Ключевые слова: background, clean, contamination, danger, dirty, discharge, drain, drainage, dump, ecology, effluent, environment, environmental, factory, flow, flowing, garbage, industrial, industry, lake, liquid, metal, nature, oil, pipe, plant, polluted, pollution, polution, problem, production, recycle, recycling, river, sanitation, sewage, sewer, sludge, smell, stream, system, technology, toxic, trash, treatment, tube, waste, wastewater, water, white,