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Direct, Indirect, and Potable Reuse Panel

TWCA Mid Year MeetingJune 2012

Guy Carpenter, PE

Vice President - Water Supply & Reuse

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Direct Reuse

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Indirect Potable ReuseGroundwater Augmentation

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Indirect Potable ReuseSurface Water Augmentation

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Indirect Potable ReuseSurface Water Augmentation

?

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Direct Potable Reuse

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Texas Reuse Regulations

• Direct Reuse– Title 30, Chapter 210 of the Texas Administrative

Code; administered by the TCEQ

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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

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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.

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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

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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”

Clarified

Secondary Efflue

nt

UF/RO

UV/H2O

2

What

Else?

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)

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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 CONTROL POINTS• Developed by NASA in

the early 1960’s, widely adopted in the food industry, among others.

• Centers around the idea of “Critical Control Points.”

• Focus is put on managing the CCPs

Analyze HazardsID hazards and potential control

solutions.

ID CCPsIdentify and label the critical control

points throughout the process.

ID Prevention Measures

Establish protocols for minimizing failures at the CCPs.

Develop “Fail-Safe” Response

Establish protocols for minimizing the effect of CCP failures. Document CCP

EventsKeep a log of how well the system works.

Review and modify the protocol periodically.

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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 FATMoving 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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NDMA

Biological Filtration Solves these Issues

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Biological Filtration Solves these Issues

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

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

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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