Bromide affecting drinking water mutagenicity.

The effect of bromide on the mutagenicity of artificially recharged groundwater and purified artificially recharged groundwater after chlorine, ozone, hydrogen peroxide, permanganate, and UV treatments alone and in various combinations was studied. The highest mutagenicity was observed after chlorination, while hydrogen peroxide-ozone-chlorine treatment produced the lowest value for both waters. Chlorinated waters, which were spiked with bromide, had up to 3.7 times more mutagenic activity than waters without bromide after every preoxidation method. 3-Chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX) was found to correspond as much as 76% of the overall mutagenicity in the waters not spiked with bromide. MX formation was found to be lower when the treated water contained bromide, implicating the formation of brominated MX analogues. Trihalomethane formation increased when the treated water contained bromide.

Molecular size fractions of treated aquatic humus.

The effects of ozone, chlorine, hydrogen peroxide, and permanganate on the aquatic humic matter with different molecular size fractions and the organic acid formation in drinking water treatment were studied. Aquatic humus in lake water (LW), artificially recharged groundwater (AW), and purified artificially recharged groundwater (PW) were fractionated by high-pressure size-exclusion chromatography (HP-SEC) with UV-254nm detection before and after oxidation, a technique which resulted generally in seven peaks. The sum of the molecular size fractions (SMSF) of the LW was reduced by 47% during the bank filtration process, and the SMSF of the AW was reduced by 55% during the process in the water treatment plant. The oxidation of the AW resulted in reductions in the range of 18-35% of the SMSF; the respective range of the PW was 15-69%. However, the content of the total organic carbon (TOC) reduced only slightly, and a high correlation between the TOC and the SMSF (0.911) was observed in the whole material. The greatest decreases appeared in the highest-molecular-weight fractions while the low-molecular-weight fractions remained nearly unchanged. The total content of the six organic small-molecular-weight acids (sum of the organic acids, SOA) (formate, acetate, propionate, pyruvate, oxalate, and citrate) varied between 0.1-5.1% and 0.1-9.7% of the reduced TOC in the AW and the PW, respectively. The formation of the SOA, especially of oxalate, was the greatest after hydrogen peroxide combined with ozonation (as much as 1,100 microg/L), while chlorination resulted in the SOA of < 50 microg/L.

Disinfection by-products in Finnish drinking waters.

Disinfection by-products (DBPs) were measured in plant effluents of 35 Finnish waterworks, which utilized different treatment processes and raw water sources. DBPs were measured also from the distribution systems of three waterworks. Di- and trichloroacetic acids, and chloroform were the major DBPs found in treated water samples. The concentration of six haloacetic acids (HAA6) exceeded the concentrations of trihalomethanes (THMs). Chlorinated drinking waters (DWs) originating from surface waters contained the highest concentration of HAA6 and THMs: 108 and 26 microg/l, respectively. The lowest concentrations of DBPs were measured from ozonated and/or activated carbon filtrated and chloraminated DWs. Higher concentrations of HAA6, THMs, and adsorbable organic halogens were measured in summer compared to winter. The levels of chlorinated acetic acids, chloroform, and bromodichloromethane correlated positively with mutagenicity. Past mutagenicity levels of DWs were examined. A major reduction in the use of prechlorination, increased use of chloramine disinfection, and better removal of organic carbon were the most important reasons for the 69% decrease in mutagenicity from 1985 to 1994.

Molecular size distribution of natural organic matter in raw and drinking waters.

The purpose of this study was to compare the molecular size distribution (MSD) of natural organic matter (NOM) in raw waters (RW) and drinking waters (DW), and to find out the differences between MSD after different water treatment processes. The MSD of NOM of 34 RW and DW of Finnish waterworks were determined with high-performance size-exclusion chromatography (HPSEC). Six distinct fractions were generally separated from water samples with the TSK G3000SW column, using sodium acetate at pH 7 as an eluent. Large and intermediate humic fractions were the most dominant fractions in surface waters (lakes and rivers), while in artificially recharged groundwaters and natural groundwaters intermediate and small fractions predominated. Water treatment processes removed the two largest fractions almost completely shifting the MSD towards smaller molecular size in DW. Granular activated carbon (GAC) filtration, ozonation, and their combination reduced all humic fractions compared to the conventional treatment. Humic fractions correlated with total organic carbon (TOC) content and chemical oxygen demand, this being especially true in RW. The results demonstrate that the HPSEC method can be applied for a qualitative and also for rough estimate quantitative analyzes of NOM directly from RW and DW samples without sample pretreatment.