Starting with septic tanks, owners have to continually maintain the system. Just like this, our sewer systems must continually be maintained, and many aren't.
For the 80% of us using community water, our waste is taken to a treatment facility where it is treated, the water is cleaned, the standards are met, and eventually, the water is let out into a nearby water system.
What happens when the facility fails to clean the excrements correctly? Well, check the news. This happens quite often. Many treatment facilities are not up to code, and many release contaminated water in our waterways. This effects fishing, community health, tourism, farming, and so much more that goes unseen until it is too late and your town has a major problem on its hands.
Need another common problem? Well, many states have connections for both sewer and stormwater drains. When there is flooding, very often there is overflow in the system carrying the sewage sludge, and this overflows into bodies of water.
To add on to this, since the infrastructure is so old, the pipes are usually too narrow to carry today's population load along with stormwater overflow. This leads to more leaks in the pipes, which can lead to more water and land pollution as the sludge contaminates the area of the leak.
If these problems are not faced as soon as possible, our tap water and farm products will face the consequences, and then we will face them. One of the best funders to start with for sewer issues, for those in South Carolina, is the Rural Infrastructure Authority.