Direct, Indirect, and Potable Reuse Panel

Direct, Indirect, and Potable
Reuse Panel

TWCA Mid Year Meeting
June 2012

Guy Carpenter, PE
Vice President - Water Supply & Reuse
CarolloTemplateWaterWave.pptx


Direct Reuse

2

Indirect Potable Reuse
Groundwater Augmentation

3

Surface Water Augmentation

4

Surface Water Augmentation

5


Direct Potable Reuse

6

Texas Reuse Regulations

• Direct Reuse
– Title 30, Chapter 210 of the Texas Administrative
Code; administered by the TCEQ

7

Texas Reuse Regulations
• Direct Reuse
– Title 30, Chapter 210 of the Texas Administrative Code;
administered by the TCEQ
• Indirect Reuse (Surface Water Augmentation)
– Texas PDES Permit
– Texas Surface Water Quality Standards
– T.A.C Chapters 295 and 297 - rules and process for water rights
• Indirect Reuse (Groundwater Augmentation - ASR)
– T.A.C. Chapter 331- meet or exceed SDWA requirements and
TCEQ DW standards (T.A.C. Chapter 290)
– No specific regs for spreading (percolation) basins

• Potable Reuse (DPR)
– No regulations , but not prohibited
– TWDB looking for a path forward 8

TWDB Project Seeks Path for Direct
Potable Reuse
• Focused on removal of “environmental buffer”
• Examine the range and incidence of contaminants of
concern for potable reuse in Texas
• Benchmark water quality goals and treatment strategies
for potable reuse projects
• ID treatment performance indicators for range of
implementation (costs, energy, residuals,
advantages/disadvantages)
• Guidance document summarizing water quality goals and
recommended treatment approaches for potable reuse in

Texas.

9

What do we lose by not having an
environmental buffer?

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Response Time is the Ultimate Value of
the Environmental Buffer

“The primary benefit of an environmental
buffer is to provide time to react should
treatment be inadequate due to process
failure or other factors”

– Direct Potable Reuse, A Path
Forward

11

NRC Report on Potable Reuse
(January 2012)

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Planned Potable Reuse – Key Findings
from NRC Report
• Natural systems are employed in most potable water reuse systems to serve
as an environmental buffer, which may provide:
– Retention time
– Attenuation of contaminants
– Blending (or dilution)

• Engineered processes can be designed to achieve these same functions
– Cannot be demonstrated that “natural” barriers provide public health protection
that is not also available by other engineered processes
– Science required to design for uniform protection from one environmental buffer
to the next is not available

• Potable reuse of highly treated reclaimed water without an environmental
buffer is worthy of consideration, if adequate protection is engineered within
the system

• Distinction between indirect and direct potable reuse is not scientifically
meaningful to product water quality
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Full Advanced Treatment “FAT”

How “Phat”
does FAT need
to be?

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Two Projects Specifically Addressing
Risk & Treatment
• Evaluation of Risk Reduction Principles for Direct
Potable Reuse (WRRF-11-10)
• Equivalency of Advanced Treatment Trains for
Potable Reuse (WRRF-11-02)

15

Evaluation of Risk Reduction Principles
for Direct Potable Reuse (WRRF-11-10)
• NASA
• Nuclear Energy Industry
• Structural Engineering
(bridges & buildings)
• Focus on:
– Reducing human error
• Training
• Checklists
– Minimize close coupling
of complex systems

– Improvements in
monitoring and controls
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HAZARD ANALYSIS
AND CRITICAL Analyze Hazards
ID hazards and potential control solutions.
CONTROL POINTS
ID CCPs
• Developed by NASA in Identify and label the critical control points
throughout the process.
the early 1960’s,
widely adopted in the ID Prevention Measures
food industry, among Establish protocols for minimizing failures at
others. the CCPs.

• Centers around the Develop “Fail-Safe”
idea of “Critical Control Response
Points.” Establish protocols for minimizing the effect of
CCP failures.
• Focus is put on

managing the CCPs Document CCP Events
Keep a log of how well the system works.
Review and modify the protocol periodically.
17

Project Observations to Date
• Current FAT technologies provide for sufficient treatment
barriers, if they are all properly working.
• Additional treatment or storage can be provided to
counter the loss of the environmental buffer.
• Online monitoring techniques can increase operational
confidence.
• How much time is needed to properly monitor (and
respond) is yet to be determined.
• From the Outside Experts:
– Training, Training, Training…and Motivation!
– Avoid “Complex and Closely Coupled” systems as much as

possible.
– Make alarms meaningful.
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Equivalency of Advanced Treatment
Trains for Potable Reuse (WRRF-11-02)
• MF/RO + AOP is the “Gold Standard”
• RO brine difficult to deal with (concentrated
everything)
• What is the performance of other technologies for
EDCs if salts are not a concern?
• Focused entirely on replacing the RO process

Moving Away from FAT

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Alternatives to RO Treatment Are
Available
• Match pathogen reduction (4+ log protozoa, 4+ log virus)
– At Ct of 1 mg-min/L, Ozone achieves greater than 5 log removal
of viruses and bacteria
• Match trace pollutant reduction (95% removal of most
pollutants)
– Ozone provides robust removal of trace organics

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Ozone Provides a Robust Barrier to
Trace Pollutants

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…but, Ozone does make byproducts

• Bromate

• Biodegradable dissolved organic carbon

• NDMA

• Aldehydes

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Biological Filtration Solves these Issues

NDMA

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Biological Filtration Solves these Issues

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Polishing Treatment with UV is
Recommended to Provide a Multiple
Barrier to Pollutants and Pathogens

 >5-log Virus
 >5-log Bacteria
 >5-log Protozoa
 Plus NDMA destruction

25

Summary

• Current research is helping us:
– Determine how much treatment is necessary for IPR
and DPR
– Reduce the risk of not having the response time
afforded by the environmental buffer

26

Direct, Indirect, and Potable Reuse Panel

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