Abstract

Life support systems (LSS) maintain quality water for marine mammals held in closed water systems. Typically, three components make up these systems; mechanical filters filled with a filter media which remove solids, biological filters or baffles which remove or help to detoxify chemicals in the water, and disinfecting methods to control or remove pathogens.

Mechanical filters are vessels that hold sand or other filter media. Sand filters operate under pressure and a high flow rate of water and must be backwashed regularly to remove the collected waste and particulate material. Formation of foam on the surface of the pools could indicate the sand filters are not functioning properly. Foam is an indicator of excessive protein that is not properly broken down and removed. Foam fractionators are built into the newer systems to help solve this problem. Sand filters must be checked for channels which allow water to pass through without removing the solids and may cause a protein build-up in the system. Plastic bead media filters run at a lower pressure, require less energy, have lower backwash water loss rates, do not cake or form channels and the media never needs replacement.

Biological filters provide a large surface area on which beneficial bacteria may grow. Media compositions include sand, gravel, plastic beads, or baffles. Sand and bead filters may serve as biological filters if not exposed to disinfectants or oxidizing agents. Beneficial bacteria such as Nitrosomonas and Nitrobacter grow in biological filters and biofiltration occurs when these bacteria actively break down organic compounds. These bacteria are capable of detoxifying nitrogenous waste such as ammonia and nitrites to relatively harmless nitrates.

Common disinfectants include chlorine, and ozone. Chlorine is highly effective at inactivating pathogens. When combined with organic material containing ammonia, byproducts are formed called chloramines which may cause skin or eye irritation. Ozone is used in most modern LSS. Efficiency is based on the time ozone is in contact with the water and the power of the ozone generator. Water in direct contact with animals should be ozone-free as the free radicals may cause cellular damage. Bromine reacts with organic materials and forms brominated disinfection byproducts that may be harmful to animal health.

UV light is used to kill microorganisms and is usually accomplished with mercury lamps. The microorganisms must be directly exposed to the light energy which requires a high side-stream flow of the circulating water to the lamps. UV disinfection may be best used in combination with other disinfection techniques which may decrease the amount of oxidants necessary to maintain the quality of the water.

Coliform Bacteria Testing and Recording

Coliform counts are used to monitor the efficiency of the LSS in the removal of potentially harmful bacteria. Testing must be done weekly at USDA licensed facilities and the most probable number of bacteria not exceed 1000 per 100 ml of water. Records should reflect the actual number of coliforms exceeding 1000, rather than a notation of “>1000.” Coliform counts of zero may indicate over-oxidizing the pool.

* Presenting author