View
228
Download
0
Tags:
Embed Size (px)
Citation preview
Steve Reiber, Ph.D. • HDR Engineering • Seattle, WA
Past History/Future ChallengesWater Treatment
Legionella
Evolutionary Change in Water treatment – The History of a Developing Market
Early water treatment engineers describe the first
dirt molecule.
Take-Away Points
• Despite predictions to the contrary, the cost of new technology (especially membranes) will not increase the cost of water treatment.
• When quality is factored in, the cost of water treatment will actually decline.
• Conventional sand filtration will be phased out in favor of low-pressure membranes. (This represents a 10 BGD market.)
Disinfection: The Most Important Treatment Step
• Gate Houses and Chlorination Plant at Boonton Reservoir (Jersey City),circa 1908
DyNasand Filter
Actiflow
Deep Bed Mono-Media
Slow Sand Filtration
(Germany 1820)
Rapid Sand Filtration
(Chicago 1900)
River Bed Filtration
(Roman Times)
Evolution of Water Filtration Technology
Rapid sand filters are no longer the most cost-effective polishing step.
Cellulosic Membranes (1980)
• New water supplies are inferior.
• Fear of waterborne disease.
• SDWA regulations
• Expensive infrastructure replacement
Numerous factors are influencing these changes.
Market Drivers
The Water-Consuming Public is Aware (and Wary)
Well-publicized “events”
Bottled water sales increase dramatically
Waterborne Disease Outbreaks Cause Irreparable Damage to Public & to PWSs
Year State/Territory Cause of Disease No. of People Affected
1985 Massachusetts Giardia lamblia (protozoan) 703 illnesses
1987 Georgia Cryptosporidium parvum (protozoan) 13,000 illnesses
1987 Puerto Rico Shigella sonnei (bacterium) 1,800 illnesses
1989 Missouri E. coli 0157 (bacterium) 243 illnesses / 4 deaths
1991 Puerto Rico Unknown 9,847 illnesses
1993 Missouri Salmonella typhimurium (bacterium) 650 illnesses / 7 deaths
1993 Wisconsin Cryptosporidium parvum (protozoan) 400,000 illnesses 50+ deaths
1998 Texas Cryptosporidium parvum (protozoan) 1,400 illnesses
1999 New York E. coli 0157 (bacterium) 150 illnesses / 1 death
2000 Ontario E. coli 0157 (bacterium) 1,000 illnesses / 7 deaths
Source: HDR’s Handbook of Public Water Systems
Public Health IssuesPathogenic bacteria, viruses and protozoa in water and wastewater represent potential risks to public health.
(Giardia) (Cryptosporidium)
Viruses
(Hepatitis, Polio)
Bacteria
(E.coli)
Protozoa
Historical mortality from waterborne diseases exceeds the current mortality rates
of all diseases combined.Typhoid Fever Mortality in Chicago (1860-1950)Typhoid Fever Mortality in Chicago (1860-1950)U.S. Leading Causes of Death (1990)U.S. Leading Causes of Death (1990)
Viruses: smallest (0.02-0.3 µm diameter); simplest:
nucleic acid + protein coat (+ lipoprotein envelope)
Bacteria: 0.5-2.0 µm diameter; prokaryotes; cellular; simple internal org.; binary fission.
Protozoa: most >2 µm - 2 mm; eucaryotic; uni-cellular;
non-photosynthetic; flexible cell memb.; no cell wall; wide range of sizes and shapes; hardy cysts and oocysts;
flagellates (Giardia sp.), amoebae, ciliates, sporozoans (Cryptosporidium sp.) and microsporidia.
C. parvum oocyst
~5 um
Classes of Microorganisms:The Microbial World
What is a low-pressure membrane?
Membranes can remove anything that is smaller than the pores.
Giardia
Cryptosporidium
A Short History of Membrane TechnologiesMembrane treatment is not new.
Cellulosic membranes have been in use for four decades.
What is new is that membrane systems are now affordable!
Membrane TreatmentWhat is driving the technology?
• Competitive costs
• Complete microbial barrier
• Improved organics removal
• Small space requirements
• Reduced solids
• Automation
Improved materials are the key to cost-effective performance.More recent polymeric materials are more robust than cellulosic materials.
Teflon
Polypropylene (PP)
Polyvinylidenefluoride (PVDF)
Polysulphone (PSf)
Chemical and
Mechanical
Resistance
They foul more easily, but can be regularly and vigorously cleaned.
Growth in drinking water low-pressure systems is
exponential.
Combined
Microfilter
Nanofiltration
Ultrafilter
Capital costs for membrane technology continues to drop.
*Per gal/d of Installed Capacity
*
Membrane Architecture is Evolving
Encased systems trap solids, are difficult to backwash and cannot be used with high concentrations of coagulants or adsorbants, but offer high flux rates!
Open systems are easier to backwash, but generally have lower flux rates!
Hollow Fiber Encased Membranes
Submerged MembranesZenon’s ZeeWeed Process
Integration with Other Processes
• TOC & DBPs (Coagulant/PAC/GAC)
• Taste & Odor (Aeration/PAC/GAC/ClO2)
• Soluble Fe & Mn (Oxidants)
• Arsenic (Ferric coagulants)
Size Exclusion Device
Cellulosic Systems
Immersed membrane
Treated water
InflowCoagulant
Sorbant
PVDF and Fluoropolymer systems
Residuals
Solids Contact Separation System
Particle Removal vs. Dissolved Organics Removal
Evolution
Membrane processes are not trouble free!
Cellulose acetate (CA)
Poly(m-phenylene isophtalamide) (Normex)
Polyacrylonitrile (PAN)
Polyethersulphone (PES)
Polysulphone (PSf)
Teflon
Polyvinylidenefluoride (PVDF)
Polypropylene (PP)
Polycarbonate (PC)
Hydrophilic
Fouling Resistant
Hydrophobic
Fouling Susceptible
Hydrophobicity
Support Substrate
Membrane
Fouling by organic material is the most serious threat to membrane operations.
The dense NOM gel-like layer reduces capacity and fouls an unprotected membrane.
Fouling at 20 hours; 79% flux reduction
Membranes do fail. However, failure is never catastrophic – less serious than microbial penetration of rapid sand filter beds.
• Membranes fail incrementally – one fiber at a time.
• Statistically, individual fiber breaks are insignificant to the overall microbial water quality.
What Will Not Change!
• Urban-Industrial society depends on a safe and abundant supply of water. It is the most important public health function - bar none!!!
• Water Wars are not imminent.
Price
Cap
acit
y
SupplyDemandNon-Non-
Commodity Commodity Pricing of Pricing of Water!!Water!!
Water Industry/Distribution System Issues
The American Water Industry is Not Being Privatized!
Municipal advocacy supplants privatization efforts
Merchant water will be limited to speculative markets.
Distribution Water Quality is Improving
98
99
100
1990 1992 1994 1996 1998 2000 2002 2004 2006
Almost 100% of national samples tested met health-based and aesthetic standards for drinking water
The number of tests failing water quality standards has fallen by 60% since 1992
Com
plia
nce
Perc
ent
The Cost Efficiency of Public Water Purveyors is Increasing
0
1
2
3
4
1.00
Misc. Cost
Capital Cost
Operating Cost
1990 1995 2000 2005
$ / 1
000
Gal
.
Public drinking water is a remarkable bargain
Efficiencies derive primarily from manpower and technology
It is still inexpensive despite more stringent regulations and dwindling supplies
Inflation-Adjusted Homeowner Costs
0
1
2
3
1 2
1990 2000
Cost as a % of Household Income
Waterborne Disease Outbreaks are Decreasing. Distribution System Contribution is Increasing
1971 – 1974
1975 – 1978
• Most distribution failures are related to cross-connection and back siphonage.
• Magnitude of outbreaks – 180 illnesses per event.
1979 – 1982
1983 – 1986Source: Lee and Blackburn, 2004
1987 – 1990
1991 – 1994
1995 – 1998
1999 – 2000
2001 – 2002
Disease and Distribution System Evidence shows that current endemic levels of Evidence shows that current endemic levels of
gastrointestinal diseases are associated with gastrointestinal diseases are associated with the consumption of tap waterthe consumption of tap water
The typical disease symptoms are generally The typical disease symptoms are generally mild, short term, and clear spontaneouslymild, short term, and clear spontaneously
The organisms causingThe organisms causingthese diseases arethese diseases arecultured in the distributioncultured in the distributionsystem (not the raw water)system (not the raw water)
Challenge – Many 20th century iron distribution mains are approaching the end of their service lives.
Projected annual replacement needs for transmission lines and distribution mains. Source: EPA 2002)
• Average post-WWII pipe service life ≈ 75 years.• 19th century cast iron pipe service life ≈ 120 years• Drinking water infrastructure spending to reach $6 billion per year by 2010.
Challenge - The Bottled Water Industry Continues to Grow
Year GPCAnnual % Change
2000 17.3
2001 18.8 9.7
2002 20.9 10.7
2003 22.4 7.3
2004 24.0 7.4
2005 25.7 7.1Fairly, or not, the continued success of bottled water creates the perception of a growing deficiency (“lack of purity”) in our public water system.
7%
11%
35%
12%
35%
7% Taste
11% Other
35% Worried about tap water safety
35% Substitute for other beverages
12% Worried about tap water safety
and substitute for other beverages
Why People Drink Bottled WaterBottled Water MarketU.S. Per Capita Consumption