Replacement of fresh water use by final effluent recovery in a highly optimized 100% recovered paper mill

摘要

A further closure of the water circuit in paper mills with a relative high optimization of theirnwater network is limited by the increase of contamination in the water and runnability problemsnof the paper machine. Therefore, new strategies for saving water must be focussed on thentreatment of final effluents of the paper mill, aiming to obtain high quality water that may replacenfresh water use in some applications. An appropriate treatment train performed at pilot scale,nconsisting on a previous clarification stage followed by anaerobic and aerobic treatments,nultrafiltration, and reverse osmosis, made possible producing the highest water quality from thenfinal effluent of the mill. Anaerobic pre-treatment showed very good performance assisting thenaerobic stage on removing organics and sulphates, besides it produced enough biogas for beingnconsidered as cost-effective. Permeate recovery depended on the silica content of the paper millneffluent, and it was limited to a 50–60%. The reject of the membranes fully met the legislationnrequirements imposed to effluents arriving to municipal wastewater treatment plants.