A
settling basin,
settling pond or
decant pond is an earthen or concrete structure using
sedimentation to remove
settleable matter and
turbidity from
wastewater. The basins are used to control
water pollution in diverse industries such as
agriculture,
aquaculture, and
mining. Turbidity is an optical property of water caused by scattering of light by material suspended in that water. Although turbidity often varies directly with weight or volumetric measurements of settleable matter, correlation is complicated by variations in size, shape,
refractive index, and
specific gravity of suspended matter. Settling ponds may be ineffective at reducing turbidity caused by small particles with specific gravity low enough to be suspended by
Brownian motion.