Critical aspects for the wider application of ultraviolet (UV) light in drinking water treatment sometimes have been described, in spite of the success of the method as established in the field: • Absence of well-established and generally accepted design rules • Absence of a permanently active residual agent in the treated water • Suspicions of the possible photochemical formation of by-products • Possibility of revival–reactivation by repair mechanisms of irradiated organisms • Need for operational control of the permanent reliability of the technique.
