ON-SITE COLLIMATED UV BEAM TESTING OF SECONDARY AND BLENDED EFFLUENT

The City of Winnipeg is required to install disinfection equipment at its largest wastewater treatment plant, the North End Water Pollution Control Centre. The preferred method of disinfection is by ultraviolet light. At high flows the performance of the secondary clarifiers is poor and also primary effluent is blended with secondary effluent. To ascertain the efficacy of UV disinfection a large number of bench-top collimated beam tests were undertaken. The results from the collimated beam tests indicated that UV disinfection of secondary effluent would be effective during dry weather conditions only. During wet weather conditions, it would be difficult to meet the disinfection standard, whether disinfecting only secondary effluent or a blend of primary and secondary effluent. The extensive collimated beam test results have provided the engineers with excellent data for designing the full-scale UV disinfection facility. The test results have demonstrated the difficulty of disinfecting wet weather flow and have provided the City with data to support their application for some relaxation of the permit limits during wet weather flow.