Question 1 |

A wastewater sample contains two nitrogen species, namely ammonia and nitrate. Consider the atomic weight of N, H, and O as 14 g/mol, 1 g/mol, and 16 g/mol, respectively. In this wastewater, the concentration of ammonia is 34 mg NH_3/liter and that of nitrate is 6.2 mg NO_3^{-}/liter. The total nitrogenconcentration in this wastewater is _______ milligram nitrogen per liter. (round off to one decimal place)

29.4 | |

12.8 | |

36.2 | |

16.4 |

Question 1 Explanation:

Total nitrogen concentration (mg/liter)in this
wastewater =\left ( \frac{34}{17}+\frac{6.2}{62} \right ) \times 14=29.4 mg/l as Nitrogen.

Question 2 |

The total hardness in raw water is 500 milligram per liter as CaCO_3. The total
hardness of this raw water, expressed in milligram equivalent per liter, is

(Consider the atomic weights of Ca, C, and O as 40 g/mol, 12 g/mol, and 16 g/mol, respectively.)

(Consider the atomic weights of Ca, C, and O as 40 g/mol, 12 g/mol, and 16 g/mol, respectively.)

10 | |

100 | |

1 | |

5 |

Question 2 Explanation:

TH=500\frac{mg}{L} \text{ as }CaCO_3=\frac{500}{(100/2)}\frac{meq}{L}=10meq/L

Question 3 |

Ammonia nitrogen is present in a given wastewater sample as the ammonium ion \left(N H_{4}^{+}\right) and ammonia \left(N H_{3}\right). If pH is the only deciding factor for the proportion of these two constituents, which of the following is a correct statement?

At pH above 9.25, only \left(N H_{4}^{+}\right) will be present | |

At pH above 9.25, \left(N H_{3}\right) will be predominant | |

At pH 7.0, \left(N H_{4}^{+}\right) and \left(N H_{3}\right) will be found in equal measures | |

At pH 7.0, \left(N H_{4}^{+}\right) will be predominant |

Question 3 Explanation:

From the above curve, it is evident that at pH 7.0, \mathrm{NH}_{4}^{+} will be predominant.

Question 4 |

A 50 mL sample of industrial wastewater is taken into a silica crucible. The empty weight of the crucible is 54.352 g. The crucible with the sample is dried in a hot air oven at 104 ^{\circ}C till a constant weight of 55.129 g. Thereafter, the crucible with the dried sample is fired at 600 ^{\circ}C for 1 h in a muffle furnace, and the weight of the crucible along with residue is determined as 54.783 g. The concentration of total volatile solids is

15540 mg/L | |

8620 mg/L | |

6920 mg/L | |

1700 mg/L |

Question 4 Explanation:

\begin{aligned} V&= 50 \; ml\\ W_1&=54.352\; gm \\ W_2&=55.129 \; gm \\ W_3&=54.783 \; gm \\ &\text{Total volatile solids,} \\ &=\frac{W_2-W_3}{V} \\ &= \frac{(55.129-54.783)}{50} \times 10^6 \; mg/lit\\ &=6920\; mg/l \end{aligned}

Question 5 |

A completely mixed dilute suspension of sand particles having diameters 0.25, 0.35, 0.40, 0.45 and 0.50 mm are filled in a transparent glass column of diameter 10 cm and height 2.50 m. The suspension is allowed to settle without any disturbance. It is observed that all particles of diameter 0.35 mm settle to the bottom of the column in 30 s. For the same period of 30 s, the percentage removal (round off to integer value) of particles of diameters 0.45 and 0.50 mm from the suspension is ____

50 | |

75 | |

90 | |

100 |

Question 5 Explanation:

Since sand particle of size 0.35 mm settles to the bottom of the column in 30 sec
particles having size greater than 0.35 mm i.e. 0.45 and 0.50 mm will also settle in
suspension at the bottom of column by 100% in 30 sec, infact these bigger sized particle
will settle by 100% in less than 30 sec. So answer is 100%.

There are 5 questions to complete.