Process for reducing sludge accumulation in the hot water extraction process for oil sands

A method of reducing sludge accumulation in a tailings pond, having an inlet and an outlet, for a hot water extraction process plant which uses a recycling circuit of process water taken from the pond to extract bitumen from incoming oil sand, said oil sand containing ultrafines of less than 300 nm, and returns the process water containing ultrafines to the pond, comprising:

• treating the process water delivered to the pond by ensuring sufficient dispersent enters the process water circuit to disperse ultrafines and hinder formation of flocs which are precursors to forming sludge;
• delivering the treated process water to a beach at the pond's inlet where some ultrafines are removed from the recycling circuit, leaving a residual quantity, of ultrafines dispersed in the process water returned to the pond;
• withdrawing the process water and residual ultrafines from the pond's outlet for maintaining the volume of the process water in the pond sufficiently small so that the retention time of the process water and residual ultrafines is short enough that the ultrafines remain in a dispersed state and are prevented from forming flocs;
• and
• repeatedly withdrawing the process water and residual ultrafines from the pond's outlet and recycling them to the plant so that the ultrafines content increases to a steady state concentration where the quantity of ultrafine being trapped at the beach becomes substantially the same as the quantity of ultrafines being introduced with the incoming oil sand.