Water Quality for Textile Processing Questions and Answers

Answer: C

Correct answer: raising the temperature of the bath

Heating makes hardness worse rather than better: temporary hardness precipitates as scale as the bicarbonate decomposes, which is exactly the deposit to be avoided. The other three are genuine remedies - sequestering holds the ions in solution, lime soda precipitates them, and ion exchange removes them onto a resin.

Answer: D

Correct answer: forming a soluble complex with the hardness ions

A sequestrant such as EDTA or a polyphosphate chelates calcium and magnesium into a stable soluble complex, so the ions remain in the water but are no longer available to react with soap, dye or the fibre. Nothing is removed and nothing precipitates, which is what distinguishes sequestering from the lime soda and ion exchange routes.

Answer: A

Both are true and the reason gives the hazard: the same affinity that makes the agent useful against hardness makes it a threat to any dye that depends on a coordinated metal ion. Overdosing is a real cause of shade variation.

Answer: B

Correct answer: filtration through a sand bed

A sand filter removes suspended solids, which are particles held in suspension; hardness is dissolved and passes straight through. The other three all address dissolved hardness - by precipitation, by exchange onto a resin, or by complexing it in solution. The distinction between suspended and dissolved is the whole point of the item.

Answer: C

A dyebath set at a particular pH will drift if the water carries substantial bicarbonate, and the buffer demand changes from batch to batch. It is measured separately from hardness for that reason. Buffering the bath is the usual remedy.

Answer: D

The first two are correct and are basic dyeing practice. The third is wrong, since the alkalinity of the supply changes how much acid or alkali is needed to reach the working pH. Both extremes demand control of the water supply.

Answer: A

One hundred times twenty gives two thousand cubic metres. Textile wet processing is among the more water intensive industries, which is why reuse and recovery receive so much attention. Consumption per tonne is a standard benchmark.

Answer: B

Everything dissolved in the feed stays behind as the water evaporates, so the concentration in the drum rises steadily. Blowdown and demineralisation are used to keep it within limits. Scale on a heated surface is dangerous as well as wasteful.

Answer: C

Both are true and the reason gives the necessity: the blowdown carries away both the concentrated solids and a good deal of heat, so its rate is a compromise between water quality and energy. Heat recovery from blowdown is often worthwhile.

Answer: D

Suspended matter must go before the softener or the resin bed fouls, and each stage protects the one that follows. Distribution is last because the treated water is what the process actually needs. Each stage protects the one after it.