The primary treatment of sewage involves:

1. Digestion

2. Decomposition

3. Sedimentation and filtration

4. None of these

The amount of oxygen required by the microbes in the decomposition of organic matter is called:

1. Chemical oxygen demand

2. Biochemical oxygen demand

3. Total oxygen demand

4. Dissolve oxygen

The mixture of gases released during anaerobic digestion of sludge is called:

1. Methane

2. Carbon dioxide

3. Biogas

4. Flammable gases

Biogas contains:

1.CO₂

2. H₂S

3. CH₄

4. All of these

The symbiotic association between fungi and roots of higher plants is called:

1. Lichen

2. Mycorrhiza

3. Biofertilizer

4. BOD

The organisms which are used to enrich the nutrient quality of the soil are called:

1. Mycorrhiza

2. Biofertilizers

3. Yeast

4. Methanogens

Which of the following serve as biofertilizer in paddy fields?

1. Bacteria

2. Yeast

3. Cyanobacteria (blue-green algae)

4. Fungi

The solids which settle after primary treatment of sewage are called:

1. Primary sludge

2. Activated sludge

3. Flocs

4. Total solids

Given below are three statements (A-B) each with one or more blanks. Select the option which correctly fills the blanks in the statements Statements:

1. A - Antibiotic, Trichoderma polysporum; B - filtration and sedimentation

2. A - Cyclosporin A, Trichoderma polysporum; B - filtration and sedimentation

3. A - Cyclosporin A, Trichoderma polysporum; B - Centrifugation and sedimentation

4. A - Antibiotic, Trichoderma polysporum; B - Centrifugation and sedimentation

Given below are three statements (A-B) each with one or more blanks. Select the option which correctly fill the blanks in the statements Statements:

A. Microbes consume the major part of the organic matter in the effluent and reduce _________ of sewage.

B. Certain bacteria which grow anaerobically on cellulosic material, produce large amount of methane along with CO₂ and H₂. The bacteria are commonly called as _________ and one such common bacterium is _________. Options:

1. A - CO₂ demand; B - methanogens, Methanobacterium

2. A - Carbon; B - methanogens, Methanobacterium

3. A - biochemical oxygen demand; B - methanogens, Methanobacterium

4. A - biochemical oxygen demand; B - Methylokorus infemorum