This paper presents the usability of EM-Farming™ preparation for work optimization of preliminary settling tanks. The settling tanks studied are the first units of soil-vegetable wastewater treatment plants where domestic sewage is purified. The preliminary results of the study as well as field observations suggest that EM-Farming™ application activates and supports pollutant removal in the settling tanks. The preparation use results in sewage system declogging, the reduction in deposit volumes, nearly total decomposition of sludge blanket and fats in the preliminary settling tanks as well as odour elimination and decrease in odour nuisance of the tanks. The preparation tested increases significantly the effectiveness of organic matter removal measured by decreases in BOD5, COD and total suspended solids. ...