Water Quality for Textile Processing Questions and Answers

Answer: A

Correct answer: True

Suspended solids foul the resin bed: they coat the beads, reducing the surface available for exchange, and they block the flow so that the bed channels and its capacity falls. Regeneration does not remove them. A sand or multimedia filter ahead of the softener is therefore standard, and it is far cheaper than replacing a fouled resin charge.

Answer: B

It gives a permeate low in total dissolved solids and a concentrated reject that must be disposed of. The reject is a significant fraction of the feed and is itself an effluent problem. Recovery of the reject is an active area of work.

Answer: C

The first two are correct. The third is generally false, since reactive dyeing discharges strongly alkaline liquor and neutralisation is a routine part of the effluent plant. Colour is the hardest of the three to remove.

Answer: D

Correct answer: counter-current rinsing of the fabric

In counter-current rinsing the fresh water enters at the last stage and flows backwards against the fabric, so the dirtiest water meets the dirtiest cloth and the cleanest meets the cleanest. The same rinsing is achieved with a fraction of the water, and it needs no treatment plant - only the plumbing. Recycling an exhausted dyebath or mixed effluent requires treatment and careful control of what is carried over.

Answer: A

Correct answer: True

Hardness, iron, alkalinity and dissolved solids all affect how a dye behaves - the exhaustion, the shade and the fastness - so the same recipe in different water gives a different result. That is why a mill measures its water and treats it to a specification rather than accepting whatever the supply delivers, and why a change of borehole or season can shift shades unaccountably.

Answer: B

Correct answer: Both A and R are true, and R is the correct explanation of A

Both are true and the reason gives the causal link. Right first time dyeing means matching the standard without additions, and that requires every input to be the same each time. Water is the largest input by mass, so uncontrolled variation in it defeats the aim however carefully the dyes and chemicals are weighed - which is why water treatment is a prerequisite for the practice rather than an optional refinement.

Answer: C

Correct answer: 97.5 per cent

\[ \frac{200-5}{200} = \frac{195}{200} = 0.975 = 97.5\%. \] The base is the hardness entering, so the removal is 97.5 per cent. The 2.5 per cent offered is the fraction *remaining*, which is the same calculation read the wrong way round, and 5 mg/L is a normal softener outlet figure for textile use.