Biofiltration process and apparatus for odour or voc treatment

Abstract

A bioreactor and process is described which offers a transition or continuum between one or more of (a) from biotrickling filter conditions to biofilter conditions, (b) changing media characteristics, c) liquid or nutrient recirculation rates or frequency, (d) pH, (e) gas velocity, (f) retention time along the gas flow passage or (g) cross-sectional area. For example, media may be arranged in sections of a rectangle, with gas flow in a horizontal direction sequentially through the sections, and liquid flow in a vertical direction from top to bottom in one or more sections. Zonal control of process conditions may be provided as the gas passes from inlet to outlet and liquid is introduced at the top of one or more zones and flows down by gravity.

1 . A process comprising
 a) passing a gas to be treated through two or more adjacent zones, the zones differing in one or more of (a) extent of biotrickling filter conditions or biofilter conditions, (b) changing media characteristics, c) liquid or nutrient recirculation rates or frequency, (d) pH, (e) gas velocity, (f) retention time along the gas flow passage (g) extent of irrigation if any or (h) cross-sectional area.   
     
     
         2 . The process of  claim 1  further comprising a step of flowing a liquid vertically through at least one of the zones. 
     
     
         3 . The process of  claim 2  wherein the liquid comprises water, nutrients, and acid. 
     
     
         4 . The process of  claim 2  wherein the liquid is water collected from the bottom of at least one of the zones. 
     
     
         5 . The process of  claim 1  further comprising
 a) providing zonal control of process conditions as the gas passes from an inlet to an outlet and liquid is introduced at the top of one or more of the zones and flows down by gravity.   
     
     
         6 . A process comprising,
 a) providing a gas to a reactor;   b) passing the gas in a generally horizontal direction through a biotrickling zone of the reactor   c) passing the gas in a generally horizontal direction through a biofilter zone of the reactor.   
     
     
         7 . The process of  claim 6  further comprising
 d) passing the gas in a generally horizontal direction through an intermittent biotrickling or biofilter zone positioned between the biotrickling zone and the biofilter zone of the reactor.   
     
     
         8 . The process of  claim 6 , further comprising:
 d) selecting an inert media for the biotrickling zone and a biologically active media for the biofilter zone.   
     
     
         9 . The process of  claim 6 , further comprising:
 d) recirculating liquid through the biotrickling zone continuously, and;   e) providing once through, and intermittent irrigation of the biofilter zone.   
     
     
         10 . The process of  claim 9 , further comprising
 f) passing the gas in a generally horizontal direction through an intermittent biotrickling zone positioned between the biotrickling zone and the biofilter zone of the reactor   g) providing once-through and intermittent irrigation to the intermittent biotrickling zone, wherein the irrigation provided to the intermittent biotrickling zone is provided at a higher flow or frequency than the irrigation provided to the biofilter zone.   
     
     
         11 . The process of  claim 6 , further comprising introducing a liquid at a top of the biotrickling zone, and distributing the liquid evenly across a media provided in the biotrickling zone. 
     
     
         12 . The process of  claim 9  further comprising introducing irrigation liquid at a top of the intermittent biotrickling zone or the biofilter zone periodically. 
     
     
         13 . A reactor comprising
 a) a gas inlet   b) a biotrickling zone in communication with the inlet;   c) a biofilter zone in communication with the biotrickling zone and spaced horizontally from the biotrickling zone; and   d) a gas outlet in communication with the biofilter zone.   
     
     
         14 . The reactor of  claim 13 , further comprising an intermittent biotrickling zone in communication with and spaced horizontally from the biotrickling zone and in communication with and spaced horizontally from the biofilter zone. 
     
     
         15 . The reactor of  claim 14 , wherein the intermittent biotrickling zone is provided between and adjacent the biotrickling zone and the biofilter zone. 
     
     
         16 . The reactor of  claim 13 , wherein the reactor is generally rectangular. 
     
     
         17 . The reactor of  claim 13 , further comprising an inlet gas distribution manifold. 
     
     
         18 . The reactor of  claim 17 , wherein the biotrickling zone and biofilter zone are provided adjacent a first side of the inlet gas distribution manifold, and the reactor further comprises:
 a) A second biotrickling zone provided adjacent a second opposed side of the inlet gas distribution manifold; and   b) A second biofilter zone in communication with and spaced horizontally from the second biotrickling zone.   
     
     
         19 . The reactor of  claim 13 , further comprising a sump positioned to collect draining liquid from the biotrickling zone and the biofilter zone, and a recycle pump in communication with the sump and configured to provide the drainage liquid to the biotrickling zone. 
     
     
         20 . The reactor of  claim 13 , further comprising a an intermediate biofilter zone in communication with and spaced horizontally from the biotrickling zone and in communication with and spaced horizontally from the biofilter zone