Abstract
BackgroundHigh salinity (1–10% w/v) of tannery wastewater makes it difficult to be treated by conventional biological treatment. Salt tolerant microbes can adapt to these saline conditions and degrade the organics in saline wastewater.ResultsFour salt tolerant bacterial strains isolated from marine and tannery saline wastewater samples were identified as Pseudomonas aeruginosa, Bacillus flexus, Exiguobacterium homiense and Staphylococcus aureus. Growth factors of the identified strains were optimized. Tannery saline wastewater obtained from a Common Effluent Treatment Plant (CETP) near Chennai (southern India) was treated with pure and mixed consortia of four salt tolerant bacterial strains. Experiments with optimized conditions and varying salt content (between 2 and 10% (w/v) were conducted. Salt inhibition effects on COD removal rate were noted. Comparative analysis was made by treating the tannery saline wastewater with activated sludge obtained from CETP and with natural habitat microbes present in raw tannery saline wastewater.ConclusionSalt tolerant bacterial mixed consortia showed appreciable biodegradation at all saline concentrations (2%, 4%, 6%, 8% and 10% w/v) with 80% COD reduction in particular at 8% salinity level the consortia could be used as suitable working cultures for tannery saline wastewater treatment.
Highlights
High salinity (1–10% w/v) of tannery wastewater makes it difficult to be treated by conventional biological treatment
Biochemical analysis and 16s rRNA analysis of the isolated salt tolerant bacterial colonies helped to identify them as Pseudomonas aeruginosa, Bacillus flexus, Exiguobacterium homiense and Staphylococcus aureus
The non-sterilized tannery saline wastewater samples were taken separately and the efficiency of Chemical Oxygen Demand (COD) removal by Growth optimization Optimization experiments were performed for the growth of halotolerant bacterial isolates at shaker level to determine the growth factors simulating higher biomass yield
Summary
High salinity (1–10% w/v) of tannery wastewater makes it difficult to be treated by conventional biological treatment. Salt tolerant microbes can adapt to these saline conditions and degrade the organics in saline wastewater. A primary effluent stream in leather processing industry is generated by soaking the salt-laden hides and skins in fresh water to remove excess salt. The presence of high salinity (1–10% NaCl by wt) in this waste stream hinders treatment by biological means [1]. A biomass sludge adapting to varying saline concentrations (salt tolerant strains) is required to degrade the dissolved organics present in tannery saline wastewater. Kargi and Dincer treated waste waters rich in halogenated organics at different salt concentrations and showed COD removal decreased with increasing salt concentration [7]. Woolard and Irvine studied the treatment of hypersaline wastewater by a moderate halophile in a sequencing batch reactor (page number not for citation purposes)
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