Research Product

Freshwater (Selenastrum capricornutum) and estuarine (Skeletonema costatum) algae were exposed to liquid wastes from 10 industrial sites in laboratory bioassays. All wastes affected algal growth, either by stimulation only or by stimulation at low concentrations and inhibition at high concentrations. Generally, S. capricornutum and Sk. costatum responded similarly to each waste: SC20's (concentrations that stimulated growth by 20%) were between 0.01 and 20.0% waste; EC50's (concentrations that inhibited growth by 50%), between 5.1 and 85.5% waste. Since toxicity to S. capricornutum was usually lost by the sixth or seventh day of exposure in all wastes except one, it is recommended that algal tests be carried out for 4 days. Both algal species were more sensitive to the wastes than were Daphnia magna (freshwater) and Mysidopsis bahia (estuarine). Only three wastes were toxic to D. magna and two were toxic to M. bahia. SC20 and EC50 values are used to calculate the 7-day, 10-year flow rate of the receiving stream required for dilution of effluents to non-toxic concentrations.