Toxicity evaluation of spent drilling mud and drilling waste.
Roman Żurek, Aleksandra Jamrozik, Andrzej Gonet
Vol. 34, no. 1 (2017), s. 243-257, 
Spent of water based mud (WBM) were tested in this study. Bioassays were done on spent WBM, brine after filtration and solid phase (SP) after filtration on the press. As test organisms, green algae Kirchneriella obesa and Botrydium granulatum were used, along with the cladoceran Simocephalus vetulus and the plant 13 Lepidium sativum. Electrolytic conductivity was between 6.43 and 240 mS/cm. The liquid phase was toxic for K. obesa in the range of dilutions between 0.21 and 0.019, considered as LC₅₀. The parameter LC₅₀ in the category of dilutions was 0.125 to 0.0078 SPP for S. vetulus, 0.25 to 0.094 SPP for green alga Botrydium granulatum when diluted by brown soil and 0.56 to 0.039 SPP for Lepidium sativum. Maximum quantum efficiency (QY) of plants’ photosystem II (PS II), growing on mixtures of drilling fluids with soil, did not depend on the kind of drilling fluid, whereas minimal fluorescence (F₀) did. Rinsing the salt out of drilling fluids in a 1:1 proportion was effective only for bentonite mud in the test with L. sativum.
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