Within the septic tank, gravity causes the solids to sink to the bottom of the tank, and the oils/grease and scum float on the surface of the liquid in the tank.
(the oils/grease and scum; float; L:on the surface of the liquid in the tank) (gravity; causes; the solids to sink to the bottom of the tank; T:Within the septic tank) Context(gravity causes,List([24, 38))):(the solids; to sink; to the bottom of the tank)
gravity causes,List([24, 38))
the oils/grease and scum gravity the solids
float causes to sink
L:on the surface of the liquid in the tank
the solids to sink to the bottom of the tank T:Within the septic tank
to the bottom of the tank