Toxicity evaluation of waste drilling fluids

Ten drilling wastes was tested. Bioassays were done on liquid and SPP phase. As test organisms green algae Kirchneriella obesca and Botrydium granulatum were used, plant Lepidium sativum and cladoceran Simocephalus vetulus. Electrolytic conductivities were from 6,43 to 240 mS/cm. Liquid phase was toxic for K. obesca in range of dilutions 0.21 to 0.019 considered as LC50. Parameter LC50 for S. vetulus in rhe category of dilutions was 0,125 to 0,0078, SPP phases diluted by brown soil had LC50 for greens Botrydium granulatum from 0.25 to 0.094 and for Lepidium sativum 0.56 to 0.039. Maximum quantum efficiency (QY) of photosystem II plants growing on mixtures of drilling fluids with soil not depend on kind of drilling fluid whereas minimal fluorescence F0 does.

Cumulated oxygen consumption ad respired carbon dioxide showed that dilutions greater than 1:16 are generally, excluding single case not harmful for microbial and fungal activity. At the end of 96 h experiments oxygen consumption in control sample had ca 21 µl /g/96 h whereas remaining samples consumed usually 17- 20 µl /g/96 h independently on dilution.Samples of spent drilling mud as saline-barytic, ultra-inhibitive water-base drilling fluid for reactive shales, and chloride - polymeric had inhibited O2 consumption ca 25 %. in dilution 1:16 to 14,4-15.46 µl /g/96 h. The most toxic is drilling fluid belong to polymeric type which inhibit metabolism up to dilution 1:32. Treatment procedure of dilution in 1:1 is not sufficient to suppress toxicity. 

The research leading to these results has received funding from the Polish-Norwegian Research Programme operated by the National Centre for Research and Development under the Norwegian Financial Mechanism 2009-2014 in the frame of Project Contract No Pol-Nor/200375/58/2013.