Uses of ozone and its adverse effect?

Beneficial uses in Civil Engineering (for other uses, see link below) # Flocculant - small doses added early in processing surface waters helps natural compounds in the water act as flocculants. # Oxidant - added at any step, it serves to oxidize soluble metals to (usually) insoluble states, and organic molecules such as MIB and geosmin to a state where BAC can consume them... removing / reducing common precursors for THM and HAA formation. Bromate production discussed below. # Sterilant - added after initial processing, it will kill any non-colony-forming or non-slime-forming organism faster and/or at lower doses than chlorine. Things to watch for: # Ozone is not the entire "swiss army knife" of water treatment. # Ozone off gas must be contained. (Ozone destructors are available.) # Ozone is corrosive to steel, uncoated ductile iron, most common gasket materials, and most paints. Concrete is unaffected by the presence of ozone. # Ozone capital equipment is higher than regular chemical feed, but payback can be short (even with power included). # Ozone requires more maintenance than standard chemical feed. # Ozone decays naturally in water in minutes (well or surface water) to hours (ultrapure). # Ozone survives about 1 cm or less into carbon filter beds, or even DE or sand filter beds. Adverse effects of ozone # The EPA has declared that the bromate ion is a "potential human carcinogen". Ozone converts natural bromide ion found in some water sources to bromate, requiring monitoring and control. The effective elements are: bromide present+, pH-, ozone dose * time in contact+, contaminants- (+ means increase in this increase bromate production, and - the opposite). Note that all chemical oxidizers can, in the presence of visible light, produce bromate from bromide ion... not just ozone. # Ozone cannot be used as the secondary sterilant (added to water-to-distribution). Not only will it tend to damage common distribution system materials, but it will decay back to oxygen, leaving the balance of the distribution system unprotected from infection (or sustained colonization).