Settling basins are designed to retain water long enough so that suspended solids can settle to obtain a high purity water in the outlet and to provide the opportunity for pH adjustment. Other processes that could be used: thickeners, clarifiers, hydro cyclones and membrane filtration are highly used techniques in the field. Compared to those processes, settling basins have a simpler and cheaper design, with fewer moving parts, demanding less maintenance, despite requiring cleaning and vacuuming of the quiescent zones at least once every two weeks.
However, settling basins can introduce new kinds of water contamination, particularly if the water supply is from a well. The basin can catch windblown contaminants, and if the water is retained for a long period, algae grows in the pool, leading to greater filtration problems. Settling ponds may also be ineffective at reducing turbidity caused by small particles with specific gravity low enough to be suspended by Brownian motion. Usually, it can only remove particles ranging from sand (2 mm in diameter) to silt (0.002 mm in diameter).