Choosing coagulants and flocculants for the local treatment of wastewater of pulp and paper industry

Summary

The results of studies on removing lignosulfonates, suspended solids and sulfur-containing compounds from pulp and paper industry wastewater by chemical treatment are presented. As chemicals the following coagulants were studied: alumina, ferrous sulfate, iron (III) sulfate, and flocculants Praestol and RusFloc, that differ in charge, molar mass, and ionic activity. In the course of the experiment, it was found that the most effective removal of lignosulfonates and sulfur-containing compounds from wastewater proceeded in the presence of ferrous sulfate coagulant and Praestol 810 cationic flocculant. In this case, easily settling thickened sludge is formed and the efficiency of removing sulfide ion is 92%, the color of water decreases 3–4 times. The optimal dose of the coagulant as metal ion is 300 mg/dm³, the dose of the flocculant is 1.5 mg/dm³. Comparison of the activity of RusFloc cationic flocculants in terms of settling time, sludge layer thickness, clarified water COD, showed that the use of RusFloc 504 cationic flocculant is most effective for the coagulation of wastewater containing lignosulfonates. The optimal dose of the chemical was 5 mg/dm³. Studies on wastewater treatment by coagulation-flocculation in the presence of ferrous sulfate coagulant and RusFloc 504 flocculant at pH 8.5 showed 70% reduction of COD of organic compounds – lignosulfonates, and more than 90% color. On the basis of the conducted studies, the choice of conditions and effective chemicals for the local treatment of pulp and paper industry wastewater is substantiated.

Key words

coagulation , pulp and paper industry , flocculation , optimal dosage of chemical , pulp production , lignosulfonates , sulfide-ion

Development of a method for producing carbon sorbents by thermochemical pyrolysis of liquid cellulose waste

Summary

In the process of high-quality cardboard and newsprint production, cellulose is used prepared by thermal treatment of hardwood or softwood with cooking solutions based on alkali metal sulfites or bisulfites. As a result, spent cooking liquors containing lignosulfonates and lignosulfonic acids are generated that are subject to concentration by evaporation. A method is presented for producing carbon sorbent from evaporated liquor in the presence of an activator – potassium hydroxide; the method involves thermochemical pyrolysis of the raw material. It has been established that the developed method provides for one-stage production of carbon sorbents with properties comparable to engineering grades of active carbon. Tertiary treatment of pulping wastes by adsorption to remove lignosulfonates using active carbons of AG-3, BAU grades and carbon sorbents based on liquid lignosulfonates was studied. The obtained adsorption isotherms have allowed to establish that the carbon sorbent samples are applicable for removing organic compounds – lignosulfonates from water. A basic process flow scheme for the utilization of lignin-containing wastes with the production of sorption materials by thermochemical pyrolysis has been developed.

Key words

wastewater treatment , carbonic sorbent , pulp and paper industry , lignin-containing waste , adsorption isotherm

Syktyvkar Timber Processing Complex: Solving of Wastewater Treatment Problems

Summary

Peculiarities of the wastewater treatment process of the Syktyvkar timber processing complex typical for pulp and paper industry are described. Data on studies of the problem of activated sludge swelling are presented. It is proposed to solve this problem using the aerobic selector. On the basis of simulation results the scheme of reconstruction of preaerators of inlet flows into an aeration tank is proposed; according to this scheme the wastewater mix and return activated sludge are supplied to the first tunnels of preaerators operating as a selector of bacteria. The article presents a flow chart of wastewater and sludge treatment for retechnologization of existing facilities consisting of the following stages: treatment of wastewater at fine treatment mechanical grates and aerated sand catchers; degassing of wastewater before primary sedimentation tanks; installation of belt filter presses for treatment of excess activated sludge; installation of equipment for additional dewatering of primary sludge and excess activated sludge up to 50% of moisture content; disinfection of wastewater.

Key words

wastewater , sludge index , retechnologization , aerator , pulp and paper industry , aerobic selector