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Questions and Answers
What are the primary sources of domestic wastewater?
What are the primary sources of domestic wastewater?
What is the major concern regarding untreated domestic wastewater?
What is the major concern regarding untreated domestic wastewater?
What percentage of domestic sewage is typically water?
What percentage of domestic sewage is typically water?
What is Biological Oxygen Demand (BOD) a measure of?
What is Biological Oxygen Demand (BOD) a measure of?
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Which of the following is NOT a component of domestic sewage?
Which of the following is NOT a component of domestic sewage?
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What happens to the environment if wastewater is directly released into a stream?
What happens to the environment if wastewater is directly released into a stream?
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How are BOD levels typically measured?
How are BOD levels typically measured?
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What is the typical composition of solids in wastewater produced in communities, such as Washington DC?
What is the typical composition of solids in wastewater produced in communities, such as Washington DC?
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What is BOD5 primarily used to measure?
What is BOD5 primarily used to measure?
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What is the primary goal of wastewater treatment plants?
What is the primary goal of wastewater treatment plants?
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In secondary treatment, what is primarily decreased?
In secondary treatment, what is primarily decreased?
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Which type of microorganisms are responsible for producing methane during anoxic secondary waste treatment?
Which type of microorganisms are responsible for producing methane during anoxic secondary waste treatment?
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Which of the following describes the trickling filter method of aerobic secondary waste treatment?
Which of the following describes the trickling filter method of aerobic secondary waste treatment?
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What significant waste reduction occurs during aerobic secondary waste treatments?
What significant waste reduction occurs during aerobic secondary waste treatments?
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What is a characteristic feature of an anoxic sludge digester?
What is a characteristic feature of an anoxic sludge digester?
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Which of the following best explains the role of biofilm in aerobic treatments?
Which of the following best explains the role of biofilm in aerobic treatments?
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What is the primary role of nitrifying bacteria in sewage treatment?
What is the primary role of nitrifying bacteria in sewage treatment?
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Which group of bacteria is responsible for the conversion of nitrite to nitrate?
Which group of bacteria is responsible for the conversion of nitrite to nitrate?
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What characteristic of fecal coliforms makes them important as an indicator organism?
What characteristic of fecal coliforms makes them important as an indicator organism?
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Why is monitoring effluents and the surrounding environment crucial in sewage treatment?
Why is monitoring effluents and the surrounding environment crucial in sewage treatment?
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What process do methanogens primarily participate in within sewage treatment?
What process do methanogens primarily participate in within sewage treatment?
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Which of the following best describes nitrosomonas and nitrosolobus?
Which of the following best describes nitrosomonas and nitrosolobus?
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Which characteristic is NOT a criterion for an effective indicator organism?
Which characteristic is NOT a criterion for an effective indicator organism?
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What key enzyme is involved in the oxidation of ammonia to nitrite by AOB?
What key enzyme is involved in the oxidation of ammonia to nitrite by AOB?
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What does the MPN analysis for quantifying coliforms NOT assess?
What does the MPN analysis for quantifying coliforms NOT assess?
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Which test part follows the presumptive test in the MPN method?
Which test part follows the presumptive test in the MPN method?
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What is a possible consequence of high MPN results in recreational waters?
What is a possible consequence of high MPN results in recreational waters?
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What does the completed test in the MPN method analyze?
What does the completed test in the MPN method analyze?
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Which medium inhibits gram positive organisms during the MPN Confirmed Test?
Which medium inhibits gram positive organisms during the MPN Confirmed Test?
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In the example of glucose fermenters, how many organisms are reported per 100 ml?
In the example of glucose fermenters, how many organisms are reported per 100 ml?
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What does the MPN index primarily report?
What does the MPN index primarily report?
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Which outcome is categorically important for drinking water systems when coliforms are detected?
Which outcome is categorically important for drinking water systems when coliforms are detected?
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Study Notes
Wastewater Treatment
- Wastewater is a mixture of water and organic waste from both industrial and domestic sources.
- Domestic sewage is primarily comprised of water with a very small percentage of solids, including proteins, carbohydrates, and fats.
- If untreated, wastewater released into the environment can lead to water contamination, oxygen depletion (lowering dissolved oxygen levels) due to high organic loads, and potential fish kills.
Biological Oxygen Demand (BOD)
- BOD is a measure of oxygen depletion in wastewater.
- This is determined by measuring the oxygen consumption over a five-day period through a bioassay.
- Domestic sewage typically has a BOD5 of 150-200 mg/L, while industrial waste can be significantly higher depending on the source, ranging from 5000-6000 mg/L for milk processing to 10,000-15,000 mg/L for pulping operations.
Wastewater Treatment Plant
- The goal of a wastewater treatment plant (WWTP) is to protect human health, preserve natural resources, and prevent ecological damage.
- This is accomplished by removing energy-rich organic matter from the wastewater before discharge into the environment.
- WWTP utilize technologies to lower the occurrence of water-borne diseases.
Sewage Treatment Processes
- Primary Treatment: Non-biological, primarily focuses on removing solid material.
- Secondary Treatment: Decreases dissolved organic carbon (DOC), utilizes biological processes.
- Anoxic Secondary Treatment: Utilizes an anoxic sludge digester, which breaks down solid waste via fermentation and produces methane.
- Aerobic Secondary Treatment: This involves utilizing aerobic microorganisms to break down organic matter.
Aerobic Secondary Treatment Methods
- Trickling Filter: Sewage is trickled over a bed of crushed rocks, providing surfaces for microbes to attach and mineralize waste.
- Activated Sludge: Air is bubbled through wastewater, promoting the growth of bacterial flocs, primarily composed of Zoogloea ramigera. These flocs settle out after the treatment phase.
Important Microbes in Sewage Treatment
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Nitrifying Bacteria: Aerobes responsible for converting nitrogenous waste into nitrate. This process occurs in two steps:
- Ammonia Oxidizing Bacteria (AOB): Convert ammonia (NH3) to nitrite (NO2-) through the use of ammonia monooxygenase (AMO) and hydroxylamine oxidoreductase (HAO) enzymes.
- Nitrite Oxidizing Bacteria (NOB): Convert nitrite (NO2-) to nitrate (NO3-) using the Nor enzyme complex.
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Denitrifying Bacteria: Anaerobes that convert nitrate to nitrogen gas (N2).
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Methanogens: Primarily archaea, generate methane from acetate or use hydrogen and carbon dioxide to produce methane.
Environmental Monitoring
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Monitoring effluents and the surrounding environment is vital to:
- Assess the effectiveness of the wastewater treatment process.
- Monitor levels of organic matter, nutrients (C, N, P), metals and microorganisms.
- Evaluate the toxicity of effluents.
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It is often difficult to directly monitor specific pathogens due to their complexity.
Indicator Organisms
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Indicator organism: A microbe that can be easily cultured and indicates the presence of a potential pathogen or correlates with a specific health concern.
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Criteria for Indicator Organism Selection:
- Consistency in fecal presence and higher concentrations than pathogens.
- Inability to multiply outside the human intestinal tract.
- Resistance to environmental conditions and disinfection, equal to or greater than pathogens
- Ease of culturing and quantification, and distinguishability from other microbes
- Strong correlation to pathogen levels or measurable health hazards
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Coliforms: Facultatively aerobic, gram-negative, non-spore-forming, rod-shaped bacteria that ferment lactose with gas production. Often found in the intestinal tract (e.g., E. coli, Klebsiella, Citrobacter, Enterobacter, Serratia, Yersinia).
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Fecal Coliforms: Thermotolerant coliforms (44.5˚C) represent about 20% of total coliforms.
Most Probable Number (MPN) Analysis
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MPN analysis quantifies total coliform bacteria in water samples through three sub-tests.
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Presumptive Test: Determines the presence of coliforms by testing for gas producers through serial dilution of lactose broth tubes.
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Confirmed Test: Confirms the presence of coliforms through inoculation of positive presumptive test tubes with brilliant green lactose bile broth (BGLB).
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Completed Test: Streak plating on eosin methylene blue (EMB) plates to identify coliforms from confirmed test positive samples.
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High MPN results in water sources can lead to beach closures (e.g., in recreational waters) and trigger further investigation in drinking water systems.
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Description
Explore the essential concepts of wastewater treatment, including the composition of domestic sewage and its environmental impacts. Understand the significance of Biological Oxygen Demand (BOD) in measuring oxygen depletion in wastewater. This quiz is vital for those studying environmental science or water management.
