Assessment of the Microbiological Quality of the River Tisa in Serbia - page 02


Study area

The samples for microbiological analysis were collected during the spring and autumn of 2010 from three sites on the River Tisa (Table 1). The sites were determined by the Republic Hydrometeorological Service of Serbia as part of their own routine water quality testing. The Ada site receives domestic sewage from the town of Senta (25.000 inhabitants) located upstream, and is also effected by the sugar and fermentation industry of this town. The Novi Bečej site receives a great amount of urban wastewater since it is located downstream from the town of Bečej (40,000 inhabitants). The Titel site was chosen to measure the effects which Tisa’s tributary river Begej has on the water quality. This site is affected by urban wastewater from the town of Zrenjanin (33,000 inhabitants). The coordinates of the sampling sites were measured by GPS (“Garmin Etrex”) and charted using the ArcView software (map 1:300.000, system WGS_1984).

Material and methods

Microbiological analyses

All samples were processed in the laboratory within 12 hours from the sampling and a total of 16 parameters were analysed. Microbiological indicators of the sanitary quality and indicators for the organic assessment of contamination were analysed using the standard procedures (’’Official Gazzete of the SFRY’’ number 33/87, ’’Official Gazzete of the SRY’’ number 42/98) and EU-Bathing water quality directive 2006/7/EEC.

For an assessment of recent faecal pollution and the potential presence of pathogenic bacteria, total coliforms (cultivated on eosin-methylene blue agar at 37°C for 24h), faecal coliforms (cultivated on MacConkey agar at 44°C for 24h) and intestinal enterococci (cultivated on dextrose tellurite agar at 37° for 24h) were monitored by the membrane filtration method.

The identification of isolated coliform bacteria was tested using the API 20e identification kit (Biomerieux, 1995). The presence of potential pathogen species was observed by cultivation on meat peptone agar (MPA). To accomplish the sanitary analyses, the presence of Proteus sp (cultivated on phenylalanine agar at 37°C for 24h), sulphite reducing clostridia (cultivated on sulphite agar at 37°C for 48h), Pseudomonas aeruginosa (cultivated on pseudomonas agar at 42°C for 24h)  and Bacillus sp. (cultivated on blood agar at 30ºC for 24h) was also determined.

To provide information about overloading of water with organic compounds, the presence of heterotrophic, oligotrophic bacteria (pour plate technique with nutrient agar, incubation at 22ºC for four days) and the phosphatase activity index (Matavulj et al., 1983) were monitored.

Microbiological analyses of sediment included the quantification of coliform bacteria (membrane filtration of diluted sediment samples, incubation on eosin-methylene blue agar at 37ºC for 24h), identification of isolated coliforms (API 20e), isolation of bacteria resistant to mercury (spread plate technique of diluted sediment samples, incubation on MPA with mercury at 37ºC for 24h) and the presence of potential pathogens (spread plate method of diluted sediment samples on MPA at 37ºC for 24h).