Environmental Sanitation Questions and Answers

Answer: B

The paper's answer is 2, 3 and 4.

Rules on waste disposal in India are framed under the Environment (Protection) Act, 1986, the umbrella law under which the Bio-medical Waste (Management and Handling) Rules, 1998 and the municipal and other solid waste rules were notified. The Air (Prevention and Control of Pollution) Act, 1981 applies because burning and incineration of waste must meet emission standards set under it.

The Montreal Protocol is an international treaty of 1987 on substances that deplete the ozone layer. It does not govern solid waste disposal, so every option containing statement 1 is wrong.

Answer: B

Chlorination is most effective at about pH 7.

Chlorine in water forms hypochlorous acid (HOCl), the strongly germicidal form, and the hypochlorite ion (OCl^-), which is far weaker. Near neutral pH, around 7, most of the chlorine is present as hypochlorous acid; as the pH rises above about 8 it changes increasingly into hypochlorite and disinfection falls sharply.

pH 10 and 14 are alkaline, where hypochlorite dominates. pH 4 is far too acidic for drinking water. So of the options, pH 7 is the one at which chlorination works best.

Answer: C

The method is incineration.

Incineration is the controlled burning of refuse at high temperature. It reduces waste to ash and gases, destroys germs, and greatly cuts the volume of waste, which is why it is the hygienic method of choice for hospital and other infectious waste.

Burial and landfilling dispose of refuse by covering it with earth, without burning. Composting turns organic waste into manure by the action of microbes. None of these involves burning, which is the defining feature in the question.

Answer: B

Permanent hardness is removed by soda.

Permanent hardness is caused by calcium and magnesium sulphates and chlorides, which are not removed by boiling. Adding washing soda (sodium carbonate) converts them into insoluble calcium and magnesium carbonates, which settle out, leaving soft water.

Boiling removes only temporary hardness, which is due to bicarbonates. Chlorination kills germs but does not affect hardness, and filtration removes suspended particles, not dissolved salts.

Answer: B

The recommended level is 0.2 ppm to 0.5 ppm.

Residual free chlorine is the chlorine left in water after disinfection, which keeps protecting it on the way to the consumer. The Indian drinking water standard, IS 10500, sets a minimum of 0.2 mg/L (0.2 ppm) at the tap, and 0.5 mg/L where protection against viral infection is needed.

Below 0.2 ppm there is not enough reserve to deal with fresh contamination, which rules out the 0.1 ppm option. Ranges starting at 0.3 or 0.4 ppm do not match the standard's figures.