“Green” & Sustainable Infrastructure: A Water Treatment Perspective Michael R. Schock USEPA, ORD, NRMRL, WSWRD Cincinnati, OH [email protected]
Apr 01, 2015
“Green” & Sustainable Infrastructure: A Water Treatment Perspective
“Green” & Sustainable Infrastructure: A Water Treatment Perspective
Michael R. SchockUSEPA, ORD, NRMRL, WSWRD
Cincinnati, [email protected]
Michael R. SchockUSEPA, ORD, NRMRL, WSWRD
Cincinnati, [email protected]
Why Do We Care about Plumbing?
• Human health Toxic contaminants
• Metals• Microorganisms• Organic leachates
Allergens• Dermal irritants (eg. Ni)• Biofilms
Why Do We Care about Plumbing?
• Materials longevity Uniform corrosion (wears through) Non-uniform corrosion
• pinhole leaks• tuberculation
Scale View of Drinking Water Distribution
• Municipal distribution network Mains Storage tanks/reservoirs
• Service lines • Premise plumbing system
Cold (drinking/consumption) Hot (human use)
“Premise Plumbing”• After NRC-NAS Report1 definition• Residential• School/day care• Hospital• Office building• Manufacturing complex
1 National Research Council, 2006. Alternatives for Premise Plumbing. Ch. 8 in: Drinking Water Distribution Systems: Assessing and Reducing Risk, pp. 316-340. National Academies Press, Washington, DC.
Typical Plumbing Materials: DS• Old unlined iron• Asbestos-cement• Cement mortar linings with seal coat
Bitumen Epoxy
• Plastics• In-situ relined (rehabilitated)
Cement mortar Epoxy Plastic liners
Typical New Premise Plumbing Materials
• Copper• Plastics• Copper alloy components
Traditional leaded brasses New low-Pb alloys
• Stainless steels• Plated materials (Ni, Cr)• Soldered joints
What Are Contamination Sources?
• Pipes• Faucets• Flow control/shut-off valves• Meters• Pressure regulators• Backflow preventers• Storage tanks• Biofilms growing in the above
Pipe Networks Are Not Inert!
Challenges of Water Conservation
• Creates conditions of Higher metal exposure potential Depletion of disinfection Temperature conditions favorable for
nitrification and other biofilm growth• Problem extent function of:
Background water chemistry Usage pattern Spatial distribution of contamination sources
Example: Copper Levels and Stagnation
Stagnation time, hours
0 10 20 30 40 50 60 70 80 900
1
2
3
4
5
6
7Cu, 161-184 days
DO, 161-184 daysCu, 455-462 days
DO, 455-462 days
Dissolved oxygen
Copper
Current Plumbing Standards• EPA does not have statutory authority
to require non-contaminating materials not be used in drinking water systems
• SDWA has voluntary standards• Widespread use of NSF/ANSI 61 in
model plumbing codes• Enforcement erratic or non-existent
More Problems• Standards not robust enough to cover
low-flow challenges• Many materials are legal under the
standards, but can still contaminate under many water chemistries Leaded brasses Copper
DW Treatment Dilemma• Water chemistry targets of corrosion control
often conflict with ideal conditions for DBP control
• Increasing levels of disinfectant to overcome high water age cause more DBPs to form
• High dosages of corrosion inhibitors create high nutrient loads for wastewater treatment plants
• Phosphate inhibitors are costly and sometimes in short supply
Reasons to Avoid Supplemental Building Water Treatment
• Dangerous chemicals• Requires chemical feed or other mechanical
equipment operation• Ongoing chemical/process cost• Requires dosage and background chemistry
monitoring to maintain proper conditions• May require licensed operator and state or federal
regulation as TNCWS• Even POU devices at each tap for consumption
require monitoring and replacement
What We Think is “Green”• Reduced use of non-renewable natural resources
Manufacture of plumbing materials Municipal or supplemental DW treatment chemicals
• Does not cause unhealthy levels of contamination under intended usage conditions Metals Organics Microbial
What We Think is “Green”• Does not require supplemental treatment
Entry point Point of use
• Does not create environmental challenges with waste Reduces metal loadings to WWTPs Reduces nutrient loadings to WWTPs Plumbing materials amenable to recycling/reuse
“Green Infrastructure”New Opportunity for Achievable Objectives
• Prevent the potential for contamination in the first place
• Dramatically reduce the extent of contamination
• Simplify central water treatment to provide better overall protection Metal contamination Corrosion Disinfection Disinfection byproducts (carcinogens)