Our main aquaculture facility is a modern, high intensity, recirculating system. People are often surprised that aquaculture is viable in dry southern Alberta. The secret is that virtually all the water in our facility is used over and over again. Water from the tanks is filtered, treated and returned to the tanks again. The only place where water is lost from the system is the water used to wash the drum filter. The drum filter removes particles bigger than 62 microns (1 micron = 1/1000 mm).

After passing through the drum filter the water goes to a fluidized sand bed (a biological filter) that maintains a culture of bacteria that removes ammonia from the water. Although fish produce ammonia, they are very sensitive to it and the ammonia must be removed from the water. There are two kinds of bacteria in the filter that convert ammonia into nitrate.

The water next passes to a low head oxygenation unit where carbon dioxide is removed and oxygen and ozone are added. We add pure (95%) oxygen to the water. The oxygen is produced by a VPSA (vacuum pressure swing absorption) oxygen generator located just outside the building. This machine separates the oxygen (21%) in the air from the nitrogen (78%) by passing the air through a molecular sieve. The oxygen moves more quickly through the sieve than the nitrogen. The flow of air through the sieve is reversed every few seconds to exhaust the nitrogen. The reason the oxygen is only 95% pure is that argon, an inert gas present in air at about 1%, moves through the sieve at the same rate as oxygen. We use ozone to partially disinfect the water. The ozone is generated from the pure oxygen by passing it through a system of electrical grids that discharge due to a high electrical voltage between them. This is the same principle that produces the ozone that you can smell in the air after an electrical storm.

Once the oxygen and ozone have been added the water passes back into the fish tanks.

A key feature of intensive aquaculture facilities such as this one is continuous and intensive monitoring. Our system is monitored by a large number of sensors that measure such parameters as water temperature, oxygen concentration in the water, pH, ORP (oxidation reduction potential, a measure of the amount of ozone in the water), and water levels in various tanks. All of the monitoring system is connected to a computer that automatically notifies the facility manager if there are any deviations in parameters monitored outside the normal operating range.