Reducing sulfates concentration in the tannery effluent by applying pollution prevention techniques and nanofiltration

Abstract

a b s t r a c tThe use of large quantities of sulfuric acid and other sulfur-containing chemicals causes high sulfate concentrations in the wastewater of a tannery. The aim of this work was reducing the sulfate concentration in the final wastewater from a tannery. For that, firstly a study about the main sulfate sources in a tannery was carried out and the total sulfates load in the tannery wastewater was evaluated. Two measures for sulfates reduction were studied: the recycling of unhairing wastewater to the soaking drums and the reuse of the chromium sulfate from the tanning washing wastewater after its separation by nanofiltration (NF). The first measure proposed was studied experimentally in laboratory drums of 5 L of volume. Two series of experiments with different volumes of unhairing wastewater in the soaking bath were carried out. The quality of the final leather was evaluated by means of mechanical tests. NF experiments were carried out in a laboratory pilot plant with a spiral wounded membrane element. Concerning the results, the combination of 50% unhairing wastewater and 50% of fresh water was appropriate in order to obtain leather with an acceptable quality. Besides, it drove to a diminution of approximately 10% in the addition of sulfide in the unhairing. Related to the NF experiments, 97% of the sulfates were rejected by the membrane. The separated ions could be recycled to the tanning drums. The application of the two measures (firstly the recycling of the unhairing wastewater and secondly the NF of the tanning washing wastewater) drove to a reduction of 14.82 kg SO 4 À2 t À1 of raw hide.

Characterization of tannery effluent wastewater by proton-induced X-ray emission (PIXE) analysis to investigate their role in water pollution

“…These compounds are also discharged as effluents containing considerable amount of Cr and other organic matter, toxic trace metals, sulfide, and lime (Tariq et al 2005). It is estimated that a single tannery annually disposes around 40,000 t of basic chemicals and 15,000 t of Cr-sulfate as effluents, which drastically affects the natural environment (Galiana-Aleixandre et al 2011;Tariq et al 2005). Moreover, the natural water reservoirs are also polluted by the continued seepage of these toxic effluents into the water basin and make the water hazardous for human consumption (Bhuiyan et al 2010;Tariq et al 2005).…”

From waste treatment to resource efficiency in the chemical industry: recovery of organic solvents from waters containing electrolytes by pervaporation

“…Some other works focused on the concentration of hazardous components from wastewaters in order to be utilized. Galiana-Aleixandre et al (2011) proposed nanofiltration for the separation of chromium sulphate from the tanning washing wastewater and re-use in the tanning drums.…”

Comparison of the performance of ultrafiltration and nanofiltration membranes for recovery and recycle of tannins in the leather industry

“…The membrane processes are emerging as a new alternative technology aimed at remedying this problem. This is because they are considered clean technologies to treat wastewater from the tanning industry in order to recycle and reuse some chemicals which are used during the leather manufacturing process (Galiana-Aleixandre et al, 2011;Gallego-Molina et al, 2013;Molinari et al, 2004). The main advantage of membrane processes is its inherent simplicity, moderate temperature conditions with no phase change and the negligible use of chemicals (Baker, 2004;Dasgupta et al, 2015).…”