Special Issue Survey of Cetaceans in Captive Care

6. Life Support Systems 361contact chamber. Microorganisms, such as bacteria,algae, yeast, and viruses, are killed or inactivatedby the UV radiation produced by the UV lamp thatpenetrates the microorganism’s cell wall and membrane,destroying the inner material. These microorganismsrequire a precise wavelength and durationof irradiation to be destroyed; otherwise, they canresist, repair, and regrow (Mofidi et al., 2002). UVsterilisation is a point-contact process. Efficiencydepends on the time of contact; therefore, the speedof the flow is crucial. UV sterilisation efficiency isimpeded by turbidity; the higher the number of suspendedparticles in the water, the less light penetration(Spotte, 1991). The precise UV dosage will bedetermined by the quality of water and the type ofmicroorganisms targeted. UV dose is recorded as aproduct of irradiance (milliwatts per square centimetre)and time (second), which provides units ofmilliJoules per square centimetre (mJ/cm 2 ) (Mofidiet al., 2002). Low-pressure lamps are preferred asthey have a longer life and are more economical toreplace. Recommended dosage is between 20 and35 mJ/cm 2 (calculated at the end of lamp life) ata wave length of 254 nanometer (nm). UV lightsterilisation is not the most efficient system forlarge volumes (Spotte, 1991); it is also one of theless economical (Boness, 1996); however, it issafer in comparison with other means of sterilisationin terms of potential production of harmfulbyproducts.I recommend that a newly installed systems berun for several days to several weeks before introducinganimals into the pool to ensure that thereare no toxicity concerns, leakage, or loose materialsfrom the LSS.In conclusion, there is not one solution that hasall the advantages. The survey showed that newLSSs tend to be more complex and that a combinationof techniques is the most efficient solution.Nowadays, it is common to see an LSS equippedwith high-pressure sand filters as the basicmechanical installation. This is used in combinationwith either a high dosage of ozone or proteinskimmers, combined with a lower dosage ofozone. This also is associated with activated carbonfilters or denitrification filters on side-streams,sometimes a side-stream treated by UV, and oftena small dosage of chlorine as a residual oxidant inbulk-fluid to prolong oxidation capacity and controlalgal growth. This combination of techniquesallows all of the different and extremely complexreactions occurring in cetacean pool water purificationto be tackled with more subtlety.Water Flow and DrainageFlow mechanics in pools are a delicate and complicatedmatter, and they are difficult to summarise.Figure 6.8. UV unit (Photograph from I. Smit)Water circulation depends mainly on the volume ofwater and the topography and depth of the pool. Ingeneral, water flows into the pool through severalinlet pipes located in the upper section, and sumpslocated at the bottom of the pool collect water tooutlet pipes. Both inlet and outlet pipes shouldbe placed in such a way that they leave no “deadcorner” in the pool. The survey indicated that itis sometimes obvious that such pockets of poorlyagitated water exist when leaves, food debris, anddirt regularly accumulate at the bottom.Water inlet pipes also can be located all aroundthe perimeter of the pool, close to the water surface.This system is found in semi-natural poolswhere pipes can be hidden behind rocks and aredesigned to distribute water evenly.Air entrapment in the water column is acommon problem in a water circulation system.High turbidity levels increase air entrapment assuspended solids bind with air bubbles and preventthem from ascending to the surface and escaping.It is caused by a high water flow rate that producesturbulence in some parts of the circulation system.It does not cause an immediate health threat to theanimals, but it can severely disrupt their echolocationabilities (Fasik, 1991).Water turnover rate depends on various factorssuch as the volume of water to treat or replace,the number of animals, the water temperature, andthe sterilisation system. The survey indicated that