Microscreen Filter

A microscreen filter is a rotating drum or belt covered with a fine mesh, typically 20–120 microns, through which RAS water flows from inside to out, depositing solids on the screen until a rising water level triggers a backwash spray that flushes the captured material to a sludge trough. Drum screens are rated by filtration area and design flow, with hydraulic loading commonly 10–30 m3/m2/hour depending on fish density and feeding rate. Sizing rule of thumb is roughly 0.5–1 m2 of screen per m3/h of flow for grow-out systems. Finer screens capture more solids but backwash more often and use more water, typically 0.5–2% of system flow per day. The microscreen is usually the first treatment step after the fish tank outlet, positioned before the biofilter so that feces and uneaten feed are removed before they dissolve and raise the dissolved load. Properly sized units keep TSS below 10–15 mg/L in the culture tanks, protecting fish gills and downstream components. Automatic control by water-level differential rather than timers materially improves capture efficiency and reduces screen wear.