[Chloroform concentration in drinking water of the Lódź municipal area]

Chloroform is one the most important pollutants, formed in the process of chlorination of water from surface intakes. The city of łódź is supplied with water mainly from surface intakes containing considerable amounts of organic material and from deep water intakes. The aim of this study was to determine concentrations of selected organic compounds including chloroform in raw water, water after chlorination and on different stages of purification as well as in water introduced to the municipal water supply system. Chloroform was analysed in n-pentane extracts by gas chromatography with ECD. The detection limit of the analytical method was 1 microgram/l. Concentrations of chloroform in raw water were very low, in most cases below the limit of detection. As a result of chlorination level of chloroform in water increased reaching as high as 120 micrograms/l. It has been shown that activated charcoal was not efficient in removing chloroform from water. Concentrations of chloroform were much lower in water from the municipal water supply system serving the northern part of town, where water from surface intakes was mixed with water from deep intakes. Concentrations exceeding 30 micrograms/l were determined only in the summer season. In both investigated parts of municipal water supply systems seasonal changes of chloroform concentration were observed with maximum values in June-August. The concentration of chloroform in water samples collected in different quarters of town were strictly correlated with its concentration in treated water from the municipal water supply system serving the quarter.