AN ENVIRONMENTALLY-FRIENDLY TECHNOLOGY FOR THE PROCESSING OF ACCUMULATED COLLOIDAL SLUDGE-LIGNIN PRECIPITATES IN THE BAIKALSK PULP AND PAPER MILL

The accumulated hazardous colloidal precipitates of sludge lignin in the Baikalsk Pulp and Paper Mill are located in the vicinity of settlements and four hundred metres from Lake Baikal. The area of their location is considered to be mudflow dangerous; therefore, any failure in the sediment storage tanks can trigger socio-ecological technogenic catastrophes that might entail irreversible environmental consequences for the entire Southern Pribaikalye district. This paper presents a new environmentally-friendly technology for processing accumulated waste in the Baikalsk Pulp and Paper Mill. A series of industrial experimental tests on the freeze treatment of colloidal sludg-elignin precipitates was carried out under natural conditions. Changes in the physical and chemical properties of the precipitates were studied. A technological scheme for the waste recycling is proposed. It is established that three fractions are formed following the freeze treatment of colloidal sludge-lignin precipitates, including demineralized water (up to 25%), mineralized water (up to 15%) and a re-structured colloidal precipitate (up to 60%). The total volume of the precipitate is shown to decrease to 40%. After the freeze treatment of the sludge-lignin precipitate, the degradation of its colloidal structure occurs. Under this process, lignin substances and colloid-bound moisture pass into the water phase, accompanied by the transition of the amorphous lattice of gibbsite to diaspore. The freeze treatment of colloidal sludge-lignin precipitates in the Baikalsk Pulp and Paper Mill leads to a decrease in their toxicity from the third to the fourth hazard class. The wastes were systematized using the morphological and quantitative composition analysis. This allowed a waste recycling technology to be developed based on the principles of freeze treatment. The proposed environmentally-friendly technology for recycling wastes in the Baikalsk Pulp and Paper Mill is expected not only to reduce costs and to raise the social and ecological safety at the enterprise with the total economic effect of 17,7 billion RUB, but also to obtain a valuable compound - α-Al₂O₃ - for the production of М-400 cement.

Baikal Pulp and Paper Mill, waste, sludge lignin, freezing

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