Biomaterials as carriers of denitrification bacteria for water treatment in aquariums


With the booming interest in aquariums as a hobby and, consequently, the introduction of new exotic ornamental fish species, higher water-quality standards are required for those aquariums. Some fish species are unable to propagate or grow in water containing high nitrate levels, and those levels stimulate undesirable algal growth on the aquarium walls. Today, only a limited number of commercial biofiltration systems adapted to nitrate removal from aquariums are available. Moreover, problems are often encountered with those few commercially available filters, and there is therefore a need for denitrifying filters that are easy to operate and instantly and rapidly remove nitrate from aquariums. We designed novel beads which have potential applications in water-purification systems for aquariums. Denitrifying bacteria immobilized in a matrix composed of single or complex biopolymers and other ingredients were employed as reducing agents in the conversion of nitrate to nitrogen gas. These unique beads enable the incorporation of the bacteria at a high concentration and stability. Denitrifying activity was sustained over an extended period of time with limited loss of carrier texture. Pilot studies employing the beads have been successfully carried out in commercial-size aquariums.