To test chemical oxygen demand (C.O.D.) of sewage, organic matter is oxidised by potassium dichromate in the presence of

A

1 and 2 only

B

1 and 3 only

C

2 and 3 only

D

1, 2 and 3

For the COD test of sewage, organic matter is oxidised by K₂Cr₂O₇ in the presence of

A

H₂SO₄

B

HNO₃

C

HCl

D

None of these

For the COD test of sewage, organic matter is oxidised by K₂Cr₂O₇ in the presence of

A

H₂SO₄

B

HNO₃

C

HCl

D

None of these

The correct relation between theoretical oxygen demand (TOD), Biochemical oxygen demand (BOD) and Chemical oxygen demand (COD) is given by

A

TOD > BOD > COD

B

TOD > COD > BOD

C

BOD > COD > TOD

D

COD > BOD > TOD

What is the COD (chemical oxygen demand) of ethanol, expressed as g COD/g ethanol?

A

1.30 g COD/g ethanol

B

32 g COD/g ethanol

Which of the following statements is correct regarding the oxidation number of Oxygen? I. The oxidation number of Oxygen in most compounds is -2. II. When Oxygen is bonded to Fluorine in compounds like Oxygen difluoride and Dioxygen diflouride, the Oxygen is assigned an oxidation number of +2 and +2 respectively. III. In peroxide, an Oxygen atom is assigned an oxidation number of -1 and in Superoxide, each oxygen atom is assigned an oxidation number of -1/2.

A

I only

B

II only

C

I and III only

D

I, II, and III

Which of the following statements is/are incorrect? 1. BOD (biochemical oxygen demand) of the effluent refers to the amount of carbon dioxide that would be consumed if all the organic matter in one litre of water were oxidised by bacteria. 2. The greater the BOD of wastewater, the more is its polluting potential. Select the correct answer using the code given below.

A

1 only

B

2 only

C

Both 1 and 2

D

Neither 1 nor 2

In sewage having fully oxidised organic matter, the nitrogen exists in the form of

A

Nitrites

B

Nitrates

C

Free ammonia

D

Aluminoid nitrogen

In a well aerated and agitated microbial culture, the 'supply' of oxygen is equal to 'demand' (uptake) of the growing culture. The K_La for such a system will be (K_La = volumetric mass transfer coefficient, C* = dissolved oxygen concentration in liquid in equilibrium with gaseous oxygen, C = instantaneous value of dissolved oxygen concentration, 'r' = specific oxygen uptake rate per unit weight of cells, X = dry weight of the cells per unit volume)

A

$$\frac{{\left( {rX} \right)}}{{\left( {C* - C} \right)}}$$

B

$$\frac{{\left( r \right)}}{{X\left( {C* - C} \right)}}$$

C

$$\frac{{\left( {C* - C} \right)}}{{\left( {rX} \right)}}$$

D

$$\frac{{\left( X \right)}}{{r\left( {C* - C} \right)}}$$

Biochemical oxygen demand or BOD is a test of the amount of oxygen needed for bacteria to break down the organic matter in a water sample over a period of

A

Five days

B

Ten days

C

Seven days

D

One day

To test chemical oxygen demand (C.O.D.) of sewage, organic matter is oxidised by potassium dichromate in the presence of

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