الفهرس 
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Abstract
The present study proposes a new design of mechanical filter to suit the recirculating aquaculture system (RAS) as a high-efficiency alternative filter to the conventional swirl separator (CSS). The new filter is considered the developed version of CSS; thus, it is called thereafter as the swirl-vertical drum filter (SVDF) which is provided with a rotating vertical micro-screen drum equipped with a fixed vertical brush as a self-cleaning tool instead of the conventional backwash system. The performance of SVDF was evaluated under different drum rotational speeds, and drum rotation times using sinking and floating fish feed pellets and magnetic field device, and then, it was compared to CSS in terms of water quality and filtration efficiency under the same operational conditions. Experimental results showed better values of water quality including Dissolved oxygen (DO), pH and unionized ammonia (NH3). Also, the lowest value of COD was found to be 18.33 mg/L by using SVDF, whilst the highest value of 100.73 mg/L was found in the case of using the CSS. Also, SVDF showed values of TSS less than CSS 8.27±0.65-20.32±0.7 mg/L, Respectively. The obtained water quality parameters were in the appropriate levels for aquaculture. Meanwhile, the magnetic field device had no effect on the filtration process. The lowest surface area of the vertical micro-screen drum of 0.217±0.013 m2 was obtained at the drum’s rotational speed of 20 rpm (0.39 m/s), rotation time of 150 min with floating feed pellets. Experimentally, the filtration efficiency of SVDF was found to be 66.87%which was higher than those of CSS 28%. It is found that the new SVDF has higher filtration efficiency than the CSS by about 57.57% under the same operational conditions. The total percentage of removing TSS for SVDF is " ~ " 66% obtained from a single device without backwashing system, whilst the percentage of removing TSS for the conventional RAS is 63–68% obtained from two consecutive devices. Hence, SVDF featured with less occupation area and consumed power as well as saving the backwashing water.