ABSTRACT
By 1940, there were roughly 100 slow sand filtration plants built in the US However, improvements in design of rapid rate filter technology using chemical coagulants to treat more turbid waters, while requiring significantly less space, greatly expanded the construction of rapid sand filtration plants. Although there is a record of a slow sand filter used in 1804 for the treatment and sale of water in Scotland, the emergence of slow sand filtration began in earnest around the early 1850s in London (1852) and other major European cities. Between 1940 and 1980, only a few slow sand filtration plants were constructed in the US and very few slow sand filters were even considered when designing a new water treatment facility. A key element in slow sand filtration reemergence in northern New England was construction of a full-scale facility that met and even exceeded the treatment and operational expectations of the small system.
