In natural bodies of freshwater, the purification of pathogens from the water column occurs primarily in wetlands. Four processes have been identified in achieving this end, being: aggregation (floc formation) and sedimentation; adsorption on suspended inorganic matter; competitive inhibition and ingestion by beneficial micro-organisms; and the presence of antibiotics and biocides produced by beneficial micro-organisms and plants. Despite the absence of inorganic matter, it is possible to identify and utilize both floc formation and sedimentation and competitive inhibition and ingestion in purifying artificial freshwater aquasystems. It is also likely that antibiotics and biocides produced by algae and higher plants may play a role in purifying artificial systems.

Aggregation of suspended organic matter and pathogens into settleable solids (floc) is primarily due to the presence of mucopolysaccharides in the water column. These have been highly exploited in treating storm runoff water and sewage water. Many commercial preparations of bacterial origin are used to this end. Of interest to aquaculture is the presence of nematodes in the substrate which produce these mucopolysaccharides, as well as those of bacterial origin. Once floc formation has occurred, upflow filtration provides excellent separation of settleable solids via sedimentation for removal from the aquasystem.

Competitive inhibition and ingestion by beneficial micro-organisms is an important function which occurs primarily in the microstructure of the periphyton. Many of the rotifers of natural bodies of freshwater can be present in artificial aquasystems. They require a suitable substrate on which to attach and a steady gentle flow of highly oxygenated water. Many of these sessile rotifers, such as Stentor, Vorticella and Epistylis, may take months or years to develop their potential in a given aquasystem. Of particular interest is the motile rotifer Philodina, which can swim through the water column or crawl along the microstructure to a desirable location. These rotifers possess the ability to process large quantities of organics and bacteria under ideal conditions. They can reproduce and mobilize rapidly when conditions warrant.

They are also capable of anhydrobiosis, thus not killed through desiccation. A suitable substrate microstructure, which supports these rotifers and nematodes, while facilitating the transit of highly oxygenated water will maximize the purification process in filtering artificial aquasystems.

The antibiotic and biocidal effects of both algae and higher plants has yet to be studied, but their presence in the aquasystem, where possible, is desirable for the removal of iron, nitrates and phosphates from the system.

Based on these processes, a phytoremedial device was developed for use in artificial aquasystems. When combined with an upflow refugium, a synthetic wetlands filter was produced. Once biologically activated and planted with a terrestrial plant, excellent control of ammonia, nitrite and nitrate was achieved. Lower turbidity levels were measured compared to the inert control setup.^1,2 Further testing for the control of a pathogenic strain of Aeromonas sobria introduced into the aquasystem proved the synthetic wetlands filter to be highly effective.[3] Additional testing in an aquasystem housing a painted turtle Chrysemys picta for an extended period showed excellent control of total coliforms.

References

1.  A Phytoremedial Device for Koi Ponds. Julius M. Tepper. Proceedings of the IAAAM, 2000.

2.  The Use of an Upflow Refugium and Phytoremedial Device for Water Purification in Clinical Pet Fish Practice. Julius M. Tepper. Proceedings of the IAAAM, 2004.

3.  Testing a Refugium and Phytoremedial Device for the Control of a Pathogenic Strain of Aeromonas sobria. Julius M. Tepper* and Tirath S. Sandhu. Proceedings of the IAAAM, 2005.

4.  Testing a Refugium and Phytoremedial Device for the Control of Total Coliforms in an Aquatic Reptile Habitat. Julius M. Tepper and Tirath S. Sandhu. Proceedings of the IAAAM, 2007. Scandinavica. 56:66;2014.