chapter  8
49 Pages

Anions in wastewaters

The level of boron in raw waters has tended to increase, resulting from its greater use in cleansing materials and in industrial processes [1]. As sewage treatment does not significantly reduce this level the increase is passed to surface waters, which may then be utilised for crop irrigation or potable water supply. Many varieties of fruit can tolerate no more than 0.5mg L−1 of boron [2] in irrigation water. The US Environmental Protection Agency [3] recommends limits of 0.75mg L−1 for most fruits, 1.0mg L−1 for most cereals, potatoes, peas and tomatoes and 2.0mg L−1 for tolerant species including sugar beet, turnips and cabbage. The Anglian Water Authority [4] apply criteria such that the ‘maximum desirable’ limit for crop irrigation is 0.5mg L−1 and the ‘maximum permissible’ limit is 1.0mg L−1. They also apply criteria of 0.8 and 1.0-1.2mg L−1, respectively, to potable water abstractions.