1. What is the primary purpose of a sewage treatment plant?
(A) To remove pollutants from wastewater
(B) To generate electricity
(C) To store water for irrigation
(D) To increase water hardness
2. Which of the following is a common method for primary treatment of sewage?
(A) Chlorination
(B) Filtration through sand
(C) Sedimentation in a settling tank
(D) Nitrification
3. The process of breaking down organic matter in sewage by microorganisms in the absence of oxygen is called:
(A) Aerobic digestion
(B) Coagulation
(C) Flocculation
(D) Anaerobic digestion
4. Which unit process in sewage treatment is mainly responsible for the removal of dissolved organic matter?
(A) Sedimentation
(B) Biological treatment
(C) Grit removal
(D) Screening
5. What is the function of a grit chamber in sewage treatment?
(A) Remove floating debris
(B) Reduce BOD
(C) Disinfect treated water
(D) Remove heavy inorganic solids like sand and gravel
6. In which treatment stage is sludge thickening usually carried out?
(A) Secondary treatment
(B) Quaternary treatment
(C) Primary treatment
(D) Tertiary treatment
7. Activated sludge process is an example of:
(A) Biological treatment
(B) Thermal treatment
(C) Physical treatment
(D) Chemical treatment
8. Which of the following is commonly used for disinfection of treated sewage?
(A) Aluminum sulfate
(B) Lime
(C) Chlorine
(D) Polyphosphate
9. The biological oxygen demand (BOD) of sewage indicates:
(A) The concentration of heavy metals
(B) The chemical content of solids
(C) The amount of suspended solids
(D) The amount of dissolved oxygen required by microorganisms to decompose organic matter
10. Tertiary treatment in sewage treatment is mainly aimed at:
(A) Removal of large solids
(B) Removal of nutrients and pathogens
(C) Sedimentation
(D) Biological decomposition of organics