Patent ID: 8226828

Claim:
A method of treatment of wastewater, comprising performing in a submerged aerated filter system differing specific forms of treatment at respective stages, with sparging of gas at those stages, said differing specific forms of treatment being biological main treatment, effluent solids removal and one of substantially solely de-nitrification and a combination of de-nitrification and effluent solids removal, utilising respective beds of buoyant media particles, said main treatment comprising using its bed of media particles for support of biofilm with said sparging of gas at said main treatment stage being normally of a gas comprised of oxygen and at a lower rate of flow for aeration of the wastewater at said main treatment stage, but intermittently at a higher rate of flow to disrupt and thereby clean said bed at said main treatment stage, said solids removal comprising using its bed of media particles to filter-out the solids from the liquid with substantially no sparging at the solids removal stage, said sparging of gas being performed intermittently at said solids removal stage to disrupt and thereby clean said bed, said substantially solely de-nitrification, if performed, comprising using its bed of media particles for support of biofilm with substantially no sparging with oxygen-containing gas at the substantially solely de-nitrification stage, sparging of gas being performed intermittently at said substantially solely de-nitrification stage to disrupt and thereby clean said bed at said substantially solely de-nitrification stage, and said combination, if performed, comprising using its bed of media particles for support of biofilm with substantially no asparging with oxygen-containing of the combined de-nitrification and effluent solids removal stage, sparging of gas being performed intermittently at that combined stage to disrupt and thereby clean said bed at said combined stage.