This project has examined the effect of three potential disinfection methods, namely, ozonation, UV irradiation and microfiltration, on the removal of E. coli and total coliforms from a typical secondary municipal effluent. The changes in TOC, colour, absorbance at 254 nm. and toxicity were also examined. With the ozonation treatment the removal of microorganisms was also studied under variable ozonation conditions. All of the methods were successful in removing the microorganisms under study. Of the three methods, only ozonation and microfiltration improved the general quality of the effluent in that they also removed part of the organic matter. The untreated secondary effluent was not toxic, and none of the examined methods added toxicity to the effluent. For the different ozonation conditions, the most important treatment parameter was the transferred ozone dose and not the contact time. Consequently, the use of higher ozonation rates could accelerate the disinfection process and lead to smaller scale contacting systems.