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

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

GCWA1113_interview.pptx
Map
GCWA serves
municipal,
industrial, and
irrigation users
in Brazoria, Fort
Bend, and
Galveston
Counties
City of Houston

Map
Shannon P/S – 60 MGD
(Average Capacity)
Oyster Creek

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

Map
Thomas Mackey WTP – 50 MGD
Oyster Creek

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

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 Reuse
Near-term,
lowest cost option
Longer term,
higher cost option
Not Practical

Map
Thomas
Mackey
WTP
Approximately 8.5 miles to Canal A
Over 32 miles to
Thomas Mackey WTP
Treated effluent from Houston’s SW WWTP
provides a possible supply source
Houston SW WWTP
(60 MGD max/30 MGD ave)

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

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 Supply
Ongoing monitoring
& verification

Increasing risk requires more
safeguards to make supply safe
IncreasingRisk
(acute&chronic)
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

Regulators and end-users must be
confident in approach
Does it provide
sufficient
treatment to
mitigate risk?
Can I trust this
source of
supply?

Environmental barrier & monitoring
make supply reliable (trustworthy)
 Response Retention Time
(RRT)
 Treatment (Attenuation)
 Verify performance
 Early warning
Environmental Barrier Water Quality Monitoring

0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
10 100 1000 10000
PercentNotExceeded
Fecal Coliform
Existing raw supply already impacted
Fecal Coliform in Brazos River at Richmond Station (1980-1995)
In-stream
standard
Type I
reuse
standard

WQ evaluations will establish
possible range of blended quality
0
50
100
150
200
250
300
350
Oyster Cr @ A
Canal
Oyster Cr @
Hwy 90
Possible
Blend - Low
Possible
Blend - Max
E.coli(CFU/100ml)
Historic Sampling Possible Blended Canal WQ
Under some
conditions, blended
quality might be
higher than
Oyster Cr.

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

Regulatory Approaches to Direct
Potable Reuse (DPR)
Severely impaired High quality
sewage
WWTP
effluent
Defined:
10-4 risk
drinking water
TCEQ Approach (8/6/5.5)
California / WRRF Approach (12/10/10)
site-
specific
quality
site-
specific
quality

TCEQ BASELINE GOALS
Barrier/Treatment Log Removals*
* Virus / Crypto / Giardia
Multiple barriers will ensure safety
of supply
8 / 6 / 5.5

TCEQ BASELINE GOALS
1. Dilution
of supply
8 / 6 / 5.5
Negligible

TCEQ BASELINE GOALS
1. Dilution
2. Canal A
(Environmental Buffer)
of supply
8 / 6 / 5.5
Negligible
Variable
(safety factor)

TCEQ BASELINE GOALS
1. Dilution
2. Canal A
3. Thomas Mackey WTP
(Conventional WTP)
of supply
8 / 6 / 5.5
Negligible
Variable
(safety factor)
4 / 3 / 2

TCEQ BASELINE GOALS
1. Dilution
2. Canal A
(Conventional WTP)
Total of All Barriers/Treatment
of supply
8 / 6 / 5.5
Negligible
Variable
(safety factor)
4 / 3 / 2
4 / 3 / 2

TCEQ BASELINE GOALS
1. Dilution
2. Canal A
(Conventional WTP)
Potential Deficit
of supply
4 / 3 / 3.5
8 / 6 / 5.5
Negligible
Variable
(safety factor)
4 / 3 / 2
4 / 3 / 2

TCEQ BASELINE GOALS
1. Existing Systems
of supply
8 / 6 / 5.5
4 / 3 / 2

TCEQ BASELINE GOALS
1. Existing Systems
2. Possible Barriers
a. Enhanced disinfection
(chlorine dioxide +
chlorine)
of supply
8 / 6 / 5.5
4 / 3 / 2
4+ / 2+ / 2+

TCEQ BASELINE GOALS
1. Existing Systems
(chlorine dioxide +
chlorine)
b. Optimized filtration
(0.15 NTU 95% time)
of supply
8 / 6 / 5.5
4 / 3 / 2
4+ / 2+ / 2+
0 / 0.5-1.0 / 0

TCEQ BASELINE GOALS
1. Existing Systems
2. Possible Additional Barriers
(chlorine dioxide +
chlorine)
(0.15 NTU 95% time)
c. UV disinfection
of supply
8 / 6 / 5.5
4 / 3 / 2
4+ / 2+ / 2+
0 / 0.5-1.0 / 0
<1 / 3+ / 3.5

TCEQ BASELINE GOALS
1. Existing Systems
(chlorine dioxide +
chloramines)
(0.15 NTU 95% time)
c. UV disinfection
of supply
8 / 6 / 5.5
4 / 3 / 2
4+ / 2+ / 2+
0 / 0.5-1.0 / 0
<1 / 3+ / 3.5
8+ / 6+ / 5.5+

UV inactivates Crypto & Giardia at
low doses and reasonable cost
0
20
40
60
80
100
2 log virus 3.5 log
Giardia/Crypto
UVDose(mJ/cm2)
$0.05/gal $0.20/gal
Budgetary Cost
Range for UV @ WTP

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

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

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