Effect of oxygen injection in a reclaimed wastewater pipeline on the microbiological quality of water

• Published in: Environmental technology 2012-03, Vol.33 (5), p.497-505
• Main Authors: Acosta, N. Abreu, Rodríguez Gómez, L. E, Díaz, M. Álvarez
• Format: Article
• Language: English
• Subjects: Applied sciences; biofilm; Bioreactors - microbiology; coliform bacteria; coliphages; Conservation of Natural Resources - methods; disinfection; Drinking water and swimming-pool water. Desalination; Enterococcus; environmental technology; Escherichia coli; Exact sciences and technology; General purification processes; gravity; Inactivation; Industrial Waste - prevention & control; microbiological indicators; microbiological quality; Microorganisms; organic matter; oxygen; Oxygen - pharmacology; oxygen consumption; oxygen injection; Pipe; Pipelines; Pollution; regrowth; Transportation; Waste water; wastewater; Wastewaters; Water Microbiology; Water Purification - methods; water quality; water reuse; water transport; Water treatment and pollution
• ISSN: 1479-487X; 0959-3330; 1479-487X
• DOI: 10.1080/09593330.2011.581312

In this work the influence of oxygen injection on the inactivation of microbiological indicators during reclaimed wastewater transportation was studied. Experiments were carried out in a completely filled gravity pipe (62 km long), at two different periods of the year and with three different oxygen doses (7, 15 and 30 mg L⁻¹). Microbiological parameters studied were faecal coliforms, Escherichia coli, enterococci and somatic coliphages. As a consequence of the oxygen injection, a significant inactivation of the microbiological parameters was observed during the aerobic stretch of the pipe. Later, once the oxygen had been consumed, inactivation stopped and even a slight regrowth of the microbial population took place. Inactivations were within the range of 0.6–1.0 log₁₀ units, in most cases. No significant differences between inactivations for the different microbiological parameters were found, except for the somatic coliphages. A relationship between the inactivation degree and oxygen dose and organic matter content was observed. The biofilm played an important role in the inactivation process. The injection of oxygen contributes to improving the microbiological quality of reclaimed wastewater during its transport by pipelines, helping to diminish the subsequent on-site disinfection requirements.