Toxicity of alum sludge extracts to a freshwater alga, protozoan, fish, and marine bacterium

The effects of alum sludges on several trophic levels of aquatic organisms were investigated. Alum sludge from 10 water treatment plants in the U.S.A. were used in acute toxicity studies with the marine bacterium Photobacterium phosphoreum (Microtox test) and the protozoan Tetrahymena pyriformis and chronic toxicity studies with the diatom Selenastrum capricornutum and the fathead minnow (Pimephales promelas). S. capricornutum was more sensitive than any other test species to sludge extracts. S. capricornutum growth inhibition varied with the alum sludge tested and the receiving water chemistry. Algal growth inhibition was observed at pH 5. Sludge extracts obtained using receiving water, which had a hardness of less than or equal to 35 mg calcium carbonate per litre inhibited growth of S. capricornutum at all pH values studied (5-9). There are 35 references.