The aim of the study was to determine the impact of various methods of oil mixing with wastewater on

properties of synthetic municipal wastewater containing edible oil (SMW+0.02% m/v rapeseed oil). The study was

carried out in 3L glass, cylindrical reactors to which SMW+0.02% were introduced. Various methods of its mixing

with water were applied: mechanical mixing (SMW+0.02%+mixing) and sonication (SMW+0.02%+ultrasounds).

The wastewater was sonicated at 35 kHz for 30 min. The constant temperature conditions were maintained during

the experiment for each mixing method (15°C, 20°C and 30°C). The analysis of parameters (pH, COD, BOD5

and

long chain free fatty acids concentration) of raw wastewater and after 2, 4, 6, 24, 48 and 72 hours of inoculation

was performed to determine the effect of mixing method.

The most signifi cant changes in wastewater chemical parameters after the introduction of the oil were observed

in the case of COD. For SMW+0.02%+ mixing a slow increase in COD within 24 hours of the process was observed.

In the case of SMW+0.02%+ultrasounds the increase and the decrease of COD value were observed in reference

to the initial value. The changes in acids concentrations observed in reactors with SMW+0.02%+ultrasounds were

referred to the ones observed in reactors with SMW+0.02%+mixing but changes were more intense in the fi rst

reactor. The use of ultrasounds in pre-treatment of wastewater resulted in the intense appearance of palmitic acid

for 6 hours. Regardless of the emulsion formation method (mixing or ultrasounds), the concentration of oleic acid

and linoleic acid was reduced. The biggest changes in free fatty acids concentration were observed for palmitic,

oleic and linoleic acids after 24 hours.