Water pollution is caused by both domestic and industrial sources. Domestically, septic tanks can leak liquid waste into land drainage systems and waterways if not functioning properly. Industrially, factories dump untreated waste like plastic, rubber and metal directly into water bodies. This dumping harms sea life and can take years for some materials to decompose. Overall, the document discusses the main causes of water pollution as improper waste disposal from both households and industry that releases harmful contaminants into aquatic environments.