Factors influencing optimal micro-screen drum filter selection for recirculating aquaculture systems

• An optimal method of drum filter selection for aqua-cultural applications.
• A low cost method to establish particle size distribution of suspended solids in a RAS.
• The effect of cake filtration on mechanical filtration efficiency and flow rates through micro-screen filters.

Recirculation aquaculture systems (RAS) are susceptible to contamination due to the accumulation of waste matter including faecal material in the water. It is imperative that contaminant levels are maintained within acceptable limits. The maintenance of good water quality is a pre-requisite to the success of the fish farming operation. Micro-screen drum filters are a popular solution for the removal of suspended solid material and are nominally rated by their screen aperture size measured in microns. Negligence in this area will adversely affect animal growth rates and thus the economic performance of the system. Many variables influence mechanical filter performance, this presents a common issue during equipment selection. For simplicity, vendors have simplified selection criteria for filters to the flow capacity at vendor specified TSS levels, without reference to a specific culture species. This paper outlines a method for micro-screen drum filter selection for site and species specific applications using simple equipment, aiding in the identification of an optimal filtration solution, in terms of cost and filtration performance. Furthermore, the potential of cake filtration for increased filtration mechanical efficiency is also evaluated; this evaluation considers the impact of cake filtration on filter flow rate and mechanical filtration efficiency, for an analysis that is more representative of real world operating conditions. It has been found that the formation of a cake does not significantly increase the mechanical filtration efficiency achieved.