In our research, we studied the specificity of formation of the water quality in water sources with a limited debit in the lake Staroe, located in the southern part of the West Siberian Plain, and in the river Malaya Karla, located in the Republic of Kazan in Russia. We carried out a study of the efficacy of detention of phytoplankton, contained in the initial raw water on a floating filter with expanded polystyrene (EPS) bed. We developed three technological models, which provide the removal of algae by using a floating filter with further coagulation of the remaining suspended substances for processing of the raw water from the low power surface sources. The application of the proposed water pretreatment technologies from the low power sources can significantly reduce the problem of the drinking water supply to the small populated areas in different climatic conditions. (C) 2017 The Authors. Published by IASE. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).