Azo dyes are among the oldest man made chemicals and they are still widely used in the textile, printing and the food industries. About 10%-15% of the total dyes used in the industry is released into the environment ...Azo dyes are among the oldest man made chemicals and they are still widely used in the textile, printing and the food industries. About 10%-15% of the total dyes used in the industry is released into the environment during the manufacturing and usage. Some dyes and some of their N substituted aromatic bio transformation products are toxic and/or carcinogenic and therefore these dyes are considered to be environmental pollutants and health hazards. These azo dyes are degraded by physico chemical and biological methods. Of these, biological methods are considered to be the most economical and efficient. In this work, attempts were made to degrade these dyes aerobically. The organisms which were efficient in degrading the following azo dyes Red RB, Remazol Red, Remazol Blue, Remazol Violet, Remazol Yellow, Golden Yellow, Remazol Orange, Remazol Black were isolated from three different sources viz., wastewater treatment plant, paper mill effluent treatment plant and tannery wastewater treatment plant. The efficiency of azo dye degradation by mixed cultures from each source was analyzed. It was found that mixed cultures from tannery treatment plant worked efficiently in decolorizing Remazol Red, Remazol Orange, Remazol Blue and Remazol Violet, while mixed cultures from the paper mill effluent worked efficiently in decolorizing Red RB, Golden Yellow and Remazol Yellow. The mixed cultures from wastewater treatment plant efficiently decolorized Remazol Black.展开更多
Toxicity characteristic leaching procedure(TCLP) of zinc plating sludge was carried out to assess the leaching potential of the sludge and the leachates were analyzed for heavy metals. The concentration of zinc, chrom...Toxicity characteristic leaching procedure(TCLP) of zinc plating sludge was carried out to assess the leaching potential of the sludge and the leachates were analyzed for heavy metals. The concentration of zinc, chromium, and lead in the leachate were 371 5 mg/L, 1 95 mg/L and 1 99 mg/L respectively Solidification of zinc sludge was carried out using four different binder systems consisting of cement mortar, fly ash, clay and lime and cured for 28 d. The ratio of sludge added varied from 60% to 80% by volume. The solidified products were tested for metal fixing efficiency and physical strength. It was observed that the volume of sludge added that resulted in maximum metal stabilization was 60% for all the combinations, above which the metal fixation efficiency decreased resulting in high values of zinc in the leachate. Addition of 5% sodium silicate enhanced the chemical fixation of metals in all the binder systems. Among the four fixing agents studied, mixture of fly ash: lime, and cement mortar: lime stabilized zinc and other metals in the sludge effectively than other combinations. Addition of lime increased the stabilization of zinc whereas cement mortar increased the strength of the solidified product.展开更多
文摘Azo dyes are among the oldest man made chemicals and they are still widely used in the textile, printing and the food industries. About 10%-15% of the total dyes used in the industry is released into the environment during the manufacturing and usage. Some dyes and some of their N substituted aromatic bio transformation products are toxic and/or carcinogenic and therefore these dyes are considered to be environmental pollutants and health hazards. These azo dyes are degraded by physico chemical and biological methods. Of these, biological methods are considered to be the most economical and efficient. In this work, attempts were made to degrade these dyes aerobically. The organisms which were efficient in degrading the following azo dyes Red RB, Remazol Red, Remazol Blue, Remazol Violet, Remazol Yellow, Golden Yellow, Remazol Orange, Remazol Black were isolated from three different sources viz., wastewater treatment plant, paper mill effluent treatment plant and tannery wastewater treatment plant. The efficiency of azo dye degradation by mixed cultures from each source was analyzed. It was found that mixed cultures from tannery treatment plant worked efficiently in decolorizing Remazol Red, Remazol Orange, Remazol Blue and Remazol Violet, while mixed cultures from the paper mill effluent worked efficiently in decolorizing Red RB, Golden Yellow and Remazol Yellow. The mixed cultures from wastewater treatment plant efficiently decolorized Remazol Black.
文摘Toxicity characteristic leaching procedure(TCLP) of zinc plating sludge was carried out to assess the leaching potential of the sludge and the leachates were analyzed for heavy metals. The concentration of zinc, chromium, and lead in the leachate were 371 5 mg/L, 1 95 mg/L and 1 99 mg/L respectively Solidification of zinc sludge was carried out using four different binder systems consisting of cement mortar, fly ash, clay and lime and cured for 28 d. The ratio of sludge added varied from 60% to 80% by volume. The solidified products were tested for metal fixing efficiency and physical strength. It was observed that the volume of sludge added that resulted in maximum metal stabilization was 60% for all the combinations, above which the metal fixation efficiency decreased resulting in high values of zinc in the leachate. Addition of 5% sodium silicate enhanced the chemical fixation of metals in all the binder systems. Among the four fixing agents studied, mixture of fly ash: lime, and cement mortar: lime stabilized zinc and other metals in the sludge effectively than other combinations. Addition of lime increased the stabilization of zinc whereas cement mortar increased the strength of the solidified product.
