PUBH 6011 EXAMS 2 QUESTIONS AND ANSWERS
SET A+
✔✔Explain water availability and treatment challenges in developing countries - ✔✔○
Arsenic in drinking water, need to dig deeper wells; filtration techniques; mark high
arsenic wells
■ Bangladesh example of attempts to reduce surface waterborne disease...dug tube
wells...lead to massive arsenic exposure in the population (Persons w/poor nutrition esp
sensitive to arsenic effects)
■ 2/3rds of wells have high arsenic levels
○ Water collection --> a good source if don't live closer to drinking water. It influences
hygiene practices. Less likely to practice hygiene the farther an individual is away.
○ Water availability --> proportion of population using an improved drinking water has
improved but disparities exist especially between rural and urban.
○ Treatment challenges : Done at household level.
■ Chlorination - appropriate for use in areas where drinking water is taken from muddy
ponds or rivers.
■ Ceramic and Biosand Filters - unknown effectiveness against viruses, lack of residual
protection that can lead to recontamination, the need for user education to keep the
filter and receptacle clean, and potential slow flow rates.
■ SODIS- the need for pretreatment of turbid water, limited volume of water that can be
treated at once, length of time required to treat water, and the supply of plastic bottles
required.
■ Boiling- potential for recontamination after boiling and prior to consumption is high.
Water must be consumed in 24 hours.
✔✔point source vs. non-point source pollution - ✔✔Point source pollution is when
contaminants enter a water supply from a single identified source
non-point source pollution is when contaminants cannot not be traced to a source
(example: animal manure/ stormwater)
, ✔✔Biological Oxygen Demand (BOD) - ✔✔The amount of oxygen needed by
microorganisms to decompose biological wastes into carbon dioxide, water, and
minerals.
Higher BOD is associated with lower water quality because the nutrients present
provide the ingredients for eutrophication and lowering of oxygen levels in a body of
water. If oxygen levels get too low the water body can become hypoxic or even anoxic.
✔✔apply systems thinking to explain why marine "dead zones" develop - ✔✔○ Hypoxia
- Low Oxygen.
○ Anoxia- no oxygen.
○ Dead zones--> places where low oxygen is present. Occurs due to waste water
treatment, runoffs from agriculture that results in high nutrients ( nitrogen and
Phosphorous) in the water--> causes eutrophication---> bacteria breaks down algae and
due to abundance of algae increases metabolization--> depletes the oxygen in the
water.
✔✔Explain the function of each stage of a wastewater treatment facility. - ✔✔Coming
out of your house—>connected to a larger sewer system & wastewater treatment
facility.
1. Primary: First step is to run it through coarse screens- capturing grit. Grits goes to
landfill by truck
2. Primary sedimentation (aka Sedimentary tanks) - gravity + time works to separate
larger products --> get sewage sludge out of it and liquid is passed on to the next stage
3. Secondary (aeration tanks): Bacteria are breaking down products- (aerobic bacteria)
as a result compressed air is used. some of the sludge is also returned..hence
SECONDARY TREATMENT
4. Final settling Tank—>sludge again is collected and then get treated water.
5. Sometimes can go to tertiary treatment where the water is disinfected. Tertiary
treatment may be used to remove nutrients or reclaim water
6. Sludge Disposal (8 million tons of sludge a yr) --- 60% is used in fertilizer and soil
amendments Landfill Incineration Ocean dumping—now banned in the United States
7. Treated waste water: Discharged to receiving body (river, lake, etc.) back into
environment Used for irrigation Farm land, municipal parks, golf courses, and so on
Advantages Return nutrients to soil Cheap irrigation Recharge groundwater Concerns:
bacteria, metals, and so on
✔✔Explain the challenges of wastewater management in developing countries. -
✔✔Challenges arise due to lack of infrastructure, and sanitation. The size of many
SET A+
✔✔Explain water availability and treatment challenges in developing countries - ✔✔○
Arsenic in drinking water, need to dig deeper wells; filtration techniques; mark high
arsenic wells
■ Bangladesh example of attempts to reduce surface waterborne disease...dug tube
wells...lead to massive arsenic exposure in the population (Persons w/poor nutrition esp
sensitive to arsenic effects)
■ 2/3rds of wells have high arsenic levels
○ Water collection --> a good source if don't live closer to drinking water. It influences
hygiene practices. Less likely to practice hygiene the farther an individual is away.
○ Water availability --> proportion of population using an improved drinking water has
improved but disparities exist especially between rural and urban.
○ Treatment challenges : Done at household level.
■ Chlorination - appropriate for use in areas where drinking water is taken from muddy
ponds or rivers.
■ Ceramic and Biosand Filters - unknown effectiveness against viruses, lack of residual
protection that can lead to recontamination, the need for user education to keep the
filter and receptacle clean, and potential slow flow rates.
■ SODIS- the need for pretreatment of turbid water, limited volume of water that can be
treated at once, length of time required to treat water, and the supply of plastic bottles
required.
■ Boiling- potential for recontamination after boiling and prior to consumption is high.
Water must be consumed in 24 hours.
✔✔point source vs. non-point source pollution - ✔✔Point source pollution is when
contaminants enter a water supply from a single identified source
non-point source pollution is when contaminants cannot not be traced to a source
(example: animal manure/ stormwater)
, ✔✔Biological Oxygen Demand (BOD) - ✔✔The amount of oxygen needed by
microorganisms to decompose biological wastes into carbon dioxide, water, and
minerals.
Higher BOD is associated with lower water quality because the nutrients present
provide the ingredients for eutrophication and lowering of oxygen levels in a body of
water. If oxygen levels get too low the water body can become hypoxic or even anoxic.
✔✔apply systems thinking to explain why marine "dead zones" develop - ✔✔○ Hypoxia
- Low Oxygen.
○ Anoxia- no oxygen.
○ Dead zones--> places where low oxygen is present. Occurs due to waste water
treatment, runoffs from agriculture that results in high nutrients ( nitrogen and
Phosphorous) in the water--> causes eutrophication---> bacteria breaks down algae and
due to abundance of algae increases metabolization--> depletes the oxygen in the
water.
✔✔Explain the function of each stage of a wastewater treatment facility. - ✔✔Coming
out of your house—>connected to a larger sewer system & wastewater treatment
facility.
1. Primary: First step is to run it through coarse screens- capturing grit. Grits goes to
landfill by truck
2. Primary sedimentation (aka Sedimentary tanks) - gravity + time works to separate
larger products --> get sewage sludge out of it and liquid is passed on to the next stage
3. Secondary (aeration tanks): Bacteria are breaking down products- (aerobic bacteria)
as a result compressed air is used. some of the sludge is also returned..hence
SECONDARY TREATMENT
4. Final settling Tank—>sludge again is collected and then get treated water.
5. Sometimes can go to tertiary treatment where the water is disinfected. Tertiary
treatment may be used to remove nutrients or reclaim water
6. Sludge Disposal (8 million tons of sludge a yr) --- 60% is used in fertilizer and soil
amendments Landfill Incineration Ocean dumping—now banned in the United States
7. Treated waste water: Discharged to receiving body (river, lake, etc.) back into
environment Used for irrigation Farm land, municipal parks, golf courses, and so on
Advantages Return nutrients to soil Cheap irrigation Recharge groundwater Concerns:
bacteria, metals, and so on
✔✔Explain the challenges of wastewater management in developing countries. -
✔✔Challenges arise due to lack of infrastructure, and sanitation. The size of many
