Ring channel aeration apparatus and method

In a ring channel aerator comprising inner and outer wall means for circulating wastewater along a horizontal flow path, the improvement which comprises:

• means for causing the major portion of the work expended in the aeration of the wastewater to be performed separately from the work of circulating said wastewater, said means including:
• hydraulic jump means located in said channel and extending between said inner and outer wall means generally transversely of said flow path, said hydraulic jump means including means for establishing upward flow in said jump, for positively urging said flow in a forward direction as it departs said jump, for discharging said forward flowing wastewater from said jump as a stream which includes the upper surface of the wastewater downstream of the jump, for directing said stream into a zone of abruptly increased cross-section immediately downstream of the jump and for inducing thereby a forward roll in the wastewater, said hydraulic jump means comprising a substantially upright chimney member having an upstream inlet in the lower half of the channel depth and a downstream outlet in the upper half of the channel depth, said hydraulic jump means having the property that it is capable of imparting and maintaining horizontal circulation of wastewater within said ring channel aerator with an energy expenditure of about 0.35 times the total energy input to the ring channel aerator or less, said hydraulic jump means occupying a minor portion of the length of said flow path;
• and
• horizontally non-propulsive bubble release means positioned along the remainder of said flow path for bubbling oxidative process gas into the waterwater and having an oxygen transfer efficiency of at least about 6.

In a ring channel aerator comprising inner and outer wall means for circulating wastewater along a horizontal flow path, the improvement which comprises:

• means for causing the major portion of the work expended in the aeration of the wastewater to be performed separately from the work of circulating said wastewater, said means including:
• hydraulic jump means located in said channel for inducing an upward and forward rolling motion in the wastewater as it passes through and out of said jump, said hydraulic jump means having the property that it is capable of imparting and maintaining horizontal circulation of wastewater within said ring channel aerator with an energy expenditure of about 0.35 times the total energy input to the ring channel aerator or less, said hydraulic jump means occupying a minor portion of the length of said flow path and comprising:
• an upstream upper water barrier and a downstream lower water barrier, said barriers extending between said inner and outer walls and generally transversely of said flow path;
• an upstream inlet and downstream outlet positioned respectively below and above said upstream and downstream water barriers;
• gas discharge means distributed laterally between said inner and outer walls in the space between said upstream and downstream barriers, said gas discharge means being positioned for releasing and distributing its discharge of gas across more than half of the horizontal distance between said upstream barrier and said downstream barrier;
• and
• horizontally non-propulsive bubble release means positioned along the remainder of said flow path for bubbling oxidative process gas into the wastewater and having an oxygen transfer efficiency of at least about 6.

A method of aerating wastewater undergoing circulation in a ring channel along a horizontal flow path, comprising:

• inducing said horizontal circulation by causing upward and forward motion of the wastewater as it passes through and exits at least one propulsion zone, said zone or zones being located in and extending transversely of said flow path, and occupying a minor portion of the length of said flow path, said zone or zones comprising a substantially upright chimney member(s) having an upstream inlet and a downstream outlet at a relatively higher elevation than said inlet;
• bubbling oxidative process gas into the wastewater along said flow path outside said propulsion zone(s) through horizontally non-propulsive bubble release means having an oxygen transfer efficiency of at least about six;
• and
• maintaining a ratio in the range of about 0.01 to about 0.35 between the adiabatic horsepower consumed in inducing said circulation and the total of said horsepower plus the adiabatic horsepower consumed in non-propulsive bubbling of process gas into the wastewater.

A method of aerating wastewater with flexible allocation of horsepower consumption between circulation and aeration, said method comprising:

• inducing circulation of wastewater in a loop channel along a horizontal flow path at a circulation rate which averages less than about one foot per second over the transverse cross-section of said channel,
• by discharging gas into said wastewater through gas discharge means for causing upward and forward motion of the wastewater as it passes through and exits at least one propulsion zone, said zone or zones,
• being located in and extending transversely of said flow path, and
• occupying a minor portion of the length of said flow path;
• bubbling oxidative process gas into the wastewater along said flow path outside said propulsion zone(s) through horizontally non-propulsive bubble release means having an oxygen transfer efficiency of at least about six;
• applying about 0.5 to about 5 adiabatic horsepower per million gallons of daily plant throughput for inducing said circulation, while varying the rate of release of oxidative process gas in response to the BOD of the wastewater and independently of the rate of discharge through said gas discharge means, and maintaining the ratio of said horsepower relative to the total of said horsepower plus the adiabatic horsepower consumed in non-propulsive bubbling of process gas in the wastewater in the range of about 0.01 to about 0.35.