1) Water purifying capsules. The capsules are able to deactivate bacteria, viruses and parasites to make the water safe to drink but it cannot remove impurities in the water.
Boiling of water. Boiling water can remove most bacteria and viruses but it cannot remove impurities in the water. It is the cheapest method out of the three but it is time consuming.
Life Straw. The straw is able to filter most impurities, parasites and bacteria but it does not remove viruses and salt. It is more expensive than water purifying capsules but it is able to purify a larger volume of water.
All these methods are only a small part of the method to purify municipal water supplies. Sedimentation, Filtration, Disinfection, Water Fluoridation, Coagulation and Flocculation are the steps required to purify municipal water supplies.
2) This is because a lot of energy is required for the machines to perform desalination. Thus it is very expensive and not sustainable for the environment.
3a) The likely major source of the lead in the drinking water could be from the lead water pipe as it may corrode over time which will cause the water to be contaminated with lead.
3b) Yes. This is because some of the chemicals may not be properly disposed of and thus the chemicals may cause the lead water pipe to corrode thus contaminating the water supply.
4) Fat is non polar and water is polar. Polar compounds dissolve in polar solvents and non polar compounds dissolve in non polar solvents, hence only the water-soluble vitamins would be expected to be polar molecules.