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19.01.2020 20:49

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Выписать глаголы Past Simple ТОЛЬКО в активном залоге + перевод Modern Water Treatment Methods
The twentieth century began with the development of continuous chlorination as a means for bacteriological control, and in the first four decades the focus was on the implementation of conventional water treatment and chlorine disinfection of surface water supplies. By 1940, the vast majority of water supplies in developed countries had „„complete treatment‟‟ and were considered microbiologically safe. In fact, during the 1940s and 1950s, having a microbiologically safe water supply became one of the principal signposts of an advanced civilization. The success of filtration and disinfection practices led to the virtual elimination of the most deadly waterborne diseases in developed countries, particularly typhoid fever and cholera.
Most of the methods in use at the beginning of the twentieth century evolved out of physical observations (e.g., if turbid water is allowed to stand, a clarified liquid will develop as the particles settle) and the relatively recent (less than 120 years) recognition of the relationship between microorganisms in contaminated water and disease. A list of plausible methods for treating water at the beginning of the twentieth century was presented in a book by Hazen (1909).