Environmental Studies · Chemistry

Water and Wastewater Treatment

1,423 Questions

This topic deals with water purification, wastewater treatment methods, and industrial effluent management. It includes questions on filtration, disinfection, and water hardness removal. These concepts are tested in environmental science and engineering exams.

Water purificationWastewater treatmentBioremediation strategiesWater hardness removalIndustrial effluent management

Water and Wastewater Treatment Questions

Multiple choice

An analysis for determination of solids in the return sludge of activated sludge process was done as follows: (1) A crucible was dried to a constant mass of 62.485 g. (2) 75 ml of a well mixed sample was taken in the crucible. (3) The crucible with the sample was dried to a constant mass of 65.020 g in a drying oven at 104o C. The crucible with the dried sample was placed in a muffle furnace at 600o C for an hour. After cooling, the mass of the crucible with residues was 63:145 g.

The concentration of organic fraction of solids present in the return sludge sample is

  1. 8800 mg/l

  2. 25000 mg/l

  3. 33800 mg/l

  4. 42600 mg/l
Reveal answer Fill a bubble to check yourself
C Correct answer
Multiple choice

The results of analysis of a raw water sample are given below:

 
Turbidity 5 mg/l
pH 7.4
Fluorides 2.5 mg/l
Total Hardness 300 mg/l
Iron 3.0 mg/l
MPN 50 per 100 ml

From the data given above, it can be inferred that water needs removal of

  1. turbidity followed by disinfection

  2. fluorides and hardness

  3. iron, followed by disinfection

  4. both (2) and (3)
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

 Fluoride should be less than 1.5 mg/L, hardness between 75 - 115 mg/L as $CaCO_3$ iron 0.3 mg/L and MPN 1 per 100 mL (presence of pathogenic bacteria). Hence, water needs removal of fluoride, hardness iron and followed by disinfection to reduce MPN to 1 per 100 mL.

Multiple choice

Match the following:

Group I (Type of water impurity) Group II (Method of treatment)
P. Hardness 1. Reverse Osmosis
Q. Brackish water from sea 2. Chlorination
R. Residual MPN from filters 3. Zeolite Treatment
S. Turbidity 4. Coagulation and Flocculation
5. Coagulation, Flocculation and Filtration

  1. P - 1, Q - 2, R - 4, S - 2

  2. P - 3, Q - 2, R - 2, S - 4

  3. P - 2, Q - 1, R - 3, S - 5

  4. P - 3, Q - 1, R - 2, S - 5
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Hardness is treated by Zeolite (3), Brackish water by Reverse Osmosis (1), Residual MPN by Chlorination (2), and Turbidity by Coagulation, Flocculation, and Filtration (5). This matches option D.

Multiple choice

A conventional Activated Sludge Plant treating 1000 m3/d of municipal waste water disposes of its anaerobically digested sludge on relatively impervious farmland. Use the following data:

1. Raw Sewage SS = 225 mg/I (70% volatile)

BOD = 190 mg/I (Excess activated sludge returned to primary) | | 2. Primary Setting| SS-50% removal BOD-30% removal| | 3. Excess Activated Sludge applied (80% Volatile of total)| 0.4 g VSS produced per g BOD| | 4. Anaerobic Digester| VSS reduced 50% Digested Sludge Concentration – 60% Sludge Specific Gravity-1| | 5. Application on farmland| 2 m3 /ha.d|

Total volatile suspended solids to be anaerobically digested (kg/d, VSS) shall be

  1. 133

  2. 168

  3. 233

  4. 245
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Total VSS is the sum of VSS from primary sludge and excess activated sludge. Primary sludge VSS is calculated from SS removal and volatile fraction. Excess activated sludge is 0.4 * BOD removed. Summing these gives 133 kg/d.

Multiple choice

Zero hardness of water is achieved by

  1. lime soda process

  2. excess lime treatment

  3. iron exchange treatment

  4. excess alum and lime treatment
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Zero hardness, other than ion exchange or base exchange or zeolite method, leaves behind a substantial amount of hardness or alkalinity. Only by means of zeolite process can zero hardness of water be achieved.

Multiple choice

The aquariums are disinfected by

  1. potassium peroxymonosulphate

  2. potassium permanganate

  3. peracetic acid

  4. ozone
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

It is utilised to disinfect aquariums and is also mainly employed in it. It is used to disinfect aquariums and is also widely used in public swimming pools to disinfect people's feet before using the pool.

Multiple choice

What is the reason for using alum for purifying the water?

  1. It forms complex with clay particles.

  2. It coagulates the mud particles.

  3. It exchanges Ca2+ and Mg2+ ions present in hard water.

  4. Its sulphate ion is a water purifier.

  5. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Mud is colloidal charged solution which on treatment with Alum (Al3+) gets neutralised or coagulated.

Multiple choice

What does the WD in WD-40 stand for?

  1. Wisconsin Distillery

  2. Water Disposal

  3. Waste Dispenser

  4. Water Displacer
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

WD-40 stands for Water Displacement, 40th formula, as it was designed to prevent corrosion by displacing water.

Multiple choice chemistry water too little to waste effects and conservation of water pollution water pollution, its effects and cures for a pollution free nature

Distilled water is clean and pure water, but unfit for human consumption.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Drinking distilled water robs your body of its natural source for many minerals essential to good health. This results in a mineral loss in the body with increase your risk for osteoporosis, hypertension, osteoarthritis etc.

Multiple choice chemistry substances in common use common salt some useful compounds in everyday life salts and their properties study of some important salts salts used in daily life

The uses of bleaching powder are:

  1. it is used for bleaching cotton

  2. it is used as an oxidizing agent in chemical industries

  3. it can be used for disinfecting water

  4. all of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Bleaching powder $(CaOCl _2)$ has many uses and some of them are as follows :-

1.It is used in bleaching dirty clothes in launder, as a bleaching agent in cotton and linen in the textile industry.
2.Due to evolution of nascent oxygen, it is used as an oxidizing agent in the chemical industries.
3.It can be used as a disinfectant which can be used for disinfecting water to make it potable.
Hence, the correct answer is option (D).

Multiple choice zoology weather, climate and adaptation of animals to different climates terrestrial adaptation in animals terrestrial adaptations animal adaptations terrestrial adaptations in plants adaptation in terrestrial plants

Floating materials in preliminary treatment includes:

  1. Chemicals

  2. Gases

  3. Liquids

  4. Dead animals
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Preliminary treatment in wastewater management involves removing large solids, including debris and dead animals, to protect downstream equipment.