Ключевые слова: background, canal, chemical, clean, concrete, contamination, culvert, danger, dirt, dirty, disaster, discharge, drain, drainage, dump, ecology, environment, environmental, factory, flow, flowing, garbage, industrial, industry, liquid, metal, nature, old, outdoor, pipe, pipeline, plant, pollution, recycling, river, rust, sanitary, sea, sewage, sewer, stream, system, technology, toxic, treatment, tube, unhygienic, waste, wastewater, water,