ABSTRACT
Reactive dyestuff has potential of toxicity, carcinogenesis and mutagenesis for mammals and aquatic organisms. The current physical and chemical methods such as adsorption, coagulation, precipitation, filtration and. can been used for removing of dyestuff. Biological treatment which is effective and economic for decontamination of dyestuff wastewaters was preferred because of limitation and difficulty of physicochemical methods. In order to investigate the trend of pollution reduction of color compounds, ability of Remazol Black-B dyestuff removal from aqueous medium by bacterial consortium under anoxic conditions was studied. The mix culture of bacteria from textile industries activated sludge was enriched in luria broth medium containing RB-B dyestuff as a carbon source. Then biodegradation was assessed in 4 batch reactors. Microbial population of bacterial and decolorization quantities of samples were detected by MPN and UV-Vis spectrophotometer. Decolorization efficiency by the bacterial consortium was obtained more than 99% for 50 and 250 mg/L concentrations in 72 and 144 h [3 and 6 days] respectively, while for the initial concentration of 500 mg/L was 98.1in 240 h [10 days] of biodegradation period. Dyestuff reduction rate after completed removal was about 0.69, 1.74,2 mg/L/h for initial concentration of 50, 250, 500 mg/L respectively. Results showed that Alcaligenes denitrificans and Alcaligenes xylosoxidans bacteria which were isolated from activated sludge have good potential of RB-B dyestuff removal and this removal is depending on primary concentration of dye. Removal efficiency increased as primary concentration went up
ABSTRACT
PACT is an adsorption- degradation process through which slowly or non-biodegradable waste water compounds such as dye can be degraded. This study was carried out to evaluate the efficacy of PACT in removal of dyes form textile industry wastewaters. This research was carried out in pilot scale. The pilot design had two parts: an aeration tank with 40L volume and a clarifier with 12L volume. The dyes used in this research were acid and reactive dyes in different concentrations which are mostly used in textile industries. First, the biodegradability of the dye was studied through Zahen-Wellens method [ISO 9888, 1999]. Then, dye removal efficiency in different conditions of powdered-activated carbon concentration and operational conditions were evaluated. American Dye Manufacture Institute [ADMI] method was utilized for determination of dye removal in samples. Biodegradability of acid dyes and basic dyes in 100 mg/L dye concentration, were 60 and 80% respectively. On the other hand, the best efficiency for application of PAC in activated sludge process, was obtained in 1500 mg/L PAC concentration. In this situation, with 30 hydraulic retention time, and 30§C temperature, the rejection percent of dye was 98.8%. PACT process could be the best method for removal of different dyes used in textile industry with high efficiency [up to 90%]. Application of this method in treatment of textile wastewaters is an important economic improvement, which in a single step, allows the removal of COD and color from textile wastewater without additional physicochemical treatment