APPLICATION OF BIOSURFACTANTS IN WASTEWATER BIOFILTRATION TECHNOLOGY USING DAPHNIA MAGNA

Abstract

When solving water purification problems, including for the needs of industrial fish farming, biofiltration methods involving planktonic organisms, in particular branchiopod crustaceans, deserve special attention. A specific filtration apparatus feeding daphnia can provide highly efficient wastewater treatment from suspended fine particles that have a low settling velocity and are not able to be retained on mechanical filters. An important advantage of this method of water treatment is the ability to use the resulting zooplankton biomass as live feed for fish farming.   The filtration properties of zooplankton can be improved by growing it in the presence of surfactants of biological origin, which, in addition, improve the absorption of nutrients by cladocerans and intensify their growth. In this study, the possibility of using a preparation of trehalosolipid biosurfactants obtained from the culture fluid of Rhodococcus erythropolis AU-1 for intensive growth of Daphnia magna culture for the purpose of biological treatment of water bodies was evaluated. It was established that the toxicity of trehalosolipids is dose-dependent, in particular, their minimum concentration at which the death of daphnia was observed within 24 hours of exposure was 300 mg/l, and the LC50 at the same duration of exposure was 479 mg/l. The maximum non-toxic concentration of the trehalosolipid biosurfactant is 200 mg/l. Concentrations of trehalosolipids in the range of 1-3 mg/l provide an increase in the density of daphnia culture by 1.3-1.7 times compared to the control. To evaluate the efficiency of biofiltration of Daphnia magna in the model experiment, water from the mechanical filter of the experimental recirculation system of the Yuriy Fedkovych Chernivtsi National University was used. The value of the optical density of the discharge water decreases by more than half after one day of daphnia presence in it, and after 4 days - by 7 times. The addition of biosurfactants leads to a more efficient filtration process, with the best results obtained when using the preparation with a concentration of 1 mg/l. The use of biosurfactants in concentrations of 1, 2 and 3 mg/l leads to a decrease in electrical conductivity and total mineralization compared to the control. At the same time, the pH and soluble oxygen content did not change compared to the control.