Ridho, M. R.Jose, C.Balatif, N.2014-03-272014-03-272014-03-27Rangga Dwijunanda Putrahttp://repository.unri.ac.id/xmlui/handle/123456789/5954Drainage basin of Siak River in Perawang, a village in the district of Siak, is one of the downstream areas. It is a severe drainage basin which is indicated by the decreasing quality of Siak River that has already exceeded the standard indicator of sustainable river. This research aims to analyze the water quality of Siak River using microbiological parameters (microbial contamination indicators). The parameters applied are based on the standard quality of water according to Government Regulation No. 82 Year 2001. The water samples from drainage basin of Siak River were collected in July 2013 from four sampling sites (9 , 10 , 11 and 12). Microbial contamination indicators such as fungi, Coliform, and E. coli were determined by total plate count and total bacteria by Most Probable Number (MPN). The results showed that sampling site 11 had relatively higher number of total plate count and MPN, while the sampling site 10 was relatively lower and significantly different in total plate count and MPN compared to the other sampling sites. Based on Government Regulation, the results of the research showed that the microbiological parameters exceeded the standard qualityotherDrainage basin of Siak Rivermicrobial indicatorsMost Probable Number (MPN)Other