Presentation on theme: "Monroe L. Weber-Shirk S chool of Civil and Environmental Engineering Water Quality."— Presentation transcript:
Monroe L. Weber-Shirk S chool of Civil and Environmental Engineering Water Quality
History of our understanding of waterborne disease Brief history of water treatment Drinking Water Standards: how do we decide what is allowed in the water we drink?
Germ theory Pasteur ( ) Proved that microorganisms cause fermentation and disease Lister ( ) Founder of antiseptic medicine and a pioneer in preventive medicine Koch ( ) One of the founders of the science of bacteriology Discovered the tubercle bacillus (1882) and the cholera bacillus (1883)
The Flush Toilet’s Connection to Disease In the early 1800s new flush toilets and sewers carried the waste directly into rivers and streams London drained its raw sewage into and withdrew its drinking water from the Thames River, both without any treatment. Several of the drinking water intakes were below sewage outfalls!
Southwark and Vauxhall Water Company In 1850, the microbiologist Arthur Hassall wrote of the River Thames water they were using,"...a portion of the inhabitants of the metropolis are made to consume, in some form or another, a portion of their own excrement, and moreover, to pay for the privilege." Next Cartoon presents John Edwards, owner of the Southwark Water Company, posing as Neptune ("Sovereign of the Scented Streams"). He is seen crowned with a chamber-pot, seated on a stool on top of a cesspool which doubles as the water-intake for the Southwark Water Company customers in south London.
Southwark and Vauxhall Water Company Courtesy of the National Library of Medicine
Drinking Water Treatment and Germ Theory 1829: First sand filter used to treat some of London's drinking water 1850: John Snow established the link between drinking water (from a contaminated well) and Cholera 1872: Poughkeepsie, NY installs first filter in US 1885: Sand filters are shown to remove bacteria 1892: Cholera outbreak in Hamburg, Germany
1892 Cholera outbreak in Hamburg Germany Large outbreak of Cholera in Hamburg 17,000 cases; 8,600 deaths Very few cases in neighborhoods served by Altona's filtered water supply Hamburg's sewers were upstream from Altona's intake! Altona's water intake and filter beds Hamburg's sewer outfalls Hamburg Altona Elbe River Hamburg's water intake
Altona vs. Hamburg: Cholera Cases Hamburg Altona Cases in Altona acquired in Hamburg Cholera cases Received water from Altona Cholera was waterborne Slow sand filtration may have protected Altona Conclusions
Disease Definitions Pathogen: an agent that causes infection in a living host. It acts as a parasite within the host or host cells and disrupts normal physiological activities Infection: growth of a disease-producing organism within the host Virulence: ability of the pathogen to inflict damage on the host
Epidemic An occurrence of disease that is temporarily of high prevalence An epidemic occurring over a wide geographical area is called a pandemic Epidemics require _________________________ __________________________ an infected host a number of non-infected potential hosts a mechanism of pathogen transfer
Waterborne Threats to Human Health Infectious diseases caused by viruses, bacteria, protozoa (pathogens) Noninfectious diseases _____: caused by short term exposure to harmful chemicals _______: caused by long term exposure to harmful chemicals low levels of exposure to certain chemicals over a long period of time may cause cancer, liver and kidney damage, or central nervous system damage acute chronic
Pathogens: Viruses OrganismDiseaseInformation Hepatitis A virusHepatitisFDAFDA Hepatitis E virus Hepatitis EFDAFDA Norwalk virus viral gastroenteritis FDAFDA
Propose a Drinking Water Standard You have been granted the authority to regulate drinking water quality. Create a standard for the concentrations of disease-causing organisms in drinking water. In the absence of technological/economic constraints, Which pathogens would you regulate? What concentration would you choose? Given technological and economic constraints how might you change your regulation? Setting the standards
Optimal Pathogen Exposure Should we be exposed to small doses of pathogens so we build up our resistance? How could we build pathogen exposure into our daily lives? Potential application Common cold (continues to mutate) Norwalk virus (Immunity, however, is not permanent and reinfection can occur after 2 years) HIV (no immunity)
Optimal Pathogen Dose?
Safe Drinking Water Act (1974) Specific standards for drinking water primary (__________) secondary (__________ upper limits for non-health related parameters) Applicable to all water supplies serving more than 25 people or having 15 or more service connections Enforced by U.S. Environmental Protection Agency mandatory suggested
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How do they determine MCLGs? Determine NOAEL (No Observed Adverse Effect Level) by experimental data on humans or animals Divide NOAEL by uncertainty factor (UF) UF = 10 when good data on humans available UF = 100 when good data on animals available UF = 1000 when no good data available To get reference dose Determine drinking water equivalent level
Setting the Standards (Non- Carcinogens) For chemicals that can cause adverse non-cancer health effects, the MCLG is based on the reference dose. A reference dose (RFD) is an estimate of the amount of a chemical that a person can be exposed to on a daily basis that is not anticipated to cause adverse health effects over a person's ________. In RFD calculations, sensitive subgroups are included, and uncertainty may span an order of magnitude. lifetime
MCLG Calculations RFDreference dose adult body weight (70 kg) M daily water consumption (2 liters) Drinking Water Equivalent Level DWEL Q MCLG Maximum Contaminant Level Goal
Example MCLG: Lindane 50 mg/lifetime (exposure over 70 years) RFD = ________ Estimate the MCLG 30x10 -6 MCLG=______0.0002
Primary Standards : (Health) Related to Microorganisms ContaminantMCLGMCL CryptosporidiumzeroTT 3 3 Giardia lambliazeroTT 3 3 LegionellazeroTT 3 3 Viruses (enteric)zeroTT 3 3 Heterotrophic plate countN/ATT 3 3 Total Coliformszero5.0% 4 4 TurbidityN/ATT 3 3 Cause disease Indicators Interferes with disinfection
Microbial Contaminants For microbial contaminants that may present public health risk, the MCLG is set at zero because ingesting one protozoa, virus, or bacterium may cause adverse health effects. EPA is conducting studies to determine whether there is a safe level above zero for some microbial contaminants. The MCL is set as close to the MCLG as feasible, (the level that may be achieved with the use of the best available technology, treatment techniques, and other means which EPA finds are available), taking cost into consideration.
Treatment Technique (TT) When there isn’t an economical and technically feasible method to measure a contaminant, a Treatment Technique is set rather than an MCL. A treatment technique is an enforceable procedure or level of technological performance which public water systems must follow to ensure control of a contaminant. Surface Water Treatment Rule (disinfection and filtration) Lead and Copper Rule (optimized corrosion control).
Indicator Organisms Impractical to detect, differentiate, or enumerate all of the pathogenic organisms that may be present in water Pathogenic organisms share a common fecal origin therefore limit fecal contamination of water need a measure of fecal contamination
Ideal Indicator Organism Be present when pathogens are Not reproduce in the environment Survive at similar rate to pathogens Correlate quantitatively with pathogens Be present in greater numbers than pathogens Be easily, accurately and quickly detected
Fecal Contamination Indicator: Coliform Bacteria Normally are not pathogenic Always present in the intestinal tract of humans and excreted in very large numbers with human waste Easier to test for the presence of coliforms rather than for specific types of pathogens Are used as indicator organisms for measuring the biological quality of water
Indicator Organism Failure Relative viability of pathogens and indicator organisms Effect of treatment processes Some pathogens survive for a longer time in the environment (raw water concentrations are different) Some pathogens are resistant to chlorine
Testing for Coliform Bacteria: Presence/Absence Tests Colisure allows testing for coliform bacteria and/or E. coli in hours. The detection limit of ColiSure is 1 colony forming unit (CFU) of coliform bacteria or E. coli per 100 mL of medium. If coliform bacteria are present, the medium changes color from yellow to a distinct red or magenta. If E. coli are present, the medium will emit a bright blue fluorescence when subjected to a long wave (366 nm) ultraviolet (UV) light.
Testing for Coliform Bacteria: Membrane Filtration Membrane filter 0.45 μm pores 47 mm in diameter Filter 100 mL of water to be tested through the membrane filter
Membrane Filtration Petri dish with sterile absorbent nutrient pad Add 2 mL of m- endo broth (selective media) Place membrane filter in the petri dish on top of the nutrient pad
Membrane Filtration: Incubation and Results Incubate for 24 hours at 35°C Coliform bacteria grow into colonies with a green metallic sheen Non-coliform bacteria may grow into red colonies Coliform concentration is __________________ coliform/100 mL
Turbidity A measure of the scattering of light by particles in a suspension A turbid water sample appears cloudy or “dirty” High turbidity is the result of lots of light scattering caused by the particles in suspension Measured in NTU (Nephelometric Turbidity Units) cloud
Coagulant Dose How will you determine coagulant dose for your water treatment plant? What will you monitor to decide if coagulant dose should be increased or decreased? Why is it hard to use feedback (data from a sensor) to set the coagulant dose?
Summary The causes of waterborne disease have been identified Indicator organisms are used to measure the extent of fecal contamination Standards for microbiological and chemical contaminants have been set by US EPA Waterborne disease continues to be a significant public health concern especially for the poorest 2 billion