Caracterização física, química, mineralógica e geotécnica do lodo da estação de tratamento de água visando aplicação em obras geotécnicas

Abstract

In the process of treating raw water in water treatment plants (WTPs) are generated large amounts of waste. This residue namead ETA sludge has characteristics that vary with the nature of the raw water, with the unit processes and with the chemical products used in the treatment, presenting large variations, both between different ETA's and over time in the same ETA. The final disposition of the sludge from ETA-Oeste da Cagece is in the landfill located in the municipality of Caucaia. Motivated by the need to give this waste a more appropriate final destination, both from an environmental, technical and economic point of view, this research aims to define its main physical, chemical, environmental and geotechnical characteristics for this waste, with the aim of subsidizing future studies regarding its behavior and its influence in mixtures with other materials, in addition to defining the best alternatives for use in geotechnical works. For this, the sludge collected at two different times (dry period and winter) was subjected to physical-chemical, environmental tests, and geotechnical characterization tests. Some test results were in line with expected results, such as the massive presence of organic matter in its composition. The formation of cementitious lumps was verified as the sludge lost moisture, and the impact of this formation on geotechnical tests. In the sedimentation test, for example, various concentrations of the deflocculant were used, in addition to that recommended by the standard as alternatives to maintain the dispersion of the solution in the densimeter. In the Liquidity Limit and Plasticity tests, when carrying out the tests in hygroscopic humidity, a loss of affinity of the residue with water was observed. To obtain results in these tests, the conventional methodology also needed to be adapted to overcome the challenges presented by the composition of the sludge and its behavior after drying. In the other tests, the direct relationship with the eutrophication and water quality of the treated source can also be seen in the composition of the sludge, evidenced in the images obtained through microscopy, thermogravimetry, the chemical levels obtained and in the environmental characterization tests.