A CONTRIBUTION TO THE PROBLEM OF TRIHALOMETHANE FORMATION FROM THE ARABIAN GULF WATER

The Arabian Gulf water at Umm Al Nar (Abu Dhabi, UAE) is analyzed for components expected to influence trihalomethane (THM) formation in case of chlorination. Chromatograms of chlorinated clean seawater show four peaks corresponding to bromoform (BF), di-bromochloromethane (DBCM), di-chlorobromomethane (DCBM) and chloroform (CF). The BF peak, representing ca. 95% of the THMs, is suitable for detection of oil pollution. This has been substantiated during an actual oil spillage that affected the intakes. The effect of chlorination on the concentration of the various THMs is examined in detail to very high Cl2 levels. The formation of BF and Br-rich THMs prevails, depending on the Br--ion content of seawater. This has been confirmed by experiments in which seawater is artificially enriched with KBr. In these solutions the amounts of the THMs formed depend on the Cl2 level. At low levels the amounts of BF and DBCM are independent of [Br-]. At higher Cl2 levels a double logarithmic relationship operates. The chlorination of I--enriched seawaters for long times produces three iodo(halo)methanes suspected to be di-chloroiodomethane (DCIM), chlorobromoiodomethane (CBIM) and di-iodochloromethane (DICM). Additions of Belgard EV 2000 (anti-scale) and Belite (anti-foam) to seawater do not affect THM formation from seawater. Recommendations are given for actions to be followed in case of oil pollution near a desalination plant. These aim to the complete elimination or considerable reduction in the concentration of THMs in potable water.