Clay bricks added with effluent sludge from paper industry: Technical, economical and environmental benefits

Recently, it was indicated that a feasible industrial alternative to valorize the sludge obtained from the treatment of waste water effluent of paper fabrication in Europe is its use as raw material in the production of clay bricks. The present technical note is an open report, probably first in Americas, on a Brazilian industrial-scaled solution for this kind of sludge. As a novelty, the sludge was added to a mixture of clays for improved technical properties of construction bricks. Both bricks, added with 10 wt% of sludge and conventional pure clay bricks for comparison, were simultaneously fired at a relatively low temperature of 750 °C according to the ceramic fabrication procedure. The technical characterization was performed by linear shrinkage, water absorption and mechanical compression tests as per Brazilian standards. The brick consolidated structure was analyzed by optical microscopy. Environmental impact was evaluated by solution test and atmospheric emission by monitoring the release of SO2, NOx, TOC, CO and particulate material, according to Brazilian standards. The results showed that, owing to its composition and firing temperature, the addition of paper sludge into clay bricks contributes to a substantial reduction in price associated with a saving of 3% of fuel similar to that reported for Spanish kilns, during the industrial firing stage. The paper sludge added clay bricks attended the technical and environmental standards.