Food-based sizing criteria of bead filters with floating media in serial treatment with moving bed bioreactors

Authors: MALONE, RONALD - LSU Agcenter; ALT, DANIEL - LSU Agcenter; Pfeiffer, Tim

Submitted to: Journal of Aquaculture Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/10/2022
Publication Date: 11/11/2022
Citation: Malone, R.F., Alt, D., Pfeiffer, T.J. 2022. Food-based sizing criteria of bead filters with floating media in serial treatment with moving bed bioreactors. Journal of Aquaculture Engineering. 100:1-9. https://doi.org/10.1016/j.aquaeng.2022.102298.
DOI: https://doi.org/10.1016/j.aquaeng.2022.102298

Interpretive Summary: This manuscript addresses the sizing and integration of a floating bead biofilter and a moving bed bioreactor that are integrated in series for utilization in warmwater recirculating aquaculture production systems as part of the water treatment process. Many times previous designs are used to size these two components without consideration for water flow and ammonia removal capabilities of the bead filter. As a result, failure to properly integrate the two components leads to unit performance that fall below the producer's expectation. In response, the authors have amended sizing recommendation to avoid reoccurrence of this short fall. The authors evaluated three cases for proper integration of the two units. Case one is utilizing the bead filter as a solids capture device without the filter limiting the system recirculating flow rate. Case two, the bead filter determines the system recirculating flow rate based on the feed load rate, but the filter's nitrification capacity is not considered. Lastly, in Case three the nitrification capacity of the bead filter is considered and utilized in sizing the moving bed reactor placed in series after the filter. In summary, using a bead filter that is capable of handling high water reuse flow rates and considering the filter's nitrification capacity will aid in the MBR sizing and produce a more cost-effective design free of transport limitations for solids and ammonia removal.

Technical Abstract: The bead filter and moving bed biological reactor (MBBR) are two common technologies used in tandem to remove solids and ammonia from recirculating aquaculture systems. While the sizing of these two technologies is well understood when designed separately, the same sizing guidelines lead to inefficiencies when the two are used together. This is primarily due to the sizing by part design philosophy not considering processes that occur in multiple system components. In response, the authors have reviewed and amended sizing recommendation to avoid unnecessary oversizing. This analysis presents three cases to examine how sizing by parts can lead to system inefficiencies and to lay out a better design approach. Case 1 utilizes the bead filter as a solids capture device, ignoring the impact of the system’s recirculating flow rate and bead filter’s nitrification capacity. Case 2 uses the bead filter’s volume to determine the system’s recirculating flow rate without considering the bead filter’s nitrification capacity. In Case 3 the bead filter’s nitrification capacity is utilized in sizing the moving bed reactor placed in series after the bead filter. In summary, the high-rate floating bead filters (O=2888 m3 day -1 m-3 media) should be utilized to remove solids prior to a moving bed reactor and the nitrification capacity of the floating bead filter should be consideration in the MBBR sizing. This will produce a more cost-effective design and result in a balanced design free of transport limitations.