Short answers, pulled from the story.
The first sanitary sewer system to be built in the United States was constructed in Lowell, Massachusetts, on the 1st of July 1854. This system marked a significant shift from earlier methods where cities relied on gutters and open refuse accumulation.
A conventional gravity sewer relies on the force of gravity to move wastewater from buildings to treatment facilities. Pipes are laid at specific gradients to maintain flow velocities that generate enough turbulence to prevent solids from settling and causing blockages.
Force mains and lift stations pump sewage to higher elevations or across long distances to treatment plants where gravity flow is insufficient. These systems are essential for serving areas at lower elevations than the sewage treatment plant or for distant areas at similar elevations.
Simplified sanitary sewers consist of small-diameter pipes laid at fairly flat gradients which can reduce investment costs to about half the price of conventional sewers. However, the trade-off is that the requirements for operation and maintenance are usually higher as the smaller pipes are more prone to blockages.
Sanitary sewer overflows occur when blocked or broken sewer lines allow untreated sewage to escape into the environment before reaching treatment facilities. Prevention requires comprehensive construction inspection programs to avoid inappropriate connections of cellar, yard, and roof drains to sanitary sewers.
The mid-1950s marked a turning point in the maintenance of sanitary sewers with the invention of a unit that could coat the inside of a pipe with a special cement mixture. This method sealed all cracks and breaks without the need for expensive excavation.