ULTRAVIOLET DISINFECTION OF FILTERED ACTIVATED-SLUDGE EFFLUENT FOR REUSE APPLICATIONS

An ultraviolet (UV) disinfection system was assessed in terms of the m ost stringent U.S. wastewater reuse standards. The UV inactivation of total and fecal coliform bacteria and seeded MS2 coliphages in filtere d activated sludge effluent was tested continuously for 22 weeks. The most stringent coliform criterion, that the 7-day median not exceed 2. 2 per 100 mL was met consistently in effluent exposed to an average UV dose of 168 and 112 mW/cm(2) . s for total and fecal coliforms, respe ctively. MS2 coliphages were more resistant to UV disinfection than th e coliform group. Both the point source summation (PSS) and bioassay m ethods were used to estimate UV dose in the system. For a 95% confiden ce interval, the PSS method resulted in an equivalent estimate of UV d ose when compared with the bioassay method.