Toxicity Effects of Sludge on the Survival and Reproduction of Daphnia

By Syama S. Veerina, Nick Parker, and Clifford B. Fedler

Toxicity resting with aquatic biota is an accepted practice t'or determining the potential toxicity ot' waste water and other eftiuents that may be discharged to the nation's water resources. Similarly. runoff reaching playas and lakes from agricultural lands treated with sludge can also be tested to evaluate its et't'ect on flora and fauna. These tests can be indirectly used to identify the toxic effects of effluent and runoff on survival and reproduction of fish populations. However. organisms that are selected for toxicity tests should be easily cultured. have a short life cycle. and be representative of local populations. The fresh water invertebrate currently used in toxicity tests is a micro- crustacean, daphnia. Two separate batches of bioassay experiments were performed at Texas Tech University, utilizing soil samples treated with sludge and sludge samples from a municipal waste water treatment plant. Results of the toxicity test with soil samples indicated that the No-Observed-Effect- Concentration and the Lowest-Observed-Effect-Concentration for survival were 80% and 100% respectively, for soil samples treated with 16 tons/ acre of sludge. For soil samples treated with 0 and 8 tons/acre of sludge. the survival rates of daphnia were not effected at any concentration. Reproduction was suppressed by Aspic when daphnia were exposed to 10.9% concentration of soil treated with sludge at 16 tons/acre. A 50%o suppression of reproduction occurred when daphnia were exposed to 50% concentration of soil treated with sludge at 16 tons/acre. With a sludge application rate of 8 tons/acre, the reproduction was suppressed by 25% at a treatment concentration of 60%.   Neither 25% nor the 50% - Inhibition Concentrations were affected in the treatment involving a sludge application rate of 0 tons/acre. It is inferred from this experiment that runoff from soil treated with 16 tons/acre seems to have an effect on the reproduction and survival of daphnia. Experiments utilizing both wet and dry sludge samples from a waste water treatment facility indicated that the Lowest-Observed- Effect-Concentration and the Lowest-Observed-Effect-Concentration for survival were respectively. 80% and 100% concentrations of the sludge. Reproduction data indicated that the 25% Inhihitionn Concentrationwas 40.3% for wet sludge end 19.2C%. for dry sludge, whereas the 50%-lnhibition Concentration on reproduction was 54% for wet and 92.5% for dry sludge. This indicated that the inhibition of reproduction by the wet sludge was caused by the anaerobic conditions of the sludge. whereas in the dry sludge it may have been caused by dissolved metals present in the sludge.

In Research Highlights - 1996, Vol. 27. Texas Tech University, Department of Range, Wildlife & Fisheries Manangement.

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