...
At some point, the filter will become so clogged that the water level of the filter will begin to rise. Once the water level rises to a certain point, or the flow through the filter slows significantly, the filter has to be cleaned (how often this happens is usually plant and weather dependent). The plant operator will shut off the flow entering the filter and allow the remaining water to drain out. Next, the clear well valve is opened and the backwash water from the clear well will backwash the filter bed. This water fluidizes the sand particles in the filter, loosening the dirt particles caught in the sand and carries them into the backwash or sludge pipe. The backwash pipe will be at such an elevation so that the sand (which is larger and heavier than dirt particles) will remain in the sand filter. The clear well is designed so that as the last drop of water is flowing through the filter at the correct elevation to keep the sand particles elevated the target 30% for optimal cleaning. Once finished, the operator will close the backwash valve and begin filtration again or recharge the clear well. 
Figure 1: Clear Well Basic Concept
Method
1) Review of existing filtration/backwash technology and research
We conducted a literature and online review. We determined the flow rate needed to sufficiently expand and clean the sand filter bed. This will help us determine how high the clear well needs to be above the filter, how large the flow pipes should be, and how much water should be in the clear well.
Research of Existing Work.
...