Ключевые слова: aeration, aerial, cleaning, construction, ecology, engineer, environment, environmental, equipment, factory, filter, helmet, horizontal, male, man, microbiology, midadult, outdoors, people, pollution, process, purification, purity, qualitycontrol, recycling, round, seriousman, sewage, sewer, sewerage, sludge, steel, storage, supply, tank, treatment, urban, wastewatertreatment, water, watertreatmentplant,