Toxicological assessment of drilling wastewater treatment quality

Abstract

Purpose. To determine the optimal combination and consumption of coagulants and flocculants in the treatment of drilling wastewater, followed by determination of the acute lethal toxicity of the obtained illuminated liquid phase. Methods. Primary clarification of the liquid phase of drilling waste was carried out by the method of chemical coagulation using the organic coagulants "Magnafloc" and "ECOFLOC" as a coagulant. In case of insufficient degree of purification of drilling wastewater by coagulation method, an additional method of purification with Zetag 8180 flocculants and cellulose gum was used. After the cleaning process, a toxicological analysis of drilling wastewater was carried out using the biotesting method to determine the acute lethal toxicity of the water on the crustacean Ceriodaphnia affinis Lilljeborg. Results. In the process of experimental research, a number of experiments were conducted to determine the optimal consumption of coagulants and flocculant for the treatment of drilling wastewater, followed by the determination of the acute lethal toxicity of the obtained illuminated liquid phase of drilling water. First, combinations of «Magnafloc» coagulant and Zetag 8180 flocculant were tested. The conducted studies showed that the most effective cleaning occurs during the primary clarification of the liquid phase of drilling waste by the method of chemical coagulation using the organic coagulant «Magnafloc» and additionally the flocculant Zetag 8180 in concentrations of 1.2 g/dm3 and 1 kg/m3, respectively. When using these chemical reagents in the above-mentioned concentrations, the 2nd level of acute lethal toxicity was determined in purified drilling wastewater (water is slightly toxic). The following experimental studies were conducted in order to identify the most effective combination of coagulant «ECOFLOC» and flocculant cellulose gum. According to the results of the conducted research, it was established that the most effective cleaning occurs during the primary clarification of the liquid phase of drilling waste by the chemical coagulation method using the coagulant «ECOFLOC» and the flocculant - cellulose gum in concentrations of 1.2 g/dm3 and 1.3 kg/m3, respectively. When using these chemical reagents in the above-mentioned concentrations, the 2nd level of acute lethal toxicity was determined in the purified drilling wastewater (the water is slightly toxic). Conclusions. In general, it should be noted that such wastewater requires more thorough treatment in case of possible discharge to water bodies, and its use is possible only in repeated technological processes of drilling. The results of biotesting must be used for screening highly toxic environmentally hazardous chemicals and controlling the toxicity of various categories of wastewater at all stages of their formation and discharges into water bodies as an integral indicator in their quality control.