ABSTRACT
Ultraviolet (UV) light is a valuable alternative for disinfection of treated wastewater, because it forms no or very low levels of disinfection by-products. Among the negatives of the method that have been considered is the potential reactivation of organisms after exposure, whether or not in relation to shielding of organisms by suspended solids. At present, no general rules exist for the necessary (high) UV doses that could promote formation of by-products. Pilot investigations are advisable for each particular case. The potential toxicity of the treated effluent must be evaluated.
