The major issue with the dye discharged in the water is its concentration. As low concentration also has significant color in water. The major statics while release of color into effluent varies from process to process and industry to industry. So, in view of same issue, what should be the range of synthetic dye wastewater can be used for studying dye removal.
Further, Idea behind this question is if all researchers use a specified dye concentration the results using different dyes and also process can be easy to correlate and we can opt for better process for particular dye.