Waste Generation and Characterisation Questions and Answers

Answer: A

The estimated per capita solid waste generation in small towns is about 0.1 kg per day.

Indian estimates show that per capita municipal solid waste rises with town size and income: about 0.1 kg per person per day in small towns, rising to about 0.5 kg in the largest cities.

The higher figures of 0.3 to 0.6 kg belong to larger towns and cities, not to small towns.

Answer: C

The moisture content is 20.35%.

Moisture content of solid waste is normally reported on a wet-weight basis: the water lost on drying as a percentage of the original wet weight.

\[ \begin{aligned} M &= \frac{w - d}{w} \times 100 \\ &= \frac{102.2 - 81.4}{102.2} \times 100 \\ &= \frac{20.8}{102.2} \times 100 \approx 20.35\% \end{aligned} \]

Dividing by the dry weight instead (the dry-basis formula) gives \(20.8/81.4 \approx 25.6\%\), close to the 25.22% option. 10.15% and 5.1% are roughly half and a quarter of the right value.

Answer: A

The least ash is found in textiles, the keyed option.

In a proximate analysis of municipal solid waste, the inorganic residue left after burning is small for natural and synthetic fabrics. Plastic, leather and rubber contain fillers, pigments and mineral additives (carbon black, chromium salts and other compounds), which leave a larger ash residue. Textiles are therefore the component with the lowest percentage.

Answer: D

The keyed answer is that an important source of arsenic in municipal solid waste is household pesticides.

Many older pesticides, wood preservatives and rat poisons contained arsenic compounds, and discarded household products of this kind put arsenic into the waste stream. Rubber products and batteries are known mainly for other metals (zinc and lead, cadmium and mercury), and pigments in plastics are associated with cadmium and lead, so they are the less usual sources for arsenic.