Please check all statements about health-based targets that are correct.

1. A health outcome expressed in the number of DALYs per year.

2. A specific level of pathogen removal.

3. A health outcome expressed in the number of cancer cases per lifetime exposure.

4. A health outcome expressed in the number of ingested pathogens per year.

 

3 log reduction means that the number of bacteria is...

1. 100 times smaller

2. 1000 times smaller

3. 10000 times smaller

4. 100000 times smaller

 

Which one of those coagulants should be used in combination with another coagulant to be effective?

1. Nirmali seeds

2. Prickly pear cactus

 

What processes are involved in membrane filtration?

1. Electrostatic effects

2. Biological activity

3. Size exclusion

Please check all pathogens that are usually removed by micro filtration.

1. Cryptosporidium

2. Entamoeba hystolitica

3. Dracunculus medinensis

4. Vibrio cholerae

5. Rotavirus

It is important to conduct a quality control for every single produced ceramic pot filter. What are usual procedures to assure quality?

1. Visual tests

2. Audio tests

3. Odor tests

4. Microbiological tests

 

Homework quiz 2

 

Question 1

Can an LRV (Log reduction value) be negative?
No
Yes

 

Question 2

1 gram of faeces from an infected person may contain 10,000,000 Cryptosporidium cysts. If all of that 1 gram of faeces were mixed in 1 liter of water, how many LRV (Log reduction values) would be needed to completely remove the cysts?
> 7 LRV
> 4 LRV
> 5 LRV
> 9 LRV

 

Question 3

Faecally derived pathogens are the principal concerns in setting health-based targets for microbial safety. It is not sufficient to measure the water quality only one time for verification. Why?
Microbial water quality often varies rapidly but not over a wide range.
Microbial water quality often varies rapidly and over a wide range.
Microbial water quality often varies slowly but over a wide range.

 

Question 4

Ceramic filters show very variable removal effectiveness depending on the class of pathogens. What LRV approximately can be achieved with ceramic filters regarding the removal of viruses?
0-2 LRV
2-5 LRV
3-4 LRV
6 LRV

 

Question 5

An example of a household membrane filter is Vestergaard-Frandsen’s LifeStraw. With a pore size of 20 nm, in which filtration category does it fall, and which classes of pathogens can it remove?

  It falls into the category of ultrafiltration. It can remove protozoa, bacteria and viruses.
It falls into the category of microfiltration. It can remove protozoa and bacteria.
It falls in the category of nanofiltration. It can remove protozoa, bacteria and viruses.
It falls into the category of microfiltration. It can remove protozoa, bacteria and viruses.

 

Question 6

Good operating procedures are important to maintain the performance level of a biosand filter. Which of the following are good operating procedures? Please check all that are correct..

A consistent water source should be used.
The flow rate shouldn’t be too fast nor too slow.

The biological layer should be changed every day.

The biological layer must be kept wet.

 

 

Video Quiz 3

Check all correct statements about boiling and pasteurization.

1. Turbidity is a problem for pasteurization, but not for boiling.

2. Pasteurization gives adequate protection from pathogens in drinking water.

3. Recontamination is a problem for boiling and pasteurization.

4. Pasteurization gives an objective signal that disinfection temperature has been reached. 

 

UV-Radiation. How can the efficiency of the SODIS method be improved? Check all statements that are correct.

1. Reduce turbidity of water

2. Use unscratched bottles

3. Increase water temperature 

4. Use a new bottle for water storage

 

Chemical disinfection. Chlorine is the most widely used chemical disinfectant globally. Please select the pathogen against which chlorine is NOT effective?

1. Vibrio Cholera

2. Cryptosporidium

3. Hepatitis A virus

4. Rotavirus

 

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