Improving Single Pass Solids Removal in Bead Bioclarifiers by Optimizing Media Size and Shape

Commercial-scale marine aquaculture has the potential to balance the increasing demand for high-quality seafood products with the limited harvest capacity of our nations oceans. However, water reuse in recirculating aquaculture systems (RAS) is limited by the accumulation of nitrate, which can be toxic to many species, especially marine species. Thus, nitrate removal by denitrification presents a pressing need for the continued expansion of intensive recirculating aquaculture. In the waste treatment industry, denitrification has traditionally been achieved by adding methanol or a similar chemical to act as the necessary carbon source, which requires sophisticated computer monitoring and control systems. This project proposal will continue to investigate the potential for using Polyhydroxyalkanotes (PHAs), a biodegradable biopolymer produced from sugar fermentation, as an alternative carbon source for denitrification in aquaculture systems. Through a series of lab-scale denitrification bioreactor studies, the denitrification capabilities of PHA were quantified at more than 2.0 kg/m3-day using the effluent from a research production tank stocked with tilapia. The problems associated with clogging and short circuiting of the PHA filter bed were addressed by utilizing the PolyGeyser® bead filter technology which promoted a healthy thin biofilm due to its characteristic frequent and gentle backwashing. This Phase II project will cumulate with the development of a commercial PolyGeyser® Denitrification Filter employing PHAs as a simple, low-cost alternative to the relatively complex existing treatment methods. The final goal is to develop commercial systems to complement the exiting line of PolyGeyser® bead filter to provide both nitrification and denitrification in aquaculture systems.