Abstract: Pure oxygen or a gas containing substantially more oxygen than air is injected under pressure into sewage held in or flowing through a rising or pumping sewer. This injection may be used to prevent the concentration of dissolved oxygen in the sewer falling to a level at which there occurs bacterial reduction to hydrogen sulphide of sulphate present in the sewage and/or to reduce the Biochemical Oxygen Demand of the sewage. The injection can also be used to oxidize to sulphur any sulphide dissolved in the sewage.The pure oxygen or the gas containing more oxygen than air may be injected into sewage flowing through a sewage pipe forming part of a rising or pumping sewer, into a pump used to transfer the sewage through the sewer, or into a part of the sewer (e.g. a sump) where sewage is collected before being transferred through the sewer.

Abstract: The invention provides a method of, and apparatus for, treating sewage flowing through a sewer, wherein an oxygenating gas is introduced under pressure into the sewage and is dissolved therein and the thus oxygenated sewage is contact with a matrix of solid material carrying micro-organisms effective to reduce the Biochemical Oxygen Demand of the sewage, the matrix extending across a region inside the sewer. The treatment may be performed in a gravity sewer or in a rising or pumping sewer.

Abstract: An oxygenation system for promoting the activity of microorganisms supported on a filter bed, by introducing an oxygenated liquid stream into contact with the microorganisms.