A review of the effects on aquatic ecosystems of acid iron waste from the production of titanium dioxide by the sulphate process

Abstract

Damaging effects of acid iron waste to biota have been demonstrated in the vicinity of coastal and estuarine outfalls. The toxic properties have been confirmed in laboratory studies with algae, invertebrates and fish. So far it appears that the toxicity is associated with either decreased pH (below pH 6.0-7.0) and/or iron concentrations above at least 0.5-1 mg Fe/l. However, due to the complex nature of the waste and its fate in the aquatic environment causal relations are difficult to assess. Leakage of metals from precipitated iron hydroxide flocs may be among the serious stress factors. In dumping areas of the open sea there are few and uncertain observations of harm to biological communities. With the possible exception of two estuarine recipient areas the risk of accumulation of waste constituents appears to be small