Optimizacion del proceso de desinfeccion de aguas residuales depuradas mediante radiacion ultravioleta

Two ultraviolet (UV) disinfection systems were pilot tested at the Wastewater Treatment Plant in Jerez de la Frontera City (Spain). Both units were operated using unfiltered secondary wastewater effluents to assess the viability of using UV light to meet the municipal and tourist/recreational reuse criterion suggested by the Andalusia Regional Government (ARG). The ARG criterion that the 95% samples not exceed 200 faecal colifoms per 100 mL was met in unfiltered effluent exposed to an average UV dose of 75 mW·s/cm 2 or greater. Besides this condition, Aguas de Jerez, Empresa Municipal, S.A. (AJEMSA) suggested two new criterions: the 95% sample not exceed 1.000 total coliforms per 100 mL and the 95% sample not exceed 200 faecal streptococcus per 100 mL. These criterions was met in unfiltered effluent exposed to an average UV dose of 75 mW·s/cm2 or greater. The effective UV dose for indicator bacteria (total coliforms, faecal coliforms and faecal streptococcus) removal and the feedwater quality characteristics were examined too. Results indicated that the UV light causes a logarithmic decrease higher than 3,2 units, which is the equivalent of nearly a 99,99 percent decrease. The quality of the unfiltered wastewater shows that turbidity and total suspended solids could serve as a good indicator for UV transmittance variations.;Finally, photoreactivation and dark reactivation of microorganisms following UV disinfection was examined too. Results indicated that the dark reactivation and the photoreactivation by both fluorescent lamps and sunlight may be important in the reuse of UV disinfected wastewater.