Abstract: A process for treating retention pond sludge containing greater than 20% solids including minerals and bitumen and associated with the aqueous extraction of bitumen from tar sands to provide water substantially reduced in solids content which comprises agitating the sludge with water to provide a diluted sludge with a solids concentration in the range of 6 to 18% by weight, and thereafter settling the sludge to form a lower layer having a solids content substantially higher than that of the sludge an upper layer of bituminous froth, and a middle layer of water having a substantially lower solids content than said undiluted sludge and recovering said upper layer.

Abstract: A method for reducing the sludge content of a retention pond associated with the hot water process for extracting bitumen from tar sands which comprises admixing a sludge stream containing at least 12% solids by weight with a hot water extraction process waste water stream containing at least 20% sand; settling the mixture in a settling zone to form an upper layer substantially reduced in mineral matter and a lower layer comprised of a sand-sludge mixture and dispersing said lower layer over a sand pile zone to provide additional sand layers thereon containing at least a part of the sludge in the interstices of said additional sand layers.