Wastewater pollution with detergents is one of the environmental problems associated with the rational use of water resources. The existing methods of physicochemical wastewater treatment, despite their efficiency, are open to secondary environmental pollution. Biological coagulation/flocculation methods are widely used with the use of plant waste. The aim of this research is the use of ferric iron obtained by the bacterial-chemical method and bentonite to reduce the chemical oxygen demand in wastewater containing detergents. It was identified that the use of Fe2(SO4)3 obtained by the bacterial-chemical method with thionic bacteria Acidithiobacillus ferrooxidans BIT 1 and bentonite as a clay material is promising. At the same time, it was found that the highest reduction degree in the chemical oxygen demand – 88.1 ± 7.9% in wastewater was noted in the variation where the bacterial-chemical ferric iron in the amount of 1.75 g/L was used in combination with bentonite in the amount of 600 mg/L.