S . 8
The simple structure of H 2
S makes it an easy target for oxidation by ozone . In addition , ozone ’ s unique structure tends to create free radicals , making them highly reactive , especially in water . As part of these reactions , additional free radicals form , which can be even more reactive than ozone . These tend to create additional radicals as they react , in what is termed a free radical chain reaction . The current technology for producing ozone has benefitted from more than 45 years of ongoing development , resulting in costeffective and robust operation . Using little more than an oxygen separator , a corona discharge chamber and some compressors and other electrical components , onsite generation of ozone is relatively simple and safe , unlike most other commercially available treatments . Because of the way ozone is produced , oxygen is necessarily going to be part of the treatment gas cocktail when using it . This is beneficial because oxygen is also an oxidiser . With an oxidation potential of 1.23 V , oxygen reacts slower than ozone but is an excellent complement to it .
Oxygen ’ s other primary benefit is increasing the dissolved oxygen ( DO ) concentration of the wastewater , encouraging the growth of aerobic bacteria , which do not create compounds that are odorous , corrosive or otherwise harmful to collection systems . It also eliminates the ability of SRB to produce sulfides , either by removing it entirely or promoting the growth of aerobic species that will oxidise any sulfides before they enter the wastewater stream . 3
Combined use for treatment
The combined forces of oxygen and ozone are at the top of the list of robust and green methods to treat and prevent of odour and corrosion in collections systems . The generation and infusion of these two gases into wastewater collection systems has proven to be clean , safe and cost-effective . The first method of action is the powerful destructive effects of ozone on H 2
S , quickly converting it to sulfites
and sulfates on contact . In addition , ozone ’ s antimicrobial properties can help to reduce the presence of SRB and other microorganisms present on pipe walls . As a product of its reaction , oxygen is generated . This in turn adds more power to the oxygen portion of the treatment gas cocktail , which is providing secondary treatment by significantly increasing DO , and allows for more complete utilisation of infused treatment gases . Oxygen will also oxidise H 2
S , though at a much slower rate . Because of these indiscriminate and powerful oxidising characteristics , concerns are sometimes raised about ozone attacking the wastewater infrastructure itself . However , this is unlikely to occur in application , especially in wastewater where liquid-phase infusion is implemented , due to the high ratio of liquid volume compared to pipe surface area per unit pipe length and the extreme availability of reactants in the liquid portion . •
References
1 : American Society of Civil Engineers , ASCE ’ s Infrastructure Report Card , ASCE , 2009 , http :// www . infrastructurereportcard . org /
2 : A . Matthews et al ., Proceedings of the Water Environment Federation , WEFTEC 2010 : Sessions 101-112 , pp . 7591-7611 ( 21 )
3 : US EPA , Odor & Corrosion Control in Sanitary Sewerage Systems and Treatment Plants , Design Manual , EPA / 625 / 1-85 / 018 , Cincinnati , 1985
4 : F . J . Beltran , Ozone Reaction Kinetics for Water & Wastewater Systems , Lewis Publishers , 2004
5 : Lenntech , Water Disinfection Application Standards ( For EU ), 1998 , www . lenntech . com
6 : J . A . Drago et al ., Ozone : Science & Engineering , 2010 , 32 ( 1 ), 43-55
7 : Plasma Technics , Inc ., Plasma Block Product Line , 2011 , www . plasmatechnics . com
8 : P . A . Terry , International Journal of Chemical Engineering , Volume 2010 , Article ID 250235 , 2010
Greg Bock
VP & GENERAL MANAGER
ANUE WATER TECHNOLOGIES k + 1 760 476 9090 J info @ anuewater . com j www . anuewater . com
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