Anaerobic treatment of sulphate-containing waste streams

Sulphate-containing wastewaters from the paper and board industry, molasses-based fermentation industries and edible oil refineries present difficulties during anaerobic treatment, leading to problems of toxicity, reduction in methane yield, odour and corrosion. The microbiology and biochemistry of dissimilatory sulphate reduction are reviewed in order to illustrate the potential competition between sulphate reducers and other anaerobes involved in the sequential anaerobic mineralisation process. The theoretical considerations which influence the outcome of competition between sulphate reducers and fermentative, syntrophic, homoacetogenic and methanogenic bacteria are discussed. The actual outcome, under the varying influent organic composition and strength and sulfate concentrations which prevail during digestion of industrial wastewaters, may be quite different to that predicted by thermodynamic or kinetic considerations. The factors governing competitive interactions between SRB and other anaerobes involved in methanogenesis is discussed in the context of literature data on sulphate wastewater treatment and with particular reference to laboratory and full-scale digestion of citric acid production wastewater.