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

Study of the technologies of wash water treatment from contact clarifiers

Summary

The results of the laboratory studies of twelve flocculant kinds used for wash water treatment from contact clarifiers are presented. The optimal dosages of flocculant were determined. Two of the flocculants studied were selected that could ensure the maximum degree of water clarification at the minimum concentration of residual aluminium, residual polyacrylamide and suspended solids in water. It was stated that the sludge generated during water clarification had 99.9% moisture content. It was proved that Flopam FO 4240 PWG and Маgnafloc LT-22S flocculants ensured good sedimentation of pollutants present in wash water. Possible use of chemical and chemical free filtration in «Fil’tr Polimernyi» manufactured by «Samenviro» LLC as well as of membrane filtration in UNA-620A hollow fiber module (based on Microza^® pressure membranes) in a pilot plant rendered by «Pall Evrasia» LLC was considered.

Key words

turbidity , flocculant , wash water , contact clarifier , residual aluminium , residual polyacrylamide , optimal dosage of chemical