Chlorine dioxide as a post-disinfectant for Dutch drinking water.

Chlorine dioxide has some important advantages over chlorine with respect to water quality (no formation of trihalomethanes, no impairment of taste and no odor) and stability when used for oxidation/disinfection of drinking water. In this paper, results are presented of experiments into the consumption and reaction kinetics of chlorine dioxide in a number of (drinking) waters in The Netherlands. It was found that chlorine dioxide consumption is related to the dissolved oxygen content (DOC) of the water and the reaction time. Water samples from a plant that applied ozonation and activated carbon filtration had a very low chlorine dioxide consumption. Other water quality parameters, including pH and CO3(2-), did not have any influence on consumption. The temporary advised Dutch guidelines of 0.2 mg l-1 (dosage) is sufficient for activated carbon treated water. For other Dutch drinking waters, however, none of the 0.2 mg l-1 chlorine dioxide remained after a reaction time of 10 min, as was also found for the water of Dutch pumping stations where chlorine dioxide is at present used for disinfection.

Mutagenic activity and presence of the strong mutagen 3-chloro-4-(dichloromethyl)-5-hydroxy-2-(5H)-furanone (MX) in chlorinated raw and drinking waters in The Netherlands.

Chlorinated surface and drinking waters in The Netherlands were analysed for mutagenic activity (Ames test) and the strong mutagen 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX). Mutagenic activity and MX were formed during chlorine treatment of raw surface waters and purified surface water. Mutagenicity was also present in finished drinking waters which had been subjected to post-chlorination, but no MX could be detected. It is proposed that the mutagens responsible for most of the activity are acidic compounds as they were mainly extractable under acidic conditions. The precursors to the mutagenic compounds formed during post-chlorination of drinking water were efficiently removed by use of ozonation/activated carbon filtration. On the other hand, coagulation (Fe(III] in the presence of activated carbon powder seemed to have hardly any effect on the mutagen precursors. The calculated mutagenicity contribution from MX to the observed TA100 activity in the waters studied was less than 20%.

Wet deposition of polycyclic aromatic hydrocarbons in The Netherlands.

The concentrations of 11 polycyclic aromatic hydrocarbons (PAH) in rainwater at four locations in the Netherlands in 1983 are reported. From literature data for these PAH in air, scavenging ratios were calculated. For PAH predominantly adsorbed on aerosols these scavenging ratios are in the range 3-13 X 10(4). For phenanthrene the scavenging ratios are in the range 0.35-2.5 X 10(4). The data for the aerosol-associated PAH at the various locations are discussed in terms of aerosol in-cloud scavenging, and are compared with reported data from Belgium and Germany. The scavenging ratios for phenanthrene are compared with those predicted on the basis of Henry's law constant and were found to be less than one order of magnitude higher than expected, possibly because of enhanced aqueous solubility.