Woodworking wastewater biomass effective separation and its recovery
¹Latvian State Institute of Wood Chemistry, 27 Dzerbenes Street, LV–1006 Riga, Latvia
2Riga Technical University, Faculty of Material Science and Applied Chemistry, 3/7 Paula Valdena Street, LV–1048 Riga, Latvia
The aim of the study was to develop a new Al-based hybrid coagulant that was effective in removing wood biomass from the wastewater formed in water basins of plywood plants during hydrothermal treatment of birch wood. The organic-inorganic coagulant was prepared by interaction of high molecular polyethyleneimine (PEI) with the inorganic polyaluminium chloride-based composite coagulant (KHPAC) in aqueous medium. Owing to the hybrid nature, the developed coagulant could simultaneously perform both the coagulation and flocculation function. The influence of a hybrid coagulant composition, its dosage, pH and a temperature on the efficiency of wastewater biomass separation was investigated. The best coagulation-flocculation efficiency was achieved with the hybrid coagulant having a mass ratio of PEI/KHPAC equal to 0.3–0.5 and at the optimal dosage of 70–80 mg L-1, reaching 97% yield of the total wood biomass and 60% yield of the lignin recovery. The efficient dosage of PEI and KHPAC in hybrid coagulant was about 1.4–1.8 and 1.7–2.2 times lower than if these coagulants/flocculants were used alone. As a result of the coagulation-flocculation process, wood biomass sludge is formed, which is a sufficiently large source of renewable organic matter, with the potential to obtain value-added products. The components of the biomass sludge were found to have surface activity and binder properties, as well as cation exchange capacity. Based on these properties, its ability to structure dusty soil particles with the formation of mechanically resistant soil aggregates was studied.