The Effect Of Preozonation On The Control Of Trihal Omethane Formation

Abstract

Abstract A study was made to obtain a better understanding of the manner in which preozonation affects trihalomethane (THM) formation with respect to humic acid, citric acid, and 11 aromatic compounds which were components of humic acid, all in dilute aqueous medium. Ozonation before chlorination is able tonotonly decrease, butalso increase the concentrations of THM precursors. The compounds which are inherently high THM precursors, such as resorcinol, aniline, salicyl-aldehyde, phenol, andp-hydroxybenzoic acid, are controlled with respect tothe increase inthe amount ofozone consumed, but the compounds which have essentially no or alow potential for chloroform formation, such as hydroquinone. salicylic acid, methoxybenzene. benzaldehyde. and benzole acid, produce their maximum THM levels at a certain value of ozone consumed. When 1mg of organic carbon consumes more than 8 mg of ozone, THM formation from thetested aromatic compounds isdepressed by ozone. Aliphatic carbonyl compounds which are the products resulting from the ozonation of aromatic compounds are not significant THM precursors. The preozonation of humic acid is not as effective in reducing its THM formation potential (THMFP) as when simple aromatic compounds are treated. However, the organic materials in the effluent from a biological treatment process usually have a high THMFP, in comparison with organic compounds which are contained in raw wastes. Therefore, there is a limitation in the effectiveness of utilizing biological treatment to remove the precursors of THM.