Malodor is a complex problem due to the large range of compounds involved, their low concentrations and transient nature as well as individual sensitity to different odorous compounds. Hydrogen sulfide and ammonia are the most common source of malodor complaints. They are product of anaerobic decomposition (i.e., putrefaction) of organic matters by microorganisms. High concentration of hydrogen sulfide can be lethal and accidents involving sewer workers are not uncommon and their presence in sewers also corrode concrete resulting in damage and shorter infrastructure life. There are different approaches in solving malodor caused by H2S and NH3 including frequent cleaning and disinfection to decrease the microbial load, along with source dilution. These method is only effective for point source, but the cost becomes prohibitable for dispersed source over wide area (e.g., sewer works, landfills, waste treatment facilities). This work reports on a controlled-release antimicrobial gel that doses an optimized formulation containing biocides, metabolic inhibitors and catalysts to effectively suppress the generation of malodor. Laboratory tests using two sulfur-reducing bacteria (i.e., desulfobulbus propionicus and desulfoibrio vulgaris) indicated that chlorine dioxide and copper ion are efficient in controlling the growth of these bacteria and in suppressing biofilm formation. Introducing trace amount of homogeneous catalyst for reoxidation of reduced sulfur and metabolic inhibitor to prevent their production are effective in suppressing malodor. Field study performed in a working sewer line at the University campus (i.e., 90-160 m3/h) show that a 200 g gel is capable of reducing the H2S source concetration from 500 ppb to less than 50 ppb over the 28 days study without detrimental change in bacteria population in the sewage (< 30 % reduction).

Malodor treatment using controlled-release antimicrobial gel

248th National Meeting (2014)

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