In the 19th century Hamburg’s waterworks took water from the Elbe without treatment. Plans for filtering it existed, but they were not carried out, for reasons of cost. In neighboring Altona the water was already filtered. In 1892 cholera broke out, and more than 8,600 people died in Hamburg. In Altona hardly anyone died. The filtration plant on the island of Kaltehofe, under construction since 1890, was completed in 1893. It stayed in operation until 1990. After the epidemic, water treatment in Hamburg and other cities could no longer be stopped.