NOVELTY - A gas-liquid scrubber system has a tower vessel having a gas inlet, an exhaust outlet, a perforate media support structure, and a sump; a liquid recirculation system having a pump, a nozzle, and a conduit connected between the pump and the nozzle; a mechanism for populating the media with sulfur-oxidizing microorganisms; and a mechanism for maintaining a pH of the recirculating liquid.    USE - The system is useful for removing contaminants including hydrogen sulfide from an incoming gas stream also comprising oxygen.    ADVANTAGE - The inventive system can be operated less expensively than conventional chemical scrubbers. It greatly reduces the chemical and labor costs required for odor control of wastewater treatment plant offgases. It also reduces the cost of operating activated carbon scrubbers by removing about half of incoming organic pollutants.    DETAILED DESCRIPTION - A gas-liquid scrubber system (10) comprises:    (a) a tower vessel (12) having a gas inlet (14) for receiving the gas stream; an exhaust outlet (16); a perforate media support structure between the gas inlet and the gas outlet; and a sump (18) for collecting liquid falling below the media support structure (20);    (b) a liquid recirculation system having a pump (30) fluid connected to the sump; a nozzle (32) in the tower vessel; and a conduit connected between the pump and the nozzle for spraying the media with the liquid, when a quantity of liquid is present in the sump;    (c) a mechanism for populating the media with sulfur-oxidizing microorganisms; and    (d) a mechanism for maintaining a pH of the recirculating liquid between a low limit (at least 1.0) and a high limit (at most 5.0). The perforate media support structure supports porous media (22) when the gas stream (25) passes through. The liquid used in the liquid recirculation system (26) goes back to the sump.    An INDEPENDENT CLAIM is also included for a process for removing contaminants including hydrogen sulfide from an incoming gas stream also containing oxygen, comprising:    (i) providing a porous media;    (ii) populating the media with sulfur-oxidizing microorganisms;    (iii) recirculating a liquid through the porous media;    (iv) passing the gas stream through the porous media, to permit the microorganisms to oxidize the hydrogen sulfide to produce sulfuric acid; and    (v) maintaining a pH of the recirculating liquid between a low limit and a high limit to remove the hydrogen sulfide from the gas stream.    DESCRIPTION OF DRAWING(S) - The figure shows a pictorial diagram of the system.    Gas-liquid scrubber system (10)    Tower vessel (12)    Gas inlet (14)    Exhaust outlet (16)    Sump (18)    Support structure (20)    Porous media (22)    Gas stream (25)    Liquid recirculation system (26)    Pump (30)    Nozzle (32)    Control valve (42)    PH probe (50)