Decoloration and Treatment of Azo Dyes Contaminated Waste Water Using Lab Scale Constructed Wetlands (P-0797) (MFN 5514)

Abstract

zo reactive Dyes contaminated textile effluents possess serious threats to aquatic as well as terrestrial environment. Since these dyes are strong carcinogenic in nature, their bioaccumulation and bio magnifications causes severe adverse effects on exposed mechanisms. In Pakistan, existence of textile waste water treatment facilities for removal of these dyes is very rare. The objective of the present study was to examine the treatment efficiency of lab scaled constructed wetlands for dye rich textile waste water with special emphasis on decoloration and COD reduction. The dyes used were Azo reactive dye Red, Azo reactive dye Blue and Azo reactive dye Yellow. A series of experiment were conducted using vertical flow CW packed with layers of gravel, sand and soil of 5 inches each. 5% of 1000ppm dye solution was used to prepare synthetic waste water to be treated in CW. To evaluate the efficiency of our constructed wetlands, waste water parameters like pH, EC, TDS, UV and COD were analysed before and after treatment. A separate experiment was conducted in a similar fashion but with a addition of three commonly available low cost plants to find out the effect of phytoremediation in constructed wetlands. The efficiency of wetlands was also evaluated to investigate the effect of retention time on waste water treatment. Decoloration and COD removal of individual dye was observed in each of the three constructed wetlands. For effect of phytoremediation, a mixture of dyes was used containing 5% solution of each dye. The obtained results evidence that the CW were able to reduce pH from 9.3 to 7.10 in case of Azo reactive dye Blue. pH was reduced to 8.4 to 7 and from 8.8 to 7.1 in case of red and yellow dyes. Electrical conductivity was reduced from 1.8 to 1.61, 1.74 to 1.36 and 1.64 to 1.33 in case of Blue, Red and Yellow dyes. Total dissolved Solids were reduced from 1240 to 1110, 1200 to 930 and 1130 to 910. Decoloration was calculated by measuring absorbance at 430 nm in UV spectrophometer. CW showed decoloration efficiency of 77%, 88% and 90% for Blue, Red and Yellow dyes. COD removal efficiency was calculated to 33.23%, 65.29% and 70.4% for Blue, Red and yellow dyes.in case of phytoremediation experiments, pH was reduced from 7.5 to 7.2 in case of Money plant and common grass whereas from 7.5 to 6.6 in case of Korean grass. Electrical conductivity was increased from 0.9 to 1.78 incase of Money plant and 1.74 when treated with common grass and Korean grass. TDS was increased from 630 to 1220 incase of ii money plant and 1200 when treated when common grass and Korean grass. color reduction efficiency was observed to be 93.97%, 94% and 95% when treated with money plant, common grass and Korean grass. Reduction efficiency of COD was calculated to be 56.68%, 57.54% and 29.89% when treated with money plant, common grass and Korean grass. Maximumdecoloration and waste water treatment occur when 5 days of retention time was provided for waste water treatment. The results indicate that using simple constructed wetlands with or without use of plants can provide an efficient and cost effective method for treatment of Azo dyes contaminated textile waste water.