Patent ID: 7121532

Claim:
Apparatus for aeration of liquid comprising: a tank for receiving the liquid from a source having a tank bottom and tank sides for receiving and containing a quantity of the liquid during aeration; a liquid supply pipe for transporting the liquid from the source into the tank arranged to discharge the liquid adjacent the tank bottom; a discharge duct for removing liquid from a top of the tank to maintain a desired level of the liquid in the tank as more liquid is added from the source; an array of aeration pipes in the tank above the bottom and below the level of the liquid so that the aeration pipes are located in the liquid in the tank; each aeration pipe having an upper discharge surface with an array of air exit holes at spaced positions along its length and at spaced positions across its width; an air feed system including an air pump for feeding air into one end of each of the pipes for discharge of the air through the air exit holes into the liquid as bubbles of the air in the liquid; the array of aeration pipes being arranged such that each of the aeration pipes extends at least partly across the tank in a first direction of the tank; the array of aeration pipes being arranged such that the aeration pipes are arranged at spaced positions across the tank in a second direction of the tank transverse to the first direction; the array of aeration pipes being arranged such that the aeration pipes are arranged at different depths in the tank so as to define lower ones of the aeration pipes in the tank and upper ones of the aeration pipes in the tank at a death in the liquid higher than the lower ones of the aeration pipes; such that liquid flows between and over the aeration pipes in a path from the supply pipe to the discharge duct; and such that the air escapes from the aeration pipes of the array through the holes to inject air into the liquid in the tank at positions spaced in the tank both in the first and second directions and spaced vertically in the tank; and a plurality of collecting channels each located in the tank above a respective one of the lower ones of the aeration pipes; each of the collecting channels being arranged to collect bubbles rising from the respective one of the aeration pipes and being inclined so as to transport the bubbles as a stream of air to a location in the tank separated from the path of the liquid; at least some of the upper ones of the aeration pipes being located in the tank above respective ones of the collecting channels so as to discharge the air from the upper ones of the aeration pipes through the air exit holes as bubbles into the liquid from which the bubbles of the lower ones of the aeration pipes have been removed by the collecting channels.