It is IAA’s philosophy that solids or sludge should not be entrapped/accumulated in a RAS. This is among other things to avoid having to backwash filters, but equally as much the uncertainty of certain potentially undesirable biological processes that may take place in a sludge laden environment. For this reason, we emphasize on mechanical solids removal using drum filters.
Drum filters are designed with the purpose of removing solids and they do it very well. The sludge is flushed of the mesh and is instantly out of the system. Efficiency has improved in recent years with better and better mesh materials.
Drum filters have though limitations with removal of particles below 30-40 microns. In cases where further particle removal is required, IAA emphasize to do this on a side stream of the water flow. Then we still achieve to keep the processes in a RAS separate and controllable. Depending on application, there are a number of options for fine particulate matter removal on side stream.