Why Is Dirt in our Wastewater and What Do We Do with It?
Sand will break the machinery throughout the plant if we don't clean it out. But why is sand in the wastewater? It is NOT because you are so dirty when you take a shower or bath. It is because dirt or sand can get into the wastewater stream if there are any cracks in the collection pipes.
We slow the wastewater stream down just enough so that the heaviest (most dense) materials fall out of the water. Wastewater flows at about 1 ft per second through the grit removal system. Because sand and dirt are the most dense, so they fall out at that speed, but most organics do not.