Causes of pollution of drinking water purveyor of Tehran, Karaj River case study

The purpose of this article is to identify the causes of contamination of drinking water supply sources in Tehran especially in Karaj River. Its main question is: What are the pollutants in the Karaj River? The hypothesis is that: The most important contaminants of drinking water in the Karaj River in Tehran are in the order of priority: industrial waste (hazardous waste), solid waste and biological factors. This article is an applied and descriptive one. The population of the sample is 69 people. The method of data collection was questionnaire and library. The hypothesis has been analyzed by statistical inference method and statistical data has been analyzed by Excel and SPSS software. The results of the article show. All three variables of industrial wastes, solid wastes and biological wastes will equally affect the drinking water pollution in Tehran and have no particular priority or superiority over each other.