Investigation of Environmental Problems Caused by Dyeing Effluent with Natural Dyes

One of the main and essential problems in the dyeing units of the textile industry is the volume of pollutants produced, which has endangered the health of the environment through ground water pollution. Despite not causing respiratory and skin allergies and good compatibility with humans and nature, natural dyes can cause environmental problems by creating effluents. The resulting dyeing effluents often contain metal ions and colored compounds that can be harmful to the health of organisms and cause various diseases. Usually, different natural dyes such as madder, weld, walnut shell, and cochineal are used with different concentrations during the dyeing process. Besides, along with pre, simultaneous and post-mordanting methods, various mordants such as aluminum sulfate, copper sulfate, and potassium dichromate are applied. In this research, a review study has been conducted on the effect of using these dyes, types of applied mordant, and different dyeing methods on parameters such as BOD, COD, and TDS of resulted effluents.