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In a pressure swing adsorption system for the supply of enriched oxygen to a variable demand wastewater treatment system, the oxygen product to feed air ratio is increased during periods of reduced oxygen demand, with the enriched oxygen being supplied to the wastewater treatment system at lower pur

In a pressure swing adsorption system for the supply of enriched oxygen to a variable demand wastewater treatment system, the oxygen product to feed air ratio is increased during periods of reduced oxygen demand, with the enriched oxygen being supplied to the wastewater treatment system at lower purity levels during such periods of reduced demand than the purity levels supplied under maximum demand conditions. Operation in this manner enables oxygen recovery to be enhanced and the power requirements to be reduced under such variable demand conditions.

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In a pressure swing adsorption process for the production of oxygen for delivery to a variable oxygen demand waste-water treatment system, said oxygen being produced by a pressure swing adsorption system capable of selectively adsorbing nitrogen, said system having at least two adsorbent beds, each

In a pressure swing adsorption process for the production of oxygen for delivery to a variable oxygen demand waste-water treatment system, said oxygen being produced by a pressure swing adsorption system capable of selectively adsorbing nitrogen, said system having at least two adsorbent beds, each of which undergoes, on a cyclic basis, cocurrent depressurization from a higher adsorption pressure to one or more intermediate pressures with release of an enriched oxygen stream from the product end of the bed; counter-current depressurization to a lower desorption pressure and/or purge with release of selectively adsorbed nitrogen from the feed end of the bed; and repressurization to said higher adsorption pressure, with at least a portion of the gas released from one bed during said cocurrent depressurization step(s) being passed to one or more other beds initially at lower pressures for pressure equalization and/or purge purposes, said pressure swing adsorption process being carried out in said system such that an adsorption front of the selectively adsorbed nitrogen is formed in each bed and advances toward the product end thereof during said cocurrent depressurization step, the improvement comprising: (a) maintaining an oxygen product/feed air ratio in each bed in the system, during periods of maximum oxygen demand for said wastewater treatment system, such that the enriched oxygen product released from said bed is essentially at a design oxygen purity level corresponding to the maximum design oxygen demand in said wastewater treatment system, said adsorption front of said selectively adsorbed nitrogen advancing toward but not reaching the product end of the bed during the cocurrent depressurization of the bed to said intermediate pressure(s); (b) increasing said oxygen product/feed air ratio in each bed, during periods of reduced oxygen demand in said wastewater treatment system, such that the enriched oxygen product released from said bed is at a lower oxygen purity level than the design level, said adsorption front of selectively adsorbed nitrogen breaking through at the product end of the bed during said cocurrent depressurization of the bed, the amount of enriched oxygen product released from said bed under the lower purity conditions corresponding essentially to the reduced oxygen demand for said wastewater treatment system; and (c) adjusting the product/feed ratio between the conditions of step (a) for maximum oxygen demand, wherein oxygen product is released essentially at said design oxygen purity level, and the higher product/feed ratios of step (b) for lower, variable oxygen demand conditions, wherein oxygen product is released at a lower oxygen purity level than said design level, thereby decreasing oxygen product purity in response to lower oxygen demand, whereby oxygen recovery is enhanced and power requirements are reduced in the operation of said pressure swing adsorption system in conjunction with said variable oxygen demand wastewater treatment system.