ULTRAVIOLET DISINFECTION OF WASTE-WATER - EFFECT OF DOSE ON SUBSEQUENT PHOTOREACTIVATION

The objective of this research was to examine the significance of phot oreactivation of total coliform for u.v. disinfected secondary effluen t. An appropriate methodology for quantifying photoreactivation was id entified. Photoreactivation was evaluated in relation to u.v. dose, ex posure to photoreactivating light and various water quality parameters . An increase in u.v. dose is extremely valuable in minimizing photore activation events. A significant inverse relationship was found betwee n average u.v. dose and photoreactivation of coliform in wastewater at both low and high u.v. doses. Increased levels of suspended solids ha d the effect of reducing the true u.v. dose reaching targeted organism s, thus reducing DNA damage and increasing subsequent photoreactivatio n. The dose of photoreactivating light was also observed to be an impo rtant parameter in the reactivating process.