Removal of chromium from tannery wastewater by tannery lime liquor; a very cost effective method

Tanning industries produces large quantities of waste water which on direct discharge causes severe environmental pollution. Basic chromium sulphate used in the tanning process is not consumed fully and about 30-40% of it is washed away to the environment and thus creates severe environmental problem especially to the aquatic system. Here a simple method is developed to remove the chromium content of the tannery waste water. Waste water discharged from tannery has different character (pH) at different stages of the tanning process. The chrome liquor (discharged during chrome tanning process) has pH of about 3.5 to 4.0 while the lime liquor (discharged during lime tanning process) has pH of about 11 to 13. Neutralization of these liquors through mixing with each other results precipitation of chromium which was removed by simple filtration. Neutralized liquor was found to have chromium content 2 ppm while the original chrome liquor had 3600 ppm.