Determination of some bacteriological pollution parameters at Büyükçekmece lake

Abstract

This study covers investigations made on the bacterial pollution of Büyükçekmece lake, which supplies 16 % of Istanbul's drinking water. The data was collected at four stations, namely; Bahsayiş, Çakıldere, Tepecik, and Mezarlıkönü between January and December 1999 and compared periodically with standards. The parameters like temperature, pH, biochemical oxygen demand (BOD), chemical oxygen demand (COD), total and fecal coliform were measured. The results obtained showed that, pH and temperature were within the range of standards. On the other hand biochemical oxygen demand (BOD) and chemical oxygen demand (COD) varied according to the sampling sites and seasons. When the quality of lake water is evaluated in relation to these parameters, it generally fits with the criteria of secondary quality water but, sometimes it shows values agreeing with primary quality however; sometimes it drops down below limits of even secondary class. Many differences were observed in the total and fecal coliform values. Fecalvıı coliforms could not be encountered in some months, but there was a considerable increase at 3 stations in February. Generally an increase was observed in the amounts of total coliforms, during summer months which showed a parallelism in all stations. There are several factors that affect the increase in total and fecal coliform to a certain degree. One of these is the domestic wastes discharged into the brooks without any treatment. The other is that some residential areas are very close to the lake. When the results are compared with standards, we find some differences in the samples taken from different stations, depending on the seasonal conditions. These differences give clues about microbial pollution. We can infer that these differences are related to the changes in the amount of organic substances present in the lake and the seasonal factors. A comparison between the results of four stations fully enlightens us about the sources of pollution. According to these results, Büyükçekmece lake is being polluted by effluent entering the lake through the brooks flowing into the lake without any treatment. These polluting sources are the sewerage and domestic wastes of Tepecik, Çatalca, and surround villages.