Shock effects of monovalent cationic salts on seawater cultivated granular sludge

• Published in: Journal of hazardous materials 2021-02, Vol.403, p.123646-123646, Article 123646
• Main Authors: Sivasubramanian, Raghavendran, Chen, Guang-hao, Mackey, Hamish Robert
• Format: Article
• Language: English
• Subjects: Aerobiosis; Biological wastewater treatment; Bioreactors; Cations, Monovalent; Extracellular polymeric substances; Morphology; Salinity; Salts; Seawater; Seawater cultivation; Sewage; Waste Disposal, Fluid
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2020.123646

[Display omitted] •Aerobic granules cultivated on seawater then 0.8 M mixed-salts (NaCl, Na2SO4, KCl).•Change to 0.8 M single salt solutions caused drastic changes in sludge morphology.•KCl and Na2SO4 reactors had greater changes in morphology and treatment.•Tonicity deemed important for cell viability and treatment performance.•Ionic strength changes important for EPS and hydrophobicity changes. Saline wastewater is commonly encountered in various industries, posing challenges to biological treatments. The application of seawater as a seed source provides a media of diverse halophilic organisms for rapid startup. However, effects of transitioning from a mixed salt source to monovalent salt solutions prevalent in industry remains unexplored. Hence, seed sludge was cultivated using seawater and later granulated under a mixed-salt synthetic medium comprising a mixture of NaCl, KCl and Na2SO4 at a combined concentration of 0.8 M (0.27 M each). The stable, acclimated granules were then tested against single salt media of 0.8 M NaCl, KCl, or Na2SO4. Shift to single salt media resulted in granule disaggregation, poor settling, sludge washout and development of fluffy or slimy flocs. Changes in exopolysaccharides composition after the single salt shift was the predominant reason for the large changes in sludge morphology. The impacts of KCl and Na2SO4 were more significant than the shift to NaCl. The resulting impacts also had a major influence on the treatment performance. A complex mechanism involving monovalent cation stimulation of proteins; ionic strength impacts on exopolysaccharides and morphology; solution density influence on sludge density and settling; and tonicity impacts on cell viability and treatment is described.