Question

_______A_______ and ______B________ are the colloidal materials found in domestic sewage.

• A. A - Fecal matter, B - bacteria
• B. A - Ammonia, B - phosphate
• C. A - Sand, B - bacteria
• D. A - Fecal matter, B - Sand

Answer 1

The correct option is A A - Fecal matter, B - bacteria

The municipal wastewater generated in huge quantities in cities and towns is called sewage. Domestic sewage contains 0.1% of impurities and 99.9 % water.

The three types of impurities present in domestic sewage are as follows:

• Suspended solids: These remain suspended in the water. Sand, silt and clay are examples of suspended solids. Hence, option c and d are incorrect.
• Colloidal materials: These are microscopically dispersed insoluble particles in the size range of 0.001 to 1 micrometers. These include fecal matter, bacteria, cloth, paper fibres etc. Hence option a is correct.
• Dissolved materials are present in the dissolved state in the domestic sewage. It includes nutrients like nitrates, ammonia, phosphate, sodium etc. Hence, option b is incorrect.

Figure: Composition of wastewater