Methods of and apparatus for removing odors from process airstreams

Apparatus for scrubbing a steam of process air from a sewage composting facility, wherein the process air has been used to aerate compost for passage therethrough, the process air including ammonia, sulfides, and malodorous organic compounds, the apparatus comprising:

• a first tower having an upper end and a lower end with an inlet at the lower end and an outlet at the upper end, the first tower including an atomizing station for treating the process air with an atomized dilute sulfuric acid mixture as the air rises in the first tower from the lower to the upper end, the mixture having atomized droplets of a selected size, the first tower further including a sump at the lower end thereof for removing the dilute sulfuric acid mixture from the rising airstream and a recirculating means for recirculating the mixture and spraying the mixture at a recirculating station into the airstream upstream of the atomizing station and beneath the upper end of the first tower, the mixture being sprayed at the recirculation station having droplets of a size substantially larger than the atomized droplets;
• a second tower having an upper end and lower end with an inlet at the upper end connected to the outlet of the first tower and an outlet at the lower end, the second tower including means proximate the upper end thereof for oxidizing the organic sulfides in the airstream subsequent of removing ammonia and active organic compound therefrom by treating the airstream with an atomized solution of sodium hypochlorite prior to descent of the airstream in the second tower;
• and
• a third tower having a lower end an upper end, the lower end having an inlet connected to the outlet of the second tower and the upper end providing an outlet for the airstream, the third lower including atomizing means at a site proximate the lower end thereof for treating the airstream with an atomized hydrogen peroxide solution with atomized droplets of a selected size as the airstream rises in the third tower to maintain the oxidation reaction wile removing chlorine from the airstream, the third tower further including means of precipitating products of the oxidation reaction from the airstream by recirculating the hydrogen peroxide solution and spraying the hydrogen periodic solution into the airstream in a droplet size substantially larger than the atomized droplet size at a location downstream of the site of the atomizing means for treating the airstream with hydrogen peroxide.