Abstract
This paper investigated the effect of mixed cultures of Pseudomonas aureofaciens and Escherichia coli and air as gas on degradation of chemical oxygen demand (COD) in three-phase inverse fluidized beds (TPIFBs) for textile effluents with initial COD of 1200 ppm (effluent 1) and 640 ppm (effluent 2). Investigators focused on the importance of different design of gas spargers of the TPIFB for checking its effect on COD reduction performance. For this purpose, four different gas spargers were fabricated for gas flow entry into bioreactor with different % open area: Gas sparger 1 (18% open area), sparger 2 (10.42% open area), sparger 3 (8.077% open area) and sparger 4 (1.53% open area). These percentage open area decided the amount of gas flow in a unit time in batch studies, which in turn rely mainly on superficial gas velocity. The reduction in COD was measured at two different superficial gas velocity (0.00343 and 0.004068 m/s) and at two ratio of static bed height to diameter (H/D) of 0.5 and 0.25 in an aerobic mode. Textile effluent 1 resulted in 98.07% COD reduction with sparger 3 and discharged at 23.14 ppm in 28 h. Textile effluent 2 resulted in 96.5% COD reduction with sparger 2 and discharged at 22.4 ppm in 22 h. The resulting COD values of Effluent 1 and effluent 2 were in range of discharge limit and resulted at a low gas velocity of 0.00343 m/s and low H/D ratio of 0.25. The gas holdup correlation was found to be εg = 0.0064 Ug0.98.
Highlights
Textile industries produce considerable amounts of effluent with high chemical oxygen demand (COD), which is contributed by recalcitrant organics, toxicants, color and salts (Doble and Kumar 2008)
This paper investigated the effect of mixed cultures of Pseudomonas aureofaciens and Escherichia coli and air as gas on degradation of chemical oxygen demand (COD) in three-phase inverse fluidized beds (TPIFBs) for textile effluents with initial COD of 1200 ppm and 640 ppm
All the experimentations were accomplished at gas velocities of 0.004068 and 0.00343 m/ s and at the ratio of static bed height to diameter (H/D) of 0.5 and 0.25
Summary
Textile industries produce considerable amounts of effluent with high chemical oxygen demand (COD), which is contributed by recalcitrant organics, toxicants, color and salts (Doble and Kumar 2008). The presence of dyes in the effluent poses the biggest problem since they are recalcitrant and toxic. Two percent of dyes produced are discharged directly in the effluent (Doble and Kumar 2008). Characteristics of textile wastewater are reviewed and that indicated the initial COD for effluent from different processes ranges from 800 to 30,000 mg/mL (Correia et al 1994). Due to the presence of grease, dirt as well as nutrients from dye bath additives, the wastewater discharged from a dying process in textile industry is high in COD whereas the
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