Abstract
Important pollutants in textile effluents are mainly recalcitrant organics, colours, toxicants and inhibitory compounds, surfactants, chlorinated compounds (AOX), pH and salts. An aerobic system using a continuous stirred bed reactor (SBR) was continuously operated at constant temperature and fed with textile wastewater (pH 7 and total chemical oxygen demand (COD) 1 700 mg/l).This report is focused on the decolourisation treatment of effluent by a bacterial consortium (Sphingomonas paucimobilis, Bacillus sp. and filamentous bacteria). The influence of the different mixtures of 3 strains on the decolourisation of effluent (cell density fixed at OD600 = 1) was studied using an equilateral triangle diagram and mixture experimental design to assess colour and COD removal during species evolution. With the aid of analysis software (Minitab 14.0), the formulation of pure culture was optimised for several responses and the best formulation obtained. The results suggested that the highest predictable specific decolourisation rate and chemical oxygen demand (COD) were 86.72% and 75.06%, respectively. Regression coefficients between the variables and the responses of decolourisation and COD removal were, respectively, R2 = 72.48% and 54.28%, which indicated excellent evaluation of experimental data by the polynomial regression model. UV-visible analysis confirmed biodegradation of effluent. Keywords : textile wastewater, bacterial decolourisation, response surface, mixture design, SBR
Highlights
Textile industries consume a considerable amount of water in their manufacturing processes
Among low-cost, viable alternatives available for effluent treatment and decolourisation, the biological systems are recognised by their capacity to reduce biochemical oxygen demand (BOD) and chemical oxygen demand (COD) by conventional aerobic biodegradation
The effect of the change of variables on the responses can be observed on the ternary contour map
Summary
Textile industries consume a considerable amount of water in their manufacturing processes. Some reports showed that the effluent of the anaerobic decolourisation process was completely non-toxic (Flores et al, 1997). Another problem with anaerobic colour removal is the reverse colourisation of anaerobic degradation products upon exposure to oxygen. This could be because of unstable characteristics of biodegradation products, aromatic amines, which deteriorate to give colour (Knapp and Newby, 1995; Chinwetkitvanish et al, 2000)
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