Experimental tests were performed on surface water samples after coagulation-flocculation settling treatment steps. The main operating parameters of sonolysis experiments were as follows: ultrasound frequency 20 kHz (constant for all tests), sonolysis time 2 - 50 min., ultrasound energy 2000 - 8000 kJ, ultrasound amplitude 20 - 80%, hydrogen peroxide doses 2 - 10 mg H2O2/L.
Aerobic mesophiles bacteria (37 0C) content was measured and the best removal efficiency was 97% (initial content 9x104 CFU/ml) for direct sonolysis and over 99.9% for hybrid sonolysis in case of short irradiation time.