Keeping in mind the volume of the polluted effluents formed annually at woodworking enterprises and the zero waste policy for rational use of bioresources, it is very important to extract quantitatively and qualitatively the formed biomass from the effluents to achieve more its rational utilization. The effective removing of biomass will allow to return the purified wastewater in the basic technological cycle. The formed sewage sludge of woodworking wastewater as a product of the coagulation can be used successfully for soil improvement and for producing building materials or sorbents. The plywood production wastewater generated at hydrothermal treatment of hardwood is dramatically polluted with biomass consisting of hemicelluloses, low molecular lignin and tannin fragments, wood extractives. The coagulation is one of the cheapest processes for obtaining the biomass from such type of wastewater. The aim of this work was to increase the efficiency of the coagulation process of plywood production wastewater by developing a new composite coagulant based on PEI (CCPEI). The composite coagulant represented a polymeric complex formed with PEI macromolecules and colloid particles having the reactive functional groups. The effect of the content of PEI in the coagulant, the CCPEI dosage and the pH value of the coagulation process on the biomass removal was studied.