The presence of mudballs is an indication of problems in your filter bed. A mudball is the result of solids accumulating in a filter, then combine with filter media to form into a ball of solids. These mudballs block the passage of water, creating higher velocity filtration and uneven distribution. Mudballs impact filter performance and effluent quality while also shortening filter run lengths.
If media is inadequately backwashed, thin layers of solids will coat and build up around individual media grains. During operation, an increase in pressure drop across the media bed compresses the particles, causing them to stick together. Polymer and other sticky agents will accelerate growth. As mudballs grow, they sink down into the media bed, eventually stopping at the support gravel.
Large mudball build-up
Mudballs can also form in filter dead zones, defined as any area that is not covered during conventional backwash. When mudballs achieve critical mass and hydro-dynamic shape, they are unable to be backwashed out of a filter.
A simultaneous air and water backwash is recommended in media filters to prevent the formation of mudballs. By simultaneously applying air and water at a sub-fluidized rate, an aggressive scouring action occurs known as collapse pulse. This powerful backwash method creates the momentary formation of air pockets where media collapses, causing a pulsation within the bed that aggressively scours and cleans the media. During a sustained air and water wash, a dual media bed will completely intermix into one homogeneous depth of media. This provides the most effective media cleansing, ensuring that the entire filter bed is washed, eliminating all dead zones and preventing the formation of mudballs.
U.S. Water offers a simultaneous air and water backwash process known as Simul-Wash™. Need assistance with existing mudballs or have additional questions? Learn more about our Simul-Wash™ system by contacting us today.
U.S. Water’s Performance Index series is designed to share operations and maintenance best practices with plant personnel. The more our customers know about how to maintain and protect their systems, the more they can safeguard against system failures or efficiency issues.