Page 49 - New Trends in Green Construction

APPLICATION OF THE CIRCULAR ECONOMY IN THE RECOVERY OF WASTEWATER TREATMENT SLUDGE FROM WWTP AND PAPER MILLS TO OBTAIN SUSTAINABLE BRICKS
Luisa Molina Sampedro, Carmen Martínez García, Teresa Cotes Palomino, Francisco. A. Corpas Iglesias
Keywords: MSW sludge, Cotton linters sludge, Sustainable bricks, Circular Economy 1. Introduction
The Circular economy model is based on the intelligent reuse of waste, which becomes raw material to feed natural cycles, or simply to be transformed into new technological products with minimum energy expenditure (Lett, 2014). One of the most important types of waste produced as a result of human activity is sludge from the purification of both urban and industrial wastewater. If these wastes are not managed properly, they can contribute significantly to environmental pollution. The use of the ceramic process as a technique for recovering sludge from urban and industrial wastewater treatment plants for the manufacture of traditional bricks as construction materials opens up a reuse route for these wastes, with a marked environmental advantage (Elías and Bordas, 2017).
In the p r e s e n t work, sludge from the purification of wastewater from the cleaning, firing and bleaching system of cotton linters used in a paper money and security factory, and sludge from the purification of urban wastewater together with a mixture of clay traditionally used by the ceramic industry of Bailén, to obtain bricks for partition walls, have been used. The results showthattheproductsobtainedcomplywithcurrentregulations intermsofmechanicalresistance and have better insulating properties compared to traditional bricks.
2. Materials and methods
Specimens of a mixture of clay (30 % red clay, 30 % blond clay and 40 % black clay), with different percentages of sludge, have been produced in the range between 5-20 % by weight of residue. Previously, both the clays and the sludge used have been characterized. The prepared mixtures have been formed by extrusion using a laboratory extruder NANNINI RENATO MACHINERY S.R.L., at a working pressure of 2.2 bars, and has been sintered in laboratory electric furnace at a maximum temperature of 950 oC. The pieces obtained have been tested for weight loss, water absorption (UNE 772-21), water absorption by capillarity (UNE-EN 772-11), determination of open porosity and apparent density (ASTM-C373-14a) and resistance to compression(UNE-EN772-1:2011+A1).Aporosity characterizationstudyhasalsobeencarried out using mercury intrusion porosimetry.
3. Results and discussion
The addition of both residues has not been a problem at the time of manufacturing the pieces, that is to say, in the process of extrusion, drying and sintering. For both types of waste, the weight loss of the piece increases with the percentage of waste added, due to the amount of organic matter they contain. The values of this parameter for both wastes are of the same magnitude, as both have similar organic matter contents, as indicated by the LOI values. The results obtained for the
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New Trends in Green Construction