Sewage Treatment Systems Quiz

What is the primary objective of the Preliminary Treatment System?

• To remove large floating matter

• To treat sludge

• To disinfect sewage

• To remove dissolved organic matter

Answer explanation

The primary objective of the Preliminary Treatment System is to remove large floating matter, such as debris and plastics, to protect downstream equipment and processes from damage and clogging.

What percentage of solids is typically found in domestic sewage?

• 0.1%

• 99.9%

• 30%

• 50%

Answer explanation

Domestic sewage typically contains about 0.1% solids, with the majority being water. This low percentage highlights the dilute nature of sewage, making 0.1% the correct answer.

Which treatment system is designed to remove colloidal and dissolved organic matter?

• Tertiary treatment

• Secondary treatment

• Primary treatment

• Preliminary treatment

Answer explanation

Secondary treatment is designed to remove colloidal and dissolved organic matter through biological processes, making it the correct choice. Primary treatment focuses on solids, while tertiary treatment targets remaining contaminants.

What is the main purpose of a grit chamber in sewage treatment?

• To remove scum

• To settle inorganic particles

• To remove large floating matter

• To disinfect the sewage

Answer explanation

The main purpose of a grit chamber is to settle inorganic particles, such as sand and gravel, from sewage. This process helps prevent damage to equipment and improves the efficiency of subsequent treatment stages.

What type of settling occurs in a plain sedimentation tank?

• Discrete settling

• Flocculent settling

• Compression settling

• Hindered settling

Answer explanation

In a plain sedimentation tank, discrete settling occurs as particles settle independently without interaction. This is typical for larger, denser particles, making 'discrete settling' the correct choice.

Which of the following is NOT a component of the Preliminary Treatment System?

• Screens

• Grit Chamber

• Biological reactor

• Skimming tank

Answer explanation

The biological reactor is not part of the Preliminary Treatment System, which typically includes screens, grit chambers, and skimming tanks to remove solids and debris from wastewater before further treatment.

What is the main function of a skimming tank?

• To remove scum

• To settle solids

• To aerate water

• To disinfect sewage

Answer explanation

The main function of a skimming tank is to remove scum, which consists of floating materials and oils. This process helps in maintaining water quality before further treatment.

What is the typical bacteria count in 1 liter of sewage?

• 5-50 million

• 100-200 million

• 5-50 billion

• 1-10 billion

Answer explanation

Sewage typically contains a high concentration of bacteria, often ranging from 5 to 50 billion per liter. This makes the correct answer 5-50 billion, reflecting the significant microbial load present in sewage.

Which treatment system is primarily focused on disinfection?

• Primary treatment

• Secondary treatment

• Tertiary treatment

• Preliminary treatment

Answer explanation

Tertiary treatment is primarily focused on disinfection, removing remaining contaminants and pathogens after primary and secondary treatments. This step ensures water is safe for discharge or reuse.

What is the main objective of the Secondary Treatment System?

• To remove dissolved organic matter

• To disinfect sewage

• To treat sludge

• To remove large solids

Answer explanation

The main objective of the Secondary Treatment System is to remove dissolved organic matter from sewage, which is essential for reducing pollution and improving water quality before further treatment.