Sewage?

In almost all coastal towns that I've been to so far, first Bintan and now SB, there is always a little river runoff formation at the beach that comes from a manmade structure that resembles a drain or sewage of sorts. I sure hope those water are treated! I believe at Karnzow in Germany, we noticed similar discharges into the lake which made us blame the obnoxious smell in the area to the sewage!