ENVR 133 ENVIRONMENTAL HEALTH MICROBIOLOGY TAKE-HOME FINAL
Name (Print)______. Honor Pledge (Sign)______
This take-home final exam must be turned in by COB on May 4, 2006
YOU MAY USE PUBLISHED OR INTERNET LITERATURE, INCLUDING BOOKS, JOURNAL ARTICLES, REPORTS AND THE LIKE. HOWEVER, EACH OF YOU ARE
EXPECTED TO WORK INDEPENDENTLY AND WITHOUT CONSULTATION WITH OTHERS IN CONCEPTUALIZING, FORMULATING AND PREPARING YOUR ANSWERS. PLEASE MAKE YOUR ANSWERS NO LONGER THAN 5 TYPEWRITTEN, DOUBLESPACE PAGES PER QUESTION.
YOU MUST ANSWER ANY THREE (3) OF THE FOLLOWING SIX (6) QUESTIONS
1. Bacteria and other cellular microbes are subject to phenomena that have been referred to as "injury", "stress" or sublethal damage.
a. In the context of public health concerns about enteric pathogens in environmental samples ingested by humans (water, food, etc.), what are the potential consequences such injury or sublethal damage on the determination of the "true" number of viable and potentially infectious microbes in such samples as drinking water, bathing water, shellfish and other foods?
b. To what extent may the actual risks to human health be underestimated because injured
indicator organisms go undetected in routine monitoring using culture methods and that injured enteric pathogens pose a health risk.
c. What kind of evidence is available or can be applied to show that injury, stress or other
sublethal damage is causing microbial underestimation compared to the conventional culture
methods used for bacterial indicators or pathogens?
d. What is the evidence that microbial injury results in underestimation of pathogen exposure and adverse health effects of pathogens from ingestion of water and/or food?
e. How does this phenomenon impact or relate to microbial standards for indicator bacteria in water and food?
f. In your estimation how big a problem is this?
g. What do your recommend, if anything, to address this problem in the way of research, surveillance or other investigational approaches?
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2. Disinfection of drinking water using free chlorine and chloramines is widely used in the USA and many other countries. Please answer the following questions concerning the use of these disinfectants.
a. How capable are these disinfectants in inactivating the various microorganisms of public health significance in drinking water and how do they compare in microbiocidal efficacy?
b. What are the anticipated or reported inactivation kinetics of key waterborne viruses, bacteria and parasites by free chlorine and chloramines in terms of inactivation rates and extents?
c. What biological, chemical and physical factors influence microbial inactivation by free chlorine and monochloramine?
d. What are the mechanisms of microbial inactivation by free chlorine and chloramines and are they adequately elucidated?
e. What other disinfectants are available for use in drinking water and how do they compare to free chlorine and chloramines in terms of efficacy against different waterborne pathogens and the provision of a disinfectant residual?
f. If you had to select disinfection treatment for a city of 10,000 people using a ground water source for its drinking water supply, which of these disinfectant(s) would you recommend and why? What other treatment, if any, would you apply to this water and why?
3. A city of 100,000 people in the arid southwest is faced with a severe and chronic water shortage. They have no additional water resources that can be developed from either surface or
ground sources, except their sewage. Presently, they treat their sewage (secondary treatment by activated sludge and chlorine disinfection (10 mg/l dose, 60' contact time) and simply
discharge it to a river (usually an otherwise dry riverbed).
The city is considering the emergency reclamation and reuse of their sewage for beneficial purposes, including its use as both potable and nonpotable water supply. They propose to use advanced treatment processes to reclaim the sewage. As the authority on environmental health microbiology, the city has asked you to address the following questions.
a. What are the potential microbial risks of using reclaimed wastewater? Which microorganisms are most important as health risks?
b. City politicians and managers want to know if Mumps is one of the microbes posing a risk from reclaimed sewage. What is your judgment of such a risk and what is the basis for your judgment of this risk?
c. What beneficial uses of the reclaimed water would you recommend or allow?
Would this include use as: (i) drinking water? (ii) irrigation water for parks, other greenspace and household lawns? (iii) industrial cooling water?
d. What do you recommend for treatment of the wastewater to produce reclaimed water for the recommended beneficial uses?
e. Do you recommend the same treatment scheme for all beneficial uses of the water?
f. What are the expected microbial reductions of the major classes of pathogens of public health concern for each of the treatment processes you recommend and the entire treatment scheme(s), beginning with the raw sewage? If possible, show calculations and provide quantitative data.
g. What types of management, operations, surveillance and other measures would you recommend to make sure that the reclaimed water was consistently safe? Would this include maximum allowable limits of specific pathogens, pathogen groups and/or microbial indicators? If so, which ones, at what levels and why?
4. A city of 100,000 in the Piedmont region of North Carolina is experiencing an explosive outbreak of acute gastroenteritis that has developed in the community in a very short period of time. The outbreak is affecting all age groups, with people developing several of the following symptoms and signs: diarrhea, nausea, vomiting, abdominal pain, loss of appetite, low-grade fever and malaise. The outbreak may be due to a common source, such as the drinking water supply, food or other common exposure routes. However, this is currently unknown.
As one of the state's public health epidemiologists-microbiologists, you are called in to immediately take charge of the situation, investigate, determine what to do, coordinate actions, determine the cause of the outbreak and propose measures to prevent further cases. You are charged with writing and implementing a detailed plan of action for all parties.
Develop a plan of action, starting with the launching of the investigation, the investigation team and its roles and responsibilities, the investigational approaches and analytical methods, the determination of disease risk and burden and the source(s) of pathogen exposure, the analytical approach and methods to identify the causative pathogen, and the measures to control and further prevent the outbreak or its spread to other communities. A description of the implementation of these activities and your interpretation of the possible findings is the answer to this question.
Everybody is waiting for you to take the lead on this...NOW!
5. A new city of 10,000 people is being planned that has a raw water source containing Cryptosporidium parvum at a concentration of 10 oocysts per 10 liters of water. Currently the city is proposing to use only free chlorine disinfection (with 3 mg/l dose and 30 minute contact time) to treat its water. As an expert on drinking water and health, you are asked to do a risk assessment for cryptosporidiosis and to recommend any changes in the water supply that may be needed to reduce the cryptosporidiosis risk to consumers.
a. Knowing that the water contains 10 oocysts per 10 liters and assuming people drink 2 liters of water per day what is the daily and annual risks of cryptosporidiosis per person? Be sure to list any additional assumptions you have made in developing your in your answer and show any relevant calculations.
b. Is the annual Cryptosporidium parvum infection risk less than 1 in 10,000 (<10-4) per year? What concentration of C. parvum in the water would constitute a 1 in 10,000 annual risk level?
c. If the proposed chlorinated water supply exceeds the 1 in 10,000 (<10-4) annual risk level, to what extent would the expected risk level have to be reduced and how would you propose to reduce the risk to this acceptable level? Specifically, how much (what % or log10) C. parvum oocyst reduction from the water would be needed and what treatment process or processes would you propose to reduce the risk from C. parvum to the acceptable level?
6. There is growing concern that manure (feces and urine) from swine and other concentrated/confined animal feeding operations (CAFOs) is contaminating surface and ground water and possibly food crops will human enteric pathogens and other pollutants. For this reason, NC has imposed a moratorium on new swine operations that use the currently approved swine waste management system, which consists of storage in an anaerobic lagoon and land application by spray irrigation at agronomic rates for nitrogen.
Efforts are underway to identify and implement alternative swine waste management systems that would better control pathogens and other contaminants. As an authority on waste treatment and pathogens, you have been tasked with choosing one or more alternative swine waste treatment technologies or systems that would be recommended for use to reduce pathogens and otherwise prevent environmental pollution from swine farms. You are asked to address the following questions.
a. What are the types of pathogens that could be present in swine manure and at what levels or concentrations?
b. What treatment technologies and systems and operating conditions for them would you recommend to reduce pathogens in the swine waste and why would you recommend these?
c. There are going to be liquid and solid residuals from the waste treatment technology or system. What uses or disposal options would you allow for these materials? Would you require criteria and standards for their microbial quality? If so, what would these criteria and standards be?
d. What safeguards and specific management requirements would you recommend to document that these new technologies and systems are working properly and are not causing environmental contamination or posing human health risks from pathogens?
e.
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