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New Filter Optimization Guidance Article in AWWA Opflow

(NEW YORK, NY - November 30, 2023) - Granular media filters are one of the most important tools in water treatment. While they may appear to be simple strainers at first glance, they actually rely on a combination of physical and chemical processes to capture particles, disease-causing pathogens, and other harmful contaminants. By better understanding how these filters work, facility operators will be empowered to get the most out of their filters, extending their useful life and their effectiveness.

To help inform facility staff and share crucial operational tips, Hazen’s Matt Charles recently wrote an article titled “Optimize Granular Media Filtration” published in AWWA’s Opflow.

Filters capture particles in three ways – sedimentation, interception, and diffusion. All three of these capture methods require the proper conditioning of both the particles and the filter media. Poor filtration is most often the result of poor particle conditioning, which can be resolved by adjusting upstream pretreatment. While backwashing is important to keep the filters functional, floc accumulated on filters helps remove other particles, so it is possible for a filter to get too clean and perform poorly due to over washing.

Proper conditioning of the particles in pretreatment and optimizing the backwash process can minimize peak turbidity and filter ripening time, increasing the efficiency of the filters and extending their runtimes. Other considerations include avoiding sudden changes in filter flow, resting filters for short periods, and implementing filter surveillance.

The article also details Uniform Filter Run Volume (UFRV), a filter evaluation parameter used to compare performance regardless of flow rate and provides guidance for ideal UFRV rates. The full article is available for free on the Opflow website.

AWWA Magazine Graphics Figure 5

Although many variations in exact construction are possible, granular media filters typically contain several key elements, pictured here.