Abstract

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The present work evaluates the potentials of using indigenous microbial strains isolated from wastewaters of an effluent treatment plant of a Textile Industry and the feasibility of employing nanofiltration (NF) membrane and reverse osmosis (RO) systems as an alternative treatment method of textile wastewater discharged from textile industry. Experiments were performed in a laboratory - scale set up using four potential candidates’ microbial strains, in which the bacterial strains (Pseudomonas monteilii and Aeromonas hydrophila) and the fungal strains (Phanerochaete chrysosporium and Aspergillus oryzae) were selected based on their ability to decolorize and degrade dyes effluent into non-toxic form. Decolorization efficiencies of the microbial strains were measured as a function of the operational parameters (aeration, dye concentration, pH, temperature, total viable count and optical density) and the microbial isolates showed increase in cell number as the concentration, absorbance and pH decreases. The effects of dye concentration, pH of solution, feed temperature, dissolved salts and operating pressure on permeate flux and dye rejection were studied using the membrane technologies. Results at operating conditions of dye concentration of 60 mg/L, feed temperature of 38 °C and pressure at 8.5 bar showed the final dye removal with NF membrane as 97.3 %, 99.1 % and 98.9 % for organic dyes, Congo red and Direct blue 80, respectively. While with RO membrane, the final dye removals were 97.5 %, 97.7 %, and 98.6 % for organic dyes, Congo red and Direct blue 80 dyes, respectively. Higher color removal was achieved due to the existence of NaCl salt in the solution. It was later confirmed that pH of solution also had a positive impact on dye removal. A comparison was made between the results of dye decolorization in microbial and membrane methods and it was found that the use of membrane technologies in dye removal from the effluent of textiles industry was highly effective and promising

Keywords: Decolorization, microbial strains, nanofiltration, reverse osmosis, textile effluent