Slide 1

Monroe L. Weber-Shirk S chool of Civil and Environmental Engineering Water Quality Slide 2 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? Slide 3 Germ theory Pasteur (1822-1895) Proved that microorganisms cause fermentation and disease Lister (1827-1912) Founder of antiseptic medicine and a pioneer in preventive medicine Koch (1843-1910) One of the founders of the science of bacteriology Discovered the tubercle bacillus (1882) and the cholera bacillus (1883) Slide 4 The Flush Toilets 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! Slide 5 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. Slide 6 Southwark and Vauxhall Water Company Courtesy of the National Library of Medicine Slide 7 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 Slide 8 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 Slide 9 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 Slide 10 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 Slide 11 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 Slide 12 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 Slide 13 Pathogens: Protozoa OrganismDiseaseInformation Giardia lambliaGiardiasis FDAFDA Entamoeba histolyticaAmebiasis FDAFDA Cryptosporidium parvum cryptosporidiosis FDAFDA Cyclospora cayetanensis FDAFDA Slide 14 Pathogens: Bacteria OrganismDiseaseInformation Vibrio choleraeCholeraFDAFDA Shigella spp.Shigellosis FDAFDA Salmonella typhiTyphoidFDAFDA Enterotoxigenic Escherichia coli GastroenteritisFDAFDA Slide 15 Pathogens: Viruses OrganismDiseaseInformation Hepatitis A virusHepatitisFDAFDA Hepatitis E virus Hepatitis EFDAFDA Norwalk virus viral gastroenteritis FDAFDA Slide 16 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 Slide 17 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) Slide 18 Philadelphia Typhoid Slide 19 Optimal Pathogen Dose? Slide 20 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 Slide 21 Primary Standards: (Health) Inorganic chemicals (units of mg/L) ContaminantU.S. EPA Antimony0.006 Arsenic0.01 Asbestos (fiber >10 micrometers)7 MFL Barium2 Beryllium0.004 Cadmium0.005 Chromium (total)0.1 CopperAction Level=1.3; TT 8 8 Cyanide (as free cyanide)0.2 Fluoride4.0 LeadAction Level=0.015; TT 8 8 Inorganic Mercury0.002 Nitrate (measured as Nitrogen)10 Nitrite (measured as Nitrogen)1 Selenium0.05 Thallium0.002 Slide 22 A Few Organic Chemicals (units of mg/L) see the complete list! ContaminantMCLGMCL AcrylamidezeroTT 7 7 Alachlorzero0.002 Atrazine0.0030.003 Benzenezero0.005 1-1-Dichloroethylene0.0070.007 Dioxin (2,3,7,8-TCDD)zero0.00000003 EpichlorohydrinzeroTT 7 7 Ethylbenzene0.70.7 Ethelyne dibromidezero0.00005 Lindane0.00020.0002 Polychlorinated biphenyls (PCBs)zero0.0005 Tetrachloroethylenezero0.005 Toluene11 Total Trihalomethanes (TTHMs)none 5 0.10 5 Trichloroethylenezero0.005 Vinyl chloridezero0.002 Xylenes (total)1010 Slide 23 Secondary Standards: Aesthetics ContaminantU.S. EPA, 1993WHO, 1984 Aluminum0.5-0.2 mg/L0.2 mg/L Chloride250 mg/L250 mg/L Color15 color units15 color units Copper1.0 mg/L1.0 mg/L CorrosivityNoncorrosive Fluoride2.0 mg/L Foaming agents0.5 mg/L Iron0.3 mg/L0.3 mg/L Manganese0.05 mg/L0.1 mg/L Odor (Threshold Odor Number)3 TON pH6.5-8.5 6.5-8.5 Silver0.1 mg/L Sulfate250 mg/L400 mg/L Total dissolved solids500 mg/L1000 mg/L Zinc5.0 mg/L5.0 mg/L Slide 24 ESW Social BOWLING and PIZZA 7 PM - 9 PM today! Helen Newman Slide 25 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 Slide 26 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 Slide 27 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 Slide 28 Example MCLG: Lindane 50 mg/lifetime (exposure over 70 years) RFD = ________ Estimate the MCLG 30x10 -6 MCLG=______0.0002 Slide 29 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 Slide 30 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. Slide 31 Treatment Technique (TT) When there isnt 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). Slide 32 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 Slide 33 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 Slide 34 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 Slide 35 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 Slide 36 Testing for Coliform Bacteria: Presence/Absence Tests Colisure allows testing for coliform bacteria and/or E. coli in 24 - 28 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. Slide 37 Testing for Coliform Bacteria: Membrane Filtration Membrane filter 0.45 m pores 47 mm in diameter Filter 100 mL of water to be tested through the membrane filter Slide 38 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 Slide 39 Membrane Filtration: Incubation and Results Incubate for 24 hours at 35C Coliform bacteria grow into colonies with a green metallic sheen Non-coliform bacteria may grow into red colonies Coliform concentration is __________________ 1 2 3 4 5 6 7 8 8 coliform/100 mL Slide 40 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 Slide 41 Turbidity Measurements 90 detector lamp lens sample cell 180 detector LED sample cell 170 detector Turbidity Sensors (approximate turbidity measurement) Slide 42 90 Detector Output? 90 detector 180 detector Slide 43 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? Slide 44 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