The Effectiveness of UV Disinfection of a WPCP Secondary Effluent with High Levels of Iron at Pilot Scale

Ultraviolet (UV) disinfection using low pressure high output (LPHO) lamps was an alternative to chlorination investigated to treat the secondary effluent at the Duffin Creek Water Pollution Control Plant (WPCP) in Pickering, Ontario, Canada. A pilot study was conducted with two different UV systems in parallel in order to confirm the feasibility and requirements for the design of the disinfection system.Based on the pilot test data, it is evident that a UV dose up to 50 mJ/cm2 is required to meet the design objective of 100 E. coli counts/100 mL and provide a factor of safety. This result was verified by collimated beam tests conducted throughout the study period using secondary effluent.The results of this study are unique due to the high levels of iron present in the secondary effluent (approximately 6 % of the TSS) and the side by side comparison of the cleaning efficiency of two different UV pilot systems treating the same secondary effluent.