Inactivation of Escherichia coli in photobioreactors with microalgae and illuminated by light emitting diodes.

Abstract

Pathogens in wastewater must be inactivated to prevent the spread of waterborne diseases and allow reuse of the water after treatment. One of the options for wastewater treatment is to use photobioreactors with microalgae. Such systems can inactivate pathogens by diferent mechanisms, and Escherichia coli can be used as an indicator of inactivation. Therefore, this study aimed to evaluate inactivation of E. coli in wastewater by means of light emitting diodes (LED)-illuminated photobioreactors with microalgae, without the emission of ultraviolet radiation (UV). Two optimization steps were carried out, in which LED-illuminated photobioreactors without UV emission were set up for the treatment of wastewater, and various exposure times and luminous fuxes were tested for three wavelengths (white, blue and red); they were compared with photobioreactors illuminated by sunlight and in the dark. Additionally, using the results obtained in the optimization, a scaled-up reactor approximately 8.5 times larger in volume was operated to evaluate whether the behavior would be maintained at this scale. The removal efciency was 5.06 logarithmic units. Photobioreactors illuminated with a blue LED with luminous fux of 700 µmol m−2 s −1 and operated for 15 days showed the best performance in the inactivation of E. coli. LED-illuminated photobioreactors with microalgae, without the emission of ultraviolet radiation (UV) presents inactivation of pathogens and has the advantage of the low cost of the lamps, and the ease of operation.