Northwest Fisheries Science Center

Reduction in energy consumption using the moving bed biofilter

Land-based reuse systems offer many advantages over net pens or flow-through systems. The primary disadvantages of reuse systems are higher energy use, carbon dioxide emissions, and capital costs. One of the most expensive unit processes in reuse systems is nitrification, the bacterial conversion of ammonia to nitrate. Typical nitrification systems involve pumping of the process water up 3-5 meter through a series of closed reactors using plastic beads or sand as the bacteria support media. A relatively new development is the moving bed filter, a system that uses small floating plastic media that are keep in circulation with mechanical mixing or diffused aeration. The integration of moving bed biofilter and circular rearing tanks may significantly reduce the energy consumption and the size of the reuse system.