UV Process and Fouling Testing at a Trickling Filter Plant: Key Factors in UV Design for Trickling Filter Effluent

The use of ultraviolet (UV) light for disinfection for trickling filter effluent is traditionally difficult. The City of Olathe, Kansas, however, has been successfully using ultraviolet (UV) light at a trickling filter facility for over 20 years to disinfect wastewater effluent. The Olathe system was one of the first low pressure/low intensity UV systems installed in the state of Kansas. The existing Harold Street WWTP UV disinfection system, however, requires frequent manual cleaning to continue to meet effluent disinfection requirements. The labor associated with the cleaning activities significantly increases operation and maintenance costs when compared to current technologies. In order to establish design parameters and to compare potential new systems, a multi-phase pilot study was conducted. Two pilot-scale UV systems were tested at the treatment plant to compare the extent of fouling of their quartz sleeves. The pilot testing included a multi-phase process to establish the operation and maintenance requirements for each system. The first phase of the testing was conducted to validate the performance of the pilot system. The second phase of testing was to conduct a fouling study. Results of the study indicated that after one week the sleeve transmittance was close to zero percent. The results of the fouling study were used to determine projected cleaning requirements for the new UV system. A baseline condition was established to allow a comparison to be made after new equipment is installed.