Effluent Treatment without Nutrients Addition, the Bahia Sul's Case, 1999 Environmental Conference Proceedings

Luiz J. C. Quaglia, Ricardo de Aguiar Quadros & Cristóvão L. S. Santos

Bahia Sul Celulose S. A.

The present paper aims to shown the operational results and the effluent quality after elimination the use of nutrients in the secondary treatment plant at the Bahia Sul Celulose, a Brazilian 520,000 tons/year kraft sulfate pulp and paper mill. Through the evaluation of the amount of nutrients concentration in the effluent, quantifying the consumption in the secondary lagoon and optimizing the dosage, the process efficiency was monitored. The mill’s primary treatment system is constituted by 3 circular decanters, 2 thickeners and 3 dewatering presses. The plant was projected to reach an efficiency of about 90 % in the suspended solid removal. The biological secondary treatment facilities is established by an aerated lagoon followed by a polishing lagoon that objective the removal of at least 95% of the biodegradable organic matter, as required by the State environmental authorities. The mill’s secondary effluent system was projected to use phosphoric acid and urea, basic nutrients to the microbial growth. Since we know that the pulp and paper wastewater are deficient of these elements, the dosage was predict to form an equal relation of BOD/N/P of a 100/2.5/0.5 respectively. Ups to now, the dosage interruption of urea and phosphoric acid did not cause significant reduction of the removal efficiency of BOD and COD in the secondary lagoon.