# Environmental Engineering Questions and Answers – Types of Sewage Filter

This set of Environmental Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Types of Sewage Filter”.

1. The intermittent sand filters have better BOD removal efficiency than trickling filters.
a) True
b) False

Explanation: The trickling filters have the best BOD removal efficiency in comparison to the types of filters used in aerobic treatment with a maximum value of 95%.

2. The filter material used in contact bed is ___________
a) Sand
b) Stone ballast
c) Gravel
d) Fine sand

Explanation: The filter material used in the contact bed is broken stones called as stone ballast.

3. Which of the following is called as contact bed?
a) Primary clarifier
b) Secondary clarifier
c) Contact filter
d) High rate digester

Explanation: Contact filters are water tight tanks that are used for the aerobic treatment of sewage. They are also called as contact bed.

4. How many types of trickling filters are used in sewage treatment?
a) 6
b) 5
c) 3
d) 2

Explanation: The trickling filters are divided into conventional and high rate trickling filters.

5. The depth of the filter media of intermittent filter is ___________
a) 45cm
b) 60cm
c) 20cm
d) 25cm

Explanation: The minimum depth of filter media of intermittent filter is 60cm. These filters give highly nitrified effluent.

6. Which of the following filter is used in the anaerobic treatment of sewage?
a) Intermittent sand
b) Trickling filter
c) Contact filter
d) Biological filter

Explanation: Biological filter is used in anaerobic treatment, whereas intermittent sand filter, trickling filter and contact filter are used in the aerobic treatment of sewage.

7. The maximum size of filter media of a percolating filter is ___________
a) 10mm
b) 25mm
c) 60mm
d) 75mm

Explanation: The minimum and maximum size of filter media of a percolating filter is 25mm and 75mm respectively.

8. The recirculation ratio for the low rate trickling filter is ___________
a) 1
b) 2
c) 3
d) 0

Explanation: The recirculation system is not provided in the low rate trickling filter. So, when the recirculation is 0, the type of filter used is a low rate trickling filter.

Sanfoundry Global Education & Learning Series – Environmental Engineering.