Side-By-Side Pilot Testing of Two Disk Filter Manufacturers at the City of Merced Wastewater Treatment Plant

As more wastewater treatment facilities upgrade to tertiary treatment for pathogen removal and trace pollutant reduction, the options for tertiary filtration expand. The use of cloth-disk media filtration (disk filters) for tertiary filtration is becoming more common because of the effluent quality, lower backwash rates, small footprint, and ability to meet California Department of Health Services Title 22 criteria for the unrestricted reuse of treated effluent. Two manufacturers currently have Title 22 approval, the Aqua Aerobic AquaDisk and the Kruger Hydrotech Discfilter.Relative performance of disk filter technology can vary depending on the site-specific characteristics of the secondary treated wastewater used as the influent to the disk filters. Pilot testing of the two Title 22 approved disk filter manufacturers was performed concurrently to determine the filter best suited for the specific conditions at the City of Merced Wastewater Treatment Plant (WWTP). Side-by-side piloting included several logistical challenges, but allowed the use of the same procedures, on the same source water, and a direct comparison of testing results. The suitability of each filter technology at Merced was determined based on quantification of the filter operating characteristics and evaluation of filter reliability and performance based on varying influent quality, loading rate, and chemical dose rates. This testing then allowed for a more specific determination of design criteria for the filters.