Method and system for ozone vent gas reuse in wastewater treatment

Abstract

A system and method for ozone vent gas reuse is provided. The disclosed system and method involve controlling or conditioning the ozone vent gas stream or degassing unit vent gas stream and directing the stream to a mechanically agitating contactor in an aerobic section of the wastewater treatment system. The oxygen content of the vent gas stream is controlled so as to ensure sufficient oxygenation to the aerobic section of the wastewater treatment system. Control may be effected by adjusting the oxygen content of the vent gas stream in response to sensor or measurement inputs characterizing the gas contents of the vent gas stream or the dissolved oxygen levels. The volumetric flow of the vent gas stream to the aerobic section may also be controlled by adjusting the rotational speed of the mechanically agitating contactor in an aerobic section of the wastewater treatment system.

1 . A method for supplying supplemental oxygen to a wastewater treatment system comprising the steps of:
 directing an oxygen containing feed stream to an ozone generator;   operating the ozone generator to produce an ozone containing gas stream;   directing the ozone containing gas stream to an ozone treatment system within the wastewater treatment system to produce an ozone treated effluent and; and an ozone vent gas stream; and   directing the ozone vent gas stream to a mechanically agitating contactor in an aerobic section of the wastewater treatment system;   wherein the oxygen content of the ozone vent gas stream is controlled so as to ensure sufficient oxygenation to the aerobic section of the wastewater treatment system by adjusting the oxygen content of the ozone vent gas stream in response to sensor or measurement inputs characterizing the gas contents of the ozone vent gas stream or the dissolved oxygen level in the aerobic section of the wastewater treatment section.   
     
     
         2 . The method of  claim 1  further comprising the step of directing the ozone vent gas stream to an ozone destruct system configured to destroy any ozone contained in the ozone vent gas stream. 
     
     
         3 . The method of  claim 1  wherein the step of directing the ozone vent gas stream to the aerobic section of the wastewater treatment system further comprises mixing or combining the ozone vent gas stream with a make-up oxygen containing stream and directing the combined stream to the aerobic section of the wastewater treatment system. 
     
     
         4 . The method of  claim 1  wherein the step of adjusting the oxygen content of the ozone vent gas stream further comprises adjusting the flow of the oxygen containing feed stream to the ozone generator. 
     
     
         5 . The method of  claim 1  wherein the step of adjusting the oxygen content of the ozone vent gas stream further comprises adjusting the power supplied to the ozone generator. 
     
     
         6 . The method of  claim 1  wherein the step of adjusting the oxygen content of the ozone vent gas stream further comprises adjusting the flow of a make-up oxygen containing stream to the ozone vent gas stream. 
     
     
         7 . The method of  claim 1  wherein the volumetric flow of the ozone vent gas stream is controlled so as to ensure sufficient oxygenation to the aerobic section of the wastewater treatment system by adjusting the rotational speed of the mechanically agitating contactor in an aerobic section of the wastewater treatment system. 
     
     
         8 . A ozone vent gas reuse system for a wastewater treatment plant comprising:
 an oxygen containing feed stream;   an ozone generator configured to receive the oxygen containing feed stream and produce an ozone containing gas stream   an ozone contactor for contacting an effluent with the ozone containing gas stream to produce an ozone treated effluent and an ozone vent gas stream;   an ozone destruct system configured to receive the ozone vent gas stream and destroy any ozone contained in the ozone vent gas stream;   a supplemental oxygen delivery conduit coupling the ozone vent gas stream to a mechanically agitating contactor in an aerobic section of the wastewater treatment plant; and   a control unit for controlling the oxygen content of the ozone vent gas stream so as to ensure sufficient oxygenation to the aerobic section of the wastewater treatment system by adjusting the oxygen content of the ozone vent gas stream in response to sensor or measurement inputs characterizing the gas contents of the ozone vent gas stream or the dissolved oxygen level in the aerobic section of the wastewater treatment section.   
     
     
         9 . The system of  claim 8  wherein the ozone vent gas stream is mixed or combined with a make-up oxygen containing stream and directing the combined stream to the aeration basin of the wastewater treatment system. and the combined stream is directed to the aeration basin of the wastewater treatment plant. 
     
     
         10 . The system of  claim 8  wherein the control unit adjusts the oxygen content of the ozone vent gas stream by adjusting the flow of the oxygen containing feed stream to the ozone generator. 
     
     
         11 . The system of  claim 8  wherein the control unit adjusts the oxygen content of the ozone vent gas stream by adjusting the power supplied to the ozone generator. 
     
     
         12 . The system of  claim 8  wherein the control unit adjusts the oxygen content of the ozone vent gas stream by adjusting the flow of a make-up oxygen containing stream to the ozone vent gas stream. 
     
     
         13 . The system of  claim 8  wherein the control unit further controls the volumetric flow of the ozone vent gas stream by adjusting the rotational speed of the mechanically agitating contactor in an aerobic section of the wastewater treatment system so as to ensure sufficient oxygenation to the aerobic section of the wastewater treatment system. 
     
     
         14 . A method for supplying supplemental oxygen in a wastewater treatment system comprising the steps of:
 directing an oxygen or ozone containing sludge stream within the wastewater treatment system to a degassing unit;   separating an oxygen containing off-gas from the sludge stream to produce a supplemental oxygen containing gas stream; and   directing the supplemental oxygen containing gas stream to an aerobic, anaerobic or anoxic section of the wastewater treatment system   wherein the oxygen content of the supplemental oxygen containing gas stream is controlled in response to sensor or measurement inputs characterizing the gas contents of the ozone vent gas stream.   
     
     
         15 . The method of  claim 14  wherein the step of directing the supplemental oxygen containing gas stream further comprises mixing or combining the supplemental oxygen containing gas stream with a make-up oxygen containing stream and directing the combined stream to the aerobic, anaerobic or anoxic section of the wastewater treatment system. 
     
     
         16 . The method of  claim 14  wherein the step of directing the supplemental oxygen containing gas stream further comprises directing the supplemental oxygen containing gas stream to a mechanically agitating contactor in the aerobic, anaerobic or anoxic section of the wastewater treatment system, the mechanically agitating contactor configured to assist or enhance in the dissolution of oxygen from the supplemental oxygen containing stream into the contents of the aerobic, anaerobic or anoxic section of the wastewater treatment system. 
     
     
         17 . The method of  claim 14  wherein the step of directing the supplemental oxygen containing gas stream further comprises directing the supplemental oxygen containing stream to a digester for micro-oxygenation of the contents of the digester.