Ключевые слова: background, biology, brown, canal, clean, contamination, dirty, drain, drainage, dump, ecology, environment, environmental, factory, filtration, flowing, industrial, industry, liquid, manufacturing, mud, natural, pipe, pipeline, plant, polluted water, pollution, pond, purification, purified, recycle, removal, reservoir, river, sanitary, sanitation, sedimentation, sewage, sewer, smell, substance, treatment, tube, turbine, unhygienic, urban, valve, waste, wastewater, water,