intent to reuse requires

permitting on an individual basis Dilution and environmental

buffer are important

GCWA Canal

http://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&docid=KhV4_IaIqcB8oM&tbnid=LEDZmx9Mnh91iM:&ved=0CAUQjRw&url=http://en.wikipedia.org/wiki/Battle_of_the_Brazos_River&ei=u5-RU5qqHLSksQTG-oCQAg&bvm=bv.68445247,d.b2k&psig=AFQjCNEhxYlShuCbjcm5gselVI8nAQry3Q&ust=1402138937962748

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This project puts GCWA on path towards supply augmentation with potable reuse

T1&2 – Data/gaps/monitoring

T3 - Regulatory

T4&5 – Goals & Standards

T6 – Presentations

T7 - Reporting

Water shortages

Water Quality Study

Negotiate

Implement Strategies

Augment SupplyOngoing monitoring

& verification

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Increasing risk requires more safeguards to make supply safe

Incr

ea

sin

g R

isk

(a

cute

& c

hro

nic

)

Increasing Safeguards (treatment & barriers)

Conventional WTP(4 log virus, 3 log Crypto)

Higher level of treatment& barriers needed for

higher risk

Brazos R. designated “high” per TCEQ SWA

WWTP discharge into canal increases risk

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Regulators and end-users must be confident in approach

Does it provide sufficient treatment to mitigate risk?

Can I trust this source of supply?

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Environmental barrier & monitoring make supply reliable (trustworthy)

Response Retention Time (RRT)

Treatment (Attenuation)

Verify performance Early warning

Environmental Barrier Water Quality Monitoring

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10 100 1000 100000%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Fecal Coliform

Pe

rce

nt

No

t E

xce

ed

ed

Existing raw supply already impacted

Fecal Coliform in Brazos River at Richmond Station (1980-1995)In-stream standard

Type I reuse standard

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WQ evaluations will establish possible range of blended quality

Oyster Cr @ A Canal

Oyster Cr @ Hwy 90

Possible Blend - Low

Possible Blend - Max

0

50

100

150

200

250

300

350

E.

coli (

CFU

/10

0 m

l)

Historic Sampling Possible Blended Canal WQ

Under some conditions,

blended quality might be higher

than Oyster Cr.

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Potable Reuse in Texas

§290.D.42(g) - Innovative/ alternate treatment clause:“Any treatment process that does not have specific design requirements in 290.42(a) – (f) of this title.”

Case-by-case approval• Treatment requirements based on

pathogen log reduction credits

• Pilot or “full scale verification” required

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Regulatory Approaches to Direct Potable Reuse (DPR)

Severely impaired High quality

sewageWWTPeffluent

Defined:10-4 risk

drinking water

TCEQ Approach (8/6/5.5)

California / WRRF Approach (12/10/10)

site-specificquality

site-specificquality

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TCEQ BASELINE GOALS

Barrier/Treatment Log Removals*

* Virus / Crypto / Giardia

Multiple barriers will ensure safety of supply

8 / 6 / 5.5

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TCEQ BASELINE GOALS

1. Dilution




8 / 6 / 5.5

Negligible

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TCEQ BASELINE GOALS

1. Dilution

2. Canal A(Environmental Buffer)




8 / 6 / 5.5

Negligible

Variable(safety factor)

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TCEQ BASELINE GOALS

1. Dilution


3. Thomas Mackey WTP(Conventional WTP)




8 / 6 / 5.5

Negligible


4 / 3 / 2

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TCEQ BASELINE GOALS

1. Dilution



Total of All Barriers/Treatment




8 / 6 / 5.5

Negligible


4 / 3 / 2

4 / 3 / 2

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TCEQ BASELINE GOALS

1. Dilution




Potential Deficit




4 / 3 / 3.5

8 / 6 / 5.5

Negligible


4 / 3 / 2

4 / 3 / 2

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TCEQ BASELINE GOALS




8 / 6 / 5.5

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TCEQ BASELINE GOALS

1. Existing Systems




8 / 6 / 5.5

4 / 3 / 2

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TCEQ BASELINE GOALS

1. Existing Systems

2. Possible Barriersa. Enhanced disinfection (chlorine dioxide + chlorine)




8 / 6 / 5.5

4 / 3 / 2

4+ / 2+ / 2+

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TCEQ BASELINE GOALS

1. Existing Systems

2. Possible Barriersa. Enhanced disinfection (chlorine dioxide + chlorine)

b. Optimized filtration (0.15 NTU 95% time)




8 / 6 / 5.5

4 / 3 / 2

4+ / 2+ / 2+

0 / 0.5-1.0 / 0

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TCEQ BASELINE GOALS

1. Existing Systems

2. Possible Additional Barriersa. Enhanced disinfection (chlorine dioxide + chlorine)


c. UV disinfection




8 / 6 / 5.5

4 / 3 / 2

4+ / 2+ / 2+

0 / 0.5-1.0 / 0

<1 / 3+ / 3.5

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TCEQ BASELINE GOALS

1. Existing Systems

2. Possible Barriersa. Enhanced disinfection (chlorine dioxide + chloramines)


c. UV disinfection





8 / 6 / 5.5

4 / 3 / 2

4+ / 2+ / 2+

0 / 0.5-1.0 / 0

<1 / 3+ / 3.5

8+ / 6+ / 5.5+

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UV inactivates Crypto & Giardia at low doses and reasonable cost

2 log

viru

s

3.5

log

Giard

ia/C

rypt

o0

20

40

60

80

100

UV

Dose

(m

J/cm

2)

$0.05/gal $0.20/gal

Budgetary CostRange for UV @ WTP

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Conclusions

1. Potable reuse offers the quickest, least expensive approach for augmenting the GCWA water supply

2. This study will establish reuse water quality to ensure safety and reliability of supply

3. Multiple barriers are needed to make supply safe and trustworthy

4. Supplemental treatment with UV disinfection or another technology might be required

GCWA: Ivan Langford III – General ManagerCarollo Engineers: Meera Victor – Project Manager

Education

Potable Reuse as a New Source of Supply for Gulf Coast Water Authority