Can home water be contaminated with city sewer water?

It's not supposed to...! But I will never discard any possibility. Household water is treated on designated utility plants to remove bacteria, most minerals, odor and contaminants. But nothing is perfect. Household water every one and then will have some odor. However if your brother has a concern the utility company supplier take samples in his property and test'em upon request. The the most pure drinking water is bottle water. Good luck...!