Use of Septic Tank Sludge as Raw Material in the Manufacture of Bricks

The present paper analyzes the feasibility of using septic tank sludge subsequently treated in an anaerobic pond as raw material in the ceramic industry. An experiment was conducted involving the manufacture of 500 bricks using 6.5% (dry weight) of sludge at a ceramic plant in the Northeast of Brazil. To reproduce the methodologies, the same conditions and methods used by the local ceramic industry were adopted. To evaluate the bricks produced and environmental risk, compressive strength, water absorption and lixiviation tests were carried out, obeying current Brazilian norms, according to international standards. Results show the technical feasibility of using sludge as raw material in the red ceramic industry, highlighting the firing temperature of the bricks as a determinant variable. Moisture content of the sludge-clay mixture emerges as limiting factor in the manufacturing process. The moisture value determined as acceptable in the study was 22%.