Decolorization of low-volume colored wastewater

The hand-made textile weaving industry of Thailand is a small-scale industry, comprised of groups of local villagers around the country. These villagers, mostly farmers, form cooperatives that they themselves own and operate. Individually, these cottage industries produce small volumes of colored wastewater, creating little pollution. Collectively, being scattered through the country, they create widespread contamination to their own water resources by colored dyestuffs. For local villagers, conventional treatment technologies are too costly to bear and too complicated to handle. The purpose of this research is to find a suitable treatment method for decolorizing lowvolume wastewater generated from these villages The potential of water hyacinth powder (WH) and wood charcoal (WC) to remove five cotton dyes (Black, Blue-1, Blue-2, Red-1 and Red-2) from aqueous solution were evaluated. Their effectiveness was compared to commercial granular activated carbon (AC). Studies of the effects of contact time and initial pH on adsorption capacity were conducted. Equilibrium conditions of dye adsorption were studied using the Langmuir isotherms. A large fraction of the dye was removed during the first 60 minutes, the removal rate decreasing markedly thereafter. The equilibrium adsorption by AC, WC and WH occurred after 24, 3 and 10 hours of contact time. The adsorption of all dyes by WH, WC and AC were pH independent over a pH range of 4.0 to 10. The Langmuir adsorption isotherms were found to conform to all adsorption systems. The dye adsorption capacity followed the order WH > > AC > WC. The costs of WH, WC and AC to treat a batch of 200 liters of single-dye wastewaters, containing an initial dye concentration of I 00mg (.) L (-1), to achieve a final effluent concentration of 100mg (.) L-1 were calculated and compared.