A city is to install rapid sand filters downstream of the clarifiers. The design loading rate is selected to be 160 m3/ (m2.d). The design capacity of the water works is 0.35 m3/s. The maximum surface per filter is limited to 50 m2. Design the number and size of filters.

A city is to install rapid sand filters downstream of the clarifiers. The design loading rate is selected to be 160 m3/ (m2.d). The design capacity of the water works is 0.35 m3/s. The maximum surface per filter is limited to 50 m2 and find out the normal filtration rate?

A

154.3 m3/(m2.d)

B

154.6 m3/(m2.d)

Which of the following statements are correct pertaining to the value of uniformity coefficient Cu for filter sand? (1) For slow sand filters, Cu = 1.8 to 2.5 (2) For rapid sand filters, Cu = 1.3 to 1.7 (3) For slow sand filters, Cu = 1.3 to 1.7 (4) For rapid sand filters, Cu = 1.8 to 2.5

A

2 and 3

B

1 and 4

C

3 and 4

D

1 and 2

Consider the following statements in respect of slow sand filter and rapid sand filter: 1. The two filters differ in respect of the standards regarding the non-uniformity of the sand used in their filtering media. 2. The two filters do not differ in respect of the effective size of the sand used in them. 3. The two filters differ in respect of their respective under-drainage system. 4. The two filters differ in respect of their respective rate of filtration. Which of the above statements are correct?

A

1, 2 and 3

B

1, 2 and 4

C

2, 3 and 4

D

1, 3 and 4

Assertion A: Slow sand filters are more efficient in removal of bacteria than rapid sand filters.
Reason R: The sand used in slow sand filters is finer than that in rapid sand filters
Select your answer based on the coding system given below:

A

Both A and R is true and R is the correct explanation of A

B

Both A and R is true but R is not the correct explanation of A

C

A is true but R is false

D

A is false but R is true

Three companies L, M, and N participated in campus recruitment in college Z. All three companies selected an equal number of candidates. Out of the total candidates selected, 60 were selected by both L and M. The number of candidates selected by both M and N was 68 less than twice the number of candidates selected by both L and M. There were 28 candidates who got selected by each L, M and N companies. This number was 50% less than the number of candidates selected by both L and N. The total number of candidates selected by both L and N was 92% less than a total number of candidates selected. The total number of students that got placed in exactly one company was what percent more than the ones that got placed in exactly two companies?

A

200%.

B

600%.

C

400%.

D

800%.

Cleaning is done by
(i) Scraping and removal in filters slow sand
(ii) Back washing in slow sand filters
(iii) Scraping and removal in filters rapid sand
(iv) Back washing in rapid sand filters
The correct answer is

A

(i) and (ii)

B

(ii) and (iii)

C

(i) and (iv)

D

(ii) and (iv)

Assertion A: Slow sand filters are more efficient in removal of bacteria than rapid sand filters.Reason R: The sand used in slow sand filters is finer than that in rapid sand filtersSelect your answer based on the coding system given below:

A

Both A and R is true and R is the correct explanation of A

B

Both A and R is true but R is not the correct explanation of A

C

A is true but R is false

D

A is false but R is true

Cleaning is done by (i) Scraping and removal in filters slow sand (ii) Back washing in slow sand filters (iii) Scraping and removal in filters rapid sand (iv) Back washing in rapid sand filtersThe correct answer is

A

(i) and (ii)

B

(ii) and (iii)

C

(i) and (iv)

D

(ii) and (iv)

The following are certain operating problems of a rapid sand filter: 1. Sand depth should never be depleted by more than 10 cm. 2. Air binding results due to development of negative head and formation of air bubbles in the filter sand. 3. Water softening with lime-soda leads to incrustation of sand. 4. Bumping of filter bed is caused due to negative head. Which of the above statements are correct?

A

1, 2 and 4 only

B

1, 2 and 3 only

C

3 and 4 only

D

1, 2, 3 and 4

A water treatment plant of capacity, 1 m3/s has filter boxes of dimensions 6 m × 10 m. The loading rate to the filters is 120 m3/day/m2. When two of the filters are out of service for back washing, the loading rate (in m3/day/m2) is

A

144

B

122

C

133

D

124

A city is to install rapid sand filters downstream of the clarifiers. The design loading rate is selected to be 160 m3/ (m2.d). The design capacity of the water works is 0.35 m3/s. The maximum surface per filter is limited to 50 m2. Design the number and size of filters.

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