Abstract
Among the industries generating hyper saline effluents, tanneries are prominent in India. Hyper saline wastewater is difficult to treat by conventional biological treatment methods. Salt-tolerant microbes can adapt to these conditions and degrade the organics in hyper saline wastewater. In this study, the performance of a bench scale aerobic sequencing batch reactor (SBR) was investigated to treat the tannery wastewater by the salt-tolerant bacterial strains namely Pseudomonas aeruginosa, Bacillus flexus, Exiguobacterium homiense and Styphylococcus aureus. The study was carried out under different operating conditions by changing the hydraulic retention time, organic loading rate and initial substrate concentration. From the results it was found that a maximum COD reduction of 90.4% and colour removal of 78.6% was attained. From this study it was found that the salt-tolerant microorganisms could improve the reduction efficiency of COD and colour of the tannery wastewater.
Highlights
Hyper saline effluents are generated by various industrial activities
Tannery wastewater was characterized by the parameters like biochemical oxygen demand (BOD), chemical oxygen demand (COD), suspended solids (SS), Total dissolved solids (TDS), chromium and sulfides etc
The COD and colour reduction profiles obtained during the degradation of tannery wastewater in a sequential batch reactor are shown in Figs. 2, 3, 4 and 5
Summary
Hyper saline effluents are generated by various industrial activities. Leather tanning is a wet process from which a large volume of highly saline liquid waste is continuously generated. The details of wastewater generated from tanneries and their characteristics have already been reported in various literatures (Wiegant et al 1999; Sreeram and Ramasami 2003; Durai and Rajasimman 2011). Rich in both organic matter and total dissolved solids (TDS), is difficult to treat using conventional biological wastewater treatment processes. Major problems encountered in biological treatment were (1) a limited extent of adaptation, as conventional cultures could not be effectively used to treat saline wastewaters of values higher than 3–5% (w/v) salt (2) salt adaptations of cultures were lost when subjected to salt-free medium (3) changes in ionic strength cell disruptions due to shifts in salt concentration, from 0.5 to 2% (w/v), caused significant reductions in system performance (Glass and Silverstein 1999) and (4) rapid changes in salt concentrations created adverse effects more than gradual changes
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